Internal Medicine

3151 questions

All types3,151 Multiple choice1,611 Multiple select73 Numeric81 Matching714 Ordering672

A 45-year-old patient is undergoing evaluation for secondary causes of hypertension and electrolyte abnormalities. The physician orders a plasma aldosterone concentration and plasma renin activity panel. Match the following laboratory profiles to their most likely underlying etiology.

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Answer

Elevated aldosterone/suppressed renin matches adrenal adenoma. Elevated aldosterone/elevated renin matches fibromuscular dysplasia. Suppressed aldosterone/suppressed renin matches licorice consumption. Suppressed aldosterone/elevated renin matches autoimmune adrenalitis.

Matching these conditions correctly requires analyzing the physiological feedback loop of the RAAS pathway. Autonomous mineralocorticoid activity (whether from an adenoma or an exogenous source like licorice) will always suppress renin. If the aldosterone itself is the source, aldosterone is high (primary hyperaldosteronism). If something else is acting at the mineralocorticoid receptor, both renin and aldosterone are suppressed (apparent mineralocorticoid excess). Conversely, if the system is driven by renal hypoperfusion, renin is high, driving aldosterone high. If the adrenal gland fails, aldosterone is low, leaving renin unsuppressed and highly elevated.

Step-by-Step Solution

Determine if the aldosterone and renin levels are moving in the same or opposite directions.

Opposite directions suggest a primary adrenal issue; same directions suggest a secondary (renin-driven) or exogenous issue.

This establishes whether the pathology originates in the adrenal gland or upstream in the RAAS pathway.

Evaluate the 'Elevated aldosterone, suppressed renin' profile.

Matches Primary Hyperaldosteronism (Aldosterone-producing adrenal adenoma).

Autonomous production of aldosterone causes negative feedback on renin.

Evaluate the 'Elevated aldosterone, elevated renin' profile.

Matches Secondary Hyperaldosteronism (Unilateral renal artery fibromuscular dysplasia).

Primary increase in renin (due to perceived renal hypoperfusion) drives the elevation in aldosterone.

Evaluate the 'Suppressed aldosterone, suppressed renin, hypokalemia' profile.

Matches Apparent Mineralocorticoid Excess (Chronic consumption of authentic licorice).

An alternative mineralocorticoid source (cortisol bypassing degraded 11b-HSD2) suppresses both native renin and aldosterone while still causing hypokalemia.

Evaluate the 'Suppressed aldosterone, elevated renin, hyperkalemia' profile.

Matches Primary Adrenal Insufficiency (Autoimmune adrenalitis).

Primary failure of the adrenal gland eliminates aldosterone, removing negative feedback and causing profound renin elevation due to volume depletion.

Key Concept

Interpretation of Renin-Angiotensin-Aldosterone System (RAAS) laboratory profiles

Question 2182Question →

A 62-year-old man with a 15-year history of poorly controlled type 2 diabetes mellitus and peripheral neuropathy is evaluated in the clinic for a chronic right foot ulcer. He first noticed the ulcer 6 weeks ago. The patient is afebrile, and his vital signs are strictly within normal limits. On physical examination, there is a $3 \times 3$ cm non-tender ulcer on the plantar surface of the right first metatarsal head. There is no surrounding erythema, warmth, fluctuance, or purulent drainage. A sterile metal probe is introduced into the ulcer and easily palpates a hard, gritty surface at the base. The physician highly suspects underlying osteomyelitis.

Arrange the following diagnostic and therapeutic steps in the most appropriate chronological sequence for the standard medical management of this patient.

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Answer

The correct sequence is to first perform plain radiography, followed by MRI of the foot, then obtain a bone biopsy off antibiotics, and finally initiate targeted antimicrobial therapy.

In a clinically stable, afebrile patient with a chronic diabetic foot ulcer and positive probe-to-bone testing, the management sequence prioritizes accurate diagnosis and pathogen identification over immediate medical therapy. Plain radiography is the mandatory initial test. Because it may lack sensitivity in early or indolent disease, MRI follows to confirm the diagnosis and delineate the anatomical extent. Subsequently, a bone biopsy is required as the gold standard for diagnosis. Critically, in patients without systemic signs of sepsis or severe acute cellulitis, empiric broad-spectrum antibiotics should be strictly withheld until the bone biopsy is obtained. Once cultures confirm the organism, prolonged, targeted systemic antimicrobial therapy can be initiated.

Step-by-Step Solution

Perform plain radiography of the affected foot.

Evaluates the foot for baseline gross bony changes, cortical destruction, soft tissue gas, or radiopaque foreign bodies.

Due to its wide availability and low cost, plain radiography is always the initial imaging test of choice for suspected osteomyelitis, even though it may appear normal during the first 2 weeks of infection.

Perform magnetic resonance imaging (MRI) of the foot.

Identifies early bone marrow edema and defines the exact anatomical extent of the infection.

MRI is the most sensitive and specific imaging test for osteomyelitis. It maps the infection to guide the subsequent surgical or percutaneous biopsy site.

Obtain a bone biopsy for microbiological culture.

Yields a definitive microbiologic diagnosis and histopathologic confirmation of osteomyelitis.

Because diabetic foot infections are often polymicrobial, a bone culture is the gold standard. In hemodynamically stable patients without severe acute cellulitis, this must be done BEFORE giving antibiotics to maximize culture yield.

Initiate targeted systemic antimicrobial therapy.

Treats the infection using narrow-spectrum agents proven to be effective against the isolated organism.

Chronic osteomyelitis requires a prolonged course of antibiotics (typically 6 weeks). Therapy should be strictly tailored to biopsy susceptibilities to ensure efficacy and promote antibiotic stewardship.

Key Concept

In hemodynamically stable patients with chronic diabetic foot osteomyelitis, empiric antibiotics must be withheld until after imaging and a definitive bone biopsy are obtained to ensure accurate microbiologic diagnosis.

Alternative Method

In cases where MRI is contraindicated (e.g., incompatible pacemakers), a Ceretec (WBC) scan combined with a bone scan may be used as the alternative advanced imaging step before biopsy.

Estimated Time:2m 0s

Question 2183Question →

Match each brief clinical presentation to the most appropriate initial or highly specific diagnostic serologic marker.

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Answer

Match the 45-year-old woman (PBC) with AMA, the 32-year-old man with ulcerative colitis (PSC) with p-ANCA, the 28-year-old woman with marked transaminitis (Autoimmune Hepatitis) with ASMA, and the 35-year-old man with chronic diarrhea and vesicular rash (Celiac Disease) with Anti-tTG IgA.

Each clinical presentation is a classic description of a specific autoimmune gastrointestinal or hepatobiliary disorder, each of which has a highly characteristic autoantibody used for diagnosis.

Step-by-Step Solution

Analyze the first presentation.

Identified as Primary Biliary Cholangitis (PBC) due to the middle-aged female demographic, pruritus, fatigue, and cholestatic liver injury.

PBC is an autoimmune destruction of intrahepatic bile ducts, classically marked by Anti-mitochondrial antibodies (AMA).

Analyze the second presentation.

Identified as Primary Sclerosing Cholangitis (PSC) based on the association with ulcerative colitis and stricturing of biliary ducts.

PSC is heavily linked to inflammatory bowel disease and often shows a positive p-ANCA, unlike PBC.

Analyze the third presentation.

Identified as Autoimmune Hepatitis (AIH) type 1 given the severe hepatocellular injury (high AST/ALT) and hypergammaglobulinemia in a young woman.

AIH type 1 is characterized by the presence of Anti-smooth muscle antibodies (ASMA) and/or Antinuclear antibodies (ANA).

Analyze the fourth presentation.

Identified as Celiac disease with Dermatitis Herpetiformis based on malabsorption and the classic extensor surface vesicular rash.

The highly specific serologic test for Celiac disease is the Anti-tissue transglutaminase IgA antibody (Anti-tTG IgA).

