This blog provides free general information for anyone who is seeking to understand more about the laparoscopic one anastomosis gastric bypass, not intended as a medical consult. Please seek proper medical advice for individual assessment and management.

Please read the section on sleeve or Roux Y gastric bypass as well for more information.

Management of the obesity crisis

The increasing demand for treatment of morbid obesity, has led to wide variety of options for weight loss management, which range from conservative (lifestyle) management to medical management (appetite suppression medication use or lipase enzyme suppression), endoscopic management (gastric balloons, endoscopic sleeve gastrectomy, possibly more procedures in the future) and surgical management.

Over the last two decades, patients have been advised to consider various bariatric surgical procedures, which include laparoscopic gastric band, sleeve gastrectomy and Roux Y gastric bypass.

There are also the less common but more aggressive weight loss procedures, which included the bilio-pancreatic diversion or duodenal switch (BPD-DS) procedure.

• These may be recommended as an initial treatment option (primary procedure) or more likely as revisional surgery (conversion procedure) after previously failed weight loss procedure.

With the increasing number of primary procedures being performed across the world, we have also seen a great increase in the number of secondary procedures, which is performed for selective patients to address unique problems.

Indications may include inadequate weight loss, physical or psychological intolerance of the primary procedure or complications of the primary procedure.

• For example, after previous failed gastric band or sleeve gastrectomy, some patients are seeking for the more aggressive bypass procedure. This has driven some patients and surgeons to consider or choose the OAGB to be the primary weight loss procedure.

Having said that, it is also a good time to re-iterate that bariatric surgery is not about achieving the maximum weight loss result. Please read the section on sleeve or gastric bypass.

Choosing to have a sleeve gastrectomy or gastric bypass is based on so many other clinical aspects as well, which include:

• Not just the long term weight loss result and weight regain
• Issues with Type 2 diabetes mellitus and post op reflux
• Issues with subfertility and future pregnancy
• Issues with gallstones and ERCP

Secondly we emphasized that weight loss surgery is only a tool.

• It should be considered as a combined multi-modality approach rather than just the operation. Patients need to be compliant to follow the advice from their GP, dietician, exercise physiologist, psychologist and others.

Australian Medicare criteria for bariatric surgery

As always the most important and only indication for bariatric surgery is for health reasons, this is not regarded as a cosmetic procedure. The procedure is for treatment of morbid obesity (BMI>40) or those with obesity (BMI>35) and associated medical problems, in Australia this is primarily cardiovascular disease or risk factors and certain cancers (such as breast or endometrial cancer).

The aim is to:

• Achieve durable and maintained excess weight loss (>50% EWL)
• Treatment (or resolution) of obesity associated co-morbidities (mainly Type 2 diabetes mellitus, hypertension, dyslipidaemia, obstructive sleep apnoea)
• Improvement of quality of life (in physical, social, family circles, employment and emotional well being
• Increase survival (life span)

One Anastomosis gastric bypass (OAGB)

Introduction

The other names for the one anastomosis gastric bypass are single anastomosis gastric bypass (SAGB), omega loop gastric bypass (OLGB) or mini gastric bypass (MGB).

The single anastomosis gastro-ileal bypass (SAGI) and the single anastomosis sleeve ileal bypass (SASI) has also been introduced recently. Strictly speaking these procedures are referred to as sleeve plus and not gastric bypass but they are more similar to OAGB than a sleeve.

• These operations may be more aggressive than the OAGB because the anastomosis is to the distal small bowel, measured as 250-300cm proximal to the ileo-caecal junction.

The MGB procedure was first introduced by Dr Rutledge, a surgeon in USA in 1997. Having said that, this procedure has been around for a while, with resemblance to the Mason gastric bypass (distal gastrectomy and Billroth 2 gastric reconstruction) that were done in the last century.

History and variations in surgical techniques

The 1960-70s Mason gastric bypass was a short wide proximal gastric pouch/fundus and a wide horizontal gastroplasty (a high gastro-jejunostomy).

• This has the potential for bile reflux from the afferent limb.
• In theory this may increase the risk of bile damage, increase the risk of gastric or oesophageal cancers.

The 1997 Rutledge MGB is a long narrow gastric pouch, with a 3 to 5cm gastro-jejunostomy using  bilio-pancreatic limb 180-250cm distal to the ligament of Treitz, depending on the age and degree of obesity or whether the patient was a vegetarian.

