Gastric Bypass - Bariatric Surgery Postoperative Monitoring

Bariatric surgeries are increasingly used to treat overweight and obese patients who have clinically relevant signs and symptoms. Surgeons performed ~196,000 bariatric surgeries in the U.S. in 2015. These procedures can be successful in reversing many adverse syndromes (including diabetes, hypertension, joint pain, obstructive sleep apnea), but there are risks and complications to consider, such as the exacerbation of preexisting nutritional deficiencies and the development of new ones. Some of these deficiencies present early following surgery, but the late presentation of nutritional deficiencies is increasingly recognized to contribute to poor outcomes or devastating complications. Bariatric surgeries using a restrictive technique present a lower risk of subsequent nutritional deficiencies, while restrictive surgeries combined with malabsorptive techniques, such as Roux-en-Y and biliopancreatic diversion (BPD), may pose a higher risk. Therefore, long-term monitoring for nutritional deficiencies is indicated following gastric bypass surgeries.

Tabs Content

Clinical Overview

Quick Answers

What types of bariatric procedures are performed to induce weight loss?

Bariatric procedures can be classified as restrictive or malabsorptive. Restrictive procedures reduce the volume or capacity of the stomach. Malabsorptive procedures reduce the amount of calories absorbed by altering the flow of the food. Sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB) are the most popular procedures. SG is a restrictive procedure; RYGB is a dual malabsorptive and restrictive technique.

What testing is appropriate for preoperative gastric bypass assessment?

Individuals being considered for bariatric surgery should have a preoperative nutritional assessment, with correction where possible, to identify deficiencies that may predispose them to higher risk of nutritional deficiencies. Common testing includes vitamins, folate (ie, vitamin B₉), iron, ferritin, and calcium. See below for full list of testing to consider.

What testing is used for postoperative monitoring?

The same tests used for preoperative assessment are also used postsurgery. The biochemical and nutritional testing schedule varies depending on the type of surgery. Refer to the tables in Monitoring below for full schedules.

Indications for Testing

Prior to bariatric surgery, individuals should be assessed for nutritional status. Patients who have undergone surgical modification of the gastrointestinal (GI) tract for management of obesity should be monitored postsurgery for nutritional deficiencies. Clinical presentations may suggest specific nutritional deficiencies to investigate. The following table offers some examples.

Clinical Features	Suspected Deficiencies
Prolonged nausea and vomiting (food intolerance)	Vitamin B₁ (most critical)
Nausea, constipation, neurologic and psychiatric complications (Wernicke-Korsakoff syndrome)	Vitamin B₁
Anemia, fatigue, shortness of breath, orthostatic hypotension	Iron, vitamin B₁₂
Neurologic and psychiatric changes, eg, paresthesias, numbness, balance problems, memory disturbance, dementia	Vitamin B₁₂
Osteoporosis, fatigue	Vitamin D
Macrocytic anemia, glossitis, leukopenia, thrombocytopenia	Folate
Night blindness, dry eyes/hair	Vitamin A

Laboratory Testing

Preoperative Assessment

Individuals being considered for bariatric surgery should have baseline biochemical and nutritional testing performed, with correction where possible, prior to surgery, to identify deficiencies that may predispose them to a higher risk of deficiencies after surgery.Testing to consider includes the following.

Vitamin B₁: Evaluate for thiamine deficiency. Whole blood specimens are required for accurate analysis.
Vitamin B₁₂: Assess for vitamin B₁₂ deficiency, which may take longer to present due to the body’s ability to maintain large stores of the vitamin. B₁₂ deficiency may result from intrinsic factor decrease and loss of absorptive surface.
Folate: Evaluate for folate (B₉) deficiency, which is rarely seen due to consumption of fortified foods.
Iron: Lab testing includes iron, iron binding capacity, and ferritin. Iron deficiency may be present prior to surgery and may be exacerbated by the loss of absorptive surface and/or changes in food preferences.
Ferritin: Evaluate for iron deficiency anemia. Ferritin, an acute phase reactant, is the most sensitive marker for iron deficiency anemia, but may be affected by inflammation.
Iron and iron binding capacity: Use periodically to verify accuracy of ferritin testing. This test is not as sensitive as ferritin.
Vitamin D/calcium: Vitamin D, 25-hydroxy is a marker of vitamin D stores in the body and is the preferred test. Vitamin D, 1,25 dihydroxy is indicated for renal disease and other special situations and is less commonly used. Calcium may be reduced due to changes in food preferences.
Comprehensive metabolic panel: Evaluate adequacy of protein intake.
Vitamins A, E, and K; zinc; copper; magnesium; phosphorous; and parathyroid hormone tests should be considered as well.

Postoperative Monitoring

The postoperative schedule for biochemical and nutritional testing is based on type of surgery: adjustable gastric banding (AGB), sleeve gastrectomy (SG), Roux-en-Y gastric bypass (RYGB), or BPD.

AGB
Analyte	Time Postsurgery (Mos)
Analyte	1	3	6	12	18	24	Annually Thereafter
Calcium	X	X	X	X	X	X	X
Vitamin B₁	X	X		X		X	X
Vitamin B₁₂			X	X	X	X	X
Vitamin B₆				X			X^a
Vitamin D				X		X	X
Vitamin E				X
Magnesium		X	X
Transferrin		X	X	X		X	X
Zinc				X		X	X
Ferritin		X	X	X		X	X
Iron				X		X	X
Parathyroid hormone			X	X		X	X
Phosphorous				X		X	X
^aEvery 2-5 yrs Source: Lupoli, 2017

SG
Analyte	Time Postsurgery (Mos)
Analyte	1	3	6	12	18	24	Annually Thereafter
Calcium	X	X	X	X	X	X	X
Vitamin B₁		X		X		X	X
Vitamin B₆				X		X	X^a
Vitamin B₁₂			X	X	X	X	X
Vitamin D				X		X	X
Vitamin E				X		X
Magnesium		X	X
Transferrin		X	X	X		X	X
Zinc				X		X	X
Ferritin		X	X	X		X	X
Iron				X		X	X
Parathyroid hormone			X	X		X	X
Phosphorous				X		X	X
^aEvery 2-5 yrs Source: Lupoli, 2017

RYGB/BPD
Analyte	Time Postsurgery (Mos)
Analyte	1	3	6	12	18	24	Annually Thereafter
Calcium	X^a	X^a	X^a	X^a	X^a	X^a	X^a
Vitamin B₁	X^b	X^a		X^a		X^a	X^a
Vitamin B₆				X^a			X^a,c
Vitamin B₁₂			X^b	X^b	X^b	X^b	X^b
Vitamin A		X^a	X^a	X^a		X^b	X^a
Vitamin D		X^b	X^b	X		X^b	X^b
Vitamin E				X^a
Magnesium		X^a	X^a	X^a		X^a	X^a
Transferrin		X^a	X^a	X^a		X^a	X^a
Zinc		X^a	X^b	X^b		X^b	X^b
Ferritin		X^a	X^a	X^a		X^a	X^a
Iron		X^a	X^a	X^b	X^a	X^b	X^b
Parathyroid hormone			X^b	X^a		X^b	X^b
Phosphorous				X^a		X^a	X^a
^aUseful for BPD ^bRecommended for BPD ^cEvery 2-5 yrs for BPD Source: Lupoli, 2017

ARUP Lab Tests

Copper, Serum or Plasma 0020096

Method: Quantitative Inductively Coupled Plasma-Mass Spectrometry

Ferritin 0070065

Method: Quantitative Chemiluminescent Immunoassay

Folate, RBC 0070385

Method: Quantitative Chemiluminescent Immunoassay

Folate, Serum 0070070

Method: Quantitative Chemiluminescent Immunoassay

Iron and Iron Binding Capacity 0020420

Method: Quantitative Spectrophotometry

Magnesium, Plasma or Serum 0020039

Method: Quantitative Spectrophotometry

Magnesium, RBC 0092079

Method: Quantitative Inductively Coupled Plasma-Mass Spectrometry

Parathyroid Hormone, Intact with Calcium 0070172

Method: Quantitative Electrochemiluminescent Immunoassay

Renal Function Panel 0020144

Method: Quantitative Chemiluminescent Immunoassay/Quantitative Enzyme-Linked Immunosorbent Assay