Key Concept

Diagnostic serologies for autoimmune gastrointestinal and hepatobiliary diseases

Estimated Time:1m 30s

Question 2184Question →

A 34-year-old woman is brought to the emergency department for severe, progressive mid-abdominal pain and bilious emesis over the past 24 hours. She has not passed flatus or stool since the pain began. Her medical history includes Crohn disease, which necessitated a terminal ileal resection 7 years ago due to fibrotic strictures. She also has a history of mild asthma and a peripartum cardiomyopathy 3 years ago that has since completely resolved. Current medications include adalimumab. Her temperature is 38.9°C (102.0°F), blood pressure is 88/54 mm Hg, and pulse is 126/min. On physical examination, the abdomen is markedly distended and tympanic. There is severe, diffuse abdominal tenderness with involuntary guarding and rebound tenderness. Bowel sounds are absent.

Laboratory studies show:

Laboratory Test	Result
Leukocyte count	19,500/mm³
Serum sodium	138 mEq/L
Serum potassium	3.9 mEq/L
Serum chloride	102 mEq/L
Serum bicarbonate	14 mEq/L
Lactic acid	4.8 mmol/L

Arterial blood gas analysis on room air:

Test	Result
pH	7.28
PaCO2	28 mm Hg
PaO2	92 mm Hg

Which of the following is the most appropriate next step in the management of this patient?

Placement of a nasogastric tube and serial abdominal examinations

Computed tomography scan of the abdomen and pelvis

Intravenous administration of sodium bicarbonate

Urgent surgical exploration

Administration of intravenous furosemide

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Answer: Urgent surgical exploration

Answer

The most appropriate next step is urgent surgical exploration due to signs of a strangulated small bowel obstruction.

The correct answer is urgent surgical exploration. This patient presents with the classic triad of a small bowel obstruction (SBO): colicky abdominal pain, bilious vomiting, and obstipation, likely due to adhesions from her prior surgery or a new Crohn disease stricture. Crucially, she exhibits signs of a strangulated obstruction, including peritonitis (involuntary guarding, rebound tenderness), hemodynamic instability (hypotension, tachycardia), systemic inflammatory response (fever, marked leukocytosis), and bowel ischemia (lactic acidosis causing a high anion gap metabolic acidosis). In any patient with an acute surgical abdomen and hemodynamic instability, emergent laparotomy is the definitive and life-saving next step.

Step-by-Step Solution

Assess the patient's hemodynamic status and physical examination findings.

The patient is hypotensive and tachycardic with fever, and has diffuse abdominal rigidity and rebound tenderness indicating peritonitis.

To determine if the patient has an acute surgical abdomen requiring immediate operative intervention rather than conservative management.

Evaluate the laboratory results and calculate the anion gap and expected respiratory compensation.

The anion gap is elevated at 22 (

138 - (102 + 14)

), driven by lactic acidosis (4.8 mmol/L). Using Winter's formula (

PaCO_2 = 1.5 \times 14 + 8 = 29 \pm 2

), the patient's

PaCO_2

of 28 mm Hg indicates a perfectly compensated metabolic acidosis with no primary respiratory disorder.

To identify the presence of bowel ischemia (lactic acidosis) and to rule out any concurrent primary respiratory failure that might mandate primary airway management over immediate surgery.

Synthesize the history of Crohn disease and prior abdominal surgery with current findings.

The clinical picture confirms a strangulated small bowel obstruction (SBO) likely secondary to adhesions or stricture.

To select the definitive management pathway, which dictates that strangulated SBO in an unstable patient bypasses advanced imaging directly for surgical exploration.

Key Concept

Patients with small bowel obstruction presenting with signs of ischemia or strangulation (peritonitis, fever, lactic acidosis, hemodynamic instability) require immediate surgical exploration.

Question 2185Question →

A 24-year-old woman is brought to the emergency department due to severe nausea, diffuse abdominal pain, and confusion. She has a history of type 1 diabetes mellitus but ran out of her insulin prescription three days ago. For the past 48 hours, she has had intractable vomiting, rendering her unable to tolerate oral intake. Her temperature is 37.1°C (98.8°F), blood pressure is 98/60 mm Hg, pulse is 118/min, and respirations are 24/min and deep. Physical examination reveals dry mucous membranes, decreased skin turgor, and diffuse abdominal tenderness without rebound or guarding.

Laboratory studies reveal:

Serum chemistry	Value
Sodium	140 mEq/L
Potassium	3.2 mEq/L
Chloride	94 mEq/L
Bicarbonate	16 mEq/L
Blood urea nitrogen	32 mg/dL
Creatinine	1.4 mg/dL
Glucose	480 mg/dL

Arterial blood gas (room air):

Parameter	Value
pH	7.33
pCO2	32 mm Hg
pO2	92 mm Hg

Which of the following best describes this patient's current acid-base disturbance?

Anion gap metabolic acidosis and concurrent metabolic alkalosis

Isolated anion gap metabolic acidosis with appropriate respiratory compensation

Anion gap metabolic acidosis and concurrent respiratory acidosis

Anion gap metabolic acidosis and concurrent respiratory alkalosis

Non-anion gap metabolic acidosis and concurrent metabolic alkalosis

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Answer: Anion gap metabolic acidosis and concurrent metabolic alkalosis

Answer

Anion gap metabolic acidosis and concurrent metabolic alkalosis

This patient has a mixed acid-base disorder comprising an anion gap metabolic acidosis (AGMA) and a metabolic alkalosis, with appropriate respiratory compensation. First, the pH of 7.33 and low bicarbonate (16 mEq/L) indicate a primary metabolic acidosis. Next, calculating the anion gap (

\text{AG} = \text{Na}^+ - (\text{Cl}^- + \text{HCO}_3^-)

) yields

140 - (94 + 16) = 30

mEq/L, indicating a severe AGMA, consistent with diabetic ketoacidosis. To determine if a secondary metabolic disorder is present, the delta gap must be analyzed. The anion gap increased by 18 (

30 - 12

), so the bicarbonate should drop by exactly 18 to 6 mEq/L (

24 - 18 = 6

). However, the patient's actual bicarbonate is 16 mEq/L. Because the actual bicarbonate is significantly higher than the predicted bicarbonate, there is a concurrent metabolic alkalosis, likely secondary to her intractable vomiting (loss of gastric HCl). Finally, Winter's formula (

\text{pCO}_2 = 1.5 \times \text{HCO}_3^- + 8 \pm 2

) yields an expected

\text{pCO}_2

1.5 \times 16 + 8 = 32

mm Hg. Because the measured

\text{pCO}_2

is exactly 32 mm Hg, respiratory compensation is appropriate and there is no concurrent respiratory disorder.

Step-by-Step Solution

Determine the primary disturbance from the pH and bicarbonate.

The patient has acidemia (pH 7.33) with a low bicarbonate (16 mEq/L), indicating a primary metabolic acidosis.

Identifying the primary disorder provides the baseline for further acid-base calculations.

Calculate the anion gap (AG).

\text{AG} = \text{Na}^+ - (\text{Cl}^- + \text{HCO}_3^-) = 140 - (94 + 16) = 30

mEq/L.

A significantly elevated AG (> 12 mEq/L) confirms an anion gap metabolic acidosis, typical of diabetic ketoacidosis.

Check respiratory compensation using Winter's formula.

Expected

\text{pCO}_2 = 1.5 \times 16 + 8 = 32

mm Hg. The actual

\text{pCO}_2

is 32 mm Hg.

Because the actual

\text{pCO}_2

falls exactly within the expected range, there is appropriate respiratory compensation without a concurrent primary respiratory disorder.

Calculate the delta gap to identify hidden metabolic disorders.

\Delta\text{AG} = 30 - 12 = 18

. Expected

\text{HCO}_3^- = 24 - 18 = 6

mEq/L. Actual

\text{HCO}_3^-

is 16 mEq/L.

Because the actual bicarbonate (16) is greater than the expected bicarbonate (6), a concurrent metabolic alkalosis is present, consistent with her history of intractable vomiting.

Key Concept

In complex patients (e.g., DKA with vomiting), evaluating the delta gap (or delta ratio) is required after calculating the anion gap to unmask hidden concurrent metabolic disorders.

