All practice questions

4736 questions

All types4,736 Multiple choice2,413 Multiple select567 Numeric127 Matching858 Ordering771

A 41-year-old woman is evaluated in the emergency department for severe, diffuse abdominal pain that started two days ago. The pain is continuous, non-radiating, and accompanied by persistent nausea, vomiting, and new-onset generalized weakness. One week ago, she was diagnosed with an uncomplicated lower urinary tract infection and began a course of trimethoprim-sulfamethoxazole. Her past medical history is notable for generalized anxiety disorder. On presentation, her temperature is $37.1^{\circ}\text{C}$ ( $98.8^{\circ}\text{F}$ ), blood pressure is $168/102 \text{ mmHg}$ , heart rate is $118/\text{min}$ , and respiratory rate is $18/\text{min}$ . Physical examination reveals a distressed, diaphoretic woman. Her abdomen is diffusely tender to deep palpation, but there is no guarding, rigidity, or rebound tenderness. Neurologic examination demonstrates $4/5$ strength in the proximal upper and lower extremities bilaterally, with diminished deep tendon reflexes. Laboratory studies show a leukocyte count of $8,500/\mu\text{L}$ , hemoglobin of $13.8 \text{ g/dL}$ , and a serum sodium of $128 \text{ mEq/L}$ . Liver function tests and serum lipase are within normal limits. A non-contrast CT scan of the abdomen shows no abnormalities. Urinalysis reveals no red or white blood cells, but the urine appears dark reddish-brown after standing. Which of the following is the most likely diagnosis?

Acute intermittent porphyria

Acute mesenteric ischemia

Guillain-Barré syndrome

Lead toxicity

Functional neurological symptom disorder

Show answer & explanation

Answer: Acute intermittent porphyria

Answer

Acute intermittent porphyria

The correct diagnosis is Acute Intermittent Porphyria (AIP). This patient presents with a classic triad of symptoms for an acute porphyric attack: severe abdominal pain (often without peritoneal signs), autonomic instability (tachycardia, hypertension, diaphoresis), and neuropsychiatric/neuromuscular manifestations (proximal weakness, diminished deep tendon reflexes). The attack in this vignette was precipitated by the administration of trimethoprim-sulfamethoxazole, a classic porphyrinogenic drug that induces cytochrome P450 enzymes. Additional key features confirming the diagnosis include hyponatremia (commonly due to the syndrome of inappropriate antidiuretic hormone secretion, SIADH, associated with AIP) and dark reddish-brown urine, which occurs when excess porphobilinogen oxidizes to porphobilin upon standing in ambient light. Normal abdominal imaging and normal lipase effectively rule out primary gastrointestinal emergencies.

Step-by-Step Solution

Analyze the clinical presentation and medication history.

Identified a triad of severe neuropathic abdominal pain, autonomic hyperactivity (hypertension, tachycardia, diaphoresis), and neuromuscular weakness (proximal deficits, areflexia) precipitated by a sulfonamide antibiotic.

Establishing the core clinical syndrome and potential triggers is the first step in formulating a targeted differential diagnosis.

Evaluate the objective diagnostic data.

Noted normal abdominal CT, normal lipase, and normal hemoglobin, which safely rule out structural GI emergencies and anemia-associated toxicities. Identified significant hyponatremia and dark urine lacking erythrocytes.

Diagnostic data must be synthesized to eliminate high-morbidity structural conditions and highlight subtle metabolic derangements.

Synthesize the findings to isolate the most likely etiology.

Concluded that Acute Intermittent Porphyria uniquely unifies the multi-system findings (GI, neuro, autonomic, renal/electrolytes), whereas other diagnoses fail to account for the entire clinical picture.

A comprehensive differential diagnosis must account for all of the patient's objective, atypical findings without relying on premature closure.

Key Concept

Synthesizing multi-system clinical findings (abdominal pain, neuropathy, autonomic instability, hyponatremia) and medication history to differentiate Acute Intermittent Porphyria from overlapping gastrointestinal and neurological conditions.

Question 2622Question →

Match each patient's clinical presentation with the single most appropriate initial or definitive diagnostic imaging modality to order.

Click a left item, then click its matching right item

Show answer & explanation

Answer

The 18-year-old male with scrotal pain requires color Doppler ultrasonography. The 45-year-old male with flank pain requires noncontrast computed tomography. The 68-year-old man with urinary incontinence and saddle anesthesia requires magnetic resonance imaging. The pregnant female with right lower quadrant pain requires graded compression ultrasonography.

Each clinical scenario requires a specific imaging modality tailored to the most likely diagnosis while minimizing patient harm. Testicular torsion requires Doppler ultrasound to quickly check arterial blood flow. Nephrolithiasis in adults is best visualized on a noncontrast CT scan. Cauda equina syndrome necessitates urgent MRI to visualize the spinal nerves within the bony canal. Pregnant patients with acute abdominal pain require radiation-free modalities like ultrasound as the first step.

Step-by-Step Solution

Analyze the presentation of the 18-year-old male with scrotal pain.

Identify suspected testicular torsion based on acute pain and absent cremasteric reflex.

Testicular torsion causes ischemia and requires emergent evaluation of arterial flow with Doppler ultrasound.

Analyze the presentation of the 45-year-old male with flank pain.

Identify suspected nephrolithiasis.

Noncontrast CT is the gold standard imaging modality for kidney stones in non-pregnant adults.

Analyze the presentation of the 68-year-old male with a history of prostate cancer.

Identify 'red flag' symptoms suggesting cauda equina syndrome.

MRI of the spine is the definitive test required to evaluate spinal cord or nerve root compression.

Analyze the presentation of the 28-year-old pregnant female.

Identify suspected acute appendicitis and note the pregnancy status.

Ultrasound is the safest initial test to evaluate the appendix while avoiding teratogenic radiation risk.

Key Concept

Selection of diagnostic imaging modalities must be tailored to the suspected pathology while accounting for patient-specific contraindications, such as avoiding ionizing radiation during pregnancy.

Estimated Time:2m 0s

Question 2623Question →

A 24-year-old man is brought to the emergency department by paramedics after sustaining a stab wound to the right upper chest during an altercation. On arrival, he is stuporous, diaphoretic, and in severe respiratory distress. His temperature is 36.5°C (97.7°F), blood pressure is 74/40 mmHg, pulse is 142/min, respirations are 36/min, and pulse oximetry shows 84% on a non-rebreather mask. Physical examination reveals a 3-cm laceration in the right second intercostal space at the midclavicular line. The trachea is visibly deviated to the left, and the jugular veins are prominently distended. Auscultation demonstrates completely absent breath sounds over the right hemithorax with hyperresonance to percussion. Which of the following simultaneous initial stabilization steps are indicated immediately? (Select two)

Select all that apply

Perform a right-sided needle or finger thoracostomy

Establish two large-bore peripheral intravenous lines

Perform rapid sequence endotracheal intubation

Obtain a stat portable chest radiograph

Perform a focused assessment with sonography for trauma (FAST)

Show answer & explanation

Answer: Perform a right-sided needle or finger thoracostomy; Establish two large-bore peripheral intravenous lines

Answer

The most appropriate simultaneous initial steps are to perform a right-sided needle or finger thoracostomy and to establish two large-bore peripheral intravenous lines.

This patient presents with classic signs of a tension pneumothorax following penetrating chest trauma, including profound hypotension, severe respiratory distress, unilateral absence of breath sounds, contralateral tracheal deviation, and jugular venous distention. The accumulating air creates severely elevated intrathoracic pressure that compresses the superior and inferior vena cava, drastically reducing venous return and leading to obstructive shock. The correct initial management requires simultaneous, life-saving interventions: immediate mechanical decompression of the pleural space (via needle or finger thoracostomy) to restore venous return and cardiac output, alongside the establishment of large-bore intravenous access to facilitate the volume and blood product resuscitation appropriate for a hemodynamically unstable major trauma patient.

