A 65-year-old man on long-term anticoagulation with warfarin presents with recurrent bleeding episodes despite therapeutic INR. Laboratory investigation reveals prolonged PT/INR and low serum prothrombin levels. Which is the most common site of bleeding in vitamin K deficiency?

Explanation

## Hemorrhagic Manifestations of Vitamin K Deficiency **Key Point:** The gastrointestinal tract is the most common site of bleeding in vitamin K deficiency, accounting for the majority of hemorrhagic episodes in both acquired and warfarin-related coagulopathy. ### Pathophysiology of Vitamin K-Dependent Coagulopathy Vitamin K is essential for the γ-carboxylation of clotting factors II, VII, IX, and X. Deficiency leads to: - Impaired synthesis of vitamin K-dependent factors - Prolonged PT/INR (Factor VII has shortest half-life, affected first) - Bleeding tendency, particularly in tissues with high vascular trauma ### Why GI Tract Is Most Common | Reason | Mechanism | |--------|----------| | **Mechanical trauma** | Constant mucosal friction from food bolus passage | | **Acid exposure** | Gastric acid erodes protective mucosa | | **High vascularity** | Rich submucosal blood supply | | **Frequency of contact** | Continuous exposure to ingested material | | **Prevalence in practice** | 40–50% of bleeding episodes in vitamin K deficiency | **High-Yield:** GI bleeding (hematemesis, melena, or occult fecal blood) is the hallmark presentation of vitamin K deficiency and warfarin overdose. ### Clinical Presentation Hierarchy 1. **Mucosal bleeding** (gums, epistaxis) — early, mild 2. **Gastrointestinal bleeding** — most common serious manifestation 3. **Intracranial hemorrhage** — rare but life-threatening (typically only with severe deficiency or major trauma) 4. **Retroperitoneal/deep tissue bleeding** — uncommon without severe coagulopathy **Clinical Pearl:** In a patient on warfarin with bleeding, GI source should be assumed until proven otherwise. Upper endoscopy is often diagnostic and therapeutic. **Mnemonic:** **VIK** — **V**itamin K deficiency → **I**nternational Normalized Ratio ↑ → **K**eeps bleeding from **G**I tract (most common site). ### Why Other Sites Are Less Frequent - **Intracranial hemorrhage:** Requires severe coagulopathy or significant head trauma; occurs in <5% of vitamin K deficiency cases - **Retroperitoneal bleeding:** Rare without major trauma or severe factor deficiency - **Subdural hematoma:** Requires head injury; not a spontaneous bleeding site in vitamin K deficiency [cite:Harrison 21e Ch 179; KD Tripathi 8e Ch 47]