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Question 2921Question →

Emergency medical services bring a 38-year-old woman to the hospital after her husband noted her to be increasingly lethargic and speaking incoherently over the past 12 hours. The husband reports that she had been complaining of generalized weakness and low-grade fevers for the previous three days. She has no significant past medical history and takes no daily medications. Upon arrival, her temperature is 38.3°C (100.9°F), blood pressure is 142/85 mmHg, pulse is 108/min, and respiratory rate is 18/min. She is somnolent but arouses to verbal stimuli, appearing disoriented to time and place. Physical examination reveals scattered pinpoint red macules that do not blanch on the lower extremities and abdomen. Cardiopulmonary examination is unremarkable, and there is no nuchal rigidity.

Initial laboratory evaluation reveals:

Laboratory TestResultReference Range
Hemoglobin7.6 g/dL12.0-16.0 g/dL
Platelets18,000/mm³150,000-400,000/mm³
Leukocytes8,800/mm³4,500-11,000/mm³
Blood urea nitrogen28 mg/dL7-18 mg/dL
Serum creatinine1.6 mg/dL0.6-1.2 mg/dL
Total bilirubin3.2 mg/dL0.1-1.2 mg/dL
Indirect bilirubin2.7 mg/dL0.1-0.8 mg/dL
Prothrombin time (PT)12 sec11-15 sec
Activated partial thromboplastin time (aPTT)29 sec25-40 sec

A peripheral blood smear demonstrates marked thrombocytopenia and numerous fragmented red blood cells.

Based on the provided data, which of the following is the most likely diagnosis?

Show answer & explanation

Answer: Thrombotic thrombocytopenic purpura

Answer

Thrombotic thrombocytopenic purpura
The correct diagnosis is characterized by the classic pentad of microangiopathic hemolytic anemia (evidenced by low hemoglobin, elevated indirect bilirubin, and schistocytes), thrombocytopenia (causing petechiae), neurologic manifestations (lethargy, confusion), fever, and renal impairment. A critical distinguishing feature in formulating this specific differential is the normal prothrombin time and activated partial thromboplastin time, which indicate that the coagulation cascade is not consumed, solidifying TTP over other coagulopathies.

Step-by-Step Solution

1
Analyze the patient's clinical presentation.
The patient exhibits fever, progressive neurologic dysfunction (lethargy, confusion), and signs of severe thrombocytopenia (petechiae).
Identifying the core clinical syndrome is the first step in formulating an accurate differential diagnosis.
2
Evaluate the laboratory data and peripheral smear.
Labs show thrombocytopenia, anemia, elevated indirect bilirubin, and mild renal impairment. The smear reveals schistocytes, confirming a microangiopathic hemolytic anemia (MAHA). Coagulation times (PT/aPTT) are normal.
Objective data is required to differentiate between various causes of thrombocytopenia and hemolysis.
3
Synthesize findings to select the most likely diagnosis.
The combination of MAHA, thrombocytopenia, fever, neurologic deficits, and renal impairment with normal coagulation studies perfectly represents the classic pentad of thrombotic thrombocytopenic purpura.
Matching the comprehensive clinical and laboratory pattern to the underlying pathophysiology establishes the final diagnosis while ruling out mimics.

Key Concept

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening microangiopathy that classically presents with a pentad of microangiopathic hemolytic anemia, thrombocytopenia, neurologic abnormalities, fever, and renal impairment. Normal PT and aPTT are critical to differentiate it from disseminated intravascular coagulation (DIC).
Estimated Time:1m 30s
Question 2922Question →

A 68-year-old woman is brought to the emergency department by emergency medical services for severe, sudden-onset shortness of breath that began 45 minutes ago. She has a medical history of hypertension, type 2 diabetes mellitus, and coronary artery disease. Upon arrival, the patient is visibly distressed, diaphoretic, and using accessory muscles of respiration. She is unable to speak in full sentences. Vital signs are temperature 37.0°C (98.6°F), blood pressure 215/115 mmHg, heart rate 118/min, respiratory rate 34/min, and oxygen saturation 81% on room air. Physical examination reveals elevated jugular venous pressure and diffuse bilateral crackles extending to the mid-lung fields. She is expectorating pink, frothy sputum. Which of the following is the most appropriate initial step in the management of this patient?

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Answer: Initiate noninvasive positive pressure ventilation

Answer

The most appropriate initial step is to initiate noninvasive positive pressure ventilation to immediately stabilize the patient's respiratory status.
The correct response addresses the patient's acute hypoxic respiratory failure and severe work of breathing. This presentation is highly characteristic of acute decompensated heart failure (ADHF) with flash pulmonary edema, driven by a hypertensive emergency. In the acute setting, the primary goal of stabilization follows the ABCs (Airway, Breathing, Circulation). Noninvasive positive pressure ventilation (NIPPV), such as continuous positive airway pressure (CPAP) or bilevel positive airway pressure (BiPAP), is the cornerstone of immediate management for ADHF. It improves oxygenation, decreases the work of breathing, and provides positive intrathoracic pressure, which favorably reduces both preload and afterload. This critical therapeutic intervention must precede any diagnostic testing.

Step-by-Step Solution

1
Identify the primary pathophysiological process based on the clinical presentation.
The patient's acute severe dyspnea, extreme hypertension, severe hypoxia, and pink frothy sputum indicate acute decompensated heart failure presenting as flash pulmonary edema.
Accurate syndrome recognition is essential to direct the appropriate stabilization pathway.
2
Evaluate the patient's hemodynamic and respiratory stability.
The patient is in impending respiratory failure (SpO2 81%, RR 34/min, accessory muscle use) requiring immediate resuscitation.
According to the principles of initial stabilization and triage (ABCs), airway and breathing must be secured before any definitive diagnostic workup.
3
Determine the most appropriate immediate intervention.
Noninvasive positive pressure ventilation (NIPPV) is selected as the priority.
NIPPV provides rapid respiratory support, improves oxygenation, and reduces both cardiac preload and afterload, which is critical in hypertensive flash pulmonary edema.

Key Concept

In patients presenting with severe respiratory distress and hypoxia due to acute decompensated heart failure, immediate stabilization with noninvasive positive pressure ventilation (NIPPV) must be prioritized over diagnostic testing or disposition.
Question 2923Question →

A 60-year-old male with a 40-pack-year smoking history is undergoing preoperative evaluation for an elective inguinal hernia repair. A routine pre-admission posterior-anterior and lateral chest radiograph incidentally reveals a newly identified, 14-mm, non-calcified, solitary nodule in the right upper lobe. The patient is completely asymptomatic, has no history of malignancy, and his physical examination is unremarkable. According to established clinical guidelines for the evaluation of a solitary pulmonary nodule, arrange the following diagnostic steps in the most appropriate chronological order.

Drag items to arrange them in the correct order

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Answer

The correct sequence is: 1) Review previous chest radiographs, 2) Perform a non-contrast thin-section chest CT, 3) Obtain an FDG-PET scan, and 4) Proceed with tissue biopsy.
The evaluation of a newly discovered solitary pulmonary nodule (SPN) follows a strict, step-wise algorithm to balance diagnostic accuracy with the minimization of iatrogenic harm. The absolute first step is comparing the current radiograph to prior imaging; documented size stability over 2 years virtually guarantees a benign etiology. If no old films are available or the nodule has grown, a thin-slice non-contrast chest CT is required to define the anatomical characteristics of the nodule (size, borders, density). Because this patient's nodule is 14 mm (greater than the 8 mm threshold), finding indeterminate features on CT necessitates an FDG-PET scan to evaluate for metabolic activity and occult regional lymph node involvement. Finally, if the PET scan is hypermetabolic and suspicious for lung cancer, the patient must undergo a tissue biopsy to secure a definitive histological diagnosis prior to definitive surgical or oncologic management.

