Obstetric

The underlying factors responsible for the development of obstetric fistulae may be considered in physical, biosocial, cultural, and geographical or political terms. The basic physical factors responsible for obstetric fistula development include obstructed labour, accidental injury at the time of caesarean section, forceps delivery, craniotomy, symphysiotomy, traditional surgical practices including circumcision and ‘gishiri’, and complications of criminal abortion.

The overwhelming majority are complications of neglected obstructed labour. During normal labour, the bladder is displaced upwards and the anterior vaginal wall, bladder base and urethra are compressed between the fetal head and the posterior surface of the pubis. No harm results if this occurs for a short time, but in prolonged obstructed labour, the intervening tissues are devitalized by ischaemia. Usually, the anterior vaginal wall and underlying bladder neck are affected, although the area of necrosis is sometimes higher, in which case the anterior lip of the cervix and underlying trigone are involved. Compression of the soft tissues between the sacral promontory and the presenting part may occur at the same time, with necrosis at the posterior vaginal wall and underlying rectum. The devitalized area separates as a slough usually between the third and 10th day of the puerperium, with resulting incontinence (Figure 57.2).

Figure 57.2 Puerperal patient following prolonged obstructed labour. An area of devitalized tissue is seen on the anterior vaginal wall, about to slough with resultant fistula formation.

Accidental injury to the vaginal wall during a difficult operative delivery may involve damage to the underlying bladder wall, particularly if the tissues are devitalized by prolonged pressure. Forcible rotation of the head with Kielland’s forceps is particularly liable to produce such an injury by shearing stresses. The bladder is particularly exposed to injury following symphysiotomy if the pubic bones are too widely separated by forced abduction of the thighs. In these circumstances, the unsupported bladder neck is very likely to be damaged, especially if the head is rotated and extracted with forceps. The posterior wall of the bladder may be accidentally incised during lower segment caesarean section or repair of ruptured uterus, particularly if the bladder is not reflected sufficiently far downwards before the lower segment is opened. During the reflection itself, the bladder may be torn, especially if a previous operation has made it densely adherent to the lower segment. If the bladder injury goes undetected at the time, urinary leakage through the abdominal wound soon develops. This is usually followed by incontinence vaginally when the urine finds its way through the uterine incision. The abdominal leakage then dries up as the bladder drains through the resulting vesicocervical fistula. Alternatively, sutures may be passed through the posterior bladder wall during repair of the uterine incision. The appearance of urinary incontinence in these cases is delayed until the intervening bladder tissue caught up in the suture sloughs.

The perineum and posterior vaginal wall are, of course, at risk from even the most straightforward delivery, although primiparity, forceps delivery, birth weight over 4 kg and occipitoposterior position have been found to be significant risk factors associated with third-degree tears (Sultan et al 1994). Even when identified and repaired, this increases the risk of rectovaginal fistula.

Traditional surgical practices are undertaken in up to 98% of women in some parts of Africa (United Nations Population Fund 2007, World Health Organization 2008), and may play a role in the aetiology of both direct ‘surgical’ and obstetric fistulae. The practices of ‘angurya’ and ‘gishiri’ cutting [female genital mutilation (FGM) type IV] (World Health Organization 2008) are commonly employed to treat a wide variety of conditions including obstructed labour, infertility, dyspareunia, dysuria, amenorrhoea, goitre, backache and presumed tumour. The traditional cut made with a razor blade or knife through the vaginal introitus is sometimes superficial, but may result in fistula formation (Figure 57.3). Since cuts are usually made by linear incision into healthy tissues, repair is often much easier than for those resulting from pressure necrosis. Tahzib (1983, 1985) reported on the epidemiological determinants of vesicovaginal fistulae in northern Nigeria. In 84% of cases, obstructed labour was the major aetiological factor, 33% had undergone ‘gishiri’, and this was felt to be the main aetiological factor in 15%.

Figure 57.3 Vesicovaginal fistula resulting from ‘gishiri’ cutting (female genital mutilation type IV).

Female circumcision has been practised in various forms in much of North Africa, being most prevalent in Ethiopia, Eritrea, Sudan, Egypt, Mali and Guinea, where currently over 75% of women are affected (World Health Organization 2008). The more extreme forms (previously referred to as ‘pharaonic circumcision’) involve removal of the labial minora (FGM type IIa), and may include removal of the clitoris (FGM type IIb) and labia majora (FGM type IIc) (see Figure 57.4). In FGM type III, the introitus may be reduced to pin-hole size by excision and apposition of the cut edges of the labia minora or majora (infibulation) (World Health Organization 2008). Whilst an association between FGM and both vesicovaginal and rectovaginal fistula is recognized (Lovel et al 2000), the strength of the association and the exact mechanisms are less certain and are currently under investigation (World Health Organization 2008).

