Definitions
Bariatric surgery is understood to mean those surgical procedures which, through sustained weight loss, aim to improve and prevent associated comorbidities and enhance the quality of life. If the primary objective of surgical procedures is to improve metabolic glycemia in the presence of T2DM, the term metabolic surgery is used.
The WHO classification of obesity is based on the body mass index (BMI): Body weight divided by height squared (kg/m²). For Europeans obesity is classified as:
- Grade I (BMI 30–34.9 kg/m²)
- Grade II (BMI 35–39.9 kg/m²)
- Grade III (≥ 40 kg/m²)
The underlying cause of obesity is multifactorial; ultimately, a positive energy balance will result in storage of excess energy, mainly in the fatty tissues and liver. Weight loss is accompanied by decreased insulin resistance and improvements in blood glucose and lipids; blood pressure; gastroesophageal reflux; urinary incontinence; osteoarthritis; spinal complaints; intertrigo; infertility; obstructive sleep apnea syndrome; asthma; as well as a risk reduction in certain cancers.
Indications for bariatric/metabolic surgery
While sustained weight loss aimed at improving comorbidities and quality of life can be achieved in high-grade obesity through diet; exercise; and behavioral and drug-based therapies, alone or in combination, this is often not realized.[1-4] Compared with conventional weight loss measures, alone or in combination, surgery is much more effective and generally achieves the desired outcome.[5-12]
Bariatric surgical procedures are indicated under the following conditions:[13-16]
1. BMI ≥ 40 kg/m² without comorbidities and contraindications after failure of nonsurgical management.
2. BMI ≥ 35 kg/m² with one or more obesity-associated comorbidities such as T2DM; coronary artery disease; heart failure; hyperlipidemia; arterial hypertension; nephropathy; obstructive sleep apnea syndrome; obesity hypoventilation syndrome; Pickwick syndrome; nonalcoholic fatty liver or nonalcoholic fatty liver hepatitis; gastroesophageal reflux disease; asthma; chronic venous insufficiency; urinary incontinence; immobilizing joint disease; fertility limitations; or polycystic ovary syndrome.
3. Primary indication for bariatric surgery without prior nonsurgical management attempt, if one of the following conditions is met:
- BMI ≥ 50 kg/m²
- A non-surgical treatment attempt is deemed unpromising or futile by the multispecialty team.
- In patients with particularly severe concomitant and secondary diseases that do not allow postponement of surgery.
Primary indication for metabolic surgery is possible in the presence of BMI ≥ 40 kg/m² and coexisting T2DM if the treatment goal is more to improve the glycemic metabolic state rather than to achieve weight loss. These patients do not require evidence of exhaustive nonsurgical treatment to establish the indication for bariatric surgery. [17, American Diabetes Association 2017]
Contraindications for bariatric/metabolic surgery
Despite the current lack of evidence, bariatric or metabolic surgery is contraindicated in the following diseases and disorders:
1. Unstable mental conditions, untreated bulimia nervosa, active substance abuse.
2. Consuming underlying disease; malignant neoplasms; untreated endocrine causes; chronic diseases exacerbated by postoperative catabolic metabolism.
3. Pregnancy present or planned for the immediate future.
If the above diseases and disorders can be successfully treated, the situation should be reevaluated.
The following are not contraindications:
- Advanced age (≥65 years) [18]
- Chronic inflammatory bowel disease, e.g., Crohn disease and ulcerative colitis [19]
- Family planning not yet completed [20]
- Type 1 diabetes mellitus (T1DM) [21]
Surgical procedures
The most effective surgical procedures in management of obesity and its comorbidities include:
- Sleeve gastrectomy (SG)
- Proximal Roux-en-Y gastric bypass (pRYGB)
- Omega-loop gastric bypass (OLGB)
- Biliopancreatic diversion with/without duodenal switch (BPD/DS and BPD respectively)
There is no single surgical procedure that can be recommended for all patients in general; rather, the choice of procedure should be tailored to the patient's personal medical, psychosocial, and general circumstances.[22] Current evidence does not allow definition of a surgical "gold standard" as the primary procedure in bariatric and metabolic surgery.
In patients with extreme obesity (BMI > 50 kg/m²) and/or significant comorbidity, a staged approach may be considered, e.g., sleeve gastrectomy first, followed by gastric bypass, to reduce the perioperative risk.[23] Ideally, all procedures should be performed laparoscopically.
1. Sleeve gastrectomy (SG)
SG was initially introduced in biliopancreatic diversion with duodenal switch (BPD/DS) for additional transit restriction and ulcer prophylaxis. By now it has become established as a stand-alone surgical procedure. SG was first described by Marceau in 1993.[24] In patients with extreme types of obesity (BMI > 50 kg/m²) and/or severe comorbidity, a staged approach is an option, e.g., first sleeve gastrectomy and then gastric bypass, to reduce the perioperative risk.[23]
The excess weight loss two years after SG does not differ significantly from weight loss after pRYGB. After five years, the weight loss following SG is around 50% and the rate of remission in T2DM is 58%.[26–30] SG sometimes has significantly fewer perioperative complications compared to gastric bypass. Post-SG morbidity is reported to be 7–8%.[15,29,31,32,33] The mortality in high-volume centers is well below 1%.[15] The most common complications are staple line fistulas, abscess formation, and secondary bleeding.
