What are the differential diagnoses for a patient with abdominal pain for the last month accompanied by three episodes of hematochezia (blood in stool)?

Differential Diagnoses for Chronic Abdominal Pain with Hematochezia

In a patient with one month of abdominal pain and three episodes of hematochezia, the differential diagnosis must prioritize inflammatory bowel disease, colorectal malignancy, diverticular disease, and infectious colitis, as hematochezia with chronic abdominal pain fundamentally indicates mucosal pathology requiring urgent colonoscopy. 1, 2, 3

Critical Diagnostic Framework

Primary Differential Diagnoses

Inflammatory/Infectious Causes:

• Inflammatory bowel disease (IBD) - Crohn's disease or ulcerative colitis presenting with rectal bleeding, abdominal pain, and diarrhea 1, 3
• Infectious colitis - Including E. coli O157:H7, which can cause severe colitis with hematochezia and abdominal pain 4
• Diverticulitis - Particularly in older adults, can present with left lower quadrant pain and bleeding 5, 3

Neoplastic Causes:

• Colorectal malignancy - Carries a 2.4-11% risk in patients presenting with rectal bleeding and represents 60% of large bowel obstructions 2, 5
• Colonic polyps - Can cause intermittent bleeding with abdominal discomfort 2

Vascular Causes:

• Mesenteric ischemia - Must be considered when pain is out of proportion to physical findings, though typically presents more acutely 1, 5
• Angiodysplasia - Most common in cecum and ascending colon, can cause chronic intermittent bleeding 3

Other Structural Causes:

• Diverticular bleeding - Most common cause of lower GI bleeding in adults, though typically painless 3
• Radiation proctitis - If history of pelvic radiation 9 months to 4 years prior 1
• Anorectal varices - In patients with portal hypertension, up to 15% may have concurrent upper GI bleeding 2, 3

Red Flag Features Requiring Immediate Evaluation

The presence of hematochezia with chronic abdominal pain should trigger systematic evaluation for GI bleeding sources before considering other diagnoses. 2

• Hemodynamic instability (tachycardia, hypotension) suggests significant bleeding or sepsis 5, 3
• Peritoneal signs (rigid abdomen, rebound tenderness) indicate perforation or ischemia 5
• Pain out of proportion to examination strongly suggests mesenteric ischemia 5
• Fever with severe pain suggests infection, abscess, or perforation 5
• Weight loss raises concern for malignancy or IBD 1

Diagnostic Algorithm

Initial Assessment (First 24 Hours)

Hemodynamic stabilization takes absolute priority before diagnostic procedures. 3

1. Immediate hemodynamic assessment including vital signs, complete blood count, coagulation parameters, blood type/crossmatch 3
2. Establish two large-bore IV access for fluid resuscitation if severe bleeding 3
3. Laboratory evaluation: CBC, electrolytes, BUN, creatinine, liver function tests, coagulation studies, C-reactive protein 3, 6
4. Pregnancy test in all women of childbearing age 3
5. Digital rectal examination to confirm blood presence and exclude anorectal pathology 1, 3

Focused History Elements

Critical historical features that differentiate diagnoses: 1, 3

• Timing and frequency of bleeding episodes
• Associated diarrhea suggests IBD or infectious colitis 1, 4
• NSAID use increases risk of ulceration and bleeding 1
• History of pelvic radiation points to radiation proctitis 1
• Chronic constipation raises concern for diverticular disease 5
• Portal hypertension/liver disease suggests anorectal varices 2, 3

Definitive Diagnostic Approach

Urgent colonoscopy within 24 hours is the first-line diagnostic approach after hemodynamic stabilization. 3

Primary diagnostic pathway:

1. Colonoscopy with thorough bowel preparation - First-line for chronic intermittent bleeding, allows both diagnosis and therapeutic intervention 1, 3
2. Upper endoscopy if no lower GI source identified, as 10-15% of patients with hematochezia have upper GI bleeding 2, 3
3. CT abdomen/pelvis with IV contrast if colonoscopy inconclusive or to evaluate for complications (abscess, perforation, obstruction) 5, 6

If initial colonoscopy is inconclusive: 3

• Repeat colonoscopy with improved bowel preparation
• Consider radionuclide imaging with 99Tc-labeled red blood cells (detects bleeding at 0.1-0.5 mL/min)
• CT angiography for hemodynamically unstable patients or suspected active bleeding
• Angiography only after positive scintigraphy (requires bleeding rate ≥1 mL/min)

Age-Specific Considerations

In patients over 70 years: 1

• Diverticular disease and angiodysplasia are most likely causes of lower GI bleeding
• Colorectal malignancy risk significantly elevated
• Atypical presentations are common, requiring thorough evaluation even with normal laboratory values 5

In younger patients: 1, 4

• IBD more likely, particularly with chronic diarrhea and systemic symptoms
• Infectious colitis should be strongly considered with acute-on-chronic presentation

Critical Pitfalls to Avoid

Even if hemorrhoids are present on examination, patients may have more proximal bleeding sources or colorectal cancer requiring full colonoscopy. 2

• Delaying resuscitation to perform diagnostic procedures - stabilization always takes priority 3
• Inadequate bowel preparation leading to poor colonoscopic visualization and missed diagnoses 3
• Dismissing atypical presentations in elderly patients can lead to missed serious pathology 5
• Over-relying on normal laboratory values early in disease course 5
• Failing to consider upper GI sources in patients with severe hematochezia and hemodynamic instability 3
• Premature resort to surgery without attempting to localize bleeding through endoscopic/radiological modalities first 3

Management Principles

Correct any coagulopathy (INR >1.5) with fresh frozen plasma or thrombocytopenia (<50,000/µL) with platelets before invasive procedures. 1, 3

• Maintain hemoglobin >7 g/dL and mean arterial pressure >65 mmHg while avoiding fluid overload 3
• Consider discontinuing antiplatelet agents temporarily during acute bleeding 3
• Endoscopic hemostasis is preferred first-line treatment for accessible bleeding sources 3
• Approximately 75% of diverticular bleeding episodes stop spontaneously 3