The study aims to explore patients perception of chronic abdominal pain after Roux en Y gastric bypass surgery for morbid obesity. The investigators aim to describe characteristics of symptoms of pain. Potential risk factors for developing abdominal pain post gastric bypass will be explored.

This is a single-center, prospective, longitudinal, cohort study performed at the Department of Morbid Obesity and Bariatric Surgery, Oslo University Hospital. Patients undergoing gastric bypass are eligible for inclusion. The study is approved by the Regional Committee for Medical and Health Research Ethics (no.2013/1263), South-East health region. All participants provide written consent for study paennrollment.

The participants are asked to fill inn a set of questionnaires before and during follow-up after gastric bypass surgery. Symptom characteristics are explored and evaluated. Quality of life is included in the analyses. The main outcome is findings at 2 years post surgery, but the patients will be followed for 5 years.

The investigators also aim to evaluate by objective measures the patients perception of pain by temperature and skin pressure stimulants before and after surgery (2 years).

Inclusion Criteria:

• Indication for gastric bypass surgery i.e. BMI > 40 kg/m2 or BMI > 35 kg/m2 and obesity related comorbidity following failed attempts of sustained weight loss

Exclusion Criteria:

• Other indications for gastric bypass surgery than obesity
• Previous bariatric surgery
• Other concomitant surgical procedures for abdominal pain such as cholecystectomy

Patients planned for bariatric surgery (gastric bypass) at a single center