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Re: Factors Related to Colonization With Oxalobacter Formigenes in U.S. Adults
UROLITHIASIS/ENDOUROLOGY
577
Fat Malabsorption and Increased Intestinal Oxalate Absorption are Common After Roux-En-Y Gastric Bypass Surgery R. Kumar, J. C. Lieske, M. L. Collazo-Clavell, M. G. Sarr, E. R. Olson, T. J. Vrtiska, E. J. Bergstralh and X. Li Nephrology and Hypertension Research Unit, Division of Nephrology; Division of Endocrinology, Metabolism and Nutrition; Department of Internal Medicine; and Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota Surgery 2011; Epub ahead of print.
Background: Hyperoxaluria and increased calcium oxalate stone formation occur after Roux-en-Y gastric bypass (RYGB) surgery for morbid obesity. The etiology of this hyperoxaluria is unknown. We hypothesized that after bariatric surgery, intestinal hyperabsorption of oxalate contributes to increases in plasma oxalate and urinary calcium oxalate supersaturation. Methods: We prospectively examined oxalate metabolism in 11 morbidly obese subjects before and 6 and 12 months after RYGB (n ⫽ 9) and biliopancreatic diversion-duodenal switch (BPD-DS) (n ⫽ 2). We measured 24-hour urinary supersaturations for calcium oxalate, apatite, brushite, uric acid, and sodium urate; fasting plasma oxalate; 72-hour fecal fat; and increases in urine oxalate following an oral oxalate load. Results: Six and 12 months after RYGB, plasma oxalate and urine calcium oxalate supersaturation increased significantly compared with similar measurements obtained before surgery (all P ⱕ .02). Fecal fat excretion at 6 and 12 months was increased (P ⫽ .026 and .055, 0 vs 6 and 12 months). An increase in urine oxalate excretion after an oral dose of oxalate was observed at 6 and 12 months (all P ⱕ .02). Therefore, after bariatric surgery, increases in fecal fat excretion, urinary oxalate excretion after an oral oxalate load, plasma oxalate, and urinary calcium oxalate supersaturation values were observed. Conclusion: Enteric hyperoxaluria is often present in patients after the operations of RYGB and BPD-DS that utilize an element of intestinal malabsorption as a mechanism for weight loss. Editorial Comment: It is now well documented that patients undergoing certain types of bariatric surgery, such as Roux-en-Y gastric bypass and biliary-pancreatic duodenal switch, are at risk for kidney stones postoperatively. This finding is thought to be due to hyperoxaluria, which typically manifests 6 months after the procedure. This study suggests that the increased oxalate excretion is due to augmented gastrointestinal oxalate uptake linked to fat malabsorption. These patients should limit their intake of oxalate and fat, and increase their consumption of dairy products with meals. Calcium supplements are also used to reduce oxalate excretion. Calcium citrate is recommended, as some of these patients may also have diminished oxalate excretion. There is some evidence that probiotic therapy may also reduce oxalate excretion. Dean Assimos, M.D.
Re:: Factors Related to Colonization With Oxalobacter Formigenes in U.S. Adults J. P. Kelly, G. C. Curhan, D. R. Cave, T. E. Anderson and D. W. Kaufman Slone Epidemiology Center, Boston University, Boston, Massachusetts J Endourol 2011; 25: 673– 679.
Goals: To elucidate the determinants of Oxalobacter formigenes colonization in humans. Background: O. formigenes is a gram-negative anaerobic bacterium that colonizes the colon of a substantial proportion of the normal population and metabolizes dietary and endogenous oxalate. The bacterium has been associated with a large reduction in the odds of recurrent calcium oxalate kidney stones. Subjects were 240 healthy individuals from Massachusetts and North Carolina. O. formigenes was detected by culture of fecal swabs. Information on factors of interest was obtained by telephone interviews and self-administered questionnaires. Study Results: The overall prevalence of O. formigenes was 38%. Use of specific antibiotics previously thought to affect the bacterium was significantly related to colonization, with prevalences of 17%, 27%, and 36%, for those who had used these drugs
578
UROLITHIASIS/ENDOUROLOGY
⬍1, 1–5, and ⬎5 years ago, compared with 55% in nonusers. There were no significant associations with demographic factors, nutrient intake, or medical history, although the prevalence appeared to increase somewhat with increasing oxalate consumption. Conclusions: Some antibiotics markedly affect colonization with O. formigenes. Although no other factor was identified as having a material influence on the prevalence of the bacterium, there is much to learn about how an individual acquires the organism and which factors affect persistence of colonization. Editorial Comment: Colonization with this bacterium has been demonstrated to reduce the risk of calcium oxalate kidney stones. Its main carbon source is oxalate. The authors showed that colonization can be impacted by antibiotic therapy. They analyzed the impact of antibiotic sensitivity. However, analysis was done for only 1 strain of this bacterium (HC1). More information is needed on the antibiotic sensitivities of other strains found in humans. The positive relationship between oxalate consumption and colonization is of interest. Perhaps a certain level of oxalate consumption is required to maintain this bacterium in the fecal microbiome. Dean Assimos, M.D.