Alternative Method

Instead of subtracting the delta gap from a normal bicarbonate, you can calculate the delta ratio (

\frac{\Delta\text{AG}}{\Delta\text{HCO}_3^-}

). A ratio between 1.0 and 2.0 indicates an isolated anion gap metabolic acidosis, while a ratio > 2.0 indicates a concurrent metabolic alkalosis. Here, the ratio is

\frac{18}{8} = 2.25

, confirming the concurrent metabolic alkalosis.

Estimated Time:2m 0s

Question 2186Question →

A 58-year-old man is brought to the emergency department by his wife due to fever, severe headache, and confusion that started 12 hours ago. His wife reports that he has also been dragging his right leg since the onset of symptoms. His temperature is 39.2°C (102.6°F), blood pressure is 145/90 mm Hg, and pulse is 110/min. Physical examination reveals marked nuchal rigidity and right-sided hemiparesis. He is lethargic but arouses to verbal stimuli. Arrange the following management steps in the most appropriate chronological order.

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Answer

The correct chronological sequence is: obtain blood cultures, administer intravenous dexamethasone and empiric antibiotics, perform a non-contrast CT scan of the head, and perform a lumbar puncture.

In a patient with suspected bacterial meningitis and focal neurologic deficits (hemiparesis), a CT scan of the head is required before a lumbar puncture to avoid brain herniation. Because these procedures take time, life-saving therapy cannot be delayed. Therefore, blood cultures must be drawn immediately, followed promptly by empiric antibiotics and dexamethasone. Once therapy is initiated, the CT scan is performed, and if it is safe, the lumbar puncture is conducted.

Step-by-Step Solution

Identify indications for neuroimaging prior to lumbar puncture.

The patient's right-sided hemiparesis is identified as a focal neurologic deficit.

Focal deficits, altered mental status, papilledema, new-onset seizures, or an immunocompromised state require a CT scan before a lumbar puncture to rule out mass effect and prevent brain herniation.

Determine the first step in managing suspected bacteremia or meningitis.

Blood cultures must be drawn immediately.

Drawing blood cultures before antibiotic administration ensures the best chance of isolating the pathogen, and this step does not significantly delay life-saving therapy.

Determine the timing of empiric antimicrobial therapy.

Intravenous dexamethasone and empiric antibiotics are administered next.

When a CT scan is required, therapy cannot be delayed until after the imaging and lumbar puncture are completed. Dexamethasone must be given with or just before the antibiotics.

Sequence the remaining diagnostic procedures.

Perform the CT scan of the head, followed by the lumbar puncture.

The CT scan must confirm safety before the lumbar puncture is performed to obtain cerebrospinal fluid for definitive diagnosis.

Key Concept

Management sequence for suspected bacterial meningitis with indications for a head CT before lumbar puncture.

Question 2187Question →

Paramedics bring a 64-year-old woman to the emergency department due to acute respiratory distress that began 2 hours ago. She reports severe difficulty breathing and the sensation of smothering, which worsens significantly when she tries to lie flat on the stretcher. Her medical history includes long-standing hypertension, diet-controlled type 2 diabetes mellitus, and a 30-pack-year history of cigarette smoking. Upon arrival, her blood pressure is 182/104 mmHg, heart rate is 112/min, and respiratory rate is 26/min. Pulse oximetry shows an oxygen saturation of 88% on room air. Physical examination reveals an anxious patient sitting upright and utilizing accessory muscles of respiration. Jugular venous pressure is visibly elevated. Pulmonary auscultation reveals bilateral basilar crackles and prominent diffuse expiratory wheezing. Cardiac auscultation is notable for a regular tachycardia and an audible S3 gallop. In addition to providing supplemental oxygen, which of the following is the most appropriate initial pharmacological intervention for this patient?

Intravenous bolus of a loop diuretic

Inhaled short-acting bronchodilator therapy

Intravenous administration of a systemic glucocorticoid

Empiric therapy with broad-spectrum antibiotics

Continuous intravenous infusion of unfractionated heparin

Show answer & explanation

Answer: Intravenous bolus of a loop diuretic

Answer

Intravenous bolus of a loop diuretic

The correct answer is an intravenous bolus of a loop diuretic. This patient presents with classic signs of acute decompensated heart failure (ADHF) with pulmonary edema, indicated by severe dyspnea, orthopnea, elevated jugular venous pressure, basilar crackles, and an S3 gallop. The severe hypertension suggests an acute afterload elevation precipitating the failure. The prominent wheezing is due to peribronchial edema compressing the airways, a phenomenon referred to as 'cardiac asthma.' The presence of a smoking history combined with wheezing can tempt a misdiagnosis of a COPD exacerbation; however, COPD does not cause a third heart sound (S3) or elevated left-sided filling pressures resulting in rapid-onset orthopnea and bilateral pulmonary crackles. The immediate management of ADHF requires aggressive preload and afterload reduction. Intravenous loop diuretics are the cornerstone of initial therapy because they induce rapid venodilation (decreasing preload even before diuresis begins) and subsequent diuresis to clear the pulmonary edema.

Step-by-Step Solution

Analyze the patient's vital signs and physical examination findings.

The patient has severe hypertension, tachycardia, hypoxia, orthopnea, elevated jugular venous pressure, bilateral crackles, wheezing, and an S3 gallop.

Identifying these clinical signs is necessary to determine the primary etiology of the acute respiratory distress.

Synthesize the findings to formulate a primary diagnosis.

The combination of elevated filling pressures (JVP, S3 gallop) and pulmonary edema (crackles, orthopnea) strongly indicates acute decompensated heart failure (ADHF). The wheezing is due to peribronchial edema, known as cardiac asthma.

Distinguishing ADHF from a primary pulmonary process like a COPD exacerbation guides the immediate management strategy.

Select the most appropriate initial pharmacological therapy for the primary diagnosis.

Intravenous loop diuretics are indicated to provide rapid symptomatic relief by reducing intravascular volume and decreasing pulmonary venous pressure.

Loop diuretics are the standard initial pharmacologic therapy for volume overload in ADHF.

Key Concept

Patients with acute decompensated heart failure can present with prominent wheezing (cardiac asthma) due to peribronchial edema. The presence of an S3 gallop, elevated jugular venous pressure, and rapid-onset orthopnea help clinically differentiate this from a COPD exacerbation.

Question 2188Question →

Match each patient's clinical presentation and multiphasic abdominal imaging findings with the most likely primary hepatic lesion.

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Answer

Hepatocellular carcinoma presents with arterial hyperenhancement and rapid washout. Hepatic cavernous hemangioma shows peripheral nodular enhancement with centripetal fill-in. Focal nodular hyperplasia features an arterially enhancing mass with a delayed-enhancing central scar. Hepatic adenoma is a hypervascular mass lacking a scar, associated with oral contraceptives. Intrahepatic cholangiocarcinoma exhibits rim enhancement, delayed central fill-in, and characteristic capsular retraction.

The diagnostic evaluation of focal liver lesions depends heavily on characterizing their blood supply through multiphasic contrast imaging. Hepatocellular carcinoma receives its blood exclusively from the hepatic artery, leading to early arterial enhancement, whereas the surrounding parenchyma is supplied by the portal vein, resulting in rapid washout. Hepatic cavernous hemangiomas are slow-flow vascular spaces that fill from the periphery to the center over time. Focal nodular hyperplasia represents a hyperplastic response to an aberrant artery; it enhances intensely in the arterial phase but contains a central fibrotic scar that typically retains contrast on delayed imaging. Hepatic adenomas are benign epithelial tumors strongly associated with oral contraceptive use; they show arterial enhancement but lack the central scar. Intrahepatic cholangiocarcinomas are highly desmoplastic, causing rim-like arterial enhancement, delayed central fill-in due to the dense stroma, and characteristic retraction of the overlying liver capsule.

Step-by-Step Solution

Analyze the first presentation (65-year-old with cirrhosis, arterial hyperenhancement, rapid washout).

