Multicystic Dysplastic Kidney Disease

The Multicystic Dysplastic Kidney (MCDK) is an enlarged kidney whose parenchyma is replaced by multiple, non-communicating cysts, of variable size and number. The ipsilateral ureter is usually atretic and the normal functioning renal parenchyma is commonly scarce or even absent.

Potter type II; multicystic dysplasia; multicystic kidney.

1/1000–5000 live births; unilateral in approximately 75–80% of cases.^1,2 Male to female ratio is 2:1.^3,4

MCDK could be found not only isolated, but also in a wide range of heterogeneous diseases, in association with different urogenital and multi-organ abnormalities. This implies that teratogens, genetic and chromosomal abnormalities could play a role in the etiology of this condition. The possible embryologic causes are either an interference of nephron induction by the metanephric blastema, or a defect of communication between the ureteric bud and the metanephric blastema. A possible role of vascular compromise has also hypothesized.^1,5 The defect should act early during nephrogenesis, leading to early functional impairment and cystic degeneration of the parenchyma.

Cystic dysplastic kidneys are usually enlarged, with an irregular shape. A typical “bunch of grapes” appearance has been described. The pyramids are poorly delineated and cysts are usually well visible, as cystic degeneration, of both cortical and medullary components, is the main feature of this condition. The kidney architecture is therefore compromised, and abnormal representation of ductal, mesenchymal and connective components is usually reported, with additionally evidence of cartilaginous metaplasia, embryonic nephrons and duct, suggesting a developmental defect occurring early during the renal embryogenesis. This parenchymal impairment often involves the vast majority of the renal tissue, leading to functional impairment of the kidney. The ipsilateral ureter is atretic, as mentioned, and the renal artery is also absent, or very small.^1,6

MCDK is unilateral in the majority of cases (approximately 75–80% of cases), but may also be bilateral or segmented, in which case small areas of normal renal parenchyma are also present. Cystic dysplasia has been found in cases of ureteral duplication (often involving the upper pole of the duplex kidney), in ectopic and also in horseshoe kidneys.

The functional impairment of one kidney usually doesn’t significantly affect the amount of amniotic fluid, as the contralateral kidney, if normal, produces enough urine to maintain the fluid volume within normal ranges. In a significant number of of cases, the contralateral kidney appears hypertrophic.7 If MCDK is bilateral, oligo/anhydramnios is usually present. The absence of fluid causes mechanical compression of the chest and impaired development of the lungs, resulting in pulmonary hypoplasia. Oligo/anhydramnios causes also a typical facial appearance (Potter’s facies) and limbs abnormalities of the fetus, known as Potter sequence.

Postnatal studies show that these kidneys have a tendency to progressive involution, during patient’s life.8 In fact, MCDK is considered to be the major cause of apparent unilateral renal agenesis in adults.9

Children with unilateral MCKD have an increased risk of abnormalities of the contra-lateral kidney and the lower urogenital tract (up to 40% of cases1):the most common abnormality is vescicoureteric reflux, but renal agenesis and pelviureteric junction obstruction are not uncommon.8,10Heart, CNS, and gastrointestinal (esophageal atresia, tracheoesophageal fistula, duodenal stenosis, imperforate anus) and limb problems have frequently been reported in association with MCKD1, 11

In case of dysplasia involving both kidneys, oligo/anhydramnios is usually associated, with consequent pulmonary hypoplasia and Potter sequence, as previously mentioned.

The risk of chromosomal anomalies, when MCKD is diagnosed, depends on the presence of associated anomalies : this is relatively low, when MCKD is isolated (2–4%), but reaches 15–18% in bilateral forms and 25–28% when associated with other anomalies.²

The risk of non-chromosomal syndromes is 5–10%.² The most common syndromes possibly associated with MCKD are as follows¹:

- Brachio-otorenal syndrome:the multicystic kidney is associated with pre-auricular tags and branchial cleft-fistulas.

- Cerebrorenodigital syndrome: the multicystic kidney could be found in association with digital and limb anomalies, and CNS malformations.

- VA(C)TER(L) association: multicystic kidney, vertebral anomalies, anal atresia, congenital heart defects, tracheo-esophageal fistula, and limb anomalies are features of this association.