Step-by-Step Solution

Identify the primary pathophysiologic derangement from the clinical signs.

The patient has obstructive shock secondary to a right-sided tension pneumothorax, evidenced by severe hypotension, absent right breath sounds, tracheal deviation, and distended neck veins.

Recognizing the clinical triad of tension pneumothorax is essential because it dictates emergent, empiric intervention without waiting for diagnostic confirmation.

Determine the necessary simultaneous interventions for stabilization.

Immediate pleural decompression and concurrent securement of vascular access.

Pleural decompression relieves the obstructive intrathoracic pressure to restore cardiac output, while large-bore intravenous access ensures readiness for volume and blood resuscitation required in penetrating trauma.

Key Concept

Clinical diagnosis and immediate empiric stabilization of tension pneumothorax in trauma

Estimated Time:1m 15s

Question 2624Question →

An ambulance brings a 58-year-old man to the acute care bay with a chief complaint of unremitting, heavy chest pain radiating to the left jaw that started 45 minutes prior. He appears profoundly weak and is sweating profusely. His medical history includes type 2 diabetes mellitus and hyperlipidemia. Vital signs show a blood pressure of $76/48\text{ mmHg}$ , a heart rate of $115\text{ /min}$ , a respiratory rate of $24\text{ /min}$ , and an oxygen saturation of $95\%$ on ambient air. Physical examination demonstrates distended neck veins while sitting at a $45^{\circ}$ angle. Lung auscultation reveals clear breath sounds in all fields without adventitious sounds. An initial 12-lead electrocardiogram reveals $3\text{ mm}$ ST-segment elevations in leads II, III, and aVF. The patient is lethargic but responds to verbal stimuli. Which of the following is the most appropriate immediate next step in stabilizing this patient?

Rapid infusion of an isotonic crystalloid solution

Administration of sublingual nitroglycerin

Immediate transfer for percutaneous coronary intervention

Performance of right-sided electrocardiography

Procurement of a bedside chest radiograph

Show answer & explanation

Answer: Rapid infusion of an isotonic crystalloid solution

Answer

The correct step is the rapid infusion of an isotonic crystalloid solution.

The clinical triad of hypotension, jugular venous distention, and clear lung fields in the setting of inferior ST-segment elevations (leads II, III, and aVF) is the classic presentation of a right ventricular (RV) myocardial infarction. The ischemic right ventricle loses its contractility and becomes highly dependent on elevated right-sided filling pressures (preload) to push blood through the pulmonary circulation and fill the left ventricle. Because this patient is in severe cardiogenic shock, the absolute priority is to support the RV preload. Rapid intravenous infusion of an isotonic crystalloid solution (such as normal saline) maximizes venous return, improves RV forward flow, and stabilizes the systemic blood pressure. This life-saving stabilization must occur before the patient is transported for definitive reperfusion therapy.

Step-by-Step Solution

Identify the underlying diagnosis from the clinical triad.

Inferior ST-elevation myocardial infarction complicated by right ventricular (RV) involvement, evidenced by hypotension, jugular venous distention, and clear lungs.

Accurate diagnosis dictates the stabilization pathway, as RV infarction management differs significantly from standard left-sided myocardial infarction.

Analyze the hemodynamic state.

The patient is in cardiogenic shock (blood pressure

76/48\text{ mmHg}

) due to right ventricular failure.

The ischemic right ventricle relies almost entirely on venous return (preload) to maintain forward flow and left ventricular filling.

Determine the most urgent stabilization priority.

Administer rapid intravenous fluids.

Before any definitive therapeutic or diagnostic procedures can be performed safely, the patient's preload must be aggressively supported to prevent imminent cardiovascular collapse.

Key Concept

Initial hemodynamic stabilization of right ventricular myocardial infarction requires aggressive volume expansion with isotonic crystalloids.

Estimated Time:1m 30s

Question 2625Question →

Accurate interpretation of pulmonary and chest wall physical examination findings requires an understanding of the underlying changes in intrathoracic acoustics and mechanics. Match each clinical respiratory examination finding with its most characteristic pathophysiologic mechanism.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Egophony reflects enhanced sound transmission through consolidation; fine late-inspiratory crackles indicate the opening of fibrotic alveoli; Hamman sign represents air in the mediastinum; dullness with decreased fremitus suggests a pleural effusion barrier; and hyperresonance with decreased breath sounds points to emphysematous hyperinflation.

Understanding thoracic acoustics is key to diagnosing respiratory pathology. Normal lung tissue is air-filled and dampens sound. When replaced by solid exudate (pneumonia), high-frequency sound transmission improves, producing egophony. Conversely, fluid in the pleural space (effusion) pushes the lung away from the chest wall, creating a barrier that diminishes sound and fremitus. Air trapping (emphysema) creates an over-resonant, quiet acoustic environment. Interstitial fibrosis causes stiff airways to snap open late in inspiration (crackles). Finally, extra-pulmonary air in the mediastinum is churned by the beating heart, creating a systolic crunch (Hamman sign).

Step-by-Step Solution

Evaluate the acoustic properties described in each physical finding.

Identify whether the finding suggests increased fluid/tissue density (consolidation, effusion), increased air (emphysema, pneumomediastinum), or fibrotic changes.

Physical sounds change predictably based on the density of the transmitting medium in the thorax.

Correlate specific acoustic changes to the correct anatomic compartment.

Egophony localizes to the lung parenchyma; Hamman sign to the mediastinum; dullness/decreased fremitus to the pleural space; and hyperresonance to diffusely trapped alveolar air.

Different anatomic compartments produce distinct physical signatures when pathologically altered.

Key Concept

Correlation of pulmonary physical examination findings with their underlying acoustic and pathophysiologic mechanisms.

Question 2626Question →

Match each patient presentation of suspected stable ischemic heart disease with the most appropriate guideline-indicated next step in diagnostic test sequencing.

Click a left item, then click its matching right item

Show answer & explanation

Answer

The normal baseline ECG capable of exercise pairs with exercise electrocardiography. The ST-depressions capable of exercise pairs with exercise stress imaging. The patient with asthma unable to exercise pairs with dobutamine echocardiography. The patient with a left bundle branch block pairs with vasodilator myocardial perfusion imaging.

Appropriate test sequencing in stable ischemic heart disease requires triaging based on exercise capacity, ECG interpretability, and specific pharmacologic contraindications. The correct pairings align physical capacity with exercise stressors, uninterpretable ECGs with imaging, asthma with dobutamine, and LBBB with vasodilators.

Step-by-Step Solution

Assess the patient's physical ability to achieve a target heart rate.

Determines whether an exercise or pharmacologic stress test is required.

Exercise is always the preferred stressor as it provides physiological prognostic data, but cannot be used if the patient has severe mobility limitations.

Evaluate the baseline electrocardiogram for abnormalities.

Identifies left bundle branch block, paced rhythms, pre-excitation, or ST depressions greater than 1 mm.

These baseline abnormalities render standard exercise electrocardiography uninterpretable and mandate the use of concurrent imaging.

Identify specific electrocardiogram patterns that contraindicate increased heart rate during imaging.

Identifies that a left bundle branch block requires a vasodilator rather than an exercise or dobutamine stressor.

Tachycardia in a patient with a left bundle branch block causes false-positive reversible septal defects on imaging studies.

Review medical history for contraindications to specific pharmacologic agents.

Identifies active reactive airway disease (asthma/wheezing) as a strict contraindication to vasodilator agents.

Vasodilators such as adenosine and dipyridamole can trigger life-threatening bronchospasm; dobutamine must be used instead.