The 2002 Carbajo-Caballero OAGB (also known as BAGUA in Spanish), using a side-side gastro-jejunostomy anastomosis and a 250-350cm bilio-pancreatic limb.

The single anastomosis gastro-ileal gastric bypass (SAGI or SASI) is a variation of the OAGB.

• The difference is in the technical aspect of the operation, instead of doing the small bowel anastomosis between 150 to 200cm distal to the duodenal jejunal flexure the anastomosis is done onto the jejunum measured at 300cm proximal to the ileo-caecal valve.

Currently and maybe in the future, some surgeons believe that the bilio-pancreatic limb should be standardised to 150cm to reduce the risk of macro or micronutrient deficiencies. This is yet to be determined.

The reasons for this include:

• OAGB with an afferent limb more than 200cm does result in more weight loss or greater resolution of medical co-morbidities
• In most patients, the efferent limb length should be >400cm to prevent malabsorption side effects

Measuring the total bowel length may be necessary to avoid creating a short small bowel, which may increase the risk of malnutrition

The current One Anastomosis Gastric Bypass (OAGB)

As stated above, there are 2 main variations of the surgery, either a conservative 150cm or a standard 200cm bilio-pancreatic (BP) limb being used in this operation. Some centres may even use a longer BP limb.

There is no consensus or established guidelines to suggest that it is better to perform a biliary limb length of a 150cm, 200cm, 250cm or more for the primary or revision procedure.

Individual surgeon may tailor the BP limb length depends on the BMI or the total alimentary limb length.

• For example for patients with BMI >50, some surgeons would perform a 200cm OAGB.

On the contrary some surgeons believe that every patient should have a BP length of 150cm regardless of the patient’s starting BMI. Especially when the same operation delivers a similar weight loss outcome and potentially less risk for long term nutritional or micronutrient deficiencies.

Personally I perform the 150cm OAGB for almost every case because it is:

• Safe and effective in the medium term
• Not associated with a poorer weight loss outcome compare to the 200cm OAGB (for patients BMI >50)
• Longer BP lengths may increase the risk of protein calorie malnutrition and micronutrient/vitamin deficiencies

The disadvantage of an OAGB include:

• Potentially a risk for alkaline/bile reflux, potentially may lead to gastric or oesophageal malignancy.
• There may be a higher rate of nutritional deficiencies after an OAGB because of the longer segment of proximal small bowel being bypassed, especially when more than 200cm of the BP limb was created. Reversal of the surgical procedure is needed for severe malnutrition.

Trends

The OAGB had a slow uptake at first but now is rapidly becoming a popular option amongst surgeons in Europe, certain parts of Asia and Australia/New Zealand.

In South East Asia, the single anastomosis gastric bypass is performed for Type 2 diabetes and not necessary for morbid obesity BMI>40.

Currently OAGB:

• Is recognized and endorsed by the International Federation for the Surgery of Obesity and Metabolic Disorders (IFSO).
• Previously (2018 and 2020), The American Society for Metabolic and Bariatric Surgery (ASMBS) have decided not to endorse the OAGB due to the potential carcinogenic risk for bile/alkaline reflux and concerns about long term nutritional deficiencies, especially when more than 200cm of the BP length is utilized. In 2022 it has been endorsed by the ASMBS.

Currently (in 2020) the OAGB is now the third most commonly performed bariatric procedure after the sleeve gastrectomy and RYGBP.

• In the future it may overtake the RYGBP as the second most popular procedure, if there is a decrease in the proportion of sleeve gastrectomies being performed around the world and increase in the OAGB.

Results

The OAGB provides effective durable weight loss results.

• Weight loss result from primary OAGB has been reported to be 70 to 80% excess weight loss (EWL).
• Revision OAGB have unpredictable outcome, perhaps 50% EWL.

The OAGB has been reported to result in remission of hypertension (over 65%), Type 2 diabetes mellitus (over 80%) or metabolic syndrome (over 80%).

Studies comparing it to the sleeve gastrectomy, showed that the OAGB may have a higher incretin effect and may achieve better glycaemic control and better improvements in dyslipidaemia.

OAGB versus the sleeve gastrectomy (LSG)

Both the LSG and OAGB are proven to be safe, effective, feasible and well tolerated.

