Clinical Analysis: 31-Year-Old Male with Bloody Diarrhea (10-15 stools/day) + Vomiting for 15 Days

Immediate Impression

Top Differential Diagnoses

1. Acute Severe Ulcerative Colitis (ASUC) - Most Important to Rule Out

• ≥6 bloody stools per day (this patient has 10-15)
• Plus at least one systemic marker:
  • Pulse >90 bpm
  • Temperature >37.8°C
  • Hemoglobin <10.5 g/dL
  • ESR >30 mm/h

"Acute severe ulcerative colitis (ASUC) is a medical emergency and requires prompt treatment in hospital, to avoid complications of spontaneous perforation and toxic megacolon." - Yamada's Textbook of Gastroenterology, 7th Ed.

2. Amoebic Dysentery (Entamoeba histolytica)

• Fever, tenesmus, abdominal pain
• Watery stools with blood and mucus
• Vomiting can occur

• Stool microscopy: mobile trophozoites containing ingested RBCs (pathognomonic)
• Nonpathogenic ameba cysts do NOT contain host RBCs
• Immune assay of stool can differentiate pathogenic from non-pathogenic species
• Serology may be negative in the first month of infection

"E. histolytica causes an invasive or inflammatory diarrhea. Patients complain of fever, tenesmus, abdominal pain, and watery stool containing blood and mucus." - Rosen's Emergency Medicine, 9th Ed.

3. Infectious Bacterial Dysentery

• Shigella - most likely bacterial cause of high-volume bloody diarrhea with systemic features; can cause >10 stools/day; self-limiting in 5-7 days but may persist longer
• Campylobacter jejuni - bloody diarrhea, fever, vomiting, can last 7-10 days
• Salmonella (non-typhoidal) - bloody diarrhea, high fever, vomiting
• EHEC (E. coli O157:H7) - bloody diarrhea without high fever; watch for HUS (hemolytic uremic syndrome) - especially if oliguria develops

4. Crohn's Disease (First Presentation)

• Transmural inflammation affecting any part of the GI tract
• Can present with diarrhea (with or without blood), weight loss, abdominal pain, fever
• Less likely as a first-time presentation with this acuity, but must be excluded
• Rectal involvement distinguishes UC from Crohn's (Crohn's may spare the rectum)

5. Pseudomembranous Colitis (C. difficile)

• Especially if the patient had recent antibiotic use
• Can cause severe bloody diarrhea with systemic toxicity
• Must send stool C. diff toxin assay

Workup to Order (Urgency-Based)

Immediate (On Admission)

Secondary

Management Principles

If ASUC Confirmed:

1. Admit to hospital - this is a medical emergency
2. IV fluid resuscitation - correct dehydration and electrolytes
3. NPO or restricted diet - bowel rest
4. IV corticosteroids - methylprednisolone 40-60 mg/day or hydrocortisone 200-300 mg/day
5. Monitor for toxic megacolon - daily abdominal X-ray, vitals
6. If steroids fail at 3-5 days - rescue therapy with:
   • Infliximab (5 mg/kg), OR
   • Cyclosporine (2-4 mg/kg IV)
7. Surgical consultation early - subtotal colectomy if deteriorating

If Amoebic Dysentery Confirmed:

• Metronidazole 750 mg every 8 hours (10 days) - drug of choice
• Followed by a luminal amebicide to eliminate intraluminal cysts:
  • Iodoquinol 650 mg TID x 20 days, OR
  • Paromomycin 500 mg TID x 7 days

If Bacterial Dysentery:

• Supportive care, hydration
• Ciprofloxacin or azithromycin for Shigella/Salmonella if severe
• Avoid antispasmodics (risk of ileus/megacolon)

Red Flags Requiring Urgent Surgical Review

• Abdominal rigidity or peritoneal signs
• Toxic megacolon (colon >6 cm on X-ray)
• Free air on imaging (perforation)
• Rapid clinical deterioration despite IV steroids
• Septic shock (hypotension, high fever, altered consciousness)

Summary

Updated Analysis: Pustular/Scaling Rash on Lower Limbs PRECEDING Bloody Diarrhea

Leading Diagnoses

1. Inflammatory Bowel Disease (UC or Crohn's) with Extraintestinal Skin Manifestations

• Starts as pustules or papules on the lower limbs/shins, then evolves into deep ulcerating lesions with a purulent, necrotic center and raised dusky-purple border
• Occurs in ~2% of UC patients
• Can appear before or independently of bowel disease activity
• The pustular early stage of PG is easily confused with infection - this is critical to recognize as misdiagnosis leads to harmful debridement

• Bilateral, raised, erythematous, tender subcutaneous nodules on the anterior tibial surface (shins)
• More common than PG (~15% of IBD patients)
• Strongly correlates with active bowel disease and typically precedes flares
• More nodular/tender than pustular, but early lesions can look erythematous and scaling

"Peripheral and axial arthritis and skin lesions including erythema nodosum and pyoderma gangrenosum are the most common extraintestinal complications." - Tintinalli's Emergency Medicine

Fig: Dermatological EIMs of UC - (a) Pyoderma gangrenosum with pustular/necrotic center on shin, (b) Peristomal PG, (c) Erythema nodosum on anterior tibia - Yamada's Gastroenterology, 7th Ed.

2. Reactive Arthritis (Reiter's Syndrome) - with Keratoderma Blennorrhagica

• Triggered by enteric infections (Shigella, Salmonella, Campylobacter, Yersinia)
• Skin lesions can appear in the prodromal phase
• Young adult male is the classic demographic (HLA-B27 association)
• However, in reactive arthritis the diarrhea is typically the trigger (comes first), not the result - so this sequence makes UC with PG more likely

3. Psoriasis with Gut Involvement / IBD-Associated Psoriasis

• Psoriasis and IBD share common genetic pathways (TNF-alpha, IL-23/IL-17 axis)
• Pustular psoriasis on lower limbs can precede or coexist with IBD
• UC patients have ~2x higher risk of psoriasis
• If scaling/silvery plaques are present on shins, this fits psoriasis

Revised Differential Priority

How the Skin Changes the Workup

Critical Point: Skin Lesion Preceding GI = IBD Until Proven Otherwise