Step-by-Step Solution

1
Assess for radiographic stability by obtaining old films.
Determines if the nodule is new, growing, or stable.
Stability over 2 years strongly suggests a benign etiology (e.g., granuloma), avoiding unnecessary radiation and invasive procedures.
2
Order a thin-section CT scan of the chest without contrast.
Provides high-resolution anatomical detail of the nodule.
Essential for morphological risk stratification (spiculated margins, eccentric calcifications) if old films are unavailable or show change.
3
Order an FDG-PET scan for metabolic evaluation.
Differentiates metabolically active (potentially malignant) tissue from inactive tissue.
Guidelines recommend PET for nodules >8 mm with an intermediate probability of malignancy based on CT findings.
4
Perform a CT-guided percutaneous needle biopsy.
Yields a definitive histopathological diagnosis.
Required to confirm malignancy and determine the histologic subtype before initiating oncologic therapies or definitive anatomic resection.

Key Concept

The standard diagnostic algorithm for an incidental solitary pulmonary nodule prioritizes non-invasive, historical comparison before escalating to advanced imaging and ultimately invasive tissue sampling.
Question 2924Question →

A local health department in an endemic region is evaluating several patients who presented with acute febrile illnesses during the summer months. Match each patient's clinical presentation with the most likely diagnosis.

Click a left item, then click its matching right item

Items

A 62-year-old man with a history of hereditary spherocytosis requiring a surgical intervention in childhood presents with a 1-week history of fatigue, fevers, and dark urine. Labs show a hemoglobin of 8.2 g/dL, elevated lactate dehydrogenase, and a normal leukocyte count.
A 45-year-old woman presents with fevers, myalgias, and severe headache. Laboratory evaluation reveals a leukocyte count of 2,400/µL, platelet count of 88,000/µL, and elevated aminotransferases. A peripheral blood smear demonstrates morulae within mononuclear cells. She has no rash.
A 31-year-old man presents with acute onset of severe headache, fevers, and profound myalgias. Laboratory studies show a sodium level of 128 mEq/L and a platelet count of 95,000/µL. On examination, a maculopapular eruption is noted on the palms and soles.
A 54-year-old man presents with progressive fatigue, lightheadedness, and dyspnea on exertion. Examination reveals a heart rate of 42/min and a faint, 8-cm erythematous plaque with central clearing on his posterior thorax. Electrocardiogram confirms complete heart block.

Matches

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Answer

The presentation of hemolytic anemia in an asplenic patient matches Babesiosis. The presentation of cytopenias with mononuclear morulae matches Human monocytic ehrlichiosis. The presentation of hyponatremia with a palmar rash matches Rocky Mountain spotted fever. The presentation of heart block with an annular rash matches Lyme disease.
Formulating a differential diagnosis for tick-borne diseases requires synthesizing historical risk factors, rash characteristics, and laboratory findings. Babesiosis uniquely causes hemolysis, particularly in asplenic patients. Ehrlichiosis is characterized by cytopenias and morulae in monocytes. Rocky Mountain spotted fever is defined by its centripetal rash involving the palms and soles along with hyponatremia. Lyme disease is distinguished by erythema migrans and potential cardiac involvement (AV block).

Step-by-Step Solution

1
Analyze the first patient's surgical history and current laboratory findings.
Identified prior splenectomy (due to spherocytosis) and active hemolytic anemia (dark urine, high LDH, low hemoglobin).
Splenectomy causes a state of immunodeficiency against intraerythrocytic parasites, making Babesiosis the definitive diagnosis among tick-borne illnesses causing hemolysis.
2
Evaluate the second patient's cytopenias and peripheral smear.
Identified leukopenia, thrombocytopenia, elevated liver enzymes, and morulae in mononuclear cells without a rash.
These findings are highly specific for Human monocytic ehrlichiosis, distinguishing it from Anaplasmosis (which features granulocytic morulae) and diseases that typically cause a rash.
3
Assess the third patient's rash distribution and electrolyte abnormalities.
Identified a rash on the palms and soles combined with hyponatremia and thrombocytopenia.
A rash involving the palms and soles in a tick-endemic area strongly suggests Rocky Mountain spotted fever; hyponatremia is a frequently tested supportive clue due to ADH release or endothelial damage.
4
Interpret the fourth patient's cardiac findings and skin lesion.
Identified complete heart block and erythema migrans (annular lesion with central clearing).
Lyme disease classically presents with erythema migrans and can cause atrioventricular conduction delays (Lyme carditis) during the early disseminated phase.

Key Concept

Differentiating tick-borne illnesses based on classic triad presentations, specific laboratory derangements (e.g., hemolysis vs. cytopenias), and unique physical exam findings.
Estimated Time:2m 0s
Question 2925Question →

A 6262-year-old man with a 1515-year history of type 2 diabetes mellitus and hypertension is evaluated during a routine clinic visit. He reports feeling generally well but notes mild fatigue over the past few months. His current medications include metformin and amlodipine. Blood pressure is 135/85 mm Hg135/85 \text{ mm Hg} and pulse is 76/min76/\text{min}. Physical examination reveals decreased sensation to monofilament testing in both feet but no lower extremity edema.

Laboratory studies yield the following results:

SerumResult
Sodium138 mEq/L138 \text{ mEq/L}
Potassium5.7 mEq/L5.7 \text{ mEq/L}
Chloride111 mEq/L111 \text{ mEq/L}
Bicarbonate15 mEq/L15 \text{ mEq/L}
Blood urea nitrogen30 mg/dL30 \text{ mg/dL}
Creatinine1.6 mg/dL1.6 \text{ mg/dL}
Glucose165 mg/dL165 \text{ mg/dL}
UrineResult
pH5.25.2
Sodium50 mEq/L50 \text{ mEq/L}
Potassium20 mEq/L20 \text{ mEq/L}
Chloride45 mEq/L45 \text{ mEq/L}

Based on the laboratory data provided, which of the following is the most likely cause of this patient's acid-base and electrolyte abnormalities?

Show answer & explanation

Answer: Impaired aldosterone production or response

Answer

Impaired aldosterone production or response
The correct answer is impaired aldosterone production or response, which causes Type 4 renal tubular acidosis (RTA). This patient presents with a non-anion gap metabolic acidosis (NAGMA), evidenced by a serum anion gap of 12 mEq/L12 \text{ mEq/L} (138−[111+15]138 - [111 + 15]). The next step in evaluating a NAGMA is calculating the urine anion gap (UAG) using the formula UNa+UK−UClU_{Na} + U_{K} - U_{Cl}. This patient's UAG is markedly positive at +25 mEq/L+25 \text{ mEq/L} (50+20−4550 + 20 - 45), indicating impaired renal ammonium (NH4+NH_4^+) excretion. A positive UAG points to a renal tubular acidosis rather than gastrointestinal bicarbonate loss. Among the RTAs, the presence of hyperkalemia (5.7 mEq/L5.7 \text{ mEq/L}) and an appropriately acidic urine pH (<5.5< 5.5) are hallmark findings of Type 4 RTA (hyporeninemic hypoaldosteronism). This condition is most commonly caused by diabetic nephropathy, which perfectly aligns with this patient's long-standing diabetes and mild renal insufficiency.

Step-by-Step Solution

1
Calculate the serum anion gap to classify the metabolic acidosis.
138−(111+15)=12 mEq/L138 - (111 + 15) = 12 \text{ mEq/L}.
A normal anion gap (8−12 mEq/L8-12 \text{ mEq/L}) identifies a non-anion gap metabolic acidosis (NAGMA), ruling out causes like diabetic ketoacidosis or lactic acidosis.
2
Calculate the urine anion gap (UAG) to determine the source of the NAGMA.
UNa+UK−UCl=50+20−45=+25 mEq/LU_{Na} + U_{K} - U_{Cl} = 50 + 20 - 45 = +25 \text{ mEq/L}.
A positive UAG indicates low urinary ammonium excretion, pointing to a renal etiology (renal tubular acidosis) rather than a gastrointestinal etiology (where UAG would be negative).
3
Evaluate serum potassium and urine pH to differentiate the types of renal tubular acidosis (RTA).
Serum potassium is high (5.7 mEq/L5.7 \text{ mEq/L}) and urine pH is appropriately acidic (5.25.2).
Hyperkalemia and a urine pH <5.5< 5.5 in the setting of an RTA specifically identify Type 4 RTA, commonly caused by hyporeninemic hypoaldosteronism.

