A 56-year-old man is brought to the emergency department by his family due to worsening co… — USMLE Step 2 CK

A 56-year-old man is brought to the emergency department by his family due to worsening confusion and diffuse abdominal pain over the past $48$ hours. He has also experienced nausea and has not had a bowel movement for two days. His medical history is significant for decompensated cirrhosis secondary to chronic hepatitis C infection. He takes furosemide, spironolactone, and nadolol. His temperature is $38.3^\circ\text{C}$ ( $100.9^\circ\text{F}$ ), pulse is $102/\text{min}$ , blood pressure is $105/65\text{ mm Hg}$ , and respirations are $18/\text{min}$ . Physical examination shows scleral icterus and a distended abdomen with shifting dullness. There is diffuse, mild abdominal tenderness without rebound or guarding. Bowel sounds are hypoactive. Bilateral asterixis is present. Laboratory studies show:

Laboratory Parameter	Result
Leukocyte count	$12,500/\text{mm}^3$ ( $88\%$ neutrophils)
Platelet count	$75,000/\text{mm}^3$
Total bilirubin	$4.2\text{ mg/dL}$
Creatinine	$1.3\text{ mg/dL}$

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

Perform a diagnostic paracentesisAnswer
B
Administer intravenous ceftriaxone
C
Obtain a computed tomography scan of the abdomen
D
Insert a nasogastric tube for bowel decompression
E
Measure serum ammonia concentration

Answer

The most appropriate next step is to perform a diagnostic paracentesis.

This patient's presentation of fever, diffuse abdominal pain, and altered mental status (hepatic encephalopathy) in the setting of decompensated cirrhosis and ascites is highly suspicious for spontaneous bacterial peritonitis (SBP). The standard of care and the most appropriate next step is to perform a diagnostic paracentesis. Ascitic fluid must be analyzed for cell count, differential, and bacterial culture. An absolute neutrophil count (ANC) of

\geq 250/\text{mm}^3

is diagnostic for SBP. It is critical to obtain the ascitic fluid sample before administering empiric antibiotics, as even a single dose of antibiotics can sterilize the culture and impede targeted treatment.

Step-by-Step Solution

Identify the patient's underlying condition and acute presentation.

The patient has known decompensated cirrhosis presenting with the classic triad of spontaneous bacterial peritonitis (SBP): fever, abdominal pain, and altered mental status (hepatic encephalopathy).

Recognizing the high risk of SBP in patients with ascites who present with clinical deterioration.

Evaluate the gastrointestinal symptoms in the context of the systemic illness.

The nausea, lack of bowel movements, and hypoactive bowel sounds are indicative of a paralytic ileus.

Paralytic ileus frequently accompanies severe intra-abdominal infections such as peritonitis, and must be differentiated from a mechanical bowel obstruction.

Determine the proper diagnostic sequence.

A diagnostic paracentesis must be performed immediately.

Ascitic fluid analysis (specifically an absolute neutrophil count greater than or equal to 250/mm³) is required to confirm SBP and obtain cultures before empiric antibiotics sterilize the fluid.

Key Concept

Spontaneous bacterial peritonitis (SBP) typically presents with fever, abdominal pain, and altered mental status in a patient with cirrhosis and ascites. A diagnostic paracentesis must be performed prior to the initiation of empiric antibiotics.

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