Key Concept

The selection of the initial noninvasive diagnostic test for suspected stable ischemic heart disease depends on evaluating the patient's ability to exercise, the interpretability of their baseline electrocardiogram, and the presence of comorbidities that contraindicate specific pharmacologic stress agents.

Question 2627Question →

During morning rounds on hospital day 8, a 72-year-old man is assessed for transition of care. He was initially admitted for altered mental status and diagnosed with Listeria monocytogenes meningitis, for which he received a full course of intravenous ampicillin and gentamicin. He has been afebrile for 48 hours, is hemodynamically stable, and his white blood cell count is normal. His delirium has improved, though he remains oriented only to person and place, lacking insight into his current physical limitations. Prior to admission, the patient lived alone and was independent with his activities of daily living. Currently, he requires moderate assistance with feeding, bathing, and bed-to-chair transfers. Physical therapy evaluates the patient and notes that he fatigues after 45 minutes of exertion and cannot currently tolerate prolonged therapy sessions. His daughter, who is his legally designated healthcare proxy, visits daily but works full-time and cannot provide daytime supervision. The patient states, 'I am perfectly fine, I am going back to my own house today,' and demands to leave immediately. Which of the following is the most appropriate disposition plan for this patient?

Discharge to an inpatient rehabilitation facility with consent from his daughter

Allow the patient to discharge home against medical advice

Transfer to a skilled nursing facility with consent from his daughter

Transfer to a long-term acute care hospital

Discharge home with intermittent home health physical therapy

Show answer & explanation

Answer: Transfer to a skilled nursing facility with consent from his daughter

Answer

The most appropriate disposition is transferring the patient to a skilled nursing facility with consent from his daughter, because he requires 24-hour care and rehabilitation but cannot tolerate the intensive therapy required for an inpatient rehabilitation facility.

This patient requires post-acute rehabilitation due to his decline in functional status (requiring moderate assistance with ADLs) following a severe infection. However, because he fatigues after 45 minutes of exertion, he cannot participate in the required minimum of 3 hours of daily therapy necessary for admission to an inpatient rehabilitation facility (IRF). Therefore, a skilled nursing facility (SNF), which provides rehabilitation at a lower intensity (typically 1-2 hours per day) along with 24-hour nursing care and assistance, is the most appropriate setting. Furthermore, the patient is disoriented to time, lacks insight into his functional deficits, and cannot safely care for himself at home, indicating he lacks decision-making capacity for his discharge planning. Consequently, his daughter (the designated healthcare proxy) has the authority to consent to the SNF transfer on his behalf.

Step-by-Step Solution

Assess the patient's medical stability and continued acute care needs.

The patient is hemodynamically stable and his acute infection has resolved, indicating he is ready for discharge from the acute inpatient setting.

Determining if acute medical needs persist is the foundational first step in transition planning.

Evaluate the patient's physical and functional capacity for rehabilitation.

The patient requires moderate assistance with ADLs and can only tolerate 45 minutes of physical therapy per day.

Disposition to post-acute care depends heavily on the patient's ability to participate in and physically tolerate physical and occupational rehabilitation.

Assess the patient's decision-making capacity regarding discharge.

The patient is disoriented to time, lacks insight into his physical deficits, and cannot make a safe, reasoned decision about his discharge.

Patients lacking decision-making capacity cannot safely refuse care or leave against medical advice; these decisions legally fall to their designated healthcare proxy.

Determine the most appropriate post-acute care setting based on the synthesis of findings.

A skilled nursing facility (SNF) is chosen over an inpatient rehabilitation facility (IRF) or home health.

An SNF provides necessary 24-hour care for his ADL deficits and offers rehabilitation at a manageable intensity, accommodating his low endurance.

Key Concept

Selecting appropriate post-acute care settings requires synthesizing the patient's medical stability, functional assistance needs, physical endurance for therapy, and decision-making capacity.

Question 2628Question →

A 58-year-old male presents to the clinic for routine follow-up. He has a 10-year history of type 2 diabetes mellitus and hypertension. Current medications include glipizide, amlodipine, and a recently initiated angiotensin-receptor blocker (valsartan). He reports feeling generally fatigued but denies any recent illness, nausea, vomiting, or diarrhea. Vital signs are within normal limits.

Laboratory results are as follows:

Serum Chemistry	Result	Reference Range
Sodium	$139$ mEq/L	$136-145$ mEq/L
Potassium	$5.6$ mEq/L	$3.5-5.0$ mEq/L
Chloride	$112$ mEq/L	$98-106$ mEq/L
Bicarbonate	$18$ mEq/L	$22-28$ mEq/L
Blood urea nitrogen	$26$ mg/dL	$8-20$ mg/dL
Creatinine	$1.5$ mg/dL	$0.7-1.3$ mg/dL
Glucose (fasting)	$158$ mg/dL	$70-110$ mg/dL

Urine Studies	Result	Reference Range
pH	$5.5$	$4.5-8.0$
Sodium	$35$ mEq/L	Variable
Potassium	$20$ mEq/L	Variable
Chloride	$30$ mEq/L	Variable

Based on the interpretation of these laboratory findings, which of the following is the most likely mechanism underlying this patient's acid-base disturbance?

Impaired renal ammoniagenesis due to hypoaldosteronism

Defective hydrogen ion secretion in the distal tubule

Excessive gastrointestinal loss of bicarbonate

Accumulation of unmeasured endogenous organic acids

Impaired bicarbonate reabsorption in the proximal tubule

Show answer & explanation

Answer: Impaired renal ammoniagenesis due to hypoaldosteronism

Answer

Impaired renal ammoniagenesis due to hypoaldosteronism

The correct answer accurately describes the pathophysiology of Type 4 Renal Tubular Acidosis (RTA). The patient has a normal anion gap metabolic acidosis (SAG =

139 - (112 + 18) = 9

mEq/L). In this setting, the urine anion gap helps determine the source. A positive urine anion gap (UAG =

(35 + 20) - 30 = +25

mEq/L) indicates impaired renal excretion of ammonium (

NH_4^+

). When combined with hyperkalemia in a patient with diabetes and recent ARB initiation, this confirms Type 4 RTA. Hypoaldosteronism causes potassium retention; the resulting hyperkalemia creates intracellular alkalosis in the proximal tubule, which suppresses glutaminase activity and thereby impairs renal ammoniagenesis.

Step-by-Step Solution

Calculate the serum anion gap (SAG) to characterize the metabolic acidosis.

SAG =

Na^+ - (Cl^- + HCO_3^-)

139 - (112 + 18) = 9

mEq/L.

A normal SAG (typically

8-12

mEq/L) confirms a non-anion gap metabolic acidosis (NAGMA), narrowing the differential to renal tubular acidoses (RTAs) or gastrointestinal bicarbonate losses.

Calculate the urine anion gap (UAG) to distinguish between renal and extrarenal causes of NAGMA.

UAG =

(Na^+ + K^+) - Cl^-

(35 + 20) - 30 = +25

mEq/L.

A positive UAG indicates a failure of the kidneys to excrete adequate amounts of unmeasured

NH_4^+

(ammonium), pointing to a renal defect (RTA) rather than gastrointestinal bicarbonate wasting.

Evaluate the serum potassium level and contextual clinical clues.

Potassium is elevated at

5.6

mEq/L. The patient has diabetes and is taking an angiotensin-receptor blocker (valsartan).

The combination of NAGMA, a positive UAG, and hyperkalemia defines Type 4 RTA. The hyperkalemia, caused by hypoaldosteronism (due to diabetic nephropathy and valsartan use), impairs proximal tubular ammoniagenesis, leading to the positive UAG and acidosis.

Key Concept

Type 4 Renal Tubular Acidosis presents as a normal anion gap metabolic acidosis with hyperkalemia and a positive urine anion gap, commonly seen in patients with diabetic nephropathy or those taking medications that interfere with the renin-angiotensin-aldosterone system.

