Development and external validation of prediction risk scores (STRISK and NOFA) to predict immediate surgical need in adhesive small bowel obstruction: an observational prospective multicentre study.

Background: Adhesive small bowel obstruction (SBO) is a common cause of emergency admission. Identification of patients at high risk of strangulation or failure of non-operative treatment is difficult. In this multicentre prospective observational study, prediction models for strangulation and non-operative treatment failure in adhesive SBO were developed.

Method: This study was carried out in three Finnish hospitals between June 2014 to May 2022. Patients with CT-confirmed adhesive SBO and prospective case report forms were included. The main outcomes were strangulation defined by operative finding of any intestinal ischaemia and failure of non-operative treatment within 30 days from admission. The model was developed using binary logistic regression, internally validated by bootstrapping and then externally validated.

Results: Of 626 patients, 481 were included; 355 patients formed the model development group and 126 formed the external validation group. Strangulation occurred in 58 (16%) patients and non-operative treatment failed in 93 (31%) patients in development cohort. The following six variables were included in the risk model for strangulation and non-operative treatment failure: neutrophil-leucocyte ratio, number of previous SBOs, abdominal guarding, mesenteric changes and free abdominal fluid, closed loop sign, and faeces sign on CT. In the development cohort, the optimism corrected area under the receiver operator characteristics curve for the strangulation model was 0.860 (95% c.i. 0.808-0.917), and 0.751 (95% c.i. 0.694-0.816) for the non-operative treatment failure model respectively. At external validation, the models retained their discrimination and demonstrated stable calibration.

Conclusion: A clinically relevant prediction model to predict strangulation and non-operative treatment failure in adhesive small bowel obstruction has been developed.