Today I reviewed my blog post resources on Hemolytic Uremic Syndrome and added some additional resources on the topic.
I like to start a pediatrics subject review with the relevant PedsCases podcast and transcript if they are available on a topic.
So first I listened again to Hemolytic Uremic Syndrome (HUS) podcast
by Magdalena Riedl Aug 09, 2019 and reread the excellent transcript:
Etyology and pathophysiology:
Hemolytic uremic syndrome is characterized – as the name implies – by non-immune hemolytic anemia, thrombocytopenia and renal failure. In childhood (especially in children < 10 years of age) the majority of HUS cases are caused by an infection with enterohemorrhagic E.coli that produces Shiga toxin and is
often referred to as EHEC/STEC HUS.The underlying pathophysiology is endothelial cell injury and damage of small vessels, especially in the kidney. But other organs such as the CNS, liver, pancreas, lung and heart can be involved. This endothelial damage causes platelet activation and formation of thrombi. Thrombocytopenia occurs due to consumption of platelets within these clots. Hemolytic anemia occurs due to mechanical breakdown of the RBCs when they try to pass through those thrombi. Therefore hemolytic anemia is Coombs negative, as it doesn’t involve autoantibodies. Uremia or renal failure occurs as clots occlude the small vessels within the kidney and lead to decreased kidney function.
Very rarely, HUS in childhood can also be caused by other infections such as Streptococcus pneumoniae or influenza. These children present with pneumonia or sepsis, in addition to signs and symptoms of HUS. This is believed to be caused by neuraminidase shedding parts of the glycocalyx and therefore exposing the Thomsen Friedenreich antigen on blood and endothelial cells. Preformed host IgM will bind and initiate the cascade leading to HUS.
Diagnosis
HUS is a clinical diagnosis including the history of diarrhea and if available, exposure to life-stock or raw/undercooked meat and lab work that shows the triad of hemolytic anemia, thrombocytopenia and impairment of renal function.
Hemolytic anemia is characterized by low hemoglobin, elevated LDH – released from damaged red blood cells, low or undetectable haptoglobin as it will bind to all the released NO from damaged RBCs and schistocytes on peripheral blood smear. As the hemolytic anemia is non-immune mediated – with the exception of pneumococcal HUS – Coombs test is negative. Often patients have an increased WBC count due to high
neutrophil counts. Impaired renal function can be detected by increase in creatinine and urea or decrease of urine output.Hemolytic anemia is characterized by low hemoglobin, elevated LDH – released from damaged red blood cells, low or undetectable haptoglobin as it will bind to all the released NO from damaged RBCs and schistocytes on peripheral blood smear. As the hemolytic anemia is non-immune mediated – with the exception of pneumococcal HUS – Coombs test is negative. Often patients have an increased WBC count due to high
neutrophil counts. Impaired renal function can be detected by increase in creatinine and urea or decrease of urine output.Kidney injury can lead to electrolyte disturbances such
as hyperkalemia, hyperphosphatemia, hypocalcemia and hyponatremia, as well as acidbase imbalances, elevated BP and proteinuria/hematuria. You should also confirm the
presence of Shigatoxin by sending stool samples for detection of EHEC and Shigatoxin.[Treatment Of HUS]
Unfortunately there is no specific treatment for STEC HUS except for supportive measures. If hemodynamically unstable or if significantly anemic the patient should receive a RBC transfusion. Platelet transfusions should not be given routinely, unless the patient is actively bleeding or if a surgical intervention (ie peritoneal dialysis catheter insertion) is required. Supportive measures for renal impairment include fluid and dietary restriction (potassium and/or phosphate), treatment of hypertension and if needed treatment of potentially life-threatening electrolyte disorders (ie hyperkalaemia).
Monitoring of fluid inputs and outputs is critical to avoid fluid overload. Despite maximal supportive medical treatment, short-term dialysis may be needed in up to 2/3 of patients. The overall prognosis is good for patients with STEC HUS – usually with recovery of their renal function and no recurrence of the disease. However, patients are at risk of developing proteinuria, hypertension and chronic kidney disease over the longterm, thus necessitating follow up monitoring of blood pressure, urine for protein and kidney function.Review:
1. HUS is an uncommon disease, and typically presents with the triad of: hemolytic anemia, thrombocytopenia and renal failure.
2. In children it is mainly caused by Shigatoxin which is referred to as STEC HUS.
3. There is no specific treatment for STEC HUS, except for supportive medical
measures including meticulous fluid management, acute medical management of electrolyte/acid-base abnormalities and dialysis as indicated.
4. Overall prognosis of STEC HUS is good, however affected children may have increased risk of developing proteinuria, hypertension and CKD, thus requiring longterm follow up.
5. In rare instances, patients have atypical HUS, a recurrent form, which is associated with genetic defects in the complement system, leading to overactivation of the complement system. The prognosis of this disease has improved in the last decade with
eculizumab, a monoclonal antibody that blocks the complement system.
The differential diagnosis for Hemolytic Uremic Syndrome is:*
*Pediatric Hemolytic Uremic Syndrome Differential Diagnoses
Updated: Jun 13, 2016 from emedicine.medscape.com
Differential Diagnoses
And finally I reviewed Hemolytic Uremic Syndrome By Dr. Larry Mellick
Posted on July 28, 2015 by Tom Wade MD. The post embeds Dr. Mellick’s excellent YouTube video and contains slide excerpts from the video.
