Perioperative management - Mini Gastric Bypass / Omega Loop Gastric Bypass

Surgical interventions, like all other therapeutic approaches for the treatment of obesity, do not address the underlying cause, as the actual cause of obesity is complex and still largely unknown. According to guidelines in developed countries, the indication for surgical intervention is given in the following cases:

BMI ≥ 40 kg/m², where conservative treatment measures (nutritional, exercise, behavioural and pharmacotherapy, alone or in combination) have demonstrably been unsuccessful.

BMI ≥ 35 kg/m² with one or more obesity-associated comorbidities such as type 2 diabetes mellitus, coronary heart disease, heart failure, hyperlipidaemia, arterial hypertension, nephropathy, obstructive sleep apnoea syndrome, obesity hypoventilation syndrome, Pickwickian syndrome, non-alcoholic fatty liver disease or non-alcoholic steatohepatitis, gastro-oesophageal reflux disease, asthma, chronic venous insufficiency, urinary incontinence, immobilising joint disease, impaired fertility, or polycystic ovary syndrome.

Primary indication without prior attempt at conservative therapy:

• BMI ≥ 50 kg/m²
• An attempt at conservative therapy is deemed unpromising or futile by the multidisciplinary team.
• In patients with severe comorbidities and associated complications that do not permit postponement of surgical intervention.

A primary indication in the sense of metabolic surgery may be established in patients with a BMI ≥ 40 kg/m² and coexisting type 2 diabetes mellitus, when the treatment goal is focused more on improving glycaemic metabolic control than on weight reduction. For these patients, evidence of an exhausted conservative therapy in the sense of bariatric surgery is not required to establish the indication for surgery [American Diabetes Association 2017].

When choosing the procedure, the following parameters should be considered:

• the patient's initial weight (BMI)
• the expected weight loss (EWL)
• compliance
• the age
• a possible desire for children in women
• comorbidities (especially diabetes mellitus)
• the surgical risk

Other factors to consider are:

• gender
• occupation
• dietary habits

There is no surgical procedure that can be recommended across the board for all patients; rather, the choice of procedure should be tailored individually to the medical, psychosocial, and general life circumstances of the patient.

All procedures should ideally be performed laparoscopically.

The Mini Gastric Bypass (MGB) is also known as a single anastomosis bypass. Its advantage is a procedure with the gastroenterostomy as the only anastomosis, thereby eliminating all complications relating to the jejunojejunostomy.

The Mini Gastric Bypass, MGB for short, is regarded as a safe and effective procedure in bariatric and metabolic surgery. The principle of the MGB is the formation of a long lesser-curvature gastric pouch combined with a biliary small-bowel loop, the length of which may vary. Typically, it measures 200 cm from the ligament of Treitz to the gastrojejunostomy. Depending on the severity of the obesity, longer biliary limbs (250-300 cm) are also chosen. In severe obesity, a length of 250 cm is recommended, in older patients and vegetarians a length of 180-200 cm, and in type 2 diabetics without massive obesity a length of 150 cm is recommended.

• Wasting diseases such as malignant neoplasms, untreated endocrine causes, and chronic diseases that worsen due to a postoperative catabolic metabolism.
• Pregnancy
• Lack of compliance
• Unstable psychopathological conditions, untreated bulimia nervosa, active substance dependence.
• Diseases of the stomach and duodenum

Since bleeding in the gastric remnant cannot be treated endoscopically, there is a contraindication for patients

• on lifelong blood-thinning medication (phenprocoumon or ASA)
• with a chronic need for pain medication (ulcerogenic)

A preoperative gastroscopy should be performed before all bariatric procedures in order to exclude relevant diseases of the oesophagus or stomach, whose incidence is increased in obesity.

The following conditions should be considered and clarified and treated before surgery:

• Reflux

• Erosive gastritis

• Helicobacter pylori infections

• Barrett's oesophagus

• Oesophageal carcinoma

• Gastric tumours

• Ulcera ventriculi et duodeni.

Risk evaluation is of high importance in obesity surgery. In addition to standard diagnostics (ECG, chest X-ray, laboratory tests), it always includes a lung function test and an assessment of nutritional status.

Routine polysomnography is standard in US clinics, as between 77 and 88% of patients there have sleep apnoea.