Key Concept

The diagnostic evaluation of a non-anion gap metabolic acidosis requires calculating the urine anion gap to distinguish between renal and gastrointestinal etiologies, followed by assessing serum potassium to differentiate the types of renal tubular acidosis.
Estimated Time:2m 0s
Question 2926Question →

A 62-year-old female is evaluated in the inpatient dermatology consultation service for exquisitely painful, violaceous, and necrotic skin lesions on her bilateral thighs and lower abdomen that have rapidly progressed over the past two weeks. She has a history of end-stage renal disease secondary to diabetic nephropathy and receives hemodialysis three times weekly. She also has a history of permanent atrial fibrillation and diet-controlled type 2 diabetes mellitus. Her current medications include calcium acetate, calcitriol, warfarin, and metoprolol succinate. Vital signs are within normal limits. Physical examination reveals retiform purpura with central areas of black eschar and surrounding indurated erythema on the proximal lower extremities and adiposity-rich areas of the abdomen. The lesions are extremely tender to palpation. Peripheral pulses are intact. Laboratory evaluation shows:

Serum calcium: 10.2 mg/dL10.2 \text{ mg/dL}
Serum phosphorus: 7.8 mg/dL7.8 \text{ mg/dL}
Intact parathyroid hormone (PTH): 850 pg/mL850 \text{ pg/mL}
International Normalized Ratio (INR): 2.42.4

A punch biopsy of the lesion margin demonstrates microvascular calcification, extensive intimal fibroplasia, and cutaneous ischemia without evidence of systemic vasculitis. Which of the following sets of pharmacologic interventions is most appropriate for the management of this patient's dermatologic condition?

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Answer: Initiate intravenous sodium thiosulfate, substitute calcium acetate with sevelamer, and transition warfarin to apixaban

Answer

The most appropriate management is to initiate intravenous sodium thiosulfate, substitute calcium acetate with sevelamer, and transition warfarin to apixaban.
The correct combination directly addresses the three pillars of calciphylaxis management in this patient: active treatment, calcium-phosphorus product reduction, and removal of iatrogenic triggers. Intravenous sodium thiosulfate acts as a calcium chelator and antioxidant to promote lesion healing. Calcium acetate must be stopped because it contributes to an unacceptably high calcium-phosphorus product (>55 mg2/dL2> 55 \text{ mg}^2\text{/dL}^2 is high risk); it should be replaced with a non-calcium, non-aluminum binder like sevelamer. Finally, warfarin is a notorious trigger for calciphylaxis because it inhibits the vitamin K-dependent activation of Matrix Gla Protein, a critical defense against vascular calcification. Since the patient requires ongoing anticoagulation for atrial fibrillation, switching to apixaban is appropriate, as it does not inhibit MGP and has an established safety profile in hemodialysis patients.

Step-by-Step Solution

1
Diagnose the primary dermatologic condition based on clinical and biopsy findings.
The patient has calciphylaxis (calcific uremic arteriolopathy).
The presentation of exquisitely painful retiform purpura with necrotic eschars in an end-stage renal disease (ESRD) patient, combined with a high calcium-phosphorus product (10.2×7.8=79.56 mg2/dL210.2 \times 7.8 = 79.56 \text{ mg}^2\text{/dL}^2) and biopsy showing microvascular calcification without vasculitis, is pathognomonic.
2
Identify current medications that are exacerbating the condition.
Calcium acetate, calcitriol, and warfarin must be discontinued.
Calcium acetate and calcitriol actively increase the serum calcium and phosphorus burden. Warfarin acts as a direct molecular trigger for calciphylaxis by inhibiting the vitamin K-dependent carboxylation of Matrix Gla Protein (MGP), an essential endogenous inhibitor of tissue calcification.
3
Select the appropriate pharmacologic substitutions and targeted therapies.
Use sodium thiosulfate, sevelamer, and apixaban.
Intravenous sodium thiosulfate is a potent antioxidant and vasodilator that increases the solubility of calcium deposits. Sevelamer provides necessary phosphate binding without adding a calcium load. Apixaban provides required systemic anticoagulation for atrial fibrillation with established safety and FDA approval for patients on hemodialysis, unlike dabigatran, rivaroxaban, or enoxaparin.

Key Concept

Successful management of calciphylaxis in ESRD requires initiating intravenous sodium thiosulfate, aggressively lowering the calcium-phosphorus product (avoiding calcium-based binders and active vitamin D), and discontinuing warfarin, which actively promotes vascular calcification via inhibition of Matrix Gla Protein.
Question 2927Question →

A primary care physician is evaluating a 62-year-old man who presents to the ambulatory clinic with a nonhealing ulcer on the plantar surface of his left foot. The patient first noticed the lesion four weeks ago. His medical history is significant for poorly controlled type 2 diabetes mellitus, hypertension, and chronic kidney disease with a baseline serum creatinine of 2.2 mg/dL. His temperature is 37.6°C (99.7°F), blood pressure is 145/88 mm Hg, and pulse is 88/min. Physical examination reveals a 3-cm diameter ulceration under the first metatarsal head. There is surrounding erythema, induration, and a moderate amount of purulent exudate. A sterile blunt probe inserted into the ulcer bed easily contacts hard, gritty tissue. Sensation to a 10-g monofilament is absent globally over both feet. Dorsalis pedis pulses are palpable bilaterally. Which of the following is the most appropriate initial imaging study to order for this patient?

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Answer: Plain radiography of the foot

Answer

Plain radiography of the foot
The patient's clinical presentation, particularly the positive probe-to-bone test, strongly suggests osteomyelitis. According to the Infectious Diseases Society of America (IDSA) and the International Working Group on the Diabetic Foot (IWGDF), plain radiography of the affected foot is the most appropriate initial imaging study for all patients presenting with a new diabetic foot infection. It is a rapid, cost-effective method to evaluate for cortical bone destruction, periosteal reaction, soft-tissue gas, and foreign bodies. Although it has low sensitivity in the first two weeks of infection, it establishes a crucial baseline for longitudinal comparison.

Step-by-Step Solution

1
Analyze the patient's clinical presentation.
The patient has a chronic diabetic foot ulcer with purulent drainage and a positive probe-to-bone test.
A positive probe-to-bone test in the setting of a diabetic foot infection is highly predictive of underlying osteomyelitis.
2
Determine the optimal diagnostic imaging sequence for suspected diabetic foot osteomyelitis.
Guidelines recommend starting with plain films before progressing to advanced imaging.
Cost-effective, preliminary imaging is required to identify gross bone destruction, assess for soft-tissue gas, and establish a baseline for future radiographic comparison.
3
Evaluate the patient for specific contraindications to imaging studies.
The patient has chronic kidney disease with an elevated creatinine level (2.2 mg/dL).
This confirms that any modality requiring nephrotoxic intravenous contrast must be avoided.

