Distinct Clinical and Outcome Profiles Across Six Subtypes of Acute Gastrointestinal Bleeding: A Comprehensive Analysis of 1021 Patients

<b>Background</b>: Acute gastrointestinal bleeding (GIB) remains a major clinical emergency with substantial morbidity, mortality, and healthcare burden. We aimed to provide a comprehensive characterization of all GIB subtypes, including iatrogenic bleeding, which is underrepresented in previous studies. <b>Methods</b>: In this ambidirectional cohort study, 1021 consecutive adults with overt GIB were enrolled from two Hungarian tertiary centers. Standardized data collection included demographics, comorbidities, medication use, bleeding source, and in-hospital outcomes: mortality, rebleeding, intensive care unit (ICU) admission, length of hospitalization (LoH), endoscopic evaluation and haemostatic intervention, red blood cell transfusion, and surgical intervention. Group comparisons were performed using appropriate statistical tests, and survival was analysed using Kaplan-Meier curves (R v4.4.2; <i>p</i> < 0.05). <b>Results</b>: Non-variceal upper GIB was the most common subtype (51.0%), followed by lower GIB (29.7%), variceal GIB (8.9%), small bowel bleeding (2.3%), and iatrogenic bleeding (7.5%). Overall, in-hospital mortality was 10.6%, highest in variceal bleeding (22%). Rebleeding occurred in 5.3% of cases, most frequently in variceal bleeding. ICU admission was required in 8.9% of patients, again, most common in variceal bleeding (21.6%). The median LoH was 7 days (IQR 4-10), significantly shorter in cases of intraprocedural iatrogenic bleeding. Endoscopy was performed in 91% of cases, with haemostatic intervention in 57%. Surgery was required in 3.4% of patients. <b>Conclusions</b>: Gastrointestinal bleeding represents a heterogeneous clinical entity with distinct outcome profiles across subtypes. Variceal bleeding was associated with the most unfavorable outcomes, whereas intraprocedural iatrogenic bleeding had a favorable course. These findings support subtype-specific clinical management and warrant validation in larger multicenter cohorts.