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

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.