我們報告一個雖不常見卻致命的腹部急症：大網膜自發性大量出血。這位沒有特殊過去病史及任何心血管危險因子的四十歲男性病人，到急診就醫的最初表現是出血性休克及呼吸衰竭。經過急救後，病人接受了緊急剖腹手術及大網膜切除術才保住了性命。病理學檢查發現大網膜有多處動脈有破裂及伴隨著急性和慢性炎症反應的感染性栓塞現象。大網膜自發性出血之病人若生命徵象穩定，可以先做電腦斷層掃描確診後立即接受動脈栓塞治療，但若生命徵象不穩定，則應立即進行剖腹探查。

We reported a rare but deadly case of massive spontaneous omental bleeding. This 40 year-old male who did not have any specific past medical history and any known cardiovascular risk factors, presented with decompensated hemorrhagic shock and respiratory failure. After resuscitation, he was successfully managed with emergent laparotomy and partial omentectomy. Pathology revealed focal septic emboli in multiple ruptured omental arteries associated with acute and chronic inflammation. Patients with stable vital signs should receive confirmatory CT scan followed by transarterial embolization if available, whereas patients with unstable vital signs should undergo immediate exploratory laparotomy.