Bright Red Blood Per Rectum: Causes and Diagnostic Approach
Bright red blood per rectum (hematochezia) most commonly originates from the lower gastrointestinal tract, particularly from anorectal sources, diverticulosis, angiodysplasia, or colitis, though severe upper GI bleeding can also present with bright red rectal bleeding in approximately 10-15% of cases. 1
Common Causes of Bright Red Rectal Bleeding
Anorectal sources - Hemorrhoids, anal fissures, and rectal ulcers are common causes of bright red blood per rectum, accounting for a significant portion of lower GI bleeding 1
Diverticulosis - One of the most common causes of lower GI bleeding, particularly in patients over 70 years of age, accounting for 20-40% of cases 1, 2
Angiodysplasia - Vascular malformations that can cause intermittent or acute bright red bleeding, representing 3-40% of lower GI bleeding cases 1
Colitis/Inflammatory conditions - Including inflammatory bowel disease, infectious colitis, radiation colitis, and ischemic colitis, accounting for 10-21% of cases 1, 3
Neoplasia - Colorectal cancer or polyps can present with bright red bleeding, representing 6-15% of cases 1
Upper GI sources - Approximately 10-15% of patients presenting with bright red rectal bleeding actually have an upper GI source, particularly when bleeding is brisk and associated with hemodynamic instability 1, 4
Diagnostic Approach Based on Hemodynamic Status
For Hemodynamically Unstable Patients (Shock Index >1):
Immediate CT angiography (CTA) should be performed as the first-line investigation to rapidly localize the bleeding site without requiring bowel preparation 1, 3
CTA has high sensitivity (79-95%) and specificity (95-100%) for detecting active bleeding, especially when the bleeding rate is 0.3-1.0 mL/min 1
If CTA does not identify a bleeding source, perform immediate upper endoscopy to exclude an upper GI source 1, 3
For Hemodynamically Stable Patients:
Direct anorectal examination (anoscopy/proctoscopy) should be performed first to identify common anorectal causes such as hemorrhoids or fissures 1, 3
Colonoscopy should be performed after adequate bowel preparation to enable thorough mucosal visualization 1
If colonoscopy is negative, consider upper endoscopy as 8-15% of patients with hematochezia may have an upper GI source 1, 4
Clinical Pearls and Pitfalls
Age is an important factor - Diverticulosis and angiodysplasia are more common causes of lower GI bleeding in patients over 70 years of age 1
Avoid delaying CTA in hemodynamically unstable patients by attempting colonoscopy first 1, 3
Digital rectal examination is crucial as approximately 40% of rectal carcinomas are palpable during this examination 1
Nasogastric tubes are not reliable for diagnosing upper GI bleeding, do not affect outcomes, and can cause complications 3
Most lower GI bleeding (approximately 90%) will cease spontaneously without intervention 2
Medication history is important as NSAIDs and anticoagulants can contribute to GI bleeding 1, 5
By following this structured approach based on hemodynamic status, clinicians can efficiently diagnose and manage patients presenting with bright red rectal bleeding, minimizing morbidity and mortality.