Diagnostic Approach to Lower GI Bleeding in Infants

Clinical Context and Diagnostic Considerations

The American College of Radiology recommends radioisotope imaging with Tc-99m-labeled RBC scan as the most appropriate initial investigation to confirm the source of bleeding in infants with lower GI bleeding, as it can detect bleeding rates as low as 0.05-0.1 mL/min 1, 2
In infants presenting with severe anemia and hemodynamic instability, urgent localization of the bleeding source is required, and radioisotope imaging is particularly useful for identifying Meckel diverticulum, the most common cause of significant lower GI bleeding in this age group 3, 4

The diagnostic algorithm should start with radioisotope imaging to localize the bleeding source, followed by surgical consultation for resection if Meckel scan is positive, and consideration of CTA as second-line in hemodynamically stable patients if nuclear medicine is negative or unavailable 1, 2, 3, 4
Colonoscopy may be considered if other studies are non-diagnostic, although it can be challenging in this age group 3

Tc-99m-labeled RBC scans are more sensitive than CTA (0.05-0.1 mL/min vs 0.3 mL/min) and angiography (0.5 mL/min) for detecting low-rate bleeding 1, 2
SPECT/CT imaging improves anatomical localization and reduces historical localization errors associated with planar imaging 2
Barium studies are contraindicated in acute GI bleeding evaluation as they obscure active hemorrhage and interfere with subsequent endoscopy or angiography 1, 4, 5, 6

Intermittent bleeding may require repeat imaging if initial study is negative, and recognition of this possibility is crucial for timely diagnosis and treatment 1, 4