Key Concept

In patients with suspected diabetic foot osteomyelitis, plain radiography is the recommended initial imaging study, even though advanced modalities are more sensitive.
Question 2928Question →

A 64-year-old man is evaluated in the emergency department for the sudden onset of severe, continuous dizziness, nausea, and vomiting that began 2 hours ago. He reports feeling as though the room is spinning and is unable to walk without assistance. His medical history is significant for type 2 diabetes mellitus, hypertension, and hyperlipidemia. His current medications include metformin, lisinopril, and atorvastatin. Vital signs reveal a blood pressure of 168/92 mmHg, a heart rate of 88/min, and a respiratory rate of 16/min. Point-of-care blood glucose is 128 mg/dL. A basic metabolic panel obtained in triage reveals a serum sodium of 134 mEq/L and potassium of 4.1 mEq/L. On physical examination, a targeted bedside vestibular evaluation is performed. When the patient is instructed to fixate his vision on the examiner's nose while his head is rapidly rotated to the left and right, his eyes remain continuously fixed on the target without any corrective saccades. Extraocular movement testing demonstrates nystagmus that beats to the left when looking left, and beats to the right when looking right. Alternate cover testing of the eyes reveals a vertical misalignment. Hearing is intact to finger rub bilaterally. Based on these physical examination findings, which of the following is the most appropriate next step in management?

Show answer & explanation

Answer: Admit the patient to the hospital and obtain magnetic resonance imaging of the brain

Answer

The most appropriate next step is to admit the patient to the hospital and obtain magnetic resonance imaging of the brain.
The correct step addresses the high likelihood of an acute posterior circulation stroke. The HINTS examination is more sensitive than early MRI for detecting acute strokes in the posterior fossa. A 'normal' head impulse test in a patient with continuous vertigo, along with direction-changing nystagmus and vertical skew, are classic indicators of a central neurological lesion. The patient must be admitted for stroke workup and MRI.

Step-by-Step Solution

1
Analyze the patient's clinical presentation and risk factors.
The patient is an older male with multiple vascular risk factors (diabetes, hypertension, hyperlipidemia) presenting with sudden, unremitting vertigo, raising significant suspicion for an acute cerebrovascular event.
Establishing the pre-test probability helps guide the interpretation of subsequent physical examination maneuvers.
2
Interpret the specific components of the targeted physical examination.
The patient demonstrates a normal head impulse test (eyes remain fixed without corrective saccades), direction-changing nystagmus, and a vertical skew deviation.
These three components make up the HINTS (Head Impulse, Nystagmus, Test of Skew) examination, which is used to differentiate central from peripheral causes of acute vestibular syndrome.
3
Synthesize the examination findings to establish a diagnosis and formulate a management plan.
The presence of any single central sign on the HINTS exam (normal head impulse in the setting of continuous vertigo, bidirectional nystagmus, or skew deviation) strongly points to a central lesion, such as a cerebellar or brainstem infarction. Therefore, the patient requires admission and advanced neuroimaging (MRI).
Acute posterior circulation strokes can be life-threatening and require immediate inpatient evaluation; they are often not visible on initial non-contrast head CT scans, making MRI the preferred imaging modality.

Key Concept

In patients presenting with acute, continuous vertigo, a positive HINTS exam (normal Head Impulse test, direction-changing Nystagmus, or presence of a Test of Skew) indicates a central etiology such as a posterior circulation stroke, necessitating immediate neuroimaging and hospital admission.
Estimated Time:1m 15s
Question 2929Question →

An otherwise healthy 42-year-old male arrives for a health maintenance visit. During the review of systems, he describes a steady decline in sexual desire and persistent daytime fatigue that has developed over the last eight months. He mentions that spontaneous early morning erections have become rare. He gets at least seven hours of restful sleep each night and denies any recent life stressors, mood changes, or new medication use. Vital signs are normal. Physical examination shows bilateral testicular volumes of 18 mL (normal: 15-25 mL), normal secondary sexual characteristics, and no evidence of gynecomastia. Visual fields are intact. Place the following diagnostic laboratory evaluation steps in the correct sequential order to appropriately work up this patient's suspected condition.

Drag items to arrange them in the correct order

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Answer

The correct diagnostic sequence is: Initial early morning serum total testosterone, followed by a confirmatory repeat early morning total testosterone, then measurement of LH and FSH, and finally serum prolactin and ferritin.
The evaluation of male hypogonadism requires a strict stepwise laboratory approach. It begins with a morning total testosterone level. Because levels can be transiently suppressed by stress, sleep deprivation, or minor illnesses, a single low value must ALWAYS be confirmed with a second early morning measurement on a different day. Only after true biochemical hypogonadism is confirmed should the clinician order LH and FSH to classify the defect as primary or secondary. If secondary hypogonadism is identified, checking prolactin and ferritin helps rule out prolactinomas and hemochromatosis before considering a pituitary MRI.

Step-by-Step Solution

1
Order an initial early morning serum total testosterone level.
Screens for biochemical hypogonadism.
Testosterone levels fluctuate throughout the day and are highest in the early morning (8:00 AM to 10:00 AM).
2
Order a repeat early morning serum total testosterone level.
Confirms the diagnosis of biochemical hypogonadism.
Up to 30% of men with an initial low testosterone level will have a normal level on repeat testing due to transient factors like acute illness, poor sleep, or assay variability.
3
Order serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
Distinguishes hypergonadotropic (primary) from hypogonadotropic (secondary) hypogonadism.
Gonadotropins localize the defect to either the testicles (elevated LH/FSH) or the hypothalamic-pituitary axis (low or inappropriately normal LH/FSH).
4
Order targeted laboratory tests such as serum prolactin and ferritin.
Identifies the specific etiology of secondary hypogonadism.
If the patient has secondary hypogonadism, further workup is required to rule out hyperprolactinemia, hemochromatosis, or pituitary mass lesions.

Key Concept

Stepwise diagnostic laboratory sequencing for male hypogonadism
Estimated Time:1m 30s
Question 2930Question →

A 58-year-old man presents to the emergency department with a 3-day history of progressively worsening mid-back pain and subjective fevers. Over the past 12 hours, he has noted profound weakness in both legs and an inability to urinate. His medical history is significant for type 2 diabetes mellitus and opioid use disorder, with his last intravenous injection occurring one week ago. His temperature is 38.6°C (101.5°F), blood pressure is 110/70 mmHg, pulse is 108/min, and respiratory rate is 18/min. Physical examination reveals focal tenderness to percussion over the midthoracic spine. Neurologic examination demonstrates 3/5 motor strength in the bilateral lower extremities, decreased pinprick sensation below the umbilicus, and absent patellar and Achilles reflexes. Digital rectal examination reveals markedly diminished anal sphincter tone. Which of the following diagnostic tests are indicated as the most appropriate next steps in this patient's evaluation? (Select all that apply)

Select all that apply

Show answer & explanation

Answer: Magnetic resonance imaging of the entire spine with and without contrast; Peripheral blood cultures

Answer

The most appropriate immediate diagnostic steps are magnetic resonance imaging of the entire spine with and without contrast, and peripheral blood cultures.
This patient's presentation of fever, focal back pain, and acute myelopathy in the setting of intravenous drug use is highly suspicious for a spinal epidural abscess (SEA) causing acute spinal cord compression. The diagnostic workup must rapidly confirm the presence and extent of the abscess and identify the causative pathogen simultaneously. Magnetic resonance imaging of the entire spine with and without gadolinium contrast is the gold-standard imaging modality. The entire spine is evaluated because synchronous, non-contiguous skip lesions are common. Concurrently, peripheral blood cultures should be obtained before initiating empiric antimicrobial therapy, as they are frequently positive and can often obviate the need for invasive epidural tissue sampling.

Step-by-Step Solution

1
Analyze the clinical presentation and physical examination findings.
The patient exhibits the classic triad of spinal epidural abscess (SEA): severe back pain, fever, and acute neurologic deficits (paraparesis, sensory level, urinary retention, and diminished rectal tone). The risk is elevated by his history of intravenous drug use and diabetes.
Recognizing the syndrome of acute spinal cord compression secondary to infection dictates the urgency and type of the diagnostic workup.
2
Determine the optimal imaging strategy.
Urgent magnetic resonance imaging (MRI) of the entire spine with and without gadolinium contrast is indicated.
MRI provides the necessary soft-tissue resolution to identify an epidural abscess and assess cord compression. The entire spine must be imaged because non-contiguous 'skip' lesions occur in nearly 10% of cases.
3
Determine the appropriate microbiologic diagnostic sequencing.
Peripheral blood cultures must be drawn concurrently with the arrangement for imaging.
Blood cultures will identify the causative organism (most commonly Staphylococcus aureus) in over 60% of cases. They must be obtained prior to the administration of empiric broad-spectrum antibiotics to guide definitive therapy.

