Haemoglobinuria
Haemoglobinuria is a condition where the oxygen-carrying protein from red blood cells appears in the urine, often turning it a dark reddish or brown color. This happens when red blood cells break down inside blood vessels, releasing their contents into the bloodstream, which the kidneys then filter into the urine.
Table of contents
- What is haemoglobinuria?
- The difference between haemoglobinuria and hematuria
- What causes haemoglobinuria?
- Symptoms
- How is haemoglobinuria diagnosed?
- Treatment approaches
- Related conditions
What is haemoglobinuria?
Haemoglobinuria is a condition in which the oxygen transport protein haemoglobin is found in abnormally high concentrations in the urine[1]. Haemoglobin is a molecule contained within red blood cells that helps transport oxygen and carbon dioxide through the body[3].
Red blood cells normally live for about one hundred and twenty days and then break down into parts that can produce new red blood cells. This breakdown normally occurs in the spleen, bone marrow, and liver[3]. However, when red blood cells break down in the blood vessels instead, the components, including haemoglobin, move through the bloodstream and are eventually filtered by the kidneys into the urine[3].
The condition is caused by excessive intravascular haemolysis, in which large numbers of red blood cells are destroyed inside blood vessels, thereby releasing free haemoglobin into the plasma[1]. Excess haemoglobin is filtered by the kidneys, which excrete it into the urine, giving urine a purple, reddish, or brown color[1][3]. Haemoglobinuria can lead to acute tubular necrosis, which is an uncommon cause of death in patients recovering in intensive care units[1].
The difference between haemoglobinuria and hematuria
Both haemoglobinuria and hematuria can cause blood to appear in the urine, but they are different conditions. The difference is that hematuria is red blood cells in your urine, while haemoglobinuria is haemoglobin in your urine[2]. Haemoglobin is the protein in red blood cells that makes blood look red[2].
In hematuria, whole red blood cells pass into the urine. In haemoglobinuria, the red blood cells have already broken apart inside the blood vessels, and only the haemoglobin protein passes into the urine[3].
What causes haemoglobinuria?
A number of conditions and factors can lead to haemoglobin in the urine. These include[1][3]:
- Acute glomerulonephritis
- Burns
- Kidney cancer or renal cancer
- Kidney disease
- Malaria
- Pyelonephritis (kidney infection)
- Sickle cell anaemia
- Tuberculosis of the urinary tract
- Transfusion reactions
- Glucose-6-phosphate dehydrogenase deficiency
- IgM autoimmune haemolytic anaemia
- Microangiopathies, such as haemolytic-uremic syndrome or thrombotic thrombocytopenic purpura, leading to microangiopathic haemolytic anaemia
- March haemoglobinuria secondary to repetitive impacts on the body, usually the feet
- Athletic nephritis secondary to strenuous exercise
- Acute lead poisoning
There is also a genetic condition known as paroxysmal nocturnal haemoglobinuria (PNH), which is caused by a spontaneous genetic mutation rather than an inherited gene. PNH involves a defective protein on the surface of the red blood cells, which causes the immune system to attack them and destroy them. This condition is destructive and even life-threatening if left untreated[3].
Symptoms
The main symptom that a patient with haemoglobinuria displays is a change in the color of the urine, which will turn reddish, brown, or dark[3]. This discoloration is most noticeable in some cases early in the morning, upon passing urine that has accumulated in the bladder during the night[2].
Haemoglobinuria can also be accompanied by[3]:
- Shortness of breath
- Headaches
- Arrhythmia (irregular heartbeat)
- Chest pain
- Abdominal pain
- Bruising easily
- Blood clots
Haemoglobinuria is itself a symptom of other conditions, so additional symptoms may be present depending on the underlying cause[3].
How is haemoglobinuria diagnosed?
The diagnosis of haemoglobinuria is often made based on the medical history, blood samples, and a urine sample[1]. The test involves only normal urination, so there is no discomfort[6].
Haemoglobinuria is detected with an analysis of the urine and blood[3]. The absence of urine red blood cells and red blood cell casts when examined under a microscope, despite a positive dipstick test, suggests haemoglobinuria or myoglobinuria[1]. A dipstick test is a simple urine test that uses a strip that changes color to detect certain substances.
Normally, haemoglobin does not appear in the urine[6]. If the level of haemoglobin in the blood rises too high, then haemoglobin begins to appear in the urine[6].
Treatment approaches
The treatment for haemoglobinuria will depend on the underlying cause[3]. Since haemoglobinuria is a symptom of other medical conditions rather than a disease itself, treatment focuses on identifying and addressing the root cause.
In the case of paroxysmal nocturnal haemoglobinuria, the only cure is a bone marrow transplant[3]. However, various treatments exist to manage the symptoms and prevent complications of the conditions that cause haemoglobinuria.
Healthcare providers may recommend supportive care and monitoring of complications associated with the breakdown of red blood cells. This may include maintaining proper hydration and kidney function, as the excess haemoglobin filtered through the kidneys can potentially cause kidney damage[1].
Related conditions
Haemoglobinuria is closely related to several blood and kidney disorders. One of the most important related conditions is paroxysmal nocturnal haemoglobinuria (PNH), a rare blood disorder that happens when part of the immune system attacks and damages red blood cells and platelets[2].
Other conditions associated with or causing haemoglobinuria include haemolytic anaemia, which occurs when red blood cells are destroyed faster than the body can replace them. Chronic kidney disease can develop as a complication when haemoglobinuria is left untreated[2].
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Hemoglobinuria