What is the diagnosis and treatment for a 23-year-old female student with a 3-month history of bright red blood and mucus in stool, abdominal pain, cramping, diarrhea, and a history of recurrent mouth sores, sensitive stomach, and elevated liver enzymes, who has tried eliminating potential triggers without improvement?

Inflammatory Bowel Disease (Likely Ulcerative Colitis or Crohn's Disease)

This 23-year-old female most likely has inflammatory bowel disease (IBD), specifically ulcerative colitis or Crohn's disease, and requires urgent colonoscopy with biopsies, comprehensive laboratory evaluation including inflammatory markers and stool studies, and initiation of mesalamine therapy if ulcerative colitis is confirmed.

Rationale for IBD as Primary Diagnosis

The clinical presentation strongly suggests IBD rather than irritable bowel syndrome or functional disorders:

• Three months of progressive bloody diarrhea with mucus occurring with almost every bowel movement, now progressing to only blood and mucus without stool, indicates active mucosal inflammation 1
• Recurrent oral ulcers (aphthous ulceration) are a classic extraintestinal manifestation of Crohn's disease 1
• Young age (23 years) with new-onset symptoms warrants imaging of the colon to exclude serious organic disease 1
• Bright red blood per rectum with abdominal pain and cramping suggests colonic inflammation rather than upper GI bleeding 2
• Progressive worsening despite dietary modifications (eliminating gluten, dairy, potential triggers) argues against functional dyspepsia or IBS 1
• Abdominal tenderness on examination, particularly in the descending colon area, indicates organic pathology 1

Immediate Diagnostic Workup Required

Urgent Endoscopic Evaluation

• Full colonoscopy with multiple biopsies is mandatory to establish the diagnosis, assess disease extent, and exclude microscopic colitis or other seronegative enteropathies 1
• Colonoscopy should be performed after excluding upper GI bleeding source if hemodynamic instability develops 2

Comprehensive Laboratory Panel

• Complete blood count to assess for anemia from chronic blood loss and leukocytosis suggesting active inflammation 3
• Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are mandatory for assessing inflammatory burden 1, 4
• Comprehensive metabolic panel including liver function tests (given history of elevated liver enzymes), albumin, and electrolytes 3
• Fecal calprotectin to differentiate IBD from functional disorders 4, 3
• Stool culture for bacterial pathogens, C. difficile toxin, and ova/parasites to exclude infectious colitis 1, 4
• Serum B12, red cell folate, ferritin given chronic diarrhea and potential malabsorption 1
• Thyroid function tests and antiendomysial antibodies to exclude celiac disease as a seronegative enteropathy 1

Imaging Considerations

• CT abdomen/pelvis should be obtained if there are signs of complications (perforation, abscess, obstruction) or if the patient develops peritoneal signs 4, 3

Treatment Algorithm Based on Diagnosis

If Ulcerative Colitis is Confirmed

Initiate mesalamine therapy immediately as first-line treatment:

• Mesalamine delayed-release tablets 2.4-4.8 g once daily for induction of remission in mildly to moderately active ulcerative colitis 5
• After 8 weeks, reduce to 2.4 g once daily for maintenance 5
• Take with food and ensure adequate hydration to minimize risk of nephrolithiasis 5
• Monitor renal function periodically as mesalamine can cause renal impairment including interstitial nephritis 5
• Discontinue immediately if acute intolerance syndrome develops (worsening cramping, abdominal pain, bloody diarrhea, fever, headache, rash), which occurs in 3% of patients and can mimic disease flare 5

If Crohn's Disease is Confirmed

• Immunosuppression with corticosteroids or biologic agents is typically required for moderate to severe Crohn's disease with bloody diarrhea, fever, and weight loss 1
• Gastroenterology consultation is essential for determining optimal therapy based on disease location and severity 1

If Seronegative Enteropathy is Identified

Multiple conditions can present with villous atrophy and negative celiac serology 1:

• Medication-induced enteropathy: Review all supplements (iron, magnesium, zinc, L-theanine, B12, adrenal complex) and any prescription medications for potential causative agents 1
• Common variable immunodeficiency (CVID): Check total IgG, IgA, and IgM levels given recurrent infections history 1
• Autoimmune enteropathy: Consider if intractable diarrhea persists despite treatment 1
• Giardiasis: Obtain stool PCR and specific immunoassay if parasitic infection suspected 1

Critical Clinical Pitfalls to Avoid

Do Not Assume IBS Without Excluding Organic Disease

• IBS guidelines explicitly state that bloody diarrhea is an alarm feature requiring investigation and cannot be diagnosed on symptoms alone when inflammatory markers or structural disease may be present 1
• The British Society of Gastroenterology notes that symptom criteria do not reliably distinguish IBS from inflammatory bowel disease 1
• Progressive symptoms in any age group should prompt re-evaluation for imaging and endoscopy 1

Do Not Delay Endoscopy

• Younger patients with family history of colon cancer or progressive symptoms warrant colonoscopy regardless of age 1
• The combination of bloody diarrhea, weight concerns, oral ulcers, and progressive symptoms over 3 months mandates definitive diagnosis via colonoscopy 1

Monitor for Complications

• Severe diarrhea with bright red blood can lead to significant anemia and volume depletion requiring aggressive fluid resuscitation 3
• Elevated lactate, metabolic acidosis, or marked leukocytosis would suggest bowel ischemia or perforation requiring urgent surgical consultation 3
• The history of elevated liver enzymes requires monitoring as mesalamine can cause hepatic failure in patients with pre-existing liver disease 5

Address Nutritional Deficiencies

• Chronic bloody diarrhea for 3 months likely has caused iron deficiency anemia requiring supplementation 1
• Malabsorption from active inflammation may require B12, folate, and fat-soluble vitamin replacement 1

Immediate Management Pending Diagnosis

• Fluid resuscitation with isotonic crystalloids if signs of dehydration or hemodynamic compromise develop 3
• Avoid antimotility agents (loperamide, codeine) until infectious causes are excluded, as they can precipitate toxic megacolon in IBD 1, 3
• Discontinue NSAIDs if being used, as they can exacerbate IBD 1
• Ensure adequate oral hydration (at least 2-3 liters daily) to prevent volume depletion and reduce risk of nephrolithiasis if mesalamine is started 5