Question 2629Question →

A 48-year-old woman presents to the emergency department with severe, constant right upper quadrant abdominal pain that radiates to her right scapula, accompanied by fever and nausea. The pain began $12\text{ hours}$ ago after she consumed a high-fat meal. Her temperature is $38.4^\circ\text{C}$ ( $101.1^\circ\text{F}$ ), blood pressure is $135/85\text{ mmHg}$ , and heart rate is $105\text{/min}$ . Physical examination reveals marked tenderness with inspiratory arrest upon deep palpation of the right upper quadrant.

Arrange the following diagnostic imaging modalities in the appropriate step-wise sequence for evaluating and managing this patient's presentation, from the initial diagnostic test to the evaluation of potential late complications.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence for evaluating suspected acute cholecystitis is right upper quadrant transabdominal ultrasonography first, followed by a HIDA scan if the ultrasound is indeterminate, and finally a CT scan of the abdomen to evaluate for complications if clinical deterioration occurs.

The standard diagnostic algorithm for acute cholecystitis begins with right upper quadrant transabdominal ultrasonography. Ultrasound is rapid, lacks ionizing radiation, and is highly sensitive for detecting gallstones, which are the primary etiology. If the ultrasound findings are equivocal (e.g., gallstones are present but wall thickening or sonographic Murphy sign is absent), a hepatobiliary iminodiacetic acid (HIDA) scan is ordered next. The HIDA scan assesses cystic duct patency, and failure of the gallbladder to visualize confirms the diagnosis of acute cholecystitis. Finally, if a patient with acute cholecystitis subsequently exhibits clinical deterioration, severe sepsis, or generalized peritonitis, a contrast-enhanced CT of the abdomen is then indicated to evaluate for complications such as gallbladder perforation, gangrenous cholecystitis, or pericholecystic abscess formation.

Step-by-Step Solution

Analyze the clinical presentation

The patient's postprandial right upper quadrant pain, fever, and positive Murphy sign strongly suggest acute cholecystitis.

Identifying the suspected primary diagnosis dictates the initiation of a specific imaging algorithm.

Determine the optimal first-line imaging test

Right upper quadrant transabdominal ultrasonography is placed first in the sequence.

Ultrasound is the most sensitive initial test for gallstones and local gallbladder inflammation, making it the universal first step.

Identify the appropriate confirmatory test for an equivocal initial result

A HIDA (cholescintigraphy) scan is placed second.

If the ultrasound cannot definitively confirm or rule out acute cholecystitis, a HIDA scan is utilized to demonstrate cystic duct obstruction (non-visualization of the gallbladder).

Select the imaging modality for suspected downstream complications

Contrast-enhanced CT of the abdomen is placed third.

CT is not utilized for initial diagnosis but is highly effective for identifying severe downstream complications like perforation or abscess if the patient clinically deteriorates.

Key Concept

Step-wise diagnostic imaging algorithm for acute cholecystitis

Alternative Method

Point-of-care ultrasonography (POCUS) performed immediately by the attending physician can rapidly identify gallstones and a sonographic Murphy sign at the bedside, accelerating the decision to consult general surgery before a formal, comprehensive radiology-performed ultrasound is completed.

Estimated Time:1m 0s

Question 2630Question →

An adult male in his early sixties presents to an urgent care clinic with a three-day history of severe, diffuse muscle pain, profound generalized weakness, and passing tea-colored urine. His established medical background includes ischemic heart disease, hypercholesterolemia, and a recently identified supraventricular arrhythmia. His longstanding daily medication regimen consists of simvastatin, low-dose aspirin, and previously, metoprolol. His baseline laboratory records show mild, asymptomatic elevations in serum transaminases, and he is up to date on all age-appropriate cancer screenings. Eighteen days prior to this visit, a consulting specialist transitioned him from metoprolol to diltiazem for optimized chronotropic control. During the clinical interview, the patient also reports initiating a light treadmill walking routine last week. Physical examination reveals marked, diffuse tenderness across major muscle groups of the proximal extremities. During the targeted medical history evaluation for this patient's acute presentation, identifying which of the following details is most crucial for establishing the immediate etiology of his symptoms?

The addition of a medication known to inhibit the cytochrome P450 3A4 isoenzyme

The onset of myalgias following the initiation of a novel aerobic exercise regimen

The patient's ongoing adherence to a longstanding daily lipophilic statin prescription

The patient's historical baseline of mild, asymptomatic transaminase elevations

The status of the patient's age-appropriate malignancy screening history

Show answer & explanation

Answer: The addition of a medication known to inhibit the cytochrome P450 3A4 isoenzyme

Answer

The addition of a medication known to inhibit the cytochrome P450 3A4 isoenzyme

The patient is presenting with classic signs of acute rhabdomyolysis, evidenced by severe diffuse muscle pain, weakness, and tea-colored urine (myoglobinuria). When evaluating this patient's medical history, the most critical finding is the recent addition of diltiazem to a regimen that already includes simvastatin. Simvastatin is extensively metabolized by the cytochrome P450 3A4 (CYP3A4) isoenzyme in the liver. Diltiazem (a non-dihydropyridine calcium channel blocker) is a well-known moderate inhibitor of CYP3A4. The concurrent use of these medications profoundly decreases the hepatic clearance of simvastatin, causing serum levels to rise to toxic thresholds and precipitating severe myopathy and rhabdomyolysis. Promptly identifying this historical detail dictates both the correct diagnosis and the immediate cessation of the offending agents.

Step-by-Step Solution

Analyze the patient's clinical presentation.

The combination of severe myalgias, profound weakness, and tea-colored urine strongly indicates acute rhabdomyolysis.

Recognizing the syndrome dictates the need to immediately identify the precipitating toxicologic or physical trigger.

Evaluate the timeline of the patient's medical and medication history.

The patient has been on stable doses of simvastatin, but diltiazem was added 18 days ago, shortly before the onset of symptoms.

Identifying recent changes in the patient's exposure history is crucial for uncovering iatrogenic causes of acute decompensation.

Assess for pharmacokinetic interactions among the active medications.

Diltiazem inhibits the CYP3A4 enzyme, which is required to metabolize simvastatin, leading to a sudden, toxic accumulation of the statin.

Understanding drug-drug interactions is a fundamental component of evaluating a patient's medication history to establish a definitive diagnosis.

Key Concept

Pharmacokinetic drug-drug interactions (specifically CYP3A4 inhibition by diltiazem) as a precipitant for statin-induced rhabdomyolysis, identified through meticulous medication history evaluation.

Question 2631Question →

A 24-year-old nulligravid woman comes to the clinic with a 3-day history of lower abdominal pain, new-onset abnormal vaginal discharge, and pain during sexual intercourse. Her temperature is 38.0°C (100.4°F), blood pressure is 110/70 mmHg, and pulse is 88/min. Pelvic examination reveals a friable cervix with mucopurulent discharge, pronounced cervical motion tenderness, and bilateral adnexal fullness with tenderness. A urine pregnancy test is negative. She is able to tolerate oral intake and appears well overall. Which of the following antimicrobial therapies should be included in this patient's initial empiric outpatient regimen? (Select all that apply)

Select all that apply

Intramuscular ceftriaxone

Oral doxycycline

Oral metronidazole

Oral azithromycin

Intravenous cefoxitin

Show answer & explanation

Answer: Intramuscular ceftriaxone; Oral doxycycline; Oral metronidazole

Answer

The correct empiric outpatient regimen for pelvic inflammatory disease includes intramuscular ceftriaxone, oral doxycycline, and oral metronidazole.

The patient presents with classic signs of mild-to-moderate pelvic inflammatory disease (PID). Current guidelines recommend comprehensive coverage for the most likely pathogens. The standard outpatient regimen consists of a single dose of intramuscular ceftriaxone to cover Neisseria gonorrhoeae, combined with a 14-day course of oral doxycycline to cover Chlamydia trachomatis, and a 14-day course of oral metronidazole to clear anaerobic organisms and Trichomonas vaginalis.

