Current ESGE guidelines recommend urgent colonoscopy only in selected patients with acute lower gastrointestinal bleeding (LGIB), based mainly on bleeding severity and likelihood of finding stigmata of recent hemorrhage. However, they do not clearly differentiate recommendations according to the underlying clinical scenario. Since LGIB is a highly heterogeneous condition, we aimed to evaluate whether the diagnostic and therapeutic effectiveness of urgent colonoscopy differs among distinct patient populations.

We conducted a retrospective single-centre study in a tertiary referral hospital with 24/7 endoscopic availability. All urgent colonoscopies (<24 hours from request) performed for acute LGIB between July 2018 and August 2025 were analysed. Procedures were classified as diagnostic if the bleeding source or stigmata of recent haemorrhage were directly identified, and as therapeutic if endoscopic hemostasis was performed. Patients were stratified into three clinical cohorts: (1) colon-naïve patients, (2) post-polypectomy bleeding, and (3) post-surgical bleeding. The primary outcome was in-hospital mortality. Secondary outcomes included diagnostic yield, therapeutic yield, and rebleeding.

Among 415 urgent colonoscopies, 224 patients undergoing colonoscopy within 24 hours for LGIB were included: 129 colon-naïve, 52 post-polypectomy, and 43 post-surgery. Overall diagnostic and therapeutic yields were 58% and 44%, respectively, but showed marked differences across cohorts. Diagnostic yield was significantly lower in colon-naïve patients (40%) compared with post-polypectomy (88%) and post-surgical patients (77%)(p<0.001). Similarly, therapeutic yield (endoscopic hemostasis) was 21% in colon-naïve patients, versus 87% in post-polypectomy and 63% in post-surgical patients (p<0.001).

On multivariable analysis, clinical scenario (population subgroup) was the strongest independent predictor of both diagnostic and therapeutic outcomes with odds ratio (OR) up to 24.5 for haemostasis in the post-polypectomy subgroup, and up to 6.28 in the post-surgery subgroup (p<0.001), while age, sex, and quality of bowel preparation were not.

In-hospital mortality was 9.8%. A multivariable Cox proportional hazards survival analysis was performed, adjusting for age, sex, clinical scenario, and ASA class. In this model, neither diagnostic nor therapeutic endoscopic outcomes were significantly associated with mortality, whereas ASA class emerged as the only independent predictor of mortality with hazard ratio (HR) of 2.74 and 2.81 respectively, (p=0.01).

Notably, rebleeding rates were similar across the three clinical cohorts (p=0.5) and between patients on or off antithrombotic therapy (p=0.66), with only transfusion requirement (61% vs 85%, p=0.001) and prolonged hospitalisation (9 vs 20 days, p=0.01) showing significant associations.

Compared with previously published data on urgent colonoscopy in acute LGIB, our cohort showed markedly higher diagnostic and therapeutic yields even in the colon-naïve subgroup, further supporting the high effectiveness of urgent colonoscopy in our setting with 24/7 endoscopic availability. However, this effectiveness was not uniform across all patients and was strongly influenced by the underlying clinical scenario. In particular, patients with post-surgical bleeding and post-polypectomy had substantially higher diagnostic and therapeutic yields than colon-naïve patients. These results highlight a critical gap in current guidelines, which do not adequately differentiate among patient subgroups, and support the need for a more tailored, scenario-based approach when selecting candidates for urgent colonoscopy in acute LGIB.

As for rebleeding events, no strong independent predictors were identified; the only observed associations — with transfusions and prolonged hospitalisation — likely reflect secondary consequences rather than causal factors.

Moreover, our findings indicate that short-term survival in acute LGIB is primarily driven by baseline patient comorbidity rather than by endoscopic outcomes, reinforcing the concept that patient-related factors outweigh procedural factors in determining prognosis, not only in randomised controlled trials but also in real-life clinical practice.