Posterior urethral valve syndrome

　　The etiology of posterior urethral valve syndrome is unclear. Because there is occasionally a family history, some people believe it is due to abnormal development of the mesonephric duct, or it may be the result of multiple factors. Some people also believe it is caused by abnormal development of the urogenital sinus. There are four theories about the formation of posterior urethral valves:

　　1. The proximal and distal ends of the normal glans penis have several mucosal folds. If these mucosal folds become hypertrophic and protrude into the urethra, it forms the first or second type of posterior urethral valve.

　　2. The urogenital membrane during the embryonic period did not completely regress, and the residual urogenital membrane formed the third type of posterior urethral valve.

　　3. Congenital malformations of the mesonephric duct or Müllerian duct.

　　4. The mucosa of the glans penis is adherent and fused with the mucosa of the urethra. There are reports that both identical twin brothers have posterior urethral valves, and it is difficult to determine the relationship with heredity.

　　Posterior urethral valve syndrome causes lower urinary tract obstruction. The main harm caused during fetal development is that the development of the primary renal tissue under high-pressure environment will necessarily lead to abnormal development of the urinary tract, including the structure and function of the bladder, ureteral smooth muscle, and renal parenchyma.

　　Posterior urethral valve is formed by the valve at the distal part of the prostatic urethra. Generally, if a child is sick, he will have varying degrees of obstruction symptoms, often manifested as weak urination, urinary tract infection, and other symptoms. Severe cases can cause urinary retention, even vesicoureteral reflux, leading to renal and ureteral hydrops, causing renal cortex atrophy or cystic change, leading to chronic renal failure. Therefore, the damage of urethral valves to the urinary system is great, and the consequences are serious. Urethral valves may be associated with cryptorchidism, seminal papilla hypertrophy, or renal hypoplasia.

　　Posterior urethral valve syndrome is the most common congenital lower urinary tract obstruction in male children. Its common clinical manifestations include:

　　1, Urinary obstruction:Older children may be found by relatives to have difficulty urinating, requiring abdominal pressure during urination, with symptoms of frequent urination and dribbling, even overflow incontinence, and enuresis symptoms are severe and persistent, but young children cannot express themselves and are easily ignored by relatives.

　　2, Pubic or lumbar mass:This is a common sign. Due to urinary obstruction, bladder urinary retention and secondary renal pelvis dilation occur, and because the abdominal wall and lumbar muscles of children are relatively weak, the full bladder and edematous kidneys are easily palpable. Pain in the lumbar region during urination suggests vesicoureteral reflux.

　　3, Growth and malnutrition:Due to renal dysfunction, the growth and nutrition of children are delayed compared to their actual age, and their height, weight, and intellectual development are all delayed. Anemia and hypoproteinemia are common.

　　4, Renal dysfunction:Renal function tests show decreased concentrating function, and in severe cases, blood BUN and Cr levels increase, with metabolic acidosis and electrolyte imbalance.

　　5, Symptoms of urinary tract infection:High fever, chills, pyuria, and hematuria may occur due to secondary pyelonephritis.

　　6, Other:Some newborns may show respiratory distress syndrome or unexplained pneumothorax or mediastinal emphysema, which is often caused by posterior urethral valve with pulmonary hypoplasia.

　　There is currently no special preventive method for posterior urethral valve syndrome. Active prevention and treatment of urinary tract infections, complications, and treatment to improve prognosis are recommended. Preventive measures can refer to other congenital birth defects, and should be implemented from pre-pregnancy to prenatal care. Pre-marital physical examination mainly includes serological tests such as hepatitis B virus, syphilis, HIV, reproductive system examination such as cervical inflammation screening, general physical examination such as blood pressure, electrocardiogram, and inquiry of family history of diseases and personal medical history.

　　To do genetic counseling work, pregnant women should try to avoid harmful factors, including staying away from smoke, alcohol, drugs, radiation, pesticides, noise, volatile harmful gases, toxic and harmful heavy metals, and other factors. During the process of prenatal care in pregnancy, it is necessary to carry out systematic screening for birth defects, including regular ultrasound examinations, serological screening, and necessary chromosomal examinations. If abnormal results occur, it is necessary to determine whether to terminate the pregnancy.

　　The safety of the fetus in utero, the presence of sequelae after birth, whether it can be treated, the prognosis, and so on. Adopting practical and feasible diagnostic and treatment measures, the fetus with posterior urethral valve first presents with hydronephrosis, characterized by bilateral hydronephrosis of the kidneys and ureters, thickening of the bladder wall, reduced amniotic fluid volume. In the fetus, a reduced volume of amniotic fluid is an important signal of the presence of lower urinary tract obstruction. The issue of performing an in utero bladder catheterization to decompress the fetus with posterior urethral valve is currently highly controversial, as well as the impact on the mother and fetus, the achievable effects, and the occurrence of complications are all under observation.