Matches Hepatocellular carcinoma.

HCC derives its blood supply exclusively from the hepatic artery, causing early enhancement, while the surrounding cirrhotic liver is supplied by the portal vein, resulting in characteristic rapid washout.

Analyze the second presentation (40-year-old asymptomatic woman, peripheral nodular enhancement, centripetal fill-in).

Matches Hepatic cavernous hemangioma.

Hemangiomas are slow-flow vascular malformations that fill slowly from the periphery toward the center over time.

Analyze the third presentation (32-year-old healthy woman, homogeneous arterial enhancement, delayed-enhancing central scar).

Matches Focal nodular hyperplasia.

FNH is a hyperplastic response to an anomalous artery. The central fibrotic scar contains slow-flowing vessels that retain contrast on delayed venous imaging.

Analyze the fourth presentation (28-year-old woman on OCPs, homogeneous arterial enhancement, no scar).

Matches Hepatic adenoma.

Adenomas are benign, hypervascular epithelial tumors strongly linked to OCP use. They lack the central scar seen in FNH and carry risks of hemorrhage and malignant transformation.

Analyze the fifth presentation (70-year-old man, weight loss, rim enhancement, capsular retraction).

Matches Intrahepatic cholangiocarcinoma.

Cholangiocarcinomas are highly desmoplastic tumors. The dense fibrosis causes progressive delayed central enhancement and retracts the overlying liver capsule.

Key Concept

Diagnosis of focal liver lesions using multiphasic contrast-enhanced imaging.

Question 2189Question →

A 29-year-old woman is evaluated in the clinic as a new patient. She has no complaints and reports feeling well. She exercises regularly, follows a balanced diet, and takes no medications or supplements. Her father has a history of asymptomatic hypercalcemia that has never required medical treatment. Vital signs are within normal limits. Physical examination is unremarkable.

Laboratory studies show:

Test	Result	Reference Range
Serum calcium	$11.2$ mg/dL	$8.4-10.2$ mg/dL
Serum albumin	$4.1$ g/dL	$3.5-5.0$ g/dL
Serum phosphorus	$2.3$ mg/dL	$2.5-4.5$ mg/dL
Serum creatinine	$0.8$ mg/dL	$0.6-1.1$ mg/dL
Intact parathyroid hormone	$68$ pg/mL	$10-65$ pg/mL

A 24-hour urine collection yields:

Test	Result	Reference Range
Urine calcium	$65$ mg/24 hr	$100-300$ mg/24 hr
Urine creatinine	$1000$ mg/24 hr	$800-1500$ mg/24 hr

Which of the following is the most appropriate next step in management?

Reassurance and clinical observation

Referral for parathyroidectomy

Sestamibi parathyroid scintigraphy

Dual-energy x-ray absorptiometry

Measurement of serum 1,25-dihydroxyvitamin D

Show answer & explanation

Answer: Reassurance and clinical observation

Answer

Reassurance and clinical observation

The correct approach is reassurance and clinical observation. This patient presents with asymptomatic hypercalcemia and an intact parathyroid hormone (PTH) level that is mildly elevated, indicating a PTH-dependent etiology. The critical distinguishing factor is the very low 24-hour urine calcium (

65

mg/24 hr) in the setting of hypercalcemia.

To formally differentiate between the two most likely causes—primary hyperparathyroidism and familial hypocalciuric hypercalcemia (FHH)—the calcium-creatinine clearance ratio (CCCR) must be calculated:

CCCR = \frac{\text{Urine Ca} \times \text{Serum Cr}}{\text{Serum Ca} \times \text{Urine Cr}}

CCCR = \frac{65 \times 0.8}{11.2 \times 1000} = \frac{52}{11200} \approx 0.0046

A CCCR of

< 0.01

is highly sensitive and specific for FHH, whereas primary hyperparathyroidism typically yields a CCCR

> 0.02

. Furthermore, the patient's family history of asymptomatic, untreated hypercalcemia strongly supports this autosomal dominant condition. FHH is caused by an inactivating mutation of the calcium-sensing receptor (CaSR) in the parathyroid glands and kidneys, requiring higher calcium levels to suppress PTH and increasing renal calcium reabsorption. It is a benign condition that does not cause progressive bone loss or renal stones; therefore, medical or surgical interventions are not indicated, and the best step is reassurance.

Step-by-Step Solution

Analyze the serum laboratory findings to determine the category of hypercalcemia.

The patient has hypercalcemia (

11.2

mg/dL) with an inappropriately high-normal/mildly elevated intact PTH (

68

pg/mL).

Elevated or high-normal PTH in the setting of hypercalcemia indicates a PTH-dependent process, narrowing the differential diagnosis primarily to primary hyperparathyroidism and familial hypocalciuric hypercalcemia (FHH).

Calculate the calcium-creatinine clearance ratio (CCCR) using the 24-hour urine data to differentiate between primary hyperparathyroidism and FHH.

The CCCR is calculated as:

CCCR = \frac{\text{Urine Ca} \times \text{Serum Cr}}{\text{Serum Ca} \times \text{Urine Cr}}

. Here,

(65 \times 0.8) / (11.2 \times 1000) = 52 / 11200 \approx 0.0046

A CCCR

< 0.01

is highly suggestive of FHH, whereas primary hyperparathyroidism typically presents with a CCCR

> 0.02

Determine the appropriate management for the diagnosed condition.

The patient is diagnosed with FHH. The most appropriate next step is reassurance and clinical observation.

FHH is a benign, asymptomatic condition caused by an inactivating mutation in the calcium-sensing receptor (CaSR). It does not lead to end-organ damage, and parathyroidectomy is neither curative nor indicated.

Key Concept

Familial hypocalciuric hypercalcemia (FHH) presents with PTH-dependent hypercalcemia but is distinguished from primary hyperparathyroidism by a very low 24-hour urine calcium and a calcium-creatinine clearance ratio (CCCR) of

< 0.01

. It is a benign condition that requires only reassurance and observation.

Question 2190Question →

A 74-year-old woman is evaluated in the intensive care unit for rapidly worsening abdominal distension and shock. She was admitted 10 days ago for community-acquired pneumonia and was treated with a 5-day course of intravenous ceftriaxone and azithromycin. Four days ago, she developed profuse, watery diarrhea and tested positive for *Clostridioides difficile* toxin. She was started on oral vancomycin therapy.

Over the past 12 hours, her diarrhea abruptly ceased, but she became increasingly lethargic and her abdomen became massively distended. She is now mechanically ventilated due to encephalopathy and shock. Her son, who is her legally appointed healthcare proxy, is at the bedside. The patient has a living will from five years ago stating she would refuse major surgery. However, her son states, "Right before she was intubated today, she explicitly told me to authorize any surgery necessary to survive this."

Temperature is 39.4°C (102.9°F), blood pressure is 78/45 mmHg (while receiving a high-dose norepinephrine infusion), and pulse is 132/min. The abdomen is tympanitic, markedly distended, and rigid, with diffuse rebound tenderness. Bowel sounds are absent.

Laboratory results:
Leukocytes: $45,000 / \text{mm}^3$ (25% band forms)
Serum lactate: $6.8 \text{ mmol/L}$
Arterial blood gas:
pH: $7.18$
pCO $_2$ : $25 \text{ mmHg}$
HCO $_3^-$ : $9 \text{ mEq/L}$

Abdominal radiograph reveals a transverse colon diameter of 11 cm with mucosal edema and loss of haustral markings. No free intraperitoneal air is visible.

Which of the following is the most appropriate next step in management?

