How should I manage a patient with ultrasound‑confirmed colitis who has had three days of watery diarrhea, one day of bloody stool, is in hypovolemic shock with impaired renal function, mild transaminitis and elevated C‑reactive protein?

Management of Ultrasound-Confirmed Colitis with Hypovolemic Shock

This patient requires immediate resuscitation, empiric broad-spectrum antibiotics, urgent infectious workup, and surgical consultation—the combination of bloody diarrhea, shock, renal impairment, and elevated inflammatory markers indicates severe invasive bacterial colitis or fulminant Clostridioides difficile infection until proven otherwise. 1, 2

Immediate Resuscitation (First 1–2 Hours)

• Administer IV boluses of 20 mL/kg Ringer's lactate or normal saline and repeat until perfusion normalizes (mean arterial pressure >65 mmHg, urine output >0.5 mL/kg/hr, lactate clearance). 1
• Insert urinary catheter to monitor hourly urine output and assess response to fluid resuscitation. 3
• Obtain blood cultures immediately before starting antibiotics, as bacteremia occurs in invasive bacterial colitis and severe C. difficile infection. 1, 2
• Draw complete blood count with differential, comprehensive metabolic panel, lactate, coagulation studies, and type-and-screen—neutrophil predominance supports bacterial/inflammatory causes; lymphopenia with monocytosis suggests Salmonella species. 1, 2
• Initiate thromboprophylaxis with low-molecular-weight heparin once hemodynamically stable; bloody stool is not a contraindication. 3, 4

Urgent Diagnostic Workup (Within 2–4 Hours)

• Send stool for culture (Salmonella, Shigella, Campylobacter, enterohemorrhagic E. coli) and C. difficile nucleic-acid amplification test (NAAT) before antibiotics—cultures are positive in ≈31% of patients with this presentation. 1
• Measure fecal calprotectin or lactoferrin if etiology remains unclear after initial testing; values >150–250 µg/g indicate significant mucosal inflammation and warrant endoscopy. 1
• Perform CT abdomen/pelvis with IV contrast to assess for toxic megacolon (colonic diameter >6 cm), perforation, abscess, or severe colonic wall thickening (>4 mm with peri-colonic stranding suggests severe disease). 3
• Arrange urgent surgical consultation at admission—do not delay until clinical deterioration occurs. 3

Empiric Antibiotic Therapy (Start Within 1 Hour of Presentation)

Initiate empiric antibiotics immediately after obtaining cultures in this critically ill patient with dysentery (fever + bloody stool) and shock. 1, 2

• Ciprofloxacin 400 mg IV every 12 hours PLUS metronidazole 500 mg IV every 8 hours to cover invasive bacterial pathogens (Salmonella, Shigella, Campylobacter) and C. difficile simultaneously. 3, 4, 2
• Add vancomycin 125 mg orally (via nasogastric tube if unable to swallow) every 6 hours if C. difficile is strongly suspected (recent antibiotic exposure, healthcare contact, or age >65 years)—IV metronidazole alone is insufficient for severe C. difficile infection. 3, 4
• If patient deteriorates despite vancomycin + metronidazone, escalate to vancomycin 500 mg orally every 6 hours PLUS vancomycin 500 mg per rectum every 6 hours (as retention enema in 100 mL saline) for fulminant C. difficile colitis. 3

Critical Monitoring (Every 4–6 Hours for First 24–48 Hours)

• Track stool frequency, character, and blood content; vital signs; urine output; and mental status—worsening fever, abdominal pain, or altered sensorium signals impending perforation or toxic megacolon. 3, 2
• Repeat complete blood count, CRP, creatinine, and lactate every 12–24 hours—rising lactate, worsening leukocytosis (or new leukopenia), or thrombocytopenia suggest progression to septic shock or hemolytic uremic syndrome (if STEC). 3, 1
• Monitor for colonic dilation on daily abdominal radiographs—colon diameter >6 cm defines toxic megacolon and mandates surgical evaluation. 3

Indications for Urgent Surgery (Do Not Delay)

• Perforation, massive hemorrhage requiring >4 units packed red blood cells in 24 hours, or toxic megacolon without improvement after 24–48 hours of maximal medical therapy mandate emergency subtotal colectomy with end-ileostomy. 3
• Progressive clinical deterioration (worsening shock, rising lactate, new organ dysfunction) despite 24–48 hours of antibiotics and resuscitation indicates failure of medical therapy—colectomy should not be delayed. 3
• Hartmann's procedure or subtotal colectomy with ileostomy is the procedure of choice in the emergency setting; avoid primary anastomosis in critically ill patients. 3

Endoscopic Evaluation (Once Hemodynamically Stable)

• Perform unprepared flexible sigmoidoscopy (without full bowel preparation) within 24–48 hours if patient stabilizes—this confirms colitis severity, excludes cytomegalovirus (CMV) colitis in immunocompromised patients, and identifies pseudomembranes (C. difficile). 3
• Avoid full colonoscopy in the acute setting—risk of perforation is significantly elevated in severe colitis. 3

Common Pitfalls to Avoid

• Do not withhold empiric antibiotics while awaiting stool culture results in a patient with shock and bloody diarrhea—mortality increases with delayed treatment. 1, 2
• Do not use anti-diarrheal agents (loperamide, diphenoxylate)—these precipitate toxic megacolon in severe colitis. 3, 4
• Do not delay surgical consultation until medical therapy fails—early surgical involvement improves outcomes in fulminant colitis. 3
• Do not assume inflammatory bowel disease (IBD) without excluding infection first—infectious colitis mimics IBD flares, and corticosteroids worsen outcomes in unrecognized infection. 4

Special Considerations

• If patient has known IBD, still obtain stool cultures and C. difficile testing—superimposed infection occurs in 5–10% of IBD flares and requires antibiotics before immunosuppression. 4
• If immunocompromised (HIV, chemotherapy, transplant), expand stool testing to include Cryptosporidium, Cyclospora, Cystoisospora, microsporidia, Mycobacterium avium complex, and CMV—these opportunistic pathogens cause severe colitis in this population. 2
• If travel history to endemic areas (South Asia, Africa, Latin America), consider enteric fever (Salmonella Typhi/Paratyphi)—sustained fever with relative bradycardia and monocytosis are clues; blood cultures are more sensitive than stool cultures. 2