Q. What is the blood supply of the urethra?
A. The blood supply to the urethra is derived from the internal pudendal branch of the internal iliac artery. It enters the perineum via the pudendal canal (of Alcock) and terminates in the common penile artery which provides three branches that supply the structures of the penis. The urethra gets a generous blood supply from the bulbourethral and dorsal penile branches which arborise in the glans penis.
Q. A previously well 24-year-old man is referred to you with a history of slow urinary stream. He has recently been treated for a urinary tract infection but is otherwise well. What is the most likely cause of this patient’s problems?
A. A urethral stricture. The differential diagnosis includes bladder neck obstruction, neuropathic bladder and late presentation of posterior urethral valves.
Q. What is the aetiology of urethral strictures?
A.
1. Posterior urethral strictures (prostatic and membranous urethra) are due to a fibrotic process that narrows the lumen and most commonly these are due to trauma such as a PFUDD or surgery, e.g. radical prostatectomy, TURP, cryotherapy, laser use.
2. Anterior urethral strictures (bulbar, penile and navicular urethra) are a result of scar formation in the spongy erectile tissue of the corpus spongiosum. This scarring may be subsequent to
a. Inflammatory processes - Gonococcal urethritis, balanitis xerotica obliterans (BXO).
b. Trauma - Direct blow or straddle/fall astride injury (usually affects bulbar urethra).
c. Iatrogenic - Traumatic catheterisation, instrumentation, post-hypospadias repair/ urethral surgery.
d. Idiopathic/congenital - May be the result of a previous straddle injury, which may have gone unnoticed. However, there is a distinct group of young men in whom strictures occur between the proximal and middle thirds of the urethra, which contain a high content of smooth muscle on biopsy and are termed ‘congenital’ (form between point of fusion of the urethra from its two different embryological origins).
Q. What would you look for on examination?
A. In patients with urethral strictures, there are often no external signs of the disease process. However, it is important to inspect for BXO, meatal stricturing, hypospadias and evidence of prior surgery. Palpation may reveal spongiofibrosis adjacent to the stricture.
Q. What does the flow curve in Figure 8.12 show? What other investigations are important?
Figure 8.12
A. Figure 8.12 demonstrates a prolonged slow flow classical of a urethral stricture. This is typically termed a ‘plateau’-shaped trace with little change in flow rate.
Further investigations would include the following:
Flexible urethroscopy - Direct inspection of the urethral lumen is probably the most common first line of investigation in the United Kingdom.
Urethrography - Ascending and descending studies. In specialist centres, urethrography is performed in place of urethroscopy as it provides the most detailed information about the urethra. A diagnosis and management plan can be formulated and the patient counselled appropriately.
Additionally USS may show a thickened bladder wall and residual urine. If hydroureteronephrosis is present then estimation of renal function should be performed. Urinalysis will exclude concurrent urinary tract infection (UTI).
Q. What does this antegrade urethrogram in Figure 8.13 show?
Figure 8.13
A. Figure 8.13 is an antegrade urethrogram illustrating a short narrowing of the bulbar urethra consistent with a stricture. Ascending, descending and dynamic images should be reviewed.
Q. How would you manage this patient and why?
A. I would counsel this patient for an optical urethrotomy. The alternative is a urethral dilatation or a combination of urethrotomy and dilatation. ttere is no advantage in terms of outcome but the optical urethrotomy is done under direct vision so may be considered safer. Approximately 50% of urethral strictures require no further treatment following optical urethrotomy urethral dilatation. These are typically short (<1.5 cm), located in the bulbar urethra, associated with minimal spongiofibrosis and have had no previous interventions.
A urethral catheter should be left in situ for 3 days following an optical urethrotomy and the patient should be taught intermittent self-catheterisation/dilatation, which should be continued for 6 months (reduces restructuring rates).
Q. How would you manage a patient whose short bulbar stricture recurs following an optical urethrotomy?
A. If the patient is fit for anaesthesia, and the stricture <2 cm in length I would counsel the patient for an anastomotic bulbar urethroplasty which is curative in approximately 90% of cases at 10 years’ follow-up. Any anastomotic repair must be spatulated, tension free and ‘stented’ (catheterised in this case).
Note: The alternative option is palliative (if this is preferable to the patient) repeat urethral dilatation/optical urethrotomy followed by long-term self-dilatation. Older age should not be considered a contraindication to urethroplasty.
Q. What are the indications for anastomotic urethroplasty?
A. This procedure is used in two situations:
Short strictures of the bulbar urethra no more than 2 cm in length.
A pelvic fracture-related injury of the membranous urethra or bulbo-membranous junction. This is not so much a stricture but a distraction defect with no continuity of the urethra and obliteration of the lumen by fibrous tissue, which separates the ends of the urethra.