Step-by-Step Solution

Diagnose the clinical condition based on the presentation.

The patient has pelvic inflammatory disease (PID), characterized by lower abdominal pain, cervical motion tenderness, and adnexal tenderness.

Identifying the clinical syndrome is the first step in determining the appropriate empiric treatment guidelines.

Determine the appropriate clinical setting for treatment.

The patient is tolerating oral intake, is hemodynamically stable, has no signs of a tubo-ovarian abscess, and is not pregnant, making her a candidate for outpatient management.

The setting (inpatient vs. outpatient) dictates whether intravenous or oral/intramuscular regimens should be utilized.

Select the guideline-concordant antimicrobial coverage for outpatient PID.

Select a regimen that covers N. gonorrhoeae, C. trachomatis, and anaerobes: Ceftriaxone IM, Doxycycline PO, and Metronidazole PO.

Empiric therapy must cover the most common pathogens associated with PID while accounting for current local and national resistance patterns.

Key Concept

Empiric Outpatient Treatment of Pelvic Inflammatory Disease (PID)

Question 2632Question →

Evaluate the following distinct patient presentations involving peripheral nerve and spinal cord dysfunction. Match each clinical scenario to its most likely underlying pathophysiologic etiology.

Click a left item, then click its matching right item

Show answer & explanation

Answer

The correct pairings match each patient's specific constellation of symptoms, chronological progression, and past medical history to the distinct pathophysiologic mechanism of their neurological dysfunction.

Correct matching requires synthesizing the chronological onset, symmetry, accompanying physical exam findings, and relevant past medical history to arrive at the precise pathophysiologic diagnosis for each patient's presentation.

Step-by-Step Solution

Analyze the first patient's presentation of symmetric distal sensory symptoms, absent ankle reflexes, and orthostatic hypotension with long-standing diabetes.

Identified as diabetic sensorimotor polyneuropathy.

These findings are classic for length-dependent axonal degeneration with autonomic involvement.

Evaluate the second patient's acute, symmetric ascending weakness and areflexia following a gastrointestinal infection.

Identified as Guillain-Barré syndrome.

This is characteristic of an immune-mediated acute inflammatory demyelinating polyradiculoneuropathy triggered by an antecedent infection.

Assess the third patient's sensory ataxia and upper motor neuron signs (hyperreflexia) following gastric bypass surgery.

Identified as subacute combined degeneration due to vitamin B12 deficiency.

Vitamin B12 deficiency causes demyelination of the dorsal columns (producing sensory ataxia) and lateral corticospinal tracts (producing hyperreflexia).

Examine the fourth patient's mononeuritis multiplex and palpable purpura with a history of hepatitis C.

Identified as cryoglobulinemic vasculitis.

Hepatitis C is highly associated with cryoglobulinemia, leading to immune complex deposition and vasa nervorum inflammation.

Key Concept

Formulating a differential diagnosis for peripheral neuropathies requires integrating the temporal course (acute vs. chronic), symmetry (symmetric vs. mononeuritis multiplex), presence of upper vs. lower motor neuron signs, and associated systemic findings (e.g., purpura, diabetes, malabsorption).

Question 2633Question →

Roommates of a $20$ -year-old male college student rush him to the triage desk due to a rapidly progressive headache, high fever, and extreme lethargy over the past $12$ hours. His past medical history is notable only for allergic rhinitis, and he takes no daily medications. Triage vital signs demonstrate a temperature of $39.5^\circ\text{C}$ ( $103.1^\circ\text{F}$ ), blood pressure of $82/50\text{ mmHg}$ , heart rate of $132\text{/min}$ , and respiratory rate of $24\text{/min}$ . Pulse oximetry is $95\%$ on ambient air. The clinical examination reveals a somnolent patient who localizes to painful stimuli but provides nonsensical answers to questions. Nuchal rigidity is prominent, and multiple non-blanching purpuric lesions are visible on the lower extremities. Arrange the following acute management steps in the most appropriate chronological sequence.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence prioritizes hemodynamic stabilization and early empiric treatment before diagnostic imaging and definitive procedures: 1) Establish IV access, give fluids and draw cultures, 2) Administer dexamethasone and antibiotics, 3) Obtain a CT scan of the head, 4) Perform a lumbar puncture, 5) Transfer to the intensive care unit.

The fundamental principle of acute patient management is prioritizing physiological stabilization over definitive diagnosis. In a patient presenting with suspected bacterial meningitis and septic shock, establishing intravenous access for aggressive fluid resuscitation and drawing blood cultures is the immediate first step. Once cultures are drawn, empiric broad-spectrum antibiotics and dexamethasone must be administered without delay; it is a critical error to withhold antibiotics while waiting for diagnostic testing. Because the patient presents with altered mental status, there is a risk of fatal brain herniation if a lumbar puncture is performed blindly; therefore, a non-contrast head CT must precede the lumbar puncture. After the CT confirms it is safe, the lumbar puncture is performed to isolate the pathogen. Finally, given the severity of the illness, the patient is triaged to the intensive care unit.

Step-by-Step Solution

Recognize the presence of septic shock and establish access.

Intravenous fluids are initiated and blood cultures are drawn.

Hypotension and tachycardia require immediate circulatory support, which supersedes diagnostic imaging. Cultures must be drawn before antibiotics alter the yield.

Prioritize empiric medical therapy.

Dexamethasone and broad-spectrum antibiotics are administered.

In suspected bacterial meningitis with shock, delaying antibiotics for imaging or definitive testing is strictly contraindicated and drastically increases mortality.

Evaluate the safety of diagnostic procedures.

A head CT scan is ordered and reviewed.

Altered mental status is a clinical red flag for potentially elevated intracranial pressure, necessitating a CT scan prior to a lumbar puncture.

Obtain definitive diagnostic samples.

A lumbar puncture is performed.

Once mass effect is ruled out by the CT scan, cerebrospinal fluid analysis can safely identify the specific pathogen.

Determine the appropriate disposition.

The patient is admitted to the intensive care unit.

Ongoing management of septic shock and meningococcemia requires high-acuity continuous monitoring.

Key Concept

In patients with suspected bacterial meningitis complicated by septic shock or altered mental status, hemodynamic stabilization and empiric antibiotics must precede diagnostic imaging and lumbar puncture.

Question 2634Question →

A 34-year-old woman is brought to the emergency department by ambulance. Her husband reports she suddenly fell to the floor and began having full-body convulsions 15 minutes ago. The convulsions have been continuous without any periods of recovery. She has no known past medical history. Upon arrival, her blood pressure is 142/88 mmHg, pulse is 118/min, and oxygen saturation is 94% on a non-rebreather mask. She is unresponsive, diaphoretic, and exhibiting continuous generalized tonic-clonic movements. Point-of-care blood glucose is 98 mg/dL. Two large-bore peripheral intravenous lines are rapidly established. Arrange the following pharmacologic interventions in the correct sequential order for the escalating management of this patient's condition, starting from the initial recommended therapy to treatments for refractory cases.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence for managing status epilepticus is to start with intravenous lorazepam, followed by intravenous fosphenytoin, then intravenous propofol continuous infusion, and finally intravenous pentobarbital continuous infusion for super-refractory cases.

The management of status epilepticus follows a strict time-dependent protocol. Phase 1 (0-5 minutes) requires a fast-acting benzodiazepine like lorazepam to immediately halt the seizure. Phase 2 (20-40 minutes) involves loading a longer-acting antiepileptic drug like fosphenytoin to maintain seizure suppression. Phase 3 (40-60 minutes) addresses refractory status epilepticus with continuous anesthetic infusions such as propofol, which necessitates securing the airway. Finally, if seizures remain uncontrolled (super-refractory), severe interventions like a continuous pentobarbital infusion are utilized to induce a barbiturate coma.

