Posterior urethral valve (PUV) disorder is an obstructive developmental anomaly in the

urethra The urethra (: urethras or urethrae) is the tube that connects the urinary bladder to the urinary meatus, through which Placentalia, placental mammals Urination, urinate and Ejaculation, ejaculate. The external urethral sphincter is a striated ...

and genitourinary system of male newborns. A posterior urethral valve is an obstructing membrane in the posterior male urethra as a result of abnormal '' in utero'' development. It is the most common cause of bladder outlet obstruction in male newborns. The disorder varies in degree, with mild cases presenting late due to milder symptoms. More severe cases can have

renal In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and right in the retrop ...

and

respiratory failure Respiratory failure results from inadequate gas exchange by the respiratory system, meaning that the arterial oxygen, carbon dioxide, or both cannot be kept at normal levels. A drop in the oxygen carried in the blood is known as hypoxemia; a r ...

from lung underdevelopment as result of low amniotic fluid volumes, requiring

intensive care Intensive care medicine, usually called critical care medicine, is a medical specialty that deals with seriously or critically ill patients who have, are at risk of, or are recovering from conditions that may be life-threatening. It includes p ...

and close monitoring. It occurs in about one in 8,000 babies.

Presentation

PUV can be diagnosed before birth, or even at birth when the ultrasound shows that the male baby has a hydronephrosis. Some babies may also have oligohydramnios due to the urinary obstruction. The later presentation can be a urinary tract infection, diurnal enuresis, or voiding pain.

Complications

* Incontinence *

Urinary tract infection A urinary tract infection (UTI) is an infection that affects a part of the urinary tract. Lower urinary tract infections may involve the bladder (cystitis) or urethra (urethritis) while upper urinary tract infections affect the kidney (pyel ...

Renal failure Kidney failure, also known as renal failure or end-stage renal disease (ESRD), is a medical condition in which the kidneys can no longer adequately filter waste products from the blood, functioning at less than 15% of normal levels. Kidney fa ...

Vesicoureteral reflux Vesicoureteral reflux (VUR), also known as vesicoureteric reflux, is a condition in which urine flows retrograde, or backward, from the urinary bladder, bladder into one or both ureters and then to the renal calyx or kidneys. Urine normally trave ...

Chronic kidney disease Chronic kidney disease (CKD) is a type of long-term kidney disease, defined by the sustained presence of abnormal kidney function and/or abnormal kidney structure. To meet criteria for CKD, the abnormalities must be present for at least three mo ...

Oligohydramnios Oligohydramnios is a medical condition in pregnancy characterized by a deficiency of amniotic fluid, the fluid that surrounds the fetus in the abdomen, in the amniotic sac. The limiting case is anhydramnios, where there is a complete absence of ...

Diagnosis

Abdominal

ultrasound Ultrasound is sound with frequency, frequencies greater than 20 Hertz, kilohertz. This frequency is the approximate upper audible hearing range, limit of human hearing in healthy young adults. The physical principles of acoustic waves apply ...

is of some benefit, but not diagnostic. Features that suggest posterior urethral valves are bilateral hydronephrosis, a thickened bladder wall with thickened

smooth muscle Smooth muscle is one of the three major types of vertebrate muscle tissue, the others being skeletal and cardiac muscle. It can also be found in invertebrates and is controlled by the autonomic nervous system. It is non- striated, so-called bec ...

trabeculations, and bladder

diverticula In medicine or biology, a diverticulum is an outpouching of a hollow (or a fluid-filled) structure in the body. Depending upon which layers of the structure are involved, diverticula are described as being either true or false. In medicine, t ...

. Voiding cystourethrogram (VCUG) is more specific for the diagnosis. Normal ''plicae circularis'' are variable in appearance and often not seen on normal VCUGs. PUV on voiding cystourethrogram is characterized by an abrupt tapering of urethral caliber near the verumontanum, with the specific level depending on the developmental variant.

is also seen in over 50% of cases. Very often the posterior urethra maybe dilated thus making the abrupt narrowing more obvious. the bladder wall may show trabeculations or sacculations or even diverticuli. Diagnosis can also be made by

cystoscopy Cystoscopy is endoscopy of the urinary bladder via the urethra. It is carried out with a cystoscope. The urethra is the tube that carries urine from the bladder to the outside of the body. The cystoscope has lenses like a telescope or microscop ...

, where a small camera is inserted into the urethra for direct visualization of the posteriorly positioned valve. A limitation of this technique is that posterior valve tissue is translucent and can be pushed against the wall of the

by inflowing irrigation fluid, making it difficult to visualize. Cystoscopy may also demonstrate the bladder changes. Centers in Europe and Japan have also had excellent results with cystosonography, although it has not been approved for use in the United States yet.

