Radiological Investigations in Uterine (Pelvic Organ) Prolapse

"A comprehensive history and physical examination with the POPQ system are usually sufficient to properly assess the degree of prolapse. Most patients require little additional testing. Radiology studies to establish the extent or to characterize a patient's prolapse are generally unnecessary." - Campbell-Walsh-Wein Urology

1. Ultrasound

A. Pelvic Ultrasound (Transabdominal / Transvaginal)

• Identifies pelvic organ abnormalities (fibroid uterus, adnexal masses) that may contribute to prolapse or influence surgical planning.
• Detects mesh or sling location in patients with prior anti-incontinence or prolapse surgery.
• The use of ultrasound to evaluate the specific anatomic defect in POP is considered investigational by most authorities.
• Campbell-Walsh-Wein Urology notes ultrasound is useful to "identify pelvic organ abnormalities and identify possible mesh in the pelvis in patients with prior surgeries for prolapse or incontinence."

B. Transperineal / Translabial Ultrasound (TPUS)

• Performed by placing a 5-MHz curved array probe between the labia majora - minimally invasive, does not distort pelvic anatomy.
• Allows real-time visualization of the anterior, central, and posterior compartments of the female pelvis.
• Assesses the urethra, bladder neck mobility, pelvic support structures at rest and with Valsalva maneuver.
• Can quantify changes in morphology with straining - useful to document bladder base descent, uterine descent, and posterior compartment defects.
• Excellent for identifying sling/mesh complications (erosion, sling failure, de-novo voiding dysfunction) because synthetic materials are highly echogenic.
• 2D and 3D/4D modalities are available; 3D ultrasound can define levator hiatal dimensions and levator ani integrity.
• Does NOT require radiation and is noninvasive - advantage over fluoroscopy.
• Per StatPearls - Pelvic Prolapse Imaging: translabial ultrasound is a "valuable tool for complicated multicompartment pelvic prolapse when physical examination is often difficult."

C. Endoanal Ultrasound (EAUS)

• Used mainly when fecal incontinence or anal sphincter defects co-exist with prolapse.
• May reveal external anal sphincter defects not visible on clinical examination.

2. Fluoroscopic Studies (Defecography / Cystoproctography)

• Patient placed on a radiolucent commode.
• Contrast material instilled into the rectum (barium paste); addition of vaginal, bladder, and oral contrast is helpful when multicompartmental prolapse is suspected.
• Series of lateral still images or continuous videography obtained at rest, during defecation, and during anal contraction.

• Size of the rectal ampulla, length of the anal canal
• Anorectal angle (at rest and during defecation)
• Puborectalis motion
• Pelvic floor descent
• Severity and location of prolapse quantified relative to the pubococcygeal line

• Enterocele detection - pelvic fluoroscopy is superior to physical examination
• Intussusception - considered the definitive test; preferred for quantifying degree and level of rectal prolapse
• Rectocele, perineal descent, rectosphinteric dyssynergia (anismus)
• Uterine prolapse with incomplete bowel emptying or significant defecatory dysfunction where physical exam and symptom severity do not correlate

3. MRI (Magnetic Resonance Imaging)

A. Static MRI

• Provides detailed soft tissue anatomy of the urethra, striated sphincter, levator ani, and surrounding structures.
• Excellent for detecting levator ani defects (avulsions, muscle atrophy), which strongly predict prolapse recurrence.
• Identifies ballooning of the levator muscles and levator ani hernias.
• Modality of choice for urethral diverticulum diagnosis.
• Berek & Novak's Gynecology: "Static MRI gives detailed information of the urethral anatomy, the striated sphincter, and its surrounding structures."

B. Dynamic MRI / MR Defecography

• Rectal gel (ultrasound gel or specific contrast) instilled rectally ± vaginally.
• Rapid dynamic sequences (e.g., TrueFISP - True Fast Imaging with Steady-State Precession) are used.
• Images obtained at rest, during Valsalva/straining, during squeezing, and during defecation.
• No bowel preparation required.

• Simultaneously evaluates all three pelvic compartments - anterior (bladder, urethra), central (uterus/vaginal apex), and posterior (rectum, anorectum).
• Visualizes and quantifies prolapse in each compartment dynamically during straining.
• Diagnoses enterocele (especially useful with Valsalva/straining views) - resting and straining MRI is "particularly helpful in identifying the presence of enterocele."
• Differentiates mucosal intussusception from full-thickness rectal prolapse.
• Detects pelvic floor dyssynergia (anorectal angle becomes more acute confirming paradoxical puborectalis contraction).
• Measures degree of perineal descent.
• Assesses global pelvic floor anatomy - levator ani, puborectalis, external anal sphincter.
• No ionizing radiation.
• Multiplanar imaging capability, good temporal resolution, excellent soft tissue contrast.

• No radiation exposure.
• Visualizes all three pelvic compartments simultaneously.
• Better soft tissue characterization.
• Detects levator ani defects and pelvic musculature changes.

• Expensive, not widely available.
• Supine position is less physiological (gravity effect on prolapse is reduced) - though open MRI scanners allow upright imaging.
• Lack of standardization, wide range of normal values.
• The International Journal of Radiology & Imaging Technology notes: "MR Defecography has emerged as a modality which additionally images pelvic floor function in real time, combining advantages of previously used modalities with multiplanar imaging, good temporal resolution and lack of radiation exposure."

4. CT Scan

• Limited role in the primary evaluation of prolapse.
• Not suitable for dynamic assessment.
• Occasionally used post-operatively to assess complications (e.g., mesh complications, hematoma).
• Grainger & Allison's Diagnostic Radiology confirms "MRI remains the cross-sectional radiological technique of choice for pelvic imaging" for benign pelvic floor dysfunction.

5. Intravenous Urography (IVU) / Renal Ultrasound

• While not a first-line investigation specifically for prolapse diagnosis, renal/ureteral assessment is relevant in:
  • Advanced (Stage III-IV) uterine prolapse where ureteral kinking can cause hydronephrosis (reported in up to 10-15% of severe prolapse cases).
  • Pre-operative workup to document upper tract status.
  • Renal ultrasound is the preferred less invasive alternative to IVU to check for hydronephrosis/hydroureter before surgery.

6. Urodynamics (Functional Investigation)

• Evaluates concurrent stress urinary incontinence and bladder function.
• Identifies occult/masked stress incontinence that may be unmasked after prolapse repair.
• Guides surgical planning when both prolapse and incontinence are present.
• Fluoroscopic component visualizes the bladder and urethrovesical junction dynamically.

Summary Table