Laboratory findings of hemolytic anemia consist of:
1. Reduced red cell survival and evidence of accelerated hemoglobin catabolism
2. Evidence of increased erythropoiesis.
Accelerated Hemoglobin Catabolism
Accelerated hemoglobin catabolism varies with the type of hemolysis as follows:
• Extravascular hemoglobin catabolism (see Figure 7-1)
• Intravascular hemoglobin catabolism (see Figure 7-2).
Haptoglobin Hemopexin-Heme ^-
Free Hemoglobin t
^ Albumin Methemalbumin
Fig. 7-2. Intravascular hemoglobin catabolism following intravascular hemolysis. Hemoglobin-haptoglobin, hemopexin-heme, and methemalbumin are cleared by hepatocytes. Heme is converted to iron and bilirubin. The common pathway for both extravascular and intravascular hemolysis is the conjugation of bilirubin (bilirubin glucuronide) by the hepatocytes, its excretion in bile, and ultimately formation of the urobilinogen by the bacteria in the gut. Part of urobilinogen enters in enterohepatic circulation and part is excreted by the kidney in urine, and the remainder of urobilinogen is excreted in stool (see Fig. 7-1).
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