Background: The pathologic accumulation of fluid in the peritoneal cavity, which is named ascites, is observed in different diseases. Paracentesis is used to diagnose the causes. The difference of albumin concentration between ascitic fluid and simultaneous blood serum less than 1.1 g/dl, indicated low gradient ascites. Regarding the importance of low gradient ascites causes, this study proposed to find causes of this type of ascites in Rasht in a 7 –year period.

Materials and Methods: This cross sectional study was done according to the data, which were obtained from the recorded files of referral patients to two hospital of Rasht from 1993 to 2000. The type of ascites was determined by albumin concentration between ascitic fluid and simultaneous blood serum. Ascitic fluid Glucose and LDH were measured in the patients too. A data form including Patients’ demographic information and final diagnosis was prepared. Thereafter, the data were analyzed using SPSS 10 software.

Results: Of 148 studied patients there were 72 (48.6%) males and 76 (51.4%) females with the mean age of 56.03 ± 13.54. The most frequent causes of low gradient ascites were tuberculous peritonitis (68, 45.9%) and cancers (62, 41.9%). Of cases, 12.2 % were associated with other causes. Type of low gradient ascites didn’t show any significant differences between male and female groups, but age groups had significant differences (p<0.0001). The mean Serum-Ascites Albumin Gradient (SAAG) and LDH were 0.68 ± 0.19 and 342.38± 135.46, respectively. Mean ascitic fluid Glucose of peritoneal tuberculosis (TB), malignancies and others were 71 ± 13.82, 101.4 ± 17.21, 89.16 ± 13.15 mg/dl respectively and these differences were significant (P<0.001).

Conclusion: In our area in patients with low gradient ascites, it is necessary to rule out TB, this treatable disease, at first. Afterwards we do other diagnostic tests such as ascitic fluid glucose and LDH, for diagnosis of malignancies and then other causes.