Infectious Disease Compendium

Peritonitis

Diagnosis

Fevers and abdominal pain. To diagnose SBP in ascites (PubMed):

"- preprocedure coagulation was likely unnecessary prior to paracentesis

- a 15-gauge, 3.25-inch needle-cannula results in less multiple peritoneal punctures and termination due to poor fluid return

- immediate inoculation of culture bottles improves diagnostic yield vs delayed (from 77% to 100%)

- biochemical analysis of ascitic fluid in patients suspected of having spontaneous bacterial peritonitis to increase the likelihood of spontaneous bacterial peritonitis (PMN count >250 cells/µL;ascitic fluid leukocyte count >1000 cells/µL; pH < 7.35; or a blood–ascitic fluid pH gradient 0.10 or a blood–ascitic fluid pH gradient < 0.10."

Epidemiologic Risks

Three flavors:

a) from a perforated viscous.

b) spontaneous in a patient with ascites aka SBP (a review (PubMed)). Bacteremia is a poor prognostic sign (PubMed). In this population, acid suppression increases the risk of SBP (PubMed) (PubMed).

c) as a complication of peritoneal dialysis.

Microbiology

a) from a perforated viscous often mixed: E. coli + Streptococci (esp milleri) + anaerobes, and not infrequently, Candida. If a gastric ulcer perforation, high likelihood that Candida is the predominant organism.

b) spontaneous in a patient with ascites: S. pneumoniae and E. coli. In Korea and Taiwan Aeromonas is a major cause of SBP in cirrhotics (PubMed). In one series, 4% were due to Enterococcus and failure to treat early was associated with worse outcomes (PubMed).

c) as a complication of peritoneal dialysis: coag negative staphylococcus is most common, but all organisms are possible. People with pets can find their cat or dog or I suppose moose, people have the damnedest pets, microbiology in the peritoneal space (PubMed); I had one case of Pasteurella peritonitis in a patient whose cat slept in the bag warmer.

Young females get Group A streptococcal SBP. I had a young female with SBP, culture negative, that had Mycoplasma hominis on PCR of tissue biospy (Medscape).

Empiric Therapy

a) from a perforated viscous. I prefer a third generation cephalosporins PLUS metronidazole. Alternatives include a carbapenem OR penicillin/beta-lactamase inhibitors OR a (quinolone PLUS metronidazole OR clindamycin).

b) spontaneous in a patient with ascites: third generation cephalosporins OR a quinolone. Prophylaxis of SBP: ciprofloxacin 750 mg q week, trimethoprim/sulfamethoxazole DS 5x/wk, norfloxacin 400 mg qd (and probably any other quinolone ) are reasonable and prevents infection, especially if they are on the transplant list. It doesn't decrease mortality, but they get fewer episodes, and each episode of SBP pushes them down the transplant list.

c) as a complication of peritoneal dialysis: pull the catheter if possible, vancomycin AND aminoglycoside OR a third generation cephalosporin AND vancomycin OR a quinolone AND vancomycin often given in the peritoneal dialysis fluid; ask you local nephrologist for help.

Pearls

If you grow an anaerobe from the peritoneal fluid of a peritoneal dialysis patient they have a hole in the gut, probably from the catheter eroding through the bowel wall. Always.

After a colonic perforation and clean out, try and check a CT 5 -7 days later, not matter how well the patient is doing clinically; often they have an abscess.

Many patients with ascites get endoscopy for bleeds: if Childs B or C, ceftriaxone is the best prophylaxis (PubMed).

Rants

Try and get cultures, would you? Yes, I know, I know, its bowel flora. But there is so much resistance these days that it is hard to guess the best antibiotics.