Obesity affects 40% of American adults, representing an epidemic that continues to grow and carries with it a list of comorbidities that pose further health risk including hypertension, diabetes, heart disease, peripheral vascular disease, and more (1). Strategies for combatting obesity have significantly evolved to include complex medical and surgical solutions. Bariatric surgery continues to prove its utility as a means to combat obesity and therefore serves as an option for patients who have failed lifestyle and medical options and who suffer from obesity-related comorbidities. Over 270,000 Americans underwent bariatric surgery in 2024 – a number that stands atop a steady increase over the past 10 years and therefore represents the steady growing utility of the field (2).

Like all surgical procedures, weight-loss surgeries carry their own list of critical post-operative complications. As emergency physicians, it is imperative to consider the nuances that a bariatric surgical patient might pose and recognize the special considerations that need to be taken in their evaluation and management in the acute setting. Altered gastrointestinal anatomy and physiology regarding nutritional absorption make rare pathology a very real and life-threatening possibility for these patients that can become catastrophic if not recognized early.

Types of Bariatric Surgery

There are many options for bariatric surgery that patients can elect to undergo, arranged on spectra of invasiveness and degree of manipulation. The most common procedures include:

Gastric Band

A band is placed laparoscopically around the stomach and tightened in order to create a diminished stomach capacity. This causes early satiety and thereby decreases the quantity of food a patient might feel compelled to eat.

Gastric Sleeve

The greater curvature of the stomach is removed, leaving a much smaller gastric pocket that resembles a ‘sleeve.’ Similarly, this decreases stomach capacity and thereby induces early satiety. Data also suggests that satiety hormones such as GLP-1 are upregulated as hunger hormones such as ghrelin are decreased by mechanisms that remain incompletely understood (3).

Roux-en-Y Gastric Bypass

The stomach is divided to create a proximal pouch and a distal pouch. Further downstream, the jejunum is divided as well. The distal end of the jejunum is joined to the proximal stomach pouch (the G-J anastomosis) and the proximal jejunum is attached to the distal jejunum further downstream. This creates a small stomach that empties into the distal bowel and thereby bypasses the duodenum and a large portion of the small bowel, thus causing diminished nutritional uptake. The stomach and biliary structures are attached to the bowel further downstream to maintain a route for draining bile and gastric juices into the intestinal tract to aid digestion.

Biliopancreatic Diversion w/ Duodenal Switch

A gastric sleeve is created, but the duodenum is detached just distal to the pylorus. Similar to the Roux-en-Y technique, the jejunum is divided and the distal end is attached to the stomach remnant. The proximal jejunal end is reattached further downstream, allowing for flow of bile from the duodenum into the GI tract to aid digestion. (4)

Unique Surgical Complications

As in other surgical procedures, bariatric surgery carries risk for common post-operative complications including surgical site infection, bleeding, clotting events, post-operative ileus, intra-abdominal adhesions, and more. Components of obese patient’s histories and comorbidities unfortunately pose additional factors that heighten their risk. For example, obese patients’ higher adiposity often limits mobility and also has estrogenic activity that synergistically can increase risk of deep venous thrombosis or PE. In the midst of these broader considerations, the altered anatomy and physiology created by bariatric surgeries presents a broader list of unique complications that cannot be overlooked (5).

Gallstones

Alterations to the biliary outflow tract in gastric bypass surgeries can decrease biliary motility and therefore cause biliary stasis (6). Simultaneously, rapid weight loss after bariatric surgery causes alterations to bile chemistry and concentration that pose a higher likelihood of stone formation. As such, gallstones and their associated complications (e.g. choledocholithiasis, cholecystitis, pancreatitis, and cholangitis) become common adverse outcomes for bariatric surgery patients that can be difficult to avoid. A significant portion of these patients will ultimately undergo cholecystectomy for definitive management. (7)

