MRI demonstration of peritoneal implants.

The magnetic resonance imaging (MRI) findings of 12 proven cases of peritoneal implants, mainly carcinomatosis, were reviewed for evidence of peritoneal seedings. The seeded sites include the pouch of Douglas, the ileocecal and retrocecal regions, the right and left paracolic gutters, Morison's pouch, the right subdiaphragmatic parietal peritoneum, the greater and lesser omentum, the gastrocolic, gastrosplenic, and phrenicocolic ligaments, the small bowel mesentery, the sigmoid and transverse mesocolons, and the small and large bowel walls. Sizes varied from less than 1 cm to omental cake and bulky tumors. The findings include linear or tiny nodular infiltrations of the omentum and subperitoneal fat (ligamentous, mesenteric, and mesocolic), focal or segmental wall thickenings, loss of unilateral colonic haustration with sacculation on the contralateral side, and nodular soft tissue masses along different locations of the peritoneal surfaces. Air was introduced via an antegrade or retrograde method to act as a gastrointestinal contrast agent and was found to be useful for delineating the seedings. As is true with computed tomography scan, miliary implants are also not detectable with MRI. The sensitivity and specificity of MRI in detecting peritoneal implants remain to be determined.