Predictive value of omental thickness on ultrasonography for diagnosis of unexplained ascites, an Egyptian centre study

Abstract

Etiology of ascites of unknown origin varies with geographic area and ethnic origin. Tuberculous peritonitis and peritoneal carcinomatosis constitute a considerable proportion of patients. Differentiation between both is a major challenge. The role of omental thickness (OT) by ultrasonography to predict risk of malignancy in unexplained ascites. This prospective study was done at Kasr Alainy School of Medicine, Cairo University and included 100 adults with unexplained ascites and thickened omentum (>15 mm) on ultrasonography. An expert performed ultrasonography to assess peritoneum and peritoneal cavity and measure OT. Ascites was assessed regarding volume, echogenicity, and loculation. The ascitic fluid was analyzed to measure lactate dehydrogenase, adenosine deaminase, and total leukocytic count. Laparoscopic exploration with biopsy was done for final diagnosis that divided the patients into; TB Group (n = 44) and peritoneal carcinomatosis group (n = 56). Main Outcome Measures were to determine degree of omental thickness as a predictor of malignancy risk in unexplained ascites and other ultrasonographic features to predict malignancy risk including omental echogenicity and results of diagnostic ascitic tapping. We found that OT was greater in the PC group compared to the TB group (24.6 ± 4.6 mm vs. 17.9 ± 3.0 mm, respectively, p < 0.001). Higher frequency of hypoechogenicity, irregular peritoneal surface, omental cakes, and lymph nodes was seen in PC Group. ADA, TLC, and relative lymphocyte count were higher in TB group. Omental thickness ≥19.5 mm has a sensitivity of 89.3%, specificity of 84.1% to diagnose PC. We can conclude that omental thickness >19 mm is a sensitive and specific predictor of malignancy in patients with unexplained ascites.

Keywords: Ascites; Omental thickness; Ultrasonographic.