Episode 123: Spontaneous Bacterial Peritonitis.  

Kaitlen defines spontaneous bacterial peritonitis (SBP) and also explains the diagnosis and management.  

Written by Kaitlen Roy-Ross, MS4, Ross University School of Medicine. Moderated by Hector Arreaza, MD. 

Definition:

An ascitic fluid infection with no obvious surgically treatable intra-abdominal source (bowel perforation, abscess, perforated ulcer). Commonly seen in patients with cirrhosis and ascites. 

Patients may have symptoms of fever, abdominal pain, abdominal tenderness, altered mental status, and hypotension.

Etiology: The most common pathogens (75%) are gram-negative aerobic organisms. Klebsiellapneumoniae accounts for 50% of the cases. Gram-positive aerobic bacteria (Streptococcus pneumoniae or viridans group streptococcus) account for the remaining cases. 

Some report E. coli as the most common cause of SBP. Random information: in Korea, Aeromonas hydrophila is an important pathogen of SBP during the summer. 

Diagnosis: To diagnose SBP, a paracentesis should be performed to analyze the ascitic fluid prior to treating the patient with antibiotics.

The ascitic fluid should be analyzed for the following: 

• PMN (Polymorphonuclear cell) count: > or = to 250 cells/mm3 
• Aerobic and anaerobic cultures
• Serum ascites albumin gradient (serum albumin-ascitic albumin): this measures portal pressure.

If the gradient is > 1.1 = portal HTN is present (cirrhosis, heart failure, large liver malignancy, alcoholic hepatitis, portal vein thrombosis) – SBP is likely.

If the gradient is <1.1= portal HTN NOT present (peritoneal carcinomatosis or tuberculosis, pancreatitis, nephrotic syndrome) – SBP less likely.

• Ascites fluid total protein concentration: (<1 g/dL): When protein concentration in ascitic fluid is less than 1 g/dL, there is a low concentration of ópsonins (proteins that bound to bacteria to induce phagocytosis) and patients are at high risk for SBP. The concentration of protein in the peritoneal fluid does not change during SBP. So, if the protein concentration is high, think about secondary bacterial peritonitis. 
• Glucose: > 50 mg/dL
• LDH: 43 +/- 20
• Amylase- will be increased in pancreatitis or gut perforation. No SBP.
• Bilirubin- increased bilirubin in ascitic fluid greater than serum bilirubin or > 6 mg/ suggests a gallbladder perforation. No SBP.

Treatment:

The treatment for spontaneous bacterial peritonitis is broad-spectrum antibiotics. 

Empiric treatment is indicated if a patient with ascites has any of the following:

• Temperature > 100 F
• Abdominal pain or tenderness
• Altered mental status
• PMN in ascitic fluid > 250 (but if there is bacteria in ascitic fluid, start antibiotics stat)
• Alcohol-induced hepatitis

*Important note: Patients on beta blockers should have them permanently discontinued prior to treatment for SBP as beta blockers are associated with worse outcomes. In one study, patients on beta blockers had a 58% increase in mortality risk compared to patients not treated with beta-blockers. Beta-blockers were also associated with higher rates of hepatorenal syndrome and longer lengths of hospital stay.

1st line treatment- 3rd generation Cephalosporin Cefotaxime 2g IV Q8H (preferred) or Ceftriaxone 2 g per day

2nd line treatment- Carbapenems. Usually reserved for patients with severe disease/critical illness.

3rd line- Fluoroquinolones- Cipro 400 mg IV BID to patients with normal renal function. (Patients should not get this if they already receiving it prophylactically.)

Duration of treatment:

5 days, then re-assess