Anastomotic Leak

Insufficient closure or breakdown at the sites of luminal conjunction or staple/suture closure can cause leakage of enteric contents into the peritoneal cavity. Early tachycardia and abdominal discomfort can quickly become intra-abdominal sepsis that can prove life-threatening if not identified and managed early. Treatment entails resuscitation, IV antibiotics, and urgent surgical repair often with intra-abdominal drain placement. (5)

Anastomotic Stricture

A far more common complication, strictures at the anastomotic sites can also be difficult to predict and avoid. Fibrosis, scar tissue formation, and even surgical technique can all predispose to and precipitate luminal stenosis that often present asymptomatically though can cause complicated bowel obstructions (8). As such, early detection in patients presenting with postprandial abdominal pain, nausea, vomiting, dysphagia, and/or distension is paramount to preventing adverse outcomes. Treatment entails endoscopy and dilation with close post-procedural surveillance.

Marginal Ulceration

More specific to bypass surgeries, marginal ulceration occurs as a result of stomach acid draining from the stomach antrum into the distal jejunum, causing chemical irritation and corrosion of the jejunal epithelium. Unlike the antral epithelium, the jejunum does not possess mucous cells and is therefore limited in its ability to buffer acidic exposures. Though ulcers can cause visceral pain and intraluminal bleeding, their development can also cause viscus perforation that represents a life-threatening surgical emergency. Patients are counseled to avoid non-steroidal anti-inflammatory drugs (NSAIDs) and further mitigate their risk by practicing tight glycemic control, avoiding alcohol and smoking, and taking proton-pump inhibitors (PPIs). Treatment for uncomplicated ulcers is largely supportive, with more medically acute and complex ulcers requiring definitive treatment with endoscopic coagulation/clipping or even surgical resection or repair. (9)

Internal Hernia

With normal anatomy, the abdominal mesentery binds the intestines and prevents spontaneous entanglement. However, surgical redirection of the gastrointestinal tract creates small areas of mesenteric discontinuity. This represents an internal ‘hernia’ through which loops of bowel can protrude and thus become incarcerated and strangulated, leading to bowel obstruction, ischemia, infarction, and perforation. Unlike the case of abdominal wall hernias, the emergency provider does not have the benefit of palpating and reducing an internal hernia, and therefore one must be suspected any time a post-operative patient presents with nonspecific abdominal pain, nausea, vomiting, food intolerance, or abdominal distension. Treatment entails an exploratory laparoscopy/laparotomy for definitive reduction and repair, possibly including resection of any bowel that has infarcted. (10)

Nutritional Complications

Many of the benefits of bariatric surgery come from nutritional under-absorption and in turn decreased caloric uptake achieved by the bypass of large portions of bowel mucosal surface area. The unfortunate downside to this alteration is the inadequate absorption of nutritional components integral to many physiologic functions. Some key nutritional deficiencies the emergency physician must acknowledge include:

Thiamine (B1): absorbed primarily in the proximal jejunum; deficiency can precipitate Wernicke-Korsakoff encephalopathy. (11)

Folate (B9): absorbed in the duodenum and proximal jejunum; deficiency can cause megaloblastic anemia as well as fetal neural tube defects in the pregnant patient. (11)

Cobalamin (B12): absorbed in the duodenum and terminal ileum, and dependent on secretion of intrinsic factor from parietal cells in the gastric fundus; deficiency causes megaloblastic anemia and neurologic symptoms including ataxia, peripheral neuropathy, and neuropsychiatric disturbances (11,12)

Cholecalciferol (D): absorbed in the distal jejunum and ileum, though its absorption is often inadequate in bariatric surgery patients possibly due to fat malabsorption related to decreased cholecystokinin and pancreatic enzyme exposure; deficiency causes neuromuscular symptoms, cardiac conduction abnormalities, and osteopenia that could predispose to pathologic fractures (11)

Iron: absorbed in the duodenum and jejunum; deficiency causes microcytic anemia

Copper: absorbed in the duodenum and jejunum; deficiency causes inadequate iron uptake and utilization, therefore causing microcytic anemia refractory to iron repletion/supplementation (12)

POST BY Ryley guay, MD

Dr. Guay is a PGY-1 in Emergency Medicine at the University of Cincinnati

EDITING BY arthur broadstock, MD

Dr. Broadstock is an Assistant Professor in Emergency Medicine at the University of Cincinnati and assistant editor of TamingtheSRU.com

Cite As: Guay, R., Broadstock, A. Diagnostics and Therapeutics: Bariatric Surgery Complications. TamingtheSRU. www.tamingthesru.com/blog/diagnostics-and-therapeutics/bariatric-surgery-complications. 4/29/2025.

