Urethral Groove Research Articles

Development of the penile urethra.

In humans hypospadias consists of an abnormal ventral urethral meatus, incomplete formation of the prepuce and penile curvature (Baskin et al., 1998). The cause of hypospadias is thought to be failure of formation or fusion of the urethral folds bounding the urethral groove. While failure of urethral fold fusion may be the ultimate cause of hypospadias, there are many other possible causes of this malformation. In this review, the development of the penile urethra will be described for both the human and the mouse. The purpose of this paper is to review the developmental anatomy of the external genitalia to provide a framework for subsequent chapters that will focus on mechanisms of penile development. The second goal of this review is to discuss the development of the external genitalia of the human and the mouse so as to evaluate the mouse as a relevant animal model for development of the external genitalia.

MORPHOLOGICAL VARIABILITY AND EVOLUTION OF THE BACULUM (OS PENIS) IN MUSTELIDAE (CARNIVORA)

We examined morphological variability and evolution of the baculum (os penis) across the Mustelidae through allometric analyses and character mapping. Fifty-four species and 26 genera (including 2 fossil forms) were examined with numerous caniform out-group species. Allometric analyses showed that bacular length is relatively constant across mustelids and caniforms; only a tendency to a slightly shortened baculum in mephitines was observed. Character mapping revealed the ancestral mustelid baculum to be an elongated rod-shaped bone that lacks a urethral groove and possesses a simple, nondistinct distal tip. This form is largely retained in mephitines and, to a lesser degree, in lutrines. From the ancestral condition, it is possible to derive forms with a more complicated head that has projections and openings (e.g., melines, Eira barbara, Galictis, Gulo gulo, Martes) or spoon-shaped and cup-shaped processes (e.g., Ictonyx, Mellivora capensis). Another evolutionary trajectory involves the distal tip of the baculum becoming hook-shaped and the urethral groove well developed (e.g., Mustela, Vormela peregusna). Although the structure of the baculum distinguishes closely related species, many features are derived independently in more distantly related forms. Therefore, bacular structure provides restricted phylogenetic information and should be analyzed in concert with other data sources (e.g., morphology of the basicranial region).

EFFECT OF THE DEPTH AND WIDTH OF THE URETHRAL PLATE ON TUBULARIZED INCISED PLATE URETHROPLASTY

We determined the effect of the depth and width of the urethral groove on tubularized incised plate urethroplasty for distal hypospadias. We retrospectively reviewed the records of 48 patients who underwent tubularized incised plate urethroplasty for distal hypospadias between September 1996 and December 1998 for whom preoperative evaluation of the depth and width of the urethral groove was available. Patients were examined by an independent clinician a median of 28 months after surgery when the neourethra was calibrated and urinary stream assessed. Of the 48 patients 46 were available for clinical examination. The urinary stream was straight in 40 boys and angled in 8, while none sprayed. Urethral fistula developed in 6 patients with a urethral plate of less than 8 mm. wide (p = 0.001). The urethral groove was deep in 13 cases, moderate in 20 and shallow in 15. There were no differences among these 3 groups in regard to urinary stream direction or fistula rate. Of the boys with a shallow urethral groove 6 (40%) have a neourethral caliber of 6Fr or less versus 3 (15%) with a moderate and 0 with a deep groove. This difference was statistically significant (p = 0.028). Each patient in whom meatal stenosis developed had a shallow urethral groove. Urethral groove depth appears to influence neourethral caliber after tubularized incised plate urethroplasty. A shallow groove predisposes to a narrower neourethra and meatal stenosis subsequently. We observed no evidence that incising the urethral plate increases the final urethral diameter. Urethral fistula after tubularized incised plate urethroplasty was associated with an initially narrow urethral plate.

