There are small enhancing peritoneal soft tissue nodules in the omentum on the left side. These were not present on the preoperative imaging.
These were initially missed but eventually diagnosed on 1 year follow-up when the peritoneal implants grew larger and more numerous. The likely cause is spillage of tumor into the peritoneal cavity during nephrectomy.
Discussion
There are several reasons why these peritoneal implants were initially missed
- Attribution bias occurs when specific characteristics are attributed to something simply because it belongs to a certain class. In other words, intraperitoneal dissemination is not a well recognized pathway for the spread of renal cell carcinoma. Therefore, radiologists typically do not look for peritoneal implants in this setting and are at increased risk of missing them when present.
- Exam was performed only 6 months postoperatively with no evidence of metastatic disease on preoperative imaging. Most radiologists would not expect to find metastatic disease this soon, which could lead them to be less vigilant.
- Small size: remember that 60-80% of diagnostic errors in imaging are perceptual errors, meaning that they are not seen. Smaller lesions are by definition more difficult to find.
The most common places for missed metastatic disease on CT of the abdomen and pelvis is liver, bone, and peritoneal surface. These areas should be carefully checked for every patient with cancer. Cancers outside the peritoneal cavity can metastasize to an intra-abdominal site and then spread intraperitoneally.