Vitamin B1 (Thiamine), Whole Blood 0080388

Method: Quantitative High Performance Liquid Chromatography

Vitamin B12 0070150

Method: Quantitative Chemiluminescent Immunoassay

Vitamin B12 and Folate 0070160

Method: Quantitative Chemiluminescent Immunoassay

Vitamin C (Ascorbic Acid), Plasma 0080380

Method: Quantitative High Performance Liquid Chromatography

Vitamin D, 25-Hydroxy 0080379

Method: Quantitative Chemiluminescent Immunoassay

Vitamin K1, Serum 0099225

Method: Quantitative High Performance Liquid Chromatography

Zinc, Serum or Plasma 0020097

Method: Quantitative Inductively Coupled Plasma-Mass Spectrometry

Medical Experts

Frank, Elizabeth L., PhD, Medical Director, Analytic Biochemistry, Calculi and Manual Chemistry, and Co-Medical Director, Mass Spectrometry at ARUP Laboratories ; Associate Professor of Clinical Pathology, University of Utah

References

Bray GA, Heisel WE, Afshin A, Jensen MD, Dietz WH, Long M, Kushner RF, Daniels SR, Wadden TA, Tsai AG, Hu FB, Jakicic JM, Ryan DH, Wolfe BM, Inge TH. The Science of Obesity Management: An Endocrine Society Scientific Statement. Endocr Rev. 2018; 39(2): 79-132. PubMed
DeMaria EJ. Bariatric surgery for morbid obesity. N Engl J Med. 2007; 356(21): 2176-83. PubMed
Gletsu-Miller N, Wright BN. Mineral malnutrition following bariatric surgery. Adv Nutr. 2013; 4(5): 506-17. PubMed
Parrott J, Frank L, Rabena R, Craggs-Dino L, Isom KA, Greiman L. American Society for Metabolic and Bariatric Surgery Integrated Health Nutritional Guidelines for the Surgical Weight Loss Patient 2016 Update: Micronutrients. Surg Obes Relat Dis. 2017; 13(5): 727-741. PubMed
Weng T, Chang C, Dong Y, Chang Y, Chuang L. Anaemia and related nutrient deficiencies after Roux-en-Y gastric bypass surgery: a systematic review and meta-analysis. BMJ Open. 2015; 5(7): e006964. PubMed
Lupoli R, Lembo E, Saldalamacchia G, Avola CK, Angrisani L, Capaldo B. Bariatric surgery and long-term nutritional issues. World J Diabetes. 2017; 8(11): 464-474. PubMed

Additional Resources

Buchwald H, Avidor Y, Braunwald E, Jensen MD, Pories W, Fahrbach K, Schoelles K. Bariatric surgery: a systematic review and meta-analysis. JAMA. 2004; 292(14): 1724-37. PubMed

Livingston EH. Reimagining Obesity in 2018: A JAMA Theme Issue on Obesity. JAMA. 2018; 319(3): 238-240. PubMed

Mechanick JI, Youdim A, Jones DB, Garvey T, Hurley DL, McMahon M, Heinberg LJ, Kushner R, Adams TD, Shikora S, Dixon JB, Brethauer S, American Association of Clinical Endocrinologists, Obesity Society, American Society for Metabolic & Bariatric Surgery. Clinical practice guidelines for the perioperative nutritional, metabolic, and nonsurgical support of the bariatric surgery patient--2013 update: cosponsored by American Association of Clinical Endocrinologists, The Obesity Society, and American Society for Metabolic & Bariatric Surgery. Obesity (Silver Spring). 2013; 21 Suppl 1: S1-27. PubMed

Puzziferri N, Roshek TB, Mayo HG, Gallagher R, Belle SH, Livingston EH. Long-term follow-up after bariatric surgery: a systematic review. JAMA. 2014; 312(9): 934-42. PubMed

Stein J, Stier C, Raab H, Weiner R. Review article: The nutritional and pharmacological consequences of obesity surgery. Aliment Pharmacol Ther. 2014; 40(6): 582-609. PubMed

Content Review:

January 2018

Last Update: September 2018

Gastric Bypass - Bariatric Surgery Postoperative Monitoring

Quick Answers

What types of bariatric procedures are performed to induce weight loss?

What testing is appropriate for preoperative gastric bypass assessment?

What testing is used for postoperative monitoring?

Indications for Testing

Laboratory Testing

Preoperative Assessment

Postoperative Monitoring

ARUP Lab Tests

Medical Experts

References

Additional Resources

ARUP Laboratories

ARUP Websites

ARUP Consult


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