What is the condition known as when there is free hemoglobin present in urine?

The condition characterized by the presence of free hemoglobin in urine is known as hemoglobinuria. This occurs when hemoglobin, the iron-containing protein in red blood cells that carries oxygen, is released into the bloodstream and subsequently filtered by the kidneys into the urine. This situation can arise from various causes, including hemolytic anemia, severe muscle injury, or certain infections.

In contrast, hematuria refers specifically to the presence of intact red blood cells in urine, which may suggest different underlying conditions such as urinary tract infections or kidney stones. Myoglobinuria is the passage of myoglobin, a protein released from damaged muscles, into the urine, which can be seen in conditions like muscle necrosis. Proteinuria indicates the presence of general proteins in urine and is often assessed in kidney disease but does not specifically indicate hemoglobin.

Understanding these distinctions is crucial for diagnosing and addressing urinary conditions accurately.