Hemolytic Uremic Syndrome (HUS)

Alternative names:  Haemolytic-uraemic syndrome, HUS

Definition:
Hemolytic uremic syndrome, or HUS, is a kidney condition that happens when red blood cells are destroyed and block the kidneys‘ filtering system. Red blood cells contain hemoglobin—an iron-rich protein that gives blood its red color and carries oxygen from the lungs to all parts of the body.

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When the kidneys and glomeruli—the tiny units within the kidneys where blood is filtered—become clogged with the damaged red blood cells, they are unable to do their jobs. If the kidneys stop functioning, a child can develop acute kidney injury—the sudden and temporary loss of kidney function. Hemolytic uremic syndrome is the most common cause of acute kidney injury in children.

It is a disease characterized by hemolytic anemia (anemia caused by destruction of red blood cells), acute kidney failure (uremia), and a low platelet count (thrombocytopenia). It predominantly, but not exclusively, affects children. Most cases are preceded by an episode of infectious, sometimes bloody, diarrhea acquired as a foodborne illness or from a contaminated water supply and caused by E. coli O157:H7, although Shigella, Campylobacter and a variety of viruses have also been implicated. It is now the most common cause of acquired acute renal failure in childhood. It is a medical emergency and carries a 5–10% mortality; of the remainder, the majority recover without major consequences but a small proportion develop chronic kidney disease and become reliant on renal replacement therapy.

The kidneys are two bean-shaped organs, each about the size of a fist. They are located just below the rib cage, one on each side of the spine. Every day, the two kidneys filter about 120 to 150 quarts of blood to produce about 1 to 2 quarts of urine, composed of wastes and extra fluid. Children produce less urine than adults and the amount produced depends on their age. The urine flows from the kidneys to the bladder through tubes called ureters. The bladder stores urine. When the bladder empties, urine flows out of the body through a tube called the urethra, located at the bottom of the bladder.

Symptoms:
STEC-HUS occurs after ingestion of a strain of bacteria, usually types of E. coli, that expresses verotoxin (also called Shiga-like toxin). Bloody diarrhea typically follows. HUS develops about 5–10 days after onset of diarrhea, with decreased urine output (oliguria), blood in the urine (hematuria), kidney failure, thrombocytopenia (low levels of platelets) and destruction of red blood cells (microangiopathic hemolytic anemia). Hypertension is common. In some cases, there are prominent neurologic changes.

A child with hemolytic uremic syndrome may develop signs and symptoms similar to those seen with gastroenteritis—an inflammation of the lining of the stomach, small intestine, and large intestine—such as

*vomiting
*bloody diarrhea
*abdominal pain
*fever and chills
*headache

As the infection progresses, the toxins released in the intestine begin to destroy red blood cells. When the red blood cells are destroyed, the child may experience the signs and symptoms of anemia—a condition in which red blood cells are fewer or smaller than normal, which prevents the body’s cells from getting enough oxygen.

Signs and symptoms of anemia may include:-

*fatigue, or feeling tired
*weakness
*fainting
*paleness

As the damaged red blood cells clog the glomeruli, the kidneys may become damaged and make less urine. When damaged, the kidneys work harder to remove wastes and extra fluid from the blood, sometimes leading to acute kidney injury.

Other signs and symptoms of hemolytic uremic syndrome may include bruising and seizures.

When hemolytic uremic syndrome causes acute kidney injury, a child may have the following signs and symptoms:

*edema—swelling, most often in the legs, feet, or ankles and less often in the hands or face
*albuminuria—when a child’s urine has high levels of albumin, the main protein in the blood
*decreased urine output
*hypoalbuminemia—when a child’s blood has low levels of albumin
*blood in the urine

Causes:
A number of things can cause hemolytic uremic syndrome, but the most common cause — particularly in children — is an infection with a specific strain of E. coli, usually the strain known as O157:H7. However, other strains of E. coli have been linked to hemolytic uremic syndrome, too.

