Lower Gastrointestinal Bleeding: Causes and What You Need to Know

Gastrointestinal (GI) bleeding is a medical condition that can originate from any part of the digestive tract. When the bleeding occurs in the lower portion of the gastrointestinal system—such as the large intestine, rectum, or anus—it is referred to as lower gastrointestinal bleeding (LGIB). This type of bleeding can range from mild to life-threatening and should never be ignored. Understanding the causes, symptoms, and when to seek medical help is crucial for timely treatment and recovery.

What Is Lower Gastrointestinal Bleeding?

Lower gastrointestinal bleeding specifically refers to bleeding that occurs distal to the ligament of Treitz, the anatomical boundary between the upper and lower GI tract. It often presents as visible blood in the stool (hematochezia), which may appear bright red or maroon in color, indicating relatively fresh blood.

While occasional minor bleeding might not always signal a serious problem, persistent or heavy bleeding requires prompt medical evaluation.

Common Causes of Lower GI Bleeding

Several conditions can lead to bleeding in the lower digestive tract. Some of the most frequent causes include:

1. Hemorrhoids

Hemorrhoids are swollen veins in the rectum or anus and are one of the most common causes of mild rectal bleeding. They can be internal or external and often cause painless bleeding during bowel movements, with bright red blood on toilet paper or in the toilet bowl.

2. Anal Fissures

Anal fissures are small tears in the lining of the anus, usually caused by passing hard or large stools. They can result in sharp pain during defecation and small amounts of bright red blood.

3. Diverticular Disease

Diverticulosis, the presence of small pouches (diverticula) in the colon wall, is common in older adults. When these pouches become inflamed or bleed, it's known as diverticulitis or diverticular bleeding. This condition is a leading cause of significant lower GI bleeding, especially in people over 60.

4. Inflammatory Bowel Disease (IBD)

Conditions such as ulcerative colitis and Crohn’s disease fall under IBD. These chronic disorders cause inflammation and ulceration in the digestive tract, frequently leading to bloody diarrhea, abdominal pain, and weight loss.

5. Colorectal Polyps and Cancer

Polyps are abnormal growths in the colon lining. Some can develop into cancer over time. Both polyps and colorectal cancer can cause occult (hidden) or visible bleeding. This is why routine colon cancer screening is essential, especially for individuals over 50 or those with a family history.

6. Infectious Colitis

Certain bacterial, viral, or parasitic infections can inflame the colon, leading to bloody diarrhea. Common culprits include Salmonella, Shigella, Campylobacter, and Escherichia coli (E. coli).

7. Ischemic Colitis

Reduced blood flow to the colon—often due to blocked or narrowed blood vessels—can cause ischemic colitis. This condition is more common in older adults and typically presents with sudden abdominal pain and bloody stools.

8. Angiodysplasia

This condition involves abnormal, fragile blood vessels in the lining of the colon that can rupture and cause bleeding, especially in elderly patients. It's a common cause of unexplained GI bleeding in older adults.

Symptoms to Watch For

Symptoms of lower GI bleeding may include:

• Bright red or maroon-colored blood in the stool
• Blood on toilet paper after wiping
• Rectal pain or discomfort
• Dizziness, weakness, or fatigue (signs of significant blood loss)
• Abdominal pain or cramping
• Changes in bowel habits (diarrhea or constipation)

When to See a Doctor

Seek immediate medical attention if you experience:

• Large amounts of blood in your stool
• Continuous bleeding
• Signs of anemia (pale skin, shortness of breath, fatigue)
• Severe abdominal pain
• Dizziness or fainting

Even mild or occasional bleeding should be evaluated by a healthcare professional to determine the underlying cause and prevent complications.

Diagnosis and Treatment

Doctors use a combination of medical history, physical exams, and diagnostic tests to identify the source of bleeding. Common procedures include:

• Colonoscopy: Allows direct visualization of the colon and rectum, and can be used to treat certain causes of bleeding.
• Sigmoidoscopy: Examines the lower part of the colon.
• Imaging studies: CT scans or angiography may be used in acute cases.
• Stool tests and blood work: To check for infection or anemia.

Treatment depends on the cause and severity of the bleeding. Options may include medications, lifestyle changes (such as a high-fiber diet), minimally invasive procedures, or surgery in severe cases.

Prevention Tips

• Maintain a high-fiber diet to prevent constipation and straining.
• Stay well-hydrated.
• Avoid prolonged sitting on the toilet.
• Exercise regularly.
• Follow screening guidelines for colorectal cancer.
• Manage chronic conditions like IBD or cardiovascular disease under medical supervision.

Final Thoughts

Lower gastrointestinal bleeding is a symptom—not a disease—and identifying its root cause is essential for effective treatment. While some causes like hemorrhoids are benign and easily managed, others may indicate serious conditions such as colorectal cancer. Never ignore rectal bleeding, and consult your doctor promptly for an accurate diagnosis and appropriate care.

Your digestive health matters. Early detection and intervention can prevent complications and save lives.