How Vesicouterine Fistula Occurs
Vesicouterine fistula develops primarily through iatrogenic bladder injury during cesarean section, particularly when dissecting the lower uterine segment in women with prior cesarean deliveries or when the bladder is not adequately emptied preoperatively. 1
Primary Mechanism: Surgical Trauma During Cesarean Section
The overwhelming majority of vesicouterine fistulas in the modern era result from cesarean section, representing a dramatic shift from the pre-1947 era when they followed vaginal operative deliveries. 2
Key pathophysiologic steps:
- Direct bladder injury occurs during dissection of the lower uterine segment, especially when adhesions from prior cesarean sections obscure tissue planes 1
- The injury may be unrecognized intraoperatively in at least 95% of cases, leading to delayed diagnosis and requiring subsequent surgical repair 1
- Inadequate bladder emptying before surgery increases the risk of inadvertent injury during uterine incision 1
Risk Factors That Increase Fistula Formation
Prior Cesarean Section
- Women with previous cesarean sections have altered anatomy with scar tissue and adhesions that make bladder dissection more hazardous 1
- The risk compounds with multiple cesarean deliveries, as cesarean scar defects (niches) occur in 24-88% of women with prior cesarean sections 3
Complicated Deliveries
- Vacuum delivery in women with prior cesarean section creates particularly high risk, as demonstrated in case reports where the combination of operative vaginal delivery and scarred tissue led to fistula formation 4
- Prolonged or obstructed labor requiring emergency cesarean section increases the likelihood of difficult dissection 1
Timing of Fistula Development
Vesicouterine fistulas manifest along different timelines:
- Immediate postoperative period: Fistulas may develop within days of cesarean section when bladder injury occurs 5
- Late puerperium: Some fistulas become apparent weeks to months after delivery 1
- After repeated procedures: Multiple cesarean sections progressively increase risk through cumulative scarring 1
Clinical Presentation Patterns
The modern presentation differs markedly from historical cases:
- Cyclic hematuria (menouria) with amenorrhea is the hallmark symptom, occurring when menstrual blood flows through the fistula into the bladder rather than through the cervix 1, 2
- Urinary incontinence may be the sole presenting symptom, as demonstrated in recent case reports 5
- Vaginal urinary leakage occurs when urine passes from bladder through uterus and out the cervix 1
- Only 5% heal spontaneously, making intervention necessary in the vast majority 1
Critical Intraoperative Risk Factors
Prevention requires specific attention to:
- Bladder emptying with catheterization before making the uterine incision 1
- Careful dissection of the lower uterine segment, particularly in women with prior cesarean sections where the bladder may be adherent to the anterior uterine wall 1
- Intraoperative monitoring for bloody urine in the Foley catheter, which should prompt immediate investigation for bladder injury 1
Common Pitfall
The most significant clinical pitfall is failure to recognize bladder injury intraoperatively, which occurs in at least 95% of cases. 1 This leads to delayed diagnosis, prolonged symptoms that impair quality of life, and the necessity for a second operation. Intraoperative sonography via transvaginal or transrectal route has been proposed to detect injuries immediately when bloody urine appears in the catheter or when bladder injury is suspected during dissection. 1