Clinical Outcomes 2019 – 2020

BOMSS supports the publication of clinical outcomes and is committed to improving the range of information that is publicly available. Publishing outcome data will help patients to make informed decisions about their care and will support surgeons to continually assess and raise standards of surgery.

Bariatric Surgery Clinical Outcomes Publication 2019 – 2020


The United Kingdom National Bariatric Surgery Registry (NBSR)

Publication of Surgeon-level data in the public domain for bariatric surgery in NHS England


The NBSR Committee on behalf of the British Obesity and Metabolic Surgery Society presents the operative outcomes data for NHS patients having bariatric surgery for the three financial years 2016/17 to 2018/19 on The main results are summarised in the table below from the data cut taken on 1st April 2019, with the 2012/18 data copied from the 2017/18 Report.

As before, all NHS data are included and there were no non-contributing hospitals. The total number of hospitals includes private hospitals where these were used to provide additional capacity for the NHS bariatric units. The data shown are those of surgeons who are or were practising within the NHS for the 3 years reported in this Clinical Outcomes Publication (COP).

Year No of surgeons submitting data Number of Hospitals Number of NBSR operations recorded * Number of primary operations Total number of revision operations
2012/13 120 74 5528 5192 336 (6.1%)
2013/14 139 69 5729 5297 432 (7.5%)
2014/15 140 70 5671 4989 682 (12%)
2015/16 146 65 5704 5056 648 (11.4%)
2016/17 150 67 5675 5085 630 (11%)
2017/18 146 61 5566 4833 588 (10.6%)
2018/19 151 68 5675 5268 407 (7.2%)
Total 39623 35720 3723 (9.4%)


Year Number of NBSR primary operations and revisions HES recorded data (NBSR case ascertainment primary operations %) ** Recorded in-hospital mortality (%) *** HES recorded in-hospital mortality ONS recorded 30-day mortality
2012/13 5307 6152 (84%) 5 **** 14
2013/14 5464 5597 (95%) 6 **** 6
2014/15 5288 5393 (92%) 2 **** 5
2015/16 5319 5057 (100%) 0 **** 6
2016/17 5478 5429 (100%) 1 (0.02%) **** 0
2017/18 5421 5641 (96%) 3 (0.05%) **** 3
2018/19 5675 5933 (96%) 0 **** 1
Total 37952 39202


* These data include all primary and revision surgery, without subdividing revision surgery into major and minor. Therefore the numbers include re-operations for complications of the primary procedure (which may not be detected as bariatric operations by HES) as well as conversions to another bariatric procedure. There are a few cases each year which are not classified within NBSR as either primary or revisional surgery.

** The historic HES data volumes are slightly different from those recorded in the 2015/16 COP report due to adjustments made by the HSCIC. Case ascertainment is recorded as primary operations in NBSR/HES recorded data (%).

***The NBSR mortality data we report are in-hospital deaths and exclude patients who may be readmitted and die due to a complication of surgery within 30 days. The data are adjusted compared to previous reported, since entries on the registry have been changed/edited by contributing surgeons.

**** Data suppressed as low numbers to prevent potential identification of individual patients. HES noted less than 5 deaths between 2016 and 2018.

Mortality statistics according to Hospital Episode Statistics (HES) are shown on the following table and record both the number of deaths in hospital and within 30 days of surgery.

Mortality Statistics
Patient Type Financial Year Deaths in hospital Next 30 days Survive
NHS 2009/10 8 11 4994
2010/11 6 5882
2011/12 9 6326
2012/13 10 6060
2013/14 6 10 5522
2014/15 5327
2015/16 6 4995
2016/17 5 5 5259
2017/18 9 5506
2018/19 5929
NHS      Total 34 51 55800


The HES in-hospital mortality rate for 8 years was 0.061% and 0.13% for 30 day mortality, confirming that bariatric surgery is exceptionally safe in NHS England.


The first round of Consultant Outcomes Publication in 10 specialties, including bariatric surgery in the summer of 2013 followed a call for a culture of openness, transparency and candour form the Francis Report (2013) that dealt with the events leading up to the Mid Staffordshire inquiry. The NBSR publishes its 7th round of outcomes data for surgeons and units in the NHS in England.