References

1. CDC. Obesity and severe obesity prevalence in adults: United States, August 2021–August 2023. CDC.gov. Published September 2024. https://www.cdc.gov/nchs/products/databriefs/db508.htm

2. Estimate of Bariatric Surgery Numbers, 2011-2021. American Society for Metabolic and Bariatric Surgery. Published 2024. https://asmbs.org/resources/estimate-of-bariatric-surgery-numbers/

3. Holst JJ, Madsbad S, Bojsen-Møller KN, et al. Mechanisms in bariatric surgery: Gut hormones, diabetes resolution, and weight loss. Surgery for Obesity and Related Diseases. 2018;14(5):708-714. doi: 10.1016/j.soard.2018.03.003

4. Abu Dayyeh BK, Edmundowicz S, Thompson CC. Clinical Practice Update: Expert Review on Endoscopic Bariatric Therapies. Gastroenterology. 2017;152(4):716-729. doi: 10.1053/j.gastro.2017.01.035

5. Lim R, Beekley A, Johnson DC, Davis KA. Early and late complications of bariatric operation. Trauma Surgery & Acute Care Open. 2018;3(1):e000219. doi:10.1136/tsaco-2018-000219

6. Son S, Jeong Ho Song, Shin HJ, Hur H, Han S. Prevention of Gallstones After Bariatric Surgery using Ursodeoxycholic Acid: A Narrative Review of Literatures. Journal of metabolic and bariatric surgery. 2022;11(2):30-30. doi: 10.17476/jmbs.2022.11.2.30

7. Shubayr N, Elbashir M, Alashban Y, et al. Incidence of Gallbladder Stone Formation After Bariatric Surgery Using Ultrasound Imaging in the Southern Region of Saudi Arabia. Cureus. 2022;14(6). doi: 10.7759/cureus.25948

8. Csendes A, Burgos AM, Burdiles P. Incidence of anastomotic strictures after gastric bypass: a prospective consecutive routine endoscopic study 1 month and 17 months after surgery in 441 patients with morbid obesity. Obesity surgery. 2009;19(3):269-273. doi: 10.1007/s11695-008-9625-5

9. Salame M, Noura Jawhar, Belluzzi A, et al. Marginal Ulcers after Roux-en-Y Gastric Bypass: Etiology, Diagnosis, and Management. Journal of Clinical Medicine. 2023;12(13):4336-4336. doi: 10.3390/jcm12134336

10. Pokala B, Giannopoulos S, Stefanidis D. Prevention and Management of Internal Hernias after Bariatric surgery: an Expert Review. Mini-invasive Surgery. 2022;6(4):23. doi:10.20517/2574-1225.2021.136

11. Lupoli R, Lembo E, Saldalamacchia G, Avola CK, Angrisani L, Capaldo B. Bariatric surgery and long-term nutritional issues. World Journal of Diabetes. 2017;8(11):464. doi: 10.4239/wjd.v8.i11.464

12. Saltzman E, Karl JP. Nutrient deficiencies after gastric bypass surgery. Annual Review of Nutrition. 2013;33:183-203. doi: 10.1146/annurev-nutr-071812-161225

13. Reinders, Megan. (2018). Small Bowel Anastomotic Ulcers: A Source of Iron Deficiency Anemia in Adults Detected by Capsule Endoscopy. Clinical Studies & Medical Case Reports. 5. 1-4. 10.24966/CSMC-8801/100054.

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