Note: The membranous urethral strictures following TURP, sometimes known as ‘sphincter strictures’ because they are due to fibrosis within the external sphincter mechanism, are best treated by urethral dilatation in order to avoid incontinence.
Q. Which manoeuvres can be used to bridge the defect during anastomotic urethroplasty (in order to bring the two ends of the urethra together) if bulbar urethral mobilisation alone is not adequate?
A. If the elasticity of the urethra and mobilisation are not sufficient to bridge the defect then the principle is to straighten out the natural curve of the bulbar urethra so that its course from the penoscrotal junction to the prostatic apex is a straight line (rather than a semicircle). The manoeuvres used to do this are
Separation of the crura at the base of the penis
Wedge pubectomy of the inferior pubic arch Re-routing of the urethra around the shaft of the penis
Defects up to 7 cm can be bridged using these steps in sequence.
Q. What specific complications can occur post bulbar anastomotic urethroplasty?
A. Bleeding, wound infection, post-micturition dribbling (due to division of the bulbospongiosus muscle) and stricture recurrence.
Q. What operative options are available for longer bulbar strictures?
A. Substitution urethroplasty: this is used for bulbar strictures too long for anastomotic repair and in strictures of the penile urethra where anastomotic urethroplasty is not advised due to buckling on erection. A dorsal stricturotomy with placement of a dorsal patch (Barbagli procedure) is the preferred procedure. (Complete excision of the stricture with circumferential repair is only performed if the affected section of urethra definitely needs to be completely excised, e.g. BXO strictures or anterior strictures related to previous hypospadias repair, in which the tissue is totally scarred.) A dorsal patch is preferred as it is well supported by the cavernosal bodies and thus out-pouching does not occur. The current dorsal patch of choice is a buccal mucosal graft.
Other options include an augmented anastomotic urethroplasty, which is not commonly performed and a perineal urethrostomy, which is generally used only when reconstructive surgery fails.
Q. For complex strictures such as those related to radiotherapy should one use a graft?
A. No. In the presence of diseased tissue, e.g. following radiotherapy, grafts will not take. thus any tissue transfer needs to have its own blood supply and a genital skin flap is used pedicled on the vascular dartos layer of the penis.
Q. What are the success rates of anastomotic and substitution urethroplasty?
A. Anastomotic urethroplasty is associated with an approximately 90% success rate at 10 years. Substitution urethroplasty success rates are worse with 85% patency rates at 1-3 years and deteriorating at 3%-5% per year so that by 10-15 years approximately half the patients have developed recurrent strictures.
Q. What options are available for the management of penile urethral strictures?
A. The management of penile strictures is complex. Aetiology, length, location and the condition of the surrounding tissues are important. Urethral dilatation or optical urethrotomy will inevitably fail in penile strictures and anastomotic urethroplasty should not be performed for penile strictures as this will result in unacceptable penile deformity on erection. More proximal simple penile urethral strictures (i.e. those not caused by BXO or failed hypospadias repair) can be managed with a stricturotomy and penile skin flap (Orandi flap). Distal strictures, usually related to previous hypospadias repair or BXO, can be managed with excision of the affected segment followed by a circumferential repair involving a two-stage urethroplasty using buccal mucosal graft (for BXO genital skin cannot be used as the disease will recur in this tissue).
Q. Why has buccal mucosa become the graft of choice?
A. Several reasons including
Ready availability in sufficient quantities
Minimal morbidity to the donor site
Tough, easy to handle
Behaves like a full-thickness graft, so little or no contraction and rich sub-dermal plexus (much more vascular than skin) and thus takes well
Accustomed to a wet environment
Appears to have antibacterial properties
Resistant to skin diseases
Q. What specific donor site complications can occur after harvesting of a buccal mucosal graft?
A. Discomfort, bleeding, donor site infection, injury to parotid duct (Stenson’s), numbness in oral cavity, persistent difficulty with mouth opening and change in salivary function.
Further Reading
1. Santucci RA et al. Evaluation and management of renal injuries: Consensus statement of the renal trauma subcommittee. BJU Int 2004; 93: 937-954.
2. European Association of Urology. http://uroweb.org/guideline/urological-trauma
3. McAninch JW, Ed. Genitourinary trauma. Urol Clin North Am 2006; 33: 1-132.
4. Andrich DE et al. Urethral strictures and their surgical treatment. BJU Int 2000; 86: 571-580.
5. Gommersall L, Kapasi F, Potluri B. Diagnosis and management of renal trauma. Chapter 7 In: Shergill IS, Arya M, Patel HR, and Gill IS, Eds. Urological Emergencies in Hospital Medicine, London: Quay Books, 2007, pp. 61-70.
6. European Association of Urology. http://uroweb.org/guideline/urological-trauma