OAGB have:

• Better results in terms of EWL, maintenance of EWL, medical co-morbidity resolutions (HPT, T2DM).
• There may not be a statistical significant difference between the two procedures, especially in the first 2 to 3 years.
• The risk of weight regain after a LSG is higher especially with time, 2 to 5 years after the initial operation.

OAGB may be a better weight loss procedure than the LSG in the super obese (BMI>50).

Apart from the durability of weight loss, OAGB may have better incretin effect and fat malabsorption. This may explain the better T2DM remission rates.

The OAGB may have a higher risk for bile gastritis/reflux.

• Revision surgery may be necessary for acid/bile reflux or weight regain, especially after 3 to 5 years.

The main disadvantage of OAGB include:

• OAGB patients are at risk for developing marginal ulcers.
• With intestinal bypass, there are alterations in bile salt absorption and the entero-hepatic circulation, hence the risk of gall stone formation is higher. After OAGB, ERCP procedure is extremely difficult to be performed.

OAGB versus the Roux Y gastric bypass (RYGBP)

The advantages of OAGB

Now that the OAGB has been performed in large numbers across the world, researchers have manage to draw some conclusions (called meta-analysis) from these studies.

OAGB showed:

• Weight loss result to be equivalent or better than the RYGBP (with up to 5 years follow up), what is termed a non-inferior or superior results compare to the RYGBP (still considered the gold standard by many surgeons).
• The rate of T2DM remission was better in the OAGB group but the rate of HPT and dyslipidaemia remission was similar in both groups.

Another study reported both OAGB and RYGBP have good weight loss result, good resolution for HPT and T2DM but probably no statistical significant difference between the two procedures.

Please note it is difficult to be precise when comparing these two procedures because there are so much variation in surgical techniques. Hence the conclusions of the studies need to be interpreted with caution.

• As described above for the OAGB the bypassed afferent limb is mainly between 150 to 200cm, a relatively consistent measurement.
• With the RYGBP however, there are many different variation in the lengths of the bilio-pancreatic limb, alimentary limb length and the length of the common channel (eg. proximal versus distal RYGBP). Hence the results (weight loss, resolution rate for medical co-morbidities, complication rates, etc) also varies according to the surgical technique.

Regarding short/medium term complications, the incidence of leak, haemorrhage, marginal ulcer, dumping, mortality and revision surgery rates are very similar between the OAGB and RYGBP. Both procedures are safe and feasible.

Some surgeons believe that the OAGB may result in less early dumping than the RYGBP.

• Theoretically in the alimentary limb of the RYGBP, due to the absence of sodium from bile salts, there is less activation of the sodium glucose transporter and less absorption of sugars and hence creating an increased osmotic load and fluid loss into the lumen of the gut.
• There is no difference between the two procedures in terms of late dumping, the mechanism here is different due to the insulin release causing a late post prandial hypoglycaemia.

Regarding long term complications, the incidence of malnutrition was slightly higher in the OAGB group.

• Hence some surgeons are beginning to recommend a bilio-pancreatic limb of 150cm for all patients regardless of the index BMI.

The Roux Y gastric bypass takes longer to do because of the second anastomosis. There is a risk for internal hernia and small bowel obstruction, which is not an issue with the OAGB.

• One study reported up to 16% internal hernia rate at 10 years follow up

The main disadvantage of the RYGBP is the second anastomosis, which may increase the morbidity or mortality of the surgery.

• There may be a higher risk for anastomotic leak
• Post op intraluminal GIT bleeding
• Mesenteric haematoma or intra peritoneal bleeding
• Internal hernia from the small bowel mesenteric defect (Brolin space) or space between the transverse mesocolon and small bowel mesentery (Petersen’s space) resulting in chronic abdominal pain, acute small bowel obstruction or the potentially life threatening ischemic gut

The disadvantages of OAGB

The disadvantage of an OAGB include:

• Potentially a risk for alkaline/bile reflux, potentially may lead to gastric or oesophageal malignancy.
• There may be a higher rate of nutritional deficiencies after an OAGB because of the longer segment of proximal small bowel being bypassed, especially when more than 200cm of the BP limb was created. Reversal of the surgical procedure is needed for severe malnutrition.

