99 PEDIATRIC UROLOGY
Kirstan K. Meldrum M.D., Mark P. Cain M.D.

1. A healthy 3-year-old girl develops a urinary tract infection (UTI). How should she be evaluated?

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After treatment of the infection, the patient should undergo a urinary tract evaluation (this recommendation stands even in a little girl after only one UTI). Evaluation includes a renal-bladder sonogram and voiding cystourethrogram (VCUG). Approximately 50% of children younger than age 12 years who present with a UTI are found to have abnormalities of the genitourinary tract. The most common abnormalities identified are vesicoureteral reflux, obstructive uropathies, and neurogenic bladder.

2. What is vesicoureteral reflux (VUR) disease?

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With VUR, urine refluxes from the bladder into the upper urinary tract. Primary VUR is caused by an inadequate valvular mechanism at the ureterovesical junction, presumably related to a shortened submucosal ureteral tunnel. One half of children with culture-documented UTIs have VUR.

3. Is VUR bad?

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Sterile reflux is unlikely to cause renal damage; however, persistent reflux of infected urine leads to pyelonephritis and progressive renal scarring. Currently, renal scarring is the fourth leading cause for renal transplantation in children. The combination of VUR and elevated bladder storage pressures (e.g., neuropathic bladder or bladder outlet obstruction) is particularly harmful to the kidney.

4. What are the indications for surgical correction of VUR?

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Reflux disappears spontaneously in many children; however, high-grade reflux, especially when bilateral, is unlikely to resolve spontaneously. Children with high-grade reflux or breakthrough UTIs despite antibiotic prophylaxis should be managed surgically. Surgical management is also appropriate in children with reflux persisting into late childhood or adolescence.

5. What is the most common cause of antenatal hydronephrosis?

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Ureteropelvic junction (UPJ) obstruction. Hydronephrosis is the most common abnormality detected on prenatal ultrasound and accounts for 50% of all prenatally detected lesions. Fifty percent of prenatal hydronephrosis, in turn, is caused by UPJ obstruction. UPJ obstruction is bilateral in approximately 20% of cases and is associated with VUR in 15% of cases.

6. What is the most common cause of UPJ obstruction?

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Intrinsic stenosis. Less common causes include lower pole (of the kidney) crossing vessels, anomalous ureteral insertions, and peripelvic fibrosis.

7. Can UPJ obstruction resolve spontaneously? What are the indications for pyeloplasty?

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Yes, it can resolve spontaneously. Ultimately, only about 25% of children with evidence of UPJ obstruction require pyeloplasty. The indications for surgical intervention include worsening hydronephrosis, poor or declining renal function, pain, and the presence of a solitary kidney or bilateral hydronephrosis.

8. What is the Meyer-Weigert law?

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This law refers to the position of the ureteral orifices in patients with complete ureteral duplication. Occasionally, two ureteral buds develop independently from the mesonephric duct. As the ureteral buds are absorbed into the developing bladder, the bud located in a lower position along the duct (draining the lower pole of the kidney) is carried to a more cranial and lateral position. The ureteral bud located in a higher position along the duct (draining the upper pole of the kidney) is carried to a more caudal and medial position within the bladder. Lower pole ureters are more likely to reflux because of their lateral position within the bladder; however, upper pole ureters are more frequently obstructed and are more often associated with a ureterocele.

9. What is a ureterocele?

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A ureterocele is a cystic dilatation of the distal portion of the ureter. Ureteroceles are usually associated with the upper pole ureter of a duplicated collecting system; however, they also may develop from single ureters. They are usually ectopic (i.e., some portion of the ureterocele is positioned at the bladder neck or urethra) and frequently cause ureteral obstruction.

10. What is an ectopic ureter?

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A ureter with an ectopic opening at the level of the bladder neck or more caudally.
KEY POINTS: PEDIATRIC UROLOGY

1. The most common cause of antenatal hydronephrosis is ureteropelvic junction obstruction.
2. A ureterocele is a cystic dilatation of the distal portion of the ureter.
3. The most common location of an undescended testicle is the inguinal canal.
4. The most common cause of ambiguous genitalia in newborns is congenital adrenal hyperplasia, most commonly due to 21-hydroxylase deficiency.

