Bariatric surgery workup

Section: UGI Sub-section: Bariatrics Curriculum: Curriculum, page 83

Definition

• Abnormal or excessive fat accumulation that presents a risk to health

Incidence

• Global epidemic with numbers increasing over time
• NZ (2006-2007)
  • Adults
    • 30% Obese (50% Māori, 70% PI, 10% Asian)
  • Children
    • 20% Overweight, 10% Obese
• Causes more deaths/ year than Breast & Colorectal Cancer combined
• After tobacco use, second leading cause of preventable death
• Second most common cause of preventable cancers
• Leading cause of mortality in obese pts
  • Morbid obesity is associated with a decreased life expectancy
  • 4yrs (F) and 7yrs (M)
• Males have a tendency for abdominal fat distribution
• Females → Gluteal / peripheral

Measures of Obesity

• BMI
  • Generally accepted measure of degree of overweight
  • Easy, reliable and reproducible
  • Correlates well to % body fat and body fat mass
    • Better estimate of body fat than weight alone
  • Beware
    • May overestimate degree of adiposity in highly muscular individuals
    • May underestimate adiposity in aging with loss of muscle mass
  • BMI classification categories are based on risk of cardiovascular disease
    • Different cut offs for different ethnicities, and have higher/lower cardiac risk at same BMI

WHO classification

Category	BMI (kg/m2)
Underweight	< 18.5
Normal weight	18.5 – 24.9
Overweight	25.0 – 29.9
Obese (Class I)	30.0 – 34.9
Obese (Class II)	35.0 – 39.9
Obese (Class III)	≥ 40.0

• Waist Circumference
  • Measurement with flexible tape placed on horizontal plane at the level of the iliac crest
  • At the end of normal expiration
  • Assessment of abdominal obesity
    • Indicative of cardio/metabolic risk
  • Utility lies in the BMI 25-35 range
    • Above this, almost guaranteed to have waist circumference over cut-off
  • Abnormal
    • ≥ 102cm males
    • ≥ 88cm females
  • Provides independent risk information that is not accounted for by BMI
  • Increased risk for
    • Heart disease
    • Diabetes
    • HTN
    • Dyslipidaemia
    • NASH
    • Mortality

Aetiology

• Regulation of energy homeostasis is complex and multifactorial
  • Related to multiple genetic and environmental factors
• Increase in body fat requires:
  • Energy intake to be increased over energy expenditure, for an extended period
  • However, feedback mechanisms between energy intake and expenditure
    • Weight gain promotes increased expenditure
    • Weight loss associated with decreased expenditure
      • Mechanism to defend against further weight loss, body “defends its fat”
• Environmental factors
  • Sedentary lifestyle
  • Cheap calorie dense foods
• Genetic + Hormonal control
  • Lack of satiety
    • ? Leptin resistance, ? Reduced Leptin production
    • Ghrelin + CCK involved in increased hunger (fundus and prox small bowel)
    • GLP-1 and Peptide YY induce satiety
  • Incompletely understood genetic factors
    • ↓ Thermogenic response to meals
    • ? Abnormally high set point for body weight
• Central melanocortin system plays a role
  • Gene mutation MC4R

Pathophysiology of Gut Hormones and Obesity

Excess body weight arises from a complex interplay of signals within the gut-brain-endocrine axis, leading to a chronic imbalance between energy intake and expenditure. Contributing factors include:

• Genetic: Inherited traits influencing appetite regulation, metabolism, and fat storage
• Environmental: Availability of energy-dense foods, reduced physical activity, and sedentary lifestyle
• Sociocultural: Dietary habits, socioeconomic status, and cultural attitudes towards food and body weight
• Inflammatory: Adipose tissue, particularly in obesity, secretes pro-inflammatory adipokines (e.g. TNF-α, IL-6) and leptin in proportion to fat mass, leading to chronic low-grade inflammation and leptin resistance
• Metabolic: Inflammation-induced impairment of insulin signalling results in insulin resistance and other metabolic complications (e.g. dyslipidaemia, type 2 diabetes)
• Endothelial dysfunction: Chronic inflammation and insulin resistance contribute to impaired endothelial function, increasing cardiovascular risk
• Gut hormone dysregulation: Increased levels of orexigenic hormones such as ghrelin and neuropeptide Y (NPY) enhance hunger and food intake, while reduced levels or resistance to anorexigenic hormones like GLP-1 and CCK impair satiety and delay gastric emptying

