Edematous Diseases
May 3, 2013
Neil A Kurtzman, MD
Edema
• CHF
• AGN
• Nephrotic Syndrome
• Cirrhosis
Irrespective of disease, the cause of edema is
always renal salt retention
John Peters – 1948
• A normal kidney retains salt in patients with CHF
• Volume must be contracted
• The kidney retains salt when volume is contracted
• It excretes salt when volume is expanded
• What is the volume compartment the kidney recognizes?
Volume Candidates
• Blood volume
• Interstitial volume
• Extracellular volume
Peters invented a volume compartment
EABV
Effective Arterial Blood Volume
• A concept not a measurable entity
• Normal EABV is that amount of arterial filling that
assures adequate organ perfusion
• Its state is inferred from history, PE, and lab
values
EABV
• Vomiting
• Diarrhea
• Sweating
• Hemorrhage
• CHF
• Some forms of nephrotic syndrome
• Cirrhosis
EABV
• History
• PE – BP
• Low urine Na
• High uric acid
• Increased BUN:Cr
CHF
• CO inadequate
• Circulation underfilled
• EABV decreased
• Kidney retains salt and water
• Edema
AGN vs CHF
Edema
+
Pulmonary Edema +
Urine Na
Low
CVP
High
Heart size
Increased
S