Diagnosis
Classic signs and symptoms of peritonitis, including fever, chills, abdominal pain, and
increasing ascites may or may not be present in cirrhotic patients who have SBP. Abdominal
symptoms may be absent in up to one-third of cases. Patients with SBP may present with
encephalopathy, gastrointestinal bleeding, or increasing renal insufficiency. Therefore a high
index of suspicion must be maintained in all cases of cirrhotic patients who have ascites and
are acutely ill.
A diagnostic paracentesis must be performed on all patients suspected to have SBP. A
PMNL count in ascitic fluid of greater than 250 cells/mm^3 is highly suggestive of infection.
Gram-stain of centrifuged ascitic fluid will reveal organisms in approximately 30% of cases.
The fluid should be cultured both aerobically and anaerobically. Inoculating some fluid
directly into blood culture bottles increases the yield of positive cultures. But this
nonquantitative culture technique also increases the risk of false-positives if any skin flora
contaminant is introduced into the blood culture bottle at the bedside.
As indicated previously, aerobic gram-negative enteric bacilli are the most frequent
isolates from ascitic fluid cultures in SBP. Anaerobes are uncommon causes of SBP, and their
presence in ascitic fluid should raise suspicions for bowel perforation. If ascitic fluid cultures
yield polymicrobial flora,Candida albicans(or other yeast), orBacteroides fragilisone should
suspect a secondary peritonitis caused by an acute abdominal infection.
Treatment
Historically SBP has been a severe, frequently fatal infection. In the past few decades mortality
rates have dropped from over 90% in the 1970s to the current 20% to 40% mortality for patients
who have their first diagnosis of SBP. Earlier detection and treatment and the use of non-
nephrotoxic antibiotics has contributed to the increased short-term survival. The most common
causes of death in patients with SBP are liver failure, gastrointestinal bleeding, and renal
failure. One of the greatest threats to long-term survival is recurrence of SBP, which can occur
in 70% of patients (29).
Previously aminoglycosides, alone or in combination with beta-lactam antibiotics, were
widely used to treat SBP. However the risk of aminoglycoside nephrotoxicity in cirrhotic
patients has limited the usefulness of this class of agents (30). Expanded-spectrum
cephalosporins are active against most of the strains of enteric gram-negative pathogens that
cause SBP. Cefotaxime has been shown effective in a number of trials with regimens of 2 g
administered every 8 hours for five days (26) or 2 g every 12 hours for a mean of nine days (31).
In a more recent study (32) 24/33 (73%) of cirrhotic patients with SBP had clinical and
bacteriologic cures after receiving one gram of ceftriaxone every 12 hours for 5 days. With
Figure 1 Pathogenic mechanisms
underlying spontaneous bacterial perito-
nitis.Source:Adapted from Ref. 1.Infections in Cirrhosis in Critical Care 343