Pediatric Genitourinary and Renal Disorders

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20 Pediatric Genitourinary and Renal Disorders

Suzanne Lippert, N. Ewen Wang

image      Key Points

• Children often cannot differentiate between abdominal pain and groin pain—a complete physical examination is therefore necessary.

• The pathophysiology, clinical findings, and treatment of paraphimosis, testicular torsion, and priapism are similar in both the pediatric and adult population. They are emergencies that require immediate intervention.

• The most common cause of acute renal failure in children is hemolytic-uremic syndrome.

• Poststreptococcal glomerulonephritis is the most common cause of acute glomerulonephritis. IgA nephropathy is the most commonly diagnosed cause of glomerulonephritis in adolescents.

• One third of patients with Henoch-Schönlein purpura have renal involvement. This disorder is the most common form of vasculitis in childhood and is usually characterized by the triad of abdominal pain, arthritis, and purpura.

Developmental Basis of Genitourinary Tract Pathology

The male genital organs originate within the abdominal cavity and then migrate externally during fetal development. Delays in testicular migration explain much of the pathology of scrotal masses. The testes, attached to their blood supply, drag their peritoneal covering (known as the tunica vaginalis) through the inguinal canal and into the scrotal sac.

The left testicle usually completes migration before the right testicle, thus explaining the increased frequency of right-sided inguinal hernias and undescended right testicles. Impediments to migration cause cryptorchidism. Failure of the peritoneal space to close after testicular migration can lead to hydroceles and inguinal hernias. Failure of fixation of the testes within the scrotal sac allows testicular torsion to occur. Differences in venous return make left-sided varicoceles much more common than right-sided ones.

Posterior urethral valves represent a disturbance in urethral development in males that is the leading cause of lower urinary tract obstruction in neonates. One third of patients with posterior urethral valves progress to end-stage renal disease, and 10% to 15% of children who require renal transplantation have posterior urethral valves.

Developmental Anatomy of the Kidneys

The full complement of nephrons is present at birth, although newborn nephrons are heterogeneous in glomerular size and proximal tubule length. Anatomy and function mature postnatally. Although fetal urine is excreted into the bladder by 10 to 11 weeks of gestation, the ability to conserve and excrete sodium, concentrate urine, and reabsorb substrates such as glucose evolves to maturity over the first 2 years of life. In utero, the glomerular filtration rate (GFR) is minimal secondary to placental function; at birth, the GFR is 10% of adult values and matures by 12 to 24 months of age. Therefore, an increase in an infant’s creatinine to “normal” adult ranges can indicate pathology.

Genitourinary Disorders

Cryptorchidism (Undescended Testis)

By birth, the testes have usually descended from the abdominal cavity into the scrotum; only 3% to 5% of full-term newborns have an undescended testicle. Although spontaneous descent does occur in the first year of life, 0.8% of males are still affected at 12 months of age, and spontaneous descent becomes increasingly unlikely after 6 months. With a careful physical examination, 80% of undescended testes are palpable, most commonly in the inguinal canal. Children with undescended testes are at higher risk for torsion, trauma, and malignancy.

Clinical Presentation and Diagnosis

Children with undescended testes are ideally identified by careful physical examination before any complications occur. The differential diagnosis of testes that are not palpable includes undescended, retractile, and absent testes. Children younger than 1 year should be examined while they are relaxed in a warm bath because the testes can be retracted during examination. Children older than 1 year whose testes are not palpable during routine physical examination should be evaluated by a urologist. Histologic deterioration of the testes, presumably secondary to increased ambient temperature, can begin as early as 6 to 12 months and is correlated with infertility, even in cases of unilateral undescended testes. Abdominal pain in children with undescended testes should prompt emergency evaluation for intraabdominal torsion.

Treatment

The optimal time for surgical intervention is between 6 and 12 months.

