Anatomy

The male urethra is approximately 20 cm in length and is composed of the short posterior urethra and the longer anterior urethra. The posterior urethra comprises of the prostatic and membranous sections. The anterior urethra is formed by the bulbar and the penile segments and terminates at the external urethral meatus at the tip of the glans penis. The bulbar urethra is located at the dorsal aspect of the corpus spongiosum, having a thick ventral covering, whereas towards the distal penile urethra, the urethra is located ventrally. The configuration of the corpus spongiosum surrounding the urethra varies considerably and is absent in the posterior sphincteric portion with significant variation as one progresses along the length of the urethra (Fig. 26.1). It is important to realize that the corpus spongiosum is a very vascular organ (Fig. 26.2) and it is ischemic damage to this which leads on to urethral stricture disease (Fig. 26.3).

Table 26.1

Stricture aetiology by location [5]

	No. Penile (%)	No. Bulbar (%)	No. Panurethral (%)	No. Posterior (%)
Prostatectomy	0	3 (2.33)	1 (2.78)	5 (12.5)
Perineal trauma	0	6 (4.65)	0	0
Urethral catheterization	9 (14.29)	13 (10.08)	9 (25)	0
Idiopathic/unknown	13 (20.63)	62 (48.06)	5 (13.89)	0
TUR	7 (11.11)	32 (24.81)	9 (25)	4 (10)
Hypospadias	18 (28.57)	5 (3.88)	2 (5.56)	0
Pelvic fracture	0	0	1 (2.78)	29 (72.5)
Urethritis	1 (1.59)	6 (4.65)	3 (8.33)	0
Lichen sclerosus	10 (15.87)	0	3 (8.33)	0
Cystoscopy	0	1 (0.78)	2 (5.56)	0
Tumor	3 (4.76)	0	1 (2.78)	0
Penile fracture	2 (3.17)	1 (0.78)	0	0
Brachytherapy	0	0	0	2 (5)
Totals	63	129	36	40

The absence of an outer corpus spongiosum at the posterior urethra has important implications in stricture terminology and treatment. Being the only urethral segment lacking any fixed supportive tissue, the membranous urethra is vulnerable to external injury and importantly the distal urethral sphincter is located at this level.

The distal urethral sphincter mechanism, supplied by nerves from the S2 to S4 level provides voluntary control of urinary flow. The anterior urethra acts as a conduit for the passage of urine. Lined by stratified epithelium, the anterior urethra differs from the transitional epithelium lined posterior urethra.

The female urethra measures 4 cm in length. It consists of both smooth muscle layers and striated muscle along its length, with the outer striated muscle critical in maintaining continence.

Pathophysiology

Strictures form as a result of ischaemic scarring of the spongy tissue of the corpus spongiosum (spongiofibrosis). The area of disease appears white or grey in contrast to the pink appearance of healthy urethral tissue (Fig. 26.3).

As a result of epithelial insult, the underlying vascular spongy tissue is exposed which heals by fibrosis. As voiding occurs, urine further irritates this process. Stenoses form in the posterior urethra due to direct trauma to the urethral epithelium or in the bulbar urethra due to external injury; so called pelvic distraction injuries associated with a pelvic fracture or fall astride injuries as seen in the bulbar urethra respectively, both of which are not associated with significant loss of urethral length (Fig. 26.4).

Lichen sclerosus (LS), formerly known as Balanitis Xerotica Obliterans is responsible often for complex strictures of the anterior urethra. First described by Stuhmer in 1928 [2], it is an inflammatory condition of unknown aetiology affecting the stratified epithelium of the anterior urethra. For this reason, it does not affect the posterior urethra, lined by transitional epithelia. Urethral involvement by LS was first described by Laymon in 1951 [3]. Histologically, excess dermal collagen is present with a hyperkaratotic epidermal layer. It has a progressive tendency, leading to significant rates of recurrence in uro-genital epithelium.

