Ellen Shapiro, MD, FACS
Daniel Wollin, MD
BASICS
DESCRIPTION
• Multicystic dysplastic kidney (MCDK) is a congenital renal anomaly with a kidney comprised of cysts of varying sizes; no identifiable renal parenchyma—”bunch of grapes” with a paucity of stroma between cysts; no large central or medial cyst
• No reniform appearance of the involved kidney
• Usually unilateral; bilateral incompatible with life
• Most common type of renal cystic disease and 2nd most common cause of abdominal mass in neonates and infants after hydronephrosis
EPIDEMIOLOGY
Incidence
• 1 in 4,300 live births (unilateral)
• Slight male predominance
• Slightly greater occurrence on the left
• Bilateral MCDK
– 1 in 10,000—fet al demise due to oligohydramnios or postnatal demise due to pulmonary hypoplasia
Prevalence
N/A
RISK FACTORS
• Possible association with in utero urinary obstruction
• Possible association with teratogens (in utero viral infections, medications such as maternal antiepileptics)
• Maternal diabetes
Genetics
• MCDK seen in disorders of known genetic etiology such as renal cysts and diabetes syndrome (RCAD) which involves mutations in hepatocyte nuclear factor-1β
• Genes such as PAX2, EYA1, SIX1, WNT, WT-1, GNF, and AT2 have an important role in ureteral bud formation and mutations have been identified in human syndromes such as:
– Branchio-oto-renal (BOR) syndrome with mutations in the EYA1 or SIX1 genes
– Renal-coloboma syndrome (RCS) with mutations in the PAX2 gene
• Linking genetic mutations with renal dysplasia suggest bud theory as the pathogenesis in MCKD
PATHOPHYSIOLOGY
• Ureteral bud theory:
– If ureteral bud is atretic or connects abnormally with the metanephric blastema or forms abnormal distal ureteral connections to the bladder, MCDK will result.
– Prerequisite is the normal reciprocal induction between a normal ureteral bud and normal metanephric mesenchyme.
ASSOCIATED CONDITIONS
• Prenatal hypertrophy of the contralateral kidney (24–46%)
• About 1/3 will have associated congenital anomalies of kidneys and urinary tract (CAKUT)
• Contralateral vesicoureteral reflux (∼20%); of those with reflux, 40% will have grades III–V
• Contralateral UPJ obstruction (3–12%) and UVJ obstruction (6%)
• Dilated nonobstructed contralateral renal pelvis (common)
• Anomalies of the ipsilateral internal duct structures (15%) including seminal vesicle cyst, Gartner’s cyst, obstructed hemivagina
• Large series show no increased incidence of Wilms tumor or hypertension (see Patient Monitoring)
• Ureterocele or ectopic ureter associated with single system or upper pole of duplex system
• Horseshoe kidney
GENERAL PREVENTION
N/A
DIAGNOSIS
HISTORY
At least 65% are detected prenatally
PHYSICAL EXAM
• Abdominal mass palpable in 13%
• Elevated BP (rare)
DIAGNOSTIC TESTS & INTERPRETATION
Lab
• Urinalysis
• Urine microalbuminuria
Imaging
• US: Multiple noncommunicating cysts of variable size, scant, or no renal parenchyma
• Dilated renal pelvis in hydronephrotic form
• VCUG not absolutely recommended with normal contralateral kidney and bladder despite 20% having contralateral reflux
• Renal scan (DMSA): Confirms absence of function, or rarely minimal function especially in hydronephrotic form or in smaller more solid dysplastic kidneys
Diagnostic Procedures/Surgery
• VCUG: To evaluate for contralateral VUR if hydronephrosis or other contralateral upper tract abnormality on US
– If the contralateral kidney is normal, performing a VCUG remains controversial
Pathologic Findings
• Renal maldevelopment with large cysts tend to have a small amount of stroma (thin septa of fibrous tissue) and primitive dysplastic elements
– Primitive ducts (a duct encircled by a collar of fibromuscular cells)
– Immature cartilage and remnants of early metanephros can be present
• Kidneys with smaller cysts tend to have more solid components
• Hydronephrotic form
• Small to no vascular pedicle
• Ureter totally or partially atretic; renal pelvis may be absent
• Microscopic communication between cysts
• Often involute—circumscribed rims of calcifications may be seen in the renal fossa on plain film of adults
DIFFERENTIAL DIAGNOSIS
• Acquired renal cysts
• Autosomal dominant kidney disease
• Cystic congenital mesoblastic nephroma
• Cystic Wilms tumor
• Cysts of the medulla
• Hydronephrosis
• Multilocular cystic nephroma
• Neuroblastoma (calcifications)
• Renal cysts, isolated or associated with syndromes (tuberous sclerosis, von Hippel–Lindau, etc.)
