MULTICYSTIC RENAL DYSPLASIA

Multicystic renal dysplasia (MCRD) is a rare lesion of the renal parenchyma occurring in 1:10,000 births.

• Sporadic or as a recurrent familial trait.
• Pathogenesis
  Unknown, but thought to due to obstruction in most cases (1).

CLASSIFICATION

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ULTRASOUND OF THE CLASSICAL FORM

• Unilateral or rarely bilateral (2).
• Multiple renal cysts (due to segmental blocking of collecting tubules and surrounding dysplastic renal parenchyma) - "cluster of grapes".

	Unilateral Multicystic renal dysplasia
Bilateral multicystic renal dysplasia
	Multiple cysts of varying size No communication between cysts Large kidney
	Normal contralateral kidney

• May affect the entire kidney or only a portion of the kidney(segmental) and urine production is therefore variable.

Segmental multicystic renal dysplasia
Multicystic renal dysplasia lower pole left kidney	Normal right kidney

• The cysts are of varying size and shape and distributed in an irregular pattern throughout the kidney. Large peripheral cysts enlarge and distort the reniform contour ("bunch of grapes").
• The cysts are non communicating, with areas of echogenicity typically surrounding the cysts.

	Multiple non communicating cyst Peripheral location No central renal pelvis

· Size of cysts variable, but may reach considerable dimensions and appear to occupy a large portion of the abdominal cavity.

• Echogenic areas within the affected kidney reflect the presence of calcification in the areas of missing tissue.
• No normal renal parenchyma is discernible (especially with advanced disease).
• Kidney size may be normal, small or enlarged.
• The renal pelvis and ureter are not visualized.
• The ipsilateral renal artery is hypoplastic or atrophic.

• Amniotic fluid normal in unilateral disease.
• Marked oligohydramnios in bilateral disease, which is invariably fatal.

Classical multicystic renal dysplasia
	Pathological Specimen Multiple non-communicating cysts. No renal cortex. Atresia of the mid ureter.
Non functioning kidney on nuclear medicine scan

ULTRASOUND OF THE ATYPICAL FORM

• Difficult to distinguish from hydronephrosis as the renal pelvis communicates with peripheral cysts which resemble dilated calyces.

ASSOCIATED ANOMALIES

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DIFFERENTIAL DIAGNOSIS

1. Hydronephrosis.
   The classical form is easily distinguished from hydronephrosis. In hydronephrosis, the reniform shape of the kidney is preserved, normal renal parenchyma is present peripherally and the cystic areas are anatomically aligned and communicate with a dilated renal pelvis. the ureter may also be dilated in distal obstructions.
2. Trisomy 13.
3. -30% have cystic kidneys.
4. Meckel-Gruber syndrome.
   Bilateral cystic kidneys, oligohydramnios, cleft lip, microcephaly and cephalocele.
5. Less commonly cystic renal dysplasia has been reported in several chondrodysplasia syndromes, Roberts syndrome, Jeune syndrome, trisomy 9, Zellweger syndrome, Ivermark syndrome, type 2 glutaric aciduria.

REFERENCES

1. Rizzo N, Gabrielly S, Pilu G et.al. Prenatal diagnosis and obstetrical management of multicystic dysplastic kidney disease. Prenat Diagn 1987;7:109.
2. D'Alton ME, Romero R, Grannum P et.al. Antenatal diagnosis of renal anomalies by ultrasound. IV: Bilateral multicystic kidney disease. Am J Obstet Gynecol 1986;54:532.