Preoperative Peritoneal MRI: Annals of Surgical Oncology | August 2026

Introduction:

Achieving complete cytoreductive surgery (CC-0) is the most important determinant of survival in colorectal cancer with peritoneal metastases (CRC-PM). Previous abdominal surgery may obscure occult peritoneal disease, making preoperative assessment challenging. This study evaluated the role of preoperative peritoneal MRI in detecting hidden metastatic deposits before cytoreductive surgery.

Why was this study needed?

• Complete cytoreductive surgery is essential for long-term survival in CRC with peritoneal metastases.
• Previous moderate or extensive abdominal surgery may conceal residual peritoneal disease.
• Standard imaging may miss lesions in anatomically difficult regions.
• Better preoperative mapping could improve surgical planning and reduce incomplete cytoreduction.
• The value of dedicated peritoneal MRI in this setting remains uncertain.

Results:

• Preoperative peritoneal MRI demonstrated high specificity and good negative predictive value for detecting peritoneal metastases in difficult anatomical locations, making it useful for preoperative surgical planning.
• MRI showed only modest sensitivity, indicating that a negative MRI cannot completely exclude occult peritoneal disease, particularly in previously operated patients.
• MRI identified occult lesions in the inguinal canal and cardiophrenic space, leading to additional resections, with 80% of these lesions confirmed as metastatic disease on pathology.

Clinical Impact:

This study suggests that peritoneal MRI serves as a valuable adjunct to conventional imaging in patients with prior abdominal surgery undergoing cytoreductive surgery for CRC-PM. Although it cannot replace meticulous intraoperative exploration because of its limited sensitivity, MRI may identify otherwise unsuspected metastatic deposits, facilitating more complete cytoreduction and improved operative planning.

Bottom Line:

Preoperative peritoneal MRI improves detection of hidden peritoneal metastases in anatomically challenging regions and enhances surgical planning before cytoreductive surgery. While its high specificity makes positive findings clinically meaningful, its modest sensitivity means it should complement—not replace—careful intraoperative assessment.