What is a Defecogram?
A defecogram (also called defecography or cystocolpoproctography) is a dynamic fluoroscopic or MRI imaging study that evaluates the rectum, anal canal, and pelvic floor in real-time during simulated defecation, used primarily to diagnose structural and functional abnormalities causing chronic constipation, fecal incontinence, or pelvic floor dysfunction. 1, 2
Procedure Overview
What the Test Evaluates
Defecography directly images the process of rectal evacuation and identifies both structural and functional abnormalities that cannot be detected by physical examination alone 1:
- Structural abnormalities: rectocele, enterocele, sigmoidocele, rectal intussusception, rectal prolapse 1, 3
- Functional disorders: pelvic floor dyssynergia (paradoxical sphincter contraction), impaired evacuation, abnormal anorectal angle changes 1
- Clinically occult findings: approximately one-third of patients with posterior vaginal wall bulging have enteroceles or sigmoidoceles not detected on physical examination 1
Two Main Modalities
Fluoroscopic defecography (conventional cystocolpoproctography) remains the gold standard and is one of the initial imaging tests of choice 1, 3:
- Uses thick barium paste (consistency of normal stool) inserted into the rectum 2, 4
- Patient sits on a radiolucent commode during imaging 4, 5
- Real-time fluoroscopic recording during rest, straining, and evacuation 2, 3
- Oral contrast given beforehand helps detect enteroceles 1
MR defecography is also an initial imaging test of choice with distinct advantages 1:
- Superior soft-tissue contrast allows direct visualization of pelvic organs, muscles, and fascia 1
- Detects multicompartment defects and clinically occult abnormalities in 34% of cases 1
- Requires rectal contrast gel and imaging during actual defecation (not just straining) for optimal diagnostic yield 1
- Most centers perform supine MR defecography due to lack of open magnets, though this may underestimate some findings 1
Preparation for the Procedure
Pre-Procedure Requirements
For fluoroscopic defecography 1:
- Oral contrast administration (typically given 30-60 minutes before) to opacify small bowel for enterocele detection 1
- Rectal instillation of thick barium paste to simulate stool consistency 2, 4
- Bladder may be filled with contrast to assess anterior compartment 1
For MR defecography 1:
- Rectal contrast gel instillation is essential 1
- Patient must be able to perform defecation maneuvers during imaging 1
Critical Technical Points
- Complete rectal emptying is essential: A significant proportion of enteroceles appear only after complete evacuation or on post-defecation strain images 1
- Multiple defecation attempts: Patients should perform repeated strain/defecation maneuvers to maximize detection of pelvic floor dysfunction 1
- Post-evacuation imaging: Additional maximal Valsalva imaging after complete rectal emptying is necessary to detect cul-de-sac hernias like enteroceles 1
Post-Procedure Management
Immediate Post-Procedure Care
- No specific post-procedure restrictions are mentioned in the guidelines for diagnostic defecography [1-1]
- Standard barium elimination precautions apply (increased fluid intake, monitoring for constipation from residual barium)
When Surgical Intervention Follows
If defecography identifies structural abnormalities requiring surgical correction 6:
- Bowel management with stool softeners is recommended during recovery to prevent straining 6
- Surgical approach selection depends on patient factors: abdominal approaches have lower recurrence rates (0-8%) but higher morbidity; perineal approaches suit elderly or high-risk patients but have higher recurrence (5-21%) 6
Diagnostic Performance
Comparison to Physical Examination
Defecography detects clinically occult abnormalities that physical examination misses 1:
- Physical examination detected only 7% of rectoceles and 51% of enteroceles seen on fluoroscopic defecography 1
- Fluoroscopic defecography has 94% sensitivity for rectoceles and 35% for enteroceles compared to physical examination 1
- Physical examination misdiagnoses 10% of enteroceles as rectoceles 1
Correlation with Surgical Findings
Fluoroscopic defecography demonstrates 1:
- Excellent correlation for internal rectal prolapse (88% sensitivity) 1
- Good agreement for full-thickness rectal prolapse, rectocele, and peritoneocele (83% sensitivity) 1
MR defecography shows 1:
- Moderate to good correlation with surgical findings for most structural abnormalities 1
- 79% agreement with physical examination for posterior compartment prolapse 1
- Superior detection of enteroceles compared to physical examination (detects 70% more cases) 1
Common Pitfalls and Caveats
Technical Limitations
- Supine MR positioning may underestimate rectal intussusception and rectocele size, though data are conflicting 1
- Dynamic MRI without defecation (straining only) has limited utility and lower detection rates compared to actual defecation imaging 1
- Incomplete rectal evacuation during the study will miss enteroceles and other abnormalities that appear only after emptying 1
Clinical Interpretation
- Dyssynergia detection: Fluoroscopic defecography is sensitive and specific for diagnosing dyssynergia, but meta-analyses show lower prevalence compared to balloon expulsion test and anal manometry 1
- Incidental findings: Defecography commonly reveals multicompartment defects beyond the suspected clinical diagnosis, altering management in significant percentages of patients 1
- Fecal incontinence assessment: Anorectal angle measured on defecography correlates with severity of fecal incontinence 1
When to Choose Which Modality
Fluoroscopic defecography is preferred when 1, 3:
- Evaluating dyssynergic defecation specifically 1
- Resources or patient factors limit MRI access 1
- Established as the reference standard with extensive normative data 3, 7
MR defecography is preferred when 1: