What are the causes and treatments of rectal bleeding?

Rectal Bleeding: Causes and Treatment

Immediate Assessment and Diagnostic Approach

All patients with rectal bleeding require at minimum anoscopy and flexible sigmoidoscopy, with complete colonoscopy indicated when bleeding is atypical for hemorrhoids, no anorectal source is evident, or significant risk factors for colonic neoplasia exist. 1

Initial Evaluation

• Perform digital rectal examination to exclude rectal masses (approximately 40% of rectal carcinomas are palpable) and confirm blood presence 2
• Assess pain characteristics: Postdefecatory pain suggests anal fissure (most common painful cause), while painless bleeding typically indicates internal hemorrhoids 1, 2
• Evaluate hemodynamic status: Check for orthostatic hypotension, tachycardia, or signs of significant blood loss requiring immediate resuscitation 2
• Obtain laboratory studies: Complete blood count, coagulation parameters, and type/crossmatch if hemodynamically unstable 2, 3

Critical Diagnostic Principle

Hemorrhoids alone do not cause positive fecal occult blood tests—never attribute occult blood or anemia to hemorrhoids until the colon is adequately evaluated, as anemia from hemorrhoids is extremely rare (0.5 per 100,000 population). 1, 4

Common Causes by Clinical Presentation

Painless Bright Red Bleeding

• Internal hemorrhoids (most common cause of painless rectal bleeding) 3
• Colorectal polyps or cancer (must be excluded via colonoscopy) 3
• Inflammatory bowel disease (ulcerative colitis was the leading cause in one diagnostic series with 46% prevalence) 5
• Diverticulosis and vascular dysplasia (account for 30-50% of moderate to severe colonic bleeding) 6

Painful Bleeding

• Anal fissure (cardinal symptom is postdefecatory pain with minor bleeding) 1, 2
• Thrombosed external hemorrhoids (acute-onset anal pain with palpable perianal lump) 1, 4
• Perianal abscess or anal fistula (requires external examination for detection) 1, 2

Post-Radiation Bleeding

• Radiation-induced telangiectasia occurs in 50% of patients after pelvic radiotherapy but impairs quality of life requiring intervention in fewer than 6% 1
• Telangiectases often heal spontaneously over 5-10 years 1
• Median time to onset is 13-18 months post-treatment, with Grade 3 bleeding having median symptom duration of 10 months 7

Treatment Algorithms

For Internal Hemorrhoids (Painless Bleeding)

First-line conservative management for all grades:

• Increase dietary fiber (psyllium husk 5-6 teaspoonfuls with 600 mL water daily) and adequate fluid intake 4
• Avoid straining during defecation 4
• Topical analgesics for symptom relief (lidocaine for pain/itching) 4
• Short-term corticosteroids (≤7 days only to avoid perianal tissue thinning) 4

Office-based procedures when conservative management fails:

• Rubber band ligation is the most effective office procedure for Grade I-III hemorrhoids with 70-89% success rates, superior to sclerotherapy and requiring fewer repeat treatments 4
• Infrared photocoagulation for Grade I-II hemorrhoids (67-96% success rates but requires more repeat treatments) 4
• Bipolar diathermy for Grade II hemorrhoids (88-100% success for bleeding control) 4

Surgical hemorrhoidectomy indications:

• Failure of medical and office-based therapy 4
• Symptomatic Grade III-IV hemorrhoids 4
• Anemia from hemorrhoidal bleeding (represents critical threshold demanding definitive surgical intervention) 4
• Mixed internal/external hemorrhoids 4
• Recurrence rate only 2-10% with surgery 4

For Thrombosed External Hemorrhoids (Painful Bleeding)

Within 72 hours of onset:

• Complete excision under local anesthesia provides fastest pain relief and lowest recurrence rates 1, 4
• Never perform simple incision and drainage—this causes persistent bleeding and higher recurrence 1, 4

After 72 hours or improving pain:

• Conservative management with stool softeners, oral analgesics, and topical treatments 1, 4
• Topical 0.3% nifedipine with 1.5% lidocaine applied every 12 hours for 2 weeks achieves 92% resolution versus 45.8% with lidocaine alone 4
• No systemic side effects with topical nifedipine 4
• Sitz baths to reduce inflammation 4

For Radiation-Induced Rectal Bleeding

Medical therapies with randomized trial evidence:

• Sucralfate enemas (supported by RCT) 1
• Metronidazole (used 4 weeks with corticosteroids and mesalazine; possibly contraindicated if chemotherapy-induced peripheral neuropathy exists) 1
• Vitamin A (retinol palmitate, small RCT) 1
• Hyperbaric oxygen therapy (RCT evidence, multiple case series) 1

Critical warning about argon plasma coagulation (APC):

• Despite being considered by many gastroenterologists as treatment of choice, serious complication rate may be as high as 26% including deep ulceration, bleeding, fistulation, perforation, stricture formation, and severe chronic pain 1
• APC frequently fails when bleeding is heavy 1
• Complications reflect risk of thermal therapy in chronically ischemic tissues 1

For Anal Fissure (Painful Bleeding)

• Conservative management first-line: Fiber supplementation, adequate fluids, sitz baths, topical analgesics 2
• Up to 20% of hemorrhoid patients have concomitant anal fissures 2

For Rectal Varices (Portal Hypertension)

Diagnostic approach:

• Endoscopic ultrasound with color Doppler precisely shows rectal venous plexus anatomy and hemodynamics 1
• CT scan can detect bleeding rates as low as 0.35 ml/min with 92% sensitivity, visualizes large serpiginous veins 1
• Urgent colonoscopy within 24 hours for high-risk features or ongoing bleeding 1

Treatment:

• Correction of underlying portal hypertension (transjugular intrahepatic portosystemic shunt for refractory bleeding) 1
• Local endoscopic procedures: Variceal ligation, band ligation, sclerotherapy, or EUS-guided glue injection 1
• Oversewing of varices if local therapy necessary (not excision) 1
• Standard hemorrhoidal treatments should NOT be used for variceal bleeding 1

Critical Pitfalls to Avoid

• Never assume all anorectal symptoms are hemorrhoids—up to 20% have concomitant anal fissures, and careful evaluation is essential 1, 4
• Never use corticosteroid creams >7 days—causes perianal tissue thinning and increased injury risk 4
• Never perform anal dilatation—52% incontinence rate at 17-year follow-up 4
• Avoid cryotherapy—causes prolonged pain, foul discharge, and greater need for additional therapy 4
• Do not delay colonoscopy when bleeding is atypical, patient has cancer risk factors, or no clear anorectal source identified 1, 3

When to Escalate Care

• Urgent colonoscopy within 24 hours for hemodynamic instability despite resuscitation, high-risk features, or ongoing bleeding 2
• Surgical consultation for suspected perianal abscess, thrombosed hemorrhoids within 48-72 hours with severe pain, or failure of conservative management 2
• Emergency evaluation for severe pain with high fever and urinary retention (suggests necrotizing pelvic sepsis) 4