577
Fat Malabsorption and Increased Intestinal Oxalate Absorption are Common After Roux-En-Y Gastric Bypass Surgery R. Kumar, J. C. Lieske, M. L. Collazo-Clavell, M. G. Sarr, E. R. Olson, T. J. Vrtiska, E. J. Bergstralh and X. Li Nephrology and Hypertension Research Unit, Division of Nephrology; Division of Endocrinology, Metabolism and Nutrition; Department of Internal Medicine; and Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota Surgery 2011; Epub ahead of print.
Background: Hyperoxaluria and increased calcium oxalate stone formation occur after Roux-en-Y gastric bypass (RYGB) surgery for morbid obesity. The etiology of this hyperoxaluria is unknown. We hypothesized that after bariatric surgery, intestinal hyperabsorption of oxalate contributes to increases in plasma oxalate and urinary calcium oxalate supersaturation. Methods: We prospectively examined oxalate metabolism in 11 morbidly obese subjects before and 6 and 12 months after RYGB (n ⫽ 9) and biliopancreatic diversion-duodenal switch (BPD-DS) (n ⫽ 2). We measured 24-hour urinary supersaturations for calcium oxalate, apatite, brushite, uric acid, and sodium urate; fasting plasma oxalate; 72-hour fecal fat; and increases in urine oxalate following an oral oxalate load. Results: Six and 12 months after RYGB, plasma oxalate and urine calcium oxalate supersaturation increased significantly compared with similar measurements obtained before surgery (all P ⱕ .02). Fecal fat excretion at 6 and 12 months was increased (P ⫽ .026 and .055, 0 vs 6 and 12 months). An increase in urine oxalate excretion after an oral dose of oxalate was observed at 6 and 12 months (all P ⱕ .02). Therefore, after bariatric surgery, increases in fecal fat excretion, urinary oxalate excretion after an oral oxalate load, plasma oxalate, and urinary calcium oxalate supersaturation values were observed. Conclusion: Enteric hyperoxaluria is often present in patients after the operations of RYGB and BPD-DS that utilize an element of intestinal malabsorption as a mechanism for weight loss. Editorial Comment: It is now well documented that patients undergoing certain types of bariatric surgery, such as Roux-en-Y gastric bypass and biliary-pancreatic duodenal switch, are at risk for kidney stones postoperatively. This finding is thought to be due to hyperoxaluria, which typically manifests 6 months after the procedure. This study suggests that the increased oxalate excretion is due to augmented gastrointestinal oxalate uptake linked to fat malabsorption. These patients should limit their intake of oxalate and fat, and increase their consumption of dairy products with meals. Calcium supplements are also used to reduce oxalate excretion. Calcium citrate is recommended, as some of these patients may also have diminished oxalate excretion. There is some evidence that probiotic therapy may also reduce oxalate excretion. Dean Assimos, M.D.
Re:: Factors Related to Colonization With Oxalobacter Formigenes in U.S. Adults J. P. Kelly, G. C. Curhan, D. R. Cave, T. E. Anderson and D. W. Kaufman Slone Epidemiology Center, Boston University, Boston, Massachusetts J Endourol 2011; 25: 673– 679.
Goals: To elucidate the determinants of Oxalobacter formigenes colonization in humans. Background: O. formigenes is a gram-negative anaerobic bacterium that colonizes the colon of a substantial proportion of the normal population and metabolizes dietary and endogenous oxalate. The bacterium has been associated with a large reduction in the odds of recurrent calcium oxalate kidney stones. Subjects were 240 healthy individuals from Massachusetts and North Carolina. O. formigenes was detected by culture of fecal swabs. Information on factors of interest was obtained by telephone interviews and self-administered questionnaires. Study Results: The overall prevalence of O. formigenes was 38%. Use of specific antibiotics previously thought to affect the bacterium was significantly related to colonization, with prevalences of 17%, 27%, and 36%, for those who had used these drugs
578
UROLITHIASIS/ENDOUROLOGY
⬍1, 1–5, and ⬎5 years ago, compared with 55% in nonusers. There were no significant associations with demographic factors, nutrient intake, or medical history, although the prevalence appeared to increase somewhat with increasing oxalate consumption. Conclusions: Some antibiotics markedly affect colonization with O. formigenes. Although no other factor was identified as having a material influence on the prevalence of the bacterium, there is much to learn about how an individual acquires the organism and which factors affect persistence of colonization. Editorial Comment: Colonization with this bacterium has been demonstrated to reduce the risk of calcium oxalate kidney stones. Its main carbon source is oxalate. The authors showed that colonization can be impacted by antibiotic therapy. They analyzed the impact of antibiotic sensitivity. However, analysis was done for only 1 strain of this bacterium (HC1). More information is needed on the antibiotic sensitivities of other strains found in humans. The positive relationship between oxalate consumption and colonization is of interest. Perhaps a certain level of oxalate consumption is required to maintain this bacterium in the fecal microbiome. Dean Assimos, M.D.