hemolytic uremic syndrome: a dangerous complication of e. coli
DESCRIPTION
In this presentation provided by the nation's foremost food poison law firm - Marler Clark, Hemolytic Uremic Syndrome (HUS) is explained. HUS is a rare and highly dangerous result of an E. coli infection and can result in acute kidney failureTRANSCRIPT
Long-Term Health Long-Term Health ImplicationsImplications
Hemolytic Uremic Syndrome (HUS)(HUS)
Normal Kidney Structure Normal Kidney Structure and Functionand Function
Renal Artery Takes blood into kidneyTakes blood into kidney
Renal Vein Takes blood from kidneyTakes blood from kidney
Ureter Takes urine to the bladderTakes urine to the bladder
Normal KidneyNormal Kidney
From “The Human Body, Dorling Kindersly Limited, London 1995
Blood In
Blood Out
Urine Out
Renal Cortex Where the Where the
blood is blood is filtered filtered into urineinto urine
The Human Body, Dorling Kindersly Limited, London 1995
GlomerulusGlomerulus The structure which The structure which
filters blood into urinefilters blood into urine
Normal KidneyNormal Kidney
Courtesy of JC Jennette, MD, UNC-Chapel Hill
Normal KidneyNormal Kidney
The Human Body, Dorling Kindersly Limited, London 1995
Measuring Kidney Measuring Kidney Structure and FunctionStructure and Function
StructureStructure– Renal ultrasoundRenal ultrasound
– Renal biopsyRenal biopsy
FunctionFunction– Glomerular filtration rateGlomerular filtration rate
– Blood and urine creatinineBlood and urine creatinine
– UrinalysisUrinalysis
Courtesy S. Williamson MD, U of New Mexico
Structure: Renal UltrasoundStructure: Renal Ultrasound
Provides Provides information information about:about:– Size Size
– Echogenicity Echogenicity
– Stones/ScarsStones/Scars
– ObstructionObstruction
Provides Provides informationinformationabout functionabout function
Normal Glomerulus Acute HUS Glomerulus
Courtesy of JC Jennette, MD, UNC-Chapel Hill
Structure: Kidney BiopsyStructure: Kidney Biopsy
*GFR is usually expressed in terms of average adult body surface area: meters squared
Function: Function: Glomerular Filtration Rate (GFR)Glomerular Filtration Rate (GFR)
The rate at which blood The rate at which blood is filtered by the kidneyis filtered by the kidney
Normal GFR = Normal GFR = 90–150 ml/min/1.73m2*90–150 ml/min/1.73m2*
The most accurate measure The most accurate measure of kidney functionof kidney function
CreatinineCreatinine
A by-product of normal A by-product of normal muscle metabolismmuscle metabolism
Blood or 24-hour urine levels Blood or 24-hour urine levels are used to estimate GFRare used to estimate GFR– Most commonMost common
– Easily obtainedEasily obtained
– Overestimates actual kidney Overestimates actual kidney function (GFR)function (GFR)
A Window Into the Kidney’s A Window Into the Kidney’s HealthHealth
Blood
UrinalysisUrinalysis
Normal Value
Protein
24-Hr Protein
Protein/Cr ratio
None (< 4 rbc/hpf)
None or trace
< 150 mg/day
< 0.2 (mg/mg)
What Goes Wrong During HUS?What Goes Wrong During HUS?
