Nodules, plaques and omental caking on the peritoneal surfaces, with ascites — map it region by region (Peritoneal Cancer Index) because the extent, especially in the small bowel mesentery, decides cytoreductive surgery.
Orient first
- Sites of stasis are hit first: pouch of Douglas, right paracolic gutter, right subphrenic space, the omentum, and the small bowel mesentery.
- The Peritoneal Cancer Index (PCI) scores 13 regions 0–3 by lesion size (verify the scheme your surgeons use).
- CT underestimates small (< 5 mm) deposits and small bowel serosal disease.
Acquire the study
- Portal venous phase, 1–2 mm reconstructions, coronal and sagittal reformats; positive or water oral contrast helps separate bowel.
The manoeuvre
- Omentum on axial and coronal reformats: stranding, nodules, confluent cake — size in cm.
- Coronal reformats: right subphrenic space and liver surface scalloping; the pouch of Douglas; paracolic gutters.
- Small bowel mesentery on the portal venous phase: stellate thickening, bowel tethering.
- Ascites: loculated vs free; enhancement of the parietal peritoneum.
- Score the PCI regions if the case is for cytoreduction.
What confirms it
- Peritoneal nodules or omental cake with ascites in a patient with a known or suspected primary; cytology or biopsy confirms.
What licenses you to exclude it
- A normal CT cannot exclude small-volume peritoneal disease; laparoscopy is the reference.
The classic misread
- Missing subtle subdiaphragmatic deposits because ascites is read as normal fluid.