Libyan Journal of Medical Sciences

: 2022  |  Volume : 6  |  Issue : 1  |  Page : 7--13

Pathology pick up rate in routine preoperative endoscopy and its impact on patients undergoing gastric bypass surgery

Abdulmajid Ali1, Peter Ishak1, Chinaka Ugochukwu1, Andisheh Bakhshi2, Rifat Mohamed3, Jean Rankin2,  
1 Department of Bariatric Surgery, University Hospital Ayr; University of the West of Scotland, Ayr, United Kingdom
2 University of the West of Scotland, Ayr, United Kingdom
3 Department of Bariatric Surgery, University Hospital Ayr, Ayr, United Kingdom

Correspondence Address:
Prof. Abdulmajid Ali
Lead Consultant, Bariatric Surgery Unit, University Hospital Ayr, Ayr, KA6 6DX
United Kingdom


Background and Aims: Patients with obesity are known for higher chances of having upper gastrointestinal (UGI) pathology and diseases. Esophagogastroduodenoscopy (OGD) is considered the investigation of choice to detect and confirm UGI pathology in patient with obesity. The routine OGD as a preoperative workup remained controversial before gastric bypass surgery. The need for preoperative OGD on patients undergoing bariatric surgery has been a subject of debate among bariatric surgeons. The study's aim is to evaluate the impact of routine preoperative endoscopy on patients underwent gastric bypass surgery laparoscopic Roux-en-Y gastric bypass (LRYGB). Patients and Materials: Retrospective review of prospectively kept patients' records who underwent LRYGB in our unit from February 2009 to March 2020. Patients were divided into two groups according to the absence or presence of symptoms before their preoperative OGD: Group A (asymptomatic patients) and Group B (symptomatic patients). Further data on OGD reports, campylobacter-like organism test and histology results and changes in the management plan were collected and analyzed. Calculation of post hoc power and Fisher's exact test was to investigate the correlation between OGD indication and its findings. All analyses were conducted at a 5% critical level. Results: A total of 114 patients included in the analysis, 85 (74.56%) were in Group A and 29 in Group B. OGD detected pathology in 34 patients in Group A and 21 in Group B (P = 0.004). Those included hiatus hernia (HH) (17.65% Group A, 44.83% Group B, P = 0.006); stomach ulcer (7.06% Group A, 3.45% Group B, P = 0.676), Helicobacter pylori (H. pylori) infection (12.86% Group A, 29.41% Group B). This led to change of management in 22 patients in Group A and 12 in Group B (P = 0.157). Those changes included H. pylori eradication (10.59% Group A, 17.24% Group B, P = 0.153), HH repair (3.53% Group A, 24.14% Group B, P = 0.002). Conclusions: Preoperative OGD has some significant impact on symptomatic patients. However, this is debatable among asymptomatic patients; hence, cheaper noninvasive alternatives could replace preoperative OGD.

How to cite this article:
Ali A, Ishak P, Ugochukwu C, Bakhshi A, Mohamed R, Rankin J. Pathology pick up rate in routine preoperative endoscopy and its impact on patients undergoing gastric bypass surgery.Libyan J Med Sci 2022;6:7-13

How to cite this URL:
Ali A, Ishak P, Ugochukwu C, Bakhshi A, Mohamed R, Rankin J. Pathology pick up rate in routine preoperative endoscopy and its impact on patients undergoing gastric bypass surgery. Libyan J Med Sci [serial online] 2022 [cited 2023 Mar 30 ];6:7-13
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Full Text


The epidemic of obesity (having a body mass index [BMI] of 30 and above) and its related medical diseases has been recognized as one of the most common public health problems facing the world today.[1] According to the World Health Organization, around 2 billion adults (40%) are classified as overweight, of those 650 million (13% of the total population) are diagnosed with obesity worldwide in 2016.[1] Scotland is one of the most significantly affected countries. In 2018, the majority of adults in Scotland (65%) was overweight, around one-third of those were diagnosed with obesity (28%).[2]

Among treatment modalities for obesity, bariatric surgery has been the most effective intervention for sustained weight loss. Bariatric surgery ameliorates obesity concurrent metabolic syndrome in the majority of patients.[3] Laparoscopic Roux-en-Y gastric bypass (LRYGB) surgery is one of the bariatric procedures where restriction and malabsorption of food happen simultaneously.[4]

