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POSSUM and P-POSSUM

Also called POSSUM score, Portsmouth POSSUM, Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity

Physiological score (12 items) and operative severity score (6 items) converted to predicted 30-day morbidity and mortality for general surgery.

Age
Cardiac signs / chest X-ray
Respiratory signs / chest X-ray
Systolic BP (mmHg)
Pulse (beats/min)
Glasgow Coma Scale
Urea (mmol/L)
Haemoglobin (g/dL)
White cell count (× 10⁹/L)
Sodium (mmol/L)
Potassium (mmol/L)
ECG
Operative severity
Number of procedures
Total blood loss (mL)
Peritoneal soiling
Malignancy
Mode of surgery

Fill 18 more fields to see the result.

Formula and scoring

PS = sum of 12 physiological items (1/2/4/8; range 12–88); OS = sum of 6 operative items (range 6–48). POSSUM morbidity: ln[R/(1−R)] = −5.91 + 0.16·PS + 0.19·OS. POSSUM mortality: ln[R/(1−R)] = −7.04 + 0.13·PS + 0.16·OS. P-POSSUM mortality: ln[R/(1−R)] = −9.065 + 0.1692·PS + 0.1550·OS.

Exam and ward pearls

  • POSSUM is an audit tool: compare observed with expected deaths for a surgeon or unit, adjusted for case mix.
  • Score the physiology at the time of surgery and the operative items after the operation — so the full score is only known post-operatively.
  • Variants: CR-POSSUM (colorectal), V-POSSUM (vascular), O-POSSUM (oesophagogastric).

When not to rely on it

  • Some published tables print P-POSSUM as −9.37 + 0.19·PS + 0.15·OS; this page uses Prytherch 1998’s −9.065 + 0.1692·PS + 0.1550·OS.

Source

  1. Copeland GP, Jones D, Walters M. POSSUM: a scoring system for surgical audit. Br J Surg. 1991;78(3):355-60. doi:10.1002/bjs.1800780327 · PMID 2021856
  2. Prytherch DR, Whiteley MS, Higgins B, et al. POSSUM and Portsmouth POSSUM for predicting mortality. Br J Surg. 1998;85(9):1217-20. doi:10.1046/j.1365-2168.1998.00840.x · PMID 9752863
  3. Shekar N, Debata PK, Debata I, et al. Use of POSSUM and Portsmouth-POSSUM for surgical assessment in patients undergoing emergency abdominal surgeries. Cureus. 2023;15(6):e40850 (Table 1: full variable table). doi:10.7759/cureus.40850 · PMID 37489217
  4. Johns WL, Strong B, Kates S, Patel NK. POSSUM and P-POSSUM scoring in hip fracture mortalities. Geriatr Orthop Surg Rehabil. 2020;11:2151459320931674 (equations). doi:10.1177/2151459320931674 · PMID 32577320

Formula and cut-offs checked against these sources on 8 Nov 2026. Educational tool for clinicians; it does not replace clinical judgement.

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