Ghrelin

• “Hunger hormone”
• Produced by enteroendocrine cells
  • Mostly stomach (fundus) and duodenum
  • Also in jejunum, lungs, islet cells, adrenal, placenta, kidney
• Receptor
  • Growth Hormone Secretagogue Type 1a receptor (GHS-R)
  • Hence name GHRelin
• Action
  • Stimulates food intake (number of meals) and motivation to find meals
    • Activates cells in Anterior Pituitary, and Arcuate Nucleus (Hypothalamus)
      • Activate Growth Hormone and Neuropeptide-Y
    • Increases body weight and fat mass
  • Decreases sensitivity of Vagal afferents
    • Less sensitive to Gastric Distension
  • Increases motility and gastric acid secretion
  • Regulates reward cognition, learning and memory, sleep/wake cycle, glucose metabolism
• Blood levels of Ghrelin highest pre-meals, low post meals
• NB: Ghrelin levels in obese individuals is low
  • Higher in lean individuals
  • Highest in those with anorexia nervosa, and cancer-induced cachexia
  • Ghrelin may not be a driver for obesity (Except Prader-Willi syndrome)
• Sleeve gastrectomy will decrease plasma Ghrelin levels by 60%
  • Unclear evidence to say if ghrelin returns to normal levels over time

Leptin

• Produced by adipose cells and small intestine enterocytes
• Regulates energy balance by inhibiting hunger
  • Decreased fat storage in adipocytes
• Works on receptors in the Arcuate Nucleus, and other locations in the Hypothalamus
• Obese individuals have a decreased sensitivity to Leptin
  • Leads to decreased satiety despite high energy stores and high levels of Leptin
  • Similar to insulin resistance in T2DM

Glucagon-Like Peptide-1 (GLP-1)

• Produced by enteroendocrine L-cells
• Main action - Acts as an incretin
  • Decreases BSL
    • Glucose-dependent increased insulin secretion
    • NB: Preserved in T2DM
• GLP-1 receptors on Brainstem & Hypothalamus
  • Promotes satiety
• GLP-1 Receptors in the stomach
  • Decreased gastric emptying and motility
  • Decreased acid secretion

Cholecystokinin (CCK)

• Peptide hormone secreted by enteroendocrine I-Cells in Duodenum + Jejunum
  • Released rapidly in response to a meal
  • Fatty acids and amine acids in chyme entering duodenum
• Actions
  • Stimulates digestion of fat and protein
  • Stimulates pancreatic acinar cells
    • Release of digestive enzymes
  • Increases hepatic bile production Stimulates gallbladder contraction and Sphincter of Oddi relaxation
  • Decreases gastric emptying
    • Via CNS, and Vagal stimulation
  • Proposed mechanism for hunger suppression
    • Essentially opposes the Ghrelin action on Vagus

Peptide YY (P-YY)

• Short amino acid released from Ileum and colonic cells in response to feeding
• Acts to reduce appetite
  • Anorexigenic
• Inhibits gastric motility and emptying
• Increases water and electrolyte absorption in the colon
  • May also inhibit pancreatic secretion
• May be used as alternative to Leptin for weight loss
  • Don’t get the same resistance in obese people as you do for Leptin

Associated Co-morbidities

• NASH, Hyperlipidaemia
• DVT – hypercoagulability
• Venous stasis – ulcers
• Hormone imbalance → Dysmenorrhoea, Hirsutism, Infertility, PCOS
• Gallstones
  • If present consider cholecystectomy during bariatric surgery
  • If absent consider ursodeoxycholic acid treatment for 6 months post-op
• Cardiac - CM, Right HF, Pulmonary HTN
• Cancer
• Psychosocial
• Metabolic Syndrome

Hepatic steatosis

• NAFLD/MASLD
  • Presence of hepatic steatosis in the absence of causes of secondary hepatic fat accumulation
  • E.g Heavy EtOH
• NASH/MASH
  • Hepatic steatosis with associated hepatocyte ballooning degeneration and hepatic inflammation
  • Can have features of cirrhosis
  • Histologically indistinguishable from EtOH cirrhosis
• Incidence high in bariatric patients
  • 37% NASH, 1-7% Cirrhosis
  • Bariatric surgery can potentially reverse
  • But some at risk of decompensated liver failure

