Multicystic dysplastic kidney diseaseQ61.9

MCDK is a severe developmental disorder in which the kidney tissue consists increasingly of cysts and often lacks a renal pelvic calices system. There is no relevant organ function (Manski 2019). Associations with syndromes or chromosomal aberrations are sometimes found (Heinrich 2019). MCDK corresponds to the historical classification "Potter II dysplasia" (Sohn 2013).

With an incidence of 1: 4,300 live births, MCDK is the most common abdominal tumor in newborns (Manski 2019). The unilateral form is found in 1: 1,000, the bilateral in 1: 10,000 live births. The male sex dominates with 2: 1. There are often accompanying other malformations. The recurrence risk for siblings is < 5 % (Sohn 2013).

The cause is not yet known. A fetal ureteral atresia, an abnormal induction of the metanephritic bladder through the ureteral bud or viral infections are suspected (Manski 2019).

Unless the diagnosis has already been made prenatally, children with unilateral involvement and an intact second kidney are clinically inconspicuous. In these cases, the diagnosis is often an incidental finding (Heinrich 2019). On palpation, an abdominal tumor is found in infants or young children (Manski 2019).

In most cases the malformation is detected by sonography as an incidental finding. Since it is not possible to differentiate the diagnosis from a pronounced hydronephrosis on sonography, a renal scintigraphy should be performed for further diagnosis. This can then be used to show the lack of function of the affected kidney. (Heinrich 2019)

Laboratory: There are no abnormalities in unilateral involvement.

Histology: Traces of dysplastic kidney tissue and primitive collecting tubes with cystic dilatation may be detectable (Heinrich 2019).

Renal agenesis (since spontaneous involution usually occurs only postpartum in MCDK).

Simple renal cyst (Manski 2019)

• Hypertension
• Degeneration (but plays practically no role clinically)
• Infection of the organ remnant (Kemper 2020 / Heinrich 2019)

Treatment is usually not possible and not necessary, but regular sonographic controls every 6 - 12 months are necessary, since the risk of a Wilms tumor cannot be excluded. In addition, blood pressure and creatinine should be monitored until involution (involution of the affected kidney almost always occurs in childhood over several years) or until the age of 8. (Manski 2019)

Nephrectomy, which used to be performed in every case, hardly plays a role nowadays. It is now only performed in the case of:

• lack of involution
• very large or enlarging cysts
• arterial hypertension(Heinrich 2019)
• V. a. malignant degeneration (Manski 2019)

Children with unilateral infestations do not have a limited life expectancy, but children with bilateral infestations are often stillborn or die shortly after birth (Heinrich 2019).