• Ureteropelvic junction obstruction (UPJO)
• Vesico ureteral reflux (VUR)
TREATMENT
GENERAL MEASURES
• Educate parents about the signs and symptoms of UTI in infancy and childhood especially if reflux status unknown
• The use of nephrectomy to manage MCDK is controversial
MEDICATION
First Line
N/A
Second Line
N/A
SURGERY/OTHER PROCEDURES
• Mostly nonoperative:
– 25% totally involute
– 60% regress
– 15% remain stable
– A very small number may increase in size
• Indications for nephrectomy:
– Kidneys which remain large, increase in size, or show an increased amount of solid tissue (especially with function)
– Kidneys easily removed (especially laparoscopically) or cysts may be sequentially decompressed
– Hypertension: Uncommon (5%) in childhood and not likely caused by MCDK
May persist after nephrectomy depending on the patient age at onset of hypertension and the presence of CAKUT (see Prognosis)
ADDITIONAL TREATMENT
Radiation Therapy
N/A
Additional Therapies
N/A
Complementary & Alternative Therapies
N/A
ONGOING CARE
PROGNOSIS
• Usually excellent in unilateral disease
• KIMONO study (1) reports renal injury (hypertension, albuminuria and/or the use of renoprotective medication) present in 32% at young age (mean age 9.5 yr).
– Increased renal injury in individuals with a solitary functioning kidney in later life when CAKUT present.
– Study suggests long-term clinical follow-up for hypertension and microalbuminuria especially into puberty and adulthood.
– These findings are supported by an early study (2).
COMPLICATIONS
• Malignant transformation extremely low with only 15 cases of tumors reported
• Rare hypertension; usually associated with contralateral renal injury
FOLLOW-UP
Patient Monitoring
• Renal US to document involution and contralateral renal growth
– Every 6 mo in the 1st 3 yr and then every 1–2 yr to assure appropriate renal growth until puberty
– Protocol personal preference of physician since there is no consensus; some follow patients every 3–12 mo. No frequency of follow-up has been shown to be beneficial or cost-effective
• As of 2012, the American Academy of Pediatrics states that contact-sport participation is generally OK for children who have only one functional kidney. In a very large published series, none of the kidney injuries were catastrophic or needed surgery
• Long-term follow-up for hypertension and microalbuminuria by informed pediatrician or family physician; referral to nephrology for renoprotective medications when indicated
Patient Resources
• National Kidney and Urologic Diseases
• Information Clearinghouse (NKUDIC) http://kidney.niddk.nih.gov/kudiseases/pubs/kidneydysplasia/
REFERENCES
1. Westland R, Schreuder MF, Bökenkamp A, et al. Renal injury in children with a solitary functioning kidney–the KIMONO study. Nephrol Dial Transplant. 2011;26(5):1533–1541.
2. Sanna-Cherchi S, Ravani P, Corbani V, et al. Renal outcome in patients with congenital anomalies of the kidney and urinary tract. Kidney Int. 2009;76(5):528–533.
ADDITIONAL READING
• Abou Jaoudé P, Dubourg L, Bacchetta J, et al. Congenital versus acquired solitary kidney: Is the difference relevant? Nephrol Dial Transplant. 2011;26(7):2188–2194.
• Hains DS, Bates CM, Ingraham S, et al. Management and etiology of the unilateral multicystic dysplastic kidney: A review. Pediatr Nephrol. 2009;24(2):233–241.
• Hayes WN, Watson AR; Trent & Anglia MCDK Study Group. Unilateral multicystic dysplastic kidney: Does initial size matter? Pediatr Nephrol. 2012;27(8):1335–1340.
• Mansoor O, Chandar J, Rodriguez MM, et al. Long-term risk of chronic kidney disease in unilateral multicystic dysplastic kidney. Pediatr Nephrol. 2011;26(4):597–603.
• Psooy K. Multicystic dysplastic kidney in the neonate: The role of the urologist. Can Urol Assoc J. 2010;4(2):95–97.
• Schreuder MF, Westland R, van Wijk JA. Unilateral multicystic dysplastic kidney: A meta-analysis of observational studies on the incidence, associated urinary tract malformations and the contralateral kidney. Nephrol Dial Transplant. 2009;24(6):1810–1818.
• Thomas DF. Prenatally diagnosed urinary tract abnormalities: Long-term outcome. Semin Fet al Neonatal Med. 2008;13(3):189–195.
See Also (Topic, Algorithm, Media)
• Multicystic Dysplastic Kidney Image 
• Potter Syndrome/Potter Facies
• Renal Cysts
• Renal Dysplasia, Hypodysplasia, and Hypoplasia
CODES
ICD9
• 593.70 Vesicoureteral reflux unspecified or without reflux nephropathy
• 753.15 Renal dysplasia
• 753.19 Other specified cystic kidney disease
ICD10
• Q61.4 Renal dysplasia
• Q62.7 Congenital vesico-uretero-renal reflux
• Q62.39 Other obstructive defects of renal pelvis and ureter
CLINICAL/SURGICAL PEARLS
• MCDK occurs as a result of renal maldevelopment due to possible mutation(s) in genes responsible for ureteral bud formation.
• Large cysts of varying sizes present with no identifiable parenchyma; ureter usually atretic.
• Most involute or become significantly smaller; rare enlargement.
• Almost none require nephrectomy; consider for functioning solid component or increasing size.
• Not associated with increased risk of hypertension during childhood or Wilms tumor in large series.
• Long-term follow-up recommended for hypertension and microalbuminuria especially at puberty and in adulthood.