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The number of operations for morbid obesity is rising fast. We have examined aspects of postoperative physiology and results after bariatric surgery.

The pH in the proximal pouch after Roux-en-Y gastric bypass (RYGBP) was investigated with catheter-based and wire-less technique. Gastric emptying, PYY-levels in the fasting state and after a standardized meal was evaluated after biliopancreatic diversion with duodenal switch (DS). A clinical trial was undertaken, comparing DS to RYGBP in patients with BMI>48. Main outcome variables were safety and long-term weight results as well as abdominal symptoms and laboratory results.

Patients with stomal ulcer had significantly lower pH in their proximal gastric pouch as compared to asymptomatic control subjects. Long-time pH measurements with the wire-less BRAVO-system were feasible and demonstrated pH<4 in median 10.5% of the time in asymptomatic post-RYGBP patients. After DS, the T₅₀ of gastric emptying was 28±16 minutes. PYY-levels were higher after DS than in age-matched control subjects. BMI-reduction was greater after DS (24 BMI-units) than after RYGBP (17 BMI-units) in median 3.5 (2.0-5.3) years after surgery (p<0.001). Fasting glucose and HbA1c levels were lower one and three years after DS as compared to RYGBP. On the other hand, DS-patients reported having more diarrhea and malodorous flatus.

This thesis has resulted in deepened knowledge. Acid produced in the proximal pouch is an important pathogenetic factor in the development of stomal ulcer after RYGBP. However, symptom-free patients have an acidic environment in the proximal Roux-limb as well. After DS, gastric emptying is fast, but not instantaneous, and PYY-levels are high. DS results in superior weight reduction and better glucose control as compared to RYGBP in patients with BMI>48. We believe that DS has a place in surgical treatment of the super-obese, even though symptoms of diarrhea and malodorous flatus are more common after DS.