Subtotal colectomy with end ileostomy

Administration of high-dose nasogastric vancomycin, intravenous metronidazole, and vancomycin retention enemas

Escalation of antimicrobial therapy to intravenous meropenem, vancomycin, and anidulafungin

Transition to comfort-focused care in accordance with the documented living will

Urgent colonoscopic decompression of the dilated transverse colon

Show answer & explanation

Answer: Subtotal colectomy with end ileostomy

Answer

Subtotal colectomy with end ileostomy

This patient has fulminant Clostridioides difficile colitis complicated by toxic megacolon (transverse colon > 6 cm, abrupt cessation of diarrhea, rigid abdomen) and refractory septic shock. While maximal medical management (enteral vancomycin and intravenous metronidazole) is the initial therapy for severe C. difficile, this patient exhibits absolute indications for emergent surgery: hemodynamic instability requiring vasopressors, severe lactic acidosis (lactate > 5 mmol/L), marked leukocytosis (> 35,000/mm³), and peritonitis. The standard surgical procedure of choice is a subtotal colectomy with end ileostomy, which provides source control and is life-saving. Furthermore, the son's authorization for surgery is legally and ethically valid; recent, specific verbal wishes expressed to a legally appointed proxy supersede older written advance directives.

Step-by-Step Solution

Diagnose the complication

Fulminant Clostridioides difficile colitis with toxic megacolon

Patient presents with cessation of diarrhea, massive colonic dilation (>6 cm), extreme leukocytosis, and shock after initial C. difficile diagnosis.

Assess clinical stability and surgical indications

Patient requires emergent surgery

Presence of peritonitis (rigid abdomen), refractory shock on vasopressors, and severe lactic acidosis (lactate > 5 mmol/L) indicate impending perforation and medical failure.

Evaluate the ethical constraint regarding the patient's living will

Surgery is ethically and legally authorized

Recent, specific verbal wishes expressed by a competent patient to their legally appointed proxy supersede older, conflicting written advance directives.

Select the definitive intervention

Subtotal colectomy with end ileostomy

This is the standard-of-care life-saving surgical procedure for toxic megacolon secondary to fulminant C. difficile colitis.

Key Concept

Surgical indications for fulminant C. difficile colitis (Toxic Megacolon)

Estimated Time:1m 30s

Question 2191Question →

A 68-year-old man is evaluated in the intensive care unit on his fifth day of mechanical ventilation. He originally presented with severe acute pancreatitis complicated by acute respiratory distress syndrome. Three days ago, he developed a temperature of $39.2^\circ\text{C}$ ( $102.6^\circ\text{F}$ ), increased purulent endotracheal secretions, and a new right lower lobe infiltrate on chest radiograph. He was diagnosed with ventilator-associated pneumonia and empirically started on intravenous vancomycin, cefepime, and tobramycin. Today, his temperature is $37.4^\circ\text{C}$ ( $99.3^\circ\text{F}$ ), and his oxygen requirements have decreased. The endotracheal aspirate culture from three days ago grows heavy growth ( $>10^5\text{ CFU/mL}$ ) of *Klebsiella pneumoniae*. Susceptibility testing reveals resistance to ampicillin, but susceptibility to ceftriaxone, cefepime, piperacillin-tazobactam, and meropenem. Blood cultures are negative. Which of the following is the most appropriate next step in this patient's antimicrobial management?

Discontinue vancomycin and tobramycin; change cefepime to intravenous ceftriaxone

Discontinue vancomycin and tobramycin; continue intravenous cefepime

Discontinue vancomycin and tobramycin; change cefepime to intravenous piperacillin-tazobactam

Discontinue vancomycin and tobramycin; change cefepime to intravenous meropenem

Continue intravenous vancomycin, cefepime, and tobramycin without modifications

Show answer & explanation

Answer: Discontinue vancomycin and tobramycin; change cefepime to intravenous ceftriaxone

Answer

The most appropriate step is to discontinue vancomycin and tobramycin, and change cefepime to intravenous ceftriaxone.

The correct answer demonstrates proper antimicrobial stewardship through de-escalation. The patient was appropriately started on a broad-spectrum empiric regimen (vancomycin for MRSA, cefepime and tobramycin for double anti-pseudomonal coverage) for ventilator-associated pneumonia. Now that the patient is clinically improving and culture data reveals a single pathogen (*Klebsiella pneumoniae*) that is susceptible to standard beta-lactams, the empiric regimen must be narrowed. Vancomycin and tobramycin should be discontinued because neither MRSA nor *Pseudomonas aeruginosa* was isolated. Among the susceptible beta-lactams, ceftriaxone is a third-generation cephalosporin with excellent activity against wild-type *Klebsiella pneumoniae* but lacks anti-pseudomonal activity. It is the narrowest effective agent listed. Transitioning from cefepime (a fourth-generation cephalosporin with anti-pseudomonal activity) to ceftriaxone is the optimal stewardship intervention.

Step-by-Step Solution

Evaluate the clinical trajectory and need for continued empiric therapy.

The patient's fever has resolved and oxygenation has improved, indicating clinical stability and appropriateness for antimicrobial de-escalation.

De-escalation should be performed once a patient is clinically improving and culture data becomes available.

Interpret the culture and susceptibility results.

The pathogen is Klebsiella pneumoniae, susceptible to multiple beta-lactams but not ampicillin. There is no MRSA or Pseudomonas aeruginosa present.

Identifying the specific pathogen allows for discontinuation of agents covering organisms not present in the culture.

Apply principles of antimicrobial stewardship to select definitive therapy.

Vancomycin (MRSA coverage) and tobramycin (double Gram-negative/Pseudomonal coverage) must be stopped. Cefepime must be narrowed.

Maintaining unnecessary broad-spectrum agents increases the risk of adverse effects and antimicrobial resistance.

Select the narrowest effective agent for the identified organism.

Ceftriaxone is chosen over cefepime, piperacillin-tazobactam, and meropenem.

Ceftriaxone provides targeted therapy for wild-type Klebsiella pneumoniae without exerting selective pressure for Pseudomonas or anaerobic resistance.

Key Concept

Antimicrobial stewardship dictates that empiric broad-spectrum therapy for hospital-acquired infections should be narrowed to the most targeted, definitive agent once culture and susceptibility data are available and clinical improvement is noted.

Estimated Time:2m 0s

Question 2192Question →

Match the following clinical and laboratory profiles of patients presenting with suspected hypercortisolism to their most likely underlying etiology.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Profile 1 matches Pituitary ACTH-secreting adenoma; Profile 2 matches Ectopic ACTH secretion; Profile 3 matches Primary adrenal adenoma; Profile 4 matches Exogenous synthetic glucocorticoid use; Profile 5 matches Physiologic hypercortisolism.

The correct matches follow the standard endocrine diagnostic algorithm for hypercortisolism. First, true hypercortisolism must be confirmed (or refuted, as in exogenous dexamethasone use where endogenous levels are low, or pseudo-Cushing where diurnal rhythm is intact). Second, ACTH levels determine if the source is ACTH-dependent (high/normal ACTH) or ACTH-independent (suppressed ACTH, implying an adrenal source). Third, high-dose dexamethasone suppression differentiates the ACTH-dependent causes: pituitary sources (Cushing disease) typically suppress, whereas ectopic sources do not.

Step-by-Step Solution

Analyze Profile 4 which presents with paradoxical findings of Cushingoid features but low cortisol levels.

Identifies Exogenous synthetic glucocorticoid use.

Dexamethasone suppresses endogenous ACTH and cortisol but is not detected on standard cortisol assays.

Differentiate between ACTH-dependent and ACTH-independent true Cushing syndrome for Profiles 1, 2, and 3.

Profile 3 has suppressed ACTH, indicating an ACTH-independent source (Primary adrenal adenoma).

Autonomous cortisol secretion from the adrenal glands suppresses pituitary ACTH via negative feedback.

Differentiate the ACTH-dependent causes (Profiles 1 and 2) using the high-dose dexamethasone suppression test.

Profile 1 suppresses (Pituitary adenoma), while Profile 2 does not suppress (Ectopic ACTH).

Pituitary adenomas retain some negative feedback sensitivity at high dexamethasone doses, whereas ectopic sources typically lack functional glucocorticoid receptors.

Analyze Profile 5 for borderline findings in the initial screening tests.

Identifies Physiologic hypercortisolism (Pseudo-Cushing syndrome).

Normal midnight salivary cortisol indicates an intact diurnal rhythm, pointing away from pathological Cushing syndrome.

