Comparison of Different Ascitic Fluid Collection Methods for the Diagnosis of Spontaneous Bacterial Peritonitis in Cirrhotic Rats

Abstract

To test for the best method of collecting ascitic fluid for the diagnosis of spontaneous bacterial peritonitis, carbon tetrachloride was administered in 120 rats for 6-18 weeks to induce infected cirrhotic ascites. Only 58 cirrhotic rats survived with ascitic fluid ≥3 ml for cell counts and cultures. These rats were randomly divided into 4 groups to compare the methods of ascitic fluid collection: group A, paracentesis; group B, direct laparotomy; group C, rapid decapitation followed by laparotomy; and group D, the intubation method. In 13 rats in which paracentesis was performed, ascitic fluid ≥3 ml was only successfully withdrawn in 7 rats and the amount of ascitic fluid was much less than they really had. Among 52 cirrhotic rats from which ascitic fluid was successfully withdrawn, 10 had infected ascites and 42 had sterile ascites. Of 42 rats with sterile cirrhotic ascites, ascitic fluid red cell counts were significantly greater in group B (3.88±4.12xl0^5cells/mm^3) than in group A (0.14±0.31x10^5cells/mm^3, p＜0.01), C (0.18±0.l9xl0^5cells/mm^3, p＜0.01) orD (0.12±0.1410^5cells/mm^3, p＜0.01). Ascitic fluid neutrophil counts and ratio were significantly greater in group B(1667±2336cells/mm^3, 15.0±19.3%) than in group C (76±103cells/mm^3, 4.2±3.0%, p＜0.05)orD (36±33 cells/mm^3, 3.8±2.8%, p＜0.05). Of 42 rats with sterile cirrhotic ascites, ascitic fluid neutrophil counts were greater than 250 cells / mm^3 in 0, 6, 1 and 0 of group A, B, C and D (p ＜0.01), respectively; and greater than 500 cells/mm^3 in 0, 5, 0and 0 (p＜0.0l). In conclusion, rapid decapitation followed by laparotomy and the intubation method are the two best methods in collecting ascitic fluid for the rat model of spontaneous bacterial peritonitis. Since blood specimens obtained from rapid decapitation followed by laparotomy are not aseptic, the intubation method may be the best way for further experiments when simultaneous collection of aseptic blood and ascitic fluid specimens is needed.