Year Publication date
2012/13 2nd July 2013
2013/14 30th October 2014
2014/15 25 March 2016
2015/16 3rd February 2017
2016/17 15th August 2018
2017/18 1st August 2019


2017 saw the launch of version 2 of the NBSR reporting website for consultants. The NBSR Committee has repeated the outcome measures used for the 2017/18 COP report which includes:

  • Publishing the names of the hospitals whose total patient records were >10% fewer than they should  be according to HES
  • Adding the percentage of initial patient records that are ‘green for complete’
  • Sub-divides revision surgery into major and minor, so as to highlight the work of those who take on higher risk major revisions.

We are well aware of the lack of audit back up in many units and the first two are intended to support surgeons in their discussions locally.  Outcome 2 produces potential negative (and positive) outliers.

In addition to previous outcomes, NBSR has further broken-down gastric bypass procedures into Roux en Y gastric bypass and the One anastomosis Gastric Bypass/Mini Gastric Bypass (OAGB/MGB) which now features in Version 2 of the NBSR reporting website.


  • Total number of operations, broken down by common procedures (bands, sleeve gastrectomy, Roux en Y gastric bypass and one anastomosis gastric bypass/mini gastric bypass)
  • Proportion primary vs major revision vs minor revision
  • Data completion rates (‘green for complete’)
  • In-hospital mortality
  • The names of hospitals whose NBSR entries are more than 10% fewer than they should be  according to Hospital Episodes Statistics (HES) (poor case ascertainment)
  • Data completion rates for the initial in-patient record according to the proportion of records that are ‘green for complete’ for each surgeon
  • Reporting of revisional surgery rates according to major and minor, expressed as % of workload of each surgeon.


1.  Case ascertainment vs Hospital Episodes Statistics (HES)

We reprint here text from the 2013/14 report where we call for hospitals to provide sufficient administrative support to help their surgeons and bariatric teams with data entry:

‘‘It is evident that most NHS bariatric units still don’t have sufficient administrative support to ensure completeness of data entry and internal validation. Although the NBSR became mandatory for NHS providers from 1st April 2013, we remind hospital Trusts of their obligation to:

  • Verify and facilitate consultant and hospital-level engagement with national clinical audit; including providing resource for data validation
  • Respond to audit provider requests to check data accuracy and notification of outlying data
  • Work with clinicians and audit providers to use audit data ‘real-time’ for quality improvement
  • Promote the value of clinical audit across all work streams, not just those involved with COP5

Our view remains that it is insufficient to rely on individual clinicians alone to ensure there are no missing records, incomplete records or inaccurate data entry and thus possible under-reporting.’’

For this report we name the 8 hospitals whose records were more than 10% fewer than they should have been according to HES, excluding hospitals where there are 10 or fewer patients apparently missing:


In 2017/18 there were 8 hospitals with poor case ascertainment, in 2016/17 there were 8 hospitals, in 2015/16 there were 12 hospitals , in 2014/15 there were 7 and in 2013/14 there were 17.

Letters according to the policy on the BOMSS website are being sent to these hospitals to remind them of the requirement to provide sufficient administrative support for data entry, according to our policy: NBSR Policy for Managing Non-Contributions. It is possible that individual hospital coding issues are the reason for the apparent differences, and these need assessing locally. Although mandated in the NHS provider contracts, the NBSR committee has no further role other than pointing out the apparent lack of case input.

In addition to naming and sending letters to hospitals with more than 10% fewer patient records than indicated by HES, we again took an executive decision to exclude hospitals from this category if there were 10 or fewer cases missing.

The data have been interpreted with caution as the HES records may include non-bariatric operations or not detect all bariatric surgery. If the real volume of surgery was reported then it is likely that overall case ascertainment would be lower than 92%; thus we are confident to highlight the names of hospitals whose submissions are fewer than the actual total. We have no resource to investigate local reasons why submission may not be complete.

