Ascitic fluid pH in alcoholic cirrhosis: a reevaluation of its use in the diagnosis of spontaneous bacterial peritonitis.

Abstract

SUMMARY An ascitic fluid pH-7-31 has been advanced as being the best index in the early diagnosis of spontaneous bacterial peritonitis in cirrhotic patients. In order to test the validity of this criteria, 55 patients with alcoholic cirrhosis and ascites were studied. In each patient, arterial blood and ascitic fluid samples were analysed for pH, PCO2, total CO2 and P02, and the pH gradient between blood and ascites was calculated. White blood cell and polymorphonuclear cell counts were determined in ascitic fluid, and cultures of ascites were done under aerobic and anaerobic conditions. Twelve patients had a culture proven spontaneous bacterial peritonitis. Their mean ascitic fluid pH (±SD) was 7-38±0-09 (range 7.21-7.49) and differed significantly (p<005) from that found in patients without spontaneous bacterial peritonitis: 7-44±0*06 (range 7.34-7.63). A marked overlap was observed, however, between the two groups, and only three out of the 12 patients with spontaneous bacterial peritonitis had an ascitic fluid pH-7*31. The pH gradient was 0* 10±0-08 (range -0.01 to +0 28) in the spontaneous bacterial peritonitis group, as compared with 0-02±0-04 (range -0 09 to +0.12) in the sterile group (p<001), but a marked overlap was also noted between the two groups. In the spontaneous bacterial peritonitis group, the polymorphonuclear count was 3588±3849/,ul (range 60-11 776) versus 41±138/,l (range 0-813) in the sterile group (p<00001). All but one patient in the spontaneous bacterial peritonitis group and only two patients in the sterile group had over 250 polymorphonuclear/,ul.Thus, in our experience, neither the ascitic fluid pH nor the pH gradient values accurately discriminated the individual patients with and without spontaneous bacterial peritonitis. A polymorphonuclear count >250/,ul remained the best criteria for the diagnosis of spontaneous bacterial peritonitis in cirrhotic patients, before having the results of ascitic fluid cultures.Gitlin et al advocated the measurement of pH in ascitic fluid for the early diagnosis of spontaneous bacterial peritonitis in patients with alcoholic cirrhosis.' These authors showed that an ascitic fluid pH level of 7.31 perfectly separated the patients with spontaneous bacterial peritonitis from those without, and suggested that this index has a better diagnostic value for ascitic fluid infection than the cytologic criteria. These provocative results have recently been questioned,2 and the aim of this study

Spontaneous bacterial peritonitis: An explosion of information

“…Much has also been learned about the utility of the ascitic fluid cell count in the diagnosis of SBP. Eight studies have been published comparing the neutrophil (PMN) count to ascitic fluid pH and/or lactate in making a rapid presumptive diagnosis of SBP, using bacterial culture as the gold standard (24)(25)(26)(27)(28)(29)(30)(31). The PMN count (with a cut-off of 250,450 or 500 cells per mm3) remains the single best test.…”

Diagnosis of Spontaneous Bacterial Peritonitis in Cirrhotic Patients

“…Many recent reports have evaluated the diagnostic value of ascitic fluid pH [11,18,[21][22][23][25][26][27]: all confirmed the initial ob servation of Gitlin et al [17] that ascitic fluid pH was decreased in patients with SBP, but failed to find a cut-off value which could discriminate between infected and nonin fected patients. Ascitic fluid pH levels lower than 7.35 had a sensitivity of 60% [11,17,18,21,22,25,26] and a specificity higher than 95% [11,17,18,21,22,25,26], In order to improve the sensitivity of this in dex, arterial-ascitic fluid pH gradient has been studied.…”

“…These two latter tech niques have increased the number of positive cultures by approximately 20% [9, pers. data], A single organism is found in 90% of patients with SBP [1-3, 5-8, II, 13,17,18,22,25,26], In more than half the patients, the organisms are enteric in origin and in the oth ers they are of diverse types. The most fre quently encountered organisms and their prevalence are listed in table II; it should be emphasized that the great majority of organ isms (about 90%) are aerobic and that there are few anaerobic bacteria in SBP.…”

“…Arterial pH values were simi lar in patients with and without SBP [11,17,18,[21][22][23][25][26][27]: consequently, arterial as citic fluid pH gradient values were higher in patients with than in those without SBP. The arterial ascitic fluid pH gradient was higher than 0.10 in about 70% of patients with SBP and the specificity of this index for the diag nosis of SBP was about 98% [11,17,18,21,22,25,26]. These results show that an ar terial ascitic fluid pH gradient >0.10 is a reliable index of SBP.…”

“…Ascitic fluid pH levels lower than 7.35 had a sensitivity of 60% [11,17,18,21,22,25,26] and a specificity higher than 95% [11,17,18,21,22,25,26], In order to improve the sensitivity of this in dex, arterial-ascitic fluid pH gradient has been studied. Arterial pH values were simi lar in patients with and without SBP [11,17,18,[21][22][23][25][26][27]: consequently, arterial as citic fluid pH gradient values were higher in patients with than in those without SBP. The arterial ascitic fluid pH gradient was higher than 0.10 in about 70% of patients with SBP and the specificity of this index for the diag nosis of SBP was about 98% [11,17,18,21,22,25,26].…”