Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (160 page)

   Contrast radiography

   Small bowel series have a low yield in identifying a bleeding source (i.e., a 5% detection rate). This may be increased to 10% with use of enteroclysis. If the bleeding source is a small intestine malignancy, the yield is considerably better.

   Barium studies cannot diagnose angiodysplasias, but they may be useful in identifying mass lesions and mucosal defects.

   Despite the low diagnostic yield, contrast radiography is the initial study in a patient where small intestinal bleeding is suspected (i.e., when the evaluation of upper and lower GI tracts are nondiagnostic).

   Endoscopic studies

   Routine EGD reaches the junction of the second and third portions of the duodenum.

   Conventional push enteroscopy (either a dedicated enteroscope or a pediatric colonoscope) can reach the proximal jejunum. Yield with push enteroscopy varies from 24 to 75% in detecting a bleeding source. Push enteroscopy also has therapeutic value.

   Sonde enteroscopy is a newer procedure that is being developed to visualize the entire jejunum and ileum. It is a flexible fiberoptic instrument carried through the bowel by peristalsis. It is not a routinely available procedure, and it is best reserved for those patients with comorbid conditions that may preclude intraoperative enteroscopy (video capsule endoscopy).

   Angiography detects a bleeding rate of 0.5 mL/minute. It can localize the site of bleeding in 50–72% of cases if bleeding is massive, but in only 25–50% of cases if bleeding has slowed. It has a low yield in diagnosing angiodysplasias and tumors.

   Nuclear imaging

   Technetium-99 bleeding scan may detect bleeding at a rate as slight as 0.1 mL/minute. Like angiography, it is only of value in the setting of active bleeding. It can define a general area of bleeding, but it cannot identify the precise source.

   Technetium-99 Meckel scan, which is taken up by ectopic gastric mucosa in the diverticulum, is not useful if the diverticulum does not contain gastric mucosa.