By: Ryan Robinson, PhD
Hemolytic Uremic Syndrome (HUS) is a dangerous, and sometimes fatal disease characterized by anemia, low platelet count, and renal distress. HUS is commonly the result of infection by a specific class of foodborne pathogenic E. coli strains known as STEC or Shiga-toxin producing E. coli.
In the case of HUS caused by foodborne illness, the initial, acute effects of HUS (anemia, renal dysfunction, and reduced platelet count) usually follow the traditional, well-known symptoms associated with foodborne illnesses (nausea, diarrhea, fever, vomiting).
Acute effects of HUS are profoundly dangerous, particularly for high risk populations like children or the elderly. When prompt, appropriate medical intervention is available, the immediate mortality rate for HUS is between 5 and 10%.
Unfortunately, the acute effects of HUS are not the only concern. In some cases, long-term damage to the kidneys and other organs can result in persistent or recurrent health concerns that can have a drastic effect on a patient for the remainder of their life.
What causes Hemolytic Uremic Syndrome?
The most common form of hemolytic uremic syndrome is initiated by bacterial infection, and is often associated with foodborne illness. Some bacterial pathogens produce dangerous, virulent toxic compounds. During an infection, these toxic compounds can enter the bloodstream and may damage or kill red blood cells (erythrocytes) and platelets (thrombocytes).
The destruction of red-blood cells (which carry oxygen from the lungs vital organs) and platelets (which assist with blood clotting and wound-healing) is certainly troublesome enough; the scale at which they are destroyed by invading bacterial toxins complicates matters further.
One might recall that the kidneys play a vital role in human physiology: filtering debris, waste, and dangerous chemical compounds out of the bloodstream. Just as a water filter takes murky creek-runoff and produces clear, potable water, the kidneys take all of the cellular and chemical detritus from the bloodstream and release clean, filtered blood safe for other organs. Of course, even the best filters are rendered inoperable by improper use.
During extended periods of cellular death, like those triggered by bacterial toxins during HUS, the natural systems that break-down and recycle dead and dying cells are overwhelmed. As a result, dead cells and cellular waste accumulate and clog the narrow pathways like those inside the kidney in the same way that thick, heavy mud might clog a water filter.
Like a clogged water-filter, clogged kidneys are temporarily unable to perform their normal function. Unfiltered blood continues to course to vital organs, carrying cellular debris, chemical compounds, and dangerous waste products that would normally be filtered out by the kidneys and passed out of the body as urine.
Without medical intervention, the result can be catastrophic. Extended periods of kidney dysfunction will result in the brain, heart, lungs and other vital organs being bathed in dangerous chemical compounds and all manner of cellular detritus. The inevitable result being critical organ damage and eventual death.
How is HUS treated?
There is no simple cure for HUS. Even treating the root-cause for most cases (bacterial infection) can produce counterintuitive results. Administration of antibiotics to treat bacterial illness can actually increase the likelihood that an infection will result in hemolytic uremic syndrome.
When HUS does develop, not all cases result in complete kidney dysfunction. Often, even in the wake of massive cellular death prompted by an onslaught of bacterial toxins a patient’s own body may retain an acceptable level of kidney function. In these cases, supportive treatment like ensuring proper hydration, and careful observation in a hospital setting is the most common course of treatment.
Thankfully, even in the most severe cases where kidney function is impaired, modern medical technology allows us to approximate and mimic the function of the kidney for a limited amount of time.
A 2014 study indicated that between half and three quarters of childhood HUS cases required dialysis or a similar renal replacement therapies. Undoubtedly, it is these cases that have resulted in reduction of mortality rates associated with HUS to the historically low levels where they currently reside.
What are the long-term effects of HUS?
While mortality rates for HUS are historically low, kidney dysfunction and damage should never be taken lightly. The study referenced above, and other long term studies [1, 2] indicate that nearly one-third of HUS patients suffer long term (sometimes permanent) kidney damage. In some instances, these individuals will require regular kidney dialysis for the remainder of their life.
In addition to kidney damage, some research indicates that STEC-HUS (the form of HUS caused by Shiga toxin producing strains of E. coli) may result in brain damage, and damage to other components of the central nervous system.
The advanced, sometimes seemingly miraculous nature of modern medicine, may have allowed developed nations to reduce the mortality rate associated with HUS substantially. While this is undoubtedly a positive development, we should not and cannot permit it to lull us into a false sense of security.
If nothing else, the severe and acute illness associated with HUS is undoubtedly a traumatic experience for the vast majority of patients that survive it. For some, the alterations to their life are of a more significant and permanent nature. Lifelong medical intervention in the form of dialysis and/or kidney transplant may be necessary for some unlucky HUS patients. Some individuals may even suffer permanent to the brain or to other organs.
Unfortunately, as is so often the case, those who suffer most from this debilitating disease are those most as risk, and arguably those with the most to sacrifice. Those most seriously affected by this dangerous disease are those most at risk among us, and arguably those with the most quality of life to lose. HUS is the primary cause of kidney failure in children under the age of four.
When we observe that the proximate cause for most cases of HUS is foodborne illness, something that should ostensibly be so simply preventable, it becomes immediately evident that in this case an ounce of prevention may be worth much more than a pound of “cure”.