In isolated forms, the risk of recurrence is 3%; in syndromic forms, it is that of the underlying syndrome.²

In the majority of cases, the ultrasound diagnosis can be made by prenatal ultrasound¹², often already in the 2nd trimester. The typical ultrasound appearance is characterized by a single kidney with multiple non-communicating cysts of variable size, mixed with hyperechogenic parenchyma. The dimensions of the kidney are often significantly increased and depend on the number and dimensions of the cysts that do not communicate with a renal pelvis, and could even alter the normal renal shape. The bladder and quantity of amniotic fluid are usually normal. The ultrasound appearance of the contralateral kidney is usually normal, in terms of echogenicity and structure, but in a significant number of the cases, in the third trimester, its volume is increased.⁷ The volume of multicystic kidneys is often increased, and for this reason MCKD represents one of the most common causes of abdominal mass in the neonate. A variety with reduced volume is also described, as is the possibility of evolution into renal hypoplasia.¹ In rare cases, the cystic element may only involve part of the kidney, particularly when associated with the presence of a duplex kidney, as previously described. The ipsilateral renal artery may be absent or small, with the presence of Doppler velocity waveform anomalies. When, less frequently, both kidneys are multicystic, severe oligohydramnios is present and the bladder cannot be visualized. In sporadic cases, the multicystic kidney may also have an ectopic site.²

This mainly involves severe hydronephrosis. When the position of the cysts resembles that of a calicopyelic dilatation, the presence of anomalous renal tissue between the cysts and the lack of communication between the cysts indicates a diagnosis of multicystic kidney.² If the differential diagnosis is particularly difficult, some authors have suggested aspiration of the cystic fluid, which, in the case of multicystic kidney, shows high phosphate levels.¹³

The Cystic Dysplasia - Potter IV usually shows multiple cysts, more often pericortical. It usually involves both kidneys ( being often associated with early and severe obstruction of the urethra) and the dimensions of kidneys are normal/decreased.

In Meckel-Gruber syndrome, cysts are usually small and uniform, scattered throughout the kidney.⁴

In the rare case of ectopic MCDK, its appearance may simulate ovarian cysts. The visualization of an empty renal fossa, usually occupied by a “lying down” adrenal, is helpful to diagnose the displacement of the kidney.

The evaluation of kidneys and bladder in the first and second trimester routine scans usually allows a good detection for this abnormality.¹² Diagnosis of MCKD has been reported even before 16 weeks¹⁵, by transvaginal ultrasound. The typical multicystic enlarged appearance of one kidney is often the feature that raises the suspicion of this condition, and represents the indication for referral to second-level ultrasound. An accurate evaluation of the fetal anatomy is mandatory, to be preferably performed in a second-level setting, as the presence of associated anomalies could change the counselling and management of the pregnancy. The characteristics of the cysts and the renal parenchyma usually allow an appropriate differential diagnosis; this evaluation requires good knowledge about kidney diseases and experienced operators. The examination should not be limited to the abnormal kidney, but the contralateral kidney should be clearly visualized and examined. If there is any doubt about its presence in the proper renal loggia, a careful examination of the fetal pelvis should be performed, considering the frequent association with ectopic kidneys.

When MCKD is bilateral, oligo/anhydramnios is the main feature that address the attention of the operator to the bladder, usually not visible and the kidneys, both enlarged and dysplastic, with the already described appearance.

Although occasional cases of infection or hypertension associated with multicystic kidneys have been reported, prognosis, survival, and quality of life are good in the majority of cases of isolated forms.² The affected kidney often decreases in size within the first years of life, becoming no more detectable by ultrasound in about 40% of the cases.¹⁶ It has been shown that if the affected kidney is bigger than 6 cm, often do not involute. These kidneys have higher risk to develop hypertension and malignant transformation (Wilms tumor, renal cell carcinoma).^4,17

In bilateral forms, the prognosis is unfavourable¹⁸ due to the presence of the oligohydramnios, related to the complete renal insufficiency, which may result in the Potter sequence and death from lethal pulmonary hypoplasia. If MCKD is not isolated, the prognosis depends on the associated abnormality.

In case of unilateral involvement, serial ultrasound scans should be arranged in order to follow up the lesion during gestation, as it may sometimes reduce in volume; at the same time, the onset of hydronephrosis (up to 40% of cases) on the contra-lateral kidney should be verified.² When MCKD is unilateral, meticulous long-term (pre- and postnatal) screening of the entire urinary tract is warranted. When the multicystic disease is bilateral, a conservative approach is recommended, after the 24th week, due to the unfavorable prognosis, mainly related to pulmonary hypoplasia.

Fetal karyotyping can be offered considering the association with chromosomal abnormalities, mainly when extrarenal anomalies are present.

After birth, scintigraphy is recommended to confirm the type of lesion in doubtful cases and to evaluate residual renal function. During the early years of life, serial ultrasound follow-up must be carried out, in order to follow up renal size, possible associated anomalies (such as contralateral vescicoureteral reflux, infections) and exclude malignancy transformation. Clinical follow up is necessary to exclude the onset of hypertention.4 Nephrectomy is recommended if the multicystic kidney is symptomatic, being responsible for hypertension, hematuria, or infection. In this regard, it must be remembered that during the first 2 years of life, there is a high chance of involution of the multicystic kidney.In case of termination, stillbirth or abortion, post-natal autopsy may be advisable for diagnosis confirmation and further counselling, especially in case of discordancy with prenatal assessment.^19,20,21

1. Evans JA. Urinary tract. In: Stevenson RE, Hall JG. Human Malformations and Related Anomalies, second edition. Oxford. Oxford University Press. 2006: 1161-90.

