Modern Methods of Treating Diseases of the Bulbo-Membranous Part of Urethra

Strictures of the bulbous-membranous urethra are a common cause of obstructive urination disorder. Modern trends in the development of medicine lead to a wider application of endoscopic method, a more frequent cause of iatrogenic injury of the urethra. At present, conservative, endourologic and reconstructive methods of care are used to treat urethral strictures. There are several conservative, endourological and reconstructive methods for treating patients with urethral stricture. Conservative methods include interventions that do not involve the destruction of urethral stricture or its reconstruction, such as stenting, blind dilatation, and recanalization of the urethra. Performing blind dilatation strictures of the bulbo-membranous urethra is not recommended because of the high risk of false path formation and low efficiency. Endourological operations refer to surgical methods of care and suggest the natural restoration of urethral tissues after the destruction of stricture. Because of the low effectiveness of correction of strictures of the posterior urethra (more than 90 % of relapses in five years), this method is a variant of temporary or palliative care. Currently, two approaches to the reconstruction of the bulbo-membranous urethra are used: anastomotic and replacement operations. Anastomotic surgery involves excision of the affected area and juxtaposition of healthy urethral tissues without tension. Replacement plastic allows to restore patency of the urethra by increasing the diameter of the lumen due to the implantation of various grafts. The article shows that, based on international clinical studies, the most effective method of reconstructing the bulbomembranous urethra is reconstructive surgical methods.


RELEVANCE
Stricture disease of the urethra is a partial or complete narrowing of the urethral lumen.It can occur as a result of trauma or inflammation, which leads to irreversible violations of urination and, possibly, death.Treatment of this disease is still a difficult task.
At present, there is no generalized exact information on the incidence of stricture disease.Hypothetical calculations predict that approximately 0.6 % of men over the age of 55 have a narrowing of the urethral lumen.In a few studies authors report about different incidence rates, ranging from 30 to 627 cases per 100,000 of population.Thus, in Denmark, between 1977 and 2013, the total incidence of stricture disease was 34.8 per 100,000 of population [37].In this case, men over 60 years accounted for 66.9 % of cases of urethral strictures.In the United States, according to the American Urological Association (AUA) in 2003, the incidence was 193 cases per 100,000 of population [51].Thus, there is a significant statistical dispersion even in the developed countries of the world.
In Russia, there is no statistical account of the incidence of urethral stricture.This group of patients in statistical reports is combined with other diseases (benign prostatic hyperplasia, neurogenic urination disorders and others).Thus, the frequency of detection of diseases of the urinary system with obstructive symptoms in the city of Moscow for the period of 2011-2012 was 275-291 cases per 100,000 of population.
Information on the incidence of urethral stricture in the hospitals of Irkutsk for the period from 2012 to 2014 is presented in Table 1.
Based on the above reasons, it is difficult to estimate the incidence of urethral strictures and, especially, of its bulbo-membranous part.The average frequency of detection of the narrowing of the bulbo-membranous urethral part (BMP) calculated indirectly is about 8 % of the total incidence of urethral stricture [45].
Currently, two methods of surgical treatment of strictures of the proximal part of the bulbar urethra and the BMP are used: endourologic intervention and reconstructive surgery.
In addition to the anastomotic reconstruction, substitution urethroplasty is used.The method involves replacing part of the urethra with autologous, allologic, xenologic or tissue-engineering grafts.This method is one of the most effective in the reconstruction of another part of the urethra, but in the BMP its effectiveness is inferior to anastomotic methods [2].

