Caveat emptor: caliceal stones and the missing calix.

The failure of a stone-containing calix to visualize on an imaging study (that is a missing calix) is often the initial and only sign of an associated pyocalix, since the patient may present without fever and with sterile urine. Extracorporeal shock wave lithotripsy (ESWL*) in these patients may lead to life-threatening systemic sepsis. Therefore, the treatment of choice for the stone-laden missing calix is percutaneous drainage of the affected calix followed by percutaneous stone removal and, when necessary, an endoinfundibulotomy to reestablish communication between the obstructed calix and the renal pelvis.