title: Fibrous coagulum: a new cause of retained fragments following extracorporeal shock wave lithotripsy.
abstract: OBJECTIVE
  A previously unrecognized cause of retained fragments following extracorporeal shock wave therapy is identified.
  
  
  METHODS
  Nine patients referred for percutaneous stone extraction following failure of multiple shock wave lithotripsy treatments had retained fragments embedded in soft tissue. The stones were evaluated by chemical analysis and the tissue was evaluated histologically.
  
  
  RESULTS
  All stones contained calcium and histopathology confirmed the presence of fibrous tissue. Radiographs were unable to predict the presence of the substance preoperatively.
  
  
  CONCLUSIONS
  We identified fibrous coagulum as a cause of retained fragments following shock wave lithotripsy. The material is soft tissue and cannot be ablated by further shock wave lithotripsy. These findings confirm that repeated shock wave lithotripsy is contraindicated, since stone fragmentation and passage may be inhibited by fibrous coagulum.
mesh_terms: D001777:Blood Coagulation; D005260:Female; D005355:Fibrosis / Q000150:complications; D006801:Humans; D008096:Lithotripsy / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000209:etiology