INDICATIONS, ALGORITHMS OF TREATMENT
Based on the established diagnosis, indications for treatment are determined.Clearly formulated relative indications for surgical intervention for strictures of various parts of the urethra at the present time does not exist.Nevertheless, given the long period of subcompensation, patients are shown to perform dynamic observation and, possibly, treatment for any detected urethral stricture, even under normal urodynamic parameters (maximum urinary flow rate is more than 15 ml/sec, residual urine is absent).It is possible to conduct conservative therapy with fibrinolytics, dilatation and physiotherapy in the early stages of the disease (maximum urine flow rate is 12-15 ml/sec, residual urine volume is less than 100 ml), and in severe inoperable cases.
At present, consensus is reached in the Russian and world practice (EAU Guidelines, 2017, AUAGuidelines, 2016) on the algorithm for helping patients with stricture of the posterior (including the BMP) urethra.
The algorithm for examining and treating lesions of the posterior urethra is based on the causes of stricture.If there is a suspicion of iatrogenic damage to the urethra (for example, catheterization with urethrorrhagia), urethrography is indicated.In case of detection of acute damage, the urethra is drained by a catheter for a period up to the healing of the urethral walls.When revealing stricture of the urethra less than 10 mm in length -DVIU is performed.With strictures of greater length, an anastomotic reconstruction of the urethra is recommended.
If the stenosis of the vesicoureteral anastomosis after radical prostatectomy is revealed, it is possible to dilatation the urethra or endoscopic dissection of the stenotic ring.If these methods are ineffective, patients are offered re-anastomosing or permanent drainage of the bladder with a cystostomy.
At a blunt trauma of a urethra endoscopic recanalization or a drainage of a bladder by a cystostoma is carried out for the term up to three months.In the future, if a stricture of the urethra recurs, it is possible to perform a DVIU or an anastomotic reconstruction.
In the presented clinical recommendations, conservative treatment of urethral strictures (recanalization, dilatation, stenting) or performing DVIU is allowed.If they are ineffective, the second stage is used for urethroplastic reconstruction.In the clinical recommendations of the American Urological Association of 2016, the possible negative impact of DVIU and conservative treatment methods on the prognosis of the course of urethral strictures is indicated.Replacement methods of urethroplasty are absent in the presented algorithms because of their low efficiency and lack of advantages over anastomotic methods.
Recanalization is a method of restoring the urethra on a catheter, performed in the bladder with a fibrourethrocystoscope.When the urethra is recanalized in a patient with a distraction defect, drainage of the urethra by the catheter should be stopped only when the re-epithelization of the affected area is completed [15].At week 9, it is achieved in 83 % of patients, the remaining 13 % -by the 12th week of drainage.This technique does not guarantee a cure, and the process of re-epithelialization should be controlled by the method of periodic flexible ureteroscopy.The overall efficiency of recanalization is low.The subsequent formation of strictures is revealed in 14-79 % of cases, urinary incontinence is < 5 %, impotence is 10-55 % [33,38]post-void residual and cystoscopic evaluation.Failure of early endoscopic realignment was defined as patients requiring urethral dilation, direct vision internal urethrotomy, posterior urethroplasty or self-catheterization after initial urethral catheter removal.RESULTS A total of 19 consecutive patients (mean age 38 years.
DVIU is the development of the blind uretrotomy technique, allowing to improve the effectiveness and reduce the incidence of complications.It is performed by a cold knife or laser.Strictly contraindicated is holding Surgery power tools.In the case of subtotal lesion or complete obliteration of the urethral lumen, DVIU can be used in the direction of bougie, or by the method of "counter light".
The overall effectiveness of the DVIU in the treatment of strictures of the proximal part of the bulbar urethra is from 20 to 75 % according to different data [32, 33, 39] compared with 24 of 29 patients with shorter strictures (p = 0.001, and depends on the cause of the formation and extent of urethral stricture.The effectiveness of this procedure for lesion of the posterior urethra is doubtful, and with complete obliteration of the lumen -critically low [34]morbidity, and outcomes of open versus endoscopic treatment of posttraumatic posterior urethral strictures.We compared two groups of men with strictures of the posterior urethra after pelvic fracture: Group I (n = 6.
With distraction defects of the urethra, it is not recommended to perform a delayed DVIU, but to perform the plastic reconstruction.In such a situation, any excessive urethral interventions should be avoided, as they can delay or worsen treatment outcomes [12]San Francisco experience with delayed anastomotic posterior urethroplasty for management of these injuries.MATERIALS AND METHODS Since 1979 all patients undergoing posterior urethroplasty by a single surgeon at University of California, San Francisco and its affiliated hospitals have been entered prospectively into a patient registry.For this cohort descriptive statistics were calculated and recurrence was analyzed with the Kaplan-Meier method.Success was defined as no recurrence (by symptoms and/or retrograde urethrogram.With incomplete separation of the posterior urethra and partial preservation of the urethral lumen, it is possible to perform DVIU with the first stage followed by self-catabolization in certain groups of patients.
In cases of neurogenic disorders of urination due to spinal trauma, when intermittent catheterization is required, the patient may be required to perform periodic DVIU in order to maintain urethral patency.

