Updated: 3/11/2018

Hemolytic Uremic Syndrome (HUS)

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Snapshot
  • A 7-year-old boy recently had several episodes of bloody diarrhea. Desperate, his parents called his primary care physician, who reassured them that the infection is self-limited. Still concerned, his parents bought some diarrhea pills (anti-motility agents). A week later, he presents to the ER with jaundice, abdominal pain, and easy bruising. Lab results come back with low platelet count, anemia, and increased creatinine. A peripheral blood shows schistocytes. He is started on IV hydration.
Introduction
  • Syndrome commonly seen in children
    • most commonly caused by Escherichia coli O157:H7 (EHEC)  
      • acute diarrhea
      • due to Shiga-like toxin
    • S. pneumoniae infection
    • Shigella spp.
      • Shiga toxin
  • Classic triad
    • thrombocytopenia (first)
    • nonimmune microangiopathic hemolytic anemia (second)
    • acute renal failure (hence, “uremia” in title) (third)
  • Similar to TTP but without fever and neurologic symptoms
  • Pathogenesis
    • toxin damages endothelium
    • microthrombi form at site of damage
      • consumes platelets → thrombocytopenia
      • intravascular mechanical hemolysis → schistocytes
      • decreases renal blood flow → acute renal failure
  • Epidemiology
    • most commonly in children
    • exposed to E. coli
      • raw or undercooked meat
      • unwashed fruits/vegetables
      • animals at petting zoos
  • Risk factors
    • use of antimotility agents in EHEC diarrhea
    • use of antibiotics in EHEC diarrhea
Presentation
  • Symptoms
    • prodromal gastrointestinal illness
    • abdominal pain
    • bloody diarrhea
    • nausea
    • vomiting
    • fatigue (anemia)
    • oliguria/anuria (renal failure)
  • Physical exam
    • pallor (anemia)
    • jaundice (hemolysis)
    • petechiae/purpura uncommon
    • hepatosplenomegaly
Evaluation
  • Criteria for HUS
    • hemolytic anemia
      • hematocrit < 30%
      • schistocytes (helmet cells) on peripheral smear
    • thrombocytopenia 
    • ↑ serum creatinine
  • Normal PT/PTT
  • Negative Coombs test
  • ↑ bleeding time
Differential

 

Characteristics
DIC
ITP
TTP
HUS
Fever
  • No
  • No
  • Yes
  • Yes/No
Splenomegaly
  • No
  • No
  • Yes
  • Yes
Platelets
  • Low
  • Low
  • Low
  • Low
Bleeding time
PT
-
-
-
PTT
-
-
-
Shistocytes
  • Yes
  • No
  • Yes
  • Yes
Trauma
  • Yes
  • No
  • No
  • No

 

Treatment
  • Supportive care with fluids to maintain renal perfusion
    • dialysis if acute renal failure unresponsive to fluids
  • Fresh frozen plasma can be used (increases coagulation factor levels)
  • Plasmapheresis or plasma exchange for severe cases
Prognosis, Prevention, and Complications
  • Prognosis
    • 3-5% mortality
    • 5% severe sequelae such as end-stage renal failure
  • Prevention
    • prevent EHEC infection
      • avoid raw or undercooked meat
    • avoid antimotility agents or antibiotics
  • Complications
    • chronic kidney disease
    • hypertension
    • heart failure
    • electrolyte abnormalities
 

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Questions (2)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
Calculator

(M2.HE.4673) A 6-year-old male presents to the emergency room complaining of severe abdominal pain. His mother notes that he has had several episodes of diarrhea for the past week, with vomiting over the past 3 days. The child is on summer vacation and attended a 4th of July barbecue 1 week ago. The patient's vital signs are as follows: T 38.3 C, HR 116, BP 110/75, SpO2 98%. Physical exam is remarkable for diffuse abdominal tenderness without rebound or guarding. CBC shows WBC 9 x10^3/uL, Hgb 10.2 g/dL, Hct 33%, Plt 46 x10^3/uL. Peripheral blood smear yields the following findings (Figure A). The patient's creatinine is found to be elevated at 1.3. What is the underlying cause of this patient's anemia? Review Topic

QID: 107021
FIGURES:
1

Chronic renal disorder

0%

(0/18)

2

Gastrointestinal arterio-venous malformation

0%

(0/18)

3

Poor dietary nutrition intake

0%

(0/18)

4

Inheritance of a beta-globin gene variant

6%

(1/18)

5

Toxin-mediated damage to endothelial cells and prothrombotic changes

89%

(16/18)

M2

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PREFERRED RESPONSE 5

(M2.HE.33) A 6-year-old boy is admitted with a one-week history of diarrhea, which was sometimes bloody and originally began after a birthday party. He has become lethargic and has not been eating or drinking. His vital signs are as follows: T 38.5 C, HR 135, BP 82/54. Physical examination is significant for petechiae on his legs and diffuse abdominal tenderness to palpation. Lab-work shows BUN 72 mg/dL, creatinine 8.1 mg/dL, and platelet count < 10,000. PT and PTT are within normal limits. Which of the following would be expected on a peripheral blood smear? Review Topic

QID: 104673
1

Rouleaux formation

0%

(0/30)

2

Fragmented red blood cells

83%

(25/30)

3

Spur cells

3%

(1/30)

4

Giant platelets

3%

(1/30)

5

No abnormalities

3%

(1/30)

M2

Select Answer to see Preferred Response

PREFERRED RESPONSE 2
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