Adequate preoperative workup is essential for the success of bariatric surgery. This workup is not only restricted to exercise, preoperative weight loss or attending a teaching program, but also essential preoperative investigations and interventions are required.[5]

Patients with obesity are known to have higher risk of upper gastrointestinal (UGI) pathology. Esophago-gastro-duodenoscopy (OGD) is considered the investigation of choice to detect and confirm UGI pathology in a patient with obesity.[6]

Some practitioners recommend routine OGD before all bariatric surgery, while others insist particularly on preoperative OGD before gastric bypass. As in LRYGB surgery, the remnant large pouch of the stomach is completely closed off with no further access to it in the future. Nonetheless, the practice of preoperative OGD has been a subject of debate over the past decades.[6],[7],[8]

In our center, we offered OGD to all patients before their LRYGB surgery to exclude any UGI pathology and eradicate Helicobacter pylori (H. pylori) infection. This study aimed to evaluate the prevalence of UGI pathology picked up by routine OGD in the patients who underwent LRYGB surgery in our bariatric unit in the West of Scotland and their clinical significance by affecting the patient's management pathway and the decision for hiatus hernia (HH) repair.

 Patients and Materials

Prospectively collected data of patients who underwent LRYGB surgery in University Hospital Ayr, Bariatric Unit in the West of Scotland from February 2009 to March 2020 were retrospectively investigated. Data collected included baseline demographics, initial BMI, OGD findings (pathological findings, histological findings where biopsies were taken and H. pylori infection). In addition, we have investigated how these findings impacted the patient's management plan in terms of medical treatment and HH repair.

The OGD was done either by the surgeon who undertook the surgery or by a trained endoscopist. The OGD was performed through a standardized technique, where the patient was sedated and/or pharyngeal lignocaine spray was used, then inspection of the esophagus, stomach, and duodenum performed, and findings were documented in an endoscopy electronic system. Biopsies were taken from the esophagus, stomach, and duodenum where indicated. The H. pylori infection was determined either by rapid urease test (CLO test, campylobacter-like organism test) or by histology staining where a biopsy was taken.

We divided the patient's population into two groups. Group A – asymptomatic group: Patients who did not have any UGI symptoms, diagnosis, or mandatory indication for OGD before their LRYGB Surgery. Group B – symptomatic group: patients who had UGI symptoms, diagnosis of UGI disease or an indication for OGD before their surgery. Group B also included patients who needed a revision of their previous bariatric surgery. We analyzed the OGD findings, biopsy results and H. pylori infection and the resultant change of treatment and management in these two groups.

We categorized the change of management into a surgical, medical, or delay to the patient operation. A change in the surgical management in our study was when the patient had a HH repair. A medical change of management was considered if any medication was prescribed to the patient as a result of the OGD findings. These were mainly proton pump inhibitors (PPI), H. pylori eradication therapy, and antifungal treatment.

Statistical analysis

We used Fisher's exact test to investigate if there is any correlation between the indication of the OGD and its findings among asymptomatic and symptomatic patients. Baseline characteristics are also statistically compared in the study groups. All statistical tests are conducted at a 5% critical level. This is a retrospective observational study with all the inclusive data used for the analysis. Therefore, the prior study power is not applicable. However, a post hoc power is calculated. Descriptive statistics for the continuous measurement such as age and initial BMI are presented as mean and standard deviation. Frequency and percentage are given separately for categorical variables.


A total of 137 patients had LRYGB in our bariatric unit from February 2009 to March 2020. The patients with missing OGD reports (n = 12) or the patients who did not have one before their procedure (n = 11) were excluded from the study. Therefore, 114 patients were included in the analysis, of which 85 (75%) did not have any UGI symptoms or indication for OGD before their gastric bypass surgery and they were considered as Group A. The remaining 29 patients (25%) (Group B) were either symptomatic or diagnosed with previous UGI disease (13 patients, 11.4%) or scheduled for revisional surgery (16 patients, 14%). The indications for OGD in Group B are represented in [Table 1].{Table 1}

Patients were on average 52.41 years of age (±8.55) with initial BMI of 47.06 (±8.34) [Table 2]. The asymptomatic patients were significantly older than the symptomatic group by an average of 4.34 years (53.49 ± 8.58 vs. 49.15 ± 8.08) (P = 0.021). They had a significantly lower initial BMI (P = 0.017) by an average of 5.72 (45.65 ± 6.67 vs. 51.37 ± 11.19). The odds of being asymptomatic for a female is 0.21 times that for a male (P = 0.34).{Table 2}

Pathological findings

At least one pathology was diagnosed during the OGD in 34 asymptomatic patients (40%) compared to 21 (72%) among Group B. The result of the Fisher's exact test indicates that the patients with no UGI symptoms are 3.89 times likely to be pathology free (P = 0.004).

