Kidney agenesis is a malformation of the urinary system, consisting in the congenital absence of one or two kidneys. Isolated unilateral anomaly is asymptomatic, sometimes accompanied by secondary arterial hypertension. With bilateral agenesis, anuria develops, the newborn dies in utero or shortly after birth. The anomaly is diagnosed according to prenatal ultrasound of the fetus, ultrasound of the kidneys in a newborn, excretory urography, MRI. Asymptomatic agenesis does not require treatment. With the development of insufficiency of a single kidney, nephrotransplantation is indicated.
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Kidney agenesis (arenia) refers to congenital quantitative abnormalities of the organ, along with a doubled and an additional kidney. Bilateral arenia occurs with a frequency of 1:3000-4000, unilateral – 1:1500 births, in most cases the absence of the left kidney is noted. Kidney agenesis is twice as often diagnosed in boys. Renal abnormality may be combined with agenesis of other urinary organs and genitals.
Causes of kidney agenesis
Kidney agenesis in modern nephrology is regarded as a multifactorial problem caused by both genetic defects and environmental influences. Quite often, arenia is an inherited pathology. In almost half of cases, renal agenesis reveals mutations in the RET and GDNF genes, which play a key role in the induction of nephrogenesis.
Bilateral aplasia/agenesis usually occurs if at least one of the parents has some kind of kidney malformation or one kidney is missing from birth. Unilateral agenesis can be both hereditary and sporadic, caused by the effects of pathogenic factors on the body of the pregnant woman and fetus during the embryonic period. Such adverse events can be:
- infectious diseases of the mother (rubella, etc.);
- early pregnancy;
- pregnant woman’s contact with harmful chemicals (taking pharmacopreparations, working with alkali);
- the presence of insulin-dependent diabetes mellitus in a pregnant woman;
- drug use (cocaine addiction), alcohol.
Kidney agenesis can be a component of the syndromes of multiple malformations: Potter, Rokitansky-Kustner, Turner, Ivemark, Di Giorgi, caudal regression, and many others. Arenia is often combined with other defects of the genitourinary organs: the absence of the adrenal gland, ureter, bladder, in boys – with agenesis of the vas deferens, seminal tubercle and prostate, in girls – with aplasia of the vagina and uterus, a two-horned uterus.
The laying of the kidneys occurs through the interaction between the mesonephral duct, from which the future ureter, renal pelvis and the system of collecting tubules are formed, and the nephrogenic rudiment (metanephric blastema / mesenchyma), giving rise to the nephron. The process of nephrogenesis takes place in the early period of embryo development, up to 6-7 weeks of embryogenesis.
During this period, under the influence of external factors or mutations of the genes responsible for this process, the embryo of the ureter either does not develop at all from the mesonephral duct, or does not stimulate the surrounding metanephric mesenchyma to form glomeruli and nephrons. Agenesis (one- or two-sided) or rudimentary non-functioning kidney (aplasia) is formed.
Without both kidneys, the fetus does not produce urine, which is normally excreted into the amniotic fluid. With aplasia of both kidneys, the volume of amniotic fluid decreases significantly, which leads to severe renal water scarcity, fetal compression. Under these conditions, various deformations are formed, intrauterine death may occur. Patients with unilateral arenia have an increased risk of developing CRF caused by a general decrease in the number of nephrons followed by focal glomerulosclerosis.
First of all, it is necessary to distinguish between renal agenesis and aplasia. With agenesis, the organ is completely absent, with aplasia it is grossly underdeveloped and non-functional. Arenia can occur as an isolated anomaly or as a syndromic pathology. Distinguish agenesis:
- one-sided (more often left-sided);
- two-sided (incompatible with life).
Symptoms of kidney agenesis
Unilateral arenia has no clinical manifestations. Since the contralateral kidney undergoes compensatory hypertrophy in this case, it is palpated through the anterior abdominal wall and may be mistaken for a tumor. Dystopia and malrotation of a single kidney are possible. The danger arises with the development of pathological processes in a single kidney, leading to its functional insufficiency.
Bilateral agenesis refers to lethal defects. About 50% of children with arenia are born prematurely as a result of premature birth, stillbirths are frequent. Live-born children die in the first day or weeks after birth. A characteristic clinical sign of the defect is anuria.
Bilateral agenesis is most pronounced in Potter syndrome. Children with this pathology have the following facial anomalies: a puffy face with a protruding forehead, a wide bridge of the nose, deformity of the ears, hypertelorism, epicanthus, micrognathia. The consequence of oligohydramnion and intrauterine compression of the fetus are hypoplasia of the lungs and deformities of the limbs (clubfoot, arthrogryposis, congenital dislocation of the hip). The newborn’s skin is wrinkled, flabby, with many folds, the size of the abdomen is enlarged.
Children born with a single functioning kidney have a high probability of developing arterial hypertension (AH) and renal failure. Secondary hypertension by the age of 18 is formed in about 50% of children with unilateral agenesis. A third of patients have CRF by the age of 30-40, some of them need hemodialysis at a young age. There is also an increased risk of kidney infections, nephrolithiasis.
With bilateral agenesis, most of the deaths after birth are caused by hypoplasia of the lungs and respiratory failure. Also, the death of a child can be caused by other severe defects: CHD, spina bifida, myelomeningocele, etc.
Diagnostics of kidney agenesis
The wide availability of prenatal ultrasound screening makes it possible to detect kidney agenesis in utero. Ultrasound diagnosis criteria are:
- With unilateral agenesis: absence of kidney and renal artery on the one hand, compensatory hypertrophy of the opposite kidney.
- With bilateral arenia: oligohydramnion after 17 weeks, the bladder is not visualized, or there is no urine in the bladder.
Invasive prenatal testing (amniocentesis) or postpartum karyotyping is indicated to exclude chromosomal aberrations. Also, in the postpartum period, the following help to confirm kidney agenesis in a newborn:
- Sonography. Unilateral anomaly is usually diagnosed in adulthood during ultrasound of the retroperitoneal space. If an anomaly is suspected, the echography of the kidneys is necessarily supplemented with color Dopplerography, ultrasound of the bladder and pelvic organs.
- X-ray techniques. Excretory urography is used to determine the number of kidneys, their localization, and structure. Often, with agenesis, the corresponding ureter and the Lieto triangle are also missing, sometimes the mouth and the lower third of the ureter remain intact. A more accurate picture is given by renal angiography, CT / MRI of the retroperitoneal space, nephroscintigraphy.
- Endoscopic diagnostics. Chromocystoscopy gives a direct idea of the number of ureters and functioning kidneys. However, in the case of doubling of the ureters of a single kidney, a false impression may be created about the absence of an anomaly.
- Nephrological complex. The study of the general analysis of urine, electrolytes, creatinine and blood urea helps to assess and track the dynamics of renal function.
During prenatal and postnatal diagnostics, it is necessary to conduct a thorough differential diagnosis of aplasia-agenesis and other renal abnormalities:
- pelvic dystopia;
- severe hypoplasia;
- kidney atrophy;
- multicystic organ dysplasia;
- conditions after nephrectomy.
Treatment of kidney agenesis
With unilateral agenesis without clinical manifestations, no special treatment is required. Lifelong monitoring of the functions of a single kidney is necessary. Treatment is indicated only if complications occur:
- With pyelonephritis. Bed rest, salt-free and low-protein diet are prescribed. Antibacterial therapy with protected penicillins, 3rd generation cephalosporins, fluoroquinolones, aminoglycosides is carried out. Treatment is supplemented with infusion therapy, extracorporeal detoxification methods (plasmapheresis, hemosorption).
- With nephrolithiasis. With stones of a single kidney, preference is given to endoscopic methods of removing concretions: percutaneous nephrolithotripsy, laser nephrolithotripsy. They cause less surgical trauma and are associated with a lower risk of organ dysfunction. Less often, remote lithotripsy, laparoscopic interventions are used.
- With renal insufficiency. In case of a critical decrease in the patient’s indicators, he is transferred to hemodialysis. In the terminal stage of CPN, nephrotransplantation is performed.
Prenatal detection of bilateral arenia at up to 22 weeks is considered a medical basis for early termination of gestation. When refusing a medical abortion, conservative obstetric tactics are carried out. There are cases when infants with the absence of both kidneys survived: they needed chronic peritoneal dialysis until the moment when kidney transplantation was possible.
Prognosis and prevention
Bilateral arenia is fatal, patients with unilateral agenesis may have a sufficient life expectancy, provided the normal functioning of a single kidney. Bilateral agenesis leads to death in utero or in infancy. It is believed that for sporadic cases of renal agenesis-aplasia, there is a 3% risk of recurrence of the defect in repeated pregnancies.
Prevention of anomalies in the number of kidneys is to exclude teratogenic factors in the early stages of gestation. If there are cases of children with kidney agenesis in the family, it is recommended to resort to genetic counseling when planning the next pregnancies. Persons who have one kidney from birth should avoid hypothermia, infections, injuries or organ damage.