Renal fusion is a congenital disorder of the relationship of the excretory organs, characterized by the fusion of both kidneys into one. It may be accompanied by pain syndrome, symptoms of compression of the inferior vena cava, secondary renal complications (hydronephrosis, chronic pyelonephritis, nephrolithiasis, nephrogenic hypertension). Diagnosis is based on the results of ultrasound, intravenous urography, pyelography, angiography, scintigraphy, CT, MRI. Treatment may include isthmotomy (dissection of the isthmus), nephrectomy, elimination of concomitant complications.
Meaning
Renal fusion is considered in modern urology as an anomaly of the mutual arrangement of organs, in which both kidneys merge into one, but each has its own vessels and ureters, located in their usual places and opening into the bladder. It accounts for about 14% of all malformations of these organs. It is more common in males and in half of cases is accompanied by kidney dystopia and other anomalies of the location of internal organs.
Causes
Renal fusion is a consequence of abnormal fusion of paired metanephrogenic blastemes in the early stages of embryogenesis, approximately 8-10 weeks of intrauterine development. As a result of fusion, the processes of embryophetal migration of the kidneys to the area of their anatomical bed in the lumbar region and their rotation are disrupted. Therefore, fused kidneys are always dystopian to one degree or another.
At the same time, the ingrowth of the metanephral ducts and the differentiation of metanephrogenic tissue into the kidney proceeds without deviations, therefore, the ureters of the fused kidneys open into the bladder in a typical place, and the histological structure of the organs is not disturbed. The causes leading to renal fusion, as a rule, are adverse teratogenic effects (chemical, infectious, medicinal, fetal injuries and bruises, etc.).
Classification
Anatomical varieties of renal fusion can be very diverse. Among the variants of pathology, symmetrical ones are distinguished, in which each kidney is located homolateral, and asymmetric ones – with a heterolateral location of one of the kidneys. With symmetrical fusion, the kidneys can merge with their upper or lower poles (horseshoe kidney) or median surfaces (biscuit-shaped or lump-shaped kidney).
Variants of asymmetric fusion include the fusion of opposite poles (the upper of one kidney with the lower of the other) in vertically arranged kidneys (S-shaped) or horizontally rotated kidneys (L-shaped). When the longitudinal axes of the kidneys joined by opposite poles coincide, they speak of an I-shaped kidney. I- and S-shaped anomalies are attributed to unilateral fusion, other types – to bilateral fusion. The most common variant is a horseshoe–shaped kidney, a rare one is a biscuit-shaped kidney.
Symptoms
Topographic features determine specific clinical manifestations and concomitant complications of pathology. Asymmetric types of renal fusion due to compression of neighboring organs are characterized by pain in the lower back and hypochondria, gastralgia. Against this background, dyspeptic phenomena develop (nausea, vomiting, flatulence, constipation), neurological symptoms (asthenization, neurasthenia, hysteria).
As a rule, fused kidneys are palpated in the form of a tumor formation along the median line or laterally to the vertebral column. When squeezing vascular trunks, numbness in the lower extremities, lymphostasis, venous congestion and swelling of the lower half of the trunk may occur.
Complications
Disease contributes to the development of various kinds of pathological processes in them – pyelonephritis, hydronephrosis, nephrolithiasis (kidney stones). Against the background of this malformation, nephrogenic arterial hypertension, tumors, including kidney cancer, renal failure often occur. The peculiar location and immobility of the fused kidneys presents a potential danger of injury to the abnormal organ.
Diagnostics
Renal fusion can be recognized during deep palpation of the abdomen or bimanual gynecological examination in women. For a more detailed determination of the type of anomaly, ultrasound and ultrasound of the kidneys, intravenous urography, retrograde pyelography, nephroscintigraphy, renal arteriography, MRI or CT of the kidneys are used. With renal echography, you can directly consider the shape, location, size of the kidneys and their relationship with other organs.
Radiopaque studies, in addition to the variant of renal fusion, allow to identify the presence of hydronephrotic transformation of the organ, tumors, vascular pathology, kidney stones. If surgical treatment is necessary, it is extremely important to study the vascularization of abnormally located organs using ultrasound and renal angiography. To exclude urinary infections, a urine test is shown – a general analysis, bacteriological inoculation for flora and sensitivity to antibiotics.
Treatment
If the fused kidneys function normally, no special treatment of the defect is required. Patients with asymptomatic renal fusion are shown to be monitored by a nephrologist with periodic control ultrasound of the kidneys and urine tests. In case of recurrent infections of the upper urinary tract, courses of conservative therapy of pyelonephritis are conducted.
The detection of stones in the fused kidneys serves as the basis for drug treatment, and if the latter is ineffective, surgical removal of kidney stones: remote or percutaneous lithotripsy, pyelolithotomy, nephrolithotomy. In case of severe abdominal pain, surgical dissection of the abnormal formation, dilution of the kidneys and their fixation (nephropexy) in a physiological position is performed.
In case of damage or loss of function of one of the fused kidneys, partial or total nephrectomy is indicated. Operations on the kidneys during their fusion are technically time-consuming, since the blood supply to abnormal organs is characterized by the complexity of vascular architectonics.