Causes of Rectovaginal Fistula
Obstetric or vaginal trauma is by far the most common cause of rectovaginal fistula, accounting for 88% of cases, followed by Crohn's disease at approximately 9%. 1
Primary Etiologies (in order of frequency)
1. Obstetric/Vaginal Trauma (88%)
- Birth injuries during vaginal delivery
- Episiotomy complications
- Fourth-degree perineal tears
- Sexual trauma (including non-consensual anal penetration) 2
2. Crohn's Disease (9%)
- Part of perianal fistulizing Crohn's disease phenotype
- Prevalence of perianal disease in Crohn's ranges 20-40% 3
- Associated with significant morbidity and requires multidisciplinary management 4, 5
3. Iatrogenic Causes
- Rectal surgery complications (including hemorrhoid surgery) 6
- Anastomotic leakage after low rectal surgery 7
- Radiation therapy for pelvic malignancies 1
4. Pelvic Infections - INCLUDING PARASITES
Yes, parasitic infections can cause rectovaginal fistulas. The ACR guidelines specifically list schistosomiasis as a recognized infectious cause 1. Other infectious causes include:
- Schistosomiasis (parasitic)
- Tuberculosis 8
- Diverticulitis
- Lymphogranuloma venereum
- Human papilloma virus
- HIV-related infections
- Cytomegalovirus
5. Malignancy
- Anorectal cancers
- Perineal malignancies
- Gynecologic organ cancers
- Approximately 11% of colovaginal fistulae are caused by malignancy 1
Critical Clinical Pitfalls
Always consider malignancy when imaging shows soft tissue mass, mass-like wall thickening, or malignant-appearing lymphadenopathy - even when evaluating for presumed benign inflammatory disease 1. In chronic perianal Crohn's disease with fistulas, there is increased risk of squamous cell carcinoma, basal cell carcinoma, and adenocarcinoma developing in chronic fistula tracts 4.
In young patients without apparent risk factors living in TB-endemic areas, consider tuberculosis - it can present atypically as rectovaginal fistula even in nulliparous women without pulmonary TB history 8.
Anatomic Classification
Rectovaginal fistulae are subclassified as:
- High fistulas: Communications to rectum proximal to anal sphincter, often involving posterior vaginal fornix
- Low fistulas (anovaginal): Communications from anal sphincter complex to lower half of vagina 1
This distinction is crucial for surgical planning and predicting outcomes.