Peritoneal mesotheliomas account for about one-fifth of all mesotheliomas. Like pleural mesothelioma, peritoneal mesothelioma can be either benign or malignant. This discussion is only about malignant peritoneal mesothelioma. Mesothelioma is sometimes diagnosed by coincidence, before any symptoms have appeared. When the symptoms of peritoneal mesothelioma appear, they typically include abdominal pains, weakness, weight loss, loss of appetite, nausea, and abdominal swelling.
Fluid often accumulates in the peritoneal space, a condition known as ascites.
Over time the wasting symptoms can become more and more severe. The growing tumor can exert increasing pressure on the organs in the abdomen, leading to bowel obstruction and distention. If the tumor presses upward, it can impair breathing capacity. If the tumor pushes against areas with many nerve fibers, and the bowel distends, the amount of pain can increase. X-rays and CT scans are, typically, the first step towards detecting peritoneal mesothelioma.