Hemoglobin and hemosiderin casts are two interesting kinds of granular cast.


Cast with hemosiderin inclusion granules identical to the free granules
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Hemoglobin casts appear in acute hemolysis, for example, following transfusion of incompatible blood or in some other acquired hemolytic disorders (such as disseminated intravascular coagulation, some infections, etc.) or in some inherited hemolitic diseases (as in glucose-6-phosphate dehydrogenase deficiency and exposure to oxidizing agents). Under these circumstances the urine takes on a typical dark brown colour; if the patient is not adequately treated and remains in shock with oliguria and acid urine, a large number of hemoglobin casts usually appear, formed of finely granular "foamy" material. These casts are very fragile and tend to conglomerate if the sediment is centrifuged rapidly (in these circumstances it is advisable to examine

the unspun sediment in the collecting flask). With adequate anti-shock therapy, forced diuresis, and intravenous sodium bicarbonate administration to produce a urinary pH of up to 7 or greater, this finding generally disappears in a few hours, and in this case the absence of casts and hematuria can be taken as a sign of a good prognosis.


Cast with hemosiderin inclusion granules. Prussian Blue staining
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Unstained hemosiderin casts are similar to red cell granular casts and are not generally associated with hematuria. Free, scattered, pigmented granules, in the absence of red cells, are a clue to their identity, which can be confirmed by staining with Prussian blue. Hemosiderin casts are a sign of a chronic hemolysis. A good example of this was common in patients with old types of prosthetic heart valves.