Thursday, April 14, 2011

Spontaneous bacterial peritonitis

An acute bacterial infection of ascitic fluid. Happens in people with ascites due to any etiology(even with CHF, Budd chiari !!!). The route of infection is still not entirely clear. It may be a simple translocation of bacteria from the gut due to bacterial overgrowth  (as previously thought), or from hematogenous spread. But in general its the gut bacteria which accounts for most of SBP. This is mainly due to reduced intestinal transit times in pts with cirrhosis, along with low protein and complement levels etc.
The common bugs are E.Coli, Klebsiella and Strep pneumoniae.
Diagnosis is based on diagnostic aspiration of the ascitic fluid. We all tap the ascitic fluid in someone with symptoms of infection(fever, abdominal pain, tenderness etc). But around 30% of pts with SBP might not have any symptoms!! So...what shall we do?.........One of our gastroenterologist says...."JUST TAP ALL ASCITES". Well...he might be right...given a mortality range of 30-70% for SBP!

Based on the can be classified as follows...
1.SBP - if >250 PMN/micL  AND positive culture.
2.Culture-negative neutrocytic ascites -ascitic fluid culture is negative, but PMN count is ≥ 250 cells/µL. 
3. Monomicrobial nonneutrocytic bacterascites - positive culture result with a PMN count ≤ 250 cells/µL.
Irrespective of what type it is!!!......they all need to be treated based on clinical suspicion.

A very simple method being used these days(mostly in Europe) to diagnose SBP is the simple Leukocyte esterase test, which can be done at bedside. It has a sensitivity & specificity of 100 % & 91% resp to diagnose SBP! ( E Jof Gastro Hep 2007)
What to treat with -- A 3rd generation Cephalosporin or a fluroquinolone. Its rare to have anaerobic SBP , as ascitic fluid is rich in Oxygen!

When to use albumin - One of the main causes of mortality in SBP is due to development of renal failure. Albumin in addition to antibiotics have shown to prevent renal impairment and also to reduce mortality by around 10 to 15%based on this randomised trial(NEJM 1999). Its given as 1.5 g/kg at diagnosis and 1 g/kg on Day3.There is another randomised trial underway in Brazil to add more evidence to this practice.(ALTERNATE trial). 

Prohylaxis for SBP - Well..there are a group of patients who will benifit from prophylaxis. They are 1.anyone with a previous episode of SBP reducing mortality by 25% over a 1 year period(Hepatology 1990)  2. GI bleed with a course of 7 days.  3.pts with ascitic fluid protein <1 g/dl plus one of the following --- creatinine >1.5, bilirubin>4.(Hepatology 1995) The last criteria is a soft call, and would depend on local practice.The last two indications are a short course(1 -2 weeks) of antibiotics.The first indication is a longer term prophylaxis (1 year or more). Norfloxacin 400 daily is a preferred drug(as it selectively targets Gram negatives, and leaves anaerobes !)