Hematochezia: A Comprehensive Guide to Differential Diagnosis

Rectal bleeding, clinically termed hematochezia, is a common presenting complaint in outpatient settings, signaling potential pathologies from the proximal lower gastrointestinal tract to anorectal diseases like hemorrhoids, fissures, proctitis, and malignancies. Despite its prevalence and potential severity, a significant number of individuals experiencing rectal bleeding do not seek medical advice. This article provides an in-depth review of hematochezia, focusing on its differential diagnosis, evaluation, and management, aiming to enhance understanding for healthcare professionals.

Etiologies of Hematochezia: A Broad Spectrum

Hematochezia, characterized by the passage of bright red blood per rectum, predominantly originates from the lower gastrointestinal (GI) tract, defined as distal to the ligament of Treitz. However, brisk upper GI bleeds can also manifest as hematochezia due to rapid transit, limiting blood digestion. Understanding the diverse etiologies is crucial for accurate differential diagnosis.

Lower Gastrointestinal Tract Origins

Colorectal Cancer: Neoplastic proliferation within the colon or rectum can lead to fragile new blood vessels that are prone to bleeding. While representing a smaller percentage of hematochezia cases, colorectal cancer is a critical differential, especially in older adults, necessitating thorough exclusion.
Inflammatory Bowel Disease (IBD): Chronic inflammatory conditions such as ulcerative colitis and Crohn’s disease often present with rectal bleeding, accompanied by symptoms like diarrhea and abdominal pain. The inflammatory process directly affects the mucosal lining, making it vulnerable to bleeding.
Diverticular Disease: Diverticula, outpouchings in the colonic wall, commonly harbor weakened blood vessels. Rupture of these vessels can result in significant, often painless, hematochezia. Diverticular bleeding is a frequent cause of lower GI bleeding in the elderly.
Hemorrhoids: These vascular cushions in the anal canal are a leading cause of hematochezia, particularly in middle-aged and older populations. Hemorrhoids are classified as internal, external, or mixed, and graded based on prolapse severity (Goligher’s classification). Internal hemorrhoids typically cause painless bleeding, often described as bright red blood with bowel movements.
Anal Fissures: Tears in the anal canal lining, frequently caused by constipation or childbirth, are a common source of rectal bleeding. Anal fissures are characteristically associated with sharp anal pain during defecation and blood streaked stools.
Infections: Various infectious agents can induce proctitis and subsequent rectal bleeding. Sexually transmitted infections (STIs) like Neisseria gonorrhoeae, Chlamydia trachomatis, Herpes Simplex Virus (HSV), and Treponema pallidum, as well as enteric pathogens such as Escherichia coli and Clostridium difficile (causing hemorrhagic colitis), should be considered in the differential diagnosis, especially in at-risk populations.

Upper Gastrointestinal Tract Origins

While melena (black, tarry stools) is more typical of upper GI bleeding, massive upper GI bleeds can present as hematochezia. This occurs because the sheer volume of blood overwhelms the digestive capacity of the upper GI tract, and the cathartic effect of blood accelerates transit time, minimizing the conversion of hemoglobin to acid hematin. Conditions like Mallory-Weiss tears, esophageal varices, and perforated gastroduodenal arteries, when bleeding profusely, can manifest as hematochezia. Furthermore, individuals with achlorhydria may also present with hematochezia from upper GI sources due to reduced gastric acid conversion of blood.

Systemic Causes

It is crucial to consider systemic factors that might exacerbate or cause GI bleeding, including bleeding diatheses. Conditions such as vitamin K deficiency, hemophilia, thrombocytopenia, and anticoagulant medication effects can contribute to hematochezia and should be evaluated in the overall differential diagnosis.

Epidemiology and Risk Factors

Rectal bleeding is a prevalent issue, with community-based studies reporting lifetime prevalence rates ranging from 13% to 34%. While some studies suggest gender variations in incidence across age groups, the overall prevalence highlights the clinical significance of hematochezia. Notably, a substantial proportion of individuals with rectal bleeding, particularly older adults, do not seek medical attention, often underestimating the potential seriousness of the symptom. Risk factors for hematochezia are broadly related to the underlying etiologies, including age (increased risk of malignancy and diverticular disease), lifestyle factors (diet low in fiber contributing to hemorrhoids and fissures), and medical history (prior GI conditions, medication use).

