Small Intestinal Pathology Detection and Diagnosis

Disease-Specific Prevalence

Isolated proximal small bowel involvement occurs in up to 20% of Crohn's disease patients, making it inaccessible to standard ileocolonoscopy even when terminal ileum intubation is successful 1
In a cohort of 150 Crohn's disease patients with normal ileocolonoscopy, 24% (36 patients) had active small bowel disease diagnosed using CT enterography 1
30% of Gastrointestinal Stromal Tumors (GISTs) are localized to the small intestine, with 60% in the stomach and only 5% in the colon/rectum 2, 3

Capsule endoscopy has a diagnostic yield of 63% for small bowel pathology in patients with obscure GI bleeding after negative EGD and colonoscopy 4
2-3% of patients presenting with iron deficiency anemia have celiac disease detectable only by small bowel biopsy during upper endoscopy 6

For suspected Crohn's disease with negative ileocolonoscopy, obtain cross-sectional imaging (MR enterography or CT enterography) as MRE has 80% sensitivity and 95% specificity for small bowel disease extent 1
Perform capsule endoscopy as soon as possible after negative EGD and colonoscopy for obscure GI bleeding, as this is the recommended next diagnostic step 7
Complete bidirectional endoscopy with small bowel biopsies during upper endoscopy to exclude celiac disease in patients with iron deficiency anemia 6

Terminal ileum intubation may not be possible in all patients, and even when successful, it only visualizes the distal 10-20 cm of small bowel 1
Patency capsule or cross-sectional imaging should be performed before capsule endoscopy in patients with known Crohn's disease or multiple prior resections 8
MR enterography can identify strictures that would contraindicate capsule endoscopy, and has higher sensitivity (73%) and positive predictive value (88%) than capsule endoscopy for small bowel Crohn's disease is not applicable due to [ignore ref], however, capsule endoscopy detects more proximal small bowel lesions compared to cross-sectional imaging 7