Gastroenterology · Cirrhosis Complications
The facts most likely to be tested
The gold standard for diagnosis is an ascitic fluid absolute neutrophil count (ANC) ≥ 250 cells/mm³.
The most common causative organisms are gram-negative bacteria, specifically Escherichia coli and Klebsiella pneumoniae.
Clinical presentation often includes fever, abdominal pain, and altered mental status in a patient with decompensated cirrhosis.
Empiric antibiotic therapy of choice is third-generation cephalosporins such as cefotaxime or ceftriaxone.
Intravenous albumin is administered concurrently with antibiotics to prevent hepatorenal syndrome and reduce mortality.
Prophylactic treatment with fluoroquinolones (e.g., norfloxacin or ciprofloxacin) is indicated for patients with low ascitic fluid protein (< 1.5 g/dL) or a history of prior SBP.
A polymicrobial infection on ascitic fluid culture or high protein/low glucose levels should raise suspicion for secondary bacterial peritonitis due to a perforated viscus.
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A 58-year-old male with a history of alcohol-associated cirrhosis presents to the emergency department with a two-day history of diffuse abdominal pain and low-grade fever. On physical exam, he is lethargic and has diffuse abdominal tenderness with rebound tenderness and shifting dullness. Laboratory studies reveal a serum creatinine of 1.8 mg/dL, up from a baseline of 1.0 mg/dL. A diagnostic paracentesis is performed.
What is the most appropriate next step in management?
Initiate intravenous cefotaxime and intravenous albumin.
The patient's presentation of fever, abdominal pain, and altered mental status in the setting of cirrhosis is highly suggestive of SBP; immediate empiric treatment with third-generation cephalosporins and albumin is required to prevent renal failure and mortality.
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Etiology / Epidemiology
Occurs in patients with cirrhosis and ascites. Translocation of gut bacteria is the primary mechanism.
Clinical Manifestations
Classic fever, abdominal pain, and altered mental status. Look for rebound tenderness.
Diagnosis
Gold standard is paracentesis. Diagnostic threshold is PMN count ≥ 250 cells/µL.
Treatment
First-line is cefotaxime. Avoid aminoglycosides due to nephrotoxicity.
Prognosis
High mortality rate. Prophylaxis required for patients with low protein ascites.
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Epidemiology & Etiology
SBP is a life-threatening infection of ascitic fluid without an evident intra-abdominal surgical source. It primarily affects patients with decompensated cirrhosis and portal hypertension. The most common pathogens are E. coli, Klebsiella, and Streptococcus pneumoniae.
Pertinent Anatomy
The peritoneal cavity acts as a reservoir for ascitic fluid, which lacks sufficient opsonins to clear bacterial translocation. Impaired intestinal motility and increased permeability allow bacteria to cross the gut wall into the sterile fluid.
Pathophysiology
Bacterial translocation from the gut lumen to the mesenteric lymph nodes leads to bacteremia and subsequent seeding of ascitic fluid. The low protein concentration in cirrhotic ascites (<1 g/dL) reduces local complement activity. This creates a permissive environment for rapid bacterial proliferation and systemic inflammatory response.
Clinical Manifestations
Patients often present with fever, diffuse abdominal pain, and altered mental status (often the only sign). Physical exam reveals rebound tenderness and decreased bowel sounds. Red flags include hypotension, hypothermia, and worsening renal function indicating sepsis.
Diagnosis
The gold standard is diagnostic paracentesis. A PMN count ≥ 250 cells/µL is diagnostic of SBP. Culture results are often negative, but treatment must be initiated based on the PMN count alone.
Treatment
Initiate empiric cefotaxime (or other third-generation cephalosporins) immediately after fluid collection. Avoid aminoglycosides due to the high risk of acute kidney injury in cirrhotic patients. Consider IV albumin if creatinine >1 mg/dL or BUN >30 mg/dL to prevent hepatorenal syndrome.
Prognosis
SBP carries a high risk of recurrence; long-term prophylaxis with trimethoprim-sulfamethoxazole or norfloxacin is indicated for survivors. Monitor for hepatorenal syndrome and progressive liver failure.
Differential Diagnosis
Secondary peritonitis: presence of multiple organisms on culture or surgical source
Tuberculous peritonitis: elevated lymphocytes rather than neutrophils
Pancreatitis: elevated amylase in ascitic fluid
Peritoneal carcinomatosis: high serum-ascites albumin gradient (SAAG) with malignant cells
Bowel perforation: presence of free air on imaging