Normally, harmless strains, or types, of E. coli are found in the intestines and are an important part of digestion. However, if a child becomes infected with the O157:H7 strain of E. coli, the bacteria will lodge in the digestive tract and produce toxins that can enter the bloodstream. The toxins travel through the bloodstream and can destroy the red blood cells. E. coli O157:H7 can be found in:

*Contaminated meat or produce
*Swimming pools or lakes contaminated with feces
*undercooked meat, most often ground beef
*unpasteurized, or raw, milk
*unwashed, contaminated raw fruits and vegetables
*contaminated juice

Less common causes, sometimes called atypical hemolytic uremic syndrome, can include:-

*taking certain medications, such as chemotherapy
*having other viral or bacterial infections
*inheriting a certain type of hemolytic uremicsyndrome that runs in families

Children who are more likely to develop hemolytic uremic syndrome include those who
are younger than age 5 and have been diagnosedwith an E. coli O157:H7 infection

*have a weakened immune system
*have a family history of inherited hemolyticuremic syndrome
*Hemolytic uremic syndrome occurs in about two out of every 100,000 children.

Most people who are infected with E. coli, even the more dangerous strains, won’t develop hemolytic uremic syndrome. It’s also possible for hemolytic uremic syndrome to follow infection with other types of bacteria.

In adults, hemolytic uremic syndrome is more commonly caused by other factors, including:

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*The use of certain medications, such as quinine (an over-the-counter muscle cramp remedy), some chemotherapy drugs, the immunosuppressant medication cyclosporine (Neoral, Sandimmune) and anti-platelet medications

*Pregnancy

*Certain infections, such as HIV/AIDS or an infection with the pneumococcal bacteria

*Genes, which can be a factor because a certain type of HUS — atypical hemolytic uremic syndrome — may be passed down from your parents

The cause of hemolytic uremic syndrome in adults is often unknown

Diagnosis:
The Doctor diagnoses hemolytic uremic syndrome with

*a medical and family history
*a physical exam
*urine tests
*a blood test
*a stool test
*kidney biopsy

The similarities between HUS, aHUS, and TTP make differential diagnosis essential. All three of these systemic TMA-causing diseases are characterized by thrombocytopenia and microangiopathic hemolysis, plus one or more of the following: neurological symptoms (e.g., confusion, cerebral convulsions, seizures); renal impairment (e.g., elevated creatinine, decreased estimated glomerular filtration rate [eGFR], abnormal urinalysis ); and gastrointestinal (GI) symptoms (e.g., diarrhea, nausea/vomiting, abdominal pain, gastroenteritis).The presence of diarrhea does not exclude aHUS as the etiology of TMA, as 28% of patients with aHUS present with diarrhea and/or gastroenteritis. First diagnosis of aHUS is often made in the context of an initial, complement-triggering infection, and Shiga-toxin has also been implicated as a trigger that identifies patients with aHUS. Additionally, in one study, mutations of genes encoding several complement regulatory proteins were detected in 8 of 36 (22%) patients diagnosed with STEC-HUS. However, the absence of an identified complement regulatory gene mutation does not preclude aHUS as the etiology of the TMA, as approximately 50% of patients with aHUS lack an identifiable mutation in complement regulatory genes.

Diagnostic work-up supports the differential diagnosis of TMA-causing diseases. A positive Shiga-toxin/EHEC test confirms an etiological cause for STEC-HUS, and severe ADAMTS13 deficiency (i.e., ?5% of normal ADAMTS13 levels) confirms a diagnosis of TTP

Complications:
Most children who develop hemolytic uremic syndrome and its complications recover without permanent damage to their health.1
However, children with hemolytic uremic syndrome may have serious and sometimes life-threatening complications, including

*acute kidney injury
*high blood pressure
*blood-clotting problems that can lead to bleeding
*seizures
*heart problems
*chronic, or long lasting, kidney disease
*stroke
*coma