Aetiology

The aetiology of stricture disease is a fundamental consideration in planning treatment. In contemporary practice most urethral strictures encountered are idiopathic, traumatic, inflammatory or iatrogenic.

Although the term posterior urethral stricture is still used, it generally encompasses the terms bladder neck stenosis (or vesico-urethral anastomotic stenosis following prostatectomy) and the pelvic fracture urethral injury (PFUI) affecting the membranous urethra or the bulbo-membranous junction [4]. This distinction is important, as the pathogenesis and surgical options differ significantly. Following a radical prostatectomy, a stenosis may form at the vesico-urethral anastomosis proximal to the distal urethral sphincter. This can also be seen in posterior urethral stenoses that occur in men following TURP. In this case, the sphincter mechanism is intact and the urethra, although stenosed remains in continuity.

In pelvic fracture urethral distraction disorder (PFUDD), the two urethral ends are distracted relative to one another, even though the gap between the ends may be significant there is minimal loss of length. In approximately 60% of cases the distal sphincter mechanism is involved in the injury and continence depends on the integrity of the bladder neck mechanism.

The idiopathic abnormality of the bulbar urethra which gives rise to the short strictures identified in young men without an identifiable cause represents a significant proportion of cases. Being short and soft in composition, these can be successfully treated by a single direct vision internal urethrotomy (DVIU) in a proportion of patients. Proximal bulbar strictures can also occur following perineal trauma due to distracting forces between the protected bulbar urethra and the vulnerable membranous urethra.

Lichen sclerosus, as previously discussed, tends to be responsible for long anterior urethral strictures and may affect other areas of genital epithelia. For example prepucial skin and the urethral meatus.

Hypospadias, although not directly associated with stricture formation itself, can result in spongiofibrosis as a result of the surgery used to correct it in childhood.

Occasionally strictures can occur following genitourinary infections, although with the advancement of antibiotic therapy, causative organisms such as Gonorrhoea and Chlamydia represent much less of a burden on stricture formation.

The two major types of stenosis are shown in Figs. 26.3 and 26.4.

Basic Investigations

Most men with urethral stricture disease will present with voiding lower urinary tract symptoms. There may be a feeling of incomplete emptying as obstruction slowly develops, with or without haematuria or urinary tract infection as a consequence.

Uro-flowmetry characteristically shows a plateau pattern with a low Qmax. However it must be remembered that the effective diameter of the unobstructed male urethra is in the order 11Fr [6] and until the stricture narrows beyond this point there would not necessarily be interference with flow. Indeed, patients who have a known diagnosis of a stricture, but have a flow rate greater than 10mls/sec, normal bladder thickness and no features of recurrent urinary tract infection do not necessarily require treatment. In the face of recurrent urinary tract infections or features of obstruction, either biochemically or radiologically, treatment should be considered.

Urethrography

Retrograde urethrography (RUG) is regarded as the gold standard investigation in urethral stricture assessment. When performed correctly, it can give the investigating clinician information regarding the stricture location, length and any other pathology affecting the urethra (diverticulum, fistula, false passages).

A synchronous combination of RUG with voiding cystourethrogram or a combined cystoscopy and urethroscopy (retrograde or antegrade) is recommended to assess posterior urethral strictures and importantly identify the function of the bladder neck. This has particular implications and is certainly recommended in patients with pelvic fracture urethral injury (Fig. 26.4b).

Cystoscopy

Standard retrograde flexible or rigid cystoscopy is recommended to assess the location and degree of spongiofibrosis. It is also suggested as a method of follow up for patients undergoing uroflowmetry, as uroflorometry alone may not indicate recurrence of disease until the urethral calibre diminishes significantly. Nevertheless, the stricture calibre is often impossible by standard cystoscopic techniques.

Cystoscopy can also be utilized in the context of early catheter realignment in the acute management of high grade PFUDD.

