Core Topics in General & Emergency Surgery: Companion to Specialist Surgical Practice (88 page)
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Authors: Simon Paterson-Brown MBBS MPhil MS FRCS
Bruce R. Tulloh and
Andrew C. de Beaux
Trends in the UK and many other parts of the developed world show a steady increase in obesity over the last 30 years and there are no signs that this is decreasing. Obesity places an enormous health burden on our society because of the medical comorbidities that are associated with it, such as type II diabetes, hypertension, dyslipidaemia, steatohepatitis, obstructive sleep apnoea, arthritis of the weight-bearing joints, gastro-oesophageal reflux, depression and infertility. In general, these medical problems improve or even resolve in parallel with weight loss. Surgery specifically aimed at weight loss (‘bariatric’ surgery, from the Greek word
baros
= weight,
iatrikos
= medical) has been developing since the 1950s but it is only in the last 20 years, in the wake of advances in laparoscopy, that surgery has become increasingly popular.
Over the past decade, following the publication of several long-term outcome studies that showed a significant improvement in cardiovascular risk and mortality after bariatric surgery,
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the number of bariatric procedures being carried out annually in the UK has grown exponentially. Surgery remains the only way to produce significant, sustainable weight loss and resolution of comorbidities. Nevertheless, relatively few surgeons have developed an interest in this field. Most bariatric surgery is now performed in centres staffed by surgeons with a bariatric interest, usually as part of a multidisciplinary team.
Bariatric surgery is the only method of producing long-term, reliable and significant weight loss with resolution of the associated morbidities of morbid obesity.
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Although the number of hospitals providing a bariatric service in the UK is undoubtedly growing, many patients still have to travel long distances for their surgery – some even go overseas. Procedures are generally performed using laparoscopic and/or endoscopic techniques and lengths of stay are short. In the event of postoperative complications, patients can therefore present back at their local hospital or clinic, where there may be no specialised knowledge or expertise in the field. The aim of this chapter is to inform general surgeons on the disease process of obesity and the current bariatric procedures that are commonly performed, to outline the common complications that may arise and to provide management guidance for those patients that present in an emergency setting. Several articles have been written on the topic recently,
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which reflects its current level of interest.
While obesity is the result of a chronic energy imbalance when food (calorie) intake exceeds energy expenditure, such an explanation on its own is too simplistic. Obesity should be considered a multifactorial socio-psycho-endocrine disease process.
It is now clear that there is a complex physiological adipostatic system in place that works to maintain a constant body weight in the face of daily fluctuations in energy balance.
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The hypothalamus is an important control centre for this process, integrating a variety of both short-term and long-term energy flux signals. The gastrointestinal (GI) tract produces a number of hormones including ghrelin, glucagon-like peptides (GLP)-1 and 2, peptide tyrosine, insulin and cholecystokinin, which not only influence gut motility and exocrine secretions but also exert positive and negative feedback on the hypothalamus to regulate appetite. Ghrelin, the ‘hunger hormone’, is released from the gastric body and promotes appetite, while leptin, a hormone that circulates in proportion to the body's fat mass, has a negative feedback on the hypothalamus to promote negative energy balance. Neural pathways are also involved via vagally innervated stretch receptors in the stomach wall, which induce satiety (and even nausea) in response to gastric distension.
There are also social and psychological drivers to eat. Eating is a pleasurable activity and, for many, meals are the hub of family and social events. Eating may also provide comfort to address fear, loneliness or anxiety. There is now evidence that such negative emotions increase food consumption and that obese people eat in response to emotions more than normal-weight people.
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Dieting is known to be difficult and, for many, is not successful in the long term. Modern human beings have evolved from nomadic hunter-gatherers and our physiology defaults to energy storing in periods of food shortage. Thus dieting induces a physiological adaptation to starvation. This stimulates appetite, induces the bowel to absorb a greater proportion of food eaten, reduces energy loss by a subtle lowering of body temperature and promotes fat storage.
