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.

来历不明的腹水的病因因地域和种族而异。结核性腹膜炎和腹膜癌占相当一部分患者。两者之间的区别是一个重大挑战。超声检查网膜厚度（OT）在预测无法解释的腹水中恶性肿瘤风险中的作用。这项前瞻性研究是在开罗大学Kasr Alainy医学院进行的，超声检查中包括100名原因不明的腹水和大网膜增厚（> 15毫米）的成年人。一位专家进行了超声检查以评估腹膜和腹膜腔并测量OT。评估腹水的体积，回声性和位置。分析腹水以测量乳酸脱氢酶，腺苷脱氨酶和总白细胞计数。进行腹腔镜活检探查以进行最终诊断，将患者分为两个部分：结核病组（n = 44）和腹膜癌病组（n = 56）。主要结果措施是确定网膜厚度的程度，作为无法解释的腹水和其他超声检查特征的恶性风险预测指标，以预测恶性风险，包括网膜回声和诊断性腹水拍打结果。我们发现与TB组相比，PC组的OT值更高（分别为24.6±4.6 mm和17.9±3.0 mm，p <0.001）。在PC组中，出现低回声，腹膜表面不规则，网膜结块和淋巴结的频率更高。TB组的ADA，TLC和相对淋巴细胞计数较高。网膜厚度≥19.5mm的敏感性为89.3％，诊断PC的特异性为84.1％。