24.4.2.1 Ureteral‐Arterial Fistulae

In a brief reminder of ureteric anatomy: the ureters cross the common iliac or proximal portion of the external iliac artery at the level of the pelvic brim. The development of these fistulae tends to be considered a rare iatrogenic complication of usually a combination of features including, pelvic radiotherapy, pelvic surgery, ureteric stenting, or ureterolysis or the presence of prosthetic arterial grafts. The combination or some of these features leads to fistulation by increasing the adherence of the ureter to the underlying iliac vessels and damaging the integrity of those vessels [3]. There are case reports of uretero‐aortal fistulae, but these are much rarer than iliac fistulae. All patients present with haematuria, although this is reported to be significant haemorrhage with haemodynamic instability (defined as ongoing bleeding with a systolic blood pressure of <90) in the majority of cases [3].

Computed tomography (CT) angiography and cystoscopy are the main methods of investigation, although cystoscopy is not appropriate in the presence of life‐threatening haemorrhage (i.e. pulsatile bleeding coming from a ureteric orifice or fresh thrombus around a ureteric stent have been reported cystoscopic findings) [4]. Before the introduction of endovascular intervention in the 2000s, these cases required open surgical repair with either direct surgical arterial repair or arterial bypass grafting. In the last decade, the use of endovascular stents has become the mainstay of management in these patients [3–6]. Without prompt treatment, these fistulas are universally fatal, and even with treatment, these patients face significant morbidity and mortality, although this has improved with the switch to endovascular management.

24.4.2.2 Ureterovaginal Fistula

Fistulae between the ureter and the vagina are an uncommon but well‐recognised complication of hysterectomy and other pelvic operations including Caesarean section. Fistulae have also been described between the ureter and the fallopian tube or uterus. Cases of fistulation have been reported not only from open or laparoscopic gynaecological procedures, but there are also several case reports of ureterovaginal fistulae formation post‐transvaginal ultrasound‐guided extraction of oocytes for fertility treatments [7, 8]. The highest rates of ureteric injuries are found in surgeries for uterine cancers (10%), with similar but lower rates for cervical and ovarian cancers (1–4%), and around 1% for benign surgeries, although this is slightly higher in women undergoing procedures from endometriosis (1.7%) [9].

Whatever the cause of the fistula, the ureter is usually at least partially if not completely obstructed, and the presenting clinical picture is often that of upper tract obstruction (e.g. loin pain, systemic sepsis, acute kidney injury), although sometimes it is more an indolent presentation of recurrent urinary tract infections (UTIs). There can be some immediate leakage of urine from the vagina, although this may or may not be a significant finding on clinical assessment, and if present, is often described as intermittent or positional [10].

CT urography is a useful assessment if a fistula is suspected, although this only illustrates a fistula in around 60% of cases [11]. This may illustrate active leakage of urine into the vagina (or uterus or fallopian tubes); however, it may just show proxy markers of ureteric obstruction; hydronephrosis, stranding around the ureter, urinoma, lack of contrast passage, or hypoperfusion of the kidney. Alternatively, cystoscopy and retrograde pyelography may be of more use to assess the exact level of injury and extent of leakage.

Initial management depends on the clinical condition of the patient and the time since the primary surgical intervention. Prompt diagnosis followed by repair using a Boari flap, psoas hitch, or primary urtero‐neocystostomy gives the best results in the acute setting.

In patients who are profoundly unwell because of urinary sepsis, initial diversion of urine with a nephrostomy may be appropriate, followed by nephrostogram and definitive intervention once any sepsis has resolved. Alternatively, a ureteric stent can be placed for a period as a conservative management strategy. Surgical excision and repair has a success rate of 70–100%, whilst with conservative measures the success rate is around 70% [11–13]. The choice of management strategy must consider previous therapies the patient has undergone; those who have had radiotherapy are likely to have ureteric strictures and the success of conservative measures is usually low due to poor healing, although primary may be more challenging in the postradiotherapy setting. If the lesion has been neglected and the diagnosis is made only after several months, the kidney may be hopelessly damaged by obstruction and necessitate nephrectomy.