Surgery is the most effective treatment for severe and complex obesity because it alters the physiological processes at the heart of weight homeostasis. Different procedures do this in different ways.
Traditionally, weight loss operations have been described as either restrictive or malabsorptive, influencing either the volume of food that can be ingested or the absorption of food at the mucosal level, respectively (or both). However, it is more likely that surgery interacts in a beneficial way with the complex adipostatic system outlined above. Gastric band patients, for example, who are restricted in their oral intake by the constricting ring around their upper stomach, do not show the normal hormonal adaptation to starving. Part of the band's action appears to be through feedback to the adipostat, possibly via vagal afferents. Similarly, patients undergoing a so-called malabsorptive operation, such as gastric bypass, do not suffer chronic diarrhoea; their weight loss is mediated by a series of gut hormonal changes that influence appetite, food choices and gut motility, amongst other things.
Even so, iatrogenic manipulations of the adipostat are not the full story. In order to achieve the best outcomes, patients still need to make a series of healthy dietary and lifestyle changes along the lines of eating sensibly and being physically active. Authorities agree that postoperative weight maintenance is improved by the ongoing encouragement, advice and support obtained from long-term follow-up in a bariatric clinic.
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While weight control is a complex process, the mechanisms behind the postoperative resolution of obesity-related comorbidities are also complex and, even now, not fully understood. Control of type II diabetes mellitus, for example, is known to improve in parallel with the gradual weight loss that follows gastric band surgery.
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However, the gastric bypass and duodenal switch operations can normalise glucose tolerance much more quickly, even before there has been any appreciable weight loss.
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Such changes are mediated by gut hormones that are stimulated either by a lack of nutrients in the foregut or by the rapid post-prandial delivery of food to the hindgut, with a resultant improvement in pancreatic function and a reduction in peripheral insulin resistance. These processes are well explained elsewhere
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and will not be expanded upon here.
The commonest weight loss procedures performed around the world at present are the gastric band, the gastric bypass and the sleeve gastrectomy. In very obese patients, an alternative operation is the duodenal switch, while the new ileal transposition procedure represents one of the few purely metabolic operations designed specifically for the treatment of type II diabetes. Older operations such as vertical banded gastroplasty and jejuno-ileal bypass are now obsolete, although patients who have undergone such procedures in the distant past may still present to hospital with complications. The main endoscopic option at present is insertion of a gastric balloon, with newer procedures like the endoscopic duodenojejunal barrier and gastric plication on the horizon. Implantable neuroregulatory devices (gastric ‘pacemakers’) represent a new direction for surgical weight control by harnessing neural feedback signals to help control eating.
The reason that so many options exist is because no procedure is perfect. Each brings its own benefits and risks. There is little evidence to indicate which operation suits which patient, although most series demonstrate greater average weight loss from operations with a malabsorptive component over restrictive operations alone.
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In practice, the final choice of operation emerges from a detailed discussion between the patient and their surgeon about the options available and the potential risks and benefits of each one.
The gastric band is an inflatable silicone ring fixed around the proximal stomach to create a zone of constriction with a small proximal gastric pouch of approximately 30 mL. The band sits around the angle of His, runs along the line of the left crus of the diaphragm and typically lies at about 45° to the horizontal in the 8-to-2 o'clock direction (
Fig. 19.1
). Many surgeons secure the band in position with a number of gastro-gastric sutures from the fundus below the band up on to the small gastric pouch. The band connects by tubing to an injection port, which is then secured subcutaneously on the anterior abdominal wall. Instillation or aspiration of saline via the subcutaneous injection port adjusts the degree of constriction produced by the band. The amount of saline required in the band varies from patient to patient and often a number of fine adjustments are needed to achieve just the right level of restriction so that patients can manage small portions of normal food.
Figure 19.1
Barium meal showing band sitting at a normal angle of approx 45°, in the 8-to-2 o'clock direction (arrow).
