#116: Hemolytic Uremic Syndrome

July 31, 2024 | By Sam Masur

Audio

Summary:

In this episode, pediatric nephrologist Dr. Myda Khalid (Indiana) teaches us about hemolytic uremic syndrome.  Join us as we learn about the clinical manifestations of HUS, different methods for stool testing, and the role of interventions including fluids, transfusions, and renal replacement therapy.

Hemolytic Uremic Syndrome Pearls

1. HUS is defined by the triad of hemolytic anemia, thrombocytopenia, and acute kidney injury.
2. Clinicians should have a high index of suspicion for shiga toxin-associated HUS in patients who present with acute diarrhea that turns bloody,  particularly during the summer months in children less than 5 years of age.
3. Stool testing can be done with a rectal swab if patients are unable to provide a stool sample during evaluation.
4. Due to the risk of bowel ischemia and perforation, it is important to follow serial abdominal exams and have a low threshold for abdominal imaging.
5. There is no definitive treatment for HUS. Supportive care includes intravenous fluids, blood transfusions, and renal replacement therapy.

Hemolytic Uremic Syndrome Notes

In this episode, we focus on hemolytic uremic syndrome (HUS) caused by shiga-toxin producing E. Coli (STEC).  Patients can get sick following exposure to contaminated food, water, and soil. Shiga toxin damages endothelial cells in small blood vessels, leading to clotting and formation of microthrombi. Approximately 15% of children infected with STEC will go on to develop HUS around 3-5 days after onset of diarrhea. 

Other causes of HUS include Streptococcus pneumoniae infection, HIV, medications (ex. tacrolimus, chemotherapy), and atypical HUS related to overactive complement.

Clinical Manifestations

Gastrointestinal

Acute onset of bloody diarrhea is the most common presentation of HUS. Patients are at risk of bowel ischemia and perforation, so serial abdominal exams are important. Pancreatitis can also be seen with associated elevations in amylase and lipase.

Renal

Acute kidney injury is seen in 60% of children with HUS. Patients may develop edema, decreased urine output, and elevated blood pressures.

Neurological

Severity can range from altered mental status, headache, irritability, and sleepiness to seizures. 

Diagnostic Workup

• Stool culture or stool pathogen panel
• Complete blood count
• Basic metabolic panel specifically looking at Cr, BUN
• Albumin
• Haptoglobin and LDH to evaluate for hemolysis
• Amylase and lipase if there is concern for pancreatitis
• Urinalysis if possible…but Dr. Khalid recommends not pushing for a catheterization due to risk of seeding bacteria from diarrhea
• Low threshold to obtain abdominal x-ray if there is concern for bowel perforation

Management

Intravenous Fluids

There is limited data suggesting that aggressive early hydration with intravenous fluids may reduce the incidence and severity of HUS. In Dr. Khalid’s expert opinion, because HUS patients are already volume down from diarrhea and vomiting, providing fluids can prevent them from taking additional insults to the kidney due to intravascular depletion.

Transfusions

Many children will require ongoing red blood cell transfusions due to hemolytic anemia (Dr. Khalid uses a cutoff of Hgb <7). In her expert opinion, patients with HUS often do NOT require platelet transfusions unless they are actively bleeding because the platelets they do have are functioning normally.

Renal Replacement Therapy

The decision to use peritoneal dialysis, hemodialysis, or CVVH is institution-dependent. Peritoneal dialysis should be avoided if there is any concern for bowel ischemia or perforation.

Antibiotics

Should be avoided in STEC infections as there is data suggesting that they can increase the risk of developing HUS.

Eculizumab

Used in some centers when patients develop severe neurologic complications, but definitive evidence to support its use is lacking.

Plasma Exchange Therapy

No clear benefit in STEC-HUS (unlike with its use in adults diagnosed with TTP).

Prognosis

The mortality rate of HUS is 3-5%. Most children who require dialysis will be on for 1-2 weeks before renal recovery. Those who require dialysis for longer (>3 weeks) may be at higher risk for development of chronic kidney disease.

Goal

Listeners will explain the basic pathophysiology, diagnosis, and management of hemolytic uremic syndrome.

Learning Objectives

After listening to this episode listeners will…  

1. Identify the role of shiga-toxin producing E. Coli in the development of HUS.
2. Describe the clinical manifestations of HUS.
3. Discuss the use of intravenous fluids, blood transfusions, and renal replacement therapy in management of HUS.

Disclosures

Dr. Khalid reports no relevant financial disclosures. The Cribsiders report no relevant financial disclosures. 

Citation

Mao C, Khalid M, Masur S, Chiu C, Berk J. “#116:  Hemolytic Uremic Syndrome”. The Cribsiders Pediatric Podcast. https:/www.thecribsiders.com/ July 31, 2024.