Association With Cancer

• Excess weight associated with increased risk of multiple cancers
  • Estimated cause of up to 40% of cancers
  • Can also increase the risk of dying from cancer
• Strong evidence supporting link with:
  • Endometrial
  • Renal
  • Oesophageal and Gastric (cardia)
  • Colon and Rectum
  • Biliary
  • Pancreas
  • Breast
  • Ovarian
  • Multiple Myeloma
  • HCC

Metabolic Syndrome

• Cluster of multiple medical conditions that may increase risk of cardiovascular disease or developing diabetes
• Need 3/5 of
  • Abdominal obesity
  • Hypertension
  • Hyperglycaemia
  • Impaired hepatic insulin uptake, systemic hyperinsulinaemia, and tissue resistance to insulin
  • Hypertriglyceridaemia
  • Low HDL
• Thought linked to impaired hepatic glucose uptake
• Associated with PCOS, OSA etc.

Classification of Obesity

• Uses BMI
• Based on ranges of cardiovascular risk

Management of Obesity

Goals of Treatment

• Prevent, treat, or reverse complications of obesity AND…
  • Increase quality of life
  • Health benefits reported with as little as 5% of TBW
• Expected benefits
  • Lifestyle measures: 5-7% TBW
    • Often difficult to maintain
  • Pharmacologic: 5-10% TBW
  • Bariatric surgery often needed if 30% TBW wanting to be lost

Identifying Candidates for Therapy

• Assess patients
  • Degree of overweight (BMI and waist circumference)
  • Presence of CVS risk factors (HTN, DM, Hyperlipid)
  • Other comorbidities (OSA, NAFLD etc)
• Little or no risk (BMI 20-25)
• Low Risk (BMI 25-29.9 without other CVS risk factors)
  • Counsel on preventing weight gain, basic dietary advice
• Moderate Risk (BMI 25-29.9 with CVS risk factor, or 30-34.5)
  • Offer intensive behavioural intervention
  • Can consider pharmacologic therapy
• High Risk (BMI 35-40+, especially younger patients)
  • Offer intensive behavioural therapy, pharmacologic therapy, and consider bariatric surgery
• In 2022, the American Society of Metabolic and Bariatric Surgery (ASMBS) and the International Federation for the Surgery of Obesity and Metabolic Disorders (IFSO) published the following guidelines
  • Body mass index (BMI) ≥35 kg/m2 (Class 2 and higher) regardless of comorbidities
  • BMI between 30.0 and 34.9 kg/m2 (Class 1) and type 2 diabetes
  • BMI between 30.0 and 34.9 kg/m2 who cannot achieve substantial or sustainable weight loss or comorbidity improvement with nonsurgical weight loss methods.
• NICE guideline
  • BMI 40+
  • BMI 35+ with complications
  • BMI 30+ with poorly controlled diabetes

Initial Treatment

• Comprehensive lifestyle intervention
  • Dietary therapy
  • Exercise
  • Behaviour modification
• Programs that include the above:
  • Self-management
  • Individual case managers
  • Group sessions
  • Individualised adherence strategies
  • Networks for feedback and clinical/emotional support
• Average TBW loss is approx. 4%
  • Maintaining this weight loss is difficult

Dietary Therapy

• Many types of diets
  • Balanced low calorie
  • Low fat/low calorie
  • Moderate fat/low calorie
  • Low carbohydrate
  • Mediterranean diet
• Diet adherence is important predictor of weight loss, regardless of type
  • Should tailor diet to what pt will tolerate
    • Focus on reducing intake below expenditure, not worrying about specific composition
• Most adults will lose weight if calorie intake <1000 kCal/day
  • Severe caloric restriction may lose weight faster, but
    • 400kCal vs 800 kCal showed no difference in weight loss
  • Difficult to maintain very low cal diets
    • Body adapts to starvation

    • 800kCal/day recommended

• Need continued monitoring for progress
  • If < 5% TBW loss at 6 months, try different approach
• Difficulty with diets is maintaining weight loss and the body’s adaptation to dieting
  • Generally prevents dieting alone as being a viable long term strategy

Exercise

• Less potent than dietary restriction
  • But physical activity is strong predictor of long term weight loss maintenance
• Aim is 30+mins, 5-7x days per week
  • Prevents weight gain and improves CVS health
• Multicomponent program preferred
  • Aerobic and resistance exercise
• Need to take into account
  • Medical conditions
  • Age
  • Preferences for types of exercise