The pathological findings in both groups are presented in [Figure 1].{Figure 1}

Biopsy and histopathology results

Tissue biopsy was taken in 21 (25%) patients of Group A and 11 (38%) of Group B. Out of the 21 taken biopsy in Group A, 15 (71%) showed histological pathology, compared to 5 out of 11 (45%) in Group B [Table 3].{Table 3}

Helicobacter pylori infection

Seventy of the patients in the asymptomatic group (82%) had either their CLO test taken or histological staining for the evaluation of H. pylori infection. Nine patients (13%) had H. pylori infection. Fifty-six patients had no evidence of H. pylori (80%), and the rest of 5 patients their CLO test results were missing (7%). In the symptomatic group, 17 patients were investigated for H. pylori. Five (29%) of them had H. pylori infection, and twelve (71%) patients had negative H. pylori test results (P = 0.15) [Table 4].{Table 4}

Change of management due to esophago-gastro- duodenoscopy findings

Overall, 34 patients had an abnormality in their preoperative OGD that resulted in a change or more in their management plan. Twenty-two of these patients were from the asymptomatic group (26%) and 12 were from the symptomatic group (41%) (P = 0.157).

The changes in the treatment or the management plan in both groups are demonstrated in [Figure 2]. Please note that patients could have more than one change in their management plan. For example, the patient who had gastric sleeve stricture and HH, required two further preoperative OGDs, one intraoperative, preoperative assessment with Barium meal, and HH repair during her gastric bypass surgery (change of management for each patient is shown in [Table 5].{Figure 2}{Table 5}


Bariatric surgery is currently the standard treatment for obesity and its related metabolic diseases.[8] Preoperative preparation is strongly recommended to avoid the short-term and long-term complications. OGD is one of the essential tools of preoperative assessment to exclude UGI pathologies that may lead to unwanted outcomes. The selection of candidates for preoperative OGD is a controversial subject. In addition, it is associated with costs.[9],[10] and procedure risks[11] and it should be avoided and replaced by other cheaper and noninvasive investigations if possible.

The European Association for Endoscopic Surgery guidelines recommends routine OGD for all patients undergoing bariatric surgery. However, a selective approach is suggested by three other committees (the Standard of Practice Committee of the American Society for gastrointestinal endoscopy, society of gastrointestinal and endoscopic Surgeons, and the American Society for metabolic and bariatric surgery American guidelines).[8],[12] The European chapter of the international federation for the surgery of obesity has no formal stand on the matter currently.[13]

In the United Kingdom, a survey done by the British Obesity and Metabolic Surgery Society indicated that there was a wide variation in the practice across the UK regarding the selection of patients for preoperative OGD.[14] In our study, we looked at its impact on the patients who underwent LRYGB surgery as follows:

Surgical change of management

Hiatus hernia repair

HH is one of the most common pathologies in patients with obesity compared with the normal population.[15],[16] Obesity is considered an independent risk factor for the development of HH. In this study, 15 (17.6%) patients in the asymptomatic group were diagnosed with an HH on the OGD, three of them (3.5%) required surgical repair at the time of operation (hernia size was >3 cm). However, 13 (45%) patients in Group B had HH on their preoperative OGD (P = 0.006, odds ratio 3.74, 95% confidence interval 1.35–10.45), 7 of them (24%) required a surgical repair (P = 0.114). This proofs that HH is more likely to be diagnosed in symptomatic patients by nearly four times than the asymptomatic ones.

In asymptomatic patients, there has been always the question, could HH be diagnosed and assessed intraoperatively? and the decision to repair it or not could be made on the spot to save the patient waiting for the OGD? and not to expose them to another invasive investigation? In a study conducted by Boules et al., they were able to diagnose 51 asymptomatic patients with HH intraoperatively. These patients had a concurrent HH repair with their bariatric surgery.[16] They concluded that there was no need for an additional preoperative OGD.

