bubble_chart Overview

Posterior urethral valves are the most common cause of urethral obstruction in infants and newborns. This condition occurs only in male infants, with the valves typically located at the distal end of the prostatic urethra. The valves are formed by mucosal folds and appear as a very thin membrane. During urination, the valves can cause varying degrees of obstruction.

bubble_chart Clinical Manifestations

Symptoms and signs: Children with posterior urethral valves may exhibit varying degrees of urinary obstruction symptoms. Common manifestations include weak urine stream, interrupted urination, dribbling, urinary tract infections, and sepsis. Severe obstruction can lead to hydronephrosis, with a palpable mass in the abdomen and a distended bladder in the lower abdomen. A few patients may have palpable hydronephrotic kidneys in both flanks. Most affected children experience growth retardation after birth, and apart from signs of chronic illness, physical examination may reveal no other findings.

bubble_chart Auxiliary Examination

Laboratory tests: Generally, there is azotemia and decreased renal concentrating function. Patients with chronic infections may present with anemia and infectious urine. Serum creatinine, blood urea nitrogen, and creatinine clearance rate are the best indicators reflecting the extent of renal function damage.

X-ray examination: Excretory bladder urography is the best method for diagnosing posterior urethral valves. Patients with a large amount of residual urine should undergo catheterization before imaging, and the urine from the catheter should be routinely sent for culture. In cases of long-term severe obstruction, bladder imaging can reveal vesicoureteral reflux and bladder trabeculation. Excretory bladder urethrography often shows elongation and dilation of the posterior urethra and elevation of the bladder neck; excretory urography can display hydroureter and hydronephrosis.

Ultrasound examination: In children with severe azotemia, ultrasound can reveal hydroureter, hydronephrosis, and bladder enlargement. In a fetus at 28 weeks of pregnancy, the presence of hydroureter, hydronephrosis, and bladder enlargement is a typical sign of posterior urethral valves.

Instrumental examination: Under general anesthesia, urethroscopy and cystoscopy can reveal bladder trabeculation and cell formation, and in some cases, diverticula, as well as thickening of the bladder neck and trigone. The valves can be directly visualized in the distal prostatic urethra to confirm the diagnosis. Compression of the bladder suprapubically can further demonstrate the relationship between the valves and the obstruction.

bubble_chart Treatment Measures

The primary goal of treatment is to remove the valve membrane, and the choice of surgical method and approach depends on the degree of obstruction and the child's health condition. For grade I and grade II obstruction with mild azotemia, transurethral electrocoagulation of the valve membrane can be selected, with satisfactory results. In a few patients, the valve membrane can be destroyed and the urethra dilated by inserting a catheter, cystoscope, or urethral probe through a perineal incision.

For children with severe obstruction causing varying degrees of hydronephrosis, urinary sepsis, and azotemia, antibiotics, indwelling catheters, and correction of electrolyte imbalances should be administered. Children with vesicoureteral reflux and renal dysplasia should undergo vesicostomy.

In most children with severe hydronephrosis, due to ureteral dilation and relaxation, and hypertrophy of the bladder trigone, leading to obstruction at the ureterovesical junction, simple vesicostomy and valve membrane resection are not satisfactory. For these patients, ureterocutaneostomy is necessary to protect renal function and reduce or eliminate hydronephrosis. After the hydronephrosis improves, valve membrane resection and ureteral reconstruction can be performed.

The duration of urinary diversion should be as short as possible, as prolonged bladder and upper urinary tract diversion can cause permanent bladder contracture. Johnston (1979) reported that about 50% of children with urethral valve membranes have vesicoureteral reflux, and bilateral reflux often has a poor prognosis. After the obstruction is relieved, reflux can disappear naturally in one-third of patients, while the remaining two-thirds require surgical treatment.

After the obstruction is relieved, antibiotics should be used to prevent the recurrence of urinary sepsis and urinary tract infections.

bubble_chart Prognosis

The best way to protect kidney and bladder function is early detection. Prenatal ultrasound should be performed, and newborns should undergo thorough physical examinations, observation of urination, and urine tests. Children with azotemia and prolonged urinary tract infections, even after the obstruction is relieved, have a poor prognosis.