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Multicystic Dysplastic Kidney, Pediatric

Basics

Description

- Associated anomalies of contralateral GU tract include the following: - Vesicoureteral reflux, most common, occurs in ’ Ό25% - Renal hypoplasia - Ureterocele - Ureteropelvic junction (UPJ) obstruction - Genital anomalies

- Renal ultrasound - To confirm diagnosis of MCDK and evaluate the contralateral kidney - Usually no detectable Doppler flow - Useful to follow involution of MCDK and hypertrophy of contralateral kidney - 50% will have complete involution by 5 years. - Should be done after birth and at 1 month, 2 years, 5 years, and 10 years of life

- Blood pressure monitoring - Anecdotally, these patients were thought to be at risk for hypertension. - However, more recent studies show no increased risk.

  • Multicystic dysplastic kidney disease (MCDK) is the most severe type of cystic renal dysplasia and is characterized by multiple, noncommunicating cysts which are divided by dysplastic tissue.
  • In general, there is no functioning renal tissue in a multicystic dysplastic kidney.
  • Involutes over time (usually within the first 5 years)

Epidemiology

  • Incidence is 0.3 " 1 in 1,000 live births.Most cases are detected antenatally.
  • Affects boys > girls
  • Left kidney > right kidneyUsually unilateral but can be bilateral

Pathophysiology

  • Initial growth of the ureteric bud is normal, but renal development halts at a later stage.
  • Histology shows disordered renal tissue with areas of undifferentiated mesenchymal cells, abnormal differentiation (i.e., cartilage), rare nephrons

Commonly Associated Conditions

  • Associated anomalies of contralateral GU tract include the following:Vesicoureteral reflux, most common, occurs in ’ Ό25%Renal hypoplasiaUreteroceleUreteropelvic junction (UPJ) obstructionGenital anomalies

Diagnosis

History

Commonly diagnosed by antenatal ultrasound

Physical Exam

  • Blood pressure at each visit to monitor for hypertension
  • Evaluate height and weight
  • Neonates: Palpable flank mass may be present.

Diagnostic Tests & Interpretation

Lab

  • CreatinineIf unilateral kidney is normal, serum creatinine should be normal.One strategy is to monitor serum creatinine at 1 month, 18 months, 5 years, and when growth complete to detect reduced function in remaining kidney.
  • Urinalysis to check for proteinuria to evaluate for hyperfiltration in remaining kidney.
  • Urinalysis and urine culture, if the patient has any symptoms of UTI or unexplained fever

Imaging

  • Renal ultrasoundTo confirm diagnosis of MCDK and evaluate the contralateral kidneyUsually no detectable Doppler flowUseful to follow involution of MCDK and hypertrophy of contralateral kidney50% will have complete involution by 5 years.Should be done after birth and at 1 month, 2 years, 5 years, and 10 years of life
  • Voiding cystourethrogram (VCUG)To evaluate for urinary reflux is controversial.Although rate of VUR is high, most is low-grade and would not require prophylactic antibiotics.Patients with febrile UTI should have a VCUG.
  • Mercaptoacetyl-triglycine (Mag3) scanTo confirm diagnosis and rule out a kidney with severe hydronephrosis

Differential Diagnosis

Hydronephrotic kidney with poor function

Alert

If contralateral kidney is abnormal, renal function should be evaluated, and the patient requires ongoing nephrology follow-up.

Treatment

Medication

Occasionally, these patients may require antihypertensive medication, an ACE-inhibitor for proteinuria, or urologic evaluation if they suffer from severe VUR or recurrent UTI.

General Measures

  • No specific treatment is needed for MCDK.
  • Previously, nephrectomy was treatment of choice; however, given low risk of hypertension and malignancy, currently, routine nephrectomy of MCDK is not recommended.

Ongoing Care

Follow-up Recommendations

  • Blood pressure monitoringAnecdotally, these patients were thought to be at risk for hypertension.However, more recent studies show no increased risk.
  • Patients may be at increased risk for developing Wilms tumor in MCDK.Risk 3 " 10 per 10,000Monitored with periodic renal ultrasound and abdominal exam
  • Periodic urinalysis to evaluate for proteinuria and serum Cr to monitor renal function

Prognosis

  • Patients with contralateral anomalies are at greater risk for developing chronic kidney disease (CKD).
  • Patients with normal contralateral kidneys may have hyperfiltration ( ’ Ό30%) and proteinuria ( ’ Ό10%).
  • Risk of developing Wilms tumorMay be as high as 3 " 10 times higher than the general population (1 in 10,000)This estimate is controversial, however, as a systematic review of 1,041 children with unilateral MCDK found no cases of Wilms tumor

Additional Reading

  • Aslam M, Watson AR. Unilateral multicystic dysplastic kidney: long term outcomes. Arch Dis Child. 2006;91(10):820 " 823. [View Abstract]
  • Mansoor O, Chandar J, Rodriguez M, et al. Long-term risk of chronic kidney disease in unilateral multicystic dysplastic kidney. Pediatr Nephrol. 2011;26(4):597 " 603. [View Abstract]
  • Onal B, Kogan B. Natural history of patients with multicystic dysplastic kidney " what follow-up is needed? J Urol. 2006;176(4, Pt 1):1607 " 1611. [View Abstract]
  • Weinstein A, Goodman TR, Iragorri S. Simple multicystic dysplastic kidney disease: end points for subspecialty follow-up. Pediatr Nephrol. 2008;23(1):111 " 116. [View Abstract]

Codes

ICD09

  • 753.15 Renal dysplasia
  • 753.12 Polycystic kidney, unspecified type

ICD10

  • Q61.4 Renal dysplasia
  • Q61.3 Polycystic kidney, unspecified

SNOMED

  • 204949001 Renal dysplasia (disorder)
  • 82525005 Congenital cystic kidney disease (disorder)

FAQ

  • Q: What can be done to preserve contralateral renal function?
  • A: Well-controlled blood pressure, treatment of proteinuria, and quick treatment of UTI may decrease the progression of CKD.
  • Q: Are patients with MCDK at an increased risk for developing a UTI?
  • A: No. Risk of UTI is ’ Ό5%, consistent with general pediatric population. However, if a patient with MCDK has a febrile UTI, a VCUG is recommended to evaluate for VUR.
  • Q: Can patients with unilateral MCDK live a normal life?
  • A: Yes, if the contralateral kidney is normal. Patients should be encouraged to live a healthy lifestyle. If the patient has hypertension or diabetes, they should be tightly controlled.
  • Q: How is this different than polycystic kidney disease?
  • A: Polycystic kidney disease (PKD) tends to affect both kidneys and is a progressive disorder. Infants with PKD have relatively normal kidneys at birth and cystic disease develops over time. MCDK is not progressive and usually affects one kidney. PKD is an inherited condition, whereas MCDK is usually not inherited.