What is the most likely diagnosis for a patient with chronic diarrhea, intermittent lower abdominal pain, and occasional rectal bleeding, with a history of spondyloarthropathy and anemia?

Ulcerative Colitis is the Correct Diagnosis

The most likely diagnosis is ulcerative colitis (Option 1), based on the constellation of chronic bloody diarrhea for 4 weeks, bilateral lower abdominal pain, severe anemia requiring transfusion, and the critical association with pre-existing spondyloarthropathy. 1

Why Ulcerative Colitis is the Answer

Classic Symptom Complex

• The triad of chronic bloody diarrhea, bilateral lower abdominal pain, and progressive anemia is pathognomonic for ulcerative colitis. 1, 2
• Bloody diarrhea with mucus, rectal urgency, and abdominal pain relieved by defecation are the hallmark presenting features of UC. 2, 3
• The 4-week duration meets the definition of chronic diarrhea (≥3 loose stools per day for more than 4 weeks), distinguishing this from infectious causes. 4

Critical Extraintestinal Manifestation

• Approximately 20% of UC patients develop peripheral or axial spondyloarthropathy, making this the second most common extraintestinal manifestation. 1
• The pre-existing spondyloarthropathy is not coincidental—patients with axial spondyloarthropathy have significantly higher incidence of inflammatory bowel disease compared to the general population. 1
• This association is so strong that it essentially excludes hemorrhoids and makes infectious diarrhea highly unlikely. 1

Severe Anemia Indicating Chronic Blood Loss

• The severe anemia (hemoglobin requiring transfusion) with drops of blood in stool indicates chronic gastrointestinal blood loss from mucosal inflammation, a defining feature of UC. 1, 4
• This degree of anemia would not occur with simple hemorrhoids or short-term infectious diarrhea. 4

Why Other Options Are Incorrect

Infectious Diarrhea (Option 3) - Unlikely

• Infectious diarrhea rarely persists for 4 weeks without fever, and the chronic progressive nature with worsening anemia suggests chronic inflammatory disease rather than infection. 1
• The absence of fever and the 4-week duration make bacterial or viral gastroenteritis extremely unlikely. 4, 2
• While C. difficile must still be excluded before confirming IBD diagnosis, the clinical picture strongly favors UC. 1, 5

Hemorrhoids (Option 4) - Excluded

• Hemorrhoids do not cause diarrhea, bilateral lower abdominal pain, or severe anemia requiring transfusion. 1
• Hemorrhoids do not explain the association with spondyloarthropathy. 1
• The symptom complex is completely inconsistent with hemorrhoidal bleeding alone. 2

Peptic Ulcer Disease (Option 2, if this was the second option) - Wrong Location

• Peptic ulcer disease causes epigastric pain, not bilateral lower abdominal pain. 1
• It does not explain the association with axial spondyloarthropathy. 1
• The location and character of pain are incompatible with peptic ulcer disease. 2

Critical NSAID Consideration

• The patient's ibuprofen use for spondyloarthropathy is highly relevant—NSAIDs can exacerbate inflammatory bowel disease and may have contributed to this presentation. 1
• NSAIDs should be discontinued immediately as they worsen UC. 1

Next Steps for Definitive Diagnosis

• Colonoscopy with biopsies from multiple sites is the gold standard and only definitive way to diagnose ulcerative colitis. 1, 2
• Stool culture and C. difficile toxin testing must be obtained before confirming IBD diagnosis. 1, 5
• Fecal calprotectin has 93-95% sensitivity for differentiating IBD from non-IBD diagnoses, with values >200-250 μg/g strongly suggesting IBD. 5
• Expected colonoscopy findings: continuous colonic inflammation with erythema, loss of vascular pattern, granularity, friability, and ulcerations starting from the rectum. 2, 6

Management Implications

• The patient received appropriate initial management with packed red blood cell transfusion for severe anemia. 4
• Intravenous corticosteroids are first-line for severe UC, with consideration of TNF-alpha antibodies (infliximab or adalimumab) if steroid-refractory. 1
• The previous use of etanercept for spondyloarthropathy is relevant because etanercept lacks efficacy for UC, while other TNF inhibitors (infliximab, adalimumab) effectively treat both conditions. 1