This is the most common bariatric operation now performed worldwide. The first step involves using the linear cutting stapler to separate a small proximal gastric pouch, again approximately 30 mL in volume, from the distal stomach, which is left in situ. The small bowel is then divided 50–100 cm beyond the duodenojejunal (DJ) flexure and the distal side anastomosed to the gastric pouch, in an antecolic or retrocolic position. The proximal side, representing the biliopancreatic limb of the Roux-en-Y reconstruction, is anastomosed 100–150 cm distal to the gastro-jejunostomy (
Fig. 19.2
). Any mesenteric defects are closed to prevent subsequent internal herniation.
Figure 19.2
Diagram of a gastric bypass.
A more recent modification of the gastric bypass is the mini-gastric bypass, so called because it is quicker and easier to perform. The essential differences between this and a conventional bypass are that a longer gastric pouch is created and a Polya-type antecolic loop gastro-jejunostomy, rather than a Roux-en-Y configuration, is constructed (
Fig. 19.3
). Early results are satisfactory but long-term outcome data are lacking. Many authors remain sceptical, believing this operation to be a retrograde progression in technique as the Polya reconstruction has been largely abandoned in both benign and malignant upper gastrointestinal surgery because of the problems of bile reflux.
Figure 19.3
Diagram of a mini-gastric bypass.
This operation was originally developed as the first stage of a duodenal switch operation but soon became a stand-alone procedure when its weight loss outcomes were, at least initially, similar to what was achievable with a gastric bypass.
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It is also technically easier to perform than any of the Roux-en-Y procedures, particularly in super-obese patients. The greater curve of the stomach is separated from the omentum from the angle of His to a point 5–6 cm proximal to the pylorus. A bougie, commonly around 34 French in size, is inserted down to the antrum and manipulated up against the lesser curve. Using a linear cutting stapler and with the bougie as a guide, the body and fundus of the stomach are excised and removed (
Fig. 19.4
).
Figure 19.4
Diagram of sleeve gastrectomy. The omentum (not shown) is preserved on the gastro-epiploic arcade.
The duodenal switch operation can be performed as a two-stage procedure but is more commonly carried out in one sitting.
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The first stage is a conventional sleeve gastrectomy. The second stage involves dividing the duodenum just distal to the pylorus and then dividing the small bowel halfway between the DJ flexure and the ileocaecal junction. The distal part of the divided small bowel is then anastomosed to the proximal end of the divided duodenum just beyond the gastric outlet (pylorus). Thus the jejunum is ‘switched’ for the duodenum. The biliopancreatic (Roux) limb of the divided small bowel is then joined to the ileum 1 metre proximal to the ileocaecal valve (
Fig. 19.5
). This creates a longer bypassed segment and a much shorter common channel than a standard gastric bypass procedure, resulting in significantly more malabsorption. An earlier version of this operation, which involved a more conventional partial gastrectomy instead of a pylorus-preserving sleeve resection, is known as a biliopancreatic diversion (BPD) or Scopinaro procedure.
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Figure 19.5
Diagram of bilio-pancreatic diversion (BPD) (a) and duodenal switch (b).The common channel is approximately 100 cm long.
This plastic balloon is inserted endoscopically and inflated with saline under vision to between 500 and 700 mL (
Fig. 19.6
). This induces a feeling of fullness and thus reduces oral intake. Because the satiety effect wanes after several months and there also remains a small risk of leakage/deflation in situ, with the possibility of distal migration of the collapsed balloon, it is recommended that the balloon is removed after 6 months. Removal involves another endoscopic procedure in which the balloon is punctured, aspirated and withdrawn.
Figure 19.6
Abdominal X-ray of a patient with a gastric balloon in situ.
There is little evidence to indicate which operation suits which patient, although most series demonstrate greater average weight loss from operations with a malabsorptive component over restrictive operations alone.
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