Behavior Modification

• Behavioural therapy/modification is cornerstone of obesity therapy
• Goal - Help patients make long term changes in eating behaviour by
  • Modifying and monitoring food intake
  • Modifying physical activity
  • Controlling cues and environmental stimuli that trigger eating

Pharmacologic Management

• Consider in those with BMI > 30, or 27-30 with weight related comorbidities
  • Who have not met weight loss goals with comprehensive lifestyle intervention
• Single agents preferred vs combination therapy
  • Choice depends on preference, adverse effects, patient comorbidities, costs etc
• Liraglutide
  • Usually first line
• Orlistat
  • Often second line
• Phentermine
  • Also widely prescribed option

Liraglutide (Saxenda)

• Glucagon-Like Peptide-1 Receptor Agonist
  • Chemically modified version of human GLP-1
  • Stimulate glucose dependent insulin secretion
  • Inhibits Glucagon release
  • Inhibits gastric emptying
• Usually given in higher doses than for diabetes
  • 3mg daily, subcut daily injection, needs to be up titrated
  • Expensive ($5000 per year)
• Good for glycaemic control and weight loss
• Significant reduction in weight (2-4kg) compared to placebo
• Reduces major cardiac disease events in pts with T2DM and pre-existing CVS disease
• Adverse Effects
  • GI side effects – Nausea and vomiting due to decreased emptying
  • Hypoglycaemia
  • Less commonly – Pancreatitis, Gallstones, Renal Impairment
• NB: Association in rodents with Medullary Thyroid Ca
• Contraindications
  • Pregnancy
  • Personal or Fam Hx Medullary Thyroid Ca or MEN 2A/2B

Orlistat (Xenical)

• Lipase inhibitor
  • 120mg PO TDS
  • Alters fat digestion by inhibiting pancreatic lipases
    • Not completely hydrolysed, faecal fat excretion increased
  • Weight loss 5-10kg (cf placebo 3-6kg)
    • Maintained for 24-36 months of treatment
  • Improves BP in hypertensive patients
  • Also serum lipid values
• Adverse Effects
  • GI – Borborygmi, cramps, flatus (with discharge) (15-30%)
  • Severe liver injury reported (13 cases in 40 million)
  • Lowers fat soluble vitamins
  • Renal injury – Oxalate stones related to malabsorption
• Contraindications
  • Pregnancy, Chronic malabsorption, Cholestasis, Hx of Ca Oxalate stones

Phentermine (Reductil/Duramine)

• Sympathomimetic drugs
  • Stimulates noradrenaline release or inhibits reuptake
  • Can increase blood pressure
  • Reduce food intake by causing early satiety (seratogenic effect)
  • Structurally similar to amphetamines
• Most often prescribed weight loss drug in the US
• Good efficacy (7-8kg vs 1kg placebo)
• Only approved for short term use (12 weeks)
• Potential side effects, potential for abuse, etc.
• Adverse
  • Tachycardia and hypertension
  • Insomnia, dry mouth, constipation, nervousness
• Contraindications
  • Coronary artery disease
  • Uncontrolled hypertension
  • Hyperthyroidism
  • History of drug abuse

Other medications

• Contrave - naltrexone/buproprion
• Semaglutide (Ozempic) - in New Zealand, it is approved by Medsafe for the treatment of type 2 diabetes. It’s not approved for weight loss.

Pre-Surgical Considerations

• Indications for Offering Bariatric Surgery
  • 18-65 years old
  • BMI > 35 or
  • BMI > 30 + Obesity-related complications
  • Failed other measures with previous serious attempts at weight loss
  • Pt well informed, compliant (understands post-op requirements) & motivated
  • Commits to long term follow up
  • Fit for anaesthesia
• Contraindications to Bariatric Surgery
  • Untreated mental health disorder / drug & alcohol abuse
  • Inability to comply with follow-up and vitamin replacement
  • Prohibitive anaesthetic risk
  • Unstable CAD
  • Uncontrolled OSA + Pulmonary HTN
    • Systolic pressure > 50mmHg
  • Cancer within the last 2 years / Active Ca
  • Portal HTN – Absolute
  • Crohn’s – relative
  • Connective tissue disease
  • Prader-Willi Syndrome
  • Concerns re: Pregnancy after bariatric surgery (due to nutritional deficiencies)
    • Should wait 2 yrs Post-op

