Percutaneous removal of caliceal and other "inaccessible" stones: instruments and techniques.

Percutaneous removal of renal stones is becoming an established procedure, especially for stones lying free in the renal pelvis. However, some renal stones, particularly caliceal stones, are less accessible and require special techniques for removal. We discuss these techniques, which include 1) retrograde pyelography to facilitate a thorough understanding of caliceal anatomy and stone position in 3 dimensions, 2) approaches for accurate placement of a nephrostomy tract for straight-line access to the stone(s), 3) judicious use of percutaneous punctures above the 12th rib and secondary percutaneous tracts, and 4) skilled choice and use of a large variety of cutting, extracting and disintegrating instruments with endoscopic and/or fluoroscopic control. The flexible nephroscope is valuable especially to reach inaccessible areas, although its skilled use requires experience. Flexible endoscopy often is aided by pressure irrigation, an assistant and simultaneous fluoroscopic control.