Clinical Outcomes 2016-17

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 2016-17  

Data is also available on the NHS Digital website.


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 2014/15 to 2016/17 on We use the same definitions of major and minor surgery as for previous years. The main results are summarised in the table below from the data cut taken on closure of version 1 of the NBSR on 2nd July 2018, with the 2012/16 data copied from the 2015/16 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 COP.


Year No of surgeons submitting data Number of Hospitals Number of NBSR operations recorded * Number of primary operations Total number of revision operations Number of major revisions Number of minor revisions
2012/13 120 74 5528 5192 336 (6.1%) 115 (2.1%) 221 (4.0%)
2013/14 139 69 5729 5297 432 (7.5%) 167 (2.9%) 265 (4.6%)
2014/15 140 70 5671 4989 682 (12%) 299 (5.3%) 383 (6.7%)
2015/16 146 65 5704 5056 648 (11.4%) 263 (4.6%) 367 (6.4%)
2016/17 166 82 5675 5085 630 (11%) 393 (6.9%) 237 (4.1%)
Total 28307 25619 2728 (9.6%) 1237 (4.4%) 1473 (5.2%)



Year 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 (%)
2012/13 5307 6152 (84%) 5 **** 14 (0%)
2013/14 5464 5597 (95%) 6 **** 6 (0%)
2014/15 5288 5393 (92%) 2 **** 5 (0%)
2015/16 5319 5057 (100%) 0 **** 6(0%)
2016/17 5478 5429 (100%) 1 (0.02%) **** 0 (0%)
Total 26856


* 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.

** 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 has noted 7 deaths between 2014 and 2017.

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 5044
2010/11 6 5945
2011/12 9 6376
2012/13 10 6103
2013/14 7 8 5556
2014/15 5367
2015/16 6 5045
2016/17 5316
NHS     Total 32 38 49417


The HES in-hospital mortality rate for 8 years was 0.065% and 0.077% 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 5th 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


This year saw the launch of the new NBSR reporting website for consultants. As a result of the work involved, and to prevent further delay of COP publication, the NBSR Committee has repeated the outcome measures used for the 2015/16 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.


  • Total number of operations
  • 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 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 2015/16 there were 12 hospitals with poor case ascertainment, 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-six surgeons remaining potential negative outliers for data completion at the 99.9% alarm level and 2 at the 99% alert level 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 2013/16 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 now 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 were contacted by Sunderland Royal Hospital where a substantial proportion of gastric bypasses are constructed using a loop technique, which could not be recorded in version 1 of the NBSR. A loop gastric bypass (One Anastomosis Gastric Bypass, OAGB) page is now in Version 2 of the NBSR to accommodate this changing UK practice.

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.