Which laboratory finding most supports extravascular red blood cell destruction?

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Multiple Choice

Which laboratory finding most supports extravascular red blood cell destruction?

Extravascular red blood cell destruction happens when macrophages in the spleen and liver rapidly clear aging RBCs. The heme from digested RBCs is converted to unconjugated bilirubin, which the liver conjugates and excretes into bile. A lot of bilirubin reaches the gut, where bacteria convert it to urobilinogen. Some of this urobilinogen is reabsorbed and then excreted in urine, so urinary urobilinogen levels rise. This pattern—increased urobilinogen—best reflects the heightened bilirubin turnover characteristic of extravascular hemolysis. While unconjugated bilirubin can be elevated in various hemolytic processes, and a positive direct antiglobulin test points to immune-mediated cases, and LDH tends to be higher with intravascular destruction, the most specific cue for extravascular destruction in this context is the rise in urinary urobilinogen.

Extravascular red blood cell destruction happens when macrophages in the spleen and liver rapidly clear aging RBCs. The heme from digested RBCs is converted to unconjugated bilirubin, which the liver conjugates and excretes into bile. A lot of bilirubin reaches the gut, where bacteria convert it to urobilinogen. Some of this urobilinogen is reabsorbed and then excreted in urine, so urinary urobilinogen levels rise. This pattern—increased urobilinogen—best reflects the heightened bilirubin turnover characteristic of extravascular hemolysis.

While unconjugated bilirubin can be elevated in various hemolytic processes, and a positive direct antiglobulin test points to immune-mediated cases, and LDH tends to be higher with intravascular destruction, the most specific cue for extravascular destruction in this context is the rise in urinary urobilinogen.

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