Multicystic Renal Dysplasia Workup

Updated: Aug 22, 2016
  • Author: Agnieszka Swiatecka-Urban, MD, FASN; Chief Editor: Craig B Langman, MD  more...
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Workup

Laboratory Studies

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  • A urine for dipstick and microscopic analysis should be obtained in patients with suspected multicystic dysplastic kidney (MCDK). Urine should be sent for culture as needed.
  • Blood tests for creatinine, urea, and electrolytes should be performed.
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Imaging Studies

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  • Renal ultrasonography
    • Renal ultrasonography is the recommended preliminary diagnostic imaging study. [10]
    • Ultrasonography reveals a kidney that contains multiple cysts of variable size that are randomly arranged and are separated by little or no echogenic parenchyma.
    • No renal pelvis is identifiable.
  • Voiding cystourethrography (VCUG)
    • VCUG should be performed to look for vesicoureteral reflux (VUR). Current recommendations for patients with unilateral multicystic dysplastic kidney include evaluation of the contralateral kidney for VUR by VCUG.
    • Although, the necessity of VCUG, an invasive technique, has been increasingly questioned by many authors because of the following observations:
      • VUR has been reported in 4-19% of contralateral kidneys; it is usually low grade and resolves in early life. [22, 15, 16]
      • Repeat ultrasonography examinations of the contralateral kidney are able to detect significant number of renal anomalies. [22]
      • No difference in the incidence of urinary tract infections (UTIs) or renal scaring was observed between children with or without VUR in the contralateral kidney. [15, 23]
    • Routine VCUG may not be necessary for evaluation of unilateral multicystic dysplastic kidney. Two successive normal neonatal renal ultrasonography scans in infants with antenatally diagnosed multicystic dysplastic kidney clinically rules out significant contralateral anomalies, thereby rendering neonatal VCUG unnecessary. Furthermore, VCUG may be deferred, unless abnormal ultrasonography findings in the contralateral kidney or ureter and/or a history of UTI are noted.
  • Dimercaptosuccinic acid (DMSA) renal scanning
    • DMSA renal scanning may be necessary if ultrasonography does not reveal the classic features of multicystic dysplasia of the kidney.
    • DMSA renal scanning demonstrates absence of function in the kidney with multicystic dysplastic kidney.
  • Technetium Tc 99m diethylenetriamine pentaacetic acid (DTPA) or technetium Tc 99m mercaptoacetyltriglycine (MAG-3) renal scanning
    • When ultrasonography reveals a pelvocaliceal system or a dominant central cyst, severe UPJO and renal dysplasia secondary to obstruction may be difficult to differentiate. In these cases, technetium Tc 99m DTPA or technetium Tc 99m MAG-3 renal scanning with furosemide washout is important.
    • In cases of severe hydronephrosis, a peripheral rim of activity might be observed, followed by an increase in excretion noted on delayed images.
    • Delayed images also reveal retention of the DTPA or MAG-3 in the pelvocaliceal system with little or no washout with furosemide.
    • With renal dysplasia secondary to obstruction, degrees of decreased function vary.
  • Intravenous pyelography (IVP): This is not usually necessary; however, if multicystic dysplastic kidney involves only the upper or lower segment of a duplicated system, an IVP might reveal a small but functional ipsilateral kidney with an incomplete and possibly dilated calyceal system.
  • Cystoscopy
    • Cystoscopy is usually unnecessary.
    • If performed, the ipsilateral ureteral orifice and hemitrigone might be absent.
    • When the ureteral orifice is present, retrograde ureterography usually demonstrates a ureter that terminates blindly below the ureteropelvic junction.
  • Cyst puncture: In the rare situation in which severe UPJO cannot be differentiated from multicystic dysplastic kidney by ultrasonography and DTPA renal scanning, a diagnostic puncture of a cyst with instillation of radiographic contrast material might help distinguish these 2 disorders. The presence of cysts connected by tubular structures and the absence of a collecting system is diagnostic of multicystic dysplastic kidney.

A study that evaluated the impact of imaging modalities on the evaluation and prognosis of children with multicystic dysplastic kidney (MCDK) disease reported that the classical appearance of MCDK on renal bladder ultrasound was sufficient to establish the diagnosis in most patients. The authors also concluded that dimercaptosuccinic acid scan was more accurate in confirming the diagnosis and evaluating the contralateral kidney and that selective screening for vesicoureteral reflux in patients with contralateral hydronephrotic kidney should be considered. [24]

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Other Tests

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  • An annual assessment of blood pressure should be performed.
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Histologic Findings

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  • The kidney with multicystic dysplastic kidney is enlarged, abnormally shaped, and often resembles a bunch of grapes. The numerous and irregularly sized cysts range from less than 1 mm to several centimeters in diameter.
  • In a study of 48 patients, fewer than 5 cysts were noted in 34% of patients, and 5 or more cysts were noted in 66% of patients. [25]
  • The cysts contain a clear or yellow fluid and are connected by a fibrous tissue stroma. The usual reniform configuration of the kidney is obscured by the cysts and by a lack of pelvocaliceal differentiation. Rudimentary lobes are sometimes grossly identifiable. Nodular masses are present in a medial and central location in some kidneys and might represent pelvic atresia.
  • Multicystic dysplastic kidney might be present in only the upper or lower pole of a duplicated collecting system.
  • Ureteral or ureteropelvic atresia is always present.
  • The atretic portion of the ureter varies in length from 1-5 cm.
  • The ipsilateral renal artery is absent or hypoplastic.
  • Primitive epithelial ducts and nests of metaplastic cartilage are the principal microscopic criteria for a diagnosis of multicystic dysplastic kidney.
  • Histopathologic examination reveals abnormal ductal differentiation and only rudimentary corticomedullary differentiation. Thick-walled or thin-walled cysts with smooth inner linings are present throughout the kidney. Normal renal parenchyma is usually absent. The loose connective tissue that surrounds the cysts might range from thin strands to extensive areas of fibrosis.
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