List five causes of colonic thumbprinting.

Smooth folds (as a result of fluid accumulation)
1. Hemorrhage
2. Ischemic edema
3. Inflammatory edema (e.g., as a result of pseudomembranous colitis, idiopathic colitis, diverticulitis, pancreatitis, typhlitis)

Irregular folds (as a result of cell infiltration)
4. Lymphoma
5. Metastatic lesions