2.  Data completion rates – initial record ‘green for complete’

The First NBSR Report details the data fields that need to be completed to make the record go green 6.  If one or more field is missing the data record will remain yellow for incomplete.  The fields are:

Initial information
  • Weight
  • Height
  • Hospital name
  • Funding Category
Baseline comorbidity
  • ASA grade
  • Type 2 Diabetes and duration (where applicable)
  • Hypertension
  • Cardiovascular
  • Sleep apnoea
  • Asthma
  • Functional Status
  • Known risk factors for pulmonary embolus
Operation Record
  • Type Of Operation (Primary, Revision or Planned Second Stage)
  • Operative approach (Laparoscopic, Lap converted to Open, Open, Endoscopic)
  • Operation (select relevant choice)
  • For Revisions Prior Operation Type (where applicable)
Post-op course and discharge
  • Cardiovascular complications
  • Other complications
  • Discharge date
  • Discharged destination
‘Are the initial data complete’ button

Twenty-six surgeons remaining potential negative outliers for data completion and have been sent letters as per the policy published in 2013 on the BOMSS website 7. Note that the published data are for the 3 years 2016/19 and any records incomplete before the 2018/19 years will still be evident in the current reporting unless they have been updated. Thus a hospital with a local version of the database that was not collecting the relevant record for ‘green for complete’ before 2018/19 would not change its potential outlier status.

3. Primary and Revision surgery are here defined as
  • Primary surgery: the first bariatric operation
  • Minor revision: all operations for later complications of surgery, which may or may not involve laparoscopy or laparotomy, and includes band port and band removal procedures
  • Major revision: where one operation is converted to another bariatric operation, including planned second stage procedures

Minor revision surgery includes reoperations for complications of all bariatric procedures, ranging from more minor reoperations on for instance a subcutaneous gastric band port to more major reoperations for complications eg a leak from or stricture in a staple line, or bleed from a gastric bypass or sleeve gastrectomy. The definition also includes re-operations for internal hernia (twisted bowel) that can occur after some types of surgery. Operations such as cholecystectomy are not recorded as revisions with this definition.

Major revision surgery includes an operation for instance where a vertical banded gastroplasty (now obsolete) is converted to a gastric bypass, or a band procedure is added to a gastric bypass. Experienced surgeons may be more likely to perform more major revisional surgery, compared to younger, newly appointed consultants.

Future reports may sub-divide ‘Minor revision surgery’ into local procedures not involving laparoscopy/laparotomy, and more invasive procedures that involve laparoscopy/laparotomy since the current definition encompasses a wide range of invasiveness. Future reports may also include post-operative complications occurring within or after 30 days of the index procedure.


We use the same methodology to calculate in-hospital and 30-day mortality as for the 2013/17 reports 1-3. The definition of in-hospital death used for the NBSR and HES reporting is a death that occurs during the initial hospital stay before discharge. There were no statistical outliers for in-hospital deaths.

It is our policy that all mortalities related to bariatric surgery should be reported into the registry, but we are not able to comment on any mortality that is not. The policy concerning non-submission of mortality data is on the BOMSS website NBSR-Policy-for-Managing-Non-Contribution-of-Patient-Data-March-2015.pdf.

Overall, the NBSR data and the various HES analyses are entirely equivalent to a US benchmark, the American College of Surgeons Bariatric Surgery Center Network, where the published mortality rate was 0.12% (35 out of 28,616) for patients operated from 2007-10 8.


These are:

  • Consultant workload for primary and revision operations excluding gastric balloon placement
  • Operation split by consultant
  • BMI on entry into the weight loss programme
  • Co-morbidity count per type of operation (number of co-morbidities recorded per patient)
  • Obesity-Surgery Mortality Risk Score (OS-MRS) and class per operations and overall per consultant
  • Initial BMI overall per consultant (box and whiskers)
  • Length of stay for primary procedures compared to the rest per consultant
  • In-hospital mortality, described as survival

The co-morbidity count was taken from the NBSR dataset of co-morbidities:

  • Type 2 diabetes
  • Hypertension on treatment
  • Dyslipidaemia
  • Atherosclerosis (includes angina, MI, CABG, stroke, claudication)
  • Sleep apnoea
  • Asthma
  • Functional status (presence of comorbidity defined as unable to climb 3 flights of stairs without resting)
  • Back or leg pain from arthritis
  • GORD
  • Liver disease (suspected NAFLD or worse)
  • Poly-cystic ovarian syndrome (female patients only)
  • Depression (clinically significant depression as a reason for bariatric surgery)