11. What is the most common presenting symptom in a girl with an ectopic ureter?

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Incontinence. In females, an ectopic ureter will usually drain into the bladder neck, proximal urethra, or vestibule. The orifice also may be located in the vagina (25%) and, occasionally, the uterus. When the ectopic ureteral orifice is positioned below the external sphincter or within the female genital tract, incontinence can develop.

12. Do boys with ectopic ureters present with incontinence?

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No. The ectopic pathway in boys extends from the bladder neck through the posterior urethra to the mesonephric duct derivatives (i.e., vas deferens, epididymis, and seminal vesicle). Therefore, the ectopic ureteral orifice is always positioned above the continence mechanism.

13. What percentage of full-term male infants have an undescended testicle?

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Three percent. This number decreases to 0.8% by age 1 year.

14. What is the most common location of an undescended testicle?

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The inguinal canal (72% of undescended testicles). The testicle also may be located in the abdomen (8%) or prescrotal area (20%). Twenty percent of undescended testicles are nonpalpable at presentation; of these, 50% are absent completely.

15. Why should the testicle be brought back into the scrotum?

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Patients with cryptorchidism have a 40-fold increased risk of germ cell cancer compared with the normal population. Although positioning of the testicle within the scrotum does not alleviate this risk, it does permit routine, thorough testicular examination. Patients with cryptorchidism also are at risk for infertility. Histologic studies have demonstrated progressive germ cell loss in the undescended testicle beginning at age 18 months. Early orchiopexy can minimize the extent of germ cell loss and thereby decrease the chance of future infertility. In general, the higher the testicle (i.e., within the abdomen), the greater the risk of cancer and infertility.

16. What is the most common cause of bladder outlet obstruction in boys? In girls?

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Posterior urethral valves and ureterocele, respectively.

17. What are the urinary manifestations of posterior urethral valves?

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Posterior urethral valves are congenital leaflets of tissue that extend from the verumontanum to the anterior urethra in boys. They occur at an incidence of 1 in 8000 live male births. Posterior urethral valves cause bladder outlet obstruction, which, in turn, leads to variable degrees of bladder and renal injury. Severe obstruction may result in oligohydramnios, pulmonary hypoplasia, bladder hypertrophy, vesicoureteral reflux, hydroureteronephrosis, and renal dysplasia. Fifty percent of affected children have reflux, and 33% of them progress to end-stage renal disease.

18. What is a myelomeningocele? What are its urologic consequences?

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A myelomeningocele is a hernial protrusion of the spinal cord and its meninges through a defect in the vertebral column. The resulting neurologic injury causes, among other problems, bladder dysfunction. Patients with myelomeningocele usually are incontinent because of detrusor hyperactivity, detrusor hypoactivity, poor bladder compliance, inadequate outlet resistance, detrusor-outlet dyssynergy, or a combination of these factors. More importantly, patients with hyperactive, high-pressure bladders may develop upper urinary tract deterioration. Life-long follow-up is necessary because the neurologic lesion can change with time. Treatment goals include maintenance of a low-pressure urinary reservoir, prevention of urinary tract infections, prevention of upper urinary tract deterioration, and the achievement of continence.

19. What is the most common cause of ambiguous genitalia in newborns?

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Congenital adrenal hyperplasia, most commonly caused by a 21-hydroxylase deficiency.

20. What diagnostic evaluation should be performed in any male infant presenting with hypospadias and cryptorchidism?

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The presence of cryptorchidism and hypospadias should alert the physician to the possibility of an androgenized female. A karyotype should always be obtained before urogenital reconstruction.

21. What is the most common solid renal mass in infancy? In childhood?

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In infancy, it is congential mesoblastic nephroma. This is a benign tumor of the kidney that can be managed with surgical excision alone.
In childhood, it is a Wilms’ tumor. Wilms’ tumor is associated with Beckwith-Wiedemann syndrome, isolated hemihypertrophy, and congenital aniridia. The most important prognostic factors are tumor stage and histology. Treatment is multimodal, consisting of surgery, chemotherapy, and radiation.

References
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BIBLIOGRAPHY
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