There may also be a risk for gastric remnant cancer, which can’t be screened with gastroscopy because the stomach is excluded.

• We do not know whether this will be the case or not.

Relative or absolute contra indications for primary OAGB

The common relative contra indications may include young age (eg. patients who wish to have children in the near future), the presence of hiatus hernia and vegetarians.

Other contra indications may include symptomatic or severe reflux (erosive oesophagitis, Barrett’s oesophagus, peptic stricture), patients with substance abuse (cigarette smokers, drugs, alcohol), certain drug use (NSAIDs, steroids, immune-suppressants) and certain medical conditions (Crohn’s disease, liver cirrhosis, severe psychiatric issues).

Complications of OAGB

Complications may include anastomotic leak, stricture, bleeding, incisional hernia and bowel obstructions, usually reported between 1 to 5%.

One study published the complications rate for OAGB, below:

• Mortality rate 0.1%
• Leak rate <1%
• Post op reflux >2%
• Malnutrition <1%
• Anaemia >7%

Similar to the Roux Y gastric bypass (RYGBP), marginal/stomal ulcers is reported to occur in at least 2.5% in the OAGB.

• The risk is higher amongst cigarette smokers, those with Helicobacter infection, those who consume alcohol and non-steroidal anti-inflammatory medications (NSAIDs). 
• Some patients are given sucralfate or proton pump inhibitors (PPI) after gastric bypass to prevent ulcers but the duration of treatment is not certain (maybe for 3 to 6 months at least after OAGB surgery).

There may be a risk for acid or alkaline (bile) reflux.

• With hiatus hernia and acid reflux, surgery may be needed to repair the hiatus hernia.
• With bile reflux some surgeons perform a Braun anastomosis or convert the OAGB to a RYGBP.
  • At this stage bile reflux is under reported and most non American surgeons are not too concerned about the bile reflux.

Many surgeons do not believe that the OAGB has an increased for gastric or oesophageal cancers.

• This may not be the case with the Asian surgeons, who practice in countries where upper GI cancers are far more common than in Western societies.
• For patients who are concerned, a screening gastroscopy should be performed about 2 to 3 years after the OAGB. Obviously the remnant stomach can’t be accessed for a gastroscopy check.

Nutritional problems may include protein calorie malnutrition. For patients with extremely low levels of albumin, they may need to be admitted to hospital for IV albumin treatment or have the OAGB reversed back to a normal stomach. The risk may be reduced by using a shorter bilio-pancreatic limb, instead of 250cm or more, perhaps 150cm limb length may suffice.

The risk of internal hernia (from the Peterson’s space) is probably much less compared to the RYGBP.

There are always potential for inadequate weight loss or weight regain (>10% EWL) after OAGB.

This may be due to gastric pouch dilatation or inadequate bilio-pancreatic limb length. Because the OAGB is relatively new, there are lack of data in this area in terms of standardization of the surgical procedure or the statistics on weight loss failure.

Weight regain after weight loss surgery

Weight regain will occur after any bariatric surgery with time.

Weight regain may be associated with the return of medical co-morbidities (hypertension, T2DM) and reduced health related quality of life.

It is estimated that patient will regain 5-10% of their total weight loss (TWL) within the first decade after bariatric surgery.

The percentage of patients who develop weight regain after a sleeve gastrectomy and RYGBP may occur up to 76-87% or more. The weight regain after OAGB should be similar or a little less than the RYGBP.

Again it is important to remind patients that bariatric surgery is not just about weight loss. Resolution of medical problems, improvements in health related quality of life and avoiding side effects or complications of surgery is just as important.

Issues with weight regain     

It has been mentioned already in other sections that weight loss alone should not be the only focus of bariatric surgery.

Secondly it should be mentioned that weight loss failure also is not die to technical failures alone.

Obviously the surgeon is responsible to perform the bariatric surgery at the highest standard without any significant post op complications. But weight loss failure also depends on many factors.

The technical factors may be related to:

• The gastric pouch size
• The gastro-jejunal anastomosis size
• The bilio-pancreatic limb length
• The length of the common channel
• The total alimentary limb length

Non-technical factors may include:

• Age and physiology
• Underlying basal and active metabolism
• Genetic and epi-genetic factors
• Hormonal factors (menopause, PCOS, etc)
• Medications use that may have weight gain side effects
• Substance dependence (alcohol or others)
• Poor compliance to dietary advice and exercise programs
• Other unknown factors

This is why the surgeon often emphasize that weight loss surgery is an adjunct to positive lifestyle changes.