　　Posterior urethral valve syndrome causes lower urinary tract obstruction. The main harm caused in the fetal stage is that the development of the primary renal tissue under the high-pressure environment of the cavity must lead to abnormal development of the urinary tract, including the structure and function of the bladder, ureteral smooth muscle, and renal parenchyma. The examinations that need to be done for posterior urethral valve syndrome include:

　　Laboratory examination:There are usually azotemia and decreased renal concentrating function. Patients with chronic infection may have anemia and infectious urine. Serum creatinine, blood urea nitrogen, and creatinine clearance are the best indicators reflecting the degree of renal damage.

　　X-ray examination:Excretory cystography is the best method for diagnosing posterior urethral valve syndrome. For patients with a large amount of residual urine, catheterization should be performed before filming, and the urine drained from the catheter should be routinely cultured. In cases of long-term severe obstruction, cystography can detect vesicoureteral reflux and bladder trabecula formation. On the excretory cystography, the elongation and dilation of the posterior urethra and the elevation of the bladder neck are often visible; excretory urography can show hydronephrosis of the ureters and kidneys.

　　Ultrasonic examination:For children with severe azotemia, ultrasonic examination can detect hydronephrosis and bladder enlargement. If hydronephrosis and bladder enlargement are found in a fetus at 28 weeks of gestation, it is a typical sign of posterior urethral valve syndrome.

　　Instrument examination:Under general anesthesia, cystoscopy and cystoscopy can be performed, showing the formation of small trabeculae and small rooms in the bladder, and a few can even be seen diverticula, as well as hypertrophy of the bladder neck and trigone area. The valve can be directly seen at the distal end of the prostatic urethra, and the diagnosis can be made clearly. If the bladder is compressed above the pubic bone, the relationship between the valve and the obstruction can be further displayed.

　　The diet of patients with posterior urethral valve syndrome should be light and easy to digest, with an emphasis on eating more vegetables and fruits, and a reasonable dietary arrangement. Attention should be paid to ensuring sufficient nutrition. In addition, patients should also pay attention to avoiding spicy, greasy, and cold foods.

　　The treatment measures for posterior urethral valve syndrome depend on the condition of renal function and the age of the child. The primary treatment for severe urinary tract obstruction caused by posterior urethral valve syndrome in infants is to correct water and electrolyte imbalance, control infection, and drain through urethral or bladder catheterization. It is as far as possible to protect renal function and maximize the recovery of renal function, and improve the general condition. Generally speaking, catheter drainage for 5 to 7 days can appropriately restore the existing renal function.

　　Due to the application of endoscopy, posterior urethral valve syndrome can be easily diagnosed and treated early. After the improvement of renal function, the bladder valve can be electrocauterized through the urethra or bladder. An 8F endoscope or ureteroscope can be used to observe the urethra and understand the location of the external sphincter. If an endoscope is inserted into the urethra, and water is flushed out from the bladder, the valve can be seen to open outward. The valves at 5 o'clock, 7 o'clock, and 12 o'clock in the middle can be electrocauterized. For those who cannot insert an endoscope through the urethra, an endoscope can be inserted through the bladder ostomy, and the valve can be electrocauterized in a forward direction. The advantage of this method is that the valve can be clearly seen in the dilated urethra, with minimal urethral trauma. If the posterior urethra is excessively elongated and the bladder urethral scope cannot reach the valve site, a flexible bladder urethral scope can be used, or the posterior urethral valve can be excised by Nd-YAG laser through the ureteroscope.

　　For infants with poor general condition, newborns, or premature infants, a bladder ostomy (fixing the anterior wall of the bladder to the abdominal wall and opening a window without stoma) can be performed first to drain urine, and then electrocautery of the bladder valve can be performed after the general condition improves, and it is rarely used to perform ureteral skin ostomy or nephrostomy. Now, it is rarely used to perform open posterior urethral valve resection and urethral dilation for the treatment of posterior urethral valve syndrome.

　　After electrocautery of the bladder valve, close follow-up should be conducted to observe whether the bladder can be emptied and the recovery of renal function, and whether there are recurrent urinary tract infections. Clinically, children generally improve quickly; but the recovery of the bladder is much slower, and the recovery of the dilated ureter is even slower. Some bladder ureteral reflux may be relieved or even disappear. If there is still bladder ureteral reflux, urinary ureteral reimplantation with antireflux action can be performed to make the bladder and ureter have antireflux action. If there is no improvement in renal or ureteral hydrops, and there is still unilateral severe reflux, it should be differentiated whether there is ureteral obstruction, and it can be considered to perform ureteroplasty and ureteral bladder reimplantation. If the kidney is nonfunctional, it may be a severely malformed kidney, and then a nephrectomy on the affected side should be considered. During follow-up, a small number of children still have difficulty urinating after electrocautery of the bladder valve, and then urodynamic examination should be performed, which may be associated with detrusor dysfunction, bladder neck hypertrophy, and decreased bladder capacity, and corresponding drug treatment, intermittent catheterization, or bladder augmentation can be used to improve the symptoms of difficulty urinating.