Kidney dysplasia is a congenital condition where one or both kidneys do not develop properly while a baby is growing in the womb. This malformation results in kidneys that may be smaller, abnormally shaped, and often contain fluid-filled sacs called cysts. These cysts replace normal kidney tissue, preventing the affected kidney from functioning as it should.
Understanding Kidney Dysplasia
Kidney dysplasia involves an abnormal formation of kidney tissue during fetal development, leading to a disorganized internal structure. Instead of the typical filtering units and collecting ducts, the dysplastic kidney may contain primitive, underdeveloped structures and numerous cysts. These cysts interfere with the kidney’s ability to filter waste and excess fluid from the blood. The extent of this abnormal development varies, ranging from mild cases where some function is retained to severe cases where the kidney has minimal or no function.
The impact on kidney function depends on whether one or both kidneys are affected. If only one kidney is dysplastic, the healthy kidney can often compensate by growing larger and performing the work of both. In such unilateral cases, individuals may experience few, if any, health problems. However, if both kidneys are affected, the condition can lead to severe kidney impairment, potentially resulting in kidney failure early in life.
Forms and Underlying Causes
Kidney dysplasia encompasses several forms, each with distinct characteristics and potential causes. Multicystic dysplastic kidney (MCDK) is a common type, characterized by multiple non-communicating cysts of varying sizes that replace normal kidney tissue, often giving the kidney a “bunch of grapes” appearance. An MCDK typically has no or minimal function and may shrink over time, sometimes disappearing entirely. In about 1 in 1,000 to 1 in 4,300 live births, MCDK affects only one kidney, with bilateral MCDK being much rarer and often incompatible with survival.
Renal hypoplasia is another form, where one or both kidneys are smaller than normal, with a reduced number of nephrons, but often retain a relatively normal structure. The severity depends on whether one or both kidneys are affected and the degree of nephron reduction.
Polycystic kidney diseases, such as Autosomal Recessive Polycystic Kidney Disease (ARPKD) and Autosomal Dominant Polycystic Kidney Disease (ADPKD), can also present with dysplastic features or cysts. ARPKD is a rare genetic disorder characterized by numerous small cysts and often associated with liver abnormalities. The kidneys are often symmetrically enlarged in early childhood. ADPKD is more common and involves progressive growth of fluid-filled cysts, though symptoms usually appear in adulthood.
The underlying causes of kidney dysplasia are varied. In many cases, the exact cause remains unknown, often occurring as a random event. Genetic factors play a role in some instances, with certain gene mutations or chromosomal abnormalities being linked to the condition. Non-genetic factors can also contribute, including certain medications taken during pregnancy, such as some blood pressure medications. Urinary tract obstructions during fetal development can also lead to urine retention and abnormal kidney development.
Recognizing and Diagnosing Kidney Dysplasia
Recognizing kidney dysplasia can be challenging as many cases, especially if only one kidney is affected, may not present with noticeable symptoms. When symptoms do occur, they can include a palpable abdominal mass. Other potential signs include urinary tract infections, high blood pressure, or indicators of reduced kidney function such as:
- Fatigue
- Loss of appetite
- Changes in urination
- Nausea
- Pale skin
- Swelling of the face and legs
Children with kidney dysplasia may also experience headaches or growth retardation.
Diagnosis often begins during pregnancy with a prenatal ultrasound, which can detect abnormalities in the fetal kidney(s). An ultrasound might show kidneys that are smaller than usual, abnormally shaped, or contain cysts. The amount of amniotic fluid is also measured, as a low level can indicate poor kidney function. If kidney dysplasia is suspected prenatally, further scans may be needed to assess the baby’s condition.
After birth, diagnosis is confirmed through postnatal investigations. A renal ultrasound is performed to examine the size, shape, and structure of the kidneys and other parts of the urinary system. A voiding cystourethrogram (VCUG) may be conducted to evaluate the bladder and urethra and check for urine reflux. Blood tests are also performed to assess kidney function by measuring certain substance levels. Genetic testing may be considered if a hereditary cause is suspected.
Managing Kidney Dysplasia
Managing kidney dysplasia involves a range of approaches tailored to the individual’s condition severity and kidney function. For mild cases, regular observation and supportive care are often sufficient. This includes periodic follow-up appointments with specialists to monitor kidney function, blood pressure, and overall growth. The dysplastic kidney may naturally shrink or disappear over time.
If complications arise, medical management becomes more active. High blood pressure, a common issue, is managed with medications to prevent damage to the healthy kidney and slow the progression of kidney disease. Urinary tract infections may require antibiotic treatment. Children with decreased kidney function may also be treated for associated complications like anemia or bone disease with medications and vitamins.
Surgical interventions are sometimes necessary, especially if there are associated urinary tract obstructions or if a severely dysfunctional kidney causes problems. For instance, removal of a non-functioning kidney (nephrectomy) may be considered if it causes pain, high blood pressure, or recurrent infections. Surgical correction of urinary tract obstructions may also be performed to improve urine flow and protect the healthy kidney.
For severe cases leading to kidney failure, more intensive treatments are required. Dialysis filters waste and excess fluid from the blood when the kidneys can no longer do so. Ultimately, kidney transplantation may be recommended, offering a more active life without the need for dialysis. Regular follow-up with specialists is important for all individuals with kidney dysplasia to monitor kidney health and manage any long-term effects.