At present there are no clear contraindications to SG. Only in cases of preoperative evidence of symptomatic and/or refractory gastroesophageal reflux should the indication be reevaluated critically.[29]
2. Proximal Roux-en-Y gastric bypass (pRYGB)
First described in 1967 by Mason and in 1969 by Ito with a rather large pouch volume, pRYGB had been considered in the past as the gold standard in bariatric and metabolic surgery. Nowadays, it is performed in the laparoscopic modification of Wittgrove from the 1990s with a very small pouch (<15 ml).[34,35]
pRYGB offers outstanding long-term results in terms of weight loss and remission of pre-existing T2DM. In the meta-analysis by Chang et al., the mean weight loss after pRYGB was 14 BMI points compared to conservatively treated controls, while Yu et al. reported 12.6 BMI points.[36,37] After five years, the expected excess weight loss is 60–65%. On average, the procedure results in remission of pre-existing T2DM in 75% of cases.[16,37] In the meta-analysis by Chang et al., mortality was reported to be less than 1% for pRYGB, morbidity was 21%, and the reoperation rate 3%.[36] As such, pRYGB has a higher postoperative morbidity and reoperation rate than SG, while the incidence of severe complications is similar. In terms of effectiveness in T2DM, the pRYGB is superior to SG.
3. Omega-loop gastric bypass (OLGB)
Mini-gastric bypass (MGB) was first performed by Rutledge in 1997 and is regarded as a safe and effective procedure in bariatric and metabolic surgery. MGB is based on the principle of fashioning a long gastric pouch on the lesser curvature of the stomach, combined with an afferent small bowel biliary limb of variable length. In general, the length from the ligament of Treitz to the gastrojejunostomy is 200cm. Depending on the degree of the obesity, some surgeons prefer longer afferent limbs (250–300 cm). A length of 250 cm is recommended in severely obese patients, 180–200 cm in elderly patients and vegetarians, and 150 cm in T2DM without massive obesity.
The conversation rate from laparoscopic to open procedure ranges from 0% to 1.23%.[22] The MGB weight loss is reported as a BMI reduction of 11.3 kg/m² or an excess weight loss of between 61% and 69% after 12 months, and between 72.9% and 77% after five years.[22,38,39] The remission rates reported for T2DM vary between 51% and 100%. [39] Weight loss and T2DM remission rates are greater after MGB than post pRYGB.[39]
The number of postoperative complications after MGB is between 0% and 28.6%. The most common complications are bleeding requiring endoscopic or surgical intervention (0.2–28.6%) and anastomotic ulcers (1–14.3%). The mortality rate is 0–0.5%.[38]
4.1 Biliopancreatic diversion (BPD)
BPD was developed by Scopinaro in the 1970s and, as in pRYGB, bypasses the duodenum and isolates the food transit from the digestive secretions while .[40,41] Internationally, BPD is regarded as the standard procedure, but in terms of numbers it has not really gained acceptance in Germany.
The meta-analysis by Panuzi et al. showed that of all bariatric surgical procedures this malabsorptive surgical technique has the highest remission rates in pre-existing T2DM.[16] Diabetes remission was achieved in 89% of patients after BPD, in 77% of patients after pRYGB, and in 60% of patients after SG. Similar results were also reported by Müller-Stich et al. and Mingrone et al.[12, 42] The same applies to excess weight loss but there are no high-quality data available to date.
In the meta-analysis by Panunzi et al., the perioperative mortality in BPD was reported to be 0.8%. BPD is mainly based on the principle of malabsorption with extremely fatty stools, which inevitably reduces nutrient absorption, such as fat-soluble vitamins. Various studies have reported a significant decrease in vitamin A and E levels in up to 40% of patients. Vitamin D deficiency is seen in up to 61% of cases after BPD, iron and ferritin deficiency in up to 16%, and zinc deficiency in 40–68%.[43] A systematic review by Rodriguez-Carmona et al. demonstrated that bone density can decrease significantly after BPD, posing a considerable risk of spontaneous fractures.[44]
Malabsorptive surgical procedures also result in restricted absorption and reduced efficacy of treatment related medication.[45]
The overall complication rate after laparoscopic biliopancreatic diversion is up to 25% (gastric staple line failure; duodenal remnant failure; incisional hernia; duodenojejunostomy stricture).[46] In a retrospective observational study, a significantly higher percentage of postoperative ICU admissions and cases of orotracheal intubation (30.5%) was identified after BPD than after gastric bypass and sleeve gastrectomy (12%). Mortality was 6% for BPD, whereas no death was reported for SG or pRYGB.[47]
4.2 Biliopancreatic diversion with duodenal switch (BPD/DS)
BPD/DS is a complex operation combining restriction (sleeve gastrectomy) with malabsorption (postpyloric Roux-en-Y reconstruction).
It was first performed in 1988 as an open operation by Douglas Hess.[48] Due to the good outcome (sustained weight loss, high remission rate of pre-existing tT2DM), the procedure established itself and was first performed laparoscopically by Michael Gagner.[49]
By now, however, BPD/DS is rarely performed worldwide, accounting at most for 2% of all bariatric surgery and metabolic procedures.[50] The reason for this is likely to be the significant increase in perioperative morbidity and mortality compared to other interventions as well as postoperative deficiency symptoms, which, due to the pronounced malabsorption, may occur in a high percentage of cases despite replacement therapy.[15,51,52,53]