What is pseudomyxoma peritonei, and what are its CT and MR imaging features?
Pseudomyxoma peritonei is a rare condition where mucinous ascites arises from rupture of a mucinous appendiceal adenoma. It has a strong association with synchronous or metachronous colorectal adenoma and carcinoma, such that surveillance of the entire large bowel is warranted. Loculated ascites is typically seen with low attenuation, low-intermediate signal intensity on T1-weighted images, and high signal intensity on T2-weighted images relative to skeletal muscle. Thickened walls, internal septations, and scalloping of parenchymal organs such as the liver and spleen are often seen, sometimes with very high attenuation calcifications. However, lymphadenopathy and distant metastatic disease are absent.