Pre-operative Workup

• Always an MDT approach
  • Dietician, psychiatrist, physician, surgeon, nurse educator, anaesthetist, GP
• History and Exam
• Cardiovascular testing
• Pulmonary assessment
• Consider endocrine testing if Cushing’s/Hypothyroid suspected
• USS of Gallbladder
• Endoscopy – probably not routine, do if symptomatic

MDT Involvement

• Dietician
  • Assess nutritional status and aid in patient education about what to expect after surgery:
    • Up to 1/3 may have variable difficulty with eating
    • May result in regular vomiting or regurgitation of some food & limitation of the type of food
  • Small no. on pureed food for life
  • Will probably need to avoid bread, rice, pasta, red meat initially
  • Reduced alcohol tolerance
  • Bypass – B12, Iron, Folate
    • Monthly injection of B12
    • Use the gluconate form of iron as better absorbed in non-acid environment
  • Multivites for all
    • Calcium 2g/ day and possibly vitamin D
  • For malabsorptive think about fat soluble vitamins
• Psychologist
  • High prevalence of depression, anxiety, binge eating, night eating syndrome, PTSD, body dysmorphic disorder
  • 50% on psychotropic medications
  • Assess readiness for change
  • Realistic expectations
• Surgeon
• Exercise physiologist/trainer
• Anaesthetist
• Nurse educator
• GP

History and Exam

• Obesity history
  • Duration
  • What attempts at weight loss
  • Implications of obesity on life
  • Hx of cardio/resp function
• PMHx
  • ? Obesity related comorbidities
  • ? Previous surgery

Cardiovascular Testing

• Simple – Exercise tolerance
• Walk 4 blocks or up 2 flights of stairs
• CPEX if borderline
• If symptomatic consider dobutamine stress ECHO and further cardiac workup
• Usually guided by anaesthetist

Pulmonary Assessment

• Look for OSA
  • Routine pre-op sleep questionnaire
  • +/- Sleep study
  • May need pre-op CPAP
    • Reduce hypercarbia, hypoxemia & pulmonary artery vasoconstriction
  • May be a significant cause of mortality
    • Apnoea → Hypoxemia → Sympathetic discharge → Lethal arrhythmias
• Reactive asthma
• Obesity Hypoventilation Syndrome (Pickwickian Syndrome)
  • Awake alveolar hypoventilation, with daytime hypercapnoea as a result of diminished respiratory drive and capacity, related to obesity
    • Super-obese
    • May appear cyanotic
    • PaCO2 > PaO2
    • Book to ICU

Gallbladder USS

• Not routinely recommended
• If has gallstones, could consider taking out gallbladder at same time
  • Esp. if duodenal switch or RYGB
• Recognised that weight loss predisposes to gallstones
  • Incidence post-bypass = 30%
• Some surgeons say take GB if doing malabsorptive procedure but not needed if doing restrictive
• Treating with Ursodeoxycholic acid post-operative may reduce stone formation
  • Ursodiol 300mg po BD

Gastroscopy

• Recommended
  • Mandatory if symptoms, reflux etc
• Main reason is if significant Barrett’s present, then would recommend against a sleeve and towards RYGB

Planning/Interventions to Prevent Peri-operative Risk

• Obesity Surgery Mortality Risk Score
• Optifast
• Glycaemic Control – Aim BSL < 15, HbA1c < 53
• Smoking Cessation – Minimum 8/52 prior
• DVT prophylaxis
• Anaesthetic issues
• Pneumoperitoneum
• Equipment planning, special beds, positioning, special instruments/ports
• Peripheral Nerve Injuries
• ICU post-op

Obesity Surgery Mortality Risk Score

• Prospectively validated scoring system to evaluate mortality risk after bariatric surgery
  • Risk Factors
    • Age > 45
    • Hypertension
    • Male
    • BMI > 50
    • Risk factors for PE
      • Prev VTE, Pulmonary HTN, IVC filter, Obesity hypoventilation

Optifast

• 3 sachets per day + very low calorie diet
  • Aim 450-800kCal/day
• Can reverse NAFLD or NASH
  • Obese individuals have 30-100% NAFLD
• Trials have shown 6/52 course of optifast reduces liver volume by 15% and liver fat content by 43%
• Helps intra-operative liver pliability
  • Especially for gastric bands

