Surgery News - September 2007 - (Page 9) SEPTEMBER 2007 • SURGERY NEWS POSTOP MANAGEMENT 9 Stone Formation Starts Soon After Bariatric Surgery B Y B E T S Y B AT E S Else vier Global Medical Ne ws A N A H E I M , C A L I F. — Urinary metabolic changes and kidney stone formation may occur sooner after bariatric surgery than previously believed, according to studies presented at the annual meeting of the American Urological Association. Researchers found that most patients presenting to the University of Minnesota’s bariatric surgery program had low urinary volumes and significant abnormalities in urinary metabolism before surgery. By 3 months after surgery, 100% of the patients had low urinary volumes and their urine showed a significant increase in mean relative supersaturation for calcium oxylate and uric acid. A “dramatic” increase in the concentration of urinary oxylate soon after surgery posed a significant risk of kidney stones in some patients, reported Dr. Manoj Monga, director of endourology and stone disease at the Minneapolis medical center, and an ACS Fellow. A separate study from Duke University in Durham, N.C., supported the hypothesis that the early postoperative period may be important in stone formation risk. That study of 1,780 patients who underwent the Roux-en-Y gastric bypass procedure between 1999 and 2006 found that the 56 who developed kidney stones tended to be male patients and those with rapid early weight loss. The mean time from surgery to stone formation was 6.3 months, said Dr. Marnie R. Robinson, senior resident in the Duke department of urology. Previous studies from the Mayo Clinic, Rochester, Minn., and other sites focused on kidney stone formation from 1 to 3 years after bariatric surgery. The University of Minnesota study was unique in performing prospective comprehensive urinary studies, including 24hour urine collection and intake logs prior to surgery and postoperatively. Among 45 patients who presented to the bariatric clinic, 42 had a body mass index of 40 kg/m2 or greater. The mean age of all patients was 47 years. At baseline, nearly three-fourths had low urinary volumes (less than 2 L), nearly a third had high urinary sodium, and most had low urinary pH, high urinary calcium, and high uric acid. The urine of a majority of patients was supersaturated for sodium urate and uric acid, and that of nearly 30% was supersaturated for calcium oxylate. At the time of the meeting, Dr. Monga and his associates had collected comprehensive 3month data on 23 of the 45 patients, all of whom had undergone a Roux-en-Y procedure. The levels of urinary calcium, urinary sodium, and uric acid had declined, while urinary oxylate had risen. Urinary pH and urinary citrate were unchanged. The proportions of patients with low magnesium levels, low urinary citrate levels, or hyperoxaluria all increased significantly. “The mean relative supersaturation increased significantly for calcium oxylate and uric acid at only 3 months’ follow-up,” Dr. Monga said. He noted that patients’ caloric intake declined and their diets postoperatively contained less sodium, less protein, and less calcium. Letters were sent to the participants informing them of the findings and offering evaluations to detect potential kidney stones. Five came for a follow-up visit, but only one agreed to a CT scan for stone evaluation. The Duke study points to a potential profile of patients at elevated risk. Stone formers in that study were similar to those who did not form stones before surgery with respect to BMI, percentage of body water, lean body mass, and percentage of body fat. But after surgery, their mean BMI was significantly lower than that of those patients who did not form stones both 3 and 6 months postoperatively. They had lost 46% of their excess weight at 3 months and 58% by 6 months, compared with those who did not form stones, who had lost 35% and 52% by 3 and 6 months, respectively. It is unlikely that dehydration was key to stone formation, since total percentage of body water was higher among stone formers at every time point, significantly so at 3 and 6 months. Dr. Robinson noted that preexisting stones could not be ruled out; however, only 3 of the 56 stone formers had a history of nephrolithiasis. Both presenters called for more research into risk factors for stone formation and potential preventive measures in bariatric surgery patients. ■ INFORMATION FOR SOUND DECISION MAKING Clinical Summary EVIDENCEBASED BIOLOGIC TISSUE REPAIR Acellular Porcine Dermal Graft in 16 Complex Incisional Hernia Repairs Gallagher H. European Council of Coloproctology/European Association of Coloproctology Joint Meeting, 2005. Introduction This study explored the use of porcine dermal graft in the management of complex, large incisional hernia repairs. Large incisional hernias are a major problem in 3% to 15% of laparotomies; 50% to 70% of primary suture repairs fail. Mesh repair has reduced recurrence to 3% to 28% but is associated with a range of complications including fistulation, bowel obstruction, recurrence and infection. Patients Sixteen patients (8 male, 8 female) underwent incisional hernia repair. Twelve of the 16 previously failed mesh repairs, 2 failed primary suture repair, 1 failed skin grafting to a laparostomy and 1 had fecal peritonitis. Methods Patients were followed for 30 months. All were operated on by the same doctor. Results There has been no symptomatic incisional hernia recurrence within the cohort, although one patient developed a small, lateral asymptomatic incisional hernia following ileostomy reversal. There was one mortality after pulmonary embolism despite prophylaxis. One oblique muscle tear required surgery 18 hours post-op with further Permacol® insertion making an excellent recovery. Three of 16 developed superficial dehiscence in the early post-op phase requiring VACS application. One patient developed an indolent MRSA abscess drained 11 months post-op. All 16 wounds healed fully, including five MRSA patients. Conclusions Complex and demanding incisional hernia including post-mesh failure can be successfully repaired with Permacol® with an acceptable morbidity and mortality profile. Experience a Better Biologic — call (800) 394-0417 or visit www.tissuescience.com ©2007 Tissue Science Laboratories, Inc. Printed in the U.S.A. Permacol is a registered trademark of Tissue Science Laboratories, plc. Please consult product labels and inserts for any indications, contraindications, hazards, warnings, cautions and directions for use. TSL 280 Rev http://www.tissuescience.com http://www.tissuescience.com
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