Part 1: Heterogeneity within bariatric surgery Part 2: Abdominal pain: the dark side of bariatric surgery

The DIABAR is an open, randomized controlled trial, performed in two hospitals in the Netherlands(chapter 3). The primary aim is to evaluate the glycemic control after laparoscopic Roux-en-Y gastric bypass and one-anastomosis gastric bypass in patients with severe obesity and type 2 diabetes mellitus with 10 years of follow-up. Furthermore, the DIABAR trial is designed to identify novel pathways in the pathogenesis of obesity and obesity related comorbidities via gut microbial, immunological, and metabolic markers. The hypothesis that men presenting for bariatric surgery are medically less healthy than women was tested in Chapter 4. Two cohorts of patients undergoing bariatric surgery and a control group of patients with severe obesity from a general population from the HELIUS study, were used. During intake, males had significantly higher rates of the most common obesity-associated medical problems: hypertension, type 2 diabetes, OSAS and dyslipidemia. Male patients used more medication in general, more often suffered from prediabetes, NIDDM and IDDM, had a higher HbA1c, a higher blood pressure. A systematic review on %TWL after laparoscopic Roux-en-Y gastric bypass and laparoscopic sleeve gastrectomy was performed(Chapter 5). The mean %TWL at one year after laparoscopic Roux-en-Y gastric bypass was 31.9%, and 28.1% after five years. During the first and fifth years of follow-up after laparoscopic sleeve gastrectomy, the mean %TWL was 29.5% and 27.0%, respectively. In chapter II, we conducted a systematic review on emergency department visits and readmissions more than 30 days after laparoscopic Roux-en-Y gastric bypass. 25.6%, 30.0% and 31.1% of patients at one, two and three years after surgery, had a emergency department visit. Number of readmissions varied: 9.4% in one year, 29.0% within 2 years and 23.9% in a study with a mean follow-up of 4.2 years after surgery. Main reasons were abdominal pain and abdominal pain of unknown origin. Chapter III focused on diagnoses for abdominal pain. Of 441 patients 212 were readmitted at least once during and 164 required surgery for the abdominal pain. At the end of the episode 20.0% of patients had a presumed diagnosis, 41.5% a definitive diagnosis and 38.5% of patients had unexplained complaints. The most common diagnoses were cholecystolithiasis, ulcers, internal herniation, irritable bowel syndrome, ACNES and constipation. Patients with IBS or a history of psychiatric diseases had a higher probability of unexplained complaints at the end of the episode. Chapter IV described all diagnostic tests and reoperations performed in the episodes of abdominal pain. 715 diagnostic tests were performed in 441 patients. At least one abdominal CT scan was performed in 67.1%, an ultrasound in 30.2%, and a gastroscopy in 20.9%. A possible explanation for the abdominal pain was found in 40.2% of all abdominal CT scans, 45.3% of ultrasounds, 34.7% of gastroscopies. Diagnostic laparoscopy was the most commonly performed surgery followed by the laparoscopic cholecystectomy. In Chapter V, a cross-sectional study is described to assess the clinical value of the PEI-Q in patients following bariatric surgery and the value of a fecal elastase test in patients with deviating PEI-Q scores. In only 11.9% of cases, the test indicated the presence of PEI. There was no correlation between fecal elastase levels and time after surgery(P=0,73), nor between fecal elastase levels and PEI-Q scores(AUC 0.59). In Chapter VI, the changes in the gut microbiome and their role in gastrointestinal complaints following bariatric surgery were investigated. Using machine learning, we identified several pre- and post-operative bacterial species, the abundance of which predicted postoperative GIQLI score. These bacteria may be associated with certain fermentative capacities or the production of either anti- or pro-inflammatory metabolites by the intestinal microbiota, and thus have a beneficial effect on gastrointestinal health.