CONGENITAL ANTERIOR URETHROCUTANEOUS FISTULA

Congenital anterior urethrocutaneous fistula is a rare anomaly that may present in an isolated fashion or in association with other penile abnormalities, such as chordee or hypospadias. There have been 18 cases of congenital anterior urethrocutaneous fistula reported in the literature. We present 14 additional cases of congenital anterior urethrocutaneous fistula. We treated 14 patients with congenital anterior urethrocutaneous fistula, of whom 9 were uncircumcised at presentation. Two patients had evidence of chordee and 4 had distal hypospadias. The type of repair was determined by the anatomical variations of this anomaly. All cases were corrected electively by various techniques based on the degree of the defect, including primary closure via a Thiersch-Duplay urethroplasty, pedicle flap urethroplasty, hinged flap urethroplasty and interpositioned island pedicle tube or onlay urethroplasty. To our knowledge the embryological events that cause anterior urethrocutaneous fistula are unclear but they likely result from a defective urethral plate or an abnormality of the infolding of the urethral groove. Surgical technique must be individualized to fit the defect. While there has been considerable skepticism regarding the existence of congenital urethrocutaneous fistula, the fact that 9 of our 14 patients were uncircumcised confirms the congenital nature of this lesion.

Cleft glans penis associated with midshaft epispadias: A successfully treated rare anomaly of the penis

A rare case of cleft glans penis associated with midshaft epispadias is presented. Because no dorsal curvature was present, roofing of the deep urethral groove and closure of the cleft glans over the urethra yielded excellent cosmetic and functional results.

Extensive Mobilization of the Urethral Plate and Urethra for Repair of Hypospadias: The Modified Barcat Technique

The modified Barcat technique was used to treat 168 patients with hypospadias during the last 5 years. The technique, which is applicable for distal hypospadias, uses apposing fully mobilized meatal based skin flaps. Cosmetic and functional results are excellent, with only 3.5% of the patients requiring reoperation. Because the surgical technique does not depend on the configuration of the glans, depth of the urethral groove, caliber of the urethral meatus or even whether the patient has been circumcised, it is particularly suitable for training residents who can perform a single operation to correct a wide variety of cosmetic deformities.

Hormonal regulation of sexual differentiation.

F eta1 sex differentiation can be defined as the acquisition of male or female characteristics in primordia initially identical in fetuses of both sexes. These include the gonads, genital tract, and external genitalia, the appearance of which determine the legal sex assigned to the newborn. Intersex disorders are characterized by discrepancy or ambiguity of sex orientation at one or several of these levels. folds or labioscrotal swellings. After the corpora cavernosa and glans have differentiated, the genital tubercle elongates to form the phallus, whose ventral surface is depressed by a deep furrow, the urethral groove. No sex difference is detectable in human fetuses before 9 to 10 weeks.’

Meatal Advancement And Glanuloplasty Hypospadias Repair After 1,000 Cases: Avoidance of Meatal Stenosis And Regression

We first described the meatal advancement and glanuloplasty (MAGPI) procedure in 1981 as a technique to repair distal hypospadias. During the last 10 years our experience has increased to more than 1,000 cases. Case selection is critical to surgical outcome. Excessively thin or rigid ventral parameatal skin, or a meatus that is too proximal or too wide must be avoided. To prevent the ventral meatal wall from falling back and leaving a retrusive meatus, the glans wrap to support the advanced ventral urethral wall requires a solid approximation of glans tissue in 2 layers. Meatal stenosis may be avoided by an adequately deep dorsal Heineke-Mikulicz tissue rearrangement, making the incision from within the urethral meatus distally into the glanular urethral groove. The MAGPI procedure is routinely performed on an outpatient basis without urinary diversion. A review of our experience with 1,111 cases during a 12-year period reveals that a secondary procedure was required in only 1.2%. The overall success rate with the MAGPI procedure suggests that it should continue to be an important operation in the reconstruction of distal hypospadias.

