Horseshoe kidney is a congenital anomaly in which both kidneys fuse together in the area of the lower or upper pole to form an isthmus. Pathology is often complicated by pyelonephritis, urolithiasis, hydronephrosis and other diseases of the urinary system. Ultrasound, urography, pyelography, computed tomography of the kidneys are used. Surgical treatment is indicated for the development of a urological disease in an altered kidney that requires surgical tactics.
ICD 10
Q63.1 Fused, lobed and horseshoe-shaped kidney
Meaning
Horseshoe kidney occurs in modern urology with a frequency of 10-15% of all renal abnormalities, in the ratio of 1 case per 500 newborns, and in boys 2.5 times more often than in girls. The defect is characterized by the fusion of the kidneys in the lower, less often – upper poles, as a result of which the connected kidneys acquire a “U”-shaped appearance resembling a horseshoe. At the same time, each of the kidneys has its own ureter, flowing into the bladder, and feeding vessels. In 88.6%, horseshoe-shaped kidneys have abnormal blood circulation and an unusual structure of the cups.
In some cases, the kidneys are fused together by medial surfaces (the so-called biscuit-shaped kidney), opposite (upper with lower) poles (S or L-shaped kidney), both poles and the median surface (disc-shaped kidney). Pathology can be combined with other congenital malformations – polycystic kidney disease, hydrocephalus, spina bifida, malformations of the anorectal system, skeletal abnormalities (cleft lip and palate, polydactyly, clubfoot).
Causes
The formation of a horseshoe kidney is a consequence of dysembriogenesis. In the fetus, the development of the kidney goes through three successive stages: the kidney (pronephros), the primary kidney (mesonephros) and the secondary kidney. In parallel with the development of the secondary kidney, the paired organ migrates to the area of the future bed in the lumbar region. The final formation and fixation of the kidney ends after birth. The anomaly is formed as a result of violations of the processes of migration and rotation of the kidney caused by diseases of the mother, infections, exposure to harmful chemicals or drugs on the fetus.
Pathanatomy
The horseshoe—shaped kidney, fused with the lower poles, is located below the physiological boundary (XI-XII thoracic – II lumbar vertebrae). The isthmus of the horseshoe kidney can correspond to the level of the IV-V lumbar vertebrae and is usually located anteriorly from the aorta, nerve trunks and inferior vena cava. With sudden movements, the isthmus can put pressure on nerves and blood vessels, causing pain. With abdominal injuries, the risk of damage to the horseshoe kidney increases; in addition, this anomaly predisposes to the occurrence of various kinds of urological diseases in the kidney. Horseshoe kidney is almost always combined with dystopia.
Symptoms
Due to the specifics of topography, innervation and blood supply, the anomaly may be accompanied by a characteristic pain symptom complex: pain in the navel area that occurs when the trunk is bent or extended, in the lower back, lower abdomen, in the epigastrium after physical exertion. Compression of the nerve plexuses of the mesentery root by the isthmus of the kidney can cause constipation, spastic pain in the intestine, violation of intestinal peristalsis.
Against the background of a constant combat syndrome, emotional instability, neurasthenia, hysteria can develop. Venous intrarenal hypertension caused by vascular compression is sometimes accompanied by hematuria. When the inferior vena cava is squeezed, venous congestion develops in the lower half of the body: edema of the lower extremities, varicose veins of the lower extremities and pelvis, ascites. Women may have menstrual irregularities and premature birth. In a number of observations, the horseshoe kidney is not accompanied by any symptoms and is detected by chance.
Complications
Compression of the isthmus of the initial ureter creates an obstacle to the outflow of urine from the pelvis, which leads to the development of:
- pyelonephritis (19.4%)
- the formation of kidney stones (23.6%)
- hydronephrosis (41.7%)
- arterial hypertension (15.2%)
There is evidence that tumor cell transformation and kidney cancer develop more often in the isthmus of the horseshoe kidney.
Diagnostics
The diagnostic examination plan includes ultrasound, ultrasound, intravenous urography or retrograde pyelography, renal arteriography, scintigraphy, computed tomography. Urograms allow us to consider the low location of the organ, limited mobility, layering of the shadows of the lower poles of the kidney on the contour of the vertebral column, the shadow of the isthmus. With retrograde pyelography, a clear silhouette of the horseshoe kidney and its isthmus, a low position of the renal pelvis, and an abnormal location of the cups are visualized in the first minutes.
Ultrasound of the kidneys determines the absence of displacement of the renal contours, the atypical location of the renal pelvis and the altered shape of the cups; with ultrasound, abnormal blood supply to the horseshoe kidney is detected. The performance of nephroscintigraphy records the characteristic accumulation of a radionuclide drug in the form of a horseshoe encircling the vertebral column. Renal angiography is performed to study vascular architectonics, determine the number, localization and presence of additional vessels, thickness and vascularization of the isthmus, which is important when planning surgery.
Treatment
In the absence of clinical manifestations, treatment of a horseshoe kidney is not required. Such patients are subject to the supervision of a urologist to prevent the development of secondary complications. With pyelonephritis, complicating the course of the horseshoe kidney, appropriate course pathogenetic treatment is prescribed. In the case of the development of pain symptoms, hydronephrotic transformation, stone formation, kidney tumors, differentiated surgical tactics are indicated.
In case of pain and urodynamic disorders caused by the pressure of the isthmus, its dissection and dilution of the ends of the kidney with fixation in a new position are performed. With lesions of one of the halves of the horseshoe kidney and loss of its functions, a heminephrectomy is performed. When detecting stones in the horseshoe kidney, various methods of their removal are used, including remote lithotripsy, percutaneous nephrolithotripsy, pyelolithotomy, nephrolithotomy.