Step-by-Step Solution

Identify the clinical presentation and duration.

The patient is experiencing generalized tonic-clonic status epilepticus (continuous seizure activity >5 minutes).

Recognizing status epilepticus is critical because it is a neurologic emergency requiring immediate, protocolized pharmacologic escalation to prevent irreversible brain injury.

Determine the Phase 1 (initial) pharmacologic intervention.

Select intravenous lorazepam.

Intravenous benzodiazepines are the first-line agents because they rapidly cross the blood-brain barrier to enhance GABAergic inhibition and abort acute seizure activity.

Determine the Phase 2 (second-line) pharmacologic intervention.

Select intravenous fosphenytoin.

Once a benzodiazepine is given, a longer-acting non-benzodiazepine antiepileptic drug must be loaded to prevent seizure recurrence, as benzodiazepines redistribute rapidly out of the central nervous system.

Determine the Phase 3 (refractory) pharmacologic intervention.

Select intravenous propofol continuous infusion.

If clinical or electrographic seizures persist after Phase 1 and 2 therapies, the patient has refractory status epilepticus. This requires intubation and mechanical ventilation to facilitate continuous infusions of general anesthetics.

Determine the final (super-refractory) pharmacologic intervention.

Select intravenous pentobarbital continuous infusion.

For seizures that continue despite adequate anesthetic infusions for 24 hours (super-refractory status epilepticus), deeply suppressive barbiturate coma is the therapy of last resort.

Key Concept

The protocolized, sequential pharmacologic escalation in the management of status epilepticus.

Question 2635Question →

A 54-year-old man presents to the clinic to discuss his medication regimen. He was diagnosed with active pulmonary tuberculosis earlier today and is scheduled to begin a standard empiric regimen of isoniazid, rifampin, pyrazinamide, and ethambutol. His past medical history is significant for a mechanical mitral valve replacement performed four years ago, for which he takes warfarin. His daily medications also include low-dose aspirin and metoprolol. His vital signs are within normal limits. Physical examination reveals a crisp mechanical click on cardiac auscultation and bronchial breath sounds in the right upper lung field. His international normalized ratio (INR) has been consistently stable at 3.0 for the past year, and today's INR is 2.9. Which of the following is the most appropriate next step in management regarding this patient's pharmacotherapy?

Anticipate the need to increase the warfarin dosage and monitor the international normalized ratio frequently

Anticipate the need to decrease the warfarin dosage to mitigate the risk of severe bleeding

Transition from warfarin to a direct oral anticoagulant to avoid metabolic interactions

Withhold rifampin from the antitubercular regimen to prevent uncontrollable fluctuations in coagulation

Maintain the current warfarin dosage and monitor the activated partial thromboplastin time (aPTT)

Show answer & explanation

Answer: Anticipate the need to increase the warfarin dosage and monitor the international normalized ratio frequently

Answer

Anticipate the need to increase the warfarin dosage and monitor the international normalized ratio frequently

The correct response anticipates the pharmacokinetic effects of rifampin on warfarin metabolism. Rifampin is a potent inducer of hepatic cytochrome P450 enzymes, primarily CYP2C9 and CYP3A4, which are responsible for metabolizing warfarin. Induction of these enzymes drastically accelerates the clearance of warfarin from the bloodstream. In a patient relying on warfarin to prevent thrombosis of a mechanical mitral valve, this accelerated clearance will rapidly lead to a subtherapeutic international normalized ratio (INR), exposing the patient to a critically high risk of valve thrombosis and systemic thromboembolism. Therefore, the most appropriate clinical intervention is to proactively monitor the INR on a frequent basis and anticipate the need to significantly increase the warfarin dosage to maintain the therapeutic target of 2.5 to 3.5.

Step-by-Step Solution

Identify the critical drug-drug interaction introduced by the new medication regimen.

The new tuberculosis regimen includes rifampin, which interacts significantly with the patient's chronic warfarin therapy.

Recognizing polypharmacy interactions is essential to prevent iatrogenic harm, particularly with narrow therapeutic index drugs like warfarin.

Determine the pharmacokinetic mechanism of the interaction.

Rifampin is a potent inducer of hepatic cytochrome P450 enzymes, specifically CYP2C9 and CYP3A4, which are responsible for the metabolism of warfarin.

Understanding whether an agent is an inducer or an inhibitor determines the direction of the dose adjustment required.

Predict the physiological outcome of the enzyme induction on the patient's coagulation status.

Increased CYP450 activity accelerates the clearance of warfarin, leading to a subtherapeutic international normalized ratio (INR) and a higher risk of mechanical valve thrombosis.

Clinical decision-making must preemptively address anticipated changes in drug efficacy before adverse events occur.

Select the appropriate pharmacologic intervention based on the predicted outcome and patient history.

The physician must anticipate the need to increase the warfarin dosage and monitor the INR closely, as alternative anticoagulants like DOACs are contraindicated for mechanical valves.

Standard of care requires vigilant monitoring and proactive dose titration when a known potent CYP inducer is initiated in a warfarin-dependent patient.

Key Concept

Pharmacokinetic drug interactions involving potent cytochrome P450 enzyme inducers (e.g., rifampin) and narrow therapeutic index substrates (e.g., warfarin) require proactive dose escalation and frequent monitoring to prevent therapeutic failure.

Estimated Time:1m 30s

Question 2636Question →

A $28$ -year-old woman, gravida 1 para 0, at $22$ weeks gestation presents to the emergency department with a $12$ -hour history of progressively worsening right-sided abdominal pain, accompanied by nausea and two episodes of non-bloody emesis. Her temperature is $38.2^\circ\text{C}$ , blood pressure is $110/70$ mmHg, and heart rate is $105$ /min. Physical examination reveals focal tenderness to palpation in the right mid-to-lower quadrant with mild voluntary guarding, but no rebound tenderness. Laboratory studies demonstrate a leukocyte count of $16,500/\text{mm}^3$ with a left shift. The patient requires emergent diagnostic evaluation for suspected acute appendicitis.

Arrange the following diagnostic modalities and confirmatory protocols in the correct sequential order for evaluating this patient, proceeding from the initial test of choice to subsequent options if the preceding tests are non-diagnostic, unavailable, or equivocal.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct evaluation sequence for suspected acute appendicitis in pregnancy begins with graded-compression ultrasonography, followed by non-contrast MRI if the ultrasound is non-diagnostic. If MRI is unavailable or inconclusive, a CT scan is performed. Finally, if all imaging fails and clinical suspicion remains high, diagnostic laparoscopy is utilized as the definitive step.

The established standard of care for evaluating suspected appendicitis in a pregnant patient is a strict stepwise progression. Initial evaluation must begin with right lower quadrant graded-compression ultrasonography due to its complete lack of ionizing radiation and ease of access. Because the gravid uterus often displaces the cecum and appendix, ultrasound is frequently non-diagnostic. In such cases, the next appropriate step is a non-contrast MRI, which offers high sensitivity and specificity without radiation exposure. If MRI is contraindicated, unavailable, or non-diagnostic, a CT scan of the abdomen and pelvis is ordered; the risk of untreated appendiceal rupture drastically outweighs the radiation risk to the fetus. Finally, if imaging protocols are exhausted and the clinical picture remains highly suspicious, diagnostic laparoscopy serves as the definitive confirmatory and therapeutic procedure.

Step-by-Step Solution

Select the initial imaging modality with the highest safety profile for the fetus.

Graded-compression ultrasonography is chosen as the first-line test.

Ultrasonography avoids ionizing radiation and is widely available, making it the standard initial diagnostic step, despite anatomical challenges posed by the gravid uterus.

