Role of the renal collecting system in initial kidney stone formation.

Abstract

The anatomic site where the initial kidney stone grows to a clinically significant size is unknown. We studied human forniceal anatomy by microdissection and correlated the anatomic findings with the clinical presentation of kidney stones. In addition, we examined crystal attachment sites within the collecting system by direct infusion of calcium oxalate crystals into the renal pelvis of rabbits. Secondary urinary dead spaces were found in the fornices of compound papillae only, which were located at the poles of the kidneys. This feature correlated with a higher incidence of stones in these areas at the time of lithotripsy. Calcium oxalate crystals tended not to attach to either the renal papilla nor the pelvic sidewall unless these epithelia were previously injured with hydrochloric acid. The renal collecting system may serve as an anatomic site for crystal retention and growth but is unlikely to be the principal site for crystal attachment, unless prior cellular injury occurs.