Hydrocele

A hydrocele (Fig. 20.1) is a collection of fluid that accumulates within the layers of the tunica vaginalis and may or may not communicate with the peritoneal space. Hydroceles are often present at birth and occur most frequently on the right side because of delayed migration of the right testicle. Noncommunicating hydroceles in older children and adolescents should prompt examination for epididymitis, orchitis, trauma, tumor, or testicular torsion.

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Fig. 20.1 Abnormalities of the processus vaginalis.

(From Zitelli BJ, Davis HW. Atlas of pediatric physical diagnosis. 5th ed. Philadelphia: Mosby; 2007. Fig. 17-133.)

Clinical Presentation and Diagnosis

Hydroceles are usually painless. Physical examination reveals enlargement of the scrotum that may transilluminate because of its cystic structure. Ultrasonography is necessary to exclude acute pathology if the infant or child appears to be in pain. The majority of hydroceles not associated with inguinal hernia tend to resolve spontaneously between 12 and 24 months of age.

Treatment

Hydroceles associated with an inguinal hernia, those that communicate with the peritoneal space, or those that occur or persist after 2 years of age require outpatient surgical repair.

Varicocele

A varicocele is a collection of spermatic venous varicosities in the scrotum caused by incomplete drainage of the pampiniform plexus (Fig. 20.2). They are rare in children younger than 10 years. Varicoceles most commonly develop between 10 and 15 years of age and have an incidence of approximately 15% in males.1,2 The majority (85% to 95%) of varicoceles are left sided, the result of spermatic venous incompetence secondary to drainage of the left spermatic vein into the renal vein at a right angle.

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Fig. 20.2 Varicocele.

(From Zitelli BJ, Davis HW. Atlas of pediatric physical diagnosis. 5th ed. Philadelphia: Mosby; 2007. Fig. 14-44.)

Clinical Presentation and Diagnosis

Right-sided varicoceles should prompt an evaluation for intraabdominal pathology such as thrombosis or a tumor causing compression of the inferior vena cava.3 Similarly, sudden onset of a left-sided varicocele should raise suspicion for renal cell carcinoma with obstruction of the left renal vein. The differential diagnosis of varicoceles and other scrotal masses is outlined in Table 20.1.

Table 20.1 Age-Based Differential Diagnosis of Pediatric Scrotal Masses and Pain

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Varicoceles can cause mild discomfort and may lead to infertility in adult males. They are usually diagnosed on routine physical examination and are characterized by a full hemiscrotum without skin changes and a classic “bag of worms” finding on palpation.

Treatment

A varicocele is generally an incidental finding in adolescence and is not an emergency. Referral to outpatient urology is appropriate.

Testicular Torsion

The pathophysiology, clinical findings, and treatment of testicular torsion in the pediatric population is similar to that in adults. Detailed discussion of torsion can be found in Chapter 111.

Inguinal Hernia

An inguinal hernia occurs when an intraabdominal organ, usually intestine, herniates into a patent processus vaginalis (see Fig. 20.1). An incarcerated hernia refers to an intestinal loop that is not reducible. A strangulated hernia results when the blood supply to the intestinal loop is obstructed and bowel ischemia ensues.

Epidemiology and Pathophysiology

Inguinal hernias occur in 15 of every 1000 live births. The incidence in premature and low-birth-weight infants is much higher (approximately 30%), whereas the incidence in males is three to four times higher than that in females. They are most commonly identified during the first year of life, with a peak in diagnosis during the first month.

Indirect hernias are more common on the right side (60%) because of later testicular descent into the scrotum. If a left-sided hernia exists, there is a strong possibility that an occult right-sided hernia is present. A family history of hernia, prematurity, or undescended testicle is associated with inguinal hernias.

Clinical Presentation

Incarceration is more common with small hernias and occurs frequently during the first 6 months of life, less commonly after 2 years of age, and rarely after the age of 5. Strangulation and perforation can occur within 2 hours of decreased blood flow. Incarceration occurs more frequently in females; however, it is the ovaries, not the intestines, that herniate and become incarcerated.