DVT Prophylaxis

• Obesity is an independent risk factor for VTE
  • Risk accentuated by pneumoperitoneum & peri-op hypercoagulability
    • Increased fibrinogen, factor VIII & vWF
• Mitigate this by
  • Early ambulation
  • Pneumatic compression stockings
  • Clexane or heparin
  • In high risk (previous DVT/PE, predisposition to hypercoagulable state) may need IVC filter

Anaesthetic Considerations

• Endotracheal intubation & airway management can be difficult – large neck circumference
• Sometimes use head up position initially as this optimises pre-oxygenation
  • No benefit once paralysed
• May need large BP cuffs
  • May need arterial monitoring if not working
• Venous access can be challenging
• May require larger doses of lipophilic substances
• Barbiturates, benzodiazepines

Pneumoperitoneum Factors

• Increased Systemic Vascular Resistance
• Decreased cardiac index
• Transiently increased MABP
• Can get
  • Bradycardic
    • Vagal response to peritoneal stretch
  • Hypotensive
    • Reduced venous return & relative hypovolemic from steep reverse-Trendelenburg response
• May cause transient oliguria from pressure on renal cortex & IVC
  • Has no long term consequence for kidney

Peripheral Nerve Injuries

• Must always consider
  • Stretch injuries of brachial plexus
  • Ulnar nerve compression from excessive abduction of arm
• NB: If polyneuropathy
  • Need to consider malnutrition

Consider ICU

• Risk factors for complicated stay
  • Male
  • BMI > 60
  • DM
  • OSA
  • Intra-op complications

Surgery

Expected Results

• More effective and durable than conventional weight loss management (Cochrane 2005)
• Swedish obese subject (SOS) study – 10yr cohort
  • 32% RR decreased of death at 10 yrs (mostly cardiovascular + ↓ co-morbidities)
  • Cost effective after 3-5 years
  • Better QOL, higher employment rate

Effects on Co-morbidities of Obesity

• T2DM
  • 80-90% remission with BPD/DS
  • 50-70% remission with bypass
  • 10-20% with banding
  • Attributed to decreased weight and change in GI hormones reaching the duodenum
• HTN
  • 60% cured, 25% improved
• Dyslipidaemia
  • 35% cured, 40% improved
• Metabolic syndrome
  • Cured in > 60% after bypass; NNT = 2.1
• Cardiovascular risk improved after bypass
• Improved fertility rate

Mechanism of Weight Loss

• Metabolic surgery results in anatomical alterations that produce physiological interactions involving signaling between the gut and brain.
  • It works by
    • Changing hormonal signalling
    • Changing neural signalling
    • Anatomical restiction
    • Malabsorption
    • Change in guit microbiome

Pathophysiology of obesity-related diseases

Gut brain-axis

• Enteroendocrine cells sense luminal factors, such as nutrients.
• EEC’s secrete gut hormones such as oxyntomodulin (OXM), and glucagon-like peptide 1 (GLP-1), which alert the CNS that nutrients are in the gut.
• Paracrine mechanisms (vagal, spinal afferents) also alert the CNS.
• This signaling acts on the hindbrain and hypothalamus to reduce food intake, increased energy expenditure, slow GI motility, and increase nutrient utilisation.
• Adipose tissue acts as an endocrine and immune organ.
• An increase in the adipose mass results in adipose tissue dysfunction.
• White adipose tissue produces immune factors such as leptin, adiponectin, growth factors, cytokines such as IL-6 an TNF - some of which are pro-inflammatory mediators and contribute to the obesity related complications.

Mechanism of weight loss post bariatric surgery

Hormonal signaling

• Patients have reduced food intake with decreased pre-meal hunger and increased satiety.
• Metabolic surgery increases the amount of post-prandial gut secretion of entero-endocrine hormones (GLP-1, GLP-2)
• Changes in nutrient concentrations, and higher nutrient loads to distal gut segments result in higher levels of peptides secreted by EEC’s which increase satiety.
• GLP-1 slows gastric emptying, inhibits glucagon release, and promotes insulin secretion from the pancreas.
• Ghrelin production (hunger hormone) is reduced.

Neural signaling

• Vagal nerve signaling increased which reduces food intake and hunger.

