The effect of patient position on intrarenal anatomy

Although flexible ureteroscopes are designed with mechanisms for active and passive tip deflection, one of the major problems is the not infrequent inability to enter the lower pole calices. Accordingly, we measured the change in the lower pole infundibulopelvic (LIP) angle when the patient's position was varied (i.e., prone, supine, head down) during intravenous urography (IVU).

The LIP angle was measured in 20 right and 26 left adult kidneys during an IVU with the patient in six different positions: supine level, supine 20 degrees head down, supine 45 degrees head up, prone level, prone 20 degrees head down, and prone 45 degrees head up. None of the patients had a history of renal surgery.

In all cases, the broadest angle of entry to the lower pole infundibulum was obtained with the patient in a prone position and 20 degrees head down.

The LIP angle broadens when the patient lies in a prone 20 degrees head down position. This maneuver could improve the surgeon's ability to access the lower pole calices when performing flexible ureteronephroscopy.