History and Physical Examination: Guiding the Differential Diagnosis

A detailed history and thorough physical examination are paramount in the initial assessment of hematochezia, guiding the differential diagnosis and subsequent management.

History Taking

Crucial historical elements include:

Bleeding Characteristics: Onset, duration, frequency, volume, and presence of clots. Differentiating between bright red (fresh) and maroon or tarry (older) blood is essential for localizing the bleeding source.
Associated Symptoms: Abdominal pain, weight loss, changes in bowel habits, and prior abdominal or pelvic surgeries or radiation.
Risk Factors: Trauma, sexual history (relevant for infectious etiologies), fever, discharge, or rashes.
Comorbidities and Medications: Emphasis on bleeding disorders and medications such as NSAIDs, anticoagulants, and antiplatelet agents.

Specific historical clues can narrow the differential: Anal pain with defecation suggests anal fissures, while changes in bowel habits and weight loss in older patients raise suspicion for malignancy. Symptoms of hemorrhoids might include painless bleeding, anal protrusions, swelling, discomfort, mucous discharge, pruritus, and incomplete evacuation.

Physical Examination

The physical exam should begin with hemodynamic assessment, noting vital signs for signs of instability (hypotension, tachycardia, tachypnea). A focused abdominal exam assesses for pain, masses, distention, and signs of liver disease (portal hypertension and rectal varices). Perineal inspection in the left lateral decubitus position allows for visualization of external hemorrhoids, fissures, prolapse, and masses.

A digital rectal exam (DRE) is a critical component, unless contraindicated (e.g., immunocompromised patients at high risk of infection), to assess for masses, internal hemorrhoids, and obtain stool for fecal occult blood testing (FOBT). However, in cases of suspected acute anal fissures, gentle inspection may suffice to avoid exacerbating pain.

Diagnostic Evaluation: Refining the Differential Diagnosis

The diagnostic approach to hematochezia is guided by the clinical presentation and risk stratification, aiming to confirm the etiology and exclude serious conditions.

Initial Investigations

Complete Blood Count (CBC): Assesses the severity of bleeding and guides management, particularly in acute bleeds.
Coagulation Studies (INR, PTT): Evaluates for underlying bleeding disorders, especially in patients with relevant history or risk factors.
Cross-match: Considered in significant bleeding cases for potential blood transfusion to maintain hemoglobin levels.
STI Testing: In patients engaging in anal receptive intercourse, testing for gonorrhea and chlamydia is indicated.

Endoscopic Procedures

Endoscopy is the gold standard for evaluating hematochezia, especially in individuals over 40 or those with alarm symptoms.

Anoscopy and Rigid Proctosigmoidoscopy: Useful for distal source evaluation, visualizing internal hemorrhoids, proctitis, rectal ulcers, and distal malignancies.
Colonoscopy: Essential for evaluating the entire colon when proximal lower GI pathology is suspected. Colonoscopy allows for direct visualization, biopsy, and therapeutic intervention (e.g., polypectomy, hemostasis).

Advanced Imaging

CT Angiography: May be utilized in cases of massive lower GI bleeding or when endoscopy is contraindicated due to patient instability. CT angiography can identify the bleeding vessel and guide further management, such as angiography with embolization.
Tagged Red Blood Cell Scintigraphy: Highly sensitive for localizing bleeding sites in cases of recurrent or obscure rectal bleeding.

Differential Diagnosis of Hematochezia: A Structured Approach

The differential diagnosis of hematochezia is broad, requiring a systematic approach to narrow down possibilities based on clinical findings and investigations.

1. Anorectal Causes:

Hemorrhoids: Most common cause, typically painless bleeding. Differentiated by physical exam (visual inspection, DRE, anoscopy).
Anal Fissures: Painful bleeding with defecation. Diagnosis primarily clinical, confirmed by visual inspection.
Rectal Proctitis: Inflammation of the rectal mucosa, often due to IBD, infection, or radiation. Endoscopy with biopsy is diagnostic.
Rectal Cancer: Less frequent but serious. Colonoscopy with biopsy is crucial for diagnosis and exclusion.
Rectal Varices: Associated with portal hypertension. Endoscopy can identify varices.