24.4.2.3 Ureteroenteric Fistula

Due to the retroperitoneal position of the ureters, fistulae between ureters and bowel are rare. However, they may occur between the ureter and colon or small intestine and occasionally between the ureter and appendix, from which urine enters both the colon and ileum. The most common cause for ureteroenteric fistulae is iatrogenic injuries during abdominal surgery or because of penetrating abdominal trauma [14–17]. Inflammatory bowel conditions such as Crohn disease or diverticulitis can also envelope the ureters in the inflammatory process, although fistulation to the bladder is far more common.

In patients with renal transplants ureteroenteric fistulae can develop as a consequence of chronic rejection many years after transplantation, although there is an earlier peak in incidence in this population within a week of transplantation (due to avascular necrosis of the ureter) [18–21]. There have also been reports of ureteroenteric fistulae developing post‐extracorporeal shock‐wave lithotripsy (ESWL) [22]. Historically, the most common cause for ureteroenteric fistulae were as a complication of tuberculosis [23].

The presenting complaint in these patients can be an indolent history of gastrointestinal disease, previous surgeries, or recurrent UTIs. The main clinical problem arises from absorption of urine leading to hyperchloraemic acidosis. This occurs as the when the bowel epithelium is exposed to urine it reabsorbs the ammonia, hydrogen, and chloride content which does not usually occur with urothelium. To do this it cotransports out sodium and bicarbonate in exchange for hydrogen and chloride, respectively. Symptoms of hyperchloraemic acidosis include high respiration rate, fatigue, nausea and vomiting, confusion, headache, atrial fibrillation, pulmonary oedema, and osteopenia. It is also common for patient to develop renal stones due to the patient becoming hypercalciuric and to see a reduction in urinary citrate levels.

CT imaging of the abdomen and pelvis with contrast and separate delayed urogram phase can be helpful to identify the underlying pathological process and assess for ureteric obstruction, gas may be visible within the renal pelvis; however, often cystoscopy, retrograde pyelography, and ureteroscopy may be required to confirm the presence of a fistula.

Initially it is helpful to insert a nephrostomy, especially if there is hydronephrosis, to allow urinary diversion. This will improve any metabolic disturbance and allow further antegrade imaging to assess for drainage and fistulation and potentially dilate any concomitant ureteric strictures. A ureteric stent can be placed ante‐ or retrogradely. Often, the ultimate management depends on the underlying pathology. In the case of neoplasms, these will generally require surgical excision. For Crohn disease, a trial of antibiotics and immunosuppressants along with ureteric stenting or nephrostomy has been advocated as a conservative approach to these patients [22]. It may be appropriate to trial endoscopic therapies in the first instance; however, surgically, the best management is excision of the diseased segment of bowel and performing a uretero‐ureterostomy or uretero‐neocystostomy [22]. In some instances, it may be required to consider urinary diversion.

24.4.2.4 Ureterocutaneous Fistula

These are very rare fistulae, and there are only a few anecdotal reports within the literature. Most seem to be a consequence of chronic renal tract sepsis, chronic granulomatous diseases, or trauma or iatrogenic injuries [24–26]. If a ureterocutaneous fistula is suspected, the easiest diagnostic test is to check fluid electrolytes to confirm the fluid is indeed urine. Formal CT imaging of the urinary tract is then required to further assess the disease. Nephrostomy drainage allows diversion of urine away from the site of fistula. Depending on the nature of the fistula, further endourological or open surgical approaches may be required to manage any underlying disease process such as obstructing stones.

24.4.3.1 Colovesical Fistula

Colovesical fistulae are most commonly found as a consequence of complicated diverticular disease and seen between the sigmoid colon and bladder; however, they can arise because of a number of common conditions including inflammatory bowel disease (typically, Crohn disease) and colorectal tumours (predominantly sigmoid and rectal tumours). Rarer causes of these fistula include both open and laparoscopic inguinal hernia repair, foreign bodies within the colon (with several reports of fistulae caused by chicken bones), or as a result or appendicitis. There are even reports of fistulae formation after transurethral resection of bladder tumour (TURBT) and Mitomycin C instillation [27–36]. Colovesical fistulae are more commonly seen in men, with the uterus acting as an additional barrier to fistulation in females (although colouterine fistulae can develop).

