The kidney is enlarged and heavy. On cut section, the renal pelvis and calyces are dilated and cystic and contain a large stone in the pelvis of the kidney (arrow). The cystic change is seen to extend into renal p arenchyma, compressing the cortex as a thin rim at the periphery . Unlike polycystic kidney, however, these cysts are communicating with the pelvi-calyceal system.