A 64-year-old man is brought to the emergency department by his family due to a 2-day hist… — USMLE Step 2 CK

A 64-year-old man is brought to the emergency department by his family due to a 2-day history of increasing confusion, low-grade fever, and abdominal discomfort. The patient has a history of decompensated cirrhosis secondary to metabolic dysfunction-associated steatotic liver disease (MASLD). He takes furosemide, spironolactone, and lactulose, but his family reports he has been less compliant with his medications over the past week. His temperature is $38.0^\circ\text{C}$ ( $100.4^\circ\text{F}$ ), blood pressure is $105/65\text{ mmHg}$ , and heart rate is $98/\text{min}$ . Physical examination reveals scleral icterus and a distended abdomen with shifting dullness. There is diffuse, mild abdominal tenderness without rebound or guarding. Asterixis is present.

Laboratory results are as follows:

Laboratory Parameter	Result
Hemoglobin	$10.5\text{ g/dL}$
Leukocyte count	$11,500/\text{mm}^3$
Platelet count	$82,000/\text{mm}^3$
Total bilirubin	$3.8\text{ mg/dL}$
Blood urea nitrogen	$36\text{ mg/dL}$
Serum creatinine	$1.6\text{ mg/dL}$

A diagnostic paracentesis is performed, yielding cloudy yellow fluid. Ascitic fluid analysis reveals:

Ascitic Fluid Analysis	Result
Total leukocyte count	$1,000/\text{mm}^3$
Neutrophils	$85\%$
Total protein	$1.1\text{ g/dL}$

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

Intravenous ceftriaxone and albuminAnswer
B
Intravenous ceftriaxone alone
C
Intravenous ceftriaxone and metronidazole
D
Intravenous piperacillin-tazobactam and vancomycin
E
Oral ciprofloxacin and intravenous albumin

Answer

The most appropriate next step is to initiate intravenous ceftriaxone and albumin.

The correct answer is to administer both intravenous ceftriaxone and albumin. This patient's presentation of fever, confusion, and abdominal tenderness in the setting of cirrhosis strongly suggests spontaneous bacterial peritonitis (SBP). The diagnosis is confirmed by an ascitic fluid absolute neutrophil count of

850/\text{mm}^3

(diagnostic threshold is

\geq 250/\text{mm}^3

). Empiric treatment requires a third-generation cephalosporin (e.g., ceftriaxone) to cover enteric gram-negative organisms. Furthermore, SBP frequently triggers severe renal vasoconstriction, leading to hepatorenal syndrome (HRS). To prevent HRS, intravenous albumin is indicated in patients who meet high-risk criteria: a serum creatinine

> 1.0\text{ mg/dL}

, blood urea nitrogen (BUN)

> 30\text{ mg/dL}

, or total bilirubin

> 4.0\text{ mg/dL}

. Because this patient has a creatinine of

1.6\text{ mg/dL}

and a BUN of

36\text{ mg/dL}

, concurrent albumin administration is essential to reduce mortality.

Step-by-Step Solution

Calculate the absolute neutrophil count in the ascitic fluid to confirm the diagnosis.

The absolute neutrophil count is

1,000 \times 0.85 = 850/\text{mm}^3

An ascitic fluid neutrophil count

\geq 250/\text{mm}^3

is diagnostic for spontaneous bacterial peritonitis (SBP).

Determine the optimal empiric antibiotic regimen for community-acquired SBP.

Intravenous third-generation cephalosporins (e.g., ceftriaxone or cefotaxime) are the treatment of choice.

They provide excellent coverage against the most common pathogens responsible for SBP, which are enteric gram-negative organisms (such as Escherichia coli and Klebsiella pneumoniae).

Evaluate the patient's renal function to determine if adjunctive therapy is indicated.

The patient has a blood urea nitrogen (BUN) of

36\text{ mg/dL}

and a serum creatinine of

1.6\text{ mg/dL}

Patients with SBP are at high risk for developing acute kidney injury (hepatorenal syndrome). Intravenous albumin is indicated if the patient has a BUN

> 30\text{ mg/dL}

, a serum creatinine

> 1.0\text{ mg/dL}

, or a total bilirubin

> 4.0\text{ mg/dL}

Key Concept

Diagnosis of spontaneous bacterial peritonitis requires an ascitic fluid absolute neutrophil count

\geq 250/\text{mm}^3

; treatment involves a third-generation cephalosporin and intravenous albumin for patients with elevated creatinine, BUN, or bilirubin.

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