orifices outside the normal limits of the trigone signify accompanying renal malformations in the corresponding kidneys , such as hypoplasia or aplasia of nephrons that are often difficult to determine histologically but that give rise to thin kidneys and clubbed calices , dysplasia of nephrons and abnormal interstitial tissue and blood vessels , all of which are detected more readily on microscopic examination .
C0022646
kidneys
C0027713
nephrons