Expert opinion on the preoperative medical optimization of adults with diabetes undergoing metabolic surgery

Table 1 Evidence grading system for recommendations

Level of evidence	Description
A	Clear evidence from well-conducted, generalizable randomized controlled trials that are adequately powered, including: Evidence from a well-conducted multicenter trial; Evidence from a meta-analysis that incorporated quality ratings in the analysis. Compelling nonexperimental evidence, i.e. "all or none" rule developed by the Centre for Evidence-Based Medicine at the University of Oxford. Supportive evidence from well-conducted randomized controlled trials that are adequately powered, including: Evidence from a well-conducted trial at one or more institutions; Evidence from a meta-analysis that incorporated quality ratings in the analysis
B	Supportive evidence from well-conducted cohort studies: Evidence from a well-conducted prospective cohort study or registry; Evidence from a well-conducted meta-analysis of cohort studies. Supportive evidence from a well-conducted case-control study
C	Supportive evidence from poorly controlled or uncontrolled studies: Evidence from randomized clinical trials with one or more major or three or more minor methodological flaws that could invalidate the results. Evidence from observational studies with high potential for bias (such as case series with comparison with historical controls); Evidence from case series or case reports. Conflicting evidence with the weight of evidence supporting the recommendation
E	Expert consensus or clinical experience

Table 2 Obesity classification system for adults: International and Asian

Category	WHO International classification BMI (kg/m2)	Asian classification BMI (kg/m2)
Underweight	< 18.5	< 18.5
Normal weight	18.5-24.9	18.5-22.9
Overweight	25.0-29.9	23-24.9
Obesity class I	30.0-34.9	25-29.9
Obesity class II	35.0-39.9	30-34.9
Obesity class III	≥ 40	≥ 35

BMI: Body mass index.

Table 3 Indications for metabolic surgery in obesity along with presence of diabetes

Condition	Glycemic status	Recommendation for metabolic surgery	Evidence category
Diabetes and BMI ≥ 40 kg/m2 (≥ 37.5 kg/m2 for Asians)	Any	Strong recommendation	A
Diabetes and BMI 35-39.9 kg/m2 (32.5-37.4 kg/m2 for Asians)	Uncontrolled despite optimal treatment	Moderate recommendation	B
Diabetes and BMI 30-34.9 kg/m2 (27.5-32.4 kg/m2 for Asians)	Uncontrolled despite optimal treatment	Weak recommendation	C, E
Diabetes and obesity (BMI – not defined) with comorbidities: Poorly controlled hypertension; Non-alcoholic fatty liver disease; Obstructive sleep apnea; Obesity hypoventilation syndrome; Osteoarthritis of the knee or hip; Urinary stress incontinence; Polycystic ovary syndrome; Gastro-esophageal reflux disease; Idiopathic intracranial hypertension; Severe venous stasis disease; Obesity-related limited mobility; Obesity-related poor quality of life	Any	Weak recommendation	E

BMI: Body mass index.

Table 4 Comparison between laparoscopic Roux-en-Y gastric bypass and laparoscopic sleeve gastrectomy, the two most commonly performed bariatric procedures, in patients with diabetes and obesity

	RYGB	LSG	Comments
Type of procedure	Combined malabsorptive and restrictive	Restrictive
Effect on weight loss	+++	+++	Most studies demonstrate comparable weight loss, with slight superiority of RYGB shown in some reports
Remission of diabetes	+++	++	RYGB superior to LSG
Short term glycemic improvement	+++	++	RYGB superior to LSG
Long term glycemic improvement	+++	++	RYGB superior to LSG
Improvement in hypertension	++	+	RYGB superior to LSG
Improvement in dyslipidemia	++	+	RYGB superior to LSG
Improvement in gastroesophageal reflux disease	++	+	RYGB superior to LSG
Postoperative complications	+	+/-	Postoperative complication and reoperation rates less with LSG than RYGB
Long-term nutritional deficiencies	++	+	LSG safer that RYGB

LSG: Laparoscopic sleeve gastrectomy; RYGB: Laparoscopic Roux-en-Y gastric bypass.