Classification

Posterior urethral obstruction was first classified by H. H. Young in 1919. The '' verumontanum'', or mountain ridge, is a distinctive landmark in the prostatic urethra, important in the systemic division of posterior valve disorders: * Type I - Most common type; due to anterior fusing of the ''plicae colliculi'', mucosal fins extending from the bottom of the verumontanum distally along the prostatic and membranous urethra * Type II - Least common variant; vertical or longitudinal folds between the verumontanum and proximal

prostatic urethra The prostatic urethra, the widest and most dilatable part of the urethra canal, is about 3 cm long. It runs almost vertically through the prostate from its base to its apex, lying nearer its anterior than its posterior surface; the form of ...

and bladder neck * Type III - Less common variant; a disc of tissue distal to verumontanum, also theorized to be a developmental anomaly of congenital urogenital remnants in the bulbar urethra Dewan has suggested that obstruction in the posterior urethra is more appropriately termed congenital obstructions of the posterior urethral membrane (COPUMs), a concept that has come from an in-depth analysis of the historical papers, and evaluation of patients with a prenatal diagnosis that has facilitated video recording of the uninstrumented obstructed urethra. The congenital obstructive lesions in the bulbar urethra, named Type III Valves by Young in 1919, have been

eponymous An eponym is a noun after which or for which someone or something is, or is believed to be, named. Adjectives derived from the word ''eponym'' include ''eponymous'' and ''eponymic''. Eponyms are commonly used for time periods, places, innovati ...

ly referred to as Cobb's collar or Moorman's ring. For each of the COPUM (Posterior Urethra) and Cobb's (Bulbar Urethra) lesions, the degree of obstruction can be variable, consistent with a variable expression of the embryopathy. The now nearly one hundred year old nomenclature of posterior urethral valves was based on limited radiology and primitive endoscopy, thus a change COPUM or Cobb's has been appropriate.

Treatment

If suspected antenatally, a consultation with a paediatric surgeon/ paediatric urologist maybe indicated to evaluate the risk and consider treatment options. The most important first treatment in a newborn baby boy is to relieve the bladder with urethral catheter or suprapubic drainage. Treatment is by endoscopic valve ablation. Fetal surgery is a high risk procedure reserved for cases with severe

oligohydramnios Oligohydramnios is a medical condition in pregnancy characterized by a deficiency of amniotic fluid, the fluid that surrounds the fetus in the abdomen, in the amniotic sac. The limiting case is anhydramnios, where there is a complete absence of ...

, to try to limit the associated lung underdevelopment, or pulmonary hypoplasia, that is seen at birth in these patients. The risks of fetal surgery are significant and include limb entrapment, abdominal injury, and fetal or maternal death. Specific procedures for ''in utero'' intervention include infusions of

amniotic fluid The amniotic fluid is the protective liquid contained by the amniotic sac of a gravid amniote. This fluid serves as a cushion for the growing fetus, but also serves to facilitate the exchange of nutrients, water, and biochemical products betwee ...

, serial bladder aspiration, and creating a connection between the

amniotic sac The amniotic sac, also called the bag of waters or the membranes, is the sac in which the embryo and later fetus develops in amniotes. It is a thin but tough transparent pair of biological membrane, membranes that hold a developing embryo (and l ...

and the fetal bladder, or vesicoamniotic shunt. There are three specific endoscopic treatments of posterior urethral valves: * Vesicostomy followed by valve ablation - a

stoma In botany, a stoma (: stomata, from Greek language, Greek ''στόμα'', "mouth"), also called a stomate (: stomates), is a pore found in the Epidermis (botany), epidermis of leaves, stems, and other organs, that controls the rate of gas exc ...

, or hole, is made in the

urinary bladder The bladder () is a hollow organ in humans and other vertebrates that stores urine from the Kidney (vertebrates), kidneys. In placental mammals, urine enters the bladder via the ureters and exits via the urethra during urination. In humans, the ...

, also known as ''low diversion'', after which the valve is ablated and the stoma is closed. * Pyelostomy followed by valve ablation - stoma is made in the pelvis of the kidney as a slightly ''high diversion'', after which the valve is ablated and the stoma is closed * Primary (transurethral) valve ablation - the valve is removed through the urethra without creation of a stoma The standard treatment is primary (transurethral) ablation of the valves. Urinary diversion is used in selected cases, and its benefit is disputed. Following surgery, the follow-up in patients with posterior urethral valve syndrome is long term, and often requires a multidisciplinary effort between paediatric surgeons/ paediatric urologists, paediatric nephrologists, pulmonologists, neonatologists, radiologists and the family of the patient. Care must be taken to promote proper bladder compliance and renal function, as well as to monitor and treat the significant lung underdevelopment that can accompany the disorder. Definitive treatment may also be indicated for the vesico-ureteral reflux.

Female homolog

The

female An organism's sex is female ( symbol: ♀) if it produces the ovum (egg cell), the type of gamete (sex cell) that fuses with the male gamete (sperm cell) during sexual reproduction. A female has larger gametes than a male. Females and ...

homolog In biology, homology is similarity in anatomical structures or genes between organisms of different taxa due to shared ancestry, ''regardless'' of current functional differences. Evolutionary biology explains homologous structures as retained her ...

to the

male Male (Planet symbols, symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or Egg cell, ovum, in the process of fertilisation. A male organism cannot sexual repro ...

verumontanum from which the valves originate is the

hymen The hymen is a thin piece of mucosal tissue that surrounds or partially covers the vaginal opening. A small percentage of females are born with hymens that are imperforate and completely obstruct the vaginal canal. It forms part of the vulva ...

References

External links

{{Congenital malformations of urinary system Congenital disorders of urinary system Pediatrics