Often the presentation can be more indolent than with another urological fistula. Patients will often report recurrent UTIs, although some patients will present with recurrent urinary sepsis or pyelonephritis. They may report altered bowel habit and perirectal bleeding if they have active diverticulitis. Classically patients with a colovesical fistula will report pneumaturia, which air bubbles in the urine that bubble throughout the stream. Pneumaturia, however, is often only elicited by direct questioning and infrequently volunteered by patients, although on direct questioning is present in more than 90% of patients [28]. Examination may reveal a tender mass in the lower abdomen, although it is often unremarkable, particularly in patients with a chronic fistula. Urine cultures will contain profuse faecal contamination and can also contain particulate food or faecal matter. Often patients will experience frank haematuria because of severe cystitis.

Definite visualisation of a fistula is notoriously difficult in practice and often patients undergo both radiological and endoscopic evaluation of the bladder and colon. Cystoscopically it is often very difficult to see the fistula, which is usually on the posterior wall or towards the left side of the dome of the bladder because it is often concealed by oedema. Biopsies will confirm the presence of inflammatory infiltrate only but do exclude a bladder malignancy. Pressure over the suprapubic region may cause pus to issue like toothpaste from the fistula, and occasionally faeces and gas are seen to emerge. Occasionally the irrigation fluid will leak perirectally during cystoscopy, although this indicates a significant deficit and can make good views of the bladder difficult.

A formal cystogram may show the communication, but the pressure in the sigmoid is usually much greater than that in the bladder so that the fistula is usually better seen with a contrast enema, typically a CT with intravenous and rectal contrast. This has the benefit of examining the extraluminal features of the organs as well the fistulous tract, although sometimes the only evidence of communication is the presence of air within the bladder; this is relevant in patients who have not had recent bladder instrumentation or catheterisation. It can be difficult to distinguish between complicated diverticular masses and recto‐sigmoid tumours on CT and so many patients will additionally require colonoscopy and biopsy to confirm the underlying pathology.

The treatment then depends on the severity of the inflammation in the pelvis. The classical method was to perform a diverting colostomy, wait three to six weeks, and then carry out a colonic resection. The purpose of defunctioning was purely to aid in the resolution of pelvic sepsis and not aid in the closure of a fistula; the tract must be excised and the primarily affected segment of bowel resected. Today, with antibiotics and a more‐effective and precise preoperative diagnosis, the affected bowel can usually be resected and anastomosis performed in a single stage without the need for any colostomy. Once the affected bowel has been removed, omentum is brought down and interposed between bladder and bowel, and the hole in the bladder is closed in two layers with absorbable sutures and a catheter left indwelling for five or six days. This is possible for more than 90% of patients requiring surgical resection in modern practice [28]. Thought should be given to the ureters in preoperative planning, and it may be useful to cannulate or stent the ureters to delineate anatomy and prevent further iatrogenic injury intraoperatively.

As discussed in the previous section, the only category of fistulae that may improve without surgical input are those as a consequence of Crohn disease. The nature of Crohn disease means that the fistulae can be either small or large bowel in origin, and often the long‐term treatment aim is to preserve as much bowel as possible, particularly if the fistula is vesico‐ileal. Once again, longer‐term antibiotics and immunosuppression may produce resolution without the need for surgery but requires the specialist input of a gastroenterologist.

24.4.3.2 Vesicovaginal Fistula

Vesicovaginal fistulae (VVFs) are often a socially debilitating consequence of a prolonged obstructed labour in low‐resource countries. In countries where emergency obstetric provision is greater, they tend to be due to iatrogenic injuries from gynaecological or pelvic surgeries and radiotherapy. Whilst in Western nations the incidence of VVFs are low at 0.3–2%, it is estimated that in some sub‐Saharan countries the incidence of VVFs is between 1.6–3 per 1000 women [37, 38], and many of these are untreated. Obstructed labour leads to fistulation due to the pressure of the foetus within the true boy pelvis causing pressure necrosis of the bladder and vagina.

Of the iatrogenic injuries that cause VVFs, transabdominal hysterectomy (simple and radical) and transvaginal hysterectomy are the most common, although laparoscopic hysterectomy, colporrhaphy, Caesarean sections, urethral surgery, bladder traumas, periurethral bulking, and anti‐incontinence surgeries are amongst the procedures. Radiotherapy is another frequent cause of VVFs [39]. The mechanism of fistula formation is generally one of tissue ischaemia and necrosis following external pressure (e.g. clamping, clipping), inflammation, and tissue fibrosis or direct puncture or laceration of the urinary tract [10]. Pelvic radiotherapy has a 5% risk of VVF formation even years after radiotherapy. Postradiotherapy fistulas are attributable to persistent small‐vessel arteritis obliterans which reduces blood flow and leads to tissue necrosis [40]. Most VVFs are found at the vaginal cuff post‐hysterectomy.