Key Concept

Diagnostic Workup and Test Sequencing for suspected spinal epidural abscess requires immediate, concurrent execution of non-invasive definitive imaging (whole-spine MRI) and microbiologic sampling (blood cultures), while strictly avoiding contraindicated procedures like lumbar puncture.
Question 2931Question →

During a clinical evaluation, eliciting a detailed travel, occupational, and environmental exposure history is critical for formulating an accurate differential diagnosis. Match each patient's specific exposure history to the most likely infectious disease diagnostic consideration.

Click a left item, then click its matching right item

Items

A 34-year-old presents with acute respiratory distress, fever, and myalgias two weeks after sweeping an abandoned, mouse-infested cabin in rural New Mexico.
A 28-year-old presents with chronic cough, fever, and weight loss following a spelunking expedition in bat-inhabited caves along the Ohio River Valley.
A 42-year-old farm worker presents with high fever, headache, and atypical pneumonia shortly after assisting a veterinarian with a difficult sheep parturition.
A 45-year-old presents with fever, chills, and an ulcer on the hand with regional lymphadenopathy after skinning wild rabbits during a hunting trip in Arkansas.

Matches

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Answer

The correct matches align each specific environmental, occupational, or travel exposure to its corresponding zoonotic or endemic pathogen.
A thorough medical history evaluation must include targeted questions regarding travel, occupation, and environmental exposures, as these factors provide critical diagnostic clues. Recognizing the specific vector or environmental reservoir allows the physician to accurately prioritize the differential diagnosis for zoonotic and endemic infections.

Step-by-Step Solution

1
Analyze the geographic and environmental context of the patient's exposure history.
Identify the specific endemic region and the nature of the environmental interaction (e.g., caves in the Ohio River Valley, rodent droppings in the Southwest).
Endemic fungi and viruses have specific geographic distributions and ecological niches.
2
Evaluate the specific animal or vector contact described in the history.
Link sheep parturition to Coxiella burnetii, wild rabbits to Francisella tularensis, bat guano to Histoplasma capsulatum, and deer mouse droppings to Hantavirus.
Zoonotic infections require specific animal reservoirs, and identifying the reservoir is key to determining the correct etiology.
3
Synthesize the historical clues with the clinical presentation to finalize the diagnostic matches.
Match each patient profile to the corresponding infectious disease.
A comprehensive medical history evaluation directly dictates the most likely infectious etiology in these scenarios.

Key Concept

Evaluating environmental, travel, and occupational exposure history is critical for diagnosing zoonotic and endemic infectious diseases.
Question 2932Question →

A 45-year-old man with a history of traumatic brain injury and alcohol use disorder is brought to the emergency department by emergency medical services due to a continuous seizure. Paramedics report the patient has had uninterrupted generalized tonic-clonic movements for the past 18 minutes. He is unresponsive and exhibits continuous rhythmic motor activity of all four extremities. His blood pressure is 152/94 mmHg, heart rate is 128/min, and oxygen saturation is 95% on a non-rebreather mask. Two large-bore peripheral intravenous lines are successfully established.

Arrange the following pharmacologic interventions in the correct protocolized sequence for escalating the management of status epilepticus, starting with the initial first-line therapy.

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Answer

The correct sequence for escalating the management of status epilepticus is: 1) Intravenous lorazepam, 2) Intravenous fosphenytoin, 3) Intravenous propofol infusion, 4) Intravenous pentobarbital coma.
Status epilepticus is a neurologic emergency requiring a strict, time-dependent algorithmic approach to pharmacologic management. The sequence is defined by phases based on seizure duration and response to prior medications.

1. Initial Therapy (First-line): Intravenous lorazepam (or diazepam/midazolam) is the immediate treatment of choice. Benzodiazepines rapidly enhance GABA_A receptor activity to terminate the seizure.

2. Urgent Control Therapy (Second-line): Intravenous fosphenytoin (or valproate/levetiracetam) is administered to achieve sustained seizure control and prevent recurrence, especially if benzodiazepines fail to halt the seizure. Fosphenytoin blocks voltage-gated sodium channels.

3. Refractory Therapy (Third-line): If seizures persist despite first- and second-line agents (refractory status epilepticus), patients require intubation and continuous intravenous anesthetic infusions, such as propofol or midazolam, to suppress cortical electrical activity.

4. Super-Refractory Therapy (Fourth-line): For seizures that persist despite 24 hours of anesthetic infusions, induction of a barbiturate coma (e.g., intravenous pentobarbital) is the final escalation step to achieve profound burst suppression on an electroencephalogram.

Step-by-Step Solution

1
Identify the clinical presentation and timing.
The patient is in continuous generalized tonic-clonic status epilepticus for 18 minutes.
Seizure duration greater than 5 minutes defines status epilepticus, necessitating immediate protocolized pharmacologic escalation.
2
Determine the first-line therapy (initial phase).
Intravenous lorazepam is the initial drug of choice.
Rapid-acting benzodiazepines are the most effective agents for rapidly terminating prolonged seizure activity.
3
Determine the second-line therapy (established phase).
Intravenous fosphenytoin is administered next.
To prevent recurrence or terminate ongoing seizures if benzodiazepines fail, a long-acting non-benzodiazepine antiseizure drug must be given.
4
Determine the third-line therapy (refractory phase).
Intravenous propofol infusion is initiated.
Seizures refractory to first- and second-line agents require general anesthesia and intubation.
5
Determine the final rescue therapy (super-refractory phase).
Intravenous pentobarbital coma is used.
When standard anesthetic infusions fail, barbiturate coma is induced to achieve electroencephalographic burst suppression.

Key Concept

The algorithmic escalation of pharmacotherapy in status epilepticus progresses sequentially from rapid-acting benzodiazepines to non-benzodiazepine antiseizure medications, continuous anesthetics, and finally barbiturate coma.
Question 2933Question →

A 32-year-old woman is evaluated in the clinic for right lower extremity swelling and pain that began two days ago. Venous Doppler ultrasonography confirms an acute deep vein thrombosis in the right popliteal vein. Her past medical history is significant for a spontaneous abortion at 14 weeks gestation two years ago. She takes no medications and has no family history of bleeding or clotting disorders. Physical examination is unremarkable except for moderate right calf swelling and tenderness.

Laboratory results are as follows:

Laboratory TestResultReference Range
Hemoglobin13.2 g/dL12.0-16.0 g/dL
Platelet count210,000/mm³150,000-400,000/mm³
Prothrombin time (PT)12.5 seconds11-15 seconds
Activated partial thromboplastin time (aPTT)62 seconds25-40 seconds

A 1:11:1 mixing study with normal pooled plasma is performed. Immediately after mixing, the patient's aPTT is 58 seconds.

Based on these laboratory findings, which of the following is the most likely diagnosis?

Show answer & explanation

Answer: Antiphospholipid syndrome

Answer

Antiphospholipid syndrome
The correct diagnosis is antiphospholipid syndrome. This patient presents with a history of recurrent thrombotic events (deep vein thrombosis and a second-trimester miscarriage). Her laboratory workup reveals an isolated prolonged aPTT. The crucial diagnostic step is the 1:1 mixing study with normal pooled plasma, which fails to correct the aPTT. This failure to correct indicates the presence of a circulating inhibitor in the patient's serum that inhibits the coagulation cascade in the laboratory assay. The lupus anticoagulant is an antiphospholipid antibody that binds to the phospholipids used in the aPTT test, artificially prolonging the result. Despite this in vitro prolongation, lupus anticoagulant is paradoxically prothrombotic in vivo, perfectly matching this patient's clinical presentation.