2. Paladini D, Volpe P. Ultrasound of Congenital Fetal Anomalies. Informa Healthcare, 2007.

3. Van Eijk L, Cohen-Overbeek TE, den Hollander NS, Nijman JM, Wladimiroff JW. Unilateral multicystic dysplastic kidney: a combined pre- and postnatal assessment. Ultrasound Obstet Gynecol. 2002 Feb;19(2):180-3.

4. Bianchi D, Crombleholme T, D' Alton M, Malone F. Fetology: Diagnosis and Management of the Fetal Patient. Second Edition. McGraw Hill Professional, 2010; 589-95.

5. Thomsen HS, Levine E, Meilstrup JW, Van Slyke MA, Edgar KA, Barth JC, Hartman DS. Renal cystic diseases. EurRadiol. 1997;7(8):1267-75.

6. Twining P. Genitourinary Malformation. In: Nyberg DA, McGahan JP, Pretorius DH, Pilu G (eds): Diagnostic Imaging of Fetal Anomalies. Lippincott Williams & Wilkins, Philadelphia, 2003: 610-14.

7. Van Vuuren SH, Van der Doef R, Cohen-Overbeek TE, Goldschmeding R, Pistorius LR, de Jong TP. Compensatory enlargement of a solitary functioning kidney during fetal development. Ultrasound Obstet Gynecol. 2012 Dec;40(6):665-8. doi: 10.1002/uog.11168

8. Chapman T. Fetal genitourinary imaging. PediatrRadiol. 2012 Jan;42Suppl 1:S115-23.

9. Aslam M, Watson AR; Trent & Anglia MCDK Study Group. Unilateral multicystic dysplastic kidney: long term outcomes. Arch Dis Child. 2006 Oct;91(10):820-3.

10. Atiyeh B, Husmann D, Baum M. Contralateral renal abnormalities in patients with renal agenesis and noncystic renal dysplasia. Pediatrics. 1993 Apr;91(4):812-5.

11. Mir S, Rapola J, Koskimies O. Renal cysts in pediatric autopsy material. Nephron. 1983;33(3):189-95.

12. Kuwertz-Broeking E, Brinkmann OA, Von Lengerke HJ, Sciuk J, Fruend S, Bulla M, Harms E, Hertle L. Unilateral multicystic dysplastic kidney: experience in children. BJU Int. 2004 Feb;93(3):388-92.

13. Nicolini U, Vaughan JL, Fisk NM, et al. Cystic lesions of thefetal kidney: diagnosis and prediction of outcome. J PediatrSurg 1992; 27: 1451–5.

14. Sanders RC. Multicystic dysplastic kidney. In: Sanders RC, Blackman LR, Hagge WA, Wolfsberg ED, eds. Structural fetal abnormalities: the total picture. Mosby-Year Book, Philadelphia, 1996.

15. Bronshtein M, Yoffe N, Brandes JM, Blumenfeld Z. First and early second-trimester diagnosis of fetal urinary tract anomalies using transvaginalsonography. PrenatDiagn. 1990 Oct;10(10):653-66.

16. Rottenberg GT, Gordon I, De Bruyn R.The natural history of the multicystic dysplastic kidney in children.Br J Radiol. 1997 Apr;70(832):347-50.

17. Homsy YL, Anderson JH, Oudjhane K, Russo P.Wilmstumor and multicystic dysplastic kidney disease.J Urol. 1997 Dec;158(6):2256-9; discussion 2259-60.

18. Damen-Elias HA, De Jong TP, Stigter RH, Visser GH, Stoutenbeek PH.Congenital renal tract anomalies: outcome and follow-up of 402 cases detected antenatally between 1986 and 2001.Ultrasound Obstet Gynecol. 2005 Feb;25(2):134-43.

19. Kumari N, Pradhan M, Shankar VH, Krishnani N, Phadke SR. Post-mortem examination of prenatally diagnosed fatal renal malformation. J Perinatol. 2008 Nov; 28(11):736-42.

20. Gupta T, Kapoor K, Sharma A, Huria A. The Frequencies of the Urinary Anomalies which were Detected in a Foetal Autopsy Study. J ClinDiagn Res. 2012 Dec; 6(10):1615-9.

21. Isaksen CV, Eik-Nes SH, Blaas HG, Torp SH. Fetuses and infants with congenital urinary system anomalies: correlation between prenatal ultrasound and postmortem findings. Ultrasound Obstet Gynecol. 2000 Mar;15(3):177-85.

Volpe P, Volpe N, De Robertis V., Multicystic dysplastic kidney, Visual Encyclopedia of Ultrasound in Obstetrics and Gynecology,www.VISUOG.org, 30th of March, 2013.

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