title: Sir William Osler's perceptions of urolithiasis and the case of the indigo calculus.
abstract: BACKGROUND
  Sir William Osler published his textbook, The Principles and Practice of Medicine, in 1892. It became the definitive treatise on a wide variety of diseases. The section on nephrolithiasis clearly presents the etiology, pathology, symptoms, diagnosis, and treatments. What remains a mystery is the mention, under rare forms of human stones, of a type called "indigo."
  
  
  METHODS
  A search of Index Medicus starting from 1909 backward to its inception in 1879 was performed for key words "indigo," "calculus," "renal" or "bladder stones" and "indicanuria." Twelve textbooks of urology published before 1940 were scrutinized for references to indigo calculi.
  
  
  RESULTS
  Only two references to indigo were found, both related to its use for treating constipation (1887 and 1891). Of the 12 textbooks, only 4 make passing reference to "indigo stones." They all mention that such calculi are very rare, but direct references to cases are lacking. One textbook references a study of blue stones from Egyptian mummies.
  
  
  CONCLUSIONS
  It is unlikely that Osler's reference to an indigo calculus was taken lightly during his writing of The Principles and Practice of Medicine. The case of the indigo calculus is fascinating and perhaps enlightening if only for the source of Osler's intrigue.
authors.affiliation: Capital District Urologic Surgeons, Albany, New York 12208, USA. memoran2@juno.com
authors.forename: Michael E
authors.initials: ME
authors.lastname: Moran
authors.forename: Sakti
authors.initials: S
authors.lastname: Das
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Rosenberg
mesh_terms: D049672:History, 19th Century; D049673:History, 20th Century; D006801:Humans; D007200:Indican / Q000266:history / Q000652:urine; D007203:Indigo Carmine; D007211:Indoles / Q000266:history*; D007669:Kidney Calculi / Q000266:history* / Q000473:pathology; D010860:Pigments, Biological / Q000266:history*; D001744:Urinary Bladder Calculi / Q000266:history* / Q000473:pathology
chemical_list: D007211:Indoles; D010860:Pigments, Biological; D007203:Indigo Carmine; D007200:Indican