Ultrasound-guided biopsy of greater omentum: an effective method to trace the origin of unclear ascites.

OBJECTIVES: Thickened greater omentum is encountered with high frequency in patients with ascites. The purpose of our study was to assess the utility of greater omentum biopsy under the guidance of ultrasound (US) in tracing the origin of unclear ascites and differentiating benign and malignant ascites.

MATERIALS AND METHODS: We retrospectively reviewed our institutional database for all records of greater omentum biopsy cases. One hundred and ninety-four patients with unclear ascites and thickened greater omentum were included in the study. The sonograms of greater omentum were evaluated before undergoing the ultrasound-guided biopsy and a biopsy was considered successful if a specific benign or malignant diagnosis was rendered by the pathologist.

RESULTS: Successful biopsy was rendered for 182 biopsy procedures (93.8%, 182/194) including tuberculosis (n=114), chronic inflammation (n=3), metastases (n=58), malignant mesothelioma (n=6) and pseudomyxoma peritonei (n=1). Twelve biopsies were non-diagnostic. According to the results of biopsy and follow-up, the sensitivity and specificity of biopsy in distinguishing malignant ascites from benign ascities were respectively 95.6% (65/68) and 92.9% (117/126). The greater omentum of 84 cases of tuberculous peritonitis showed "cerebral fissure" sign and was well seen as an omental cake infiltrated with irregular nodules when involved by carcinomatosis. No "cerebral fissure" sign was observed in peritoneal carcinomatosis. The sensitivity and specificity of this sign in indicating the existence of tuberculous peritonitis were 73.5% (89/121) and 100% (73/73). Moreover, if the specific "cerebral fissure" sign was combined with the biopsy results, the specificity of biopsy in distinguishing malignant ascites from benign ascits increased to 96.8% (122/126).

CONCLUSION: Ultrasound-guided biopsy of greater omentum is an important and effective method to diagnose the unclear ascites for patients with thickened omentum if certain techniques could be paid attention to. "Cerebral fissure" sign of greater omentum was a specific sign in indicating the tuberculous peritonitis and could increase the specificity of biopsy in distinguishing malignant ascites from benign ascits if combined with the biopsy results.