At the cell and organ levelAt the cell and organ level– Pathology and PathophysiologyPathology and Pathophysiology
At the patient level At the patient level – Clinical findingsClinical findings
Thrombotic Microangiopathy (TMA)Thrombotic Microangiopathy (TMA)
The pathologic lesion of HUSThe pathologic lesion of HUS E. Coli Shigatoxin damages endothelial cellsE. Coli Shigatoxin damages endothelial cells
– Endothelial swelling narrows Endothelial swelling narrows vessel lumenvessel lumen
– Platelet/fibrin clots form blocking Platelet/fibrin clots form blocking blood flowblood flow
Poor blood flowPoor blood flow– Low tissue oxygen (hypoxia)Low tissue oxygen (hypoxia)
HypoxiaHypoxia– Cell dysfunctionCell dysfunction
– Cell necrosis (death)Cell necrosis (death)
Adapted from Stewart CL, Pediatr Rev, 1993
A: Normal Glomerular blood vessel
B: (-) charged endothelial cell (+) charged Platelet ( )
C: Loss of (-) charge and PGI2 due to endothelial damage
D: Fibrin/platelet thrombi formation
HUS PathogenesisHUS Pathogenesis
A B
C D
Courtesy of P Tarr MD, Univ of Washington
The Kidney in HUSThe Kidney in HUS
Normal Capillary
TMA Capillary
ThrombusExpanded subendothelial zone
Narrowed lumen
Toxin causing injury to endothelial cells
Courtesy of JC Jennette, MD, UNC-Chapel Hill
Micrograph of TMA Micrograph of TMA in Glomerulusin Glomerulus
Glomerular Light Microscopy
Normal Capillary TMA Capillary
Lumen Subendothelial Expansion
Micrograph of TMA Micrograph of TMA in Renal Arteryin Renal Artery
Courtesy of JC Jennette, MD, UNC-Chapel Hill
Normal Artery TMA Artery
Arterial Intimal Thickening
Lumen Intimal Expansion Obliterating Lumen
Fibrin Strands
Red Blood Cells
Courtesy of P Tarr MD, Univ of Washington
Electron Micrograph of Fibrin Electron Micrograph of Fibrin Clot and Red Blood CellsClot and Red Blood Cells
* Acute Tubular Necrosis (ATN) is an exception to this
Tissue Damage vs Necrosis Tissue Damage vs Necrosis
HUS induced hypoxia: HUS induced hypoxia: “Cell Suffocation”“Cell Suffocation”
Tissue injury without loss of structureTissue injury without loss of structure– RepairableRepairable
Tissue death (necrosis*) leads to: Tissue death (necrosis*) leads to: – Scar formationScar formation
– Permanent injury Permanent injury
– Loss of functionLoss of function
Clinical Findings in Acute HUSClinical Findings in Acute HUS
Serum creatinine levelSerum creatinine level GFRGFR Blood pressureBlood pressure Urine proteinUrine protein Urine outputUrine output
Normal KidneyNormal Kidney
Serum CrSerum Cr
4-year Old with Normal Kidneys
GFR
BP
Urine Protein
Urine Prot/Cr
Urine Output
0.5 mg/dl
120 ml/min/1.73m2
100/60
none
0.09 (nl < 0.2)
1000 ml/day
- Areas of HUS Activity
Acute HUSAcute HUS
AbnormalitiesAbnormalities
2.5 mg/dl
23 ml/min/1.73m2
140/90
300 mg/dl
1.8
125 ml
High
Low
High
High
High
Low
Serum Cr
GFR
BP
Urine Protein
Urine Prot/Cr
Urine Output
Oliguria (Low Urine Oliguria (Low Urine Output)Output)
Frequency (of patients)
Dialysis
Blood Transfusion
Platelet Transfusion
Hypertension
Death
70%
50%
70%
30%
30%
4%
Clinical Findings Clinical Findings in Acute HUS Renalin Acute HUS Renal
Siegler RL, Spectrum of involvement in post-diarrheal hemolytic-uremic syndrome. J Pediatrics, 125(4): 511-518, 1994
Other Organs InvolvedOther Organs Involvedin Acute HUSin Acute HUS
Intestine
Liver
Brain
Pancreas
Heart / Lung / Other
100 %
40 %
20 %
20 %
< 1 %
Frequency
Why the Kidney? Why the Kidney? Why Children?Why Children?
Children get E. coli O157 infections:Children get E. coli O157 infections:– Peak age = 1-6 yearsPeak age = 1-6 years
The cell receptor for Shigatoxin: Gb3The cell receptor for Shigatoxin: Gb3– Gb3 concentrations are:Gb3 concentrations are:
– Higher in the KidneyHigher in the Kidney
– Higher in ChildrenHigher in Children
What Happens to the Kidney What Happens to the Kidney as HUS Resolves?as HUS Resolves?
