Bariatric Surgery: Physician Quick Reference

Introduction

This is a physician-facing reference for preparing patients for, and following them after, bariatric surgery in the Western Zone. It covers obesity classification and staging, surgical candidacy, pre-operative assessment and workup, peri-operative medication considerations, and the post-operative laboratory schedule for both sleeve gastrectomy and Roux-en-Y gastric bypass.

Section 1 · Pre-Operative Assessment

Classification & staging

A. Obesity classification (WHO / Obesity Canada)

Enter weight and height (any units) to calculate BMI and obesity class automatically.

B. The 4 M’s framework

Assess each patient across all four domains prior to referral (Obesity Canada).

C. Edmonton Obesity Staging System (EOSS)

Surgical candidacy is generally considered at EOSS Stage 2–3. Stage 4 may require careful risk–benefit analysis.

Section 1D

Surgical criteria & procedures

Indications for bariatric surgery (Obesity Canada guidelines):

• BMI ≥40 kg/m² (Class III), or
• BMI ≥35 kg/m² (Class II) with at least one obesity-related comorbidity (T2DM, OSA, HTN, NAFLD, GERD, dyslipidemia, PCOS, OA), or
• BMI 30–34.9 kg/m² with poorly controlled T2DM (case-by-case)

Section 1E

Medications to consider pre-operatively

Section 1F

Pre-operative workup

Routine bloodwork

• CBC, electrolytes, Cr, eGFR, fasting glucose, HbA1c
• Lipid panel (TC, LDL, HDL, TG)
• Liver panel (AST, ALT, ALP, GGT, bilirubin, albumin)
• TSH
• Iron studies (ferritin, serum iron, TIBC, transferrin saturation)
• Vitamin B12, folate, 25-OH vitamin D, calcium, PTH
• Vitamin A, vitamin E, zinc, copper (especially if RYGB planned)
• INR/PT if liver disease suspected
• Fasting insulin (optional, if assessing insulin resistance)
• HBsAg, anti-HCV, HIV (per institutional protocol)

EGD (esophagogastroduodenoscopy)

• Recommended pre-operatively, particularly if RYGB planned (stomach becomes inaccessible post-op)
• Assess for Barrett’s esophagus, hiatal hernia, ulcers, gastritis, H. pylori
• Biopsy for H. pylori — if positive, treat and confirm clearance before surgery

H. pylori testing

• Test all patients pre-operatively (serology, stool antigen, or biopsy via EGD)
• If positive: eradication therapy (e.g., PPI + clarithromycin + amoxicillin × 14 days, or bismuth quadruple therapy)
• Confirm eradication with urea breath test or stool antigen ≥4 weeks after treatment

Additional investigations

• ECG (baseline, especially with cardiac risk factors)
• Sleep study / polysomnography if OSA suspected — initiate CPAP pre-op if positive
• Abdominal ultrasound (cholelithiasis, NAFLD assessment)
• Chest X-ray (per anesthesia requirements)
• DEXA scan if osteoporosis risk factors present

Section 1G

Binge eating disorder (BED) screening

Screen all candidates for BED prior to referral. Untreated BED is associated with poorer surgical outcomes and higher risk of weight regain.

Screening tools

• BEDS-7 (Binge Eating Disorder Screener-7) — brief, self-report; a positive screen warrants further assessment
• Binge Eating Scale (BES) — score ≥17 suggests moderate BED; ≥27 severe
• LOCES-Brief (Loss of Control over Eating Scale, 7-item) — validated in bariatric populations; predicts post-operative eating outcomes
• QEWP-5 (Questionnaire on Eating and Weight Patterns-5)
• Clinical interview: frequency of binge episodes, loss of control, distress, compensatory behaviours

If BED identified

• Refer to psychiatry/psychology with eating-disorder expertise
• Consider CBT, DBT, or interpersonal therapy pre-operatively
• Pharmacotherapy: lisdexamfetamine (Vyvanse) — Health Canada approved for moderate–severe BED; topiramate (off-label); SSRIs for comorbid depression
• BED does not necessarily preclude surgery, but should be stabilized pre-operatively
• Consider GLP-1 or GIP/GLP-1 therapy for other obesity complications and monitor BED symptoms
• BED may resolve after surgery, or may arise post-operatively in those without prior history

Section 1H–I

Cancer screening & NSAID avoidance

H. Routine cancer screening (ensure up to date)

Post-surgical anatomy (especially RYGB) may limit future endoscopic evaluation — complete all age-appropriate cancer screening prior to surgery.

