Renal Dysplasia
Content of This Page
1- Definition & Types
2- Causes (Aetiology)
3- Pathophysiology
4- Clinical Features & Examination
5- Investigations
6- Management
7- Complications
8- Core Concepts
Definition & Types
Renal dysplasia refers to a congenital malformation of the kidney in which normal renal parenchyma is replaced by undifferentiated or disorganized tissue. It represents a developmental abnormality of the kidney and can be unilateral or bilateral.
The most commonly discussed form in Davidson is the multicystic dysplastic kidney (MCDK). This is typically:
Unilateral, affecting one kidney.
Discovered in childhood.
Associated with other congenital urinary tract abnormalities.
Unilateral cases are often asymptomatic and involute (shrink) over time. The contralateral kidney usually undergoes compensatory hypertrophy to preserve function.
Causes (Aetiology)
Renal dysplasia is congenital and may result from:
Genetic mutations (some forms may be inherited).
In utero urinary tract obstruction, such as posterior urethral valves.
Abnormal interaction between the ureteric bud and metanephric blastema during embryogenesis.
It is often associated with:
Vesico-ureteric reflux (VUR)
Urethral obstruction
Ureterocele
Other urinary tract anomalies (e.g. duplex system)
Pathophysiology
In renal dysplasia, disorganized development of renal parenchyma leads to:
Presence of primitive ducts, cartilage, or undifferentiated mesenchyme.
Non-functioning or poorly functioning kidney tissue.
Replacement of normal renal structure by cysts or fibrous tissue.
In multicystic dysplastic kidney, the affected kidney contains multiple non-communicating cysts with little or no normal renal tissue.
Often, renal dysplasia coexists with conditions like reflux nephropathy and may contribute to long-term chronic kidney disease (CKD) if bilateral or if the contralateral kidney is impaired.
Clinical Features & Examination
Unilateral MCDK is usually asymptomatic and discovered on routine antenatal ultrasound or early childhood imaging.
Bilateral renal dysplasia can lead to renal failure in infancy.
If associated with VUR or obstruction, symptoms may include:
Urinary tract infections
Hypertension
Growth retardation
Signs of CKD
In unilateral cases, the contralateral kidney may be palpable (hypertrophied). Ultrasound may show one small or cystic kidney and compensatory hypertrophy of the other.
Investigations
Ultrasound is the first-line imaging modality:
Detects cystic changes and absence of normal renal architecture.
Assesses the size and structure of the contralateral kidney.
DMSA scan (radionuclide imaging): for differential renal function and scarring.
Voiding cystourethrogram (VCUG): to assess for associated vesico-ureteric reflux.
Genetic testing may be warranted in syndromic or familial cases.
Management
Unilateral MCDK:
Usually no intervention required.
Surveillance with periodic imaging and blood pressure monitoring.
Bilateral disease or impaired contralateral kidney:
Requires nephrology follow-up and monitoring of renal function.
May progress to end-stage renal disease (ESRD) requiring renal replacement therapy.
Surgical removal of a dysplastic kidney is rarely needed unless:
There is pain.
Infection is recurrent.
There is uncertainty about malignancy.
Complications
Progressive CKD or ESRD if bilateral or associated with damage to the functioning kidney.
Hypertension
Urinary tract infections
Proteinuria
Increased risk of stones in some cases
Core Concepts
Renal dysplasia is a developmental anomaly that can present in various ways depending on whether it is unilateral or bilateral.
Most unilateral cases are benign, often involuting with time.
It is often associated with other congenital abnormalities of the urinary tract.
Imaging is essential for diagnosis and follow-up.
The key risk is renal insufficiency if both kidneys are involved or if the contralateral kidney becomes damaged.