Table 5 Preoperative evaluation before metabolic surgery in individuals with diabetes and obesity

System	Essential evaluation	Conditional evaluation	Comments
History and physical examination	Detailed evaluation along with drug history	-	-
Glycemic	FPG, PPG, HbA1c, Fasting serum C-peptide	SMBG; CGMS	HbA1c < 7% is a reasonable target, higher targets may be acceptable in long-standing diabetes; SMBG and/or CGMS in patients on insulin
Cardiovascular	BP: Fasting lipid Profile; ECG: Cardiovascular risk assessment with a validated risk prediction model1	Transthoracic echocardiography (in cases with unexplained dyspnea and known cases of heart failure, especially with recent changes in clinical status); If risk ≥ 1%,2 functional status assessment. Poor (< 4 METs) or unknown functional capacity - exercise or pharmacological stress echocardiography or radionuclide MPI	Target BP < 140/90; Abnormal results in a stress test should be managed according to current clinical practice guidelines. Patients with underlying cardiac abnormalities should undergo a formal cardiology consultation before surgery
Pulmonary	Smoking history. Screening for OSA by a clinical scoring tool3. .Risk assessment for VTE during perioperative period by a validated method4	Pulmonary function test in presence of intrinsic pulmonary disease; Overnight polysomnography if indicated from results of scoring tool. ABG for PaCO2 estimation and venous bicarbonate in cases of OSA to rule out OHS	Structured tobacco cessation program if applicable
Gastrointestinal	-	UGIE to be considered routinely before LSG. Conditional for other procedures; H pylori detection and eradication
Hepatic	LFT	Abdominal USG if LFT deranged or symptomatic biliary disorder. Use of Noninvasive scoring systems5 can be considered. Liver elastography; Three-dimensional magnetic resonance elastography; Intraoperative liver biopsy	The strategy to diagnose NAFLD in bariatric patients is not defined. Variations of liver elastography such as transient elastography, 2-D shear wave elastography, and ARFI can be better modalities in severely obese patients. Intraoperative liver biopsy is the gold standard, but its specific indications are not clear
Renal, electrolytes, uric acid	Serum creatinine; eGFR6; Urinary albumin-creatinine ratio	Electrolytes in presence of CKD or drugs known to cause electrolyte imbalance. Uric acid if there is past history of gout	Serum potassium should be measured if on ACE inhibitors, ARBs, or diuretics
Nutritional	Nutritional assessment by a dietitian. Complete blood count, serum ferritin, serum iron, TIBC, and TS. Serum vitamin B12, folate. Serum calcium, 25(OH)D	Serum C-reactive protein if anemia of chronic inflammation is suspected. Serum methylmalonic acid and homocysteine in cases of low normal vitamin B12 and folate levels with high index of suspicion. Serum copper, zinc, and selenium; fat soluble vitamins such as vitamin A, E and K can be considered before malabsorptive procedures	Serum or urinary N-telopeptide, bone-specific alkaline phosphatase, and bone mineral density can be considered if osteoporosis is suspected especially in postmenopausal women
Endocrine	-	Thyroid profile if there is a past history of thyroid dysfunction, goiter or symptoms suggestive of thyroid disorder. ONDST, 24-h urinary free cortisol, or 11-pm salivary cortisol if there is suspicion of endogenous Cushing’s syndrome	Evaluation of syndromic or monogenic obesity on case-by-case basis
Reproductive	-	Total and bioavailable testosterone and USG of the pelvis if PCOS is suspected. LH, FSH, and testosterone (total) if hypogonadism is suspected in males	Women should avoid pregnancy if planned for surgery. Pregnancy should be avoided for 12-18 mo after surgery
Psychological	Behavioral and psychosocial evaluation	-	-

¹e.g., Revised Cardiac Risk Index, Obesity surgery mortality risk score, Longitudinal Assessment of Bariatric Surgery consortium risk stratification system, metabolic acuity score, etc.

²Estimated perioperative mortality risk or major adverse cardiovascular risk of ≥ 1%.

³STOP-BANG questionnaire or Berlin questionnaire.

⁴e.g., venous thromboembolism risk assessment tool by Fink et al[130].

⁵Non-alcoholic steatohepatitis clinical scoring system, AST to platelet ratio index, FIB-4 index, non-alcoholic fatty liver disease fibrosis score, BARD score and Forns index.

⁶By Chronic Kidney Disease Epidemiology Collaboration formula.

25(OH)D: 25-hydroxyvitamin D; ABG: Arterial blood gas; ACE: Angiotensin converting enzyme; ARB: Angiotensin II receptor blocker; ARFI: Acoustic radiation force impulse shear wave imaging; CGMS: Continuous glucose monitoring system; eGFR: Estimated glomerular filtration rate; FPG: Fasting plasma glucose; FSH: Follicle-stimulating hormone; H. pylori: Helicobacter pylori; HbA1c: Glycated hemoglobin; LFT: Liver function test; LH: Luteinizing hormone; MET: Metabolic equivalent; MPI: Myocardial perfusion imaging; ONDST: Overnight dexamethasone suppression test; OSA: Obstructive sleep apnea; PCOS: Polycystic ovary syndrome; PPG: Post-prandial glucose; SMBG: Self-monitoring of blood glucose; TIBC: Total iron-binding capacity; TS: Transferrin saturation; UGIE: Upper gastrointestinal endoscopy; USG: Ultrasonography; VTE: Venous thromboembolism.