Determine the best second-line imaging modality if the initial test is non-diagnostic.

Non-contrast MRI is sequenced as the second-line test.

MRI provides superior soft-tissue visualization to locate a displaced appendix without exposing the fetus to radiation, heavily outperforming ultrasound in diagnostic accuracy for pregnant patients.

Identify the fallback imaging modality if MRI cannot be performed or is inconclusive.

Computed tomography (CT) is sequenced as the third-line test.

Although CT exposes the fetus to ionizing radiation, the risk of a missed appendiceal rupture causing fetal loss is statistically higher than the radiation risk from a single scan.

Establish the definitive confirmatory step when non-invasive tests are exhausted.

Diagnostic laparoscopy is sequenced as the final option.

When cross-sectional imaging cannot rule out appendicitis and clinical suspicion remains elevated, surgical intervention is required to confirm the diagnosis and prevent life-threatening complications.

Key Concept

Sequencing diagnostic imaging for acute appendicitis in pregnancy strictly prioritizes minimizing fetal radiation while ensuring diagnostic accuracy.

Alternative Method

In rural or low-resource settings where MRI is completely unavailable, the clinical pathway effectively bypasses MRI, making the sequence Ultrasound directly followed by CT scan if clinical suspicion remains high and ultrasound is indeterminate.

Estimated Time:1m 30s

Question 2637Question →

A 52-year-old man is evaluated for treatment-resistant hypertension. His current blood pressure is $168/95\text{ mmHg}$ despite adherence to amlodipine, lisinopril, and chlorthalidone. Laboratory studies obtained two weeks ago showed:

- Serum sodium: $144\text{ mEq/L}$
- Serum potassium: $2.9\text{ mEq/L}$
- Plasma aldosterone concentration: $32\text{ ng/dL}$ (Normal: $3-16\text{ ng/dL}$ )
- Plasma renin activity: $0.2\text{ ng/mL/h}$ (Normal: $0.6-4.3\text{ ng/mL/h}$ )

A dedicated adrenal protocol computed tomography (CT) scan demonstrates a $1.8\text{-cm}$ lipid-rich nodule in the right adrenal gland. The left adrenal gland appears normal.

To guide further management, an adrenal venous sampling (AVS) procedure is performed with continuous cosyntropin (ACTH) infusion. The laboratory results from the procedure are shown in the table below:

Cannulation Site	Aldosterone ( $\text{ng/dL}$ )	Cortisol ( $\mu\text{g/dL}$ )
Peripheral vein (IVC)	$30$	$15$
Right adrenal vein	$600$	$150$
Left adrenal vein	$1200$	$300$

Based on these laboratory findings, which of the following is the most accurate interpretation of this patient's underlying condition?

Bilateral idiopathic adrenal hyperplasia

Right-sided aldosterone-producing adenoma

Left-sided aldosterone-producing adenoma

Unsuccessful right adrenal vein cannulation

Adrenocorticotropic hormone-dependent hypercortisolism

Show answer & explanation

Answer: Bilateral idiopathic adrenal hyperplasia

Answer

Bilateral idiopathic adrenal hyperplasia

The correct diagnosis is bilateral idiopathic adrenal hyperplasia. Adrenal venous sampling (AVS) interpretation requires a stepwise calculation. First, successful cannulation is verified by dividing adrenal cortisol by peripheral (IVC) cortisol (Selectivity Index); a ratio

>5

with cosyntropin confirms success. Here, the right SI is

10

(

150/15

) and the left is

20

(

300/15

). Second, because absolute hormone levels are subject to dilutional variance based on exact catheter position and blood flow, aldosterone must be normalized to cortisol. The aldosterone-to-cortisol (A/C) ratio is

4

on the right (

600/150

) and

4

on the left (

1200/300

). Finally, the lateralization index is calculated by dividing the highest A/C ratio by the lowest A/C ratio (

4/4 = 1

). A lateralization index

<3

indicates symmetric, bilateral aldosterone hypersecretion. The right-sided nodule seen on imaging is therefore a non-functioning incidentaloma.

Step-by-Step Solution

Calculate the selectivity index (SI) for both adrenal veins to verify proper catheter placement.

Right SI = 150/15 = 10; Left SI = 300/15 = 20.

An SI > 5 (during cosyntropin infusion) confirms the catheter is properly placed in the adrenal vein, avoiding dilution from peripheral venous blood.

Calculate the aldosterone-to-cortisol (A/C) ratio for each adrenal vein.

Right A/C = 600/150 = 4; Left A/C = 1200/300 = 4.

Absolute aldosterone levels are misleading due to varying blood flow and dilution; cortisol acts as an internal standard to normalize the values.

Calculate the lateralization index (LI) to determine if secretion is unilateral or bilateral.

LI = Dominant A/C divided by Non-dominant A/C = 4 / 4 = 1.

An LI > 4 indicates unilateral autonomous hypersecretion (adenoma), whereas an LI < 3 indicates bilateral symmetric hypersecretion (hyperplasia).

Correlate the biochemical AVS diagnosis with the imaging findings.

The patient has bilateral adrenal hyperplasia, and the right-sided adrenal nodule is a non-functioning incidentaloma.

CT imaging is notoriously misleading in primary aldosteronism due to the high prevalence of non-functioning adrenal incidentalomas; AVS provides the definitive functional diagnosis.

Key Concept

Interpretation of adrenal venous sampling (AVS) using cortisol-normalized aldosterone ratios to distinguish between unilateral adenoma and bilateral hyperplasia.

Question 2638Question →

A 42-year-old woman presents to the clinic to establish care. She reports an 18-kg (39.7-lb) weight gain over the past year, accompanied by irregular menses, new-onset facial hair, and difficulty rising from a seated position. Her medical history is significant for generalized anxiety disorder. Her only medication is an estrogen-containing oral contraceptive pill. Blood pressure is 162/98 mmHg, and BMI is 34 kg/m². Physical examination reveals a plethoric face, prominent supraclavicular fat pads, broad violaceous striae on the abdomen, and 4/5 strength in the proximal lower extremities. The physician suspects hypercortisolism. An overnight 1-mg dexamethasone suppression test yields a morning serum cortisol of 14.2 µg/dL (normal: < 1.8 µg/dL). A 24-hour urine free cortisol is 185 µg/24h (normal: 10-50 µg/24h). Which of the following is the most appropriate next step in laboratory evaluation?

Measurement of plasma renin activity and serum aldosterone

High-dose (8-mg) dexamethasone suppression test

Measurement of plasma adrenocorticotropic hormone (ACTH) level

Magnetic resonance imaging (MRI) of the pituitary gland

Discontinue the oral contraceptive pill and repeat the overnight dexamethasone suppression test

Show answer & explanation

Answer: Measurement of plasma adrenocorticotropic hormone (ACTH) level

Answer

The correct next step is the measurement of plasma adrenocorticotropic hormone (ACTH) level.

Once endogenous hypercortisolism is definitively confirmed by at least two abnormal first-line tests (in this case, an abnormal 1-mg dexamethasone suppression test and an elevated 24-hour urine free cortisol), the next mandatory step in the diagnostic algorithm is to determine whether the hypercortisolism is ACTH-dependent or ACTH-independent. This is accomplished by measuring the plasma ACTH level. A suppressed ACTH (< 5 pg/mL) indicates an ACTH-independent adrenal source (prompting an adrenal CT), whereas a normal or high ACTH indicates an ACTH-dependent source (prompting a pituitary MRI or high-dose dexamethasone suppression testing to differentiate pituitary from ectopic sources).

Step-by-Step Solution

Identify the clinical syndrome from the patient's presentation.

The patient has signs and symptoms highly consistent with Cushing's syndrome (weight gain, proximal weakness, striae, hypertension, hirsutism).

Recognizing the clinical phenotype directs the appropriate diagnostic pathway.