Areas of Cell Hypoxia repair to normalAreas of Cell Hypoxia repair to normal Areas of TMA mostly repair to normalAreas of TMA mostly repair to normal Areas of Necrosis form Scar tissueAreas of Necrosis form Scar tissue
What Happens to the Kidney What Happens to the Kidney as HUS Resolves?as HUS Resolves?
Kidney compensation for scar tissue:Kidney compensation for scar tissue:– Normal areas work harder: HyperfiltrationNormal areas work harder: Hyperfiltration
Excessive Hyperfiltration leads to:Excessive Hyperfiltration leads to:– Progressive Glomerular Scarring!!!Progressive Glomerular Scarring!!!
0.5
Six months after HUSSix months after HUS
- Areas of scar formation
115 ml/min/1.73m2
100/60
10 mg/dl
0.2
NL
NL
NL
NL
NL
Serum Cr
GFR
BP
Urine Protein
Urine Prot/Cr
III. Significant Hyperfiltration
I.None/Minimal Hyperfiltration
II.Moderate Hyperfiltration
5 Years After HUS:5 Years After HUS:Possible OutcomesPossible Outcomes
Chronic Renal Failure
4.0
10-30 Years After HUS10-30 Years After HUS
NO
Maybe?
Probable
Serum Cr
28GFR
U Prot Elevated
BP High
How Do We Study the Effects How Do We Study the Effects (Sequelae) of HUS?(Sequelae) of HUS?
Glomerular Filtration Rate (GFR)Glomerular Filtration Rate (GFR) Urinalysis: ProteinuriaUrinalysis: Proteinuria Blood PressureBlood Pressure Renal BiopsyRenal Biopsy
GFR After HUSGFR After HUS
The most accurate method of The most accurate method of following actual renal functionfollowing actual renal function
MethodsMethods– Iothalamate, Inulin, Cr Clearance, Iothalamate, Inulin, Cr Clearance,
EDTA, or DPTAEDTA, or DPTA
– Time consumingTime consuming
– Require either an IV line and/or long Require either an IV line and/or long urine collectionurine collection
Proteinuria After HUSProteinuria After HUS
Causes in general Causes in general – Infection, renal inflammation, fever, etc.Infection, renal inflammation, fever, etc.
After HUS: Proteinuria After HUS: Proteinuria – HyperfiltrationHyperfiltration
Proteinuria and ACE InhibitorsProteinuria and ACE Inhibitors
ACE Inhibitors (ACEIs) ACE Inhibitors (ACEIs) – Blood Pressure MedicationsBlood Pressure Medications
ACEIs also decrease ACEIs also decrease Renal HyperfiltrationRenal Hyperfiltration
ACEIs slow damage due ACEIs slow damage due to Hyperfiltrationto Hyperfiltration
Blood PressureBlood Pressure
New High Blood Pressure after HUS may New High Blood Pressure after HUS may be a sign of permanent kidney damagebe a sign of permanent kidney damage
Renal scars cause high blood pressure Renal scars cause high blood pressure throughthrough– ReninRenin
ACEIs block Renin actionACEIs block Renin action
Renal BiopsyRenal Biopsy
To evaluate structural damage after HUSTo evaluate structural damage after HUS Useful in predicting future problemsUseful in predicting future problems Does not provide information about functionDoes not provide information about function Rarely done in the U.S. Rarely done in the U.S.
(except in research)(except in research)
Why Is It Difficult to Interpret Why Is It Difficult to Interpret Outcome Studies in HUS?Outcome Studies in HUS?
