Gastrointestinal · Year 2 · from Gastrointestinal
Case 2: Cholera (Secretory Diarrhea)
Patient Presentation
Demographics: 32-year-old male
Chief Complaint: Severe watery diarrhea for 18 hours
History of Present Illness: The patient recently returned from a humanitarian trip to Bangladesh 3 days ago. He developed sudden onset of profuse watery diarrhea, initially with cramping that resolved as diarrhea progressed. He estimates passing 15-20 stools in the past day. The stool has a "rice-water" appearance without blood or mucus. He also has muscle cramps and feels extremely weak.
Past Medical History: Healthy, no prior illnesses
Social History: Traveled to rural Bangladesh, consumed local food and water
Physical Examination
- Vital Signs: BP 78/50 mmHg, HR 132 bpm, Temperature 37.0C, RR 24/min
- General: Lethargic, severely dehydrated male
- HEENT: Sunken eyes, dry mucous membranes, poor skin turgor
- Cardiovascular: Tachycardic, weak pulses
- Abdomen: Soft, mild diffuse tenderness, hyperactive bowel sounds
Workup and Results
- Chemistry: Na 152 mEq/L, K 2.4 mEq/L, Cl 118 mEq/L, HCO3 12 mEq/L, BUN 58 mg/dL, Cr 2.8 mg/dL
- Stool Analysis: Watery, no blood or WBCs, positive for Vibrio cholerae on culture
- ABG: pH 7.18, metabolic acidosis with anion gap 22
Diagram illustrating the mechanism of cholera toxin causing secretory diarrhea through irreversible activation of Gs protein and adenylyl cyclase, leading to continuous CFTR-mediated chloride secretion.
Image Source: Wikimedia Commons, Public Domain
Diagnosis
Cholera (Vibrio cholerae infection)
Clinical Correlation to Intestinal Secretion Physiology
Cholera toxin enters intestinal epithelial cells and irreversibly activates the Gs alpha subunit that stimulates adenylyl cyclase. The resulting massive, sustained increase in cAMP continuously activates CFTR chloride channels on the apical membrane. Chloride secretion into the lumen creates an electrical gradient drawing sodium paracellularly, and water follows osmotically. This produces secretory diarrhea that can exceed 10-20 liters daily. Critically, glucose-coupled sodium absorption via SGLT1 remains functional even when chloride secretion is maximally stimulated. This is the physiologic basis for oral rehydration solution (ORS), which provides glucose and sodium together to drive sodium and water absorption despite ongoing secretion.
Treatment
- Aggressive IV fluid resuscitation (Lactated Ringer's or normal saline)
- Oral rehydration solution (ORS) when able to tolerate
- Potassium replacement
- Antibiotics (doxycycline or azithromycin) to reduce duration and shedding
- Monitor for renal recovery and electrolyte normalization