Figure 57.4 Excisional type of female genital mutilation, with excision of labia minora and most of clitoris and labia majora (female genital mutilation type IIc).

In considering obstetric fistulae, it is important to consider the social, cultural and geographical influences just as much as the direct physical injury to the lower urinary tract. Obstructed labour is most often due to a contracted pelvis. This usually results from stunting of growth by malnutrition and untreated infections in childhood and adolescence. Where women retain a subservient role in society and standards of education are limited, early marriage and the absence of family planning services result in an early start to childbearing; where first pregnancies occur soon after the menarche, before growth of the pelvis is complete, this also contributes to obstruction in labour.

The influence of these factors is illustrated in the epidemiological studies alluded to earlier. Tahzib (1983) reported that over 50% of the cases of vesicovaginal fistulae seen in northern Nigeria were under 20 years of age, over 50% were in their first pregnancy, and only one in 500 had received any formal education. From the same area, Murphy (1981) reported that 88% of patients had married at 15 years of age or less, and 33% had delivered their first child before the age of 15 years. However, in different developing world societies, these factors do seem to have variable influence. For example, in south-east Nigeria (Hilton and Ward 1998) and the north-west frontier of Pakistan (World Health Organization 1989), fistula patients seem to be somewhat older and of higher parity; they also appear to have a higher literacy rate, and to be more likely to remain in a married relationship after the development of their fistula (Hilton and Ward 1998). It is likely that the development of fistulae here reflects other biosocial variations (Table 57.2). It is clear that in these populations, even where skilled maternity care is available, uptake may be poor. Mistrust of hospitals is commonplace, antenatal care is poorly attended, and delivery is commonly conducted at home by elderly relatives or unskilled traditional birth attendants. Where labour is prolonged, transfer to hospital may only be used as a last resort.

Table 57.2 Epidemiological aspects of obstetric fistula as illustrated in five studies from Nigeria, Ethiopia and Pakistan

Surgical

Genital fistula may occur following a wide range of surgical procedures within the pelvis (Table 57.1, Figure 57.5A–F). It is often supposed that this complication results from direct injury to the lower urinary tract at the time of operation. Certainly, on occasions, this may be the case; careless, hurried or rough surgical technique makes injury to the lower urinary tract much more likely. However, of 300 fistulae referred to the author in the UK over the last 20 years, 207 have been associated with pelvic surgery and 147 followed hysterectomy; of these, only seven presented with leakage of urine on the first postoperative day. In other cases, compromise to the blood supply may result in tissue necrosis and subsequent leakage; alternatively, a small pelvic haematoma may develop in association with the vaginal vault, which subsequently becomes infected and discharges with the characteristic puff of haematuria 5–10 days later, with incontinence following shortly thereafter. Recent animal studies suggest that the inadvertent placement of vault sutures into the bladder wall at hysterectomy may not carry as great a risk of fistula formation as previously thought (Meeks et al 1997).

Figure 57.5 Urogenital fistulae of varying aetiologies: (A) following anterior colporrhaphy, (B) urethral diverticulectomy, (C) radical hysterectomy, (D) midurethral tape procedure for stress incontinence, (E) colposuspension (the fistula in the latter case was fixed retropubically in the midline at the bladder neck, and the photograph shows the patient prone, in the reverse lithotomy position), (F) subtrigonal phenol injection, (G) radiotherapy for carcinoma of cervix.

Although it is important to remember that the majority of surgical fistulae follow apparently straightforward hysterectomy in skilled hands, several risk factors may be identified that make direct injury more likely (Table 57.3). Obviously, anatomical distortion within the pelvis by ovarian tumour or fibroid will increase surgical difficulty, and abnormal adhesions between bladder and uterus or cervix following previous surgery or associated with previous sepsis, endometriosis or malignancy may make fistula formation more likely. Preoperative or early postoperative radiotherapy may decrease vascularity, and make the tissues generally less forgiving of poor technique.

Table 57.3 Risk factors for postoperative fistulae

Issues of training and surgical technique are, of course, also important. The ability to locate and, if necessary, dissect out the ureter must be part of routine gynaecological training, as should the first aid management of lower urinary tract injury when it arises. The use of gauze swabs to separate the bladder from the cervix at caesarean section or hysterectomy should be discouraged; sharp dissection with knife or scissors does less harm, especially where the tissues are abnormally adherent.

It has recently been shown that there is a high incidence of abnormalities of lower urinary tract function in fistula patients (Hilton 1998); whether these abnormalities antedate the surgery, or develop with or as a consequence of the fistula, cannot be answered from this data. However, it is likely that patients with a habit of infrequent voiding, or with inefficient detrusor contractility, may be at increased risk of postoperative urinary retention; if this is not recognized early and managed appropriately, the risk of fistula formation may be increased.

