الفهرس 
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Abstract
Involvement of the peritoneum, omentum, and mesentery can be due to primary and secondary neoplastic and non neoplastic conditions. Differentiation of neoplastic involvement of the omentum from benign causes of omental thickening can be a challenge in the clinical practice. Ultrasound allows the detection and characterization of such lesions. Pulsed and color Doppler sonography have been used with the attempt to differentiate benign from malignant tumors of various origin by assessing tumor neovascularity.
Image-guided peritoneal and omental core biopsy can be safely done for determining the tumor type.
The aim of our work was to study different peritoneal diseases (benign, malignant) and causes ascites of undetermined etiologies, using conventional trans-abdominal U/S and duplex Doppler U/S in a trial to have criteria for differentiation between these diseases.
Our study included thirty patients with ascites due to peritoneal or omental pathology, 24 patients were females and 6 were males. All patients were subjected to thorough history taking, clinical examination, laboratory investigations, and trans-abdominal ultrasonography using low and high frequency probe.
Color Doppler and duplex Doppler U/S was applied over the omental lesions in attempt to differentiate benign lesions from malignant ones, and U/S-guided biopsy was taken from extra visceral lesions for histopathological examination. According to the histopathological examination of obtained omental biopsy, patients were divided into two groups; patients with ascites of benign etiology, and patients with ascites of malignant etiology. U/S-guided biopsy was done safely and no complications were reported. U/S guided biopsy could achieve 100% sensitivity and specificity in the detection of malignant and non malignant lesions. It was well tolerated, and resulted in no complications, no cases of peritonitis or hemorrhage were recorded. Eleven patients proved to have benign pathology, all had tuberculous peritonitis. Nineteen patients proved to have malignant lesions (Metastatic adenocarcinoma, Non-Hodgkin`s lymphoma, Pseudomyoma peritonei, Malignant mesothelioma). Patients with ascites due to peritoneal carcinomatosis lie in an older age group than those with ascites due to benign etiologies.
Certain ultrasound criteria were found to be significantly different between bengn and malignant omental lesion:
- Omental thickness was significantly higher in malignant lesions than benign lesions (3.07 cm, versus 1.85 cm), with a best cut-off value at 1.6 cm with 94.4% sensitivity, 63% specificity, 81.8 positive predictive value, and 86.9 negative predictive value. . - Omentum with heterogenous texture was detected in (68.4%) of malignant lesions versus 0 (0%) in benign lesions, whereas echogenic homogenous omentum was more common in benign lesions (100%) versus (26.3%) in malignant lesions, which was statistically highly significant (P value 0.001).
- By using color Doppler and duplex Doppler U/S, we found that maximum velocity (Vmax.) and mean velocity (Vmean) flow parameters of thickened omentum were significantly higher in malignant lesions than benign one, at best cut-off value 19.1 cm/sec. with 84.2% sensitivity, and 81.8% specificity for Vmax., and best cut-off value 7.8 cm/sec. with 94.7% sensitivity, and 81.8% specificity for Vmean. Pulsatility indices (PI) and resistive indices (RI) of omental vasculature shows no significant difference between these lesions.