What is the appropriate management for an adult patient with no significant past medical history presenting with bloody diarrhea?

Management of Bloody Diarrhea in Adults

Immediately hospitalize the patient and initiate aggressive IV fluid resuscitation with 20 mL/kg boluses of Ringer's lactate or normal saline, send stool studies for bacterial culture including STEC, and hold empiric antibiotics until STEC is ruled out unless the patient has documented fever ≥38.5°C with signs of sepsis, recent international travel, or immunocompromised status. 1, 2

Immediate Risk Stratification

Upon presentation, assess for the following complications that mandate hospitalization:

• Severe dehydration: tachycardia, hypotension, altered mental status, urine output <0.5 mL/kg/h 1, 2
• Signs of sepsis: fever, tachycardia, altered mental status 1, 2
• Immunocompromised status: neutropenia, chemotherapy use, immunosuppressants 1
• Severe abdominal pain with fever and bacillary dysentery pattern (frequent scant bloody stools, fever, cramps, tenesmus) 1, 2

Fluid Resuscitation Protocol

For severe dehydration or any signs of hemodynamic instability:

• Administer immediate IV bolus of 20 mL/kg if tachycardia or sepsis is suspected 1, 2
• Continue rapid fluid administration until clinical signs of hypovolemia improve 1, 2
• Target adequate central venous pressure and urine output >0.5 mL/kg/h 1
• If oliguria persists (<0.5 mL/kg/h) despite adequate volume resuscitation, urgently consult intensive care or nephrology for risk of pulmonary edema 1

Critical Diagnostic Testing

Send immediately while initiating resuscitation:

• Stool studies: bacterial culture, Shiga toxin-producing E. coli (STEC) including O157:H7, Clostridioides difficile toxin, Salmonella, Campylobacter, Shigella 1, 2
• Complete blood count with differential to assess for neutropenia and anemia 1, 2
• Comprehensive metabolic panel for electrolytes and renal function 1, 2

Antibiotic Decision Algorithm

The IDSA provides clear guidance on when to withhold versus initiate empiric antibiotics:

DO NOT give empiric antibiotics if:

• Patient is immunocompetent and awaiting stool culture results 1, 2
• STEC is suspected or confirmed (antibiotics significantly increase risk of hemolytic uremic syndrome and mortality) 1, 2

DO give empiric antibiotics if:

• Documented fever in medical setting with severe illness, abdominal pain, and bacillary dysentery pattern presumptively due to Shigella 1, 2
• Recent international travel with temperature ≥38.5°C or signs of sepsis 1, 2
• Immunocompromised with severe illness and bloody diarrhea 1, 2

Empiric antibiotic choices when indicated:

• Adults: fluoroquinolone (ciprofloxacin) or azithromycin based on local susceptibility patterns and travel history 1, 2
• If neutropenic enterocolitis suspected: broad-spectrum coverage with piperacillin-tazobactam or imipenem-cilastatin as monotherapy, OR cefepime/ceftazidime plus metronidazole 1, 2
• If no response to antibacterials in neutropenic patients, add amphotericin for fungemia 1

Special Considerations for Neutropenic Enterocolitis

If patient is neutropenic (common in cancer patients):

• Initiate broad-spectrum antibiotics covering gram-negative enteric organisms, gram-positives, and anaerobes 1
• Add granulocyte colony-stimulating factors (G-CSF) 1
• Nasogastric decompression, bowel rest, serial abdominal examinations 1
• Avoid anticholinergics, antidiarrheals, and opioids as they aggravate ileus 1
• Blood transfusions may be necessary for bloody diarrhea 1

Surgical indications in neutropenic enterocolitis:

• Persistent GI bleeding after correcting thrombocytopenia and coagulopathy 1
• Free intraperitoneal perforation 1
• Abscess formation 1
• Clinical deterioration despite aggressive supportive measures 1

Critical Safety Warnings

Never administer:

• Antibiotics if STEC is suspected or confirmed (increases hemolytic uremic syndrome risk) 1, 2
• Loperamide or other antiperistaltic agents in bloody diarrhea or high fever (increases toxic megacolon risk and bacterial shedding) 2
• Opioids in neutropenic patients (aggravates ileus) 1

Multidisciplinary Consultation

All patients with bloody diarrhea require evaluation by:

• Gastroenterology for persistent unexplained diarrhea or severe illness 1, 3
• Infectious disease specialists if neutropenic or septic 3
• Intensive care if signs of sepsis or hemodynamic instability 3

Second-Line Therapy

If diarrhea persists despite initial treatment:

• Octreotide 100-150 mcg subcutaneous/IV three times daily, can titrate up to 500 mcg three times daily or 25-50 mcg/h continuous IV infusion 1, 3

Ongoing Management

• Reassess fluid and electrolyte balance frequently during first 2-4 hours 2
• Resume age-appropriate diet as soon as rehydrated 2
• Avoid lactose-containing products initially 2
• Continue replacing ongoing losses (urine output plus 30-50 mL/h insensible losses plus GI losses) 1