137: Surgical Diseases of the Newborn: Urologic Disorders

Renal masses are discussed in Chapter 136.

Testicular descent can occur prior to birth or in the first 6 months of life, after which cryptorchidism or undescended testis occurs in up to 10% of premature infants and 0.8% of term infants.

Testicles may be nonpalpable or located along the course of the inguinal canal, in the superior scrotum, retroscrotally, and in the perineum. The ipsilateral scrotum may be hypoplastic, and a hernia or hydrocele may also be present. Cryptorchidism may be associated with other anomalies such as disorders of sexual development (especially in the presence of hypospadias), prune-belly syndrome, bladder exstrophy, pituitary disorders, and multiple other syndromes.

Careful examination with a warm hand sweeping lateral to medial from the anterior superior iliac spine to the ipsilateral groin is the most effective method of distinguishing a palpable from a nonpalpable testis.

1. Palpable testes. A palpable testis must be distinguished from hernia, hydrocele, nubbin, and a long, looping portion of vas or epididymis. Infants with a palpable undescended testis should be followed to ensure proper descent by 6 months of age.

2. Nonpalpable testes. Imaging studies are not indicated to help identify nonpalpable testes. If testicles are nonpalpable at 3 months of age, referral to a pediatric urologist is needed. If both testes are nonpalpable, a disorder of sexual differentiation, including congenital adrenal hyperplasia in a genetic female, should be considered. The incidence of disorders of sexual differentiation in patients with hypospadias and bilateral nonpalpable testis is high and warrants a karyotype evaluation.

Spontaneous descent is possible until 6 months of age, after which there is only a 1% likelihood of spontaneous decent. After 6 months of age, orchiopexy is indicated for malpositioned palpable testicles. For nonpalpable testes, laparoscopy is indicated to localize the testis or identify the characteristic blind-ending spermatic artery and vas deferens entering the internal ring.

The differential diagnosis of an abnormal testicular examination in an infant includes the following:

1. Hydrocele. Fluid within the tunica vaginalis and/or along the spermatic cord. Hydroceles may have continuity with the peritoneal cavity via a patent processus vaginalis (communicating hydrocele), or be confined to the tunica vaginalis and spermatic cord distal to an obliterated processus vaginalis (noncommunicating hydrocele).

2. Hernia (most commonly indirect inguinal). Protrusion of intra-abdominal contents through a patent processus vaginalis lateral to the epigastric vessels along the spermatic cord.

3. Testicular torsion. Twisting of the spermatic cord with reduction or cessation of testicular blood flow.

4. Testicular tumor. Rare in newborns.

A noncommunicating hydrocele presents as a painless testicular enlargement that is not reducible and does not change in size. Hernias and communicating hydroceles both present as a bulge in the groin or testicular enlargement that changes size and is usually more prominent with increased intra-abdominal pressure. Hernias are usually painless; however, they may become painful if intraperitoneal contents become incarcerated. Scrotal discoloration and testicular induration with or without significant swelling is typical of perinatal testicular torsion. In the rare instance of a testicular tumor, a painless, firm mass can be palpated within the testicle or paratesticular soft tissue.

Diagnosis is based on the history and physical examination. Ultrasound can quickly assess for torsion and evaluate for a potential mass.

Hernias and communicating hydroceles should be repaired when diagnosed. The majority of nonreducible hydroceles will spontaneously resolve within the first year of life and warrant observation. Perinatal torsion should be explored urgently in conjunction with a contralateral orchiopexy. Rare cases of scrotal masses should be managed via an inguinal orchiectomy.

Hypospadias is defined by 3 components: altered development of the distal urethra, a dorsal hooded prepuce with lack of ventral prepuce, and ventral penile curvature. The megameatus variant is an isolated urethral defect with a normal complete foreskin and no curvature.

The defect is usually identified at birth with the classic findings of dorsal hooded foreskin, ventral curvature, and a proximally located urethral meatus. Megameatus may be identified during or after circumcision.

Diagnosis is based on physical examination findings. Hypospadias is classified by the location of the urethral meatus and degree of curvature. About 10% of patients also have cryptorchidism, and up to half of these may have disorders of sexual development (see Chapter 91). Karyotyping should be performed on infants with proximal hypospadias and nonpalpable testes.

Preputial skin is used in surgical correction of hypospadias; therefore, newborn circumcision should not be performed if the defect is identified at birth. The need for repair and surgical approach is based on the severity of the defect and the cosmetic appearance of the phallus. Repair is an elective procedure, ideally performed between 6 and 18 months of age.

Isolated epispadias is the least severe of the “exstrophic” embryologic malformations that results in incomplete development of the dorsal urethra.

In isolated epispadias, formation of the urethra is incomplete and the urethral plate is exposed dorsally. In males this results in dorsal curvature and incomplete fusion of the glans. Females present with a bifid clitoris and vagina that is positioned anteriorly. Involvement of the bladder neck is common, resulting in incontinence in both sexes.

Diagnosis is based on physical examination. Voiding cystourethrography may be useful in defining urethral and bladder anatomy, but is not required.

Surgical correction of curvature and urethral reconstruction is performed between 6 and 18 months of age. Reconstruction of the bladder neck and restoration of continence mechanisms is delayed until 4–5 years of age.

Thought to be due to altered development of the cloacal membrane, classic bladder exstrophy is defined by incomplete formation of the anterior abdominal wall, bladder, and dorsal urethra.

The anomaly may be identified prenatally or at birth, and it occurs more commonly in males (3–6:1). The epispadias malformation described previously is present in addition to a large abdominal wall defect occupied by the bladder plate.