The Obesity Surgery-Mortality Risk Score is the only validated measure of operative risk for patients undergoing bariatric surgery 9. A point is added for each of the following risk factors that are present, up to a maximum of 5 points: age at surgery ≥45 years, BMI ≥50 kg m2, male gender, recorded hypertension, one or more known risk factors for deep vein thrombosis (DVT) / pulmonary embolism (PE). Using the resultant score, complication & mortality rates can be risk-adjusted; the higher the score/group, the greater the risk of surgery. Patients can be stratified for risk according to how many of these risk factors are present. It is normal practice to refer to the calculated scores in three groups:

Group A (0-1 points)
Group B (2-3 points)
Group C (4-5 points)

We worked with the Quality Outcomes Research Unit in Birmingham University (QUORU) to analyse the HES data, and using a refined set of OPCS4 codes were able to estimate the mortality for primary bariatric surgery for the 3 years April 2012 – March 2016 previously highlighted (D McNulty, D Pagano, P Small, R Welbourn unpublished). Due to time limitations we were not able to analyse HES data for any other potential outcome.


Patients are able to search for hospitals by geography using an added map function and postcode. See the Frequently Asked Questions section on how to interpret this. As before, we present data for each outcome variable either as graphs, bar charts or box and whiskers graphs. Comments are included interpreting the results.

Additional notes:


We believe the 3-year data for 2016/19 are a correct representation of surgeon and hospital volume, baseline BMI, degree of baseline obesity-related disease, type of operation, mortality and length of stay.

NBSR Committee, 14th July 2020

Contact details

The NBSR administrators Sarvjit Wünsch or Nichola Coates are contactable by email or , telephone 0207 869 6941 or post to The National Bariatric Surgery Registry, The Royal College of Surgeons of England, 35-43 Lincoln’s Inn Fields, London WC2A 3PE.


So far over 70,000 individual patient records have been added since its inception in January 2009 and the First NBSR Report of aggregated operative and disease-related outcomes was published in April 2011 10. A Second NBSR Report of aggregated outcomes in 18,000 patients over 3 years was published in November 2014 11. The third NBSR Report is due for publication this year, 2020.


1Bariatric Surgeon-Level Outcomes Data 2013.

2The UK NBSR. Publication of surgeon-level data in the public domain for bariatric surgery in NHS England.

3The UK NBSR. Publication of surgeon-level data in the public domain for bariatric surgery in NHS England.

4The Francis Report 2013 Executive Summary

5HQIP Clinical Outcomes Publication programme 2016-2020.

6NBSR User Guide Summary July 09.pdf.

7NBSR Policy for Identification of Potential Outliers. June 2013. of-potential-outliers-June-2013.pdf

8Hutter MM, Schirmer BD, Jones DB et al. First Report from the American College of Surgeons Bariatric Surgery Center Network Laparoscopic Sleeve Gastrectomy has Morbidity and Effectiveness Positioned Between the Band and the Bypass. Ann Surg 2011; 254: 410–422.

9DeMaria EJ, Portenier D, Wolfe L. Obesity surgery mortality risk score: proposal for a clinically useful score to predict mortality risk in patients undergoing gastric bypass. Surgery for Obesity and Related Diseases. 2007; 3(2): 134-40.

10 First NBSR Report April 2011.

11Welbourn R, Sareela A, Small P et al. National bariatric surgery registry: second report. 2014 ISBN 978-0-9568154-8-4.



Policy for identification of potential outliers

It remains important to emphasise to patients that bariatric surgery is one episode in the lifelong chronic disease of obesity. All NHS surgeons work in well-developed multidisciplinary teams (MDTs) dedicated to the care of patients with severe and complex obesity. Our preference was to present outcomes data from units, since it is units that are commissioned to deliver services to patients, not individual surgeons.

Patients will be able to search for surgeons by name and hospitals by geography. We also show the overall operation volumes for each hospital as well as for each surgeon, which means the data are a more accurate reflection of the whole process of care.

We expect that patients will be able to use the data presented in the surgeon graphs to facilitate their consultations with the local bariatric team and help them make informed decisions about surgery.