Re-evaluation of the value of ascitic fluid pH lactate dehydrogenase and total proteins in the diagnosis of spontaneous bacterial peritonitis (SBP).

In view of high mortality, variable clinical presentation, and late results of bacterial culture, early diagnosis of SBP and treatment are based on indirect parameters of infection. Forty-two patients with ascites and liver cirrhosis were studied. Ascitic fluid (AF) was examined for total protein content, pH, lactate dehydrogenase, amylase, absolute polymorphonuclear cell count (PMN) and for presence of bacteria by examining a fresh smear of the deposit and culture of the fluid under aerobic and anaerobic conditions. AF/serum gradient of total proteins and LDH was calculated. One patient proved to have a malignant ascites and was excluded. The remaining 41 patients fell into two groups: Group I PMN less than 250 cell mm-3, culture negative, sterile ascites, 36 patients. Group II PMN greater than 250 cell mm-3. (a) Culture positive neutrophilic ascites (SBP), three patients. (b) Culture negative neutrophilic ascites (CNNA), two patients. In both CNNA and SBP:AF/serum total LDH gradient greater than 0.75 In the sterile group: AF/serum total LDH gradient less than 0.58 There was no correlation between presence of infection and ascitic fluid pH, protein content and AF/serum total protein gradient. Therefore AF PMN greater than 250 mm and AF/serum total LDH gradient greater than 0.6 should be considered reliable, indirect parameters of infection, and CNNA a variant of SBP with a small bacterial inoculum size.