A 70 kg adult develops watery diarrhea and loses approximately 2.0 liters of fluid stool over 24 hours. Estimate the percent of total body water lost and categorize the likely severity of dehydration using total body water = 60% of body weight and clinical thresholds: <5% mild, 5–10% moderate, >10% severe.

• A. ≈8.0% TBW lost — moderate dehydration necessitating intravenous fluid replacement even if oral hydration is possible and the patient has no comorbidities
• B. ≈2.1% TBW lost — clinically insignificant and no treatment is needed beyond encouraging oral fluids and antidiarrheal agents in all cases
• C. ≈14.3% TBW lost — severe dehydration requiring immediate intensive fluid resuscitation and blood transfusion in most adults
• D. ≈4.8% TBW lost — mild dehydration

Answer: (D)