About Hemolytic Uremic Syndrome (HUS)

Overview
Hemolytic uremic syndrome (HUS) is a kidney condition characterized by the destruction of red blood cells, which then block the filtering system of the kidneys. Red blood cells contain hemoglobin, a protein that carries oxygen throughout the body. When damaged red blood cells clog the tiny filtering units in the kidneys called glomeruli, the kidneys are unable to function properly. This can lead to acute kidney injury, which is a sudden and temporary loss of kidney function. HUS is the most common cause of acute kidney injury in children. It can be caused by various factors, including infections with certain strains of Escherichia coli (E. coli) bacteria or genetic mutations affecting the complement pathway in the immune system. Treatment options for HUS vary depending on the underlying cause and may include supportive care and specific medications.
Causes and Risk Factors

The causes of HUS include:

  • Infection with Shiga toxin-producing Escherichia coli (STEC-HUS): This is the most common cause of HUS, typically contracted through the ingestion of contaminated food or water. The release of Shiga toxin leads to endothelial damage, complement cascade activation, and thrombotic microangiopathy primarily affecting the kidneys.
  • Invasive infections with Streptococcus pneumoniae (P-HUS): Although less common, invasive pneumococcal disease can cause a specific form of HUS. The exact mechanism is not fully understood, but alternative complement pathway activation may contribute to disease development.

Non-modifiable risk factors for HUS are factors that cannot be changed. These include:

  • Age: HUS is more commonly seen in children, especially those under the age of 5.
  • Genetic predisposition: Certain genetic mutations or abnormalities in complement-regulating genes can increase the risk of developing HUS.

Modifiable risk factors for HUS are factors that can be changed or influenced. However, these factors are not well-established. However, it is important to practice good hygiene and food safety measures to reduce the risk of infection with STEC-HUS.

Symptoms

The most common early symptoms of hemolytic uremic syndrome in children include:

  • Vomiting
  • Bloody diarrhea
  • Abdominal pain
  • Fever
  • Chills
  • Headache

As the infection progresses and the toxins released in the intestine destroy red blood cells, additional symptoms may occur. These symptoms include:

  • Fatigue or feeling tired
  • Weakness
  • Fainting
  • Paleness

In later stages, progression, or higher severity of HUS, other symptoms may manifest, such as:

  • Bruising
  • Seizures

It's important to note that HUS can also lead to kidney damage and acute kidney injury. The kidneys may become damaged, resulting in decreased urine production and increased workload to remove waste and fluid from the blood. Symptoms of acute kidney injury include:

  • Hematuria (blood in urine)
  • Shortness of breath
  • Swelling in legs, ankles, and feet
  • Less urine (lower volume) than usual

If you or someone you know is experiencing symptoms of HUS, it is important to consult a healthcare professional for a proper evaluation and guidance.

Diagnosis

To diagnose hemolytic uremic syndrome, health care providers commonly perform the following examinations, tests, and procedures:

  • Medical and Family History: Gathering information about the patient's medical history and family history helps in the diagnosis of HUS.
  • Physical Exam: A thorough physical exam is conducted to look for physical signs of a medical problem, such as pain, swelling, or masses in the body.
  • Urine Tests: Several urine tests may be ordered to assess kidney damage caused by HUS. These tests include a dipstick test for albumin, which detects the presence of albumin in the urine.
  • Blood Test: A blood draw is often performed to evaluate various parameters such as red blood cell count, platelet count, and kidney function.
  • Stool Test: A stool sample may be examined to check for the presence of certain bacteria that are associated with HUS.

In addition to these diagnostic procedures, health care providers may recommend further examinations, tests, and procedures to determine the stage or severity of HUS. These additional evaluations can include:

  • Imaging Studies: X-rays or MRI scans may be conducted to assess the extent of organ damage or complications related to HUS.
  • Kidney Biopsy: In some cases, a small sample of kidney tissue may be taken for examination under a microscope to evaluate the severity of kidney damage.

It's important to remember that these examinations, tests, and procedures should be performed by health care professionals based on individual circumstances. If you suspect you or your child has HUS, consult your health care provider for proper diagnosis and guidance.

Treatment Options

The goals of treatment for hemolytic uremic syndrome are to address urgent symptoms, prevent complications, and manage the underlying causes. Here are the various treatment approaches and how they work to achieve these goals:

Medications:

  • Antibiotics: Generally, antibiotics are not used unless there are infections in other parts of the body.
  • Anti-complement therapy: This is effective in atypical HUS, which is characterized by uncontrolled activation of the alternative complement pathway. It helps reduce kidney failure.

Therapies and Therapeutic Procedures:

  • Plasma Exchange (PEX): This is considered a standard treatment for both HUS and thrombotic thrombocytopenic purpura (TTP). PEX removes antibodies against ADAMTS-13 and supplements ADAMTS-13 via fresh frozen plasma (FFP), preventing further clot formation.
  • Dialysis: If acute kidney injury occurs, dialysis may be necessary to filter waste products and extra fluid from the body. There are two types of dialysis: hemodialysis and peritoneal dialysis.
  • Supportive care: This includes replacing minerals and fluids through intravenous (IV) tubes, providing red blood cells and platelets through IV, and managing high blood pressure with medications.

Other Treatments:

  • Kidney Transplantation: In cases where significant kidney damage develops into chronic kidney disease (CKD), a kidney transplant may be necessary to replace the failing kidneys with a healthy one from a deceased or living donor.

It's important to note that specific treatments may vary depending on the underlying cause of HUS. Consulting with a healthcare professional is crucial for personalized treatment plans.

Medication dosing may be affected by many factors. Check with your health care professional about dosing for your individual situation. Other side effects can occur. Check with your health care professional or read the information provided with your medication for additional side effect information.