Metastasis

Metastatic disease of the small bowel entails cancerous growth within the small bowel arising secondarily from malignancy elsewhere in the body.  In-as-much, metastases are most often multiple (although they can be solitary).

Metastatic spread can occur through a number of routes. Hematogenous spread involves seeding of the bowel through the blood. This most often occurs with melanoma (most common), lung, breast, and kidney. Lymphatic spread, or spread through the lymph channels, occurs most commonly with colon cancer. Metastatic deposits can develop on the serosal (outer) surface of the bowel through intraperitoneal seeding, seen most commonly in ovarian and colon cancer. Finally, cancers from adjacent organs such as the pancreas can invade the small bowel through contiguous spread.

Trying to classify radiographic appearances of metastatic disease is not worth the effort, unless you have hours to devote to the memorization of grocery lists of differential diagnoses. Similar to lymphoma, metastases can do just about anything to the small bowel. That should be easy enough to remember.   

Metastatic melanoma. Separation of bowel loops by a large extrinsic mass in metastatic melanoma (left). Multiple large luminal filling defects in metastatic melanoma (right).