• Preoperative therapy for Helicobacter pylori infection to prevent gastric/anastomotic ulcers
• Patient preparation begins before hospital admission with physical conditioning: smoking cessation, a liquid diet at least 2 days before admission (ideally 2 weeks), and adjustment of medications that may increase risk (Metformin, oral anticoagulants, etc.).
• Bowel preparation is also recommended when performing gastric bypass.
• General hygienic requirements in preparation do not differ significantly from other procedures. Intertriginous skin fold affections and acute inflammatory ulcera cruris or diabetes-related changes of the lower extremity should be given particular attention.
• Pharmacological thrombosis prophylaxis begins on the day of surgery and is dosed according to body weight.

The information must be particularly comprehensive, as this is an elective procedure. In addition to covering the general surgical risks of laparoscopy and conversion to laparotomy, this includes highlighting the specific risks. The intraoperative risks, the short- and long-term consequences, up to transfusion and the mortality risk, should be explained.

In general, this is a major procedure with many potential complications, even if the access is only minimally invasive (laparoscopy).

General Complications:

• Infection (including hepatitis), especially blood transfusions and transfusions of blood components
• Thrombosis and embolism
• Bleeding requiring blood transfusions
• Wound healing disorders
• Nerve injuries
• Skin and tissue damage from electric current, heat and/or disinfectants. These injuries are rare and usually resolve on their own.
• Allergies and hypersensitivities (e.g. to medications, disinfectants, latex)
• Injuries to the pharynx and oesophagus when inserting the gastric tube
• Injuries to the urethra and bladder from inserting a urinary catheter
• Positioning injuries to nerves or soft tissues with sensory disturbances and, very rarely, paralysis of the arms and legs. The risk is considerably higher in extremely obese individuals than in those of normal weight.
• Gas insufflation during laparoscopic surgery can cause a feeling of pressure and shoulder pain. These, like crepitus of the skin, subside rapidly. If the gas enters the pleural cavity (pneumothorax), it may be necessary to insert a chest drain.
• Numbness of the skin in the area of the surgical scars may remain.
• In some patients, impaired wound healing or an individual predisposition may result in excessive scar formation (keloid formation). Such scars may be painful and aesthetically disturbing.

Specific complications:

• A later reversal of the operation (reconnection of the stomach) is effectively no longer possible, or only possible with a high surgical risk.
• The remnant stomach can no longer be endoscoped (endoscopy), and endoscopic treatment of bile duct stones (ERCP) is no longer possible by conventional means.
• Injury to the stomach, oesophagus, and other organs such as the spleen and pancreas is possible.
• If the spleen is injured, the organ may also have to be removed, which can subsequently result in an increased susceptibility to infection.
• In the event of leaks in the sutures/anastomoses, peritonitis may occur, necessitating reoperation.
• A change in procedure (from laparoscopic to open surgery) is possible if complications arise or if continuing the videoendoscopic operation is associated with too high a risk; the decision rests with the surgeon.
• Previous operations in the abdominal cavity increase the surgical risk and the level of difficulty. Previous operations in the left upper abdomen in particular (stomach, diaphragmatic hernia, ...) complicate the procedure.
• After the operation, internal hernia incarcerations, adhesions, bowel obstructions, abscesses (collections of pus), narrowing of the gastrointestinal connection, and ulcers can occur in the immediate postoperative phase as well as later, after months and years.
• Sometimes, following an operation via an abdominal incision, an incisional hernia (hernia) occurs, which usually has to be closed surgically. In laparoscopic operations, this can also occur in the area of a trocar.
• If the abdominal suture breaks open along its entire length after open surgery (burst abdomen), reoperation is unavoidable.
• Long-term consequences can include vitamin and iron deficiency, short bowel symptoms, and a disturbance of calcium metabolism with the consequences of osteoporosis.
• In the case of a planned pregnancy, increased vitamin supplementation is required, as malformations may otherwise occur. Contraception is no longer guaranteed with malabsorptive procedures.
• The success of the treatment and the avoidance of complications depend on the patient's cooperation. There is a need to adhere to dietary habits and follow-up examinations. Failure to comply with the prescribed rules (number of meals, small portions, food selection) can lead to problems and result in reduced weight loss.