How should I manage a patient presenting with fever, abdominal pain, and acute lower gastrointestinal bleeding?

Management of Fever, Abdominal Pain, and Lower Gastrointestinal Bleeding

Immediate Hemodynamic Assessment and Resuscitation

In a patient presenting with fever, abdominal pain, and acute lower GI bleeding, immediately calculate the shock index (heart rate ÷ systolic blood pressure); if >1, proceed directly to CT angiography followed by catheter-directed embolization within 60 minutes rather than colonoscopy or empiric antibiotics. 1, 2

Initial Resuscitation Protocol

• Place two large-bore intravenous catheters and initiate aggressive crystalloid resuscitation (normal saline or Ringer's lactate) to restore blood pressure and heart rate before any diagnostic procedure 2, 3
• Apply restrictive transfusion thresholds: hemoglobin trigger 70 g/L (target 70-90 g/L) for patients without cardiovascular disease, or 80 g/L (target ≥100 g/L) for those with cardiovascular disease 2, 3
• Correct coagulopathy immediately: transfuse fresh frozen plasma when INR >1.5 and platelets when count <50 × 10⁹/L 1, 2
• For patients on warfarin with unstable hemorrhage, reverse immediately with prothrombin complex concentrate plus vitamin K (<5 mg) rather than fresh frozen plasma 2, 3

Diagnostic Algorithm Based on Hemodynamic Status

Hemodynamically Unstable Patients (Shock Index >1)

CT angiography is the mandatory first diagnostic test—not colonoscopy—because it rapidly localizes bleeding without bowel preparation, detects bleeding rates as low as 0.3 mL/min with 94% sensitivity, and allows immediate treatment planning. 1, 2

• If CTA identifies a bleeding source, proceed to catheter angiography with embolization within 60 minutes; this achieves immediate hemostasis in 40-100% of cases 1, 2
• If CTA shows no lower GI source, perform urgent upper endoscopy because 10-15% of severe hematochezia originates from the upper GI tract, especially with hemodynamic instability 2, 3
• Colonoscopy is explicitly contraindicated when shock index >1 because it requires 4-6 L polyethylene glycol preparation over 3-4 hours, sedation that worsens shock, and does not address massive bleeding 1, 2

Hemodynamically Stable Patients (Shock Index ≤1)

• Perform digital rectal examination first to confirm blood presence and exclude anorectal pathology (accounts for ~16% of diagnoses) 2, 3
• Calculate the Oakland score (age, gender, prior LGIB admission, rectal exam findings, heart rate, systolic BP, hemoglobin):
  • Score ≤8: Discharge for urgent outpatient colonoscopy within 2 weeks (6% have underlying colorectal cancer) 2, 3
  • Score >8: Admit for inpatient colonoscopy on the next available list—not urgently within 24 hours, as urgent colonoscopy does not improve rebleeding, mortality, or length of stay 1, 2

Specific Considerations for Fever and Abdominal Pain

Inflammatory Bowel Disease Evaluation

The combination of fever, abdominal pain, and lower GI bleeding raises concern for acute severe ulcerative colitis or complicated Crohn's disease; evaluate all hemodynamically stable patients in a multidisciplinary approach with gastroenterology to decide on initial medical treatment versus surgery. 1

• In patients with known or suspected IBD presenting with massive colorectal hemorrhage and hemodynamic instability, subtotal colectomy with ileostomy is the surgical treatment of choice if embolization fails 1
• Perform surgical exploration immediately if radiological signs of pneumoperitoneum and free fluid are present in acutely unwell patients 1
• In toxic megacolon with perforation, massive bleeding, or clinical deterioration with shock, surgery is mandatory and should not be delayed 1
• If no clinical improvement occurs after 24-48 hours of medical treatment in toxic megacolon, surgery is mandatory 1

Infection Workup

• Obtain stool evaluation for infectious causes when blood or mucus is present, fever develops, or colitis symptoms emerge (watery diarrhea, cramping, urgency, nocturnal bowel movements) 1
• Consider fecal lactoferrin and calprotectin measurement; high calprotectin levels correlate with ulceration and predict need for intravenous steroids or infliximab 1
• For grade 2 or higher diarrhea/colitis, obtain abdominal/pelvic CT with contrast and gastroenterology consultation for colonoscopy or flexible sigmoidoscopy with biopsy 1

Surgical Indications (Last Resort)

Surgery is reserved only for patients with hemorrhagic shock non-responsive to resuscitation and failure of angiographic intervention; blind segmental resection without prior localization carries rebleeding rates up to 33% and mortality 33-57%. 1, 2

• Emergency subtotal colectomy mortality ranges from 27-33% versus ~10% when bleeding is first localized radiologically 2
• Diagnostic laparotomy is mandatory only after failure of all non-operative localization methods and persistent hemodynamic instability despite aggressive resuscitation 1, 4

Critical Pitfalls to Avoid

• Do not rush to colonoscopy in unstable patients—this delays definitive CTA localization and potential embolization 1, 2
• Do not assume bright red rectal bleeding is always lower GI—up to 15% may originate from the upper GI tract, especially with hemodynamic instability 2, 3
• Do not perform colonoscopy without adequate bowel preparation—inadequate prep leads to 70% repeat-procedure rates and missed lesions 2
• Do not delay surgery in critically ill patients with toxic megacolon—mortality increases significantly with delayed intervention 1
• Do not use fresh frozen plasma as first-line reversal for warfarin—prothrombin complex concentrate is faster, does not require ABO matching, and avoids volume overload 2

Anticoagulation Management

• Restart warfarin at 7 days after hemostasis for low thrombotic risk patients, or at 3 days for high thrombotic risk (e.g., mechanical mitral valve) 2, 3
• For direct oral anticoagulants, interrupt immediately and use specific reversal agents (idarucizumab for dabigatran, andexanet alfa for factor Xa inhibitors) in life-threatening hemorrhage 2, 3
• Continue aspirin if prescribed for secondary cardiovascular prevention; permanently discontinue if used only for primary prevention 2, 3

Mortality Context

• Overall in-hospital mortality for lower GI bleeding is 3.4%, rising to 20% in patients requiring ≥4 units of red blood cells 2
• Mortality is generally related to comorbidity rather than exsanguination, emphasizing the importance of optimal hemodynamic management 2, 3