The report concerns a 23-year-old female with a left upper ureteral stone who had received left ureterolithotomy eight years previously but was still symptomatic. She received 1, 200 shock unmber of extracorporeal shock wave lithotripsy by Simens Lithostar in this hospital. The stone fragments was passed spontaneously after treatment, revealing grossly impacted suture material. The uneven surface of that material was found by scanning electron microscopy. Whewellite, weddellite and apatite were found around the knot. There was risk of encrustation by non-absorable suture material in this case.