Bleeding Disorder or Coagulopathy: This could be due to various reasons such as hemophilia, von Willebrand disease, or acquired coagulopathy. The presence of hematuria (blood in urine) and the taste of blood in the mouth suggests a systemic issue with blood clotting, which could lead to diffuse abdominal pain due to internal bleeding.

Urinary Tract Infection (UTI) or Pyelonephritis: While these conditions primarily cause localized pain, severe infections can lead to systemic symptoms including diffuse abdominal pain. Hematuria is a common finding, and the taste of blood could be from bleeding in the urinary tract.
Kidney Stones: Large stones can cause severe, diffuse abdominal pain and hematuria. The taste of blood might be unrelated or due to associated urinary tract infection.
Gastrointestinal Bleeding: Although more commonly associated with hematemesis (vomiting blood) or melena (black, tarry stools), a significant GI bleed could potentially cause the taste of blood in the mouth, especially if the patient has recently vomited or has blood in their stomach that they are swallowing.

Abdominal Aortic Aneurysm (AAA): Although AAA typically presents with severe, sudden-onset back or abdominal pain, it can sometimes cause more diffuse pain. Hematuria could occur if the aneurysm ruptures into the urinary system, and the taste of blood might be an unrelated symptom. Missing this diagnosis can be fatal.
Retroperitoneal Hemorrhage: This condition involves bleeding into the space behind the peritoneum and can cause diffuse abdominal pain. Hematuria could be present if the bleeding involves or compresses the urinary tract, and the taste of blood could be from swallowing blood or an unrelated cause.
Sepsis: Sepsis from any source (including urinary or gastrointestinal) can cause diffuse abdominal pain and potentially hematuria if the infection involves the kidneys. The taste of blood might be an unrelated symptom but could indicate a severe systemic infection affecting multiple systems.

Goodpasture Syndrome: An autoimmune disease that can cause glomerulonephritis (leading to hematuria) and pulmonary hemorrhage (which could explain the taste of blood in the mouth). Abdominal pain could be due to renal involvement or other systemic symptoms.
Henoch-Schönlein Purpura (HSP): A form of vasculitis that can cause abdominal pain, hematuria, and potentially the taste of blood if there is gastrointestinal involvement. It's more common in children but can occur in adults.
Thrombotic Thrombocytopenic Purpura (TTP): A rare blood disorder characterized by clotting in small blood vessels throughout the body, which can lead to a variety of symptoms including abdominal pain, hematuria, and potentially the taste of blood due to systemic microangiopathic hemolytic anemia.