💉 Understanding Lower GI Bleeding

Lower gastrointestinal (GI) bleeding is defined as bleeding originating distal to the ligament of Treitz, typically from the colon, rectum, or anus. It presents most commonly as hematochezia—bright red or maroon-colored blood in the stool—and can range from minor bleeding to massive hemorrhage. Prompt identification of the bleeding source is critical for stabilizing the patient and preventing complications.

🩸 Common Causes of Lower GI Bleeding

The illustration highlights five key pathological mechanisms responsible for lower GI bleeding:

1. Hemorrhage (①) – Usually due to diverticulosis or angiodysplasia, where fragile vessels rupture under pressure.

2. Fistula (②) – An abnormal passage, such as a colovesical fistula, often seen in Crohn’s disease or post-surgical complications.

3. Inflammation (③) – Caused by ulcerative colitis, infectious colitis, or ischemic colitis leading to mucosal erosion.

4. Abscess (④) – A localized infection that can erode blood vessels and cause both pain and bleeding.

5. Perforation (⑤) – A full-thickness rupture of the intestinal wall, which can lead to peritonitis and sepsis—an emergency condition.

🧠 Diagnosis and Management

Lower GI bleeding is typically evaluated using colonoscopy, which serves both diagnostic and therapeutic purposes. In unstable patients, CT angiography helps identify active bleeding sites. Treatment may involve endoscopic hemostasis, embolization, or surgical resection, depending on severity. Supportive care includes IV fluids, blood transfusions, and monitoring hemodynamic stability.

⚖️ Upper vs. Lower GI Bleeding – Comparison Table

Feature	Upper GI Bleed	Lower GI Bleed
Anatomical Source	Esophagus, stomach, duodenum	Colon, rectum, anus
Appearance of Stool	Melena (black, tarry stool)	Hematochezia (bright red or maroon)
Common Causes	Peptic ulcers, varices, gastritis	Diverticulosis, hemorrhoids, IBD
Diagnostic Tool	Upper endoscopy (EGD)	Colonoscopy or CT angiography
Treatment Approach	Proton pump inhibitors, endoscopic banding	Endoscopic cauterization; surgery if severe

🧬 Complications and Prognosis

Untreated lower GI bleeding can lead to chronic anemia, hemodynamic shock, or infection in cases involving abscesses or perforations. The prognosis depends on the underlying cause and timeliness of intervention. Early diagnosis not only improves patient outcomes but also prevents recurrence through appropriate management and follow-up.

📚 Clinical Insight

In exams and real-life scenarios, differentiating upper vs. lower GI bleeding is essential. Remember: bright red blood = distal source, while dark, tarry stool = proximal source. Clinicians must also consider mixed presentations in cases of massive upper GI bleeds that rapidly transit through the intestines.

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At King of the Curve, we make complex medical concepts simple, visual, and unforgettable. From anatomy to pathology, our high-yield illustrations and quizzes help students prepare smarter for exams like the MCAT, USMLE, and NCLEX.

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