Key Concept

Diagnostic algorithm for Cushing syndrome and related hypercortisolemic states

Question 2193Question →

A 71-year-old man is evaluated on the medical ward on hospital day 3. He was initially admitted for severe community-acquired pneumonia presenting with fever, productive cough, hypoxemia, and a dense left lower lobe consolidation on a chest radiograph. At the time of admission, empiric therapy with intravenous ceftriaxone and oral azithromycin was initiated. He has shown excellent clinical improvement; his oxygen requirements have resolved, and he has been afebrile for the past 24 hours. The patient is currently tolerating a regular diet and ambulating in the hallways. Both blood and high-quality sputum cultures obtained on admission have finalized, demonstrating the growth of *Streptococcus pneumoniae*. Susceptibility testing results for the isolate are as follows:

Antimicrobial Agent	Interpretation	Minimum Inhibitory Concentration (MIC)
Penicillin	Susceptible	$0.03$ µg/mL
Amoxicillin	Susceptible	$\le 1.0$ µg/mL
Ceftriaxone	Susceptible	$0.25$ µg/mL
Levofloxacin	Susceptible	$0.5$ µg/mL
Azithromycin	Resistant	$> 8.0$ µg/mL

The patient is being prepared for discharge with a prescription to complete a 7-day total course of antibiotics. Which of the following is the most appropriate antibiotic regimen for this patient's discharge?

Oral amoxicillin

Oral amoxicillin-clavulanate

Oral levofloxacin

Oral cefpodoxime

Intravenous ceftriaxone via a peripherally inserted central catheter

Show answer & explanation

Answer: Oral amoxicillin

Answer

Oral amoxicillin

The correct response identifies that the patient requires de-escalation of his antibiotic regimen. He initially received standard empiric therapy (ceftriaxone and azithromycin) for inpatient community-acquired pneumonia. With the pathogen identified as a penicillin-susceptible strain of *Streptococcus pneumoniae*, and the patient clinically stable and tolerating oral intake, the most appropriate next step is to transition to a narrow-spectrum oral agent. High-dose oral amoxicillin effectively treats this infection while strictly adhering to antimicrobial stewardship principles.

Step-by-Step Solution

Identify the primary pathogen and analyze its susceptibility profile from the provided laboratory data.

The pathogen is Streptococcus pneumoniae, which is susceptible to penicillin (and amoxicillin), ceftriaxone, and levofloxacin, but resistant to azithromycin.

Determining the specific etiology and resistance pattern is required to tailor ongoing antimicrobial therapy away from empiric regimens.

Evaluate the patient's clinical trajectory to determine the appropriate route of administration (intravenous vs. oral).

The patient is clinically improved, afebrile, hemodynamically stable, and tolerating an oral diet, indicating he is ready for transition to oral therapy.

Early transition from intravenous to oral therapy reduces catheter-related complications, shortens hospital length of stay, and decreases healthcare costs.

Select the most appropriate oral agent based on the principles of antimicrobial stewardship.

Oral amoxicillin is the optimal choice because it provides highly effective, targeted, narrow-spectrum coverage against this specific isolate.

Using the narrowest effective spectrum minimizes collateral damage to the host microbiome and reduces the selection pressure that drives antimicrobial resistance.

Key Concept

De-escalation of empiric broad-spectrum antibiotic therapy to a targeted, narrow-spectrum agent (e.g., oral amoxicillin) is the standard of care for clinically stable patients with penicillin-susceptible Streptococcus pneumoniae pneumonia.

Estimated Time:1m 0s

Question 2194Question →

The rapid response team is urgently called to evaluate a 58-year-old male due to sudden clinical deterioration. The patient was admitted 48 hours ago with right lower lobe community-acquired pneumonia. He has a history of heart failure with preserved ejection fraction and a 30-pack-year smoking history. His admission blood cultures are currently growing *Streptococcus pneumoniae*, and he has been receiving targeted intravenous ceftriaxone.

Upon evaluation, the patient is lethargic and oriented only to person.

Vital signs are:
- Temperature: $38.6^\circ\text{C}$ ( $101.5^\circ\text{F}$ )
- Heart Rate: $122\text{/min}$
- Blood Pressure: $88/56\text{ mmHg}$
- Respiratory Rate: $34\text{/min}$
- $SpO_2$ : $84\%$ on a high-flow nasal cannula

Physical examination reveals profound use of accessory respiratory muscles. Lung auscultation demonstrates diffuse bilateral crackles and expiratory wheezing. Jugular venous pressure is normal.

Arterial blood gas analysis and relevant laboratories reveal:

Parameter	Value
$pH$	$7.15$
$PaCO_2$	$50\text{ mmHg}$
$PaO_2$	$52\text{ mmHg}$
$HCO_3^-$	$16\text{ mEq/L}$
Serum lactate	$5.2\text{ mmol/L}$

Which of the following is the most appropriate next step in the management of this patient?

Perform endotracheal intubation and mechanical ventilation

Switch current antimicrobial therapy to intravenous vancomycin and cefepime

Administer an intravenous sodium bicarbonate infusion

Administer intravenous furosemide and a nitroglycerin infusion

Administer nebulized albuterol and intravenous methylprednisolone

Show answer & explanation

Answer: Perform endotracheal intubation and mechanical ventilation

Answer

The most appropriate next step is to perform endotracheal intubation and mechanical ventilation.

This patient is in distributive (septic) shock and is exhibiting clear signs of impending respiratory failure. He has severe hypoxemia (

PaO_2 = 52\text{ mmHg}

) and clinical signs of respiratory muscle fatigue (use of accessory muscles, lethargy). Furthermore, his acid-base status confirms a mixed metabolic and respiratory acidosis. He has a metabolic acidosis driven by elevated lactate (

5.2\text{ mmol/L}

). According to Winter's formula (

Expected\ PaCO_2 = 1.5 \times HCO_3^- + 8 \pm 2

), his expected

PaCO_2

should be between

30

and

34\text{ mmHg}

. His actual

PaCO_2

50\text{ mmHg}

, indicating a severe superimposed respiratory acidosis due to inadequate alveolar ventilation. Given his altered mental status (lethargy) and hemodynamic instability, noninvasive positive pressure ventilation is strictly contraindicated, making definitive airway management via endotracheal intubation the most critical next step.

Step-by-Step Solution

Evaluate the patient's clinical status and vital signs.

The patient is lethargic, hypotensive, hypoxemic, and using accessory muscles, indicating septic shock and impending respiratory failure.

Recognizing the signs of respiratory muscle fatigue and altered mental status is critical for determining the urgency of airway intervention.

Analyze the arterial blood gas using Winter's formula to determine the acid-base disorder.

The patient has a primary metabolic acidosis (

HCO_3^-

16\text{ mEq/L}

). Expected

PaCO_2

(1.5 \times 16) + 8 \pm 2 = 32 \pm 2\text{ mmHg}

. Since the actual

PaCO_2

50\text{ mmHg}

, there is a severe concurrent respiratory acidosis.

Identifying the mixed acid-base disorder confirms that the patient's respiratory drive is failing to compensate, necessitating mechanical support.

Select the appropriate method of respiratory support.

Invasive mechanical ventilation via endotracheal intubation is selected.

Non-invasive positive pressure ventilation (NIPPV) is contraindicated due to the patient's lethargy (inability to protect the airway) and hemodynamic instability.

Key Concept

Impending respiratory failure characterized by altered mental status, hypoxemia, and mixed metabolic and respiratory acidosis requires immediate endotracheal intubation.

Question 2195Question →

A previously healthy college student evaluates at the university health clinic reporting sharp, stabbing chest pain that started the day before. The discomfort is severely aggravated by lying flat in bed and taking deep breaths, but provides significant relief when the patient is sitting up and leaning forward. Vital signs reveal a temperature of 38.1°C (100.6°F), heart rate of 98/min, and blood pressure of 118/74 mm Hg. An electrocardiogram demonstrates diffuse, concave ST-segment elevations and PR-segment depressions across most limb and precordial leads. Cardiac troponin levels are within normal limits. Which of the following is the most appropriate initial pharmacological treatment for this patient's condition?

