What tests are needed for a patient with a colostomy to determine if they are a candidate for takedown or reversal of the colostomy?

Pre-Takedown Evaluation for Colostomy Reversal

Before proceeding with colostomy takedown, patients require water-soluble contrast enema or CT with rectal contrast to confirm anastomotic integrity and absence of stricture, along with endoscopic evaluation (colonoscopy or sigmoidoscopy) to assess distal bowel patency and exclude active inflammation. 1

Essential Diagnostic Tests

Contrast Studies (Primary Assessment)

• Water-soluble contrast enema is routinely performed prior to ileostomy or colostomy takedown to detect anastomotic leaks, strictures, fistulas, and sinus tracts 1
• This fluoroscopic study demonstrates 80% sensitivity and 95.7% specificity for small-bowel and inlet strictures, though only 50% sensitivity for pouch leaks 1
• In one study, 14% of patients had clinically significant occult strictures detected by contrast enema that would have complicated reversal 1
• CT with rectal contrast serves as an alternative or complementary study, showing 91% sensitivity and 100% specificity for detecting anastomotic complications 1

Endoscopic Evaluation

• Digital rectal examination combined with colonoscopy or sigmoidoscopy is essential to assess the distal bowel segment 1
• Endoscopy directly visualizes the anastomosis or rectal stump, identifies strictures, and confirms absence of active inflammation 1
• Some centers use endoscopy as the primary evaluation method, as pathology detected on contrast studies is equally identified on clinical examination and endoscopy 1

Cross-Sectional Imaging

• CT abdomen and pelvis with contrast should be obtained to evaluate for parastomal hernia, intra-abdominal abscess, or other complications that would complicate reversal 2
• MRI pelvis with gadolinium provides superior soft tissue resolution for evaluating anastomotic integrity and detecting occult fistulas or abscesses, particularly in complex cases 1

Timing Considerations Before Testing

• Allow 3-6 months after initial surgery before considering reversal to ensure adequate healing and resolution of inflammation 3
• For patients who received pelvic radiation (such as anal cancer patients), wait at least 8-12 weeks after completion of chemoradiotherapy before assessment, as complete response may take up to 26 weeks 1
• Confirm physiological stability including resolution of the acute condition, adequate nutritional status, and normal electrolyte levels before proceeding with evaluation 3

Special Population Considerations

Anal Cancer Patients

• Most pre-treatment colostomies become permanent due to high radiation doses to anal sphincters causing persistent incontinence or stenosis 1
• Reversal should only be considered if the anorectum is functionally intact after treatment, which is the exception rather than the rule 1, 3
• Assessment at 8-12 weeks post-chemoradiotherapy includes digital rectal examination and anoscopic evaluation 1

Inflammatory Bowel Disease

• For perianal Crohn's disease with fecal diversion, only 16.6% achieve successful reversal, with most diversions becoming permanent 3
• Ensure complete resolution of inflammation before considering reversal, which may require longer than the standard 3-6 month interval 3

Critical Pitfalls to Avoid

• Do not proceed without contrast study or endoscopy: Occult strictures or leaks will lead to immediate postoperative complications 1
• Avoid premature reversal before 2-3 months: Inadequate healing dramatically increases anastomotic leak risk 3
• Do not assume radiation-treated bowels are functional: High-dose pelvic radiation causes permanent sphincter dysfunction in most cases 1
• Screen for parastomal hernia before reversal: Concurrent hernia repair significantly increases morbidity (39% vs 25% complication rate) and may warrant staged approach 4

Algorithm for Proceeding

1. Confirm adequate time interval (minimum 3 months, longer for radiation or inflammatory conditions) 3
2. Obtain water-soluble contrast enema to screen for stricture, leak, or fistula 1
3. Perform colonoscopy/sigmoidoscopy to directly visualize distal bowel and confirm patency 1
4. Order CT abdomen/pelvis if parastomal hernia suspected or complex anatomy anticipated 2
5. Proceed only if: no leak, no significant stricture, patent distal bowel, and resolved inflammation 1, 3