Skip to main content
EN → RO

CR-POSSUM Calculator

Estimating operative risk in colorectal surgery

CR-POSSUM (Colorectal Physiological and Operative Severity Score) estimates the risk of perioperative mortality in colorectal surgery, based on six physiological parameters and four parameters related to the operation. It was developed by Tekkis and colleagues in 2004, specifically for colon and rectal surgery, and is more accurate than the general POSSUM model for this type of procedure.

A tool intended for medical professionals.

Three of the four operative variables (operative severity, peritoneal soiling, cancer staging) are only known during or after surgery. CR-POSSUM is first and foremost a tool for surgical audit and for risk adjustment between centres — not a calculator for preoperative patient counselling.

The model systematically overpredicts risk in modern practice. In the Spanish CCR-CARESS validation (2749 patients), observed mortality was 1.5%, while the model predicted roughly four times as much. The development data come from the United Kingdom, 1993–2001.

A Physiological score 6 – 23 points

years

≤ 60 years = 1 point; 61–70 = 3; 71–80 = 4; ≥ 81 = 8 points.

Cardiac failure

Anchoring to the NYHA classification is an implementation convention; the original paper does not detail the criteria for each grade.

mmHg

100–170 = 1 point; 90–99 or > 170 = 2; < 90 = 3 points.

beats/min

40–100 = 1 point; 101–120 = 2; > 120 or < 40 = 3 points.

g/dL

13.0–16.0 = 1 point; 10.0–12.9 or 16.1–18.0 = 2; < 10.0 or > 18.0 = 3 points.

≤ 10.0 mmol/L = 1 point; 10.1–15.0 = 2; > 15.0 = 3 points. Note: this field expects serum urea, not blood urea nitrogen (BUN). The conversion used is mg/dL ÷ 6.006. If your laboratory reports BUN, multiply it by 2.14 first to obtain urea.

B Operative severity score 4 – 22 points

Operative severity

The allocation of procedures to classes differs slightly between published sources. Choose the class on clinical judgement if the procedure is not listed.

Peritoneal soiling
Operative urgency

The exact definitions used in the original paper are not reproduced in the secondary sources; those above follow the POSSUM convention and the Spanish validation.

Cancer staging

The original model uses the Dukes classification. The TNM equivalents are indicative only.

Complete preoperative assessment

CR-POSSUM measures operative risk. For the impact of comorbidities there is the Charlson index, and for nutritional status, the NRS-2002 score.

Charlson Index → NRS-2002 Score →

Scientific references

Tekkis PP, Prytherch DR, Kocher HM, et al. Development of a dedicated risk-adjustment scoring system for colorectal surgery (colorectal POSSUM). Br J Surg. 2004;91(9):1174-1182. PubMed

Bare M, Mora L, Torà N, et al. Validity of the CR-POSSUM model in surgery for colorectal cancer in Spain (CCR-CARESS study) and comparison with other models to predict operative mortality. BMC Health Serv Res. 2018;18(1):49. PMC

Equation used: ln[R / (1 − R)] = −9.167 + (0.338 × physiological score) + (0.308 × operative score), where R is the mortality risk. The model has a floor of 0.27% and a ceiling of 99.5% — it can never return a risk of zero. CR-POSSUM estimates mortality only; there is no validated equation for morbidity, despite the name.