A study of quantitative and qualitative abnormality of androgen receptor in patients with hypospadias associated with enlarged prostatic utricle

The prostatic utricle, a rudimentary structure present in the male prostatic urethra, is currently thought to be of mixed origin, with its cranial portion being derived from müllerian duct and caudal segment from wolffian and müllerian ducts and the urogenital sinus. Enlargement of prostatic utricle has often been demonstrated in patients with hypospadias and its incidence increased according to the severity of hypospadias. It has been suggested that insufficient androgenic stimulation of the urogenital sinus and urethral groove during the critical period of sexual differentiation may cause this entity. Since 5 alpha-dihydrotestosterone (DHT) is a major androgen for the normal development of urogenital sinus, androgen receptor levels in the patients with hypospadias associated with enlarged prostatic utricle may concern this ontogenesis. Fibroblasts derived from penile skin in these patients were assayed for androgen receptor levels using dispersed whole cell binding assay after Eil (1970). Thermostability of androgen receptor in the same fibroblasts was also evaluated by the remaining androgen receptor activity after incubation at 42 degrees C, and expressed as a ratio (percentage) to the androgen receptor activity in the incubation at 22 degrees C. Preputial skin of endocrinologically normal boys in the same range of age (3 to 8 years) was served as controls. There was a significant difference in averages of maximum binding capacities of [3H]DHT to the androgen receptor between those of controls (n = 4) and patients with grade II utricle (n = 4) (89 +/- 5.7 (SE) x 10(2) sites/cell vs. 37 +/- 7.1 x 10(2) sites/cell).(ABSTRACT TRUNCATED AT 250 WORDS)

The MAGPI Hypospadias Repair in 1111 Patients

The meatal advancement and glanduloplasty (MAGPI) procedure was first described in 1981 for the repair of distal hypospadias. In the past decade, our experience has grown to more than 1000 procedures. An excellent surgical result requires careful case selection, avoiding cases with thin or rigid ventral parameatal skin or a meatus too proximal or too wide. The glans wrap to support the advanced ventral urethral wall requires a solid tissue approximation in two layers to prevent a retrusive meatus. Meatal stenosis can be avoided by assuring an adequate dorsal Heineke-Mikulicz tissue rearrangement and making an incision from within the urethral meatus well distally into the urethral groove. The MAGPI procedure routinely is performed on an outpatient basis without any urinary diversion. Our experience in 1111 cases during 12 years has required a second procedure in 1.2% of cases. The overall success rate with the MAGPI procedure suggests that it should continue to be used in the repair of distal hypospadias.

Cecil Urethroplasty with Concurrent Scrotoplasty for Repair of Hypospadias

During 13 years about 8 per cent of 234 patients operated upon for hypospadias presented surgical problems of reconstruction of the urethra from the urethral meatus proximal to the penoscrotal junction. These cases commonly are referred to as perineal or penoscrotal hypospadias. The problem occurs when the urethral groove fails to develop adequately and the scrotal folds have failed to rotate caudally. This hypospadias is in contrast to penoscrotal or distal hypospadias, when the urethral groove is developed but fusion is incomplete. In these patients the Cecil procedure has been used but modified to extend the urethra from behind the penoscrotal junction to the glans at the second stage of the urethroplasty. The modification consists of rotating the scrotum caudally from its high location. The tension and acute angulation that contributed to frequent complications previously associated with such attempts have been avoided and results are satisfactory.

Etiologic Considerations in Penoscrotal Hypospadias Repair

Superficial location of fibrous bands causing chordee in patients with penoscrotal hypospadias has been demonstrated by microscopic and gross photographs. Our technique to manage this problem is similar to that described by Allen and Spence and by King for distal hypospadias and has been used in 120 patients. The technique involves the repair of the embryologic penile defect by advancing the closure of the urethral groove and transposing the scrotum to its appropriate caudal position. The repair is applicable in patients with failure of fusion rather than failure of the development of the urethral groove as in perineal hypospadias.