What causes rectal bleeding?

Generally, blood found during bowel movements may be caused by hemorrhoids, anal fissures, colorectal polyps, ulcerative colitis, or colorectal cancer. It is recommended to seek timely medical evaluation at a hospital to determine the underlying cause and receive targeted treatment. Specific analyses are as follows:

1. Hemorrhoids

Swollen vascular cushions in the anus can be scraped by hard stools, resulting in variable amounts of bleeding, typically seen as dripping blood or blood on toilet paper. Symptoms usually resolve within several days by increasing dietary fiber intake, drinking 2000 mL of water daily, cleaning with warm water after defecation, and using topical agents containing hydrocortisone or diosmin.

2. Anal Fissure

Small lacerations in the anal canal lining cause minimal bleeding but sharp, knife-like pain; constipation is the primary trigger. Short-term use of compound ointments containing lidocaine as prescribed, sitz baths with 38°C potassium permanganate solution, and maintaining soft stools typically lead to healing within two weeks. If pain persists beyond one month, chronic anal fissure should be ruled out.

3. Colorectal Polyps

Polyps with surface erosion may cause intermittent bright red blood or occult blood in stool, often without discomfort. Adenomatous polyps are precancerous lesions and should be removed via endoscopy upon detection, followed by pathological examination. Follow-up colonoscopies every 1 to 3 years after removal can reduce the risk of cancer development.

4. Ulcerative Colitis

Classic symptoms include mucous bloody diarrhea, crampy abdominal pain, and tenesmus. Diagnosis relies on colonoscopy and histopathology. Mild to moderate cases are primarily treated with 5-aminosalicylic acid (5-ASA) preparations; severe or extensive disease may require corticosteroids or biologic agents for induction of remission. During flare-ups, a low-residue, low-lactose diet is advised, along with avoidance of alcohol and spicy foods.

5. Colorectal Cancer

Bleeding from tumor ulceration is typically dark red and mixed with stool, often accompanied by changes in bowel habits and weight loss. Individuals aged 45 or earlier (if there’s a family history) should undergo fecal immunochemical testing every 1–2 years. A positive result requires immediate colonoscopy. Early-stage lesions can be cured through endoscopic resection or surgery, with over 90% five-year survival rate.

Keep a record of the color and frequency of bleeding, as well as associated symptoms, and avoid self-medicating with hemostatic drugs. Seek medical attention within 24 hours if bleeding recurs or is heavy, or if symptoms such as syncope or persistent abdominal pain occur. Evaluation by a gastroenterology specialist, including colonoscopy and other tests, is essential to rule out serious organic diseases.