44 Reconstruction of urogenital defects
The reconstructive techniques for congenital urogenital defects are broad-ranging, and the indications for intervention vary from emergent to elective. Herein the authors will discuss the normal development of the urogenital tract, followed by a discussion of some common female and male disorders and their surgical repairs. Cloacal and urogenital sinus disorders, as well as variant presentations that may include clitoromegaly, exstrophy, and/or epispadias, will be addressed first. What follows will concentrate on the spectrum of hypospadias disorders and some representative surgical techniques.
In general, reconstructive techniques for urologic disorders have satisfactory outcomes, but the importance of proper surgical timing and patient selection may not be understated. Vaginal agenesis is associated with Mayer–Rokitansky–Kuster–Hauser syndrome, wherein the proximal two-thirds of the vagina is absent. A mesonephric duct abnormality has been proposed as the etiology, with diagnosis often occurring in the workup of primary amenorrhea. Potential problems after vaginoplasty may include graft foreshortening, injury to adjacent urinary structures, and problems secondary to prolonged postoperative immobilization.
Bladder exstrophy tends to occur in nulliparous, young females’ offspring, with a recurrence risk of 1 : 275 and a risk of 1 : 70 in progeny. Patients have a low-set umbilicus and wide pubic diastasis. The pubic bone is shortened by 30%, with external rotation of the posterior pelvis. The clitoris or penis is short and bifid, and the urinary sphincter mechanism is underdeveloped. Nearly all patients have radiographic evidence of vesicoureteral reflux, and the incidence of inguinal hernias is increased. Treatment is discussed primarily in Volume 4, Chapter 13.
Cloacal exstrophy occurs when the anterior rectal and bladder walls do not develop. Prenatal ultrasound may illustrate an anterior infraumbilical cystic mass with separated pubic rami, rocker-bottom feet, and meningomyelocele. The newborn will have an exstrophied, shortened cecum that separates two exstrophied hemibladders. The ileum is prolapsed, the testes undescended, and the penis or clitoris small and bifid. The cloacal membrane is thought to have been persistent or overgrown, preventing mesenchymal ingrowth and thereby resulting in fusion of the genital ridges caudal to the membrane. Similar to bladder exstrophy, the posterior pelvis is externally rotated, the pubis is shortened, and pubic diastasis may be severe. Other associated abnormalities include spina bifida, lower limb deformities, uterine and vaginal duplication or agenesis, upper urinary tract anomalies, and gastrointestinal disorders, including short-gut syndrome.
Hypospadias occurs when the development of the urethral spongiosum and prepuce halts, resulting in a meatal location proximal to that of the distal glans. A hypospadic meatus is often accompanied by penile chordee as the normal embryological correction of curvature is likewise arrested. The severity of hypospadias is dictated by meatal location, ranging from perineal to glanular (Figs 44.1, 44.2). The more severe the hypospadias, the more likely it is accompanied by chordee and penoscrotal transposition (Figs 44.3 and 44.4).
Fig. 44.1 Spectrum of hypospadias.
(Reproduced from Wein: Campbell-Walsh Urology, 9th ed. © 2007 Saunders.)
Vaginal agenesis was first documented in the 16th century, with the first repairs described 300 years later. In 1898, Abbé1 described dissecting a neovaginal canal and lining it with split-thickness skin grafts situated over a temporary rubber stent. The procedure was popularized by McIndoe,2 who published a series of 63 such repairs. The usage of bowel, both small and large, as well as buccal mucosa and cultured vaginal tissue has been reported.3,4 Nonoperative approaches have also been employed, first through manual pressure and subsequently through the use of a modified seat-based dilation system.5,6 The resultant neovagina is lined by cutaneous squamous epithelium and requires external lubrication for intercourse.
The first description of bladder exstrophy repair was by Sweetser et al. in 1952.7 The first successful cloacal exstrophy repair was reported in 1960 by Rickham.8 The flourishing of neonatal intensive care over the last 50 years has resulted in near-universal survival for these infants.
