Branched calculi: shapes and operative approaches.

Branched calculi (infection stones) typically arise in intrarenal pelves. They expand to touch the pelvic wall and then grow peripherally, keeping contact with the walls of the pelvis and greater than or equal to 1 infundibula. Filling the infundibulum obstructs the calix and allows terminal expansion of the stone. From study of a series of stones such a sequence might be reconstructed. The shape of the calculus and collecting structures was traced and classified from excretory urograms of 50 consecutive renal units. The funnel pelvis, usually intrarenal, contained a stone either extending into the ureteropelvic junction (24 cases) or stopping short of it (9 cases). Pelvic or infundibular and caliceal dilatation around the stone was found in the remaining 8 and 9 cases, respectively. These patterns of growth of branched calculi directly bear on the approaches and technique for the operative removal. Because typical branched calculi arise in the intrarenal pelvis a high transverse intrahilar incision is necessary. Less intrahilar dissection is needed for cases in which the pelvis is dilated above and around the stone. Counter-incisions through the parenchyma or anatrophic nephrolithotomy is reserved for those patients with infundibular obstruction and resulting expanded caliceal stones.