How is multicystic dysplastic kidney differentiated from Wilms tumor on imaging?

Updated: Mar 04, 2019
  • Author: Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR; Chief Editor: Eugene C Lin, MD  more...
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Multicystic dysplastic kidney is a relatively rare condition. Even so, it is the most common cause of abdominal masses in neonates, leading to 50-65% of renal masses in infancy.

Multicystic dysplastic kidney is a developmental anomaly due to atresia of the upper third of the ureter. In most cases, concomitant atresia affects the renal pelvis and infundibula. The underlying obstruction usually occurs at or before 8-10 weeks of life. Obstruction occurring at a stage later than this gives rise to a relatively rare combination of renal dysplasia and hydronephrosis.

About 33% of patients have contralateral renal anomalies, such as multicystic dysplastic kidney, pelviureteric junction (PUJ) obstruction, hypoplasia, and rotational anomalies. When ureteric duplication is encountered on the contralateral side, one of the ureters may be atretic, with associated segmental renal dysplasia.

Ultrasonography demonstrates a large unilateral renal mass with 10-20 cysts but sometimes as many as 50 cysts of various sizes. Islands of dysplastic renal tissue may be observed between the cysts, but no normal tissue is seen. Antenatal diagnosis is possible. Ultrasonographic findings can help in differentiating multicystic dysplastic kidney and hydronephrosis from other conditions in infants, such as Wilms tumor, neuroblastoma, mesoblastic nephroma, and adrenal hemorrhage.

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