Step-by-Step Solution

1
Analyze the baseline coagulation profile.
The patient has an isolated prolongation of the activated partial thromboplastin time (aPTT) with a normal prothrombin time (PT) and normal platelet count.
Identifying the specific pathway abnormality (intrinsic vs. extrinsic vs. common) is the first step in diagnosing a coagulopathy.
2
Interpret the results of the 1:1 mixing study.
The aPTT remains prolonged (58 seconds) despite the addition of normal pooled plasma.
A failure to correct indicates the presence of a coagulation inhibitor (e.g., lupus anticoagulant or specific factor inhibitor) rather than a simple factor deficiency.
3
Synthesize the laboratory data with the clinical scenario.
The patient has a circulating inhibitor in the setting of deep vein thrombosis and a history of mid-trimester spontaneous abortion.
Lupus anticoagulant acts as an inhibitor in vitro (prolonging the aPTT) but is strongly prothrombotic in vivo, characteristic of antiphospholipid syndrome.

Key Concept

In evaluating an isolated prolonged aPTT, a mixing study differentiates between a factor deficiency (which corrects) and an inhibitor (which does not correct). A non-correcting mixing study in a patient with thrombosis strongly suggests lupus anticoagulant associated with antiphospholipid syndrome.
Question 2934Question →

A 47-year-old multiparous woman presents to the emergency department complaining of acute, severe right upper quadrant abdominal pain that radiates to her right scapula. The pain began 6 hours ago after she consumed a large, fatty meal. She also reports nausea, two episodes of emesis, and subjective fever. Her temperature is 38.2°C (100.8°F), blood pressure is 138/85 mmHg, and heart rate is 102/min. Physical examination reveals voluntary guarding and an inspiratory arrest upon deep palpation of the right upper quadrant. Laboratory studies show a leukocyte count of 14,500/mm314,500/mm^3 with a left shift, but normal serum bilirubin, alkaline phosphatase, and lipase levels.

Arrange the following imaging modalities in the correct evidence-based sequential order for establishing a diagnosis, from the most appropriate initial diagnostic test to the tests utilized for equivocal results or suspected complications.

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Answer

The correct diagnostic sequence is: 1) Transabdominal ultrasonography, 2) HIDA cholescintigraphy, 3) Contrast-enhanced CT of the abdomen.
The correct algorithm for suspected acute cholecystitis dictates that transabdominal ultrasonography is always the initial imaging test of choice due to its high sensitivity for gallstones and safety profile. If the ultrasound is indeterminate (e.g., stones are seen but the gallbladder wall is normal and Murphy sign is absent), a HIDA scan is performed next to functionally test for cystic duct patency. A CT scan of the abdomen is positioned later in the algorithm; it is not a primary screening tool for cholecystitis but is critical for identifying severe complications (like gangrene or perforation) or differentiating other causes of acute abdomen if biliary imaging is negative.

Step-by-Step Solution

1
Analyze the clinical presentation.
The patient has classic signs of acute cholecystitis, including postprandial right upper quadrant pain radiating to the scapula, fever, leukocytosis, and a positive Murphy sign.
Establishing the high pretest probability of acute cholecystitis directs the initial choice of imaging to the gallbladder and biliary tree.
2
Determine the most appropriate initial imaging study.
Transabdominal ultrasonography of the right upper quadrant is selected as the first step.
Ultrasound is the most sensitive, specific, fast, and cost-effective initial imaging modality for evaluating gallstones and signs of gallbladder inflammation.
3
Identify the next diagnostic step if the initial imaging is equivocal.
Hepatobiliary iminodiacetic acid (HIDA) cholescintigraphy is sequenced second.
If an ultrasound shows gallstones but no clear inflammatory signs, a HIDA scan is the gold standard next step to confirm or rule out cystic duct obstruction (indicated by non-visualization of the gallbladder).
4
Determine the role of cross-sectional imaging in the diagnostic algorithm.
Contrast-enhanced CT of the abdomen is sequenced last.
CT is less sensitive for gallstones and exposes the patient to radiation. It is reserved for patients where ultrasound and HIDA are non-diagnostic, or when clinical deterioration suggests complications like perforation or abscess formation.

Key Concept

The standard step-wise imaging algorithm for suspected acute cholecystitis begins with a right upper quadrant ultrasound, followed by a HIDA scan for equivocal cases, and utilizes a CT scan primarily for evaluating potential complications.
Question 2935Question →

During a multidisciplinary urology radiology case conference, a physician is tasked with interpreting abdominal computed tomography (CT) scans to determine appropriate patient management. Accurate interpretation of pathognomonic imaging signs is critical for differentiating between conditions that require emergent surgical intervention, targeted embolization, or observation. Match each distinct cross-sectional CT imaging finding on the right with its most likely corresponding renal diagnosis on the left.

Click a left item, then click its matching right item

Items

Xanthogranulomatous pyelonephritis
Renal angiomyolipoma
Renal oncocytoma
Emphysematous pyelonephritis

Matches

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Answer

The correct matching pairs associate Xanthogranulomatous pyelonephritis with the enlarged kidney containing a central staghorn calculus; Renal angiomyolipoma with the mass demonstrating -40 to -80 Hounsfield units; Renal oncocytoma with the mass exhibiting a central stellate scar; and Emphysematous pyelonephritis with the presence of gas collections in the renal parenchyma.
Each specific renal pathology possesses highly characteristic features on computed tomography that guide a physician's subsequent management decisions. Hounsfield units between -40 and -80 specifically quantify macroscopic fat, diagnostic of an angiomyolipoma. A central staghorn calculus with surrounding parenchymal replacement forms the classic 'bear paw' sign of xanthogranulomatous pyelonephritis. Intraparenchymal gas defines emphysematous pyelonephritis, denoting a critical surgical emergency. Finally, a central stellate scar is the hallmark radiologic feature of a benign renal oncocytoma.

Step-by-Step Solution

1
Analyze the imaging finding detailing negative Hounsfield units (-40 to -80 HU).
Identifies the presence of macroscopic fat within the lesion.
Macroscopic fat in a renal cortical mass is highly specific for a benign angiomyolipoma, successfully differentiating it from most malignant renal cell carcinomas and directing the clinician away from unnecessary nephrectomy.
2
Analyze the finding of an enlarged kidney with a central staghorn calculus and low-attenuation spaces.
Correlates the chronic obstruction and 'bear paw' sign with xanthogranulomatous pyelonephritis.
Chronic obstruction from a staghorn calculus leads to severe chronic inflammation and parenchymal destruction by lipid-laden macrophages, which is the defining pathophysiologic process of this specific chronic granulomatous condition.
3
Evaluate the finding of intraparenchymal and perirenal gas collections.
Diagnoses emphysematous pyelonephritis.
Gas-forming organisms (typically Escherichia coli or Klebsiella) cause necrotizing infection in the renal parenchyma. Recognizing this imaging sign is critical as it indicates a surgical emergency requiring immediate drainage or nephrectomy alongside broad-spectrum antibiotics.
4
Identify the solid mass with a central stellate scar.
Correlates the classic morphologic appearance with a renal oncocytoma.
While sometimes indistinguishable from renal cell carcinoma on many imaging modalities, the central stellate scar on a contrast-enhanced CT scan is a classic sign of this benign tumor, though pathologic confirmation is often still required.

Key Concept

Radiographic identification of pathognomonic renal lesions on computed tomography to guide appropriate clinical management.
Question 2936Question →

Paramedics rush a 1919-year-old college sophomore into the trauma bay following a 911 call from his dormitory roommates. The roommates report that he complained of an excruciating headache and severe nausea earlier in the day before becoming increasingly lethargic. He has no significant past medical history, takes no medications, and his vaccination status is unknown. Upon arrival, the patient is unresponsive to verbal commands and only groans in response to sternal rub (Glasgow Coma Scale score of 88). A petechial rash is noted on his lower extremities.

