What is the differential diagnosis for a patient with a history of internal hemorrhoids (IH) and constipation, now presenting with intermittent rectal mass and requiring manual reduction towards the vaginal wall to defecate, after normal endoscopy findings?

Differential Diagnosis: Posterior Compartment Pelvic Floor Disorder

This patient most likely has a rectocele or internal rectal intussusception (occult rectal prolapse), given the need for manual vaginal wall pressure to defecate and normal endoscopy findings. 1

Primary Diagnostic Considerations

Rectocele (Most Likely)

• Presents with bulging of the posterior vaginal wall requiring manual pressure (splinting) to evacuate stool 1
• Approximately one-third of patients with posterior vaginal wall bulging have rectoceles 1
• Normal endoscopy is expected, as rectoceles are structural defects of the rectovaginal septum, not mucosal abnormalities 1
• The ACR guidelines specifically note that rectoceles require imaging (not endoscopy) for diagnosis 1

Internal Rectal Intussusception (Occult Rectal Prolapse)

• Can simulate a rectocele clinically and requires defecography to differentiate 1, 2
• Involves infolding of the rectal wall into its lumen, which may be full-thickness or partial 1
• 39 of 52 patients (75%) with rectal prolapse in one series had internal (occult) prolapse that simulated either rectocele or enterocele 2
• Frequently coexists with other pelvic floor defects and may be missed on physical examination alone 2
• Normal endoscopy is typical because the prolapse is functional/positional rather than a fixed mucosal abnormality 1

Enterocele or Sigmoidocele

• Herniation of peritoneal contents (small bowel or sigmoid) into the rectovaginal space 1
• Can present with posterior vaginal bulging similar to rectocele 1
• Physical examination detects only 51% of enteroceles compared to imaging 1
• Requires imaging with contrast opacification to distinguish from rectocele 1

Less Likely but Important Considerations

Pelvic Floor Dyssynergia

• Inability to coordinate pelvic floor muscle relaxation during defecation 1, 3
• However, this patient's constipation resolved with fiber/water, making pure dyssynergia less likely 3
• Can coexist with structural abnormalities 3, 4

Recommended Diagnostic Approach

Immediate Next Step: Dynamic Imaging

Fluoroscopic cystocolpoproctography (defecography) is the initial imaging test of choice 1

• Sensitivity of 94% for rectoceles and 88% for internal rectal prolapse 1
• Directly visualizes the defecation process and identifies structural abnormalities that physical examination misses 1
• Can differentiate rectocele from enterocele/sigmoidocele, which both present with posterior vaginal bulging 1
• Detects clinically occult abnormalities: physical examination detected only 7% of rectoceles found on defecography in one study 1

Alternative: MR Defecography

• Provides excellent morphological and functional display of the entire pelvic floor 5
• Useful when multiple compartment defects are suspected 5
• Over 50% of postmenopausal women have associated dysfunctions in other compartments 5

Critical Clinical Pearls

Why Endoscopy Was Normal

• Structural pelvic floor disorders (rectocele, intussusception, enterocele) are mechanical/positional problems, not mucosal pathology 1
• Endoscopy evaluates the mucosal surface but cannot assess the dynamic function or structural support of the pelvic floor 1
• The ACR guidelines explicitly state that imaging, not endoscopy, is required for these diagnoses 1

The Vaginal Splinting Sign

• Manual pressure toward the vaginal wall to facilitate defecation is pathognomonic for posterior compartment prolapse 1, 2
• This finding strongly suggests either rectocele or occult rectal prolapse 2
• Cannot be adequately assessed by static examination or endoscopy 1

Common Pitfall to Avoid

• Do not assume the hemorrhoid banding resolved all pathology 2
• Internal rectal prolapse frequently coexists with hemorrhoids and may be unmasked after hemorrhoid treatment 2
• The mean number of prior pelvic floor surgeries before diagnosing occult rectal prolapse was 1.5 in one series 2

Management Implications

Before Considering Surgery

• Biofeedback therapy should be attempted first, as dyssynergic defecation may coexist with structural abnormalities 3, 4
• Accurate assessment of the entire pelvis is mandatory before surgical intervention 3
• Rectocele repair should only be considered after conservative measures fail and if definitively established as the cause 4