Rarity of DiseaseRarity of Disease Variation inVariation in
– Disease Severity and E. Coli virulenceDisease Severity and E. Coli virulence
– Measuring OutcomesMeasuring Outcomes
Lack of long term follow-up by patientsLack of long term follow-up by patients
Rarity of DiseaseRarity of Disease
IncidenceIncidence (cases/100,000 children/yr)(cases/100,000 children/yr)
HUS
ALL (Leukemia)
Congenital Heart Disease
Urinary Tract Infection
2
13
100
225
Evaluation of HUS OutcomesEvaluation of HUS Outcomes
Renal FunctionRenal Function– GFR by serum Cr, urine CrCl, Iothalamate, GFR by serum Cr, urine CrCl, Iothalamate,
EDTA, etc.EDTA, etc.
– Renal Plasma FlowRenal Plasma Flow
– Renal Concentrating AbilityRenal Concentrating Ability
ProteinuriaProteinuria– DipstickDipstick
– U Prot / Cr ratioU Prot / Cr ratio
– 24 hr urine protein24 hr urine protein
Renal BiopsyRenal Biopsy
A Word About Study SizeA Word About Study Size
NumberNumberFolloweFollowedd
Number Abnormal
PercentageAbnormal
1
1
10
100
1000 1
10%
1%
0.1%
What Do The Outcome Studies What Do The Outcome Studies Show So Far?Show So Far?
Measures used most consistently Measures used most consistently – Hypertension Hypertension
– ProteinuriaProteinuria
– Low GFRLow GFR
– ESRD (End Stage Renal Disease)ESRD (End Stage Renal Disease)
Outcome Studies of NoteOutcome Studies of Note
E. coli associated patients onlyE. coli associated patients only Follow-up > 5 yearsFollow-up > 5 years Study AssessedStudy Assessed
– HypertensionHypertension
– ProteinuriaProteinuria
– Renal FunctionRenal Function
– Evaluated outcome predictorsEvaluated outcome predictors
9 Outcome Studies on E. coli-9 Outcome Studies on E. coli-related HUS Published 1988–1998related HUS Published 1988–1998
# Patients Followed# Patients Followed
Years of Follow-up
Renal Sequelae (Yes / No)
HypertensionProteinuriaLow GFRESRD
478 (73%)
0.5 - 28 yrs
35 %/65%
0 - 20 %8 - 31 %1 - 28 %5 %
Renal Sequelae May Develop After Renal Sequelae May Develop After a Period of Normal Renal Testsa Period of Normal Renal Tests
Siegler, Utah, 1991
Gagnadoux, France, 1996
“Abnormalities sometimes appeared after an interval of apparent recovery.” (proteinuria)
“...4 had reached end-stage renal failure (ESRF) 16-24 years after onset; 2 of these latter 4 had a normal GFR at 10-year examination.”
Predictors of Renal Damage Predictors of Renal Damage in HUSin HUS
1) Elevated WBC count at presentation1) Elevated WBC count at presentation 2) Prolonged Oliguria or Anuria (or Dialysis)2) Prolonged Oliguria or Anuria (or Dialysis) 3) Severe tissue damage on HUS biopsy3) Severe tissue damage on HUS biopsy
– Extensive TMA (> 50% of gloms)Extensive TMA (> 50% of gloms)
– Cortical necrosisCortical necrosis
4) Low GFR at > 2 year follow-up4) Low GFR at > 2 year follow-up
Common Symptoms with Renal Common Symptoms with Renal Damage after HUS Damage after HUS
Most common: NONEMost common: NONE High Blood Pressure, Low GFR, High Blood Pressure, Low GFR,
Proteinuria usually cause no Proteinuria usually cause no noticeable signs or symptomsnoticeable signs or symptoms
How Will You Know If Your Child Is How Will You Know If Your Child Is at Risk of Future Kidney Damage?at Risk of Future Kidney Damage?
Yearly follow-up with a Pediatric Yearly follow-up with a Pediatric NephrologistNephrologist
Yearly blood pressure and urinalysisYearly blood pressure and urinalysis GFR and creatinine every few years GFR and creatinine every few years
– 1, 3, 5, 10, 15 yrs, …etc.1, 3, 5, 10, 15 yrs, …etc.
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