Interpret the initial laboratory screening tests.

Both the 1-mg overnight dexamethasone suppression test and the 24-hour urine free cortisol are unequivocally abnormal.

Endogenous hypercortisolism must be confirmed with at least two first-line biochemical tests before proceeding to determine the etiology.

Determine the algorithmic next best step for confirmed hypercortisolism.

The necessary step is to differentiate ACTH-dependent from ACTH-independent causes.

This differentiation dictates whether the source is adrenal (ACTH-independent) or central/ectopic (ACTH-dependent), fundamentally changing subsequent imaging and management.

Select the appropriate laboratory test to achieve this differentiation.

Measurement of plasma ACTH level is chosen.

A low ACTH level (< 5 pg/mL) indicates an adrenal source, while a normal or elevated ACTH level indicates a pituitary or ectopic source.

Key Concept

The diagnostic algorithm for Cushing's syndrome requires confirming hypercortisolism with at least two first-line screening tests, followed immediately by measuring plasma ACTH to determine ACTH dependence before any imaging or high-dose suppression testing.

Question 2639Question →

A 62-year-old woman presents to the emergency department with a 24-hour history of severe, intermittent right upper quadrant abdominal pain that radiates to her right scapula. She also reports several episodes of nausea and vomiting. She has no prior history of similar pain and has not had any recent illnesses. Her temperature is 37.4°C (99.3°F), blood pressure is 132/84 mmHg, heart rate is 88/min, and respiratory rate is 16/min. On physical examination, the abdomen is non-distended. There is moderate tenderness to deep palpation in the right upper quadrant, but no guarding, rigidity, or rebound tenderness. Murphy sign is negative. There is no scleral icterus or visible jaundice.

Laboratory studies show:
White blood cell count: 8,500/mm³
Total bilirubin: 2.2 mg/dL
Direct bilirubin: 1.6 mg/dL
Alkaline phosphatase: 245 U/L
Aspartate aminotransferase (AST): 140 U/L
Alanine aminotransferase (ALT): 165 U/L
Lipase: 42 U/L

A right upper quadrant transabdominal ultrasound reveals multiple gallstones within the gallbladder. The gallbladder wall thickness is 2 mm, and there is no pericholecystic fluid. The common bile duct measures 9 mm in diameter, but no obstructing stones are visualized within the duct.

Which of the following is the most appropriate next step in the diagnostic workup?

Magnetic resonance cholangiopancreatography

Endoscopic retrograde cholangiopancreatography

Computed tomography of the abdomen with intravenous contrast

Hepatobiliary iminodiacetic acid scintigraphy

Discharge home with scheduled outpatient cholecystectomy

Show answer & explanation

Answer: Magnetic resonance cholangiopancreatography

Answer

Magnetic resonance cholangiopancreatography

The correct answer is magnetic resonance cholangiopancreatography (MRCP). This patient presents with symptoms of biliary colic, abnormal liver chemistries (elevated bilirubin, AST, ALT, and alkaline phosphatase), and a dilated common bile duct (CBD) on ultrasound without a visualized stone. This clinical picture places her at intermediate risk (10-50% probability) for choledocholithiasis. According to clinical guidelines, the most appropriate next step for intermediate-risk patients is non-invasive imaging of the biliary tree using MRCP or endoscopic ultrasound (EUS). This step confirms the presence of a CBD stone before proceeding to an invasive therapeutic procedure.

Step-by-Step Solution

Evaluate the patient's clinical presentation, laboratory results, and initial imaging.

The patient has symptomatic right upper quadrant pain, elevated liver chemistries, an elevated total bilirubin of 2.2 mg/dL, and a dilated common bile duct (9 mm) on ultrasound without a visualized stone or acute cholecystitis.

Initial assessment is necessary to determine the risk of choledocholithiasis based on established guidelines.

Apply risk stratification criteria for choledocholithiasis.

The patient meets criteria for intermediate risk (10-50% probability) due to the presence of a dilated common bile duct and abnormal liver biochemistries. She does not meet high-risk criteria (e.g., bilirubin > 4 mg/dL with a dilated duct, a visualized stone, or clinical ascending cholangitis).

Risk stratification dictates the optimal sequencing of further diagnostic and therapeutic interventions.

Determine the most appropriate next step in management based on the assigned risk level.

For intermediate-risk patients, non-invasive imaging of the biliary tree is indicated.

Magnetic resonance cholangiopancreatography (MRCP) or endoscopic ultrasound (EUS) confirms the presence of a stone before subjecting the patient to the procedural risks of an invasive test like ERCP.

Key Concept

Patients at intermediate risk for choledocholithiasis (e.g., abnormal liver chemistries, dilated common bile duct without a visualized stone) should undergo non-invasive evaluation with magnetic resonance cholangiopancreatography (MRCP) or endoscopic ultrasound (EUS) prior to invasive procedures.

Question 2640Question →

A 66-year-old man comes to the pulmonary clinic complaining of a gradual onset of shortness of breath and a persistent, dry cough over the past seven months. He has no history of fever, chest pain, hemoptysis, or significant weight loss. He is a retired accountant, has no known occupational exposures, and has never smoked. His vital signs are within normal limits. On physical examination, there are bilateral fine end-inspiratory crackles auscultated at the lung bases, and digital clubbing is present. A high-resolution computed tomography (HRCT) scan of the chest is performed, revealing peripheral, subpleural, and bibasilar predominant reticular opacities. Additionally, there are multiple clustered cystic airspaces measuring 3 to 10 mm in diameter with thick walls, arranged in multiple layers at the lung bases. There is no significant ground-glass opacification, micronodules, or hilar lymphadenopathy. Based on these imaging findings, which of the following is the most likely diagnosis?

Idiopathic pulmonary fibrosis

Chronic hypersensitivity pneumonitis

Sarcoidosis

Cryptogenic organizing pneumonia

Nonspecific interstitial pneumonia

Show answer & explanation

Answer: Idiopathic pulmonary fibrosis

Answer

Idiopathic pulmonary fibrosis

The correct answer is idiopathic pulmonary fibrosis because the high-resolution computed tomography (HRCT) description perfectly matches the usual interstitial pneumonia (UIP) pattern. The UIP pattern is defined by a subpleural and basal predominance, reticular abnormalities, and most importantly, honeycombing (clustered cystic airspaces in multiple layers). The absence of findings such as predominant ground-glass opacities, micronodules, or air trapping further confirms this diagnosis.

Step-by-Step Solution

Analyze the patient's demographic and clinical presentation.

A 66-year-old man with a 7-month history of progressive dyspnea, dry cough, basilar crackles, and digital clubbing.

Establishing the clinical syndrome points toward a chronic interstitial lung disease.

Interpret the specific HRCT imaging features.

The scan shows a peripheral, subpleural, and bibasilar predominant distribution of reticular opacities and thick-walled cystic airspaces (honeycombing), without significant ground-glass opacities.

Identifying the radiologic pattern is required to differentiate the various types of interstitial lung diseases.

Correlate the imaging pattern with the diagnostic criteria.

The presence of subpleural, basal predominant reticulation with honeycombing strongly defines the Usual Interstitial Pneumonia (UIP) pattern. In the absence of an identifiable cause (e.g., connective tissue disease, exposures), this pattern is diagnostic of Idiopathic Pulmonary Fibrosis (IPF).

Determining the exact interstitial pneumonia pattern confirms the diagnosis and guides further management.

Key Concept

The diagnosis of idiopathic pulmonary fibrosis requires identifying a usual interstitial pneumonia (UIP) pattern on high-resolution computed tomography, characterized by subpleural, basal predominant reticular opacities and honeycombing.

Estimated Time:1m 30s

PreviousPage 132 / 237Next

All practice questions

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Alternative Method

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Alternative Method

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer