Malformations of the kidney occur relatively often, in between 3 to 4% of all births. The most common are mentioned below.
Absent kidneys (bilateral renal agenesis)
This is rarely seen, (1 in 10,000) and is three times more common in the male than in the female. Forty per cent of these children are stillborn from the resulting renal insufficiency and until now, none have survived longer than 6 weeks.
Absence of one kidney (unilateral renal agenesis)
This anomaly is seen more commonly, (between 1 in 500 to 1,000 births) and is nearly twice as common in males as in females. Usually this condition is discovered by chance with ultrasound before birth but is of little clinical significance in the absence of other abnormalities. Normal life expectancy is normal.
Underdeveloped kidney (renal hypoplasia)
This abnormality is seen in approximately 1 in 1000 births with a kidney weighing less then 50 g (normal approximately 130 g). This leads to compensatory increase in size of the opposite kidney. This situation is usually of no clinical significance. However, if the condition is bilateral or function of the opposite kidney is disturbed, hypertension may develop. In which case the hypoplastic kidney is usually removed.
This is usually seen as a double kidney on one side and occurs in less than 1% of births. This usually is without symptoms or negative consequences. The two ureters either unite or enter the bladder separately. No treatment is necessary.
Floating kidney (nephroptosis)
This condition is thought to be due to connective tissue insufficiency and may occasionally present with abdominal pain on standing which is improved by lying down. Therapy is almost always conservative (weight reduction). If this fails, the kidney may be fixed surgically to the diaphram.
Simple renal cyst
This is the most common renal anomaly and is found in approximately 50% of people over 50 years of age. One distinguishes between those within the renal tissue itself intra- and those on the renal surface extraparenchymal cysts. They are filled with yellowish fluid. The majority (70%) are asymptomatic, but occasionally patients may present with dull flank pain or colic through displacement and obstruction of the collecting system. Usually no therapy is needed, but if the cysts becomes symptomatic with severe pain due to compression or obstruction, they must be surgically resected. This maybe performed by open surgery or laparascopically. Puncture and drainage alone usually results in relapse.
Multi cystic renal dysplasia
This condition is usually not inherited. Characteristically one sees multiple cysts of different sizes as a chance finding by ultrasound. These patients have no symptoms although occasionally development may be slowed and very occasionally malignant transformation may be seen in which case the kidney should be removed.
Polycystic renal dysplasia (autosomal recessive inheritance)
This condition is uncommon, seen in approximately 1 in 40,000 births. It is often detected prior to birth by ultrasound. At birth it often presents as bilateral upper abdominal tumors. The majority of these children develop progressive renal failure immediately or during the first few months after birth. The prognoses is very poor and death usually occurs within months.
Polycystic renal dysplasia ( dominant inheritance)
This condition is more common, with an incidence between 1 in 400 to 1 in 1,000 births. If one parent is affected then the likelyhood of their children being affected is 50%. This condition usually first manifests itself in adult life, rarely before the age of 30. It is often associated with multiple cysts in the liver, spleen, pancreas and lungs and may lead to palpable organ enlargement. Up to 1/3 of the patients suffer with dull abdominal pain due to organ displacement, 50% develop high blood pressure. Other symptoms include blood in the urine, renal stones or symptomatic urinary infection, each in about 20% of cases. Cerebral aneurysms (dilated arteries in the base of the brain) are not uncommonly seen in these patients and approximately 10% of all patients die of bleeding from these blood vessels. Approximately a quarter of patients are dialysis dependent at age 50 and half of them at age 70 . Operative intervention is only indicated for painful displacement symptoms or repeated bleeding. Upon occasion renal transplantation should be considered.
This condition is seen in 1: 10 000 births, (75% being bilateral) and is not hereditary. It is distinguished by dilated collecting ducts and the presence of small cysts within the kidney. The process takes place only in the inner part of the kidney (renal medulla and gives a sponge like appearance on X-ray. Approximately 50% of patients never experience any symptoms. 30 to 50 % have increased calcium in the urine which may result in recurrent kidney stones. About half of the patients with medullarysponge kidney suffer with renal colic, half of them with documented passage of stones. Other primary symptoms are therapy resistant urinary infection or blood in the urine. Patients with clinically manifested stones are treated with lithotrypsy (shockway therapy). Larger stones or multiple stones may require surgical removal. To reduce the risk of recurrent renal stones, patients should drink a minimum of 2.5 liters of fluid per day.