What is the initial treatment approach for a patient with infective colitis, possibly complicated by underlying inflammatory bowel disease (IBD)?

Treatment of Infective Colitis

For true infectious colitis without underlying IBD, antimicrobial therapy targeting the specific pathogen is the cornerstone of treatment, while antibiotics should NOT be routinely administered in IBD patients unless superinfection, intra-abdominal abscesses, or sepsis is present. 1

Initial Assessment and Stabilization

The first critical step is distinguishing infectious colitis from IBD, as management differs fundamentally:

• Infectious colitis typically presents with acute onset (within 1 week), early fever, and lacks histologic features of IBD such as basal plasmacytosis, crypt distortion, or epithelioid granulomas 2
• IBD patients more commonly have insidious onset (56%), late presentation (>1 week), and may have preceding mild bowel symptoms 2

Immediate supportive measures for all patients:

• Adequate intravenous fluid resuscitation with electrolyte correction (including potassium supplementation of at least 60 mmol/day to prevent toxic dilatation) 3, 4
• Low-molecular-weight heparin for thromboprophylaxis immediately, even in the presence of rectal bleeding 3, 4
• Correction of anemia and electrolyte abnormalities 1, 3

Essential diagnostic workup:

• Stool cultures for invasive bacterial pathogens (Shigella, Salmonella, Campylobacter) and Clostridium difficile toxin testing 1, 5
• For suspected Shiga toxin-producing E. coli (STEC), specifically test for E. coli O157:H7 and Shiga toxin directly in stool when only low-grade or no fever is present with acute dysentery 5
• Multiplex PCR followed by guided culture provides rapid diagnosis while preserving isolates for susceptibility testing 6
• Flexible sigmoidoscopy with biopsies to confirm diagnosis, assess severity, and exclude cytomegalovirus infection 4

Antimicrobial Therapy

For confirmed infectious colitis (non-IBD):

Pathogen-specific antimicrobial therapy should be initiated for all forms of infectious colitis EXCEPT STEC 5

• For empiric treatment of febrile dysenteric diarrhea (suspected Shigella, Salmonella, Campylobacter): azithromycin 1000 mg single dose in adults 5
• For C. difficile infection: oral vancomycin 125 mg four times daily for 10 days 7
• CRITICAL PITFALL: Do NOT treat STEC with antibiotics, as this may precipitate hemolytic uremic syndrome 5

For IBD patients with suspected superinfection:

Antibiotics are indicated ONLY in the presence of superinfection, intra-abdominal abscesses, or sepsis 1

• When indicated, use prompt antimicrobial therapy covering Gram-negative aerobic/facultative bacilli, Gram-positive streptococci, and obligate anaerobic bacilli (e.g., fluoroquinolones or third-generation cephalosporin plus metronidazole) 1
• Antimicrobial duration depends on clinical and biochemical response (serum CRP levels) 1
• C. difficile testing is mandatory in all IBD patients hospitalized with disease flare, as prevalence is high and outcomes are worse 8

Management of IBD Patients with Acute Severe Colitis

Medical management for hemodynamically stable patients:

Intravenous corticosteroids (hydrocortisone 100 mg four times daily OR methylprednisolone 40-60 mg daily) should be initiated immediately without waiting for stool culture results 4

• Assess response by day 3; maximum treatment duration is 7-10 days 4
• For non-responders: medical rescue therapy with infliximab combined with thiopurine OR ciclosporin in multidisciplinary consultation 1, 4
• Overall response rate to IV corticosteroids is 67%, with 33% requiring colectomy 4

Nutritional support:

• Preoperative nutritional support is mandatory in severely undernourished patients 1
• Total parenteral nutrition is reserved for patients unable to tolerate enteral nutrition, critically ill patients with shock, intestinal ischemia, high-output fistula, severe hemorrhage, or when emergency surgery is needed 1, 3

Surgical Indications

Emergency surgical exploration is mandatory for: 1, 3, 4

• Hemodynamically unstable patients
• Colonic perforation with generalized peritonitis
• Toxic megacolon complicated by perforation, massive bleeding, clinical deterioration, or signs of shock
• Failure to improve or deterioration within 48-72 hours of medical therapy

Subtotal colectomy with ileostomy is the surgical treatment of choice for acute severe ulcerative colitis with massive hemorrhage or medical treatment failure 1, 4

Critical Pitfalls to Avoid

• Never delay corticosteroid treatment in IBD patients while waiting for microbiology results 4
• Never delay surgery in critically ill patients with toxic megacolon—mortality increases significantly with perforation 1, 3, 4
• Never extend IV corticosteroids beyond 7-10 days without escalating to rescue therapy or surgery 4
• Never treat STEC with antibiotics 5
• Recognize that preoperative immunomodulators with anti-TNF-α agents and steroids increase risk of intra-abdominal sepsis in emergency surgery 1, 3
• IBD patients with C. difficile infection are younger, have less antibiotic exposure, and often acquire infection as outpatients—maintain high index of suspicion 8