Anatomic Study Of The Approaches On Male Posterior Urethral Stricture

Posterior urethral stricture is a difficult undertaking even in an experienced specialist's hands.There are many methods for this lesion,such as urethral dilation, urethrotomy,stent implantation and open operation,each of which has its own indications.Anastomostic urethroplasty has been being a gold standard for the treatment of this kind of lesion for its lower recurrence and higher success rate.However there remaining a high incidence of recurrence and some complications,such as erectile dysfunction and incontinence that brings severe damage to the patients especially with so-called complex strictures.Recurrence results mainly from an insufficient scar tissue resection which usually caused by the complex topography of the perineum,ambiguous locatization of the neurovascular buddies and a narrow operating field.It is necessary to shed light of the course and distribution of the neurovascular buddles,especially of the segment from the apex of prostate to the penile hilum for the protective aim in operation. So the incidence of complications might be decreased to some extent,scar tissue could be resected radically and a patent urethra maybe kept for a long term.On the basis of anatomic study,a modified approach will be present which aims to sermount the limitations of the traditional procedures,such as a narrow operating field,ambiguous visualization,insufficient scar resecting and difficulties in urethral reconstruction.Anatomic structures relating to the urethroplasty,especially the course and distribution of the cavernous nerve,pudendal nerves,arteries,the shape and innervation of the rabdosphinctor were investigated by the way of dissection in 5 formalin fixed cadavers and 5 fresh cadavers.The dissection of cavernous nerve was performed under a stereomicroscope by way of cutting the pelvic specimen into a sequential slice.In the first-stage study,we found that the cavernous nerve was posterior and lateral to the apex of prostate,coursed down into the interspace between prostate and levator ani muscle, then was divided into 3 group of branches and coursed vanward,outward and inward respectively.The anterior branches run along the wall of external rabdosphinctor,some branches courses through the wall and go into the hilum of penis.The lateral part of the cavernous nerve branches fine fibers which communicate with the anterior branches of cavernous and pudendal nerves.The posterior branches are posterolateral to the membranous urethra,which innervate the rabdosphinctor,cowper gland and urethra as well.The branches of pudendal nerve and cavernous nerve form a meshwork,which locates at the base angle of perineam.The triangular area of the base angle of perineum is a dangerous field for urethroplasty. On the basis of anatomic study in the first stage,perineal anastomostic urethroplasty and transpubic urethroplasty were imitated on 3 latex-infused fresh cadavers.The aim of the second-stage study is to determine the indications of the two approaches by the way of a comparative dissection,moreover,to interpret the cause of the complications,and provide a guideline for the two operation.Structures within the approaches were obsevered,the distance between cavernous nerve and midline, cavernous nerve and membranous urethra were measured and maneuvers that may be impair the cavernous nerve were detected.The distance between cavernous nerve and midline is 5.4±1.7mm,that of membranous urethra and cavernous nerve is 7.2±1.1mm respectively.Cavernous nerves distribute in the two base and the vertex angle and course along the side line of the urogenital triangle.The bulbspogisum posess good elasticity, and could be stretched for to 4-5cm long.The field of the transpubic approach is wider than that of perineal one.Indications of the two approaches were further verified from an anatomic viewpoint.We recommend that the site while not the legth of a stricture should be taken as the indication for the dission making of which approach should be seclected. The causes of complications were analysed.The incidence of the cavernous nerve injury was correlated to the extent of midline maneuvers.In order to surmount the limitations of the perineal approach that is a narrow eyesight and field,the feasibility of the lateral perineal approach was investigated.We imitated the approaches of perineum and lateral perineum on two fresh cadavers and observed the structures that maybe impaired in the operation,cavernous nerve was the the most emphasized structure in the dissection.We compared the eyesight of the two approaches and the extent of exposure to the membranous urethra and the apex of prostate.The lateral perineal approach could expose and manage the cicartrix tissue more easily from the lateral side of the membranous urethra.The operative field is a triangle and could be enlarged with the aid of traction.The field of maneuver is wider than that of a classic perineal approach and more suited for a prostamembranous stricture with gross scar tissue.The incidence of impairment of cavernous nerve is the same as classic perineal approach.