2. Colonic Causes:

Diverticular Bleeding: Often painless, potentially massive bleeding. Colonoscopy is diagnostic and therapeutic.
Colonic Angiodysplasia: Dilated submucosal vessels, more common in older adults. Colonoscopy with angiography if needed for diagnosis and treatment.
Colonic Adenomas and Polyps: Can bleed, especially larger lesions. Colonoscopy with polypectomy is diagnostic and therapeutic.
Inflammatory Bowel Disease (IBD): Ulcerative colitis and Crohn’s disease. Colonoscopy with biopsy is essential for diagnosis and assessment of disease extent.
Infectious Colitis: Bacterial, viral, or parasitic infections. Stool studies and colonoscopy may be needed.
Ischemic Colitis: Reduced blood flow to the colon, more common in elderly and those with vascular disease. Colonoscopy may show characteristic findings.

3. Proximal Lower GI Causes (Less Common for Hematochezia):

Small Bowel Tumors: Rare but possible. Capsule endoscopy or enteroscopy might be needed for evaluation.
Meckel’s Diverticulum: Congenital anomaly, can bleed. Technetium-99m pertechnetate scan may be helpful in children.

4. Upper GI Causes Presenting as Hematochezia (Massive Bleeding):

Mallory-Weiss Tear: Mucosal tear at the gastroesophageal junction, often after vomiting. Upper endoscopy is diagnostic.
Esophageal Varices: Dilated esophageal veins due to portal hypertension. Upper endoscopy is diagnostic and therapeutic.
Peptic Ulcer Disease: Gastric or duodenal ulcers. Upper endoscopy is diagnostic and therapeutic.
Gastroduodenal Artery Perforation: Severe bleeding. CT angiography or endoscopy to locate and treat.

5. Systemic Causes:

Coagulopathies: Hemophilia, von Willebrand disease, thrombocytopenia, vitamin K deficiency. Coagulation studies are diagnostic.
Medication-Induced Bleeding: Anticoagulants, antiplatelet agents, NSAIDs. Medication history is crucial.

Management Strategies

Management of hematochezia is tailored to the underlying cause and bleeding severity. Acute, severe bleeding requires immediate hemodynamic stabilization.

Acute Management

Hemodynamic Resuscitation: IV fluids, vasopressors as needed.
Endoscopic Hemostasis: Cauterization, ligation, injection therapy (epinephrine, sclerosing agents) during endoscopy.
Angiographic Embolization: For persistent arterial bleeding, particularly in diverticular hemorrhage or angiodysplasia.

Specific Etiology-Based Treatments

Hemorrhoids: Conservative measures (fiber, fluids, sitz baths, topical agents), office-based procedures (rubber band ligation, infrared coagulation, sclerotherapy), surgical hemorrhoidectomy for refractory cases.
Anal Fissures: Conservative treatment (stool softeners, topical nitroglycerin, sitz baths), surgical sphincterotomy for chronic fissures.
Diverticular Bleeding: Endoscopic hemostasis, segmental colectomy for recurrent severe bleeding.
Colon Cancer: Surgical resection, adjuvant chemotherapy and radiotherapy based on staging.
Inflammatory Bowel Disease: Medical management with anti-inflammatory drugs, immunomodulators, biologics; surgery in select cases.
Infectious Colitis: Antimicrobial therapy targeting the specific pathogen.

Prognosis and Complications

The prognosis for hematochezia is highly dependent on the underlying cause. Most cases are benign and self-limiting. However, serious conditions like colorectal cancer or massive bleeding require prompt and aggressive management. Potential complications include:

Thrombosed External Hemorrhoids: Painful.
Chronic Anal Fissures: Persistent pain and bleeding.
Metastasis from Colorectal Cancer: If diagnosis and treatment are delayed.
Anemia: From chronic or significant blood loss.

Deterrence and Patient Education

Patient education is crucial to encourage timely medical consultation for rectal bleeding, especially in older individuals due to increased malignancy risk. Patients should be advised to seek immediate medical attention for hematochezia associated with hematemesis or signs of hemodynamic instability.

Interprofessional Approach

Optimal management of hematochezia necessitates a collaborative interprofessional team including primary care physicians, gastroenterologists, colorectal surgeons, and radiologists. Effective communication and coordinated care are essential for accurate diagnosis, timely intervention, and improved patient outcomes.

Conclusion

Hematochezia is a common and often alarming symptom that requires a systematic approach to differential diagnosis. A comprehensive understanding of the diverse etiologies, coupled with a thorough history, physical examination, and appropriate investigations, is essential for effective management. By considering the broad differential diagnosis of hematochezia, clinicians can ensure timely and accurate diagnosis, leading to optimal patient care and outcomes.