title: Risk of nephrolithiasis, hyperoxaluria, and calcium oxalate supersaturation increased after Roux-en-Y gastric bypass surgery: a systematic review and meta-analysis.
abstract: BACKGROUND
  Earlier publications have shown renal stone complications after bariatric surgery. Multiple reports have also linked metabolic changes that alter the urinary chemistry profiles, especially hyperoxaluria, after bariatric surgery. However, evidence on change of other urine chemistry studies and type of bariatric surgery and risk of stone has been inconclusive so far.
  
  
  OBJECTIVE
  To explore the association between bariatric surgery and postoperative urinary chemistry change and risk of stone formation SETTING: A systematic review and meta-analysis.
  
  
  METHODS
  We comprehensively searched the databases of MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials (CENTRAL) from their dates of inception to January 2016. The inclusion criteria were published studies of association between bariatric surgery and postoperative renal stone formation or urine chemistry profiles. We used random-effects model meta-analysis and calculated the pooled risk of renal stone and difference in 24-hour urine chemistry profiles.
  
  
  RESULTS
  Twelve observational studies were included in the meta-analysis. There was significantly higher risk of stone formation after Roux-en-Y gastric bypass surgery with pooled relative risk = 1.79 (95% CI: 1.54-2.10). In the analysis of urine chemistry profiles, there was significantly higher calcium oxalate supersaturation, lower citrate, and lower volume postoperatively compared with preoperatively. There was also higher urine oxalate in patients who had bariatric surgery compared with nonsurgery controls.
  
  
  CONCLUSIONS
  Roux-en-Y gastric bypass surgery is associated with higher risk of renal stone and increased urine oxalate and calcium oxalate supersaturation.
authors.affiliation: Department of Internal Medicine, Bassett Medical Center and Columbia University College of Physicians and Surgeons, Cooperstown, New York; Department of Preventive and Social Medicine, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Sikarin
authors.initials: S
authors.lastname: Upala
authors.affiliation: Department of Internal Medicine, University of Hawaii, Honolulu, Hawaii; Department of Internal Medicine, King Chulalongkorn Memorial Hospital, Bangkok, Thailand.
authors.forename: Veeravich
authors.initials: V
authors.lastname: Jaruvongvanich
authors.affiliation: Department of Internal Medicine, Bassett Medical Center and Columbia University College of Physicians and Surgeons, Cooperstown, New York; Department of Preventive and Social Medicine, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand. Electronic address: anawin.sanguankeo@bassett.org.
authors.forename: Anawin
authors.initials: A
authors.lastname: Sanguankeo
mesh_terms: D002129:Calcium Oxalate / Q000652:urine*; D018849:Controlled Clinical Trials as Topic; D005260:Female; D015390:Gastric Bypass / Q000009:adverse effects*; D006801:Humans; D006959:Hyperoxaluria / Q000209:etiology* / Q000652:urine; D007669:Kidney Calculi / Q000209:etiology* / Q000652:urine; D008297:Male; D009765:Obesity / Q000601:surgery / Q000652:urine; D064887:Observational Studies as Topic; D011183:Postoperative Complications / Q000209:etiology; D012307:Risk Factors
chemical_list: D002129:Calcium Oxalate
keywords: Bariatric surgery; Calcium oxalate; Nephrolithiasis; Renal stone; Urine chemistry