Over 300 repairs for hypospadias have been described. Galen is credited with the first descriptions of hypospadias and chordee in the second century ad, with Vesalius, amongst others, elaborating on the disease description.9 The first millennium contained descriptions of amputation distal to the meatus with or without penile skin stretching; the second thousand years was characterized by tunneling and cannulation procedures in which a penile tunnel was repeatedly catheterized until it epithelialized.9 Many modern techniques have strong resemblance to procedures first described centuries ago. The concept of creating a tube in situ was documented in the 19th century by Anger,10 who overlapped tubularized flaps adjacent to the urethra, and Thiersch and Duplay,11 who incised tissue adjacent to the urethral groove, allowing for dorsal urethral closure. Duplay was also studying meatal advancement techniques. Pedicle skin grafts may be traced to Van Hook, who utilized a preputial pedicle flap in 1896.12 The utilization of free flaps was pioneered by Nové-Josserand,13 who wrapped a penile and preputial autograft around a catheter and tunneled the graft from glans to perineum. These concepts, all arising over 100 years ago, remain central to hypospadias repair today.
The cloaca appears during the second gestational week, with the urorectal septum forming during week 4 (Fig. 44.5). The urorectal septum fuses with the cloacal membrane by week 7. Defects of the cloacal membrane may result in bladder or cloacal exstrophy and epispadias. The mullerian ducts fuse to become the uterovaginal canal. Distally, the urogenital sinus forms the vestibule and the intervening sinovaginal bulbs canalize to form the distal vaginal canal. Paramesonephric abnormalities are frequently associated with ipsilateral renal anomalies, partly based upon their proximity during development. Anomalies of agenesis and fusion may occur. When the urogenital sinus fails to develop into the distal vagina, atresia results; agenesis occurs when the proximal third of the vagina fails to develop in a 46XX phenotypic female. Transverse septa arise from failure of fusion or canalization of the urogenital sinus and mullerian ducts. Meyer–Rokitansky–Kusler–Hauser syndrome consists of mullerian aplasia, often accompanied by renal and cervicothoracic dysplasias.
Fig. 44.5 Development of the urogenital tract.
(Modified from Larsen WJ: Human Embryology. New York, Churchill Livingstone, 1997.)
Between weeks 7 and 8 of gestation, the male gonads differentiate secondary to the transcription of the SRY gene, thereby producing testosterone. The distance between anus and genitalia increases, the phallus elongates, the genital folds fuse, the preputial folds form and fuse dorsally, and during the 11th gestational week, the urethral folds fuse ventrally. If the genital folds fail to fuse, as in hypospadias, the preputial folds also fail to fuse ventrally, resulting in excessive dorsal preputial tissue. By week 16, the glandular urethra forms. The glandular portion of the urethra is lined by squamous epithelium which likely also arises from urogenital sinus origin, but then undergoes differentiation.14 Histologically, the hypospadic urethral plate contains sinusoids of urethral spongiosum and no scar tissue. The innervation of the hypospadic penis is like that of the normal penis: the pedendal nerve gives off the dorsal nerve which travels as two bundles on either side of 12 o’clock.
The incidence of vaginal agenesis is 1 : 5000 female births, congenital adrenal hyperplasia 1 : 5000–15 000, bladder exstrophy 1 : 30 000 with male-to-female ratio 3 : 1, and cloacal exstrophy 1 : 800 000, with male-to-female ratio 2 : 1. The incidence of hypospadias is roughly 1 : 300 male births, an increase from 2 : 1000 male births in 1970. There is nearly a ninefold increase in hypospadias in monozygotic twins.
Urogenital sinus abnormalities may be isolated or associated with congenital adrenal hyperplasia, most often due to 21-hydroxylase deficiency. Overdevelopment of the cloacal membrane preventing medial migration of mesenchyme with subsequent membrane rupture underlies current models of the exstrophy–epispadias complex. Cloacal exstrophy is associated with cardiovascular, central nervous system, respiratory, gastrointestinal, and musculoskeletal abnormalities. Most cases are sporadic, with unbalanced translocations being hypothesized as causative in select cases. Neurologic and spinal defects may be related to dorsal mesenchymal disruption or underlying tendency for separation of the spinal cord from vertebrae in the presence of a cloacal exstrophy. Regarding hypospadias, a polygenic, multifactorial etiology is most likely. Some cases may be caused by testosterone, dihydrotestosterone, or androgen receptor deficiencies, but these are found in only 5% of cases. Theories of chordee include incomplete development of the urethral plate, abnormal urethral meatal mesenchyme, and disproportional corporal growth.