Treatment:
The Doctor will treat a child’s urgent symptoms and try to prevent complications by

*observing the child closely in the hospital
*replacing minerals, such as potassium and salt, and fluids through an intravenous (IV) tube
*giving the child red blood cells and platelets—cells in the blood that help with clotting—through an IV
*giving the child IV nutrition
*treating high blood pressure with medications

Treating Acute Kidney Injury:
If necessary,the Doctor will treat acute kidney injury with dialysis—the process of filtering wastes and extra fluid from the body with an artificial kidney. The two forms of dialysis are hemodialysis and peritoneal dialysis. Most children with acute kidney injury need dialysis for a short time only.

Treating Chronic Kidney Disease:
Some children may sustain significant kidney damage that slowly develops into CKD. Children who develop CKD must receive treatment to replace the work the kidneys do. The two types of treatment are dialysis and transplantation.

In most cases, The Doctor treat CKD with a kidney transplant. A kidney transplant is surgery to place a healthy kidney from someone who has just died or a living donor, most often a family member, into a person’s body to take over the job of the failing kidney. Though some children receive a kidney transplant before their kidneys fail completely, many children begin with dialysis to stay healthy until they can have a transplant. click to know more

Prevention:

Hemolytic uremic syndrome, or HUS, is a kidney condition that happens when red blood cells are destroyed and block the kidneys’ filtering system.
The most common cause of hemolytic uremic syndrome in children is an Escherichia coli (E. coli) infection of the digestive system.
Normally, harmless strains, or types, of E. coli are found in the intestines and are an important part of digestion. However, if a child becomes infected with the O157:H7 strain of E. coli, the bacteria will lodge in the digestive tract and produce toxins that can enter the bloodstream.
A child with hemolytic uremic syndrome may develop signs and symptoms similar to those seen with gastroenteritis, an inflammation of the lining of the stomach, small intestine, and large intestine.

Most children who develop hemolytic uremic syndrome and its complications recover without permanent damage to their health.
Some children may sustain significant kidney damage that slowly develops into chronic kidney disease (CKD).

Parents and caregivers can help prevent childhood hemolytic uremic syndrome due to E. coli O157:H7 by

*avoiding unclean swimming areas
*avoiding unpasteurized milk, juice, and cider
*cleaning utensils and food surfaces often
*cooking meat to an internal temperature of at least 160° F
*defrosting meat in the microwave or refrigerator
*keeping children out of pools if they have had diarrhea
*keeping raw foods separate
*washing hands before eating
*washing hands well after using the restroom and after changing diapers

When a child is taking medications that may cause hemolytic uremic syndrome, it is important that the parent or caretaker watch for symptoms and report any changes in the child’s condition to the Doctor as soon as possible.

Prognosis:
Acute renal failure occurs in 55-70% of patients with STEC-HUS, although up to 70-85% recover renal function. Patients with aHUS generally have poor outcomes, with up to 50% progressing to ESRD or irreversible brain damage; as many as 25% die during the acute phase. However, with aggressive treatment, more than 90% of patients survive the acute phase of HUS, and only about 9% may develop ESRD. Roughly one-third of persons with HUS have abnormal kidney function many years later, and a few require long-term dialysis. Another 8% of persons with HUS have other lifelong complications, such as high blood pressure, seizures, blindness, paralysis, and the effects of having part of their colon removed. The overall mortality rate from HUS is 5-15%. Children and the elderly have a worse prognosis.

Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose.

Resources:
http://kidney.niddk.nih.gov/KUDiseases/pubs/childkidneydiseases/hemolytic_uremic_syndrome/
http://en.wikipedia.org/wiki/Hemolytic-uremic_syndrome
http://www.mayoclinic.org/diseases-conditions/hemolytic-uremic-syndrome/basics/causes/con-20029487

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