Nationwide large-scale data of acute lower gastrointestinal bleeding in Japan uncover detailed etiologies and relevant outcomes: CODE BLUE J-Study

Background: The value of endoscopy for acute lower GI bleeding (ALGIB) remains unclear, given few large cohort studies. We aim to provide detailed clinical data for ALGIB management and to identify patients at risk for adverse outcomes based on endoscopic diagnosis. Methods: We conducted a multicenter, retrospective cohort study, named CODE BLUE J-Study, in 49 hospitals throughout Japan and studied 10,342 cases admitted for outpatient-onset of acute hematochezia. Results: Cases were mostly elderly, with 29.5% hemodynamic instability and 60.1% comorbidity. 69.1% and 87.7 % of cases underwent CT and colonoscopy, respectively. Diagnostic yield of colonoscopy reached 94.9%, revealing 48 etiologies, most frequently diverticular bleeding. During hospitalization, the endoscopic therapy rate was 32.7%, mostly using clipping and band ligation. IVR and surgery were infrequently performed, for 2.1% and 1.4%. In-hospital rebleeding and death occurred in 15.2% and 0.9%. Diverticular bleeding cases had higher rates of hemodynamic instability, rebleeding, endoscopic therapy, IVR, and transfusion, but lower rates of death and surgery than other etiologies. Small bowel bleeding cases had significantly higher rates of surgery, IVR, and transfusion than other etiologies. Malignancy or upper GIB cases had significantly higher rates of thromboembolism and death than other etiologies. Etiologies that have favorable outcomes were ischemic colitis, infectious colitis, and post-endoscopy bleeding. Conclusions: Large-scale data of patients with acute hematochezia revealed high proportions of colonoscopy and CT, resulting in high endoscopic therapy rates. We highlight the importance of colonoscopy in detecting accurate bleeding etiologies that stratify patients at high or low risk of adverse outcomes.