What are the expected short and long-term outcomes for patients with Hemolytic Uremic Syndrome?
The natural history (clinical course) of HUS has improved remarkably with the advent of dialysis and intensive care facilities for children. In the 1950s, there was a 40% death rate with HUS; now, in developed countries, the mortality rate is 2-4%.
Patients today very rarely die directly from the acute renal failure associated with HUS. When death occurs, it is almost always related to an inability to prevent, recognize, and effectively treat life-threatening extra-renal organ involvement. Although brain injury is the most common cause of death from HUS, severe multi-organ damage (renal cortical necrosis, bowel necrosis, and stroke) is a common postmortem finding at autopsy.
Although those surviving HUS usually escape immediate serious complications, about 3-5% are left with long-term damage to organs other than the kidneys, especially to the pancreas or brain. An equal number are left with severe kidney damage and, thus, require chronic dialysis and kidney transplant within a few years.
A larger number of HUS patients will go on to develop future health disorders related to acute kidney injury, including hypertension, proteinuria, and low glomerular filtration rate (GFR). The risk appears to be associated with the duration of oliguria or anuria during the acute phase of HUS. However, one or more of these complications, albeit usually mild, have been seen in about a third of those with no observed decrease in urinary output. Among children whose oliguria lasted more than 10 days, 63.3% had a low GFR, 33.3% developed hypertension, and 88.7% experienced at least one long-term complication. Among children with more than 10 days of anuria, 66.7% became proteinuric, 77.8% had a low GFR, 55.6% developed hypertension, and 100% experienced at least one of these disorders. A particularly high incidence of hypertension (55.6%) has been seen in patients with greater than 10 days of anuria compared to 8.9% in those with no history of anuria.
There are data supporting the supposition that children with a “full” renal recovery have ongoing detectable manifestations of renal disease. Glomerular hyperfiltration (increased GFR) may occur after HUS, initially manifesting as microalbuminuria (albumin in the urine) and later as overt proteinuria.
It is difficult to predict the lifetime risk of end-stage kidney disease (ESKD); however, care can be preventive. At-risk patients require evaluation several times during the first year post-HUS, then at regular intervals for life. Some recommend yearly evaluations for ten years after the first year of recovery from HUS, then every two years for the next 20 years, and more frequently if abnormalities are found. This would include close scrutiny of blood pressures, as well as lab tests for serum-creatinine, urinary protein, and microalbuminuria. Special attention must be given to women of childbearing age, since there may be an increased risk of “toxemia” (pre-eclampsia and eclampsia) of pregnancy.