I. NSAID avoidance

Section 1J–L

Lifestyle, mental health & dietitian referral

J. Smoking & alcohol cessation

Smoking

• Complete cessation required minimum 3–6 months pre-operatively; confirm with urine cotinine if needed
• Smoking increases risk of anastomotic leak, marginal ulcers, DVT/PE, and impaired wound healing
• Offer NRT, varenicline (Champix), bupropion, and cessation counselling

Alcohol

• Screen with AUDIT-C or CAGE
• Post-bariatric patients are at increased risk of AUD due to altered metabolism (faster absorption, higher peak BAC, reduced first-pass metabolism — especially post-RYGB)
• If current AUD or heavy use: refer for addiction support; surgery may be deferred until stable sobriety is demonstrated
• Counsel on lifelong moderation/abstinence post-operatively

K. Mental health assessment

• Screen with PHQ-9 (depression) and GAD-7 (anxiety)
• Assess for PTSD, trauma history, self-harm, suicidality; evaluate relationship with food, emotional eating, night eating syndrome
• Ensure realistic expectations regarding surgical outcomes; psychiatric/psychological clearance per program protocol
• Stabilize active untreated psychiatric illness before proceeding
• Post-bariatric patients have elevated suicide risk — ensure ongoing mental health follow-up

L. Dietitian referral

• Refer to a registered dietitian (RD) with bariatric expertise at the time of surgical referral — use the Western Zone Care Map to find local dietitian availability
• Pre-operative RD assessment: nutritional status, eating patterns, food security, disordered eating, supplement review
• Pre-operative diet education: total meal replacement (TMR) protocol, post-op dietary stages (clear → full liquids → pureed → soft → regular)
• Review the WZON Nutrition Guide for Bariatric Surgery with the patient
• Post-operative RD follow-up recommended at 4 weeks, 8 weeks, and 6 months

Section 2 · Post-Operative Follow-Up Labs

Post-operative laboratory schedule

A. Post–sleeve gastrectomy (SG)

B. Post–Roux-en-Y gastric bypass (RYGB)

C. Key post-operative reminders

• NSAIDs — permanently contraindicated
• Alcohol — strongly discourage; altered metabolism increases AUD risk
• Smoking — lifelong cessation; ongoing ulcer and complication risk
• Mental health — ongoing monitoring; elevated suicide risk; ensure continued follow-up
• Pregnancy — avoid for 12–18 months post-op; ensure reliable contraception; monitor nutrition closely if pregnancy occurs
• Dumping syndrome (RYGB) — educate on avoiding high-sugar/high-fat meals
• Supplements — lifelong bariatric multivitamin + calcium citrate + vitamin D + B12 (sublingual or IM if malabsorptive) + iron as needed
• Dietitian follow-up — RD at 4 weeks, 8 weeks, 6 months, and as needed thereafter

Pre-Operative Checklist

Bariatric surgery pre-operative checklist

A working checklist for the initial evaluation and preparation phases. See the sections above for detail.

Classification & assessment see Sections 1A–C ›

Complete the BMI calculator, the 4 M’s, and select an EOSS stage in Sections 1A–C. The results carry down to the assessment summary at the end of this checklist.

Mental health considerations see Section 1K ›

• Binge eating
• Depression
• Anxiety
• Alcohol dependence
• Smoking / vaping
• PTSD or trauma history
• Realistic expectations discussed

Referrals to consider see Sections 1K–L ›

• Registered dietitian
• Psychiatry / psychology
• Sleep study
• Addiction services
• Eating disorder specialist
• Kinesiology

Dietitian & nutrition see Section 1L ›

• RD assessment completed
• Total meal replacement education
• WZON Nutrition Guide reviewed
• WZON Bariatric Surgery Guide reviewed

Lifestyle & cessation see Section 1J ›

• Smoking cessation ≥3–6 months
• Alcohol use addressed
• Mental health stable
• BED stabilized pre-op (if applicable)
• Movement encouraged

Initial bloodwork see Section 1F ›

• CBC, lytes, Cr, eGFR, fasting glucose, HbA1c, lipid panel, liver panel, TSH, iron studies
• B12, folate, 25-OH vit D, calcium, PTH
• Vitamin A, E, zinc, copper (esp. if RYGB)
• INR/PT
• HBsAg, anti-HCV, HIV
• H. pylori stool antigen

Investigations see Section 1F ›

• EGD (esp. if RYGB planned)
• H. pylori treated if positive
• ECG
• +/– abdominal ultrasound
• Chest X-ray
• Sleep study / CPAP initiated
• DEXA scan (if osteoporosis risk)

Follow-up schedule (months) see Section 2 ›

• Family doctor: 1, 3, 6, 12
• Dietitian: 1, 2, 6, 12 (plus 1 week post-op)
• Surgeon: 1, 6, 12
• Consider: psychology, kinesiology, other allied-health support

Assessment summary

Read-only — auto-filled from the BMI calculator and EOSS selector in Section 1.

Based on the Obesity Canada Clinical Practice Guidelines (2020; updated 2024). A Western Zone Obesity Network resource. Created by Michael Mindrum, MD and Victoria Bentley, MD · Last updated March 2026.