Does spontaneous bacterial peritonitis occur in malignant ascites?

Spontaneous bacterial peritonitis is a well-described entity estimated to occur in 8% of patients with cirrhotic ascites. Characteristic clinical findings may often be absent and the only manifestation may be decompensation of liver function. Ascites at Memorial Hospital is most commonly related to malignancy. We reviewed the records of 101 patients with ascitic fluid cytology positive for malignancy during the calendar year 1979. The most common malignant cytological diagnosis was adenocarcinoma, seen in 76 patients. Of the 101 patients with positive ascitic fluid cytology, 65 fluid specimens had microbiological studies performed which included aerobic, anerobic, fungal, and acid fast bacterial cultures. Only three patients had positive ascitic fluid cultures. We believe that these three patients had other reasons for peritonitis and do not represent true spontaneous bacterial peritonitis. Ascites alone, without liver disease, seem to predispose to spontaneous bacterial peritonitis. Perhaps, the presence of liver disease with less than normally effective hepatic reticuloendothelial function and portasystemic shunting is needed for the development of spontaneous bacterial peritonitis.