The presence of hemoglobin in the urine should not be confused with hematuria, that is, with urinary loss of blood; in fact, hemoglobin is only one component of red blood cells, which in turn are just one of the many corpuscular parts of the blood. However, both conditions are accumulated by the reddish coloring of the urine, since it is precisely the hemoglobin rich in oxygen to give arterial blood its typical red color; on the contrary, venous blood is darker, because it is rich in deoxygenated hemoglobin.
Ultimately, therefore, hemoglobinuria does not necessarily reflect a loss of blood with the urine, but only of blood pigments (hemoglobin) that color it red.
Hematuria is often accompanied by hemoglobinuria, caused by the hemolysis of red blood cells contained in the urine, while hemoglobinuria can be separated from hematuria, because it is often supported by the aforementioned phenomena of excessive intravascular hemolysis.
Another important clarification is that the excretion of reddish urine is not necessarily synonymous with hematuria or hemoglobinuria; in fact, a urine of this color may simply be due to a contamination with menstrual flow or to the intake of particular foods or drugs.
For what has been said, the presence of hemoglobin in the urine gives them a homogeneous red-brown color. Among the various symptoms that can be associated with hemoglobinuria, in relation to the cause of origin, we remember fever, chills, enlargement of the spleen (splenomegaly), skin pallor, tachycardia, shortness of breath, weakness and jaundice.
