Differential Diagnosis for Abdominal Pain, Haematemesis, and Bleeding with High Lactate and Low Blood Pressure

• Single most likely diagnosis:
  • Upper GI bleed (e.g., peptic ulcer disease): This is the most likely diagnosis given the combination of abdominal pain, haematemesis, and melena, which are classic symptoms of upper GI bleeding. The presence of high lactate and low blood pressure suggests significant blood loss leading to hypovolemic shock.
• Other Likely diagnoses:
  • Lower GI bleed (e.g., diverticulitis, colon cancer): Although less likely than upper GI bleed given the symptoms, lower GI bleeding can also present with melena and abdominal pain, especially if the bleeding is rapid and significant.
  • Gastritis or erosive esophagitis: These conditions can cause upper GI bleeding and could explain the haematemesis and melena, though they might not fully account for the high lactate and low blood pressure without significant bleeding.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed):
  • Aortic dissection or rupture: Although abdominal pain and hypotension could suggest this diagnosis, the presence of GI bleeding symptoms makes it less likely. However, it's crucial not to miss this diagnosis due to its high mortality rate.
  • Mesenteric ischemia: This condition can cause abdominal pain, lactate elevation, and hypotension. While GI bleeding is not a primary symptom, it could occur due to bowel infarction, making this a critical diagnosis not to overlook.
  • Sepsis (from any source, including intra-abdominal infection): Sepsis can cause hypotension, elevated lactate, and abdominal pain. If an intra-abdominal source of infection is present (e.g., perforated viscus), it could potentially lead to GI bleeding.
• Rare diagnoses:
  • Hemobilia: This is a rare condition where there is bleeding into the biliary tree, which can cause GI bleeding. It's often associated with liver or biliary tract pathology and would be an unusual cause of the presented symptoms.
  • Dieulafoy's lesion: A rare cause of upper GI bleeding, characterized by a small, superficial ulceration with an exposed, often large, caliber artery at its base. It could explain the GI bleeding but is less likely to cause the other symptoms without significant blood loss.
  • Arteriovenous malformation (AVM) or angiodysplasia: These vascular anomalies can cause GI bleeding and, in rare cases, could lead to significant blood loss and the associated symptoms. However, they are less common causes of the acute presentation described.