In one line
A genitourinary fistula is an abnormal epithelialised communication between the urinary tract and the genital tract that produces continuous, position-independent urinary leakage; in South Africa the dominant cause is still obstetric — ischaemic pressure necrosis from prolonged obstructed labour — and the single most important principle is that the first repair is the best chance of cure, so a fistula belongs with an experienced fistula surgeon who has staged it properly, not with whoever is on call.
The mechanism, the pathology and the simple bedside diagnosis are the groundwork; revise them at gynaecological fistulas. The consultant task here is to classify the defect accurately, decide when and by what route to operate, anticipate residual incontinence after an anatomically successful closure, and own the prevention chain that should make the disease disappear.
Mechanism & pathophysiology
Three aetiological mechanisms produce a genitourinary fistula, and they behave so differently that lumping them together is the commonest conceptual error.
Obstetric (ischaemic) fistula is a pressure injury. During prolonged obstructed labour the fetal head is impacted against the maternal pelvis, and the soft tissues of the bladder base, urethra, anterior vaginal wall and — posteriorly — the rectovaginal septum are crushed between the head and the symphysis or sacrum. Sustained compression for hours to days produces ischaemia, then pressure necrosis; the devitalised tissue sloughs several days postpartum, leaving a defect. This is why the classic obstetric fistula is not a clean surgical hole but a zone of avascular, fibrotic, scarred tissue, often with substantial loss of bladder and urethral substance, frequently bordering or involving the urethral closure mechanism and sometimes circumferential — the urethra effectively amputated from the bladder. The same ischaemic field explains the cluster of associated injuries that define the obstructed labour injury complex: vesicovaginal and/or rectovaginal fistula, urethral loss, vaginal stenosis, secondary infertility, foot-drop from lumbosacral plexus compression, and amenorrhoea. The fetus is almost always stillborn. The woman is characteristically young, short-statured, primiparous and poor, delivered late and far from emergency care — the fistula is the anatomical fossil of the three delays (deciding to seek care, reaching care, receiving care).
A crucial corollary, often missed: caesarean section does not abolish the risk if the labour was already long. By the time an obstructed labour reaches theatre the ischaemic insult to the bladder base may already be complete, so a fistula can still appear after a caesarean delivery — district data show fistulae occurring despite caesarean access precisely because the compression preceded the operation (Loposso 2015). The prevention target is therefore timely caesarean, not caesarean per se.
Iatrogenic (surgical) fistula is a different lesion. Here the bladder or ureter is injured directly — most often at hysterectomy (the classic post-hysterectomy vesicovaginal fistula presenting with leakage 1–2 weeks postoperatively as a devascularised suture line breaks down or an unrecognised cystotomy declares itself), at caesarean section, or at caesarean hysterectomy for placenta accreta. The tissue is otherwise healthy, the defect is usually small, high in the vaginal vault, and clean-edged, and the prognosis for closure is correspondingly excellent. Ureteric injury (ureterovaginal fistula) is the iatrogenic lesion that masquerades as a bladder fistula and must be actively excluded, because it leaks urine vaginally while the bladder fills and voids normally — a fundamentally different operation.
Malignant and radiation fistula is the third mechanism and the one that changes the entire plan. A fistula arising in a field of advanced or recurrent cervical, vaginal or bladder cancer, or in a pelvis that has had radiotherapy, is not a primary repair problem: the tissue is tumour-bearing or radiation-damaged and ischaemic, simple closure fails, and the priorities become tissue diagnosis (biopsy the edges — never assume), oncological staging, and usually urinary diversion or interposition rather than layered repair. Treating a malignant fistula as if it were an obstetric one wastes the patient's time and the surgeon's credibility.
Parity shapes the obstetric lesion in a way worth holding for the operating plan: primiparous women tend to develop distal fistulae with more scarring (the head sits low and long), while multiparous women tend toward proximal defects (Lorencz 2016). Distal and scarred is the harder, more incontinence-prone repair.
Hold one more pathophysiological distinction because it dictates whether continence is even achievable. The continence mechanism is the urethra plus the bladder neck and their support; an obstetric fistula that destroys this — a circumferential defect where the urethra is detached from the bladder, or one that takes out most of the urethral length — can be anatomically closed (the urinary tract made watertight) while leaving no functioning sphincter, so the woman is dry of the fistula but wet from sphincteric incontinence. By contrast, a high vesicovaginal or vesicocervical fistula that spares the urethra and bladder neck, once closed, leaves a continent woman. This is the physiological reason the site of the defect, not its size, is the strongest outcome lever, and why every classification that matters anchors on distance-from-the-meatus or urethral involvement.
Assessment
The history is usually diagnostic. Continuous, uncontrollable urinary leakage that wets the patient day and night and is independent of activity or position points to a fistula; leakage only on effort points to stress incontinence and a leak that comes and goes with urgency points to an overactive bladder — neither produces the constant wetness of a fistula. Date the leak against the index event: onset immediately or within days of an obstructed labour is obstetric; onset 1–2 weeks after a hysterectomy is iatrogenic. Take a full obstetric history (duration of labour, place and mode of delivery, fetal outcome), and screen deliberately for the rest of the injury complex — faecal leakage (rectovaginal fistula), difficulty walking (foot-drop), amenorrhoea, and the social devastation that is part of the diagnosis.
Examination is done in good light with the patient in the lithotomy or knee–chest position, and often it should be examination under anaesthesia when scarring, pain or a high defect prevents an adequate office assessment. Define:
- The site (vesicovaginal, urethrovaginal, vesicocervical, ureterovaginal, rectovaginal — and note that multiple defects coexist), the size, and the distance of the distal edge from the external urinary meatus (the basis of the Goh type).
- The state of the surrounding tissue — fibrosis, vaginal length and capacity, and whether the defect is circumferential (the urethra/bladder neck completely detached), because these, more than size, drive both the difficulty of repair and the risk of post-closure incontinence.
- Urethral length and competence, the single most prognostically loaded feature: urethral involvement independently predicts both failed closure and persistent incontinence after closure (Maljaars 2023).
- Associated injuries — a digital and, where available, endoanal assessment of the anal sphincter, and a neurological check for foot-drop.
The dye test (three-swab test) is the bedside investigation that localises and confirms a urinary fistula and distinguishes a vesical from a ureteric source. Three swabs are placed in the vagina (high, mid, low), the bladder is instilled with dilute methylene blue (or indigo carmine) through a catheter, and the swabs are inspected: blue staining of the upper/mid swabs confirms a vesicovaginal fistula; clear wetting of the top swab with no dye signals urine entering above the bladder — a ureterovaginal fistula — and mandates upper-tract imaging. A "double-dye" variant (oral phenazopyridine colouring renal urine orange while methylene blue fills the bladder) separates the two sources in one test.