Laboratory and Other Diagnostic Tests
Patients with small intestinal tumors may be anemic and have occult blood in their stools. They may be hypoalbuminemic as a result of protein loss from the tumor and obstruction of lymphatics, especially patients with lymphomas that may infiltrate the mesentery. Malabsorption may produce excess fat in the stool, abnormal Schilling and D-xylose test results, prolonged prothrombin time, and low serum calcium and magnesium concentrations.
Most malignant tumors of the small intestine can be detected in carefully performed barium contrast studies. A common error in evaluating patients with abdominal symptoms is to perform only a barium enema and upper gastrointestinal series. These examinations usually demonstrate only the most proximal and distal small bowel loops; therefore a small intestinal series should be performed. The detection of small lesions in the small intestine by barium radiographic study requires a skilled, interested, and attentive radiologist. The use of enteroclysis, or small bowel enema, can provide increased accuracy. In this more invasive technique, barium is instilled directly into the intestine by passage of a tube through the nose or mouth.
Duodenal tumors may be detected and biopsy specimens obtained by upper gastrointestinal endoscopy. Modern fiberscopes may reach the third portion of the duodenum, and longer enteroscopes have been developed. Most of the jejenum can be examined with “push”-type enteroscopes that allow biopsy, and even the ileum can be seen using “sonde” enteroscopes, which rely on peristalsis for passage but have no biopsy capability. Tumors of the terminal ileum may be revealed in some patients if the ileocecal valve is passed with a colonoscope. Peroral biopsy via tubes passed under fluoroscopic control may obtain a biopsy specimen of small bowel malignancy, particularly in diffuse or multifocal lymphoma. Frequently the diagnosis of small bowel malignancy is made by the surgeon at the time of laparotomy, by palpation, and by biopsy.