• Eating habits and behavior modifications is needed to ensure maintenance if weight loss.
• Patients will need to follow the advice of the bariatric dietician and exercise physiologist.
  • For example avoiding carbs, sweets, processed/refined foods, soft drinks or alcohol
• Some patients will need to address emotional or psychological issues behind the eating disorders.
• Patients will need to avoid risky behaviours that may compromise outcome
  • Eating late at night before going to bed, emotional eating, sabotage, etc.

Hence it is not just a simple option to choose between having an OAGB or RYGBP.

• More attention should be paid to correct patient selection, not just correct procedure selection, in order to achieve best weight loss outcome, optimal risk benefit ratio, improvement in quality of life and reduction in premature cardio-vascular mortality
  • For example, patient over 65 or 70 years of age may not have as much weight loss or be able to reverse the metabolic co-morbidities associated with obesity
  • In other words the governing bodies such as Medicare and the health funds requires clinicians to recommend bariatric surgeries only if it is going to be cost effective, have clinical benefits and improvements in quality of life
• The side effects and long term complications need to be considered, as to why patient choose to have one procedure over the other.
• Patients need to understand that there will be a proportion of patient (maybe up to 25-30%) may not achieve adequate weight loss even after an OAGB or RYGBP. Some of the reasons are mentioned above.

Issues with reflux

Some studies documented that 35-30% of patients were treated for GOR before the OAGB or RYGBP surgery. 10 years after surgery (OAGB or RYGBP) up to 20% of patients from both groups were still treated for GOR.

In the OAGB up to 1/4 of the patients have a conversion to RYGBP. However there are not much published data on the long term results and there is no guarantee that a conversion to RYGBP will aid the acid or bile reflux.

It is difficult to understand how patients can still have persistent GOR symptoms despite having a RYGBP and successful weight loss. It is also surprizing to find that there may be gastric remnant cancer and oesophageal cancers many years following RYGBP.

This highlights that the mechanisms of reflux are multi factorial, which include oesophageal clearance, lower oesophageal sphincter pressure and intermittent relaxation, hiatus hernia, loss of fat pad in the hiatal opening after weight loss, gastric clearance/stasis, bile refluxate, etc. Thus the decision to select or to perform LSG or OAGB or RYGBP is not that straight forward.

Revisional OAGB

Needless to say, revisional procedures have greater risk for perioperative complications as well as long term nutritional side effects and postoperative complications.

For patients who wish to have revision surgeries, it is advised that they do their research carefully.

Micronutrient deficiencies after gastric bypass

The most common is iron deficiency anaemia, vitamin B12 and D deficiencies.

• However it is also noted that a significant proportion of patients who present for bariatric surgery may already have iron and vitamin deficiencies.
• This is carried over after the weight loss operation.

Iron deficiencies are attributed to reduced oral/dietary iron intake and absorption as a results of:

• Reduced consumption of red meats
• Decreased hydrochloric acid production (or PPI medications use), which is normally needed to reduce the ferric (3+) state to the absorbable ferrous (2+) iron state
• Bypassing the duodenum and proximal jejunum (which are the primary sites for iron absorption)
• Iron deficiencies are more likely to occur 2 to 3 years after the initial bypass operation.

Blood tests to measure ferritin and total transferrin saturation is needed

Vitamin B12 may occur due to:

• Reduce consumption of animal protein
• Reduced gastric acid production, which impair vitamin B12 metabolism and release from R-binding protein
• Reduced production of intrinsic factor

Similarly vitamin B12 deficiencies are more noticeable 2 to 3 years after the initial bypass operation.

Vitamin B12 is needed for DNA synthesis and neurological function (to prevent demyelination and axonal degeneration)

Deficiency leads to:

• Macrocytic anaemia, fatigue and glossitis
• Neurological symptoms such as numbness/parasthesia (in hands, legs), ataxia, slow reflexes, vertigo, tinnitus, peripheral neuropathy and altered mental state

Folic acid is often associated with vitamin B12 deficiency

• Folic acid is mainly absorbed in the jejunum, which will be bypassed
• Deficiency may lead to high homocysteine levels and risk of atherosclerosis

Zinc is an essential trace metal for DNA synthesis, wound healing and protein synthesis. Zinc absorption occurs in the duodenum and proximal jejunum (in competition with copper).

