Assessing the Positive Predictive Value of International Classification of Diseases Code K55.0 for Identifying Acute Mesenteric Ischaemia

Background: Acute mesenteric ischaemia (AMI) includes acute superior mesenteric artery (SMA) thrombosis and embolism, venous AMI, and non-occlusive mesenteric ischaemia (NOMI). Patients with AMI are identified using the International Classification of Diseases (tenth revision (ICD-10)) code K55.0 (acute vascular disorders of the intestine). Reporting of outcomes depends on reliable case identification. Methods: A retrospective review of all patients assigned with ICD-10 code K55.0 at a tertiary university hospital between 1st January 2023 and 31st December 2025 was performed. Medical records and imaging findings were scrutinized to validate the diagnosis. Results: Among 218 patients assigned ICD-10 code K55.0, 117 (53.7%) had confirmed AMI and 198 (90.8%) had acute gastrointestinal ischaemia. Patients with NOMI (n = 30, 53.3%) had a higher bowel resection rate than patients with embolic SMA occlusion (n = 21, 23.8%; p = 0.039) or venous AMI (n = 15, 6.7%; p = 0.012). The in-hospital mortality rate was lower in patients with venous AMI (6.7%) than in patients with NOMI (66.7%; p < 0.003) or thromboembolic SMA occlusion (42.9%; p = 0.015). Conclusions: The positive predictive value for AMI using ICD-10 code K55.0 was 53.7%, underscoring the need for validated case identification. The heterogeneity of diagnoses captured by this code supports consideration of a more granular ICD coding system. A conceptual proposal is presented for further discussion and validation.