Congenital abnormalities of the Kidney or mal-developed kidneys

It is an abnormality in complex process of development of the kidney in the fetus leads several defects in the kidney. Kidney defects commonly seen are in position, rotation, number and structure of the kidney.

Kidneys develop from lower end of mesonephric duct in the womb (embryo). A bud develops from this mesonephric duct and grows backwards and below. The stalk of the bud forms ureter and it’s dilated upper end the pelvis of the kidney. This primitive pelvis divides repeatedly to from the renal collecting system including glomerulus. This bud can get duplicated during development process leading to congenital anomalies. Kidneys are initially formed in the lower part of the abdomen called pelvis and later they move up to their final position in the upper part of the abdomen just below the diaphragm. Primitive kidney is formed between fifth and eighth week. Improper stimulus during this complex development process will lead to abnormalities, which are called congenital abnormalities (by birth).

Common types of congenital anomalies are

Absence of one kidney

Ectopic kidney

Horse-shoe kidney

Unilateral fusion of kidney

Solitary cystic kidney

Polycystic kidney

Absence of single kidney is a very rare entity and is seen in 1:1400 births.

Ectopic kidney is due to failure of ascent of kidney. As a rule this affects only one side and the opposite side is normal. Left side is more commonly affected and the kidney commonly is seen in the lower abdomen way below its normal position.

Horse-shoe kidney is fusion of the both right and left kidneys usually in the lower part across the midline. The terminology horse-shoe is due to the fact of similar resemblance of the kidney.

Unilateral fusion is very rare, in which both kidneys are situated on one side.

Congenital cystic kidneys (Unilateral and Polycystic) are due to maldevelopment of the kidney parenchyma and collecting ducts draining urine. Urine accumulates and forms these cysts destroying kidney parenchyma.



Absent kidney though poses a severe psychological blow does not cause any problems to urinary excretion. Single kidney is adequate to perform all bodily functions of filtering blood of impurities. Little extra care is necessary in these individuals to prevent urinary tract infections that are harmful to the functioning of the kidney. They may also require periodic tests to rule out infection. Normal healthy life as good as a person having two kidneys can be achieved by these individuals.

Renal ectopia occurs 1:1000 births and left is more commonly affected than the right. Usually these kidneys are undetected unless they develop some disease and are accidentally discovered. Good quality of life can be achieved even though the kidney is in abnormal position. Occasionally due to disease they may present




Urinary difficulty

Fever and infection

Blood in urine – hematuria


Most of these cases are managed symptomatically except in select cases where surgical intervention may be required.

Horse-shoe kidney develops due to fusion of the lower end of the buds forming the kidney in the embryo (womb). It is found in 1:1000 births and fusion occurs in the first 2 months of intrauterine life. Commonly lower poles are fused but very rarely upper poles are also fused. Both the poles are never fused together.

Common problem associated with these kidneys is the urinary outlet (ureters) which gets angulated and compressed due to fusion and there is inadequate urinary flow. This causes pain, stone formation and infection in the kidneys.

Unilateral fusion is rare and both kidneys are found on the same side. Fusion usually occurs with one kidney in one direction and the opposite kidney facing the opposite direction.

All types of congenital cystic kidneys are enormously enlarged kidneys with improper function. Other organs like Lungs and pancreas are also affected with similar cysts. They are associated with



Blood in urine


Increased blood pressure

Kidney failure



Diagnosis is usually not possible by simple clinical examination. Additional tests like Intravenous pyelogram, ultrasound, CT scan are required only to ascertain the exact position of both the kidneys and their function.

Decisions on treatment are only done after carefully considering the function and the likely complications.

Your urologist will be able to advise you on further management.


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