The diagnosis of bacterial peritonitis: comparison of pH, lactate concentration and leukocyte count.

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It has been suggested that the hydrogen ion and lactate concentrations may be superior to the polymorphonuclear cell count (PMN) in ascitic fluid, in the diagnosis of bacterial peritonitis (BP). In order to compare the diagnostic accuracy of ascitic fluid measurements of pH, lactate, glucose and the PMN in BP, we analyzed the ascitic fluids of 70 consecutive patients in whom pH, lactate, glucose and the PMN count were measured in ascitic fluid and arterial blood. Fifty-one were cirrhotic patients with uninfected ascites, 14 had BP, one tuberculous peritonitis, two ascites secondary to peritoneal metastases and two with neoplastic liver involvement but without peritoneal metastases. Statistically, highly significant differences between patients with uninfected ascitic fluid and BP were observed for ascitic fluid PMN (122 vs. 2,686 per cu mm), ascitic fluid pH (7.45 vs. 7.24), arterial-ascitic fluid pH gradient (0.02 vs. 0.22), arterial lactate (12 vs. 25 mg per dl), ascitic fluid lactate (15 vs. 45 mg per dl) and arterial-ascitic fluid lactate gradient (-3 vs. -20 mg per dl). The most reliable diagnostic cutoff levels were determined for each of the parameters: PMN greater than 500 per cu mm; ascitic fluid pH less than 7.35; arterial-ascitic fluid pH gradient greater than 0.10; ascitic fluid lactate greater than 25 mg per dl; arterial-ascitic fluid lactate gradient less than -20 mg per dl; ascitic fluid glucose less than 60 mg per dl; arterial-ascitic fluid glucose gradient greater than 60 mg per dl.(ABSTRACT TRUNCATED AT 250 WORDS)