ANASTOMOTIC URETHROPLASTICS
With stricture of the posterior urethra, delayed anastomosing urethroplasty is the recommended method of care for most patients.Its use after traumatic injury of the urethra is possible after 2-3 months, for other etiologic reasons -the term is determined individually.Emergency, urgent or delayed urethroplasty is contraindicated, as it is accompanied by a very high risk of complications (impotence -56 %, incontinence -21 %).
Anastomotic operations are performed through perineal access in a modified lithotomy position.The need for additional suprapubic access is rare, usually with the correction of the neck of the bladder.Most surgeons consider perineal access to be sufficient for visualization of the entire membranous urethra, and transpubic access -not having significant advantages for greater complexity of execution and high traumatism.
Classical anastomosing method (by Turner-Warwick) involves matching the ends of the urethra after excision of the affected area.When revealing extensive strictures of the BMP to compensate for a decrease in its length after excision, in some cases, dissection of the intercavernosum septum, resection of the lower branch of the pubic bone, or movement of the urethra (rerouting) over the cavernous body foot (Webster's method) are needed.This set of techniques is technically difficult, it requires a lot of time and involves a high risk of operational injury.Nevertheless, the efficiency of such anastomotic reconstruction reaches 85-90 % [13,18,41,52]1-stage delayed repairs of complete posterior urethral ruptures in 60 men with at least 1-year followup were reviewed.Two ruptures were due to gunshot wounds and 58 were secondary to a pelvic fracture.There were 58 repairs done by the perineal approach and 5 required an abdominal perineal approach.RESULTS Surgical complications included 2 (3%.
The presence of strictures of the distal urethra limits the use of anastomotic reconstruction.The effectiveness of one-stage or subsequent reconstruction is reduced due to a violation of the blood supply to the corpus spongiosum [28].Particular attention is required to patients with congenital hypospadias due to more severe ischemic disorders of the blood supply of the bulbar urethra during its devascularization.

SUBSTITUTING URETHROPLASTICS
In addition to the anastomotic reconstruction, substitution urethroplasty is used.In cases where it is impossible to perform an anastomosing operation (with an extensive distraction defect, urethral strictures longer than 7 cm, or with ineffectiveness of the preceding anastomotic urethroplasty), it is recommended to do the flap or graft reconstruction [42].
The experimental work performed on animals can be considered as an evidence against the hypothesis of poor engraftment of grafts on a muscular basis.The study established [3] that the survival rate of the buccal graft on the gallbladder of the penis is 93.4 %, on the muscle -90.7 %, on fat -81 %.Thus, the reason for the ineffectiveness of the replacement urethroplasty of the membranous part of the urethra is not the muscular basis for transplantation, but the disruption of normal blood supply in the surgery area and the use of tubularized grafts.
Intraurethral replacement plastic [56]21 ANTA, described in 2012, is one of the most complex of substitute urethroplasty methods.This technique is performed with strictures of the proximal part of the bulbar urethra.In the BMP of the urethra this method is not applicable.
Rarer techniques such as endoscopic urethroplasty with a skin or mucosal flap with different fixation mechanisms have the advantage of being less invasive, but not sufficiently studied to talk about their success.Preliminary data are contradictory -the effectiveness was from 54.5 to 80 % [17,31]endoscopic antegrade urethroplasty was performed in 11 patients with recurrent vesicourethral anastomotic strictures that developed after retropubic radical prostatectomy (RRP.
The most promising new method for the reconstruction of the posterior urethra is tissue-engineering surgery [16,53]re-epithelialization, and remodeling that are limited by the size of the defect.Scar formation occurs because of an inability of native cells to regenerate over the defect before fibrosis takes place.We investigated the maximum potential distance of normal native tissue regeneration over a range of distances using acellular matrices for tubular grafts as an experimental model.MATERIALS AND METHODS Tubularized urethroplasties were performed in 12 male rabbits using acellular matrices of bladder submucosa at varying lengths (0.5, 1, 2, and 3 cm.In a pilot study [49] published in 2011, the results of the replacement of the BMP of the urethra in 10-14 year old boys with the use of tissue-engineered tubular flaps were analyzed.With a median follow-up of 71 months, the efficacy was 100 %.Similar results claim a new "gold standard" of assistance after a multicenter study [55].

CONCLUSION
Based on the review of currently used methods for treating of strictures of the BMP of the urethra, it is possible to draw a number of conclusions.First, DVIU is ineffective and dangerous operation, which can worsen the results of subsequent treatment and make the disease more difficult.Secondly, there is a significant group of patients for whom the performance of anastomotic reconstruction can lead to negative consequences due to damage to anatomical perineal structures (perineal muscles, urethral sphincter, vessels and nerves of the urethra and penis).Third, the methods of traditional substitution urethroplasty are inferior in effectiveness to anastomotic reconstructions, or are not available in everyday urological practice for technical reasons (tissue-engineering surgery).
In summary, the stricture of the BMP of the urethra is a rare, but extremely urgent and dangerous pathology.The given conclusion is caused by technical complexity, low efficiency and heavy consequences of existing methods of treatment.
Thus, there is a need to develop a different, more effective method of helping patients with strictures of BMP of the urethra, the proximal part of the bulbar urethra or stenoses of anastomoses in the posterior urethra.