Nonsteroidal anti-inflammatory drugs and colchicine

Dual antiplatelet therapy and a high-dose statin

Intravenous loop diuretics and strict fluid restriction

Inhaled short-acting beta-agonists and oral glucocorticoids

Broad-spectrum intravenous antibiotics

Show answer & explanation

Answer: Nonsteroidal anti-inflammatory drugs and colchicine

Answer

Nonsteroidal anti-inflammatory drugs and colchicine

The correct treatment is the combination of nonsteroidal anti-inflammatory drugs (NSAIDs) and colchicine. The patient's clinical presentation of sharp, pleuritic chest pain that improves with leaning forward, combined with diffuse ST-segment elevations and PR-segment depressions on an electrocardiogram, is classic for acute pericarditis. The standard first-line therapy for idiopathic or viral acute pericarditis consists of NSAIDs (such as ibuprofen or indomethacin) for symptom relief and inflammation reduction, alongside colchicine, which is critical for preventing recurrent episodes.

Step-by-Step Solution

Evaluate the clinical presentation and physical exam findings.

The patient has pleuritic, positional chest pain (worse lying flat, better leaning forward) accompanied by a low-grade fever.

These historical features are highly specific and classic for acute pericarditis.

Analyze the electrocardiogram findings.

The tracing shows diffuse ST-segment elevations and PR-segment depressions.

This ECG pattern is pathognomonic for acute pericarditis, helping to distinguish it from the localized ST elevations typical of an acute myocardial infarction.

Determine the appropriate initial pharmacological therapy.

Nonsteroidal anti-inflammatory drugs (NSAIDs) combined with colchicine.

This dual therapy reduces acute pericardial inflammation, relieves symptoms, and significantly decreases the risk of recurrent disease.

Key Concept

Diagnosis and initial pharmacological management of acute pericarditis.

Question 2196Question →

A patient receiving cytotoxic chemotherapy for acute myeloid leukemia arrives at the oncology triage unit reporting severe chills and a recorded temperature of $38.8^\circ\text{C}$ ( $101.8^\circ\text{F}$ ). Her blood pressure is $100/60\text{ mm Hg}$ , and her heart rate is $112/\text{min}$ . She has an indwelling totally implantable venous access device. Laboratory analysis reveals an absolute neutrophil count of $350/\text{mm}^3$ .

Arrange the following interventions in the most appropriate sequential order for managing this patient's condition according to standard clinical guidelines for high-risk febrile neutropenia.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence is: Obtain blood cultures, administer empiric antipseudomonal beta-lactam therapy, reassess clinical response at 48-72 hours, and finally add empiric antifungal therapy if fever persists after 4-7 days.

High-risk febrile neutropenia is an infectious disease emergency. The standard sequence of care dictates immediately drawing blood cultures to identify the pathogen, followed promptly (within 60 minutes) by empiric broad-spectrum antibiotics with antipseudomonal activity. Once stabilized, the patient is reassessed at 48 to 72 hours when preliminary microbiological data is available. If the patient remains persistently febrile and profoundly neutropenic for 4 to 7 days despite appropriate antibacterial therapy, an occult invasive fungal infection is highly suspected, warranting the sequential addition of empiric antifungal coverage.

Step-by-Step Solution

Identify the clinical emergency

The patient has high-risk febrile neutropenia (absolute neutrophil count <

500/\text{mm}^3

and fever).

Recognizing the condition dictates the extreme urgency of diagnostic and therapeutic interventions.

Prioritize initial diagnostic testing

Blood cultures are drawn from both the central port and a peripheral site as the first active intervention.

Crucial to capture the pathogen before antibacterial agents alter microbiological viability.

Initiate empiric pharmacotherapy

Intravenous antipseudomonal beta-lactam therapy is administered immediately after cultures are drawn.

Delays in antibiotic administration significantly increase mortality in neutropenic patients; it is a time-sensitive emergency.

Plan sequential follow-up and escalation

Reassessment occurs at 48 to 72 hours, with potential addition of empiric antifungals at 4 to 7 days if fever persists.

Aligns with expected microbiological turnaround times and the known timeline for secondary invasive fungal infections.

Key Concept

Chronological management of high-risk febrile neutropenia

Question 2197Question →

A 58-year-old man with a history of diet-controlled type 2 diabetes mellitus is evaluated in the hospital on day 3 of admission. He initially presented with progressive left lower quadrant abdominal pain, nausea, and low-grade fever. Computed tomography of the abdomen and pelvis demonstrated inflammation of the sigmoid colon with surrounding fat stranding, consistent with acute uncomplicated diverticulitis. He was admitted and started on empiric intravenous piperacillin-tazobactam. Currently, his temperature is 37.1°C (98.8°F), his abdominal pain has largely resolved, and he is tolerating a regular diet. Blood cultures drawn on admission have grown *Escherichia coli* and *Bacteroides fragilis*. Susceptibility testing reveals that both isolates are susceptible to amoxicillin-clavulanate, ertapenem, and piperacillin-tazobactam. The *E. coli* isolate demonstrates high-level resistance to ciprofloxacin and levofloxacin. Based on these findings, which of the following is the most appropriate next step in pharmacotherapy?

Transition to oral amoxicillin-clavulanate

Transition to oral ciprofloxacin and metronidazole

Continue intravenous piperacillin-tazobactam

Transition to oral cephalexin and metronidazole

Add intravenous vancomycin to the current regimen

Show answer & explanation

Answer: Transition to oral amoxicillin-clavulanate

Answer

The most appropriate next step is to transition the patient to oral amoxicillin-clavulanate.

The correct answer utilizes optimal antimicrobial stewardship principles. The patient has met the clinical criteria for IV-to-PO conversion (afebrile, tolerating diet, hemodynamically stable). The culture data definitively rules out the use of a fluoroquinolone-based regimen due to resistance. Amoxicillin-clavulanate is available in an oral formulation, covers both the isolated Gram-negative and anaerobic bacteria, and is explicitly listed as susceptible on the panel. Transitioning to this drug allows for safe, effective outpatient completion of therapy.

Step-by-Step Solution

Assess the patient's current clinical trajectory.

The patient is afebrile, his pain has resolved, and he is tolerating oral intake.

These are the criteria for transitioning from intravenous to oral antibiotics and preparing for hospital discharge.

Analyze the microbiologic and susceptibility data provided.

Cultures show *E. coli* and *B. fragilis*. The *E. coli* is resistant to fluoroquinolones but susceptible to amoxicillin-clavulanate.

Antimicrobial therapy must be de-escalated and targeted based on objective susceptibility profiles to prevent resistance.

Select the narrowest, most effective oral regimen.

Oral amoxicillin-clavulanate covers both organisms effectively based on the lab data.

It acts as a potent, single-agent oral therapy, replacing the need for a broad-spectrum intravenous drug or a multi-drug regimen.

Key Concept

In patients recovering from intra-abdominal infections (like diverticulitis), prompt transition to narrow-spectrum oral antibiotics guided by specific culture and susceptibility data is essential for effective antimicrobial stewardship.

Question 2198Question →

A $20$ -year-old woman is brought to the emergency department by her roommate due to confusion, nausea, and ringing in her ears that began several hours ago. The roommate found an empty bottle of an over-the-counter analgesic in their shared bathroom. The patient has a medical history of major depressive disorder. Her temperature is $38.0^\circ$ C ( $100.4^\circ$ F), blood pressure is $112/70$ mm Hg, pulse is $114$ /min, and respirations are $28$ /min. She appears agitated and is breathing deeply and rapidly. Arterial blood gas on room air and serum chemistry results are as follows:

Laboratory Parameter	Result
$pH$	$7.44$
$PaCO_2$	$16$ mm Hg
$PaO_2$	$98$ mm Hg
Sodium ( $Na^+$ )	$140$ mEq/L
Potassium ( $K^+$ )	$3.6$ mEq/L
Chloride ( $Cl^-$ )	$104$ mEq/L
Bicarbonate ( $HCO_3^-$ )	$10$ mEq/L
Blood urea nitrogen	$16$ mg/dL
Creatinine	$0.8$ mg/dL

Which of the following best describes this patient's acid-base status?

