A 42-year-old man is brought to the emergency department with a history of intentional ingestion of white powder suspected to be arsenic trioxide. Which is the most common organ system affected in acute arsenic poisoning?

Explanation

## Most Common Organ System Affected in Acute Arsenic Poisoning **Key Point:** The **gastrointestinal tract** is the most commonly and severely affected organ system in acute arsenic poisoning, regardless of the route of exposure. ### Pathophysiology of Acute Arsenic Toxicity **High-Yield:** Arsenic (As³⁺) binds to sulfhydryl groups (-SH) in cellular proteins and enzymes, disrupting: - Pyruvate dehydrogenase (impairs energy metabolism) - Cytochrome c oxidase (blocks oxidative phosphorylation) - Glutathione reductase (depletes antioxidant defenses) - Cell membrane integrity ### Organ System Involvement in Acute Poisoning | System | Manifestations | Frequency | Severity | | --- | --- | --- | --- | | **GI Tract** | Nausea, vomiting, abdominal pain, hemorrhagic diarrhea, mucosal erosion | **Most common** | **Most prominent** | | Cardiovascular | Hypotension, arrhythmias, myocarditis, QT prolongation | Common | Variable | | CNS | Encephalopathy, confusion, seizures (late) | Less common | Late manifestation | | Renal | Acute kidney injury, proteinuria | Common | Secondary | | Hepatic | Hepatotoxicity, cirrhosis (chronic) | Moderate | Chronic exposure | ### Why GI Tract is Most Affected 1. **Direct contact**: Ingested arsenic directly contacts gastric and intestinal mucosa 2. **High epithelial turnover**: GI epithelium has rapid cell division → high metabolic demand → vulnerable to arsenic's energy-blocking effects 3. **First manifestation**: GI symptoms appear within 30 minutes to 2 hours of ingestion 4. **Severity**: Hemorrhagic gastroenteritis can lead to: - Fluid loss and hypovolemia - Electrolyte derangement - Secondary shock - Death (if untreated) **Clinical Pearl:** The classic presentation of acute arsenic poisoning is **"burning in the mouth and throat → severe vomiting and abdominal pain → profuse watery/hemorrhagic diarrhea → cardiovascular collapse."** The GI phase dominates the early clinical picture. ### Timeline of Acute Arsenic Poisoning ```mermaid flowchart TD A[Arsenic ingestion]:::action --> B[0-2 hours: GI symptoms]:::outcome B --> C[Nausea, vomiting, abdominal pain]:::outcome C --> D[Hemorrhagic diarrhea]:::outcome D --> E[Fluid loss & hypovolemia]:::urgent E --> F{Untreated?}:::decision F -->|Yes| G[Cardiovascular collapse, shock]:::urgent F -->|No| H[Recovery or chronic phase]:::outcome G --> I[Multi-organ failure, death]:::urgent ``` ### Differential Organ Involvement **Cardiovascular effects** (2nd most common): - Occur due to hypovolemia from GI losses - Direct myocardial toxicity (arsine gas → hemolysis; As³⁺ → myocarditis) - Arrhythmias and QT prolongation - **However**: These are secondary to GI fluid loss, not primary **CNS effects** (less common in acute poisoning): - Encephalopathy and confusion occur in severe cases - Seizures are late manifestations - More prominent in chronic arsenic poisoning **Renal effects** (secondary): - Acute kidney injury from hypovolemia and direct tubular toxicity - Proteinuria and hematuria - Develops after GI and cardiovascular phases **Mnemonic:** **GI CARD** for acute arsenic poisoning sequence: - **G**astrointestinal (first, most severe) - **I**ntense fluid loss - **C**ardiovascular collapse (secondary) - **A**cute kidney injury - **R**espiratory failure (late) - **D**eath (if untreated) ### Key Distinguishing Features **Acute arsenic poisoning** → **GI-dominant** presentation **Chronic arsenic poisoning** → **Skin, PNS, CNS** manifestations (hyperpigmentation, hyperkeratosis, peripheral neuropathy, Mees' lines) **High-Yield:** In exam questions: - **Acute poisoning** = ask about GI symptoms - **Chronic poisoning** = ask about skin/nail changes and neuropathy