Haemoglobinuria

Haemoglobinuria is a medical condition characterized by the presence of free haemoglobin in the urine. Haemoglobin is the protein found in red blood cells that carries oxygen. When red blood cells are destroyed, or lyse, either within the bloodstream (intravascular haemolysis) or in other tissues, their haemoglobin is released. This free haemoglobin can then be filtered by the kidneys and appear in the urine.

The appearance of haemoglobinuria is typically reddish-brown or even dark red, similar to the colour of blood in urine. However, it is important to distinguish it from haematuria, which is the presence of intact red blood cells in the urine. Haemoglobinuria can occur due to various underlying causes. These include certain types of anaemia, such as paroxysmal nocturnal haemoglobinuria, where red blood cells are abnormally susceptible to destruction. Infections, particularly malaria, can also lead to haemolysis and subsequent haemoglobinuria. Certain drug reactions and transfusion reactions where incompatible blood is given can also trigger intravascular haemolysis.

The clinical significance of haemoglobinuria lies in its potential to cause kidney damage. When large amounts of free haemoglobin are filtered by the kidneys, it can precipitate and form casts within the renal tubules, leading to acute kidney injury. The management of haemoglobinuria focuses on identifying and treating the underlying cause of haemolysis. Supportive care may include fluid management to promote kidney function and, in severe cases, blood transfusions.