Congenital megacalyces is an incidental finding which mimics hydronephrosis. It is a result of underdevelopment of the renal medullary pyramids with resultant enlargement of the calyces. It is more frequently seen in males.
The enlarged, floppy calyces predispose to stasis, infection and calculus formation. There is an association with congenital megaureter.
Due to the lack of normal medullary pyramids, not only are the calyces enlarged but they lack the normal imprint from the papillae, thus having a flat appearance 1. The renal pelvis is of normal size helping to distinguish megacalyces from hydronephrosis.
In addition to enlargement of the calyces, there is often also polycalycosis (increased number of calyces); they are crowded and multifaceted with a mosaic-like appearance.
- 1. Vargas B, Lebowitz RL. The coexistence of congenital megacalyces and primary megaureter. AJR Am J Roentgenol. 1986;147 (2): 313-6. AJR Am J Roentgenol (abstract) - Pubmed citation
- 2. Talner LB, Gittes RF. Megacalyces: further observations and differentiation from obstructive renal disease. Am J Roentgenol Radium Ther Nucl Med. 1974;121 (3): 473-86. - Pubmed citation