What is a small bowel follow-through (SBFT)?

What is Small Bowel Follow-Through (SBFT)?

Small bowel follow-through (SBFT) is a fluoroscopic radiographic examination where a patient ingests oral contrast (typically barium sulfate or water-soluble contrast) and serial X-ray images are obtained over time to visualize the small intestine as contrast progresses from the stomach through the jejunum and ileum to the colon. 1

Technical Procedure

• Contrast administration: The patient ingests 340-750 mL of barium sulfate suspension (either undiluted or diluted 1:1 with water) or water-soluble contrast agents like diatrizoate meglumine 2, 1
• Image acquisition: Serial radiographs are obtained at timed intervals (typically every 15-30 minutes) to track contrast progression through the small bowel 1
• Fluoroscopic monitoring: Manual or mechanical compression of bowel segments is performed during the examination to separate overlapping loops and improve visualization 1
• Completion: Large-format images are captured when the entire small bowel is adequately filled and distended 1

Historical Context and Declining Role

SBFT has been largely replaced by cross-sectional imaging modalities (MR enterography and CT enterography) due to superior diagnostic accuracy. 1, 3

• The two-dimensional perspective of SBFT results in pathology being obscured by overlapping bowel loops, limiting detection of active disease 1, 3
• SBFT allows accurate intraluminal and mucosal assessment but cannot directly visualize bowel wall thickness 1
• Extraluminal pathologies including abscesses can only be indirectly inferred, leading to decreased detection 1
• In pediatric inflammatory bowel disease patients, SBFT demonstrated sensitivity of only 76% and specificity of 67%, compared to MRI with 83% sensitivity and 95% specificity 1

Current Limited Clinical Applications

Water-Soluble Contrast Challenge in Small Bowel Obstruction

The primary remaining indication for SBFT is the water-soluble contrast challenge to predict need for surgery in adhesive small bowel obstruction. 1, 3

• Protocol: 100 mL of hyperosmolar iodinated contrast (such as diatrizoate meglumine diluted in 50 mL water) is administered orally or via nasogastric tube 1
• Imaging timing: Follow-up radiographs at 8 hours and 24 hours after administration 1, 4
• Interpretation: If contrast reaches the colon by 24 hours, patients rarely require surgery and can be managed conservatively 1, 3
• Clinical benefit: Early SBFT reduces time to operative intervention (1.0 days vs 3.7 days) and time to nonoperative resolution (1.8 days vs 4.7 days) 4

Problem-Solving in Specific Scenarios

• Fistula evaluation: SBFT may visualize internal fistulas and can be useful for cutaneous fistula assessment 1
• Preoperative anatomy: Limited role in delineating anatomy for surgeons, though this use has markedly declined 1, 3
• Sedation avoidance: May serve as alternative to MRI/CT in young children when sedation must be avoided 1

Critical Contraindications

Barium-based SBFT is absolutely contraindicated in suspected or confirmed bowel perforation due to risk of severe chemical peritonitis. 5, 3

• Water-soluble contrast should be used instead if perforation is suspected 1
• SBFT should not be performed when high-grade obstruction is suspected, as it provides inadequate information for surgical decision-making 3

Potential Complications

• Aspiration pneumonia: Can occur if contrast is administered before adequate gastric decompression 1
• Pulmonary edema: Rare complication from water-soluble contrast agents 1
• Dehydration and shock: Hyperosmolar water-soluble agents shift fluid into bowel lumen, potentially causing hypovolemia in children and elderly patients 1
• Anaphylactoid reactions: Rare but reported with oral contrast media 1
• Radiation exposure: Significant concern, particularly with repeated examinations in chronic diseases 1

Preferred Alternative Modalities

Modern guidelines recommend capsule endoscopy, MR enterography, or CT enterography over SBFT for most small bowel evaluations. 3, 6

• Capsule endoscopy: Superior to SBFT for detecting small bowel inflammation (detected 107 of 110 lesions vs 63 lesions with SBFT plus ileocolonoscopy) and should be the initial test after negative ileocolonoscopy 6, 3
• MR enterography: Preferred for inflammatory bowel disease assessment due to superior soft-tissue contrast, ability to visualize extramural complications, and lack of radiation 1, 3
• CT enterography: Alternative when MRI is not available or patient cannot tolerate MRI examination 1

Common Pitfalls

• Low specificity: SBFT has poor specificity for Crohn's disease, as small lesions may represent other conditions 3
• Operator dependence: Diagnostic accuracy is highly dependent on radiologist experience and technique 1
• Incomplete evaluation: Cannot assess for transmural disease extent or detect extramural complications like abscesses 1
• Overlapping loops: Two-dimensional imaging leads to missed pathology when bowel loops overlap 1, 3