Congenital anomaly is a condition that is present at the time of birth.
The kidneys are situated near the lower back on each side of the spine. They have a complex filtering system by which they absorb nutrients from the blood and pass out the liquid waste through the ureter (tube connecting the kidney to the urinary bladder), urinary bladder and urethra as urine. In the embryonic stage (5 weeks into pregnancy), many abnormalities can occur in the kidneys and ureters, hence they are called congenital abnormalities.
Types of congenital abnormalities of kidneys
- Absence of one kidney: Also called agenesis when there is absence of one kidney the corresponding ureter is also absent. In this case the single kidney increases to almost twice its normal size and takes over the function of two kidneys.
- Supernumary kidney: There may be more than one kidney on one or both sides.
- Hypoplasia: When a kidney attains a smaller size than normal or functions less it is called hypoplasia.
- Dysplasia: When a certain part of the kidney forms abnormal tissues it is called dysplasia.
- Fused kidney: About 1 in every 1000 individuals has some form of fused kidneys. The commonest example is the horse shoe shaped kidney where the lower ends of the kidneys are fused similar to a horse shoe. Another example is S shaped kidney.
- Congenital hydronephrosis: It is usually bilateral and the kidneys become enlarged due to some obstruction like folds or valves in the urethra. In hydroneohrosis the renal tissue is damaged and the kidney functions may deteriorate.
- Ectopic kidney: When the kidney is not located at its correct place it is said to be an ectopic kidney. The left kidney is more frequently ectopic than the right.
- Pelvic kidney: Here one of the kidneys fails to ascend to its normal position and remains in the pelvis. The other kidney is usually normally positioned.
- Rotated kidney: The kidney is rotated on the vertical axis
- S shaped kidney: Both kidneys are on one side and fuse end to end making an S shape.
- Aberrant blood vessels: Sometimes along with the main artery supplying the kidney (renal artery) there is an extra artery called aberrant renal artery which is small. Sometimes this artery becomes large and is associated with hydronephrosis(swelling of kidneys).
- Cysts in the kidney: Solitary renal cyst, unilateral multicystic kidney, sponge kidney and polycystic kidney are some of the important cystic deformities.
- Polycystic kidneys are hereditary and often seen on both sides. The kidneys are large and an abdominal lump is found when the foetus is examined.
- Sponge kidney is asymptomatic unless there is infection or stone formation.
- Unilateral multicystic kidney is felt as an irregular mass in the region of kidney.
- Solitary renal cyst: This condition is asymptomatic or it can lead to symptoms like dull pain in the back, abdominal swelling and indigestion.
- Renal arteriovenous fistula: In this condition there is a mixing of blood between the artery and vein leading to a swelling of the vessel walls called fistula.
- Disorders of the renal tubules: Cystinuria, vitamin D resistant rickets, and renal tubular acidosis are some of the important disorders of functions of the renal tubules.
Congenital malformations of the ureter
- Absence of one ureter: This is associated with absence of kidney on the same side.
- Congenital megaureter: In this case the wall of the ureter expands and is thick. It is seen more often in males and is asymptomatic.
- Stenosis or narrowing of the ureter: There may be folds or valves in the ureter which can obstruct the flow of urine.
- Ureterocele: This is a cystic enlargement of one part of the ureter, more common in females and causes urinary obstruction.
- Ectopic ureteric orifice: In rare cases, the ureter opens into an abnormal spot in the urinary tract. In females it is associated with chronic urinary incontinence while in males treatment is not necessary as long as the kidneys are not damaged.
Written by Dr Nisreen Nakhoda, General Physician
Photograph by Urijamjari via Creative Commons
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