Introduction:
Kidney dysplasia, also known as renal dysplasia, or multicystic dysplastic kidney, is a condition characterized by malformed or poorly developed kidneys during fetal development. It can affect one or both kidneys. Renal dysplasia affecting both the kidneys during fetal development would result in stillbirth babies due to poorly functioning kidneys.
Urinary System
The urinary system consists of the kidneys, the ureters, the urinary bladder, and the urethra.
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Kidneys - These are the two bean-shaped organs located in the retroperitoneal region on either side. Their function is to filter the waste products from the blood, maintain electrolyte balance, acid-base balance, etc.
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Ureters - These are the two long thin tubes that carry urine from the kidneys.
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Urinary Bladder - The bladder is a bag-like structure that stores the collected urine from the kidneys through the ureters.
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Urethra - It is a tube that carries urine from the bladder to the outside of the body.
What Are the Types of Kidney Dysplasia?
There are two types of kidney dysplasia:
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Unilateral Renal Dysplasia - When only one kidney is affected or malformed, it is called unilateral renal dysplasia. In most cases, this type does not produce any problems as one kidney is functioning properly, and the children affected by this condition would lead a normal life.
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Bilateral Renal Dysplasia- When both kidneys are malformed, it is called bilateral renal dysplasia. It is a serious defect as both the kidneys fail to function or exhibit poor functioning ability. The babies affected by this condition mostly do not survive birth, or they need aggressive treatment measures to help their survival.
What Is the Epidemiology of Kidney Dysplasia?
Kidney dysplasia is one of the common disorders affecting the kidneys. The incidence rate of renal dysplasia is about one in 4,000 babies. Studies report that the suggested incidence rate is low as most cases of kidney dysplasia are undiagnosed, and in many cases, it occurs in association with other genetic defects. It is found to be more common in males and reported to affect the left kidneys more than the right.
What Is the Etiology of Kidney Dysplasia?
The causes of renal dysplasia include:
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Genetic Factors - Mutations in certain genes can be inherited from the parents to the offspring, thus resulting in the development of renal dysplasia.
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Genetic Syndromes - Certain genetic syndromes which affect the development of multiple organs in the body, including the kidneys, would result in renal dysplasia. Studies report that renal dysplasia in babies presenting with genetic syndromes would have a problem in other systems, including the digestive system, muscular system, nervous system, and cardiovascular system.
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Certain Medications - It is found that the mothers taking certain medications during gestation has a major link with the development of renal dysplasia in the fetus. It includes the medicines used to treat high blood pressure and seizures in pregnant women.
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Cocaine- Pregnant women taking cocaine is also reported to be one of the possible causes of renal dysplasia in the fetus.
What Is the Pathophysiology of Kidney Dysplasia?
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The urinary system develops from the intermediate mesenchyme, and kidney development takes place in three stages. Such as pronephros, metanephros, and mesonephros. The glomeruli develop in the metanephros stage; the ureteric bud arises from the mesonephric duct that divides in a branching fashion to form the renal pelvis, calyces, and collecting ducts. The maturation of the renal tissues takes place in the mesonephric stage.
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It is found that dysplastic kidneys develop due to the abnormal induction of metanephric mesenchyme. This abnormal induction could possibly affect the normal development of the organelles of the kidney and thereby affect its development and function. Few gene mutations are reported to be associated with this defect, such as EYA1 (eyes absent homolog 1), SIX1 (homeobox protein SIX1), and PAX 2 (paired box gene 2), but their exact role and the mechanism in causing this defect is not fully understood.
What Are the Signs And Symptoms of Kidney Dysplasia?
Usually, babies presenting with unilateral kidney dysplasia do not produce any symptoms as the other kidney is functioning well, but the bilateral condition is usually lethal, with few surviving after birth.
Unilateral Renal Dysplasia:
- Frequent urinary tract infections.
- Hypertension (high blood pressure).
Bilateral Renal Dysplasia:
Babies with bilateral renal dysplasia usually show defects in the other organ systems as well. They classically show the signs of potter's syndrome, such as:
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Oligohydramnios (deficiency of amniotic fluid in the womb).
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Pulmonary hypoplasia (a condition characterized by abnormally small lungs with poor function).
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Cranial abnormalities (the abnormal head due to a congenital disability).
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Clubbed feet.
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Anal atresia (a condition characterized by the absence of normal anal opening).
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Absence of esophagus.
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Absence of sigmoid colon, etc.
Babies with bilateral conditions usually die in the womb, or they develop complications such as renal failure, breathing difficulties, etc., which need to be addressed earlier.
What Are the Conditions Associated With Kidney Dysplasia?
The other conditions associated with renal dysplasia include:
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Vesicoureteral Reflux - It is characterized by the abnormal flow of urine from the bladder back into the ureters. When babies with vesicoureteral reflux pass urine in the womb, this backflowing urine can affect kidney function. It is found that around 18 % to 43 % of babies with dysplastic kidneys show vesicoureteral reflux disease.
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Antenatal Hydronephrosis - This is a condition characterized by the dilatation of the upper urinary tract or the enlargement of the kidneys as a result of improperly drained urine. In most cases, dysplastic kidneys are found in association with antenatal hydronephrosis.
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Ureteropelvic Junction Obstruction - It is found that about three percent to 12 % of babies with renal dysplasia show obstruction in the ureteropelvic junction.
How Is Kidney Dysplasia Diagnosed?
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History: Family history is important as it provides information about the genetic link in families and the history of anybody affected in the family with the same disorder. In the case of patients with asymptomatic unilateral renal dysplasia, a history of frequent urinary tract infections would provide a clue in diagnosing the disease.
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Fetal Ultrasound: Fetal ultrasound taken around the 28 th week of gestation would provide a detailed picture of the poorly developed or malformed kidneys. It could be present in one or both kidneys. In the case of babies with other associated genetic syndromes, other findings such as pulmonary hypoplasia, cardiovascular abnormalities, and abnormalities of the digestive tract would also be evident.
How Is Kidney Dysplasia Treated?
Unilateral Renal Dysplasia:
No treatment is needed in babies presenting with unilateral renal dysplasia and having no symptoms, as the other kidneys are functioning properly. But it is necessary to have regular follow-ups to ensure the proper functioning of the contralateral kidney. It includes:
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Monitoring the blood pressure.
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Treating the urinary tract infections then and there to prevent any complications.
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Performing kidney function test.
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Urine tests are done to check for any signs of proteinuria (presence of protein in the urine).
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Ultrasound of the kidney should be taken at regular intervals to check for the proper growth and functioning of the normal kidney.
Bilateral Dysplasia:
Most babies with this condition are stillborn (they die at birth); the ones that survive birth should be addressed with immediate and aggressive measures such as,
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Hemodialysis - To perform the kidneys function artificially.
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Kidney Transplantation - A kidney transplant would decrease the mortality and morbidity rates in patients with this condition.
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Treating Other Issues - Other systemic problems associated with genetic syndromes should be treated.
What Is the Prognosis of Kidney Dysplasia?
The prognosis of unilateral kidney dysplasia is good due to the normal functioning contralateral kidney. Bilateral kidney dysplasia shows poor prognosis as both kidneys fail to function, resulting in renal failure and death at birth; few who survive after birth also show bad prognosis due to other associated problems.
Conclusion:
Kidney dysplasia is one of the common developmental disorders of the kidneys. Unilateral cases are usually asymptomatic with the normal functioning of the unaffected kidneys. At the same time, bilateral cases show increased mortality due to renal failure and other associated anomalies. Regular monitoring and follow-up are necessary in both cases to improve the survival rates.
