Any of the small intestinal malignancies may ulcerate and bleed into the bowel lumen. Blood loss is generally not massive and may be occult. Leiomyosarcomas may be particularly vascular and may be a cause of gross bleeding with melena or grossly bloody stools. Tumors proximal to the ligament of Treitz occasionally cause hematemesis if they bleed rapidly.
Small bowel malignancies may narrow the intestinal lumen, creating partial obstruction that may cause cramping abdominal pain accompanied by loud peristaltic rushes and abdominal distention. Small bowel adenocarcinomas tend to create a ringlike constriction similar to that created by colonic adenocarcinomas. Small bowel tumors may also act as a lead point for an intussusception, producing intermittent obstruction. Higher grades of obstruction cause backing up of bowel contents, with nausea and vomiting; the vomiting may be feculent if the obstruction is in the distal small intestine and associated with stasis.
Weight loss may be a prominent feature of small bowel malignancies. Malignant tumors in the abdomen frequently cause anorexia and decreased caloric intake. Abdominal pain caused by partial bowel obstruction may be exacerbated by food intake, contributing to anorexia. Bacterial overgrowth in the obstructed small intestine may be a cause of malabsorption, producing steatorrhea and weight loss. Malabsorption is common with diffusely infiltrating small intestinal lymphomas.
Small bowel malignancies can, on occasion, cause acute abdominal catastrophes such as perforation, massive hemorrhage, or acute intestinal obstruction.