Hemolytic Uremic Syndrome in Pediatric Patients
Case:
An 8-year-old healthy male presents with non-bloody vomiting, diarrhea, abdominal pain, fatigue and subjective fevers for the last 4 days. Mom notices patient’s stools have become bloody, and his urine has become dark. No one else at home is sick. Patient’s diet consists mostly of cereal, chicken nuggets, cheese burgers, and peanut butter and jelly sandwiches. He drinks milk and juice. They occasionally eat at restaurants but not recently. He has never had any abdominal surgeries or history of hospitalizations. She is worried he is not getting any better and he is not eating or drinking.
Vitals:
HR: 150 BP: 96/61, RR: 16, T: 100.1 F, SpO2: 97% on room air
Physical exam:
General: Ill-appearing male in mild distress
HEENT: Dry mucous membranes
Cardiovascular: RRR, no murmurs or gallops, pulses 2+
Pulmonary: Breath sounds clear to auscultation bilaterally
Abdomen: Diffusely tender to palpation, no rebound or guarding, moderately distended
GU: Normal male exam for stated age
Skin: Pale, warm, dry
Notable labs:
WBC: 16.2 109/L
Hgb: 8.1 g/L
Plt: 64 109/L
Na: 137 mEq/L
K: 4.3 mEq/L
Cl: 100 mEq/L
CO2: 20 mEq/L
BUN: 37 mg/dL
Cr: 1.7 mg/dL
Glucose: 112 mg/dL
Lactate: 2.4 mmol/L
LFTS and lipase are normal
Occult stool: positive
UA: 3+ blood and 3+ protein
Stool PCR: Positive for shiga toxin 2
Imaging:
Abdominal US: Appendix intact without evidence of inflammation, no intussusception or volvulus
Chest x-ray: No cardiopulmonary abnormalities
Diagnosis:
Clinical presentation and labs concerning for Shiga toxin-producing Escherichia coli (STEC) with early signs of Hemolytic Uremic Syndrome
Discussion:
Shiga toxin-producing Escherichia Coli (STEC) is the most common cause of hemolytic uremic syndrome in children (HUS) [1]. Shiga toxins cause thrombotic microangiopathy leading to the disease. The serotype O157:H7 is the predominant bacterial cause of pediatric HUS, accounting for approximately 90% of cases [2]. STEC is usually transmitted through undercooked meat and contaminated milk and vegetables. It can also be transmitted person to person [3]. Approximately 15% of children diagnosed with STEC go on to develop HUS [4].
STEC-HUS typically affects children under 10. The typical clinical course of this disease starts with prodromal abdominal pain, nausea and vomiting that is usually bloody but may start nonbloody [1]. After 5-10 days, HUS develops with onset of microangiopathic hemolytic anemia. These fragmented red blood cells are called schistocytes (figure 1) and are non-immune mediated (negative Coombs’ test). This is due to the toxin activating thrombogenic effects on endothelial cells leading to microvascular thrombus formation, as well as activation of complement proteins and thrombus formation. This ultimately causes the clinical triad of HUS: microangiopathic hemolytic anemia, thrombocytopenia and acute kidney injury. Other symptoms include hypertension and CNS manifestations. STEC is best diagnosed with PCR tests for shiga toxin as well as stool cultures [4].
The treatment for STEC-HUS is mainly supportive. Antibiotics and antimotility agents are contraindicated as studies have shown antibiotic use STEC increases risk of HUS. The mainstays of treatment include aggressive IV fluid hydration, transfusions of packed red blood cells and platelets as needed, and dialysis for acute renal failure. Calcium channel blockers can be used for hypertension [5]. The hemolytic manifestations of STEC-HUS generally resolve within 1-2 weeks. The prognosis for kidney function is favorable however approximately one-third of patients develop mild kidney dysfunction in long term follow up. The mortality rate is less than 5 percent [6].
Case resolution:
The patient was admitted to the PICU. He required several transfusions of packed red blood cells and platelets. He became progressively more confused and hypertensive. On day 7 of admission, he was initiated on peritoneal dialysis due to severe kidney dysfunction. His kidney function improved with continuous IV fluids and he was taken off dialysis. He was ultimately discharged with no acute complications and will follow up with his pediatrician for long term blood pressure and kidney function monitoring.
Takeaway points:
STEC typically manifests in younger children with abdominal pain and bloody diarrhea.
HUS develops 5-10 days after initial symptoms.
The clinical triad of HUS includes microangiopathic hemolytic anemia, thrombocytopenia and acute kidney injury.
Treatment for STEC-HUS is supportive. Antibiotics are contraindicated and increase risk of complications.
Author: Jordan Ozolin, MD is a second-year resident at Brown University/Rhode Island Hospital
Faculty Reviewer: Kristina McAteer, MD, is an attending emergency medicine physician at Rhode Island Hospital and Newport Hospital.
References
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