Benign tumors include leiomyomas, lipomas, neurofibromas, and fibromas. All may cause abdominal distention, pain, bleeding, diarrhea, and, if obstruction develops, vomiting. Polyps are not as common as in the colon.
Adenocarcinoma, a malignant tumor, is uncommon. Usually it arises in the duodenum or proximal jejunum and causes minimal symptoms. In patients with Crohn disease involving the small-bowel, the tumors tend to occur distally and in bypassed or inflamed loops of bowel.
Carcinoid tumors (also called gastrointestinal neuroendocrine tumors) occur most often in the small bowel, particularly the ileum, and in the appendix; in these locations, larger lesions can become malignant. Multiple tumors occur in 50% of cases. Of those > 2 cm in diameter, 80% have metastasized locally or to the liver by the time of operation. About 30% of small-bowel carcinoids cause obstruction, pain, bleeding, or carcinoid syndrome. Treatment of carcinoid tumors is surgical resection; repeat operations may be required. For metastatic carcinoid tumors, long-acting somatostatin analog therapy with dose escalation, peptide receptor radioligand therapy (PRRT) using a radiolabeled somatostatin analog, or everolimus can be used to effectively control the disease.
Kaposi sarcoma, first described as a disease of elderly Jewish and Italian men, occurs in an aggressive form in Africans, transplant recipients, and AIDS patients, who have gastrointestinal (GI) tract involvement 40 to 60% of the time. Lesions may occur anywhere in the GI tract but usually in the stomach, small bowel, or distal colon. GI lesions usually are asymptomatic, but bleeding, diarrhea, protein-losing enteropathy, and intussusception may occur. Treatment of Kaposi sarcoma depends on the cell type and location and extent of the lesions.
Enteroclysis (sometimes CT enteroclysis) is probably the most common study for mass lesions of the small bowel.
Push endoscopy of the small bowel with an enteroscope may be used to visualize and biopsy tumors.
Video capsule endoscopy can help identify small-bowel lesions, particularly bleeding sites; a swallowed capsule transmits 2 images/second to an external recorder. The original capsule is not useful in the stomach or colon because it tumbles in these larger organs; a colon capsule camera with better optics and illumination is under development for use in these larger-diameter organs.