Findings on prenatal ultrasound include lack of bladder filling, inferior umbilicus, widened pubic ramis, and lower abdominal mass. Physical examination findings include epispadias, external rotation of the pelvic bones, a wide pubic diastasis, anterior displacement of the anus, and a large abdominal wall defect with exposed bladder plate.

The bladder plate must be protected with a thin plastic covering or moist dressing. There has been debate within the pediatric urology community; however, today the majority of exstrophy patients undergo bladder closure, repair of the anterior abdominal wall, and restoration of pelvic anatomy within the first days of life. The epispadias defect is repaired either at that time or within the first year of life, with bladder neck reconstruction and repair of continence mechanisms being delayed until 4–5 years of age.

The most severe presentation of “exstrophic” embryologic malformations, cloacal exstrophy is defined by the same features of bladder exstrophy in addition to altered hindgut development and the presence of an omphalocele.

Prenatal ultrasound (US) findings of absence of bladder, infraumbilical anterior midline abdominal wall defect, omphalocele, and myelomeningocele were present in over 50% of patients with exstrophy. At birth, the omphalocele extends superiorly while the open bladder plate is divided by hindgut structures, which often include a segment of intussuscepted ileum. Genital malformations are similar to those seen in exstrophy except are more severe, often with complete separation of the phallus or clitoris.

In addition to the physical examination findings discussed previously, cloacal exstrophy is also associated with renal abnormalities, Müllerian fusion anomalies, intestinal anomalies, hip or limb defects, and neural tube defects.

As with classic exstrophy patients, the bladder plate should be protected with plastic wrap or a moist dressing. Imaging should include renal and spinal US and skeletal imaging. Reconstructive surgery consists of multiple staged procedures with the initial goal of closing the bladder plate in addition to repairing the omphalocele and any associated neural tube defects. Subsequent procedures are then needed to address the hindgut and genital malformations.

The triad consists of deficient abdominal musculature, bilateral cryptorchidism, and dilation of the urinary tract in a male.

“Prune belly” refers to the classic appearance of abdominal wall wrinkling and bulging flanks caused by varying degrees of abdominal wall deficiency. Presentation ranges from the most severe (category 1) disease associated with oligohydramnios, renal dysplasia, and pulmonary hypoplasia to category 3 with mild external features and stable renal function. The degree of renal dysplasia is the single most important factor in determining the severity of the disease.

Clinical diagnosis is based on the classic appearance of the abdominal wall and associated genitourinary anomalies.

Initial management consists of antibiotic urinary tract infection (UTI) prophylaxis and assessment of renal function. The majority of patients will benefit from surgical repair of the abdominal wall defect and cryptorchidism. More invasive surgical decompression of the urinary tract and radical reconstruction is controversial and is reserved for those patients with recurrent febrile urinary tract infections or deteriorating renal function.

Posterior urethral valves (PUVs) are aberrant folds of tissue that extend from verumontanum to the external sphincter, creating a urethral obstruction.

The presentation of PUVs encompasses a wide spectrum, from mild bladder outlet obstruction to severe obstructive uropathy with renal insufficiency, oligohydramnios, and pulmonary hypoplasia. The majority of cases of PUVs present prenatally with bilateral hydroureteronephrosis and megacystis, with or without oligohydramnios.

Voiding cystourethrogram (VCUG) is the gold standard for diagnosis and classically shows a thickened bladder wall, a dilated posterior urethra, and decreased urethral caliber beyond the verumontanum.

In cases diagnosed prenatally, in utero decompression of the bladder has been attempted with limited success. A randomized controlled trial (PLUTO trial), comparing intrauterine vesicoamniotic shunting and conservative care for fetal bladder outflow obstruction, showed an improvement in perinatal survival in those who underwent vesicoamniotic shunting in preliminary results. Postnatal treatment consists of placement of an indwelling catheter, initiating antibiotic prophylaxis, and elective cystoscopic ablation of the valves. Serial chemistries are needed to monitor renal function as maternal creatinine is cleared. However, decompression of the urinary tract will likely do little to improve renal function if significant renal dysplasia is present. Nadir serum creatinine of <0.8 in the first year of life suggests a better long-term renal prognosis.

Hydronephrosis is dilatation of the renal pelvis and calyces. Mild dilation of the renal pelvis is defined as an anteroposterior diameter of 5–10 mm between weeks 18 and 23 of gestation. Severe dilation is generally defined as an anteroposterior diameter >15 mm. Postnatally, hydronephrosis is classified as grade 1–4 based on the Society for Fetal Urology grading system.

Prenatal ultrasound will detect mild pelvic dilation in 2–5% of fetuses at 18–23 weeks; however, 80% will spontaneously resolve. Severe dilation, bilateral hydronephrosis, and oligohydramnios are all suggestive of a significant urinary tract obstruction. Vesicoureteral reflux (VUR) can cause hydronephrosis. With the common use of prenatal ultrasound, a large proportion of infants with significant VUR are now diagnosed long before they would present with UTI later in life.

Prenatal hydronephrosis is most commonly diagnosed at routine prenatal ultrasound. Postnatal evaluation is as follows: Renal/bladder ultrasound may be performed 24–48 hours immediately after birth, especially if bladder outlet obstruction is suspected. Mild unilateral dilation that persists on postnatal ultrasound is followed with a repeat ultrasound at 3 months of age. All infants with severe unilateral or bilateral hydronephrosis should be started on antibiotic prophylaxis and evaluated with a VCUG under current guidelines.

Serial ultrasounds are used to document stabilization/improvement of mild to moderate dilation. Normal postnatal US precludes the need for additional studies. The differential diagnosis is broad, and specific surgical management will be dictated by the underlying pathology.