Routine liver function tests and serum amylase determinations after biliary lithotripsy: are they necessary?

Shock-wave-induced soft-tissue damage after biliary extracorporeal shock-wave lithotripsy (BESWL) has been reported. Every patient treated in Vancouver has, therefore, had liver function tests and serum amylase levels measured before and within 6 days after BESWL. All patients had symptomatic cholecystolithiasis with normal pre-BESWL biochemistry. Analysis of 311 patients after treatment with the Siemens Lithostar unit showed elevation of one or more laboratory value in 19% (60/311). Serum aspartate transaminase level was most frequently abnormal (38 cases). The majority of abnormalities were mild, less than two times normal levels. Clinically significant complications occurred in five patients (three pancreatitis, one cholecystitis, one common bile duct obstruction); four of these occurred 1 week or more after treatment. The results of routine laboratory tests could not be used to predict complications. No correlation was seen between abnormal values and number of shock waves administered or peak shock-wave pressure. Of 112 patients surveyed at the time of post-BESWL enzyme measurement, 49 (44%) reported a degree of pain, which was severe in eight cases. Presence of severe pain correlated strongly (p less than .001) with abnormal laboratory findings, however not with the degree of abnormality. As results of these laboratory tests are nonspecific, have not been shown to correlate with the degree of severity of BESWL-induced tissue damage, and do not predict complications, the tests are of little value in the absence of clinical signs and symptoms. These conclusions, however, apply only to the Siemens Lithostar Plus with patients treated in the steep left posterior oblique position. Cost savings can be expected if routine post-BESWL biochemical tests are abandoned.