title: Contribution of stone size to chronic kidney disease in kidney stone formers.
abstract: OBJECTIVE
  To determine whether stone burden correlates with the degree of chronic kidney disease in kidney stone formers.
  
  
  METHODS
  A total of 97 extracorporeal shockwave lithotripsy candidates aged 18 years and older were included. Size, number and location of the kidney stones, along with cumulative stone size, defined as the sum of diameters of all stones) were determined. Estimated glomerular filtration rate was determined using the Chronic Kidney Disease Epidemiology Collaboration cystatin C/creatinine equation, and chronic kidney disease was defined as estimated glomerular filtration rate <60 mL/min/1.73 m(2).
  
  
  RESULTS
  In individuals with cumulative stone size <20 mm, estimated glomerular filtration rate significantly decreased when moving from the first (estimated glomerular filtration rate 75.5 ± 17.8 mL/min/1.73 m(2)) to the fourth (estimated glomerular filtration rate 56.4 ± 20.44 mL/min/1.73 m(2) ) quartile (P = 0.004). When patients with a cumulative stone size ≥ 20 mm were included, the observed association was rendered non-significant. In individuals with a cumulative stone size < 20 mm, each 1-mm increase in cumulative stone size was associated with a 20% increased risk of having chronic kidney disease. The relationship persisted even after adjustment for age, sex, body mass index, C-reactive protein, fasting plasma glucose, thyroid stimulating hormone, presence of microalbuminuria, history of renal calculi, history of extracorporeal shockwave lithotripsy, number and location of the stones (odds ratio 1.24, 95% confidence interval 1.02-1.52). The same was not observed for individuals with a cumulative stone size ≥ 20 mm.
  
  
  CONCLUSIONS
  In kidney stone formers with a cumulative stone size up to 20 mm, estimated glomerular filtration rate linearly declines with increasing cumulative stone size. Additionally, cumulative stone size is an independent predictor of chronic kidney disease in this group of patients.
authors.affiliation: Nephrology Research Center, Imam Khomeni Hospital, Tehran, Iran.
authors.forename: Farrokhlagha
authors.initials: F
authors.lastname: Ahmadi
authors.forename: Samira Motedayen
authors.initials: SM
authors.lastname: Etemadi
authors.forename: Mahbob
authors.initials: M
authors.lastname: Lessan-Pezeshki
authors.forename: Mitra
authors.initials: M
authors.lastname: Mahdavi-Mazdeh
authors.forename: Mohsen
authors.initials: M
authors.lastname: Ayati
authors.forename: Alireza
authors.initials: A
authors.lastname: Mir
authors.forename: Hadi Rokni
authors.initials: HR
authors.lastname: Yazdi
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007668:Kidney / Q000503:physiopathology*; D007669:Kidney Calculi / Q000150:complications* / Q000453:epidemiology / Q000628:therapy; D008096:Lithotripsy; D008297:Male; D008875:Middle Aged; D051436:Renal Insufficiency, Chronic / Q000209:etiology*; D012307:Risk Factors
keywords: chronic kidney disease; cystatin C; estimated glomerular filtration rate; kidney stone; stone size