Initial vital signs show a temperature of 39.6∘C39.6^\circ\text{C} (103.3∘F103.3^\circ\text{F}), heart rate of 138/min138\text{/min}, blood pressure of 82/48 mm Hg82/48\text{ mm Hg}, respiratory rate of 8/min8\text{/min} with shallow effort, and oxygen saturation of 88%88\% on room air.

Arrange the following clinical interventions in the most appropriate sequential order for this patient's initial stabilization and diagnostic workup.

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Answer

The correct sequence is: 1) Endotracheal intubation, 2) IV fluids and empiric antibiotics, 3) CT scan of the head, and 4) Lumbar puncture.
The correct sequence prioritizes life-saving stabilization (ABCs) before medical management of shock/infection, followed by safe diagnostic sequencing. The patient's GCS of 8 and respiratory failure mandate immediate endotracheal intubation. Next, severe sepsis and suspected meningococcal meningitis require immediate fluid resuscitation, blood cultures, and empiric antibiotics (e.g., ceftriaxone, vancomycin, dexamethasone). Only after systemic stabilization should definitive diagnostic testing proceed. Because the patient has altered mental status, a CT scan of the head must be performed to rule out mass effect before safely proceeding to a lumbar puncture.

Step-by-Step Solution

1
Assess the airway and breathing first in any critically ill patient.
The patient has a GCS of 8 and respiratory depression, indicating an inability to protect his airway.
Securing the airway via endotracheal intubation prevents aspiration and corrects life-threatening hypoxia.
2
Evaluate and treat hemodynamic instability and the underlying life-threatening infection.
Intravenous fluids, blood cultures, and empiric antibiotics (with dexamethasone) are administered.
The patient is in septic shock with suspected meningococcemia. Antibiotics must be given as early as possible and never delayed for imaging or procedures.
3
Determine the safety of performing a lumbar puncture.
A non-contrast CT of the head is ordered.
Altered mental status (GCS 8) is a classic indication for neuroimaging prior to a lumbar puncture to rule out mass effect and prevent brain herniation.
4
Perform definitive diagnostic testing.
A lumbar puncture is performed.
Once mass effect is ruled out by the CT scan, cerebrospinal fluid can be safely collected to identify the specific pathogen and tailor directed antibiotic therapy.

Key Concept

In patients with suspected bacterial meningitis and altered mental status, the correct management sequence is: 1) Secure ABCs (intubation if GCS ≤ 8), 2) Blood cultures and empiric antibiotics, 3) CT head, and 4) Lumbar puncture.
Estimated Time:1m 0s
Question 2937Question →

A 45-year-old woman is evaluated in the emergency department for severe, colicky right upper quadrant abdominal pain that radiates to her right scapula, accompanied by nausea. The pain began 6 hours ago after she ate a heavy meal. She is afebrile, and her vital signs are within normal limits. Physical examination reveals tenderness to palpation in the right upper quadrant without rebound or guarding. The Murphy sign is negative. Laboratory evaluation shows:

Total bilirubin: 2.1 mg/dL
Direct bilirubin: 1.5 mg/dL
Alkaline phosphatase: 250 U/L
Aspartate aminotransferase (AST): 110 U/L
Alanine aminotransferase (ALT): 125 U/L
Lipase: 45 U/L
Leukocyte count: 8,500/mm³

A right upper quadrant ultrasound demonstrates cholelithiasis without gallbladder wall thickening or pericholecystic fluid. The common bile duct measures 9 mm in diameter, but no stone is visualized within it. Which of the following is the most appropriate next step in the diagnostic workup of this patient?

Show answer & explanation

Answer: Magnetic resonance cholangiopancreatography

Answer

Magnetic resonance cholangiopancreatography is the most appropriate next step because the patient's presentation places her at intermediate risk for choledocholithiasis, requiring non-invasive confirmation.
The correct option is Magnetic resonance cholangiopancreatography (MRCP). The patient's presentation of biliary colic, a dilated common bile duct (CBD) of 9 mm, and elevated liver function tests suggests choledocholithiasis. However, because she does not have high-risk features (such as clinical ascending cholangitis, a directly visualized CBD stone on ultrasound, or a total bilirubin greater than 4.0 mg/dL), her risk is classified as intermediate (10-50%). For intermediate-risk patients, current guidelines recommend non-invasive evaluation of the biliary tree with MRCP or endoscopic ultrasound (EUS) to confirm the diagnosis before proceeding to invasive procedures.

Step-by-Step Solution

1
Evaluate the clinical, sonographic, and laboratory findings.
The patient has symptomatic cholelithiasis, a dilated common bile duct (9 mm), and mildly elevated liver function tests including bilirubin, but lacks ascending cholangitis or a bilirubin level over 4.0 mg/dL.
Accurate interpretation of these initial baseline investigations is necessary to stratify the patient's risk for a common bile duct stone.
2
Stratify the risk of choledocholithiasis according to established guidelines.
The combination of abnormal liver biochemistries and a dilated common bile duct (without high-risk predictors) categorizes the patient as having an intermediate probability (10% to 50%) of choledocholithiasis.
Risk stratification determines whether the patient should proceed directly to invasive therapeutic testing, non-invasive confirmatory imaging, or surgical intervention.
3
Select the guideline-indicated diagnostic test based on the risk category.
The correct test is a non-invasive confirmatory study, such as magnetic resonance cholangiopancreatography (MRCP) or endoscopic ultrasound (EUS).
This confirms the presence of a stone before subjecting an intermediate-risk patient to the procedural risks of an invasive procedure like ERCP.

Key Concept

Patients with an intermediate risk for choledocholithiasis (abnormal liver function tests and/or dilated common bile duct on ultrasound) should undergo non-invasive confirmatory testing with magnetic resonance cholangiopancreatography (MRCP) or endoscopic ultrasound (EUS) prior to invasive interventions.
Question 2938Question →

A 6868-year-old man presents to the clinic for follow-up of newly diagnosed atrial fibrillation. Three weeks ago, he presented to the emergency department with palpitations and was found to be in paroxysmal non-valvular atrial fibrillation. An echocardiogram demonstrated a structurally normal heart with a left ventricular ejection fraction of 60%60\%. He spontaneously converted to normal sinus rhythm and is currently asymptomatic. His past medical history is significant for hypertension, type 22 diabetes mellitus, and a seizure disorder secondary to a remote traumatic brain injury. His medications include lisinopril, metformin, and phenytoin. He has been seizure-free for the past 44 years on his current dose of phenytoin. Vital signs are within normal limits. Recent laboratory studies, including a basic metabolic panel and complete blood count, are unremarkable. Liver function tests reveal a mildly elevated total bilirubin of 1.41.4 mg/dL (normal: 0.10.1-1.21.2 mg/dL) with normal transaminases and alkaline phosphatase. His CHA 2_2 DS 2_2-VASc score is calculated to be 33. Which of the following is the most appropriate pharmacologic intervention for stroke prevention in this patient?

Show answer & explanation

Answer: Initiate warfarin therapy

Answer

The most appropriate pharmacologic intervention is to initiate warfarin therapy.
This patient requires oral anticoagulation for stroke prevention due to a CHA2DS2-VASc score of 3. However, he is well-controlled on phenytoin, a potent inducer of both the cytochrome P450 system (particularly CYP3A4) and P-glycoprotein (P-gp). Direct oral anticoagulants (DOACs) such as apixaban, rivaroxaban, and dabigatran are substrates for these metabolic and efflux pathways. Co-administration of DOACs with potent inducers results in drastically reduced plasma concentrations of the anticoagulant, placing the patient at high risk for ischemic stroke. Furthermore, because DOACs lack widely available, standardized laboratory assays for routine therapeutic monitoring, their dosages cannot be safely titrated to overcome the induction effect. In contrast, while warfarin metabolism is also affected by hepatic induction, its therapeutic biologic effect is directly measurable via the International Normalized Ratio (INR). Therefore, a clinician can safely initiate warfarin and empirically titrate the dosage upward until the target therapeutic INR (2.0 to 3.0) is achieved, ensuring adequate stroke prevention.