The main symptom of a vesicovaginal is a painless constant leakage of urine from the vagina, although additionally women may experience recurrent UTIs and local vulval irritation. Examination with a Cusco speculum may reveal pooling of urine, the fistula itself often appears as a raised red granulomatous area with no visible opening. Usually clinical examination and examination under anaesthesia is often satisfactory to diagnose a VVF, but if in doubt, the patient can be injected with methylene blue which is renally excreted and turns urine blue – any blue PV loss confirms the diagnosis. The main differential diagnosis is a uretero‐vaginal or uterine fistula. Upper tract imaging with a CT urogram should be performed regardless because up to a quarter of patients will have hydronephrosis, and there is a risk of concomitant ureterovaginal fistulae [10].

Ultimately the best treatment of VVF is prevention – the provision of adequate emergency obstetric care and good surgical techniques and practices. There are some patients who have small, nonmalignant fistulas in whom conservative management may be appropriate; urethral catheterisation to prevent vaginal leakage, anticholinergic drugs to prevent bladder spams to ensure urine is diverted from the fistula track, and topical oestrogens for postmenopausal women to promote healing. Additionally, it is possible to diathermy and ablate a small fistula via a cystoscope [10].

With regards to surgical management, there are variations in terms of the approaches undertaken. For an uncomplicated VVF post‐surgery then often early closure is as effective as delayed repair. However, for radiotherapy or obstetric fistulae then it has been typically advocated to delay repair to allow for total tissue loss and regeneration to occur, with the aim to repair fistulae in a single procedure. More contemporary data however now supports early repair of obstetric fistulae. The general definition of ‘early’ repair seems to be accepted as within six weeks of injury [19].

There are a variety of techniques to repair VVFs, and often, these are dependent on individual surgeon’s experience. Transvaginal approach is suitable for distal fistulae. The dissection needs to be wide enough to allow for a tension‐free closure, which is performed in three layers with absorbable suture material and must not overlap (i.e. bladder mucosa, perivesical fascia, and undermined vagina or flap). In post‐radiotherapy fistulae or if the tissue quality is poor, a Martius flap may be required (i.e. a vascularised adipose tissue flap with bulbospongiosus muscle from the labium majorum). A transabdominal approach may be required if there is ureteric involvement, and the requirement for uretero‐neocystostomy or a proximal fistula in a deep or narrow vagina. There are several techniques but all involve dissecting off the bladder and excising the fistulous tract. The bladder usually opened to obtain adequate access (either cystotomy to bivalved) to tissue layers and to allow a layered tissue repair (double‐layered closure) and also omentum is interposed to prevent recurrence [41].

Both laparoscopic and robotic techniques have been presented which are modified versions of the open approach. These techniques are for benign VVFs, for post‐radiotherapy, or malignant fistulae an open approach is advocated [41–47]. For large VVFs, it may be necessary to consider ileocystoplasty or urinary diversion to prevent vaginal losses. Often a suprapubic and urethral catheter are placed at the end of VVF repair and the suprapubic catheter left in situ for several weeks whilst the urethral catheter is removed 5–7 days postoperatively. Patients should be discharged with laxatives and anticholinergics for bladder spasms if required.

Success rates for primary repair are around 90% [39]. Commonly women will experience urinary frequency and urgency postoperatively and some have issues with stress or urge urinary incontinence, although this is often not clinically significant and improves with time from surgery. There is an impact on sexual function and women will often report vaginal dryness or dyspareunia [48].

24.4.3.3 Vesicouterine Fistula (Youssef’s Syndrome)

This rare fistula is characterised by cyclical haematuria and amenorrhea with no leak of urine PV [49]. These fistulas typically develop in women who have history of Caesarean section or assisted vaginal deliveries. However, they can develop after any gynaecological procedure during which the uterus is instrumented. The woman will only develop urinary incontinence if the cervical os sphincter is incompetent or if the opening is below the level of the cervical os [50]. Magnetic resonance imaging (MRI) is helpful at identifying the fistula tract and will allow reveal urine within the endometrial cavity.

Treatment options include a conservative approach with urethral catheterisation to prevent urine entering the uterus and medical induction of amenorrhoea to prevent mensuria which has been shown to produce spontaneous closure [51]. The surgical principles for repair are identical to that of VVF repair: a tension‐free layered closure and are generally done via an open approach, although laparoscopic and robotic cases have been published [51].

24.4.3.4 Vesicocutaneous Fistula

These uncommon complex fistulae are usually iatrogenic from pelvic surgeries or arthroplasties, although can occur secondary to pelvic fractures, or in the presence of large bladder calculi. Very rarely they can follow pelvic radiotherapy [52]. They can also be seen in the paediatric and adult population of those who have undergone congenital bladder exstrophy repairs. They are perhaps most commonly encountered in patients with previous long‐term suprapubic cystotomies that have failed to close.

24.4.4.1 Rectourethral Fistula

These are a complex and uncommon fistula that are usually iatrogenic, although there are reported cases of congenital fistulae. They can develop as a consequence of prolonged pelvic sepsis in patients with diverticular disease or inflammatory bowel disease or from deep pelvic surgery. They are most commonly seen as a complication of radical prostatectomy for prostate cancer (PCa), whereby an inadvertent rectal injury has occurred during the dissection of the plane between Denovilliers fascia and the rectum, leading to a recto‐urethral fistula [53]. They have also been reported to develop post transurethral resection of prostate where the anatomy his been difficult to distinguish. Of note they can also develop as a complication of the newer ablative prostate cancer treatments such as brachytherapy, cryoablation, and high‐intensity focused ultrasound [54–58].

Patients typically present with the passage of faecal material per urethra, and this can result in subsequent recurrent UTIs. Investigations include both sigmoidoscopy and ureteroscopy, as well as formal imaging with CT scanning with rectal contrast. A urethrogram may illustrate contrast flow into the rectum (although this may be of better value in delineating concomitant urethral strictures), although often the pressure in the rectum is higher and so contrast often flows better from the rectum to urethra.

Traditionally the main approach to managing these cases was first to perform a defunctioning colostomy. This aids in resolution of pelvis sepsis and alleviates symptoms. It is generally insufficient as treatment alone, except in small fistulae formal, surgical repair is required and should be supplemented with a low‐residue diet and antibiotics. There is a choice of methods for closing fistulae between urethra and rectum with more than 40 different methods described and a variety of surgical approaches including trans‐anal, transperineal, laparoscopic, and robot‐assisted [59].

24.4.4.2 Urethrovaginal Fistula

These fistulas have increased in incidence, although remain uncommon, in the era of midurethral incontinence procedures such as transvaginal and transobturator tapes, although remain rare. Women present with new or worsening urinary incontinence and may have a history of previous incontinence‐ surgery. Clinical examination may be unremarkable, although a red granulomatous area may be seen on the anterior vaginal wall on speculum examination. Patients require cystoscopy and examination under anaesthetic, and this is usually sufficient to confirm diagnosis.

Surgical repair is preferred and generally involves a transvaginal approach and follows the same principles and approach of vesicovaginal fistula repair: a multi‐layer repair with the placement of a Martius flap. If previous tapes have been placed, these should be removed and thought should be given to whether further incontinence surgery is also required; some have also performed a synchronous pubo‐fascial sling procedure [60, 61].

24.4.4.3 Urethrocutaneous Fistula

These fistulae are very uncommon, although are most commonly encountered in the cohort of patients with congenital urogenital defects particularly after hypospadias repairs, in patients with bladder exstrophy, and in those undergoing penile constructive or reconstructive surgery, including gender reassignment and urethroplasty. It has been reported as a rare consequence of tuberculosis [62].

Cystoscopy alone is often diagnostic. Surgical repair can vary in complexity to primary repair with multilayer closure to the use of tunnelled tunica vaginalis flaps which have been shown to be effective and with few complications [63, 64]. Regardless of the technique a period of urinary diversion is required for several weeks postoperatively, and this is usually achieved by the placement of a suprapubic catheter at the time of surgery.