Some surgeons may argue that they would need to plan and allocate extra time in theatre for the HH repair. They may prefer to know the diagnosis in advance to have a discussion with the patient which would ensure compliance with the informed consent process. This could be an issue if the surgeon is unsure of its presence. Others felt that the preoperative diagnosis would be less important and that HH would require repair only if the patient was known to have symptoms, or depending on its appearance (simple sliding/complex para-esophageal) and size seen at the time of surgery.[17] Other studies proved that LRYGB surgery on its own is an anti-reflux procedure and the patient shouldn't have their HH repaired at the same time.[18],[19] This evidence makes the necessity of preoperative OGD questionable in diagnosing HH in asymptomatic patients.

Medical change of management

Prescription of proton-pump inhibitors

Morbid obesity is associated with inflammatory activity in the UGI tract.[15] In this study, the second-most found pathology in the asymptomatic patients was gastritis (ten patients, 11.7%) and then stomach ulcer peptic ulcer disease (PUD, six patients). All the patients with gastritis required PPI treatment.

Inoue et al. found out that the risk factors of marginal ulcer (MU) in patients with LRYGB surgery included only smoking, steroids, and nonsteroidal anti-inflammatory drugs. Gastritis or PUD before bariatric surgery was not significantly linked to the development of MU.[20] In this study, 6 (7%) patients in the asymptomatic group had a stomach ulcer on their OGD compared to one patient in Group B. Every patient who had a stomach ulcer required further OGD before their LRYGB surgery to confirm the ulcer resolution after they were treated with PPI. In these six patients, the operation was delayed until the ulcer had healed (evaluated by OGD).

Current literature suggests that routine postoperative PPI use is beneficial in reducing the incidence of MUs, making the utility of OGD for this reason questionable.[21],[22] Some surgeons argue that there is no benefit from routine preoperative OGD in determining and treating gastritis or PUD as the postoperative management already includes PPI treatment and the LRYGB is a good anti-reflux operation.[18],[19]

Pylori infection and eradication

H. pylori infection has been described as a risk factor for developing MU in patients undergoing LRYGB surgery. Eradication therapy and prophylactic PPIs therapy might be useful to prevent MU postoperatively.[23] However, in another study conducted by Coblijn et al. involving 350 patients, only two of twenty-three patients with MU had a history of H. pylori infection before their surgery and had undergone eradication therapy.[20] This possible postoperative complication of H. pylori might justify preoperative H. pylori screening.[24]

In our study, 9 patients (10.6%) of the asymptomatic group tested positive for H. pylori infection. These patients required eradication therapy and PPI before their LRYGB surgery. Only two of them had a breath test to confirm the eradication of H. pylori. If the preoperative determination of H. pylori status is considered important, several noninvasive and less expensive testing methods are available, including urea breath testing and serology and stool antigen test. Moreover, OGD is not mandatory to detect H. pylori. Some argue that these noninvasive tests do not allow the evaluation of other pathological findings such as gastric ulcer, atrophic gastritis, and gastric cancer preoperatively. This might be an issue, especially in patients undergoing LRYGB, where the gastric remnant will no longer be easily accessible.[25]

Antifungal treatment

One patient in the asymptomatic group had esophageal candidiasis which required anti-fungal medications.

Delay in the operative procedure due to esophago-gastro- duodenoscopy findings

Eleven patients (13%) had their LRYGB operation delayed due to preoperative OGD findings [Table 6]. Six delays were because of the need for further OGD to confirm the resolution of gastric ulcer. One patient had a polyp and features suggesting gastrointestinal stromal tumor (GIST). Her operation was delayed, and a computed tomography (CT) abdomen requested which came back negative. Further endoscopic ultrasound excluded GIST and the patient proceeded to have surgery as planned. In another asymptomatic patient, there was a question regarding if there were external pressure on the stomach in their preoperative OGD, CT scan was performed, and it did not show any pathology. These two patients had to be exposed to unnecessary radiation with attendant delay in the timing of surgery.{Table 6}

Biopsy and histology results

Tissue biopsy was taken in 21 (24.7%) patients of the asymptomatic group and 11 (38%) patients of Group B, the histological findings are shown in [Table 3]. None of these patients with gastritis was diagnosed with autoimmune gastritis, which is a risk factor for gastric cancer.[26] None of these histological findings impacted the patient management plan.


