What are the caustic gastrointestinal effects of an acute iron overdose and how should it be managed?

Caustic Gastrointestinal Effects of Acute Iron Overdose

Acute iron overdose causes direct corrosive injury to the gastrointestinal mucosa, ranging from superficial hemorrhagic gastritis to complete transmural necrosis and perforation, with the most severe damage typically occurring in the stomach and proximal small bowel, though enteric-coated preparations can cause distal intestinal injury. 1, 2, 3

Pathophysiology of GI Caustic Injury

Iron acts as a direct corrosive agent to the gastrointestinal tract through multiple mechanisms:

• Direct mucosal toxicity: Elemental iron concentrations cause direct chemical burns to the GI mucosa, with injury severity correlating to the amount ingested 1, 2
• Vascular injury: Iron causes damage to mesenteric vessels leading to hemorrhagic gastritis, bowel ischemia, and potential complete infarction 3, 4
• Location of injury: Liquid iron preparations transit rapidly and damage the esophagus and stomach, while solid tablets cause maximum damage where they lodge—typically the stomach and proximal small bowel 5, 1
• Enteric-coated preparations: These can cause severe distal small bowel injury with complete sparing of proximal portions, as the coating delays iron release 4

Clinical Manifestations by Severity

Significant GI toxicity threshold:

• ≥20 mg/kg elemental iron: Causes significant gastrointestinal manifestations 2
• ≥60 mg/kg elemental iron: Associated with systemic toxicity and severe mucosal injury 1, 2, 3

Acute phase (hours):

• Hemorrhagic gastritis with hematemesis and melena 1, 3
• Necrotizing gastroenteritis requiring blood transfusion 1
• Mucosal ulceration and necrosis 3, 4
• Complete bowel infarction in severe cases 4

Late complications (weeks):

• Gastric or intestinal stricture formation requiring surgical intervention 4
• Bowel obstruction from scarring 3, 4
• Pyloric stenosis 3

Management Algorithm

Immediate Assessment (within first hours):

1. Estimate total elemental iron ingested to determine severity and guide intervention intensity 1, 2
2. Obtain abdominal radiograph to visualize iron tablets in the GI tract and assess burden 1, 2
3. Measure serum iron concentration within 8 hours of ingestion; levels >500 μg/dL indicate need for aggressive chelation 2, 3
4. Check for clinical signs of severe toxicity: shock, coma, hyperglycemia, leukocytosis, and metabolic acidosis 1, 3

GI Decontamination Strategy:

For patients with visible tablets on radiograph:

• Gastric lavage with deferoxamine-sodium bicarbonate solution to remove unabsorbed iron and neutralize local corrosive effects 1
• Whole-bowel irrigation with polyethylene glycol-electrolyte solution for iron concretions or multiple tablets, continuing until serum iron normalizes 1, 6
• Surgical gastrotomy only for massive tablet burden unresponsive to medical decontamination or evidence of perforation 6

Important caveat: Ipecac and standard gastric lavage have questionable efficacy, and activated charcoal does not bind iron 6

Chelation Therapy:

Indications for IV deferoxamine (choose one):

• Serum iron >500 μg/dL measured within 8 hours of ingestion 2
• Serious clinical symptoms (shock, coma, severe acidosis) regardless of serum iron level 1, 2
• Evidence of systemic toxicity with metabolic derangements 3

Administration protocol:

• Continuous IV infusion for 24-48 hours until serum iron normalizes 1
• Monitor for vin rosé (pink) colored urine indicating ferrioxamine excretion 3
• Continue until serum iron <100-150 μg/dL and clinical improvement occurs 1

Supportive Care Priorities:

1. Maintain intravascular volume with aggressive fluid resuscitation for shock 3
2. Correct metabolic acidosis with sodium bicarbonate 3
3. Transfuse packed red blood cells for hemorrhagic gastroenteritis with significant blood loss 1
4. Correct coagulation disorders that develop from hepatotoxicity 3

Monitoring for Late Complications:

• Protracted abdominal pain beyond the acute phase should prompt evaluation for stricture formation or delayed perforation 4
• Endoscopic or radiographic evaluation at 2-4 weeks post-ingestion if persistent GI symptoms develop 4
• Surgical consultation for evidence of obstruction or perforation 4

Critical Pitfalls to Avoid

Do not rely on absence of oral lesions or initial symptoms to rule out severe GI injury—clinical symptoms correlate poorly with extent of damage 5

Do not delay chelation therapy while waiting for serum iron results if clinical presentation suggests severe toxicity 1, 2

Do not assume proximal GI tract is involved with enteric-coated preparations—distal small bowel injury can occur with complete sparing of stomach and duodenum 4

Do not discontinue monitoring after acute phase as strictures can develop weeks later requiring surgical intervention 3, 4