Normal non-atretic ureter in multicystic dysplastic kidney: Report of two cases.

Sir,

Multicystic dysplastic kidney (MCDK) lacks a discernible pelvis and calices, and is nearly always associated with atresia at the uretero-pelvic junction.[1] Finding a ureter till the bladder in a case of MCDK is a rare of the rarest observation, which needs to be reported.

A three-year-old male child presented with a history of recurrent urinary tract infection for the last 2 years. A USG showed presence of randomly arranged non-communicating multiple cysts of varying sizes with little renal parenchyma on the right side, and a Dimercaptosuccinic acid (DMSA) scan showed an absence of renal function. Diagnosis of right MCDK was confirmed. Micturating cystourethrogram (MCU) showed contralateral grade III reflux. Intraoperatively, the kidney was replaced by multiple cysts, and normal ureter was seen distally till the bladder [Figure 1a]. Histopathological examination confirmed MCDK with normal distal ureter. The second case was a five-year-old female child with antenatally diagnosed left MCDK in close follow-up, having persistent hypertension, and not responding to medical management was taken up for surgery after investigations such as USG, MCU, and DMSA. Contralateral kidney was normal. Retroperitoneoscopic nephroureterectomy was performed. Intraoperatively, we found a multicystic kidney and normal ureter [Figure 1b] going till the bladder. Specimen sent for histopathological examination confirmed the finding of MCDK with intact non-atretic ureter. The child became normotensive two months after surgery.

Figure 1

(a): Intraoperative view (case 1) showing multicystic kidney with normal ureter [asterix: individual cyst, arrow: ureter] (b): Lumboscopic view (case 2) showing multicystic kidney with normal ureter [asterix: individual cyst, arrow: ureter]. Figure 1(b) was reproduced with permission from Editor-in-chief, JPPU [Journal of Progress in Paediatric Urology 2013; 16(1): 10]

It is important to distinguish between MCDK, poorly functioning hydronephrotic kidneys (caused by pelviureteric junction obstruction), and a rarely multilocular cystic renal tumor. MCDK is characterized by tense, non-communicating cysts, non-medial location of largest cyst, and absence of functioning renal parenchyma, mostly associated with atresia or hypoplasia of the ureter. The poorly functioning hydronephrotic kidneys may have reniform configuration, cysts organized around periphery of the kidney, central medial cyst (renal pelvis), connections between peripheral cysts, and the medial cyst. Multilocular cystic renal tumor is a very rare tumor of the neonatal kidney and can be composed predominantly of large cysts. USG may show a multicystic lesion, cysts circumscribed by a thick capsule, and cystic areas are between solid areas. Advancements in USG have provided a high diagnostic accuracy for identifying MCDK. To address the unusual finding of non-atretic ureter in MCDK, understanding the embryological basis of this condition is required. The pathogenesis of MCDK is unknown; there is possibly a perturbation of the interaction between the ureteric duct and metanephric blastema.[2] Atresia of pelvis and ureter and an absent arterial supply is also common.[3] The majority of dysplastic kidneys are associated with urinary tract obstruction commencing in early embryonic life.[2] Two phenotypes of renal dysplasia are associated with urinary tract abnormality: MCDK and obstructive dysplasia (ORD).[4] According to the previous description by Potter and co-workers, cystogenesis of renal dysplasia is thought to be an inhibition of the ampullary activity of the ureteric buds preventing induction of nephrons, causing cessation of branching and converting ampullary portions.[5]

The embryological basis of this condition is not fully elucidated; in the near future, further understanding of embryology is required to answer the finding of non-atretic ureter in cases of MCDK.