Step-by-Step Solution

1
Calculate the stroke risk and determine the indication for therapy.
The patient has a CHA2DS2-VASc score of 3, providing a strong indication for oral anticoagulation for stroke prevention.
Current clinical guidelines mandate oral anticoagulation for men with a score of 2 or higher.
2
Evaluate current medications for potential pharmacokinetic interactions.
The patient takes phenytoin, which is a potent inducer of hepatic cytochrome P450 enzymes (specifically CYP3A4) and the efflux transporter P-glycoprotein (P-gp).
Recognizing potent inducers or inhibitors is critical before prescribing new long-term pharmacotherapy.
3
Assess the metabolism and monitoring parameters of available oral anticoagulants.
Direct oral anticoagulants (DOACs) are substrates of CYP3A4 and P-gp, and lack standard laboratory tests for routine titration. Warfarin is metabolized hepatically but can be monitored via the INR.
DOACs will have unpredictably low and subtherapeutic plasma levels when given with phenytoin, increasing the risk of ischemic stroke.
4
Select the safest and most effective anticoagulant regimen.
Warfarin is selected because the dose can be empirically titrated up based on INR measurements to ensure therapeutic anticoagulation despite the presence of the enzyme inducer.
Direct monitoring of the biologic effect (INR) bypasses the pharmacokinetic unpredictability caused by the enzyme inducer.

Key Concept

Direct oral anticoagulants (DOACs) are contraindicated or strongly cautioned in patients taking potent CYP3A4 or P-glycoprotein inducers (such as phenytoin or carbamazepine) because induction significantly reduces DOAC levels and risks therapeutic failure. Warfarin is preferred because its dose can be empirically titrated using the International Normalized Ratio (INR).
Question 2939Question →

A 54-year-old man is evaluated in the intensive care unit for new-onset right lower extremity swelling and pain. He was admitted six days ago for an acute right-sided pulmonary embolism and was subsequently started on a continuous unfractionated heparin infusion. His initial recovery was uncomplicated. Today, physical examination reveals a swollen, erythematous, and tender right calf. His vital signs are temperature 37.1°C (98.8°F), blood pressure 128/82 mmHg, and heart rate 88/min.

Recent laboratory studies are as follows:

Laboratory TestResultReference Range
Hemoglobin13.2 g/dL13.5-17.5 g/dL (male)
Platelet count, today85,000/mm³150,000-400,000/mm³
Platelet count, admission260,000/mm³150,000-400,000/mm³
Serum creatinine1.0 mg/dL0.6-1.2 mg/dL

A lower extremity venous Doppler ultrasound confirms an acute occlusive deep vein thrombosis in the right popliteal vein. Which of the following is the most appropriate next step in the pharmacologic management of this patient?

Show answer & explanation

Answer: Discontinue unfractionated heparin and initiate an argatroban infusion

Answer

The most appropriate intervention is to discontinue the unfractionated heparin and initiate an argatroban infusion.
The clinical presentation is highly suggestive of Heparin-Induced Thrombocytopenia (HIT) Type 2. This condition is characterized by a platelet count drop of >50%, typically occurring 5-10 days after heparin initiation, and is paradoxically highly prothrombotic, often complicated by new events like a deep vein thrombosis. The standard of care requires the immediate cessation of all heparin products and the initiation of a non-heparin anticoagulant. Argatroban, a direct thrombin inhibitor, is an appropriate choice to provide immediate anticoagulation and prevent further thrombosis while the diagnosis is confirmed.

Step-by-Step Solution

1
Evaluate the patient's acute thrombocytopenia and new thrombosis in the context of recent medication exposure.
The timing (day 6 of therapy) and severity (>50% drop) of the thrombocytopenia, combined with a new thrombosis, yield a high 4T score strongly pointing to Heparin-Induced Thrombocytopenia (HIT) Type 2.
Calculating a 4T score is essential to estimate the pretest probability of HIT before taking interventional steps.
2
Determine the immediate pharmacologic intervention required for suspected HIT.
All heparin-containing products must be discontinued immediately without waiting for confirmatory laboratory testing.
Heparin-PF4 autoantibodies drive the pathogenesis, so removing the trigger is the critical first step in stabilization.
3
Select a safe alternative anticoagulant to treat the new deep vein thrombosis and underlying pulmonary embolism.
Initiate a non-heparin anticoagulant, such as a direct thrombin inhibitor (argatroban).
Patients with HIT are highly prothrombotic and require immediate alternative anticoagulation that does not cross-react with HIT autoantibodies.

Key Concept

Management of Heparin-Induced Thrombocytopenia (HIT)
Estimated Time:1m 30s
Question 2940Question →

A 58-year-old man is brought to the emergency department by emergency medical services due to severe, crushing substernal chest pain that began one hour ago while he was resting. The pain radiates to his left jaw and is associated with profound dizziness and diaphoresis. His medical history is significant for hypertension and type 2 diabetes mellitus. On arrival, he appears ashen and lethargic. Vital signs show a temperature of 36.6°C (97.9°F), blood pressure of 74/42 mmHg, heart rate of 112/min, respiratory rate of 20/min, and oxygen saturation of 95% on ambient air. Physical examination demonstrates prominent jugular venous distension, but pulmonary auscultation reveals clear lung fields bilaterally without crackles or wheezes. A rapid 12-lead electrocardiogram demonstrates 3-mm ST-segment elevations in leads II, III, and aVF, with reciprocal ST-segment depressions in leads I and aVL. Which of the following is the most appropriate initial step in the management of this patient?

Show answer & explanation

Answer: Administration of a rapid intravenous isotonic crystalloid bolus

Answer

The correct answer is the administration of a rapid intravenous isotonic crystalloid bolus to optimize right ventricular preload.
The patient's presentation of an inferior ST-elevation myocardial infarction (leads II, III, aVF) combined with profound hypotension, jugular venous distension, and clear lungs is highly specific for a right ventricular infarction. Because the ischemic right ventricle functions primarily as a passive conduit, it is highly dependent on adequate preload to push blood into the pulmonary circulation and subsequently fill the left ventricle. When profound hypotension is present, the immediate stabilizing intervention is to maximize right ventricular preload by administering a rapid intravenous isotonic crystalloid bolus.

Step-by-Step Solution

1
Analyze the clinical presentation and vital signs.
The patient is in cardiogenic shock (blood pressure 74/42 mmHg) with elevated jugular venous pressure but clear lung fields.
Identifying the triad of hypotension, elevated jugular venous pressure, and clear lungs is critical for diagnosing right ventricular failure.
2
Correlate the physical findings with the electrocardiogram results.
ST-segment elevations in inferior leads (II, III, aVF) suggest an inferior myocardial infarction, which involves the right ventricle in up to 50% of cases.
Inferior STEMIs are typically caused by right coronary artery occlusion, which also supplies the right ventricle.
3
Determine the physiological requirements for stabilization.
The ischemic right ventricle loses contractility and becomes highly dependent on venous return (preload) to pump blood to the left side of the heart.
Without adequate preload, left ventricular filling plummets, causing profound systemic hypotension.
4
Select the immediate intervention that addresses the hemodynamic instability.
Isotonic crystalloid boluses are required to increase right-sided filling pressures.
Hemodynamic stabilization (ABCs) must be initiated prior to confirmatory diagnostics (like a right-sided ECG) or definitive transfer (to the catheterization laboratory).

Key Concept

Patients with right ventricular myocardial infarction (inferior STEMI, clear lungs, hypotension, jugular venous distension) are highly preload-dependent; immediate stabilization requires intravenous crystalloid boluses to maintain cardiac output, and preload-reducing agents (nitrates, diuretics) must be avoided.
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