Many surgeons would argue that potential malignant lesions warrant preoperative screening. This is primarily a concern with respect to screening and diagnosing premalignant and malignant disease. However, the incidence of UGI malignancy in low-risk, asymptomatic patients is very low.[10] Inoue et al. demonstrated in an experimental model of dietary-induced carcinogenesis that the LRYGB procedure reduces the risk of gastric cancer. Lack of direct contact with carcinogens, lower bile reflux, and a lower bacteria concentration in the remnant stomach were possible explanations for this phenomenon.[27]

No malignancy was found in our study. Barrett's esophagus was found in one of the patients of Group B.

The significance of the change of management

If we exclude the PPI prescription as a significant change of management, as the patient will be prescribed PPI postoperatively as per the bariatric surgery protocol anyway. H. pylori infection could be screened by noninvasive and cheaper tests and then eradication treatment could be started accordingly. HH diagnosis and repair decision could be made intraoperatively which is a benefit of the laparoscopic procedure. The only treatment and pathology which could only be diagnosed by the preoperative OGD in our study in the asymptomatic patients was the antifungal treatment for esophageal candidiasis.

Limitation of the study

This is study is a retrospective comparative study. It is limited by the small sample size and its single centeredness. The study inclusion criteria are patients who underwent LRYGB surgery only and it does not assess how many patients ended up managed nonoperatively. The symptomatic patients were a mixture of both who had revisional and primary bariatric surgery. We would recommend a prospective study to investigate the full impact of OGD, or a retrospective study that includes all the other types of bariatric procedures to investigate if the bariatric procedure was changed due to significant OGD findings.


Preoperative OGD appears to have some significant impact among symptomatic patients in identifying “related” pathology. However, this is debatable among asymptomatic patients; hence cheaper, noninvasive alternatives could replace preoperative OGD.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