Gut microbiota

• After bariatric surgery, there is a change in gut microbiota which changes the energy utilisation of these microbes which may contribute to weight loss.

Bile acids

• Plasma bile acid levels a higher in patients after bariatric surgery.
• High bile acids correlate with lower post-prandial BSL.
• BA also promote other peptides including GLP-1 (which stimulates satiety)
• BA usually stay high for 3-4 years after surgery, and promote intestinal hypertrophy.

Behavioral

• Because of the above mechanisms, behavioural changes occur - with regards to food-reward pathway which further reduce weight loss.

• Restrictive Procedures

  • Limit calorie intake by reducing stomach reservoir capacity
  • Absorptive function of small intestine remains intact
  • Sleeve gastrectomy most commonly used
    • Success probably lies in neuro-hormonal effects on hunger control also
  • Others: VBG and Lap Gastric Bands

• Malabsorptive Procedures

  • Decrease the effectiveness of nutrient absorption by shortening the absorptive length of the small intestine
  • Either by bypass of small bowel absorptive area, or bypass of biliary/pancreatic secretions that facilitate absorption
  • E.g. Jejunoileal bypass and BPD
  • Often give profound weight loss, but offset by significant metabolic complications

• Combined Procedures

  • Roux-en-Y Gastric Bypass
  • BPD (Biliopancreatic Diversion) with Duodenal Switch
  • Also One-anastomosis Gastric Bypass and SADI (Single Anastomosis Duodenal-Ileal Switch)

Short Notes

Bariatric Surgery

• Indications

  • From ASMBS & IFSO (American Society for Metabolic and Bariatric Surgery & International Federation for the Surgery of Obesity and Metabolic Disorders

    • Anyone BMI >35

    • Metabolic disease BMI >30

    • Asians + metabolic disease BMI >25

    • Bridge to other treatment

      • Joint surgery >40

      • Ventral wall repair

      • Transplant

• Preoperative Considerations 

  • Service is offered through a specialised bariatric unit with availability of MDT 

    • Dietician

    • Psychologist

    • Specialist Nurse

    • Anaesthetist

    • Endocrinologist, Respiratory 

    • Surgeon

  • Patient Selection

    • All appropriate non-surgical measures have been tried and failed to achieve or maintain adequate weight loss for at least 6 months

    • No Surgical or Anaesthetic contraindications

    • Person willing to commit to long term follow up 

  • Choice of Operations

    • Weight of patient / required weight loss

    • Previous operations

      • Bariatric 

      • Non Bariatric

    • Reflux 

    • Gastroscopy

    • Comorbidities

  • Nutritional assessment

    • Thiamine, B12, Folate, Iron

    • Vitamin D, Calcium

    • Vitamins ADEK 

    • Zinc, Copper

  • Optimisation

    • Optimisation of comorbidities

    • Patient to institute changes that will be required post operatively

      • Stop smoking

      • Change to diet

      • Exercise 

  • Optifast

    • For 2 weeks before operation 

  • VTE prophylaxis 

• Non Surgical

  • Medical

    • Orlistat

    • Amphetamine derivatives 

    • Opioid antagonists

    • GLP-1 agonists

  • Endoscopic

    • Intragastric Balloon

    • Duodeno-jejunal sleeve

    • Gastric plication

• Surgical

  • Restrictive

    • Gastric Band

      • Operation

        • An inflatable silicon band fitted around the proximal stomach to create a pouch of 30mls

        • Lies 45o in the 8 to 2 o’clock position (Phi angle)

          • 10 to 60 degrees from vertebrae 

        • Secured by sutures

        • Band is connected to a subcutaneous insulation port

      • Complications

        • Early

          • Intraoperative

            • Gastric perforation or splenic Injury

          • Band too tight 

            • Pain, vomiting, dysphagia

            • Mx: Decompress band with Huber needle, there will be 4-11mls

        • Medium

          • Slippage 
 * Pain, vomiting, dysphagia
 * Can develop ischaemia of prolapsed fundus
 * CXR shows loss of Phi angle
 * Mx: Decompress then laparoscopic removal. 
 * Deflate band
 * Adhesiolysis from left lobe of h
 * Pseudo capsule of scar tissue 
 * Cut buckle with disposable scissors.
 * Release gastrogastropexy
 * cu and remove tubing
 * Leak test stomach with air or meth blue

