Symptoms are related to where in the body blood clots form.
Diagnosis is based on the person's symptoms and blood tests.
Treatment of HUS is support of key body functions and sometimes hemodialysis, and some people may benefit from the drug eculizumab.
(See also Overview of Platelet Disorders Overview of Platelet Disorders Platelets (sometimes called thrombocytes) are cell fragments produced in the bone marrow that circulate in the bloodstream and help blood to clot. Thrombopoietin, primarily produced in the liver... read more and Overview of Thrombocytopenia Overview of Thrombocytopenia Thrombocytopenia is a low number of platelets (thrombocytes) in the blood, which increases the risk of bleeding. Thrombocytopenia occurs when the bone marrow makes too few platelets or when... read more .)
HUS is a rare disorder in which many small blood clots (thrombi) form suddenly throughout the body. Hemolytic means that red blood cells break down, and uremic means that kidney injury causes urea (a waste product) to accumulate in the blood. HUS is related to thrombotic thrombocytopenic purpura Thrombotic Thrombocytopenic Purpura (TTP) Thrombotic thrombocytopenic purpura (TTP) is a serious disorder that involves the formation of small blood clots throughout the body that block the flow of blood to vital organs such as the... read more (TTP), but it occurs more often in children and more often causes kidney failure, whereas TTP is more common among adults.
The small blood clots that form in HUS block small blood vessels throughout the body, particularly those in the brain, heart, and kidneys. The blood vessel blockage damages organs and can break apart red blood cells that pass through partially blocked vessels. The blood clots also mean that an abnormally high number of platelets are being used up, which leads to a sharp decrease in the number of platelets in the bloodstream (thrombocytopenia).
Platelets are cells that are made in the bone marrow and circulate in the bloodstream and help blood clot How Blood Clots Hemostasis is the body's way of stopping injured blood vessels from bleeding. Hemostasis includes clotting of the blood. Too little clotting can cause excessive bleeding from minor injury Too... read more . Platelets are sometimes called thrombocytes. Having too few platelets is termed thrombocytopenia Overview of Thrombocytopenia Thrombocytopenia is a low number of platelets (thrombocytes) in the blood, which increases the risk of bleeding. Thrombocytopenia occurs when the bone marrow makes too few platelets or when... read more .
Hemolytic-uremic syndrome usually occurs following an intestinal infection that results from ingestion of food contaminated with the bacteria Escherichia coli O157:H7 E. coli O157:H7 infection Escherichia coli (E. coli) are a group of gram-negative bacteria that normally reside in the intestine of healthy people, but some strains can cause infection in the digestive... read more or other toxin-producing bacteria.
Symptoms of HUS
In hemolytic-uremic syndrome (HUS), symptoms develop suddenly.
Symptoms in HUS are quite distinct from symptoms of most other forms of thrombocytopenia.
In HUS, children usually first have vomiting and diarrhea. The diarrhea is often bloody. The main symptoms of complications of HUS are related to blood clots that develop in the kidneys, causing damage that is usually severe and often progresses to kidney failure Overview of Kidney Failure This chapter includes a new section on COVID-19 and acute kidney injury (AKI). Kidney failure is the inability of the kidneys to adequately filter metabolic waste products from the blood. Kidney... read more , requiring dialysis Dialysis Dialysis is an artificial process for removing waste products and excess fluids from the body, a process that is needed when the kidneys are not functioning properly. There are a number of reasons... read more . HUS does not often cause brain symptoms.
Diagnosis of HUS
Blood tests to measure platelet count and clotting
Blood and urine tests to measure kidney function
Tests to rule out other disorders that cause a low platelet count and bleeding
Doctors suspect hemolytic-uremic syndrome (HUS) when they find a low platelet count in children who have been ill or, less commonly, in those who have taken certain drugs.
Although there are no blood tests that specifically diagnose HUS, doctors do a number of blood tests that, together with people's symptoms, help make the diagnosis. These blood tests often include a complete blood count, tests demonstrating that red blood cells are being destroyed such as examination of a sample of blood under a microscope (blood smear), and tests to determine how well the kidneys are working.
Treatment of HUS
Usually kidney dialysis
Sometimes the drugs eculizumab or ravulizumab
About half of children with hemolytic-uremic syndrome temporarily require kidney dialysis Dialysis Dialysis is an artificial process for removing waste products and excess fluids from the body, a process that is needed when the kidneys are not functioning properly. There are a number of reasons... read more , in which a dialysis machine removes waste products from the blood. Most often, the kidneys recover, but some children have permanent kidney damage. Eculizumab and ravulizumab are drugs that suppress complement Complement System One of the body's lines of defense (immune system) involves white blood cells (leukocytes) that travel through the bloodstream and into tissues, searching for and attacking microorganisms and... read more , a component of the immune system. They reduce the rate of kidney damage, and in some people, they may rapidly restore kidney function. People who take eculizumab or ravulizumab are at higher risk than normal for meningococcal meningitis Meningococcal Infections Meningococcal infections are caused by the bacteria Neisseria meningitidis (meningococci) and include meningitis and sepsis. Infection is spread by direct contact with nasal and throat... read more , so they should receive the meningococcal vaccine Prevention Meningococcal infections are caused by the bacteria Neisseria meningitidis (meningococci) and include meningitis and sepsis. Infection is spread by direct contact with nasal and throat... read more to prevent meningococcal infections.