With pronounced malformations of the kidneys, the fetus is not viable and dies in the early stages of pregnancy, while the fetus with milder abnormalities usually survives. About 10% of children are born with potentially serious anomalies of the genitourinary system.
Development of the kidneys
Intrauterine kidney development is an extremely complex process. Primitive night (metanephrosis) is laid on each side of the pelvic region. Then, with the further growth of the lower part of the fetus, each of them begins its movement upwards to the place of its final localization (migration) while simultaneously turning around its axis (rotation). An important impetus for the further development of primitive kidneys is their fusion with the rudiments of the ureters. Migration or rotation disorders are at the heart of the most common kidney anomalies. In addition, in the process of intrauterine development, it is possible to merge both primitive kidneys with the formation of one large kidney.
Kidney anomalies
Kidney anomalies are characterized by three main parameters:
• Lesion can affect one or both kidneys.
• Several anomalies can be combined in one kidney.
• Some anomalies are asymptomatic, but the effects of adverse factors, such as infection, contribute to the detection of malformation. In the case of severe anomalies, renal failure may develop immediately or soon after the birth of the child.
Anomalies of the kidney position are not subject to correction. These include:
• Pelvic kidney remaining in the pelvic area. It is formed as a result of violation of migration in the process of intrauterine development. Most of these anomalies are asymptomatic.
• Kidney damage. Perhaps in different versions, the most common is the horseshoe-shaped kidney. The migration process is usually not broken.
• The "caked" kidney in the form of a formless, clumpy mass located in the pelvic region. It is formed during the adhesion of the kidneys and the violation of migration. Such a kidney rarely causes pathological symptoms.
• Cross dystopia of the kidney. One kidney is located on the opposite side, next to another kidney.
• Thoracic kidney. Located in the chest cavity, which can be associated with a violation of the development of the diaphragm (fibrous-muscular septum separating the thoracic and abdominal cavities). This is a very rare anomaly, surgical correction of which is extremely difficult.
• Aging (congenital absence) of the kidney. It is observed, if the embryo did not place a rudiment, from which the urogenital organs should develop. Bilateral renal agenesis leads to the death of the embryo.
The ureter is a muscle tube through which the urine from the kidneys flows into the bladder. In the early stages of development, a number of anomalies are possible, which often lead to a disruption in the passage of urine. Disturbance of the fusion of the ureteric primordia (primitive renal drainage system) with mesonephros (primitive embryonic kidney) leads to the arrest of further development of the kidney (aplasia). In other cases, underdevelopment of the kidney is observed with the formation of the cystic structure (dysplasia) of Aplasia and renal dysplasia often
Separation of ureters
The ureteric ovula can bifurcate and give rise to several blindly terminating ducts that are directed down along the ureter. Sometimes it is possible to infect these outgrowths with the development of pain syndrome. Another variant of the anomaly occurs when the buds of two ureteral processes grow into the embryo - in this case, a doubling of the kidney occurs. Each of them has its own ureter, which empties into the bladder on its own or merges with another. Doubling the drainage system of the kidney is often accompanied by pain due to the casting of urine from the underlying into the overlying part of the kidney.
Defect of the urethral septum
As a result of the pathology of the development of the urethral septum (between the rudiments of the genital organs and the rectum), sometimes there is a cystic enlargement of the ureter's section that swells into the lumen of the bladder-the ureterocele. A small degree of ureterocele occurs quite often and usually does not cause problems. Significant expansion can become a place of formation of urinary stones. A sharp narrowing of the ureteral orifice leads to obstruction. Often ureterocele, urine reflux, and kidney doubling are combined in one patient. To frequent congenital defects of the lower parts of the urinary tract are:
• the posterior urethral valves - the formation of two folds of the mucous membrane of the urethra of the urethra, which leads to a violation of urination;
• hypospadias - incomplete development of the urethra, in which its external opening is on the lower surface of the penis or even on the scrotum, instead of opening on the head of the penis.
Rare anomalies
• Exstrophy of the bladder - defect of the anterior wall of the bladder and abdominal wall below the navel. In this case, deformity of the penis, undescension of the testicles in the scrotum and inguinal hernia, and in girls - cleavage of the clitoris are also observed.
• Cloaca exgrophy is a severe defect in which there is separation of the bladder into two halves (in each of which the ureter enters) and underdevelopment of the penis. It is possible to involve the small intestine and anus, as well as the combination of anomalies with congenital cerebrospinal hernia.
• Epispadia - defect of the upper wall of the urethra. When combined with a sphincter of the bladder, the patient may suffer from urinary incontinence. Early diagnosis and surgical correction of defects are of paramount importance in patients with congenital anomalies of the kidneys and bladder. Operations are carried out in large specialized centers with extensive experience in the treatment of malformations of the urogenital system in children. In the skilled hands, most of the abnormalities of the bladder can be successfully corrected.