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Complications of E. coli infection

Hemolytic Uremic Syndrome – A Life-Threatening Complication of Infection with E. coli O157:H7 and other Shiga toxin-producing E. coli (STEC)

E. coli O157:H7 and other STEC infections can lead to a severe, life-threatening complication called hemolytic uremic syndrome (HUS). HUS is characterized by three primary conditions: 1) microangiopathic hemolytic anemia (i.e., low red blood cell counts); 2) thrombocytopenia (i.e., low platelet counts); and, 3) kidney failure. E. coli O157:H7 is the most common cause of post-diarrheal HUS in the United States, accounting for at least two-thirds of cases and likely approaching 90% of cases. HUS is the most common cause of acute (sudden) kidney failure in children in the United States.

HUS accounts for a substantial portion of the acute deaths and the majority of long-term health effects caused by O157. HUS occurs in about 5-6% of those with laboratory-confirmed E. coli O157:H7 infections overall, but the risk differs by age. As many as 15% of children <5 years of age with E. coli O157:H7 infections develop HUS, as do about 8% of children 5 to 9 years of age, 3% of children from 10-17 years of age, 1% of adults 18-59 years of age, and 4% in adults >60 years of age.

HUS not only involves kidney disease; other organs can be affected as well. The central nervous system is affected in 30-60% of cases; this can result in seizures, coma, and stroke, and can be life threatening. Serious injury to the pancreas and other organs can also occur.

Organ systems that can be affected by HUS

There is no specific cure or treatment for HUS, so it is managed with supportive care. More than half of people with HUS require dialysis because of kidney failure, and blood (red cell) transfusions are required in over 90% of cases because of anemia and/or low platelet counts.

Overall, 5% of HUS cases are fatal. In children, about 3% of HUS cases are fatal. HUS is much less common in people >65 years of age, but when it does occur the fatality rates are much higher – 30% overall and 40-50% for cases >75 years of age.

For those who survive HUS, many have long-term health effects. Up to 25% of HUS cases develop long-term kidney problems, which can include end stage renal disease (ESRD) and the need for long-term dialysis or a kidney transplant later in life. Other long-term problems include an elevated risk for hypertension.

HUS typically begins around 7 days after onset of diarrhea due to E. coli O157:H7 but can begin as soon as 2 days and up to 2 weeks (rarely up to 3 weeks) after onset, often as diarrhea is improving or has completely stopped. HUS is more likely to occur in people who have severe bloody diarrhea but can occur after milder diarrheal illness as well. People with HUS usually have a sudden onset of pallor (paleness) due to anemia, little to no urine output, nausea and vomiting, edema (swelling due to fluid accumulation under the skin), and sometimes, neurologic symptoms varying from mild jerks to coma or stroke. If any of these signs or symptoms appear after having a diarrheal illness, it is critical to seek health care immediately. Blood work will typically indicate multiple abnormalities and involvement, or decreased function of multiple organs.

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Other Complications from E. coli O157:H7 Infection

Kidney disease from HUS is not the only complication that can be caused by O157 infection. Long-term deficits to the gastrointestinal tract, brain, liver, heart, adrenal glands, spleen, and pancreas can occur. Specific long-term consequences can include hypertension (high blood pressure), cardiovascular disease, diabetes, central nervous system dysfunction, and reactive arthritis, among others. Chronic hypertension, related to kidney damage, occurs in 8-12% of children who survive HUS. Diabetes occurs in an estimated 3% (up to 15% in some studies) of HUS cases.

In some E. coli O157:H7 cases, colon damage is so severe, including perforation, that the colon must be removed; this can occur with or without HUS. Several other types of long-term intestinal problems can also occur, and some can require surgery years after initial illness. One specific potential complication is Irritable Bowel Syndrome, or IBS, a chronic disorder characterized by abdominal discomfort and altered bowel habits, including diarrhea and/or constipation. Severe neurologic involvement during acute illness increases the likelihood of long-term central nervous system dysfunction, which can include manifestations such as seizures.