• Zinc deficiency occurs as a result of the bypassed proximal small bowel and is more noticeable 2 to 3 years after surgery.

Vitamin D deficiencies are the most common, which may occur in up to 90% of patients.

It is also estimated that 50-80% of patients may be vitamin D deficient before bariatric surgery.

This may be due to:

• Inadequate sunlight exposure, patients participating in sedentary indoors activities
• Reduced liver hydroxylation
• Dietary deficiencies or poor absorption (due to loss of absorption of fat soluble vitamins from the intestine

Low calcium may be a result of:

• Reduced dietary intake
• Reduced gastric acid production
• Reduced absorption from the bypassed duodenum and proximal duodenum
• Reduced calcium absorption due to vitamin D deficiency and secondary hyperparathyroidism

Other mineral deficiencies include magnesium, folate, vitamin A, B1 and B6.

Vitamin B1 (thiamine deficiencies)

• Absorption is from the jejunum
• After bypass surgery and poor nutrition (eg. alcohol abuse and persistent vomiting), thiamine deficiencies is common

Symptoms may include:

• Neuro-muscular disorders, learning difficulties, impaired short term memory, coma
• Serious cases of Beri-Beri can affect the heart, peripheral and central nervous system

Vitamin B6 (pyridoxine)

On the  contrary excessive replacement of vitamin B6 should be avoided to prevent neurological symptoms

Selenium

The organic source of selenium is mainly from cereals, eggs, fish, meat and Brazil nuts

Selenium is absorbed in the duodenum and proximal jejunum by chelating/binding to organic and amino acids

The inorganic selenium (selenate, selenite) in supplements and food fortifiers are less readily absorbed

• Deficiency may lead to cardiomyopathy (Keshan disease), osteo-athropathy, thyroid gland dysfunction, cretinism, immune suppression, male infertility and hypercholesterolaemia

On the contrary high levels of selenium may lead to gastro-intestinal upsets, hair loss, fatigue, irritable and nerve dysfunction

Changes in bone metabolism after gastric bypass

After a gastric bypass, there is a significant increase in osteoclast activity after 1 year. There is a significant bone resorption in the year after the gastric bypass. Post-menopausal women are more likely to have an increase in slerostin activity compared to the pre-menopausal group after the gastric bypass surgery, with an increased rate of bone loss.

Definitely compare to the sleeve gastrectomy, the gastric bypass:

• Is more likely to result in lower serum calcium and 25-hydroxy vitamin D, a higher level of phosphorus and parathyroid hormone (PTH).
• Bone strength/density is more likely to be reduced and secondary hyperparathyroidism is more common after a gastric bypass.

This may lead to:

• Accelerated bone remodelling, increased bone turnover, decrease bone mineral density, osteomalacia, osteoporosis and pathological fracture.
• Hence sometimes it is advisable for post menopausal women who is at risk for osteopenia or osteoporosis to avoid the gastric bypass procedure.

PTH stimulate kidney synthesis of vitamin D, which then becomes part of the negative feedback loop.

PTH increases serum calcium and suppress phosphate metabolism.

Vitamin D increase calcium and phosphate metabolism, to provide minerals for bone formation.

After a gastric bypass, some endocrinologist and dietician recommend lifelong calcium and vitamin D supplements.

1000 IU vitamin D per day (maybe even larger doses for at risk patients)

1200 – 2000mg calcium per day

Post op supplements

The American guidelines suggest that the RYGBP patients should receive at least 3 000 Units of Vitamin D and 2.4g calcium citrate, as well as the usual iron and multivitamin supplements.

With the OAGB patients, possibly more iron and calcium supplements are needed because of the exclusion of the proximal small bowel.

• Copper and zinc levels should be checked as well.

Patients with a longer bilio-pancreatic limb (>250cm) are more at risk for iron, vitamin B12 and vitamin D3 deficiency.

• Hypoalbuminaemia may result in the development of non alcoholic steatohepatitis (NASH).
• Acute liver failure with severe protein deficiency may lead to increased mortality.