Radiation

As noted above, preoperative pelvic irradiation increases the risk of postoperative fistula development, but irradiation itself may be a cause of fistula (Figure 57.5G). The obliterative endarteritis associated with ionizing radiation in therapeutic dosage proceeds over many years, and may be aetiological in fistula formation long after the primary malignancy has been treated. Of the 28 radiation fistulae in the author’s series, the fistulae developed at intervals between 1 and 30 years following radiotherapy. Not only does this ischaemia produce the fistulae, it also causes significant damage in the adjacent tissues, so ordinary surgical repair has a high likelihood of failure and modified surgical techniques are required.

Malignancy

The treatment of pelvic malignancy by either surgery or radiotherapy is associated with a risk of fistula development, but tissue loss associated with malignant disease itself may result in genital tract fistula. Carcinoma of cervix, vagina and rectum are the most common malignancies to present in this way. It is relatively unusual for urothelial tumours to present with fistula formation, other than following surgery or radiotherapy. The development of a fistula may be a distressing part of the terminal phase of malignant disease; it is, nevertheless, one deserving not simply compassion but full consideration of the therapeutic or palliative possibilities.

Inflammatory bowel disease

Inflammatory bowel disease is the most significant cause of intestinogenital fistulae in the UK, although these rarely present directly to the gynaecologist. Crohn’s disease is by far the most important, and appears to be increasing in frequency in the Western world. A total fistula rate approaching 40% has been reported, and the involvement of the genital tract in females may be up to 7%.

Ulcerative colitis has a small incidence of low rectovaginal fistulae. Diverticular disease can produce colovaginal fistulae and, rarely, colouterine fistulae, with surprisingly few symptoms attributable to the intestinal pathology. The possibility should not be overlooked if an elderly woman complains of feculent discharge or becomes incontinent without concomitant urinary problems (Figure 57.6).

Figure 57.6 Barium enema from patient complaining of vaginal discharge; demonstrates extensive diverticular disease and obvious colovaginal fistula.

Miscellaneous

Among other miscellaneous causes of fistulae in the genital tract, the following should be considered.

• Infection

Lymphogranuloma venereum

Schistosomiasis

Tuberculosis

Actinomycosis

Measles

Noma vaginae

• Other

Penetrating trauma

Coital injury

Neglected pessary

Other foreign body

Catheter-related injury

United Kingdom

The prevalence of genital fistulae obviously varies from country to country and continent to continent as the main causative factors vary. Accurate figures are impossible to obtain since those areas with the highest overall prevalence are also those with the poorest systems of health data collection. UK National Health Service data reported approximately 150 operations for vesicovaginal and urethrovaginal fistula per year in England and Wales in the early 1990s (Hilton 1997). The most recent data from Health Episode Statistics for England suggest an average of 95 operations for vesicovaginal fistula and 10 operations for urethrovaginal fistula per year in England (Department of Health 2009). It is tempting to suggest that this apparent reduction in incidence of fistulae may reflect changes in the practice of hysterectomy. However, assuming that 50% of urogenital fistulae in the UK follow hysterectomy (as in the author’s series), the rate of fistula formation following hysterectomy seems, if anything, to be increasing; from approximately one in 1200 hysterectomies in the period 1990–1991 to 1994–1995 to approximately one in 750 in 2003–2004 to 2007–2008 (Department of Health 2009). Whilst there are other possible explanations, it may be that as fewer hysterectomies are undertaken, those that remain are the more difficult procedures. Studies from Finland suggest a similar rate of posthysterectomy fistulae overall, with approximately one per 1000 abdominal hysterectomies and one per 450 laparoscopic hysterectomies (Harkki-Siren et al 1998). Similarly, ureteric injury may be up to six times as common following laparoscopic hysterectomy compared with open hysterectomy (Harkki-Siren et al 1998), and two to 10 times as common following radical hysterectomy and exenteration (Averette et al 1993, Bladou et al 1995, Emmert and Köhler 1996). Sultan et al (1994) reported that third-degree tears followed 0.6% of vaginal deliveries, and a rectovaginal fistula resulted in 6% of these (one in 3000 deliveries overall).

Developing world

In the developing world, many fistula cases are unknown to medical services, being separated from their husbands and ostracized from society. Although the true prevalence in the developing world is unknown, particularly high prevalence rates are reported in Nigeria, Ethiopia, Sudan and Chad. The estimated prevalence in the developing world is one to two per 1000 deliveries, with perhaps 50,000–100,000 new cases each year. Although several units exist in Nigeria, Ethiopia and Sudan, which deal with 100–700 cases per year, this does not come close to meeting the demand, and there are estimated to be perhaps 500,000 to 2 million untreated cases worldwide (Waaldijk and Armiya’u 1993).