Does further extracorporeal lithotripsy promote clearance of small residual fragments?

Small persistent fragments (less than or equal to 4 mm) following extracorporeal shock wave lithotripsy have been termed clinically insignificant residual fragments (CIRF), but their presence may be associated with an increased rate of development of recurrent symptomatic renal calculi. We have adopted a policy of further extracorporeal piezoelectric shock wave lithotripsy (EPL) for patients with CIRF in an attempt to promote complete clearance. A series of 22 patients with a mean initial stone burden of 16 mm (range 7-48) developed CIRF after a median of 2 EPL treatment sessions (range 1-9). CIRF were in the lower calices (n = 20), middle calices (n = 1) and upper calices (n = 1). These calices were normal (n = 6), slightly dilated (n = 9), moderately dilated (n = 2) or grossly dilated (n = 5). After 6 to 14 months, patients underwent a further session of EPL. One month later, 3 patients with normal calices showed a considerable reduction in CIRF, but all other patients showed no change. When CIRF form in normal calices a further session of EPL may promote clearance. However, when calices containing CIRF are significantly dilated, further EPL is of no value.