In acute arsenic poisoning, which organ system is primarily affected in the early phase, leading to the characteristic 'rice-water' stools?

Explanation

## Acute Arsenic Poisoning: Pathophysiology and Clinical Presentation ### Phases of Acute Arsenic Toxicity **Key Point:** Acute arsenic poisoning presents in three distinct phases, with gastrointestinal manifestations dominating the early phase (0–24 hours). ### Phase 1: Gastrointestinal Phase (0–24 hours) - **Onset:** Rapid, within 30 minutes to 2 hours of ingestion - **Mechanism:** Direct corrosive effect on mucous membranes; inhibition of cellular respiration via interference with pyruvate dehydrogenase - **Classic Signs:** - Burning sensation in mouth and throat - Severe abdominal pain and cramping - **Rice-water stools** (watery, odorless, resembling cholera stools) - Profuse vomiting and diarrhea - Dehydration and electrolyte loss ### Phase 2: Cardiovascular Phase (24–72 hours) - Hypotension, shock, and arrhythmias - Myocarditis and QT prolongation on ECG - Pulmonary edema ### Phase 3: Neurological Phase (after 72 hours) - Peripheral neuropathy (sensorimotor) - Encephalopathy (if severe) **High-Yield:** The rice-water stools in arsenic poisoning are a direct result of increased intestinal secretion and mucosal damage, NOT due to cholera toxin (which is the cause in actual cholera). **Mnemonic:** **ABCDE of Acute Arsenic Poisoning** - **A**bdominal pain (severe) - **B**urning sensation (mouth/throat) - **C**ardiovascular collapse (late) - **D**iarrhea (rice-water) - **E**lectrolyte loss (severe) **Clinical Pearl:** The gastrointestinal phase is the most critical window for intervention. Aggressive fluid and electrolyte replacement is essential to prevent hypovolemic shock.