White Count, Ph and Lactate in Ascites in the Diagnosis of Spontaneous Bacterial Peritonitis

In order to evaluate the diagnostic accuracy of ascitic pH and lactate for early confirmation of spontaneous bacterial peritonitis (SBP), 109 consecutive patients with ascites were studied. The mean ascitic leukocyte white blood cell (WBC) and polymorphonuclear cell (PMN) counts, pH and lactate levels in 42 patients with sterile “normal” ascites were 124 ± 157 per mm 3 , 41 ± 77 per mm 3 , 7.502 ± 0.097 and 11.1 ± 7.9 mg per dl, respectively, Mean ascitic WBC and PMN counts were significantly increased in 10 patients with SBP (10,452 ± 8,091 and 9,522 ± 7,470 per mm 3 ), in 10 patients with bloody ascites (2,591 ± 4,284 and 1,057 ± 1,494 per mm 3 ) and in 11 patients with cytology positive malignant ascites (1,529 ± 2,071 and 868 ± 1,601 per mm 3 ) (p < 0.001). Mean ascitic pH was significantly reduced in SBP (7.335 ± 0.048), in bloody ascites (7.384 ± 0.037) and in cytology positive malignant ascites (7.355 ± 0.167) (p < 0.001). Mean ascitic lactate was also significantly elevated in these three groups of patients (36.8 ± 17.0, 42.8 ± 35.8 and 24.0 ± 17.5 mg per dl, respectively; p < 0.001) as well as in patients with bacteremia (51.6 ± 78.0 mg per dl, p < 0.005). However, ascitic pH less than 7.31, ascitic lactate greater than 33 mg per dl were observed only in three of the patients with SBP. It is concluded that, after excluding bloody ascites, malignancy and systemic lactic acidosis, the diagnosis of SBP could be made with high sensitivity, specificity and predictive value if ascitic fluid studies fulfill any two of the following three criteria: (i) WBC greater than 1,000 per mm 3 or PMN greater than 500 per mm 3 ; (ii) pH less than 7.40, and (iii) lactate greater than 25 mg per dl.