Imaging of peritoneal carcinomatosis with FDG PET-CT: diagnostic patterns, case examples and pitfalls.

Early diagnosis of peritoneal spread in malignant disease is essential to prevent unnecessary laparotomies and to select the patients in whom complete cytoreduction is feasible. Although anatomic imaging is the mainstay for evaluating peritoneal seeding, small neoplastic implants can be difficult to detect with CT and MR imaging. FDG PET-CT has the potential to improve detection of peritoneal metastases as lesion conspicuity is high at PET due to low background activity and fused PET-CT offers the combined benefits of anatomic and functional imaging. Correlation of uptake modalities with the pathogenesis of intraperitoneal spread of malignancies, provides a rational system of analysis and is essential to define disease. Distinct patterns appear to predict the presence of either nodular or diffuse peritoneal pathology. Main pitfalls are related to normal physiologic activity in bowel loops and blood vessels or focal retained activity in ureters and urinary bladder. PET-CT is most suitable in patients with high tumor markers and negative or uncertain conventional imaging data and in selecting patients for complete cytoreduction. FDG PET-CT adds to conventional imaging in the detection and staging of peritoneal carcinomatosis and is a useful diagnostic tool in monitoring response to therapy and in long term follow-up.