Treatment

Given the high frequency of incarceration in the first year of life, hernias found on routine examination without symptoms should be referred for surgical repair. Approximately 90% of complications can be avoided if surgery is performed within the first month after diagnosis.

Idiopathic Scrotal Edema

Idiopathic scrotal edema is manifested as painless erythema and induration of the scrotum. More than 75% of cases occur in boys younger than 10 years. Two thirds of cases are unilateral.

Clinical Presentation

Patients may complain of pruritus. Edema and erythema may extend to the phallus, groin, and abdomen. The testes and epididymis will have no palpable masses, and systemic symptoms are rare.

Treatment and Disposition

Idiopathic scrotal edema is a diagnosis of exclusion. If acute pathology has been excluded, patients can be discharged home with outpatient follow-up. Most cases resolve spontaneously within a few days and do not require specific treatment. The recurrence rate is 21%.

Carcinoma

Testicular and scrotal cancer accounts for 1% of solid tumors in children. The incidence is increased in patients with bilateral cryptorchidism.

Clinical Presentation and Diagnosis

On examination, a painless unilateral mass can be palpated separately from the testis; there may also be a sensation of fullness, tugging, or increased weight in the scrotum associated with testicular enlargement. A reactive hydrocele is present in 7% to 25% of patients and may lead to a delay in diagnosis. Further examination reveals a firm mass, either smooth or nodular, that does not transilluminate. Lymphadenopathy, petechiae, abdominal masses, hepatosplenomegaly, or gynecomastia may be present. Lymphoma and leukemia can metastasize to the testicles and be manifested similarly.

A complete blood count, urinalysis, urine test for human chorionic gonadotropin (produced by germ cell tumors), and testicular ultrasound images should be obtained.

Treatment

Management consists of prompt urologic and oncologic consultation for biopsy and staging.

Phimosis

Phimosis is a constriction of the penile foreskin that results in an inability to retract the prepuce over the glans. A fully retractable foreskin is present in 4% of newborns, 50% of 1-year-olds, 80% of 2-year-olds, and 90% of 4-year-olds. In the remaining cases, the foreskin may not be retractable until puberty.4

Clinical Presentation

Although most cases of phimosis in children are physiologic, symptoms may include pain, hematuria, and in severe cases, urinary obstruction. Adolescents may complain of pain on erection secondary to tension on the foreskin from glandular adhesions. Phimosis can also result from trauma, infection, chemical irritation, and poor hygiene or as a complication of circumcision. Severe stenosis or obstructive uropathy can result from chronic symptomatic phimosis.

Treatment

Because the ability to retract the foreskin is age related, parents should not forcefully retract the prepuce. Good hygiene should be taught. If the child has signs of urinary outlet obstruction, dilation of the meatus by gentle use of forceps is warranted.

Steroid preparations (0.05% to 5% betamethasone cream two to four times daily or 1% hydrocortisone cream two to three times daily) have been used with varying success.5 Severe phimosis may mandate incision of the dorsal inner foreskin by a urologist.

Paraphimosis

Paraphimosis is a urologic emergency in which the foreskin of an uncircumcised male is retracted behind the glans penis and acts as a constricting band (Fig. 20.3). The resulting venous and lymphatic congestion precludes returning the foreskin to its normal position, threatens arterial blood flow to the glans penis, and can result in penile necrosis, gangrene, or infarction of the glans over a period of hours to days. In infants and young boys, paraphimosis most commonly results after cleaning by a caretaker.

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Fig. 20.3 Paraphimosis in a catheterized patient with an edematous prepuce proximal to the glans.

(From Zitelli BJ, Davis HW. Atlas of pediatric physical diagnosis. 5th ed. Philadelphia: Mosby; 2007.)

Clinical Presentation

Paraphimosis is accompanied by penile pain and swelling and must be differentiated from balanoposthitis, tourniquet syndrome, and the generalized edema seen with renal, cardiac, or liver failure. Irritable and inconsolable male infants should be examined for evidence of paraphimosis. Urinary obstruction can be a late finding.

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