The workup of a newborn with ambiguous genitalia should involve multiple disciplinary teams and critical associations such as congenital adrenal hyperplasia should be ruled out. Fluid and electrolyte balance and blood pressure control should be maintained. Examination should note any suprapubic mass or ascites, sacral dimples, genitalia curvature and size, palpability of gonads, location of anus and perineal orifices, and pigmentation. Karyotype and adrenal biochemical studies should be undertaken, with prompt replacement of cortisol and fludrocortisone in cases of congenital adrenal hyperplasia. In utero exposure to androgenic substances should be investigated, as should a family history of infantile death. Radiographic and endoscopic evaluations of the genitalia and urinary tract are indicated, including abdominal X-ray and ultrasound, genitography, echocardiography, lumbar magnetic resonance imaging, and cystoscopy with vaginoscopy. Exstrophy is often diagnosed in utero, and neonatal intensive care is mandatory. Older patients with isolated vaginal atresia or transverse vaginal septa may present with amenorrhea or a distended upper vagina.
Hypospadias is frequently diagnosed at birth on physical examination, although later diagnoses are not uncommon. Patients with impalpable gonads and hypospadias have a disorder of sexual differentiation until proven otherwise, and karyotype is indicated.
For the patient with vaginal agenesis, the techniques and timing remain controversial. It is apparent that the majority of patients undergoing vaginoplasty as infants require additional vaginal surgery. When vaginal defects are associated with clitoromegaly, as in congenital adrenal hyperplasia, the surgeon has two fundamental options: perform an uncomplicated clitoroplasty with deferred vaginoplasty or a complex clitorovaginoplasty with deferred minor introitus repair in postpuberty.
Patients presenting with the exstrophy–epispadias complex are managed with a staged procedure.15 Bladder and abdominal closures with bilateral osteotomy are performed in the newborn period. Epispadias repair occurs 6–12 months later, and bladder neck reconstruction with ureteral reimplantation in another 4–5 years if indicated.
Patient selection is most pertinent to hypospadias repair. The meatal location, glans volume, penile length, presence of penoscrotal transposition and/or chordee, and width and depth of the urethral plate all weigh in the surgeon’s selection of technique. In general, distal hypospadias may be treated by tubularized incised plate (TIP) procedure with meatoplasty and glanuloplasty (MAGPI) techniques, while proximal hypospadias are frequently treated by two-staged graft or onlay island flap repairs.
The optimal timing for hypospadias repair is 6 months of age in a full-term male. Ninety-two percent of pediatric urologists perform a TIP procedure for distal hypospadias .13 Proximal hypospadias without curvature is repaired by TIP or onlay island flap by equal proportions of urologists, while proximal hypospadias with severe chordee is most often repaired by a staged repair.16 Intramuscular testosterone injections of 25 mg/dose or 2 mg/kg/dose may be administered up to three times prior to repair in an attempt to improve penile vascularity and tissue robustness, thereby facilitating subsequent surgery.
Reconstruction may involve grafts of the skin, intestine, or buccal mucosa. In the Abbé–McIndoe procedure, a Y incision is made on the median raphe between urethra and anus. A Foley catheter facilitates dissection posterior to the urethra. The neovaginal walls are formed by partial-thickness skin grafts harvested from the hip and buttock. Partial-thickness grafts are best in the adult population, while full-thickness grafts may be utilized in adolescents. The exact dimensions of the neovagina must be tailored to the individual, with a young adult having depth of 10–14 cm. The skin grafts are sutured to one another with epidermal surface positioned to line the interior of the vagina. These grafts may be molded around a Heyer–Schulte vaginal stent which is then seated and inflated into position to facilitate take. The Y incision flaps are approximated to the graft edges, and the labia majora are sutured to each other to prevent distal migration of the stent. The patient remains on bedrest for at least 5 days and constipating medication is administered. After this, the labia are separated, the stent deflated and the graft examined. Upon discharge, the patient is taught how to remove, wash, and replace the stent daily. A stent or dilator is encouraged for a minimum of 6 months to minimize retraction, and intercourse is appropriate after 3 months. Vulvobulbocavernosus, gracilis, or rectus myocutaneous flaps are frequently utilized for vaginal reconstruction in the adult population following radical pelvic surgery.
The use of bowel results in mucus production which may require daily douching and result in odor or ulcerations.17 While bowel preparation has historically been advised, the authors have found it to be unnecessary.18,19 A Pfannenstiel incision is appropriate, although a midline incision may also be employed. A 10-cm segment of mobile sigmoid or ileum may be taken out of continuity and anastomosed directly to the skin dimple (Fig. 44.6). While some surgeons detubularize and subsequently fold the bowel to form the neovagina, the authors find this unnecessary and perform a simple proximal-limb closure with 2-0 absorbable suture. The distal aspect of the bowel limb is anastomosed in recessed fashion to skin flaps or the rudimentary vagina is cases of proximal atresia. The bowel anastomosis may be hand-sewn or stapled.