Renal cysts occur in a variety of diseases in children (table 1). Cysts may be due to nonhereditary fetal malformations, genetic disorders, or they may be rarely acquired. Cysts may also occur as an isolated finding or as part of a syndrome.
An overview of the different forms of pediatric renal cystic disease will be reviewed here.
NONHEREDITARY RENAL MALFORMATION
Cystic renal dysplasia, defined by microscopic features, is due to renal parenchymal malformation of the fetal kidney. As a result, the kidney contains primitive ducts and cysts, and nonrenal tissues such as cartilage, fat, and hematopoietic tissue. (See "Overview of congenital anomalies of the kidney and urinary tract (CAKUT)", section on 'Renal parenchymal malformations'.)
Although the nonheritable mechanisms responsible for this disorder remain unclear, an alteration in renal mitogen expression may in part underlie the abnormalities in renal parenchymal differentiation. One study of multicystic renal dysplasia, for example, found significant temporal and spatial alterations in insulin-like growth factor and insulin-like growth factor binding protein expression during early fetal life and the postnatal period . The pathogenetic significance of these changes is uncertain.
Cystic dysplasia is also often associated with antenatal obstruction of the urinary tract, which may be associated with posterior urethral valves or ureteropelvic junction obstruction. Cystic dysplasia is frequently observed in the atrophic pole of a kidney with duplicated ureters or an ectopic ureterocele.