What is Shiga toxin-producing E. coli hemolytic uremic syndrome (STEC HUS)?
STEC HUS is a condition caused by a toxin that is produced by E coli. E. coli is a type of bacteria that can cause fever, vomiting, abdominal pain and diarrhea. Some strains of E coli produce the Shiga toxin. Not all infected children will develop kidney problems caused by the toxin. STEC HUS can develop in up to 20 per cent of children infected with a Shiga toxin-producing E coli about five to 10 days after the initial infection, and about half of them will require hemodialysis. STEC HUS is most often seen in children under the age of 5. The toxin damages small blood vessels in the kidney, brain and other organs. The damage to small blood vessels in the kidney affects how the kidney functions. Damage to other small blood vessels in the body cause red blood cells in the blood to break apart and levels of platelets in the blood to drop. The breakdown of platelets also clogs blood vessels in the kidney and other organs.
How STEC HUS affects the body
STEC HUS most often affects the kidneys, platelets and red blood cells. It can also affect the brain and other organs.
The kidneys
Most people are born with two kidneys. The kidneys take excess water and chemical waste products out of the blood and turn them into urine (pee). The urine then flows out of the body.
When a child has STEC HUS, the toxin damages small blood vessels in the kidneys. The kidneys then cannot clean the blood properly or make the normal amount of urine. Extra fluid and chemical wastes build up in the body. This can cause several problems:
- If fluid builds up in the blood vessels, your child's blood pressure will rise. Very high blood pressure can cause blurred vision, headaches, seizures and irritability.
- If fluid builds up in the soft tissues, your child will have puffiness and swelling.
- If fluid builds up in the lungs, your child may have trouble breathing.
- If the waste product potassium builds up in the blood, it may cause an irregular heartbeat or even stop the heart from beating.
- If the waste product urea builds up in the blood, it may make your child sleepy or irritable (cranky). It may also make your child's breath smell bad.
The blood
Our blood contains three different types of cells:
- Red blood cells carry oxygen on a protein called hemoglobin to all our tissues and organs.
- White blood cells help fight infection.
- Platelets are "sticky cells" that help the blood to clot.
As the blood flows through blood vessels damaged by the toxin in STEC HUS, platelets get stuck and red blood cells may break apart. This causes the platelet count and hemoglobin and red blood cells to drop.
- A low platelet count (thrombocytopenia) can be associated with bruising and easy bleeding. Nosebleeds or bleeding from the gums are common signs of a low platelet count.
- A low red blood cell count is called anemia. Children with anemia may look pale and feel tired.
The brain
STEC HUS may also affect the blood vessels in the brain. This can make your child cranky, tired and more demanding. In severe cases, your child can show signs of stroke, weakness, seizures or a change in their level of alertness. Seizures can be treated with medication and usually disappear when a child recovers from STEC HUS.
Symptoms of hemolytic uremic syndrome
Early symptoms
If your child has a Shiga toxin-producing E. coli infection, they may vomit, have diarrhea (with or without blood), have fever or abdominal pain. These symptoms are also seen with many other types of infectious diarrhea.
Later symptoms
These are some signs of STEC HUS that appear after several days:
- blood in the urine or dark urine
- blood in the stool (poop)
- bruises that are not caused by injuries
- less urine
- puffiness around the eyes and ankles
- paleness
- higher blood pressure
- sleepiness
- irritability
- headaches
- seizures
Blood tests may show a low hemoglobin and low platelet count as well as abnormal kidney function and electrolyte levels. A stool test can check for presence of the Shiga toxin-producing E. coli.
Cause of STEC HUS
STEC HUS most commonly follows an infection of the intestines
Healthy people have several types of E. coli living in their intestines. Shiga toxin-producing E. coli are different strains that can be very harmful. They can come from contaminated food, drink or another source, including other people who are sick with the infection.
Treatment of STEC HUS
Children with STEC HUS may require treatment for:
- blood pressure
- electrolyte abnormalities
- anemia (low hemoglobin)
- thrombocytopenia (low platelets)
- poor kidney function
- seizures
Your child may need dialysis
Dialysis is a common treatment for severe STEC HUS. A dialysis machine removes water and chemical wastes from the blood and returns clean blood to the body. Dialysis takes over most of the work of the kidneys while the kidneys are getting better. Usually, dialysis is started soon after diagnosis if the kidneys are severely affected. It can go on for two to three weeks or even longer.
Preventing STEC HUS
The best way to prevent STEC HUS is to prevent infection with a Shiga toxin-producing E. coli. Proper hand washing, avoiding unpasteurized milk and dairy products, avoiding undercooked meat products, proper food handling and avoiding others who are known to be infected are all effective measures in reducing transmission.
Once a child is infected with a Shiga toxin-producing E. coli, however, there are few methods to reduce the risk of developing STEC HUS. Antibiotics and anti-diarrheal medications are ineffective in reducing the incidence of STEC HUS. In fact, they may increase the risk. Oral toxin-binding agents are not effective in preventing STEC HUS.
The only treatment that may prevent STEC HUS in children infected with a Shiga toxin-producing E. coli is hydration with high volumes of IV fluids.
Outcome: going home
Most children recover completely from STEC HUS over several weeks. How long your child stays in hospital will depend on the symptoms, how they respond to treatment and how quickly their kidney function improves.