Difficult Renal Stones
Stones to Fragment
2% of renal calculi are refractory to SWL therapy. Factors influencing
fragmentation include stone size, composition, radio-opacity, patient
weight, and anatomy. The fragility of renal stones in increasing
order is struvite, calcium apatite, uric acid, calcium oxalate dihydrate,
calcium oxalate monohydrate and cystine. There is poor fragmentation
of calcium oxalate monohydrate (whellelite) and cystine stones by
ESWL. PNL is used to treat these difficult stones. Alternatively,
the Ho:YAG laser has been successful in treating smaller renal stones
via flexible ureteropyeloscopy.
JE. Extracorporeal shock wave lithotripsy: Development, instrumentation,
and current status. Urol Clin North Am 1997, 24:1:185-211.
HH, Lee JH, Park MS, Lee SE, Kim SW. In situ extracorporeal shockwave
lithotripsy for ureteral calculi: Investigation of factors influencing
stone fragmentation and appropriate number of sessions for changing
treatment modality. J Endourol 1996, 10: 6: 501-505.