1Prevalence of Obesity. World Obesity Federation. Available from: [Last accessed on 2020 Oct 24].
2Luppino FS, de Wit LM, Bouvy PF, Stijnen T, Cuijpers P, Penninx BW, et al. Overweight, obesity, and depression: A systematic review and meta-analysis of longitudinal studies. Arch Gen Psychiatry 2010;67:220-9.
3Chang SH, Stoll CR, Song J, Varela JE, Eagon CJ, Colditz GA. The effectiveness and risks of bariatric surgery: An updated systematic review and meta-analysis, 2003-2012. JAMA Surg 2014;149:275-87.
4Gastric Bypass Surgery. In: Wikipedia; 2020. Available from: [Last accessed on 2020 Oct 25].
5Schlottmann F, Nayyar A, Herbella FA, Patti MG. Preoperative evaluation in bariatric surgery. J Laparoendosc Adv Surg Tech A 2018;28:925-9.
6Baysal B, Kayar Y, Danalıoğlu A, Özkan T, Kayar NB, Ünver N, et al. The importance of upper gastrointestinal endoscopy in morbidly obese patients. Turk J Gastroenterol 2015;26:228-31.
7Preoperative Endoscopy In Bariatric Patients May Change Surgical Strategy. Available from: [Last accessed on 2020 Sep 3].
8Di Lorenzo N, Antoniou SA, Batterham RL, Busetto L, Godoroja D, Iossa A, et al. Clinical practice guidelines of the European association for endoscopic surgery (EAES) on bariatric surgery: Update 2020 endorsed by IFSO-EC, EASO and ESPCOP. Surg Endosc 2020;34:2332-58.
9Azagury D, Dumonceau JM, Morel P, Chassot G, Huber O. Preoperative work-up in asymptomatic patients undergoing roux-en-Y gastric bypass: Is endoscopy mandatory? Obes Surg 2006;16:1304-11.
10Vakil N, Talley N, van Zanten SV, Flook N, Persson T, Björck E, et al. Cost of detecting malignant lesions by endoscopy in 2741 primary care dyspeptic patients without alarm symptoms. Clin Gastroenterol Hepatol 2009;7:756-61.
11Küper MA, Kratt T, Kramer KM, Zdichavsky M, Schneider JH, Glatzle J, et al. Effort, safety, and findings of routine preoperative endoscopic evaluation of morbidly obese patients undergoing bariatric surgery. Surg Endosc 2010;24:1996-2001.
12Mechanick JI, Apovian C, Brethauer S, Garvey WT, Joffe AM, Kim J, et al. Clinical practice guidelines for the perioperative nutrition, metabolic, and nonsurgical support of patients undergoing bariatric procedures – 2019 update: Cosponsored by American association of clinical endocrinologists/American college of endocrinology, the obesity society, American society for metabolic & bariatric surgery, obesity medicine association, and American society of anesthesiologists – Executive summary. Endocr Pract 2019;25:1346-59.
13Fried M, Yumuk V, Oppert JM, Scopinaro N, Torres A, Weiner R, et al. Interdisciplinary European guidelines on metabolic and bariatric surgery. Obes Surg 2014;24:42-55.
14Zanotti D, Elkalaawy M, Hashemi M, Jenkinson A, Adamo M. Current status of preoperative oesophago-gastro-duodenoscopy (OGD) in bariatric NHS units-a BOMSS survey. Obes Surg 2016;26:2257-62.
15de Vries DR, van Herwaarden MA, Smout AJ, Samsom M. Gastroesophageal pressure gradients in gastroesophageal reflux disease: Relations with hiatal hernia, body mass index, and esophageal acid exposure. Am J Gastroenterol 2008;103:1349-54.
16Boules M, Corcelles R, Guerron AD, Dong M, Daigle CR, El-Hayek K, et al. The incidence of hiatal hernia and technical feasibility of repair during bariatric surgery. Surgery 2015;158:911-6.
17Bennett S, Gostimir M, Shorr R, Mallick R, Mamazza J, Neville A. The role of routine preoperative upper endoscopy in bariatric surgery: A systematic review and meta-analysis. Surg Obes Relat Dis 2016;12:1116-25.
18Merrouche M, Sabaté JM, Jouet P, Harnois F, Scaringi S, Coffin B, et al. Gastro-esophageal reflux and esophageal motility disorders in morbidly obese patients before and after bariatric surgery. Obes Surg 2007;17:894-900.
19Tai CM, Lee YC, Wu MS, Chang CY, Lee CT, Huang CK, et al. The effect of roux-en-Y gastric bypass on gastroesophageal reflux disease in morbidly obese Chinese patients. Obes Surg 2009;19:565-70.
20Coblijn UK, Lagarde SM, de Castro SM, Kuiken SD, van Wagensveld BA. Symptomatic marginal ulcer disease after roux-en-Y gastric bypass: Incidence, risk factors and management. Obes Surg 2015;25:805-11.
21Coblijn UK, Lagarde SM, de Castro SM, Kuiken SD, van Tets WF, van Wagensveld BA. The influence of prophylactic proton pump inhibitor treatment on the development of symptomatic marginal ulceration in roux-en-Y gastric bypass patients: A historic cohort study. Surg Obes Relat Dis 2016;12:246-52.
22Ying VW, Kim SH, Khan KJ, Farrokhyar F, D'Souza J, Gmora S, et al. Prophylactic PPI help reduce marginal ulcers after gastric bypass surgery: A systematic review and meta-analysis of cohort studies. Surg Endosc 2015;29:1018-23.
23Sverdén E, Mattsson F, Sondén A, Leinsköld T, Tao W, Lu Y, et al. Risk factors for marginal ulcer after gastric bypass surgery for obesity: A population-based cohort study. Ann Surg 2016;263:733-7.
24Hartin CW Jr., ReMine DS, Lucktong TA. Preoperative bariatric screening and treatment of helicobacter pylori. Surg Endosc 2009;23:2531-4.
25Gisbert JP, de la Morena F, Abraira V. Accuracy of monoclonal stool antigen test for the diagnosis of H. pylori infection: A systematic review and meta-analysis. Am J Gastroenterol 2006;101:1921-30.
26Kuipers EJ. Helicobacter pylori and the risk and management of associated diseases: Gastritis, ulcer disease, atrophic gastritis and gastric cancer. Aliment Pharmacol Ther 1997;11 Suppl 1:71-88.
27Inoue H, Rubino F, Shimada Y, Lindner V, Inoue M, Riegel P, et al. Risk of gastric cancer after roux-en-Y gastric bypass. Arch Surg 2007;142:947-53.