Rectovaginal fistula

Aetiology:

• Obstetric - most common
  • 3% of 3rd and 4th degree perineal tears go on to develop rectovaginal fistula
  • Often a/w anterior anal sphincter defects
• Crohn's disease
  • Up to 10% of all female Crohn's patients
  • High recurrence rate in this population
  • Amost all will require EUA before a decision is made about formal repair
  • Optimise medical therapy - fistula may resolve with immunologics
• Iatrogenic
  • Surgery
    • Fistulotomy
    • Hysterectomy, rectocoele repair, LAR, prolapse/haemorrhoidectomy
  • Radiotherapy
    • Ensure to rule out malignancy with biopsies
• Neoplasia
  • Anal
  • Rectal
  • Vaginal
  • Cervical
• Infectious
  • Cryptoglandular abscess
  • Diverticulitis
  • TB

Presentation

• Passage of stool or gas via vagina
• Recurrent UTI
• Dyspareunia
• Vaginal discharge

Exam

• DRE - indurated fistula tract
• Anoscopy or vaginal speculum exam - granulation tissue often visible - gentle probing often reveals tract
• Tampon test - put in a tampon, then give methylene blue dye enema, and walk around for 20 minutes. If tampon goes blue, a fistula is highly suspected.
• If patient has IBD, EUA is generally necessary to define tract and evaluate for degree of inflammation

Principles of pre-op workup: identify fistula, determine the cause, evaluate extent of disease, and identify surrounding structures

Investigation:

• MRI
• Endoanal USS
• Pelvic floor physiologic testing (anorectal manometry) - indicated when suspicion for anal sphincter injury or fecal incontinence, which may impede recovery post-repair
• Colonoscopy/CT depending on aetiology

Classification

• According to their relation to the sphincter complex
  • High: above
  • Low: at or below (also referred to as anovaginal)
    • Almost always caused by obstetric trauma
• Alternatively:
  • Simple: middle or lower portion of rectovaginal septum, <2.5cm in diameter, and caused by local trauma or infection
  • Complex: >2.5cm, upper portion of rectovaginal septum, secondary to causes other than trauma and infection

Pre-op

• Phosphate enema morning of procedure

Surgical management:

• Local sepsis is an absolute contraindication to repair - may need to drain abscesses, treat infection (?seton), and wait
• Delay 3-6 months after birth if that is the cause, to allow local inflammation to subside and fibrosis to develop
• Transanal
  • Fistulotomy
    • Two-stage: first, place seton; then, lay open tract
    • Risks sphincter damage and incontinence
    • Very rarely used today
  • Endorectal advancement flap
    • Indicated in low vaginal fistulas, without sphincter defects
    • Good to perform repair from high-pressure side of fistula
    • Preserves sphincter
    • Performed transanally. Raise flap, excise fistula, close.
    • Complications: flap failure, ischaemia
    • Post-op: high-fibre diet, stool softeners, sitz baths
  • Fibrin glue
  • Bioprosthetics
    • Very limited experience
• Transvaginal
  • Vaginal advancement flap
    • Similar to rectal advancement flap
    • Advantage is that you use healthy, pliable, well-vascularised vaginal tissue to close the fistula
    • Disadvantage - closure is on the low-pressure side of the fistula
    • Can be advantageous to go vaginal when anorectal stenosis is present, e.g. in Crohn's disease - studies show no difference in orifice chosen
    • Also good if anal advancement flap has already failed once
• Transperineal
  • Episioproctotomy and layered closure
    • Converts fistula in a fourth-degree perineal tear by dividing all the tissue between the rectum and the vagina through the perineal body
    • Layers
      • Rectal mucosa
      • Rectal and vaginal muscular walls
      • Vaginal mucosa
    • Dehischence risks significant incontinence - worse than pre-op - since a full-thickness defect is being created
    • Should only be attempted by experienced surgeons
  • Transperineal ligation with a LIFT procedure, overlapping sphincteroplasty
  • Interposition flaps
    • Most commonly gracilis and bulbocavernosus flaps
    • Feval diversion generally undertaken prior
• Transabdominal
  • Rectal resection/advancement
    • Indicated in circumferential or stricturing disease (Crohn's) or for high/complex fistulae
  • Primary repair with omental interposition
    • Best suited for high fistulae or those with multiple failed transanal/vaginal/perineal approaches