Background and AimsUltrasound and computed tomography (CT) scans can be used as methods to help make a more accurate diagnosis in diseases involving the omentum and peritoneum. The present study was conducted to determine etiology and CT scan pattern of peritoneal involvement and compare it with ultrasound findings.MethodsPatients referred to Ghaem and Imam Reza hospitals who had undergone CT scans and had involvement of peritoneum in abdominal CT scans were included in the study. The findings identified in the CT scan were recorded. According to the underlying cause determined by laparotomy or laparoscopy sample, each disease's most common pattern of involvement and types of patterns were examined. An ultrasound was conducted for every patient and the obtained information was analyzed.ResultsA total of 101 patients were included in the study, of which 61 patients (59.8%) were female and the rest were male. The most common involvement patterns in CT scans included nodular (37.6%), mixed (21.8%), and omental cake (17.8%), respectively. In 80 patients (79.2%), CT scan findings were consistent with ultrasound, but in 21 patients (20.8%), CT scan findings were not visible in ultrasound. The most common diagnoses of the patients were colorectal adenocarcinoma and gastric adenocarcinoma (20 cases, 19.8% each), followed by ovarian and uterine adenocarcinoma (19 cases, 18.8%).ConclusionThe most common patterns of involvement of peritoneum in CT scans include nodular pattern, mix, and omental cake. The most common diseases that lead to the involvement of peritoneum are gastrointestinal cancers, uterine and ovarian cancers, and peritonitis.