POSSUM for Operative Morbidity and Mortality Risk
Use values at the time of surgery, not admission.
NOTE: The POSSUM should not be used for trauma patients.
Patients undergoing emergency and elective general surgical procedures.
- The Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (POSSUM) assesses morbidity and mortality for general surgery.
- It can be used for both emergency and elective surgery.
- The original POSSUM was modified by researchers in Portsmouth who derived a more accurate prediction of mortality, and the P-POSSUM model is now more commonly used to calculate the mortality component.
- The POSSUM data set excludes trauma patients, so POSSUM should NOT be used to predict morbidity and mortality after trauma surgery.
- The POSSUM should NOT dictate the decision to operate, which is a clinical decision.
- Physiological score should be calculated at the time of surgery, not at the time of admission.
- The definitions of surgical procedures are guidelines only. Not all procedures are listed, and the closest approximation should be selected.
- The POSSUM may overestimate risk in hepatopancreaticobiliary surgery.
The POSSUM calculates risk for operative morbidity and mortality, which can be used to help patients and family members make informed decisions about surgery.
Similar / alternative tools:
- There are procedure-specific models for colorectal surgery (CR-POSSUM), vascular surgery (Vascular-POSSUM), and esophagogastric surgery (O-POSSUM, O for oesophagogastric).
- APACHE II is a similar assessment tool but is applied to intensive care patients and only assesses the risk of mortality.
- The Surgical Apgar Score (SAS) offers similar estimates for morbidity and mortality.
- The POSSUM is more comprehensive than the SAS (which is calculated based on 3 parameters), but the SAS is more objective.
- The SAS uses intraoperative parameters exclusively, whereas the POSSUM uses preoperative parameters.
- The ACS NSQIP risk calculator is a newer, similar assessment. It has not yet been as rigorously validated as the POSSUM.
- Other disease-specific scores may be used to assess risk, e.g. Revised Cardiac Risk Index for Pre-Operative Risk.
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Risk estimates can help patients and family members in the process of informed consent and in management of expectations.
The POSSUM should be calculated when the decision to operate is made. The percentages can be shared with the patient when discussing the risks of the operation.
Addition of selected points.
NOTE: Physiological score and operation severity score are weighted differently.
“Under the Respiratory component of the Physiological Severity Score, xray changes are in addition to the clinical findings, and the latter are more important,” according to Dr. Copeland (creator of the POSSUM). See our interview under “From the Creator” for more of Dr. Copeland's insights.
Facts & Figures
Severity of surgeries:
- Moderate: appendectomy, cholecystectomy, mastectomy, TURP
- Major: laparotomy, bowel resection, cholecystectomy w choledochotomy, peripheral vascular procedure or major amputation
- Major+: aortic procedure, abdominoperineal resection, pancreatic or liver resection, esophagogastrectomy
Morbidity was defined as any of the following:
- Infection (including pneumonia, wound infection, UTI, deep infection, septicemia, and fever of unknown origin)
- Wound dehiscence or anastomotic leak
- Thrombosis (including) DVT, PE, CVA, or MI
- Cardiac failure
- Impaired renal function (urea increase >5 mmol/L from pre-op)
- Hypotension (respiratory failure)
- “Any other complication”
- The POSSUM was originally developed by Copeland and colleagues in 1991 to assess quality of care and provide a scoring system for surgical audit.
- Physiological and operative severity score data were obtained from 1,372 patients who underwent elective or emergency surgery from August 1988 to February 1989 at Walton Hospital in Liverpool, UK.
- Logistic regression analysis yielded statistically significant equations for morbidity and mortality, e.g. POSSUM score.
- The POSSUM’s predicted risk correlates well with observed rates for mortality and morbidity (p < 0.001).
- The original POSSUM was modified to the Portsmouth POSSUM, or P-POSSUM, in 1998 by Prytherch and colleagues, who derived a more accurate prediction for the mortality component.
- The study showed that the original POSSUM logistic regression equation for mortality overpredicted the overall risk of death by more than twofold and the risk of death for patients at lowest risk (5% or less) by more than sevenfold.
- Both the POSSUM and P-POSSUM slightly overestimate both morbidity and mortality.
- Since the original publication of POSSUM, the score has been modified and validated for numerous subtypes of surgeries and clinical scenarios, including:
- Colorectal surgery
- Vascular surgery
- Oncologic gastric surgery
- Emergency laparotomy
- Orthopedic surgery
Original/Primary ReferenceCopeland GP, Jones D, Walters M. POSSUM: a scoring system for surgical audit. Br J Surg 1991;78(3):355-60.Prytherch DR, Whiteley MS, Higgins B, Weaver PC, Prout WG, Powell SJ. POSSUM and Portsmouth POSSUM for predicting mortality. Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity. Br J Surg 1998 Sep;85(9):1217-20.
ValidationRamkumar T, Ng V, Fowler L, Farouk R. A comparison of POSSUM, P-POSSUM and colorectal POSSUM for the prediction of postoperative mortality in patients undergoing colorectal resection. Dis Colon Rectum. 2006 Mar;49(3):330-5.Tez M, Yoldaş O, Gocmen E, Külah B, Koc M. Evaluation of P-POSSUM and CR-POSSUM scores in patients with colorectal cancer undergoing resection. World J Surg. 2006 Dec;30(12):2266-9.Lam CM, Fan ST, Yuen AW, Law WL, Poon K. Validation of POSSUM scoring systems for audit of major hepatectomy. Br J Surg. 2004 Apr;91(4):450-4.Mohil RS, Bhatnagar D, Bahadur L, Rajneesh, Dev DK, Magan M. POSSUM and P-POSSUM for risk-adjusted audit of patients undergoing emergency laparotomy. Br J Surg. 2004 Apr;91(4):500-3.van Zeeland ML, Genovesi IP, Mulder JW, Strating PR, Glas AS, Engel AF. POSSUM predicts hospital mortality and long-term survival in patients with hip fractures. J Trauma. 2011 Apr;70(4):E67-72.Chen T, Wang H, Wang H, Song Y, Li X, Wang J. POSSUM and P-POSSUM as predictors of postoperative morbidity and mortality in patients undergoing hepato-biliary-pancreatic surgery: a meta-analysis. Ann Surg Oncol. 2013 Aug;20(8):2501-10.
From the Creator
- Why did you develop the POSSUM? Was there a clinical experience that inspired you to create this tool for clinicians?
- I developed it originally to act as an audit aid for the retrospective review of adverse outcomes and then realised that it could be used as a measure of surgeon quality.
- Are there any pearls, pitfalls, or tips you have for surgeons using POSSUM to assess operative risk for their patients?
- Its main use is in pre-op assessment to give patients and relatives a more realistic expectation of the post-operative course.
- Are there cases when it has been applied, interpreted, or used inappropriately?
- I have never heard of anyone using it as a 'futility index' (i.e., a reason to avoid a necessary surgery), but that remains a potential risk.
- How do you think the POSSUM compares to other similar assessments?
- I have looked at the ACS NSQIP risk calculator and have found that, as it depends on surgeon-declared data, it often under-estimates risk, as compared to coded-derived data, which may be a more independent assessment. If these underestimated predictions are communicated to patients, this may cause a future potential problem.
About the Creator
Graham Copeland, MBBS, is a consultant general surgeon at Broadgreen Hospital in Liverpool. Graham has been an advisor to the Healthcare Commission and the National Institute of Clinical Effectiveness in the United Kingdom. Dr. Copeland's research focuses on clinical audits and outcome measures in surgical settings.
To view Dr. Graham Copeland's publications, visit PubMed
- Jennie Kim, MD