Obese patients, especially sedentary (lack of mechanical loading to the joints) patients with lack of sunlight exposure are already at risk for low vitamin D levels and elevated parathyroid hormone levels.

• Secondary hyperparathyroidism may be exacerbated by the malabsorptive state.
• Vitamin D supplements may help to reduce bone loss, reduce secondary hyperparathyroidism and the risk of fractures.

Post op gallstone

Obese Caucasian female patients in the 30-40 years age group are more likely to have gallstones (even before bariatric surgery).

After bariatric surgery the estimated incidence of developing gallstones may be 30-45%

The higher the weight loss result, the higher the risk (> 2 times) for developing cholesterol gallstones

• This may be due to altered bile chemical composition (usually an imbalance between cholesterol, bile acids and lysolecithin)
• After surgery the liver increase the secretion of cholesterol, reduce the secretion of bile salts and lecithin
• Gallstone formation may be due to gall bladder hypomotility, increase nucleating factors for gall stones and change in the gastro-intestinal hormones after weight loss surgery
• Genetic variation in the enzyme HMG Co-A reductase gene (which normally lowers LDL-cholesterol) may also contribute to gall stone formation

Perhaps up to 15% of patients develop symptomatic biliary colic within 2 years.

Most people who develop biliary colic ends up having a cholecystectomy.

Some patients take statin medications for high cholesterol

• In theory statin medications may reduce the liver synthesis of cholesterol and may reduce gall stone formation
• However it is uncertain whether these medications reduce gallstones or cholecystectomy rates
• Similarly it is not certain whether ursodeoxycholic acid will help to prevent cholecystectomy

However complications such as common bile duct stones, obstructive jaundice and biliary pancreatitis can be very difficult to manage.

After OAGB and RYGBP, a standard ERCP will not be possible due to the bypassed proximal small bowel and altered anatomy

Gastric cancer risk

In theory, in the long term there may also be a risk for gastric remnant cancer, which can’t be screened with gastroscopy because the stomach is excluded. We do not know whether this will be a common problem for our patients in Western societies.

Diagnosis is difficult, often delayed, the cancer is in the more advanced stage, treatment is more difficult and hence the prognosis is less favourable.

Summary

For most Australian patients, the most popular bariatric procedure is still the laparoscopic sleeve gastrectomy. This is a very versatile procedure which still offers the patient the option of future revision surgery to convert the sleeve to OAGB, RYGBP, SADI-S or others.

Some patients may choose to have the OAGB as a stand alone primary weight loss procedure rather than a second stage procedure.

• Because the OAGB is more effective with greater %EWL in the long term, remission of T2DM and dyslipidaemia compared to the LSG.
• But it requires long term follow up, may have more nutritional side effects and complications in the future.

The OAGB has a proven safety and efficacy record. It has similar post op complications rate (for leaks and bleeding as the sleeve).

The specific issues with the OAGB are mainly related to marginal ulcers, bile reflux and nutritional/vitamin deficiencies.

For patients who suffered from acid or alkaline/bile reflux, it is probably advisable for them to avoid the OAGB and have a RYGBP instead.

Final note:

The primary end point is still weight loss.

• Take nothing away from this important goal of bariatric surgery, significant long term maintained weight loss (>50% excess weight loss beyond 5 years) is the target and this is still the desirable primary outcome.

However the secondary end point may be more important for some patients

• The amount of weight loss alone is not the only important factor, the focus should be on the improvement in health outcomes such as remission or partial resolution (reduce medications use)  for hypertension, diabetes or dyslipidaemia, improvements in obstructive sleep apnoea and other medical co-morbidities associated with obesity.

• Improvements physiology states (improvements in vascular endothelium, reduced inflammatory state, reduced advanced atherosclerosis) on a microscopic level.
• Decrease morbidity and mortality from complications of diabetes, coronary artery disease, etc. in the future on a macroscopic level.
• Improved physical fitness or exercise tolerance, better sense of well-being, self confidence, body image and quality of life.
• As well as multiple associated lifestyle benefits, such as social and employment opportunities.

Personally I believe the secondary end point is far more important than weight loss outcome alone.

We also need to look at the bigger picture rather than statistics alone. The qualitative not quantitative outcome is often far more important. Hence before any weight loss surgery, the patient needs to set realistic and important goals with their family, general practitioners, physicians and surgeon.