title: Determinants of urolithiasis in patients with intestinal fat malabsorption.
abstract: OBJECTIVE
  To investigate the determinants of urinary stone formation in patients with fat malabsorption, because, although the prevalence of urolithiasis is greater in patients with intestinal diseases, the pathogenetic mechanisms and risk factors associated with urolithiasis in this population remain partially unsolved.
  
  
  METHODS
  The present study retrospectively analyzed the determinants of urolithiasis in 51 patients with fat malabsorption due to different intestinal diseases. Anthropometric, clinical, blood, 24-hour urinary parameters, and dietary intake were assessed.
  
  
  RESULTS
  The resection rate (ie, pancreatic and/or bowel resection) differed significantly between stone formers (SF; n=10) and nonstone formers (NSF; n=41; 70% vs 29%; P=.027). Urinary citrate was lower (1.606±1.824 vs 3.156±1.968 mmol/24 h; P=.027), while oxalate excretion (0.659±0.292 vs 0.378±0.168 mmol/24 h; P=.002) and the relative supersaturation of calcium oxalate were greater in SF than NSF (8.16±4.61 vs 3.94±2.93; P=.003). Total cholesterol and low-density lipoprotein cholesterol, but also high-density lipoprotein cholesterol, plasma β-carotene, and vitamin E concentrations, were significantly diminished, whereas serum aspartate aminotransferase activity was significantly greater in SF compared with NSF. Binary logistic regression analysis revealed resection status as a major extrarenal risk factor for stone formation (odds ratio 5.639).
  
  
  CONCLUSIONS
  Increased urinary oxalate and decreased citrate excretion, probably resulting from pancreatic and/or bowel resection with mainly preserved colon, were identified as the most crucial urinary risk factors for stone formation in patients with fat malabsorption. The findings suggest that hyperoxaluria predominantly results from increased colonic permeability for oxalate due to disturbed bile acid metabolism. The impaired status of fat-soluble antioxidants β-carotene and vitamin E indicates severe malabsorptive states associated with an enhanced stone-forming propensity.
authors.affiliation: University Stone Centre, Department of Urology, University of Bonn, Bonn, Germany. Roswitha.Siener@ukb.uni-bonn.de
authors.forename: Roswitha
authors.initials: R
authors.lastname: Siener
authors.forename: Julia
authors.initials: J
authors.lastname: Petzold
authors.forename: Norman
authors.initials: N
authors.lastname: Bitterlich
authors.forename: Birgit
authors.initials: B
authors.lastname: Alteheld
authors.forename: Christine
authors.initials: C
authors.lastname: Metzner
mesh_terms: D000328:Adult; D000368:Aged; D001219:Aspartate Aminotransferases / Q000097:blood; D002129:Calcium Oxalate / Q000652:urine; D016022:Case-Control Studies; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood; D019343:Citric Acid / Q000652:urine; D003082:Colectomy / Q000009:adverse effects; D004041:Dietary Fats / Q000378:metabolism*; D005260:Female; D006801:Humans; D007082:Ileum / Q000601:surgery; D007408:Intestinal Absorption; D016015:Logistic Models; D008286:Malabsorption Syndromes / Q000150:complications* / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D019815:Oxalic Acid / Q000652:urine; D010180:Pancreatectomy / Q000009:adverse effects; D012189:Retrospective Studies; D012307:Risk Factors; D052878:Urolithiasis / Q000097:blood / Q000209:etiology* / Q000652:urine; D014810:Vitamin E / Q000097:blood; D055815:Young Adult; D019207:beta Carotene / Q000097:blood
chemical_list: D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D004041:Dietary Fats; D019207:beta Carotene; D014810:Vitamin E; D002129:Calcium Oxalate; D019343:Citric Acid; D019815:Oxalic Acid; D001219:Aspartate Aminotransferases