        • Late 

          • Erosion 

            • Cellulitis around the port

            • Infection tracks from the stomach

            • No gastric perforation just band eroded through creating phlegmon

            • Diagnosis is endoscopic

            • Mx: Endoscopic cut the tubing and remove band. Remove tubing and port percutaneously

            • Do not need to need to manage fistula as so long

          • Mega-oesophagus

    • Gastric Sleeve

      • MOA

        • Restrictive and hormonal as removing fundus removes production of Ghrelin

      • Pros:

        • Easy to preform in super obese

        • No anastomosis risk

        • Normal intestinal absorption

        • Pylorus preserved so prevention of dumping

      • Cons: 

        • Irreversible

        • Subsequent weight gain 

      • Operation

        • Using a 34Fr bougie the Greater Curve side is stapled off to be removed

        • Ensure not too narrow at incisura

      • Complications

        • Early

          • Intraoperative 

            • Oesophageal, splenic injury

          • Staple line leak 

          • Staple line bleed

          • Intra-abdominal bleed

          • VTE

        • Medium

          • Sleeve too narrow or twists

          • Stricture

        • Late

          • GORD

          • Weight Gain

  • Malabsorptive

    • Single Anastomosis Bypass

      • MOA

        • Restrictive, malabsorptive and hormonal

      • Operation

        • Create a longer gastric pouch

        • Create Gastrojejunostomy

      • Pro

        • Fewer anastomosis 

        • Fewer internal hernias

      • Cons

        • Bile reflux

        • Malabsorption 

    • Roux-en Y Gastric Bypass

      • MOA

        • Restrictive, malabsorptive and hormonal

      • Operation

        • 30ml gastric pouch 

        • Roux limb 75-150cm in length

        • Then the Biliopancreatic limb and common channel

        • Both gastrojejunostomy and jejujejunostomy anastomosis

        • Close mesenteric defects

      • Complications

        • Early

          • Intraoperative injury

          • Leak

          • Obstruction

        • Medium

          • BP or Roux limb obstruction

          • Dumping Syndrome @

          • Blind End Syndrome

        • Late

          • Marginal Ulcer

          • Adhesional SBO

          • Internal Hernia

            • Where

              • Peterson’s Space

                • Between the Roux limb mesentery and transverse colon mesentery 

              • Mesenteric defect at the enteroenterostomy 

              • And if Roux limb is retrocolic then through the defect made in the transverse mesocolon

            • ↑ risk 

              • Patient looses weight 

              • Laparoscopic surgery 

              • Spaces not initially closed

              • Retrocolic jejunostomy 

              • Dissoluble suturres 

          • Nutritional 

          • Weight gain

    • Duodenal Switch

      • MOA

        • Malabsorptive, Restrictive, Hormonal

      • Operation

        • Gastric Sleeve

        • Divide stomach just distal to pylorus

        • Divide distal jejunum and this distal part anastomose with pylorus 

        • Anastomose the proximal length of the jejunum to ileum 1m from ileocaecal value

      • Cons

        • Extreme Malabsorption

• Intra-operative Considerations

  • Positioning 

    • Non slip mat and strap

    • Pressure area concern

    • Head up 

    • Legs apart

  • Ports

    • Need long ports 

    • Ports far away to help with angles

• Post operative Considerations

  • Observe for complications

    • Bleeding

    • Perforation

    • Dysphagia

    • VTE

  • Incentive spirometry

  • Clexane until mobile

  • PPI

  • Ensure managing fluid

  • Supported regime for building up diet

  • Supplementation 

  • Nutritional observation and support

  • At least annual bloods

    • FBC

    • Thiamine, B12, folate, Iron

    • Calcium, Vit D, PTH

  • Education that need 30mins exercise 


Operative: Internal Hernia

1. Start Laparoscopically

2. Start at IC Valve and run bowel proximally to find the JJ anastomosis

3. Then go to the GJ and run distally to find the JJ anastomosis

4. This will enable appreciation of where the mesentery of roux limb is relative to the transverse colon (Peterson’s)

5. Then from the JJ to the DJ along the BP limb

6. This should have allowed inspection of the JJ mesenteric defect and unraveled all hernias

7. If Identify a Gangrenous length of bowel 

   • Call for help or staple off and remove 

   • Must decompress the remnant stomach

   • NJT for roux limb decompression