Mixed primary high anion gap metabolic acidosis and primary respiratory alkalosis

Primary high anion gap metabolic acidosis with appropriate respiratory compensation

Primary respiratory alkalosis with appropriate metabolic compensation

Mixed primary normal anion gap metabolic acidosis and primary respiratory alkalosis

Primary high anion gap metabolic acidosis and concurrent primary respiratory acidosis

Show answer & explanation

Answer: Mixed primary high anion gap metabolic acidosis and primary respiratory alkalosis

Answer

Mixed primary high anion gap metabolic acidosis and primary respiratory alkalosis

The correct answer accurately identifies two independent primary acid-base disorders using systematic calculation. First, the anion gap is

26

mEq/L (

140 - [104 + 10]

), which defines a high anion gap metabolic acidosis. Second, applying Winter's formula (

1.5 \times 10 + 8 = 23 \pm 2

mm Hg) reveals that adequate respiratory compensation should result in a

PaCO_2

between

21

and

25

mm Hg. Because the patient's actual

PaCO_2

16

mm Hg, she is 'blowing off' more

CO_2

than expected, proving a concurrent primary respiratory alkalosis. This mixed picture, along with tinnitus and hyperthermia, is the hallmark of salicylate toxicity.

Step-by-Step Solution

Calculate the Anion Gap to determine the presence and type of metabolic acidosis.

AG = Na^+ - (Cl^- + HCO_3^-) = 140 - (104 + 10) = 26

mEq/L.

An elevated anion gap (

>12

mEq/L) establishes the presence of a primary high anion gap metabolic acidosis (HAGMA).

Calculate the expected respiratory compensation for the metabolic acidosis using Winter's formula.

Expected

PaCO_2 = 1.5 \times HCO_3^- + 8 \pm 2 = (1.5 \times 10) + 8 = 23 \pm 2

mm Hg (Range:

21-25

mm Hg).

This determines if the change in

PaCO_2

is purely compensatory or if there is a secondary respiratory acid-base disorder.

Compare the actual

PaCO_2

to the expected

PaCO_2

calculated from Winter's formula.

Actual

PaCO_2

(

16

mm Hg) is less than the expected range (

21-25

mm Hg).

Because the patient is hyperventilating more than expected for her level of metabolic acidosis, there is a concurrent primary respiratory alkalosis.

Calculate the Delta Ratio to check for a third hidden disorder.

\Delta AG = 26 - 12 = 14

\Delta HCO_3^- = 24 - 10 = 14

. Ratio =

14/14 = 1.0

A ratio of

1.0

confirms a pure high anion gap metabolic acidosis with no hidden normal anion gap acidosis or metabolic alkalosis.

Key Concept

Salicylate toxicity classically presents with a mixed acid-base disorder: a primary respiratory alkalosis (due to direct stimulation of the medullary respiratory center) and a primary high anion gap metabolic acidosis (due to uncoupling of oxidative phosphorylation and accumulation of organic acids).

Estimated Time:2m 0s

Question 2199Question →

A 60-year-old man suddenly collapses in the hospital cafeteria. You are the first healthcare provider on the scene. Arrange the following initial steps of Basic Life Support (BLS) in the correct chronological order for managing this patient.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence begins with assessing responsiveness, followed by calling for help and activating the emergency response, checking for a pulse and breathing, initiating CPR with chest compressions, and finally applying an AED as soon as it arrives.

According to standard Basic Life Support (BLS) guidelines for healthcare providers, the correct sequence for managing a sudden collapse is structured to minimize delays to definitive care. First, verify scene safety and check for responsiveness. If the patient is unresponsive, immediately activate the emergency response system and call for an AED. Next, simultaneously check for a pulse and normal breathing for no more than 10 seconds. If no pulse is detected, immediately begin high-quality CPR starting with chest compressions (C-A-B sequence). Finally, apply the AED as soon as it is available to analyze the rhythm and deliver a shock if indicated.

Step-by-Step Solution

Assess responsiveness

Confirms the patient is unresponsive

Prevents unnecessary interventions on a conscious person who may have simply stumbled.

Activate the emergency response system

Summons additional personnel and an AED

Early access to advanced care and defibrillation significantly improves survival rates.

Check pulse and breathing

Identifies the presence of cardiac arrest

Determines whether chest compressions or rescue breathing alone are required.

Start CPR (compressions first)

Mechanically circulates oxygenated blood

Maintains vital organ perfusion until definitive treatment can be applied.

Apply the AED

Analyzes the cardiac rhythm

Early defibrillation is the definitive treatment for ventricular fibrillation or pulseless ventricular tachycardia.

Key Concept

Basic Life Support (BLS) sequence for adult cardiac arrest

Question 2200Question →

A 62-year-old male is brought to the emergency department with a 2-day history of severe right upper quadrant abdominal pain, fever, and yellowing of his skin. In the triage area, he becomes increasingly lethargic and confused. Vital signs show a temperature of 39.2°C (102.6°F), blood pressure of 86/50 mmHg, pulse of 118/min, and respirations of 22/min. Physical examination reveals pronounced scleral icterus and right upper quadrant tenderness with involuntary guarding. Laboratory studies show a leukocyte count of 18,500/mm³, total bilirubin of 6.8 mg/dL, direct bilirubin of 5.1 mg/dL, and alkaline phosphatase of 480 U/L.

Arrange the following management steps in the most appropriate chronological order for this patient.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence is to first resuscitate with fluids and antibiotics, then perform an abdominal ultrasound, followed by ERCP for biliary decompression, and finally schedule an elective laparoscopic cholecystectomy.

The patient's presentation of fever, jaundice, right upper quadrant pain, hypotension, and altered mental status represents Reynolds pentad, indicating severe ascending cholangitis with septic shock. The universally accepted management protocol dictates that hemodynamic stabilization and broad-spectrum intravenous antibiotics are the absolute first priorities to reduce mortality. Once the patient is hemodynamically supported, a right upper quadrant ultrasound is the preferred initial diagnostic test to confirm biliary dilation and locate the obstruction. After confirmation, urgent Endoscopic Retrograde Cholangiopancreatography (ERCP) is indicated to definitively decompress the infected biliary tree. Finally, once the patient has fully recovered from the acute episode, an elective laparoscopic cholecystectomy is performed to prevent future gallstone-related complications.

Step-by-Step Solution

Identify the primary clinical syndrome.

The patient exhibits Charcot's triad (fever, jaundice, right upper quadrant pain) plus hypotension and altered mental status.

These five findings constitute Reynolds pentad, which is pathognomonic for severe acute ascending cholangitis complicated by septic shock.

Determine the immediate life-saving intervention.

Intravenous crystalloid resuscitation and broad-spectrum antibiotics are initiated.

In severe sepsis, restoring tissue perfusion and initiating antimicrobial therapy takes absolute priority over diagnostic imaging or definitive procedural interventions.

Select the best initial diagnostic modality.

Right upper quadrant abdominal ultrasound is performed.

Ultrasound is the most appropriate initial, non-invasive imaging test to confirm common bile duct dilation and detect choledocholithiasis rapidly.

Determine the definitive acute treatment.

Endoscopic retrograde cholangiopancreatography (ERCP) is conducted.

ERCP allows for urgent decompression of the infected biliary tree and extraction of the obstructing stone, which is the definitive treatment for the acute ascending cholangitis episode.

Formulate a long-term preventive plan.

Elective laparoscopic cholecystectomy is planned.

Removing the gallbladder prevents the formation of future stones, thereby eliminating the risk of recurrent cholangitis or gallstone pancreatitis.

Key Concept

The management sequence for severe acute ascending cholangitis (Reynolds pentad) prioritizes hemodynamic stabilization and broad-spectrum antibiotics, followed by diagnostic imaging, urgent biliary decompression via ERCP, and eventual elective cholecystectomy.

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