While every effort has been made to ensure the accuracy of all information contained on this website, Dendrite Clinical Systems Ltd do not accept liability arising from any errors or omissions or the use of or reliance on the information contained in this website and reserve the right to change information and descriptions as and when required.


The United Kingdom National Bariatric Surgery Registry

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 2015/16 to 2017/18 on The main results are summarised in the table below from the data cut taken on 1st April 2019, with the 2012/17 data copied through from the 2016/17 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 currently practising within the NHS for the 3 years reported in this Clinical Outcomes Publication(COP).

Number of surgeons submitting data
Number of hospitals
Number of NBSR operations recorded *
Number of primary operations
Total number of revision operations (%)






336 (6.1%)






432 (7.5%)






682 (12.0%)






648 (11.4%)






630 (11%)






588 (10.6%)







Number of NBSR primary operations and major revisions
HES recorded data (NBSR case ascertainment primary operations %)**
Recorded in-hospital mortality (%) ***
HES recorded in-hospital mortality (%)
ONS recorded 30-day mortality (%)



6,152 (84%)



14 (0%)






6 (0%)



5,393 (92%)


0 (0%)

5 (0%)



5,057 (100%)



6 (0%)



5,429 (100%)

1 (0.02%)


0 (0%)



5,641 (96%)

3 (0.05%)






* 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 previously 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 has 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






























NHS Total




The HES in-hospital mortality rate for 8 years was 0.063% and 0.071% for 30 days 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 summer 2013, followed a call for a culture of openness, transparency and candour from the Francis Report (2013) that dealt with the events leading up to the Mid Staffordshire inquiry 4.  The NBSR publishes its 6th round of outcomes data for surgeons and units in the NHS in England1-3

Publication date
2nd July 2013
30th October 2014
25th March 2016
3rd February 2017
15th August 2018
5th August 2019

Last year saw the launch of version 2 of the NBSR reporting website for consultants. The NBSR Committee has repeated the outcome measures used for the 2016/17 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 anatomosis 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 COP 5

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 the 2016/17 report we report the names of 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 2016/17 there were 8 hospitals with poor case ascertainment, in2015/16 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 ntribution-of-Patient-Data-March-2015.pdf. 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-four 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 2014/17 and any records incomplete before the 2016/17 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 2016/17 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 2014/17 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-Mar ch-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 2015/18 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, 1st August 2019

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.


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.



What does the report show?

It shows the centres that performed NHS bariatric surgery in 2012/15. The map facility allows you to search geographically and by postcode. The hospital unit volume of operations is shown, as well as the volume for the individual surgeons. Mortality data are shown as well as operation split, frequency of revision surgery and degree of obesity-related disease present and length of stay.

How do I access bariatric surgery?

Contact your GP in the first instance and ask for help with your weight problems. If your BMI is 35 or more and you have obesity-related disease that can be improved weight loss, or your BMI is 40 or more, you may be suitable for surgery. In March 2014 the RCS and BOMSS produced Commissioning Guidance that describes how this process works 13 .

Which unit should I be referred to?

Each region has well set-up bariatric surgery multidisciplinary teams with a full complement of specialists to help you with your care. These include dietitians, specialist nurses, physicians, surgeons and anaesthetists. Some patients may benefit from seeing psychologists and physiotherapists as well. The team will discuss with you whether surgery is a good option for you.

Not all the hospitals shown on the website are
bariatric surgery assessment centres (so called Tier 4 specialist centres), they may be hospitals contracted to do the actual surgery after full assessment by the local centre. It is important that you find out which service your local hospital offers. In addition due to local contracting it is possible that you will not have a choice about where you are sent for a bariatric surgery assessment or where the operation would then be done.

If you have a choice of surgery provider we encourage you to look at the data published for each hospital and discuss what it means with your GP.

Which operation should I have?

Discuss this with your surgical team. The expertise for different operations may vary from unit to unit and it is important that you are comfortable with the service you are being offered. Remember that bariatric surgery is one episode in a process of care of severe obesity, which is a lifelong chronic disease.

Does the number of operations a surgeon or unit performs make a difference to the success of surgery?

The BOMSS commissioning guide advises that units should have at least 2 surgeons and the annual volume of procedures should be at least 100 for the hospital and 40 for the individual surgeons. This is because in general for all specialised surgery the higher the caseload the better the operative results are likely to be. For bariatric surgery the staffing infrastructure is also likely to be better as all the required multidisciplinary team should be resourced and available. Read more about this on the BOMSS website 14

Some units may have only just been set up or a fully trained consultant surgeon may have only recently joined the unit. Both can explain why the presented numbers may be small.

Which questions should I ask the surgeon?

We would encourage you to ask about experience with particular operations, unit volume and reoperation rates for complications. We would encourage you to ask about how the MDT process works, which members you will meet and how you will be followed up after the surgery. All are important for the success of surgery long term.


Atherosclerosis – hardening of the arteries, including angina (chest pain due to insufficient blood reaching the heart), MI (myocardial infarction or heart attack), CABG (coronary artery bypass grafting), stroke, claudication (pain in the legs on walking due to insufficient blood reaching the leg muscles)

Bariatric – the medicine or surgery of weight problems

BMI – body mass index, calculated by dividing your weight in kg by the square of your height in metres, or kg/m2

BOMSS – British Obesity and Metabolic Surgery Society

Case ascertainment – the proportion of NHS operations recorded out of the total done

Dyslipidaemia – high cholesterol

GORD – Gastro-Oesophageal Reflux Disease

HES – Hospital Episode Statistics

MDT – multidisciplinary team

NAFLD – Non-Alcoholic Fatty Liver Disease

ONS – Office of National Statistics

Primary bariatric surgery – the first bariatric operation that a patient undergoes

Revision surgery (includes planned 2nd stage procedures) – a subsequent bariatric operation where the previous operation was performed in the same unit or in another hospital.  Revision surgery does not include reoperations for immediate postoperative complications

Roux en Y Gastric Bypass – the commonest form of gastric bypass, where a small stomach pouch is made and connected to a part of the small bowel (the ‘Roux limb’).  Continuity is restored by connecting the the Roux limb by a Y join to a lower part of the small bowel.  The remaining stomach is left undisturbed.

RCS – Royal College of Surgeons


While every effort has been made to ensure the accuracy of all information contained on this website, Dendrite Clinical Systems Ltd do not accept liability arising from any errors or omissions or the use of or reliance on the information contained in this website and reserve the right to change information and descriptions as and when required.



for NHS Bariatric Surgery

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Data analyses updated in
April 2019


The National Bariatric Surgery Registry is the result of a collaboration between ALSGBI (Association of Laparoscopic Surgeons of Great Britain and Ireland), AUGIS (Association of Upper Gastrointestinal Surgery), BOMSS (British Obesity & Metabolic Surgery Society) and Dendrite Clinical Systems. The key objective of the registry is to accumulate sufficient data to allow the publication of a comprehensive report on outcomes following bariatric surgery. This will include reportage on weight loss, co-morbidity and improvement of quality of life.


Tel: 020 869 6115/6116

British Obesity & Metabolic Surgery Society (BOMSS)
The Royal College of Surgeons of England
35-43 Lincoln's Inn Fields, London WC2A 3PE

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