Further Imaging

Although ultrasonography is helpful in assessing stricture length and extent of spongiofibrosis, its use is not recommended for the sole assessment of strictures and should be combined with urethrography given its anatomical limitations. Other imaging modalitites, such as CT or MRI can provide useful information particularly in those patients with PFUDD and can be helpful in identifying diseased segments of urethra.

Management of PFUI

With PFUDD the treatment aim is to restore continuity of the diseased urethra. This can either be achieved in the acute setting, opting to perform early catheter realignment in an attempt to achieve an early time to spontaneous voiding, or to perform a suprapubic cystostomy and accept delayed stricture repair at a later date. In recent years with advances in endoscopic equipment there has been a great deal of interest in the use of early endoscopy at an early stage (within 2–3 weeks) to evacuate blood clot and introduce a catheter across the defect. In view of the rarity of this injury in most clinicians’ experience, it is advisable to limit this to specialized centres with the expertise; bearing in mind the other co-existing injuries and medical problems in these patients, acute transfer of these patients is rarely appropriate, hence the reliance on a two stage approach of introducing a suprapubic catheter and a secondary repair.

Stenosis occurring at the bulbomembranous junction following PFUI can be successfully reconstructed using a bulbomembranous anastomotic urethroplasty. To obtain sufficient length, one relies on the elasticity of the bulbar urethra following mobilization. When sufficient length cannot be achieved, either due to excision of a long stricture or where there is significant gap following a PFUDD, several manoeuvres can be undertaken in a step-wise fashion with the aim of reducing the natural curve of the bulbar urethra. These include separation of the crura at the penile base, a wedge pubectomy, or failing this, urethral re-routing until the bulbar urethral course from the apex of the prostate to the peno-scrotal junction is a straight line. Webster and Ramon, using a perineal approach incorporate these steps in bulbomembranous anastomotic urethroplasty [7]. In clinical practice however, the latter steps are seldom practiced given that optimal length is often gained by the initial steps, although it is recommended that surgeons should be well versed in these practices as the need arises.

Repair of the majority of defects can be achieved by a perineal approach due to the defect commonly being short. Long-term patency rates for most bulbomembranous anastomotic urethroplasty procedures are in the region of 90–98% [8, 9]. The success rates for re-do procedures are similar to primary repair (87% vs. 90%) [10].

Treatment of Bladder Neck Stenosis and Vesico-Urethal Anastomotic Stenosis

Bladder neck stenosis, the term encompassing those strictures of the posterior urethra (when the prostate is in situ and there is absence of PFUI) results from iatrogenic trauma. Vesico-urethral anastomotic stenosis (VUAS) is the term given to the stenosis occurring following a radical prostatectomy. The potential mechanisms involved in VUAS include tension at the anastomosis, inflammation, extravasation of urine and ischaemia. A stepwise treatment approach in VUAS is recommended, initially with dilation and direct visual internal urethrotomy (DVIU) demonstrating success rates of 58–92% [11, 12]. Open reconstruction is challenging and can jeopardize continence, while stent procedures are limited by migration and tissue regrowth.

Transurethral resection of the prostate (TURP) can give rise to bladder neck stenosis, particularly in the resection of smaller prostates. Here, dilatation is rarely beneficial and bladder neck incision demonstrates relative success.

Similarly, posterior urethral stenoses can be observed following external beam radiotherapy (EBRT) or brachytherapy (BT) as part of the treatment of prostate cancer. Outcomes of DVIU/dilation are similar to those observed for the treatment of VUAS.

DVIU/Dilation

Originally introduced by Sachse in 1974, the intention of dilatation is to progressively stretch the stricture restoring a normal calibre urethral lumen. In DVIU, the stricture is incised, following which a catheter is left to splint the urethra open allowing re-epthelialisation before contracture can occur. This, however, is largely dependent upon blood supply and any underlying pathology, e.g. LS.

For patients with short, soft bulbar strictures, stricture free rates in the region of 50–70% can be achieved. Whilst this is significantly lower than that demonstrated by excision and primary anastomotic urethroplasty (EPA) (90–95%), it is not unreasonable to attempt a single DVIU in those patients with single bulbar urethral strictures <1 cm. Indeed, a second DVIU can be offered to those patients with recurrent disease >6 months following initial treatment [13]. The optimal duration of post-operative catheterization following DVIU is unclear.

There is no evidence that balloon dilatation of a sphincter is any way different in outcome to a urethrotomy and there is no evidence to suggest that a laser incision is in any way different to a cold knife urethrotomy.

It is recommended in healthy patients with stricture recurrence within 3 months of initial DVIU/dilation or indeed failing a second DVIU that urethroplasty should be offered. Repeat DVIU/dilation is not recommended except in those either unfit or unwilling to undergo reconstructive surgery.

In cases with a distal sphincter stricture, often seen in patients following TURP or radical prostatectomy, it is best to avoid a urethroplasty as there is no functioning bladder neck mechanism. In these cases after a urethrotomy it is best to rely upon regular intermittent self-dilatation of the stenosis.

There has previously been some interest into the use of urethral stents, both temporary and permanent for the treatment of anterior urethral strictures. Unfortunately, however these were associated with significant complications including migration, encrustation and infection. Moreover, it seems their use does make reconstruction technically more difficult in the case of a failed stent. This is particularly true in terms of bulbar urethral strictures, where the morbidity associated with encrustation is significant.

In recent years a number of studies have evaluated the efficacy of agents injected into the scar tissue at the site of stricture area as an internal urethrotomy procedure to decrease recurrence rates by preventing recurrent spongiofibrosis. In this context, Mitomycin C has been used for anterior urethral stricture [14]. Authors have reported that after 15 months mean follow-up urethral stricture recurred in 10% of patients in the mitimycin-C treated group and in 50% of patients in the untreated group [15, 16]. Another study evaluated the use of triamcinolone injection and showed a significant decrease in recurrence rate [17, 18].

Excision and Primary Anastomosis

The gold standard for the treatment of short bulbar urethral strictures is the excision and primary anastomotic urethroplasty. This allows the diseased length of urethra to be excised and the two healthy ends to be spatulated and anastomosed. Success rates are reported as high as 98.8% in 260 patients with a stricture length of 0.5–4.5 cm (mean 1.9 cm) followed up for 50 months [19]. Barbagli [20], in a study with 153 patients followed up for a mean duration of 68 months demonstrated success rates of 90.8%. Interestingly, those who underwent either a single treatment prior to urethroplasty or no treatment at all showed success rates of 92.1–100% whereas in those whom had undergone multiple previous treatment modalities stricture free rates were lower.

There is much debate over the critical stricture length to be managed by EPA. It is generally considered that the stricture length should not exceed 2 cm and Guralnick and Webster [21] suggest a limit of 1 cm. The rationale behind this is that after the 1 cm stricture length is excised and 1 cm of proximal and distal healthy urethra are spatulated and anastomosed, the deficit is 2 cm. This can result in shortening and chordee. On the other hand, it is argued that by freeing up the urethra and separating the corpora, several centimetres more may be gained in length. Morey [22] reports that in young men with proximal bulbar strictures of up to 5 cm, a 91% success rate can be achieved. Clearly, local factors play a vital part in the anastomotic repair of long bulbar urethral strictures.

In 2012, Andrich and Mundy [23] in a preliminary report, described a non-transecting anastomotic technique, relying upon a dorsal stricturotomy following mobilization of the urethra, leaving the ventral spongiosum intact. The rationale behind this is to limit the neurovascular damage resulting from urethral transection with subsequent improved healing and ED rates at the cost of incomplete stricture excision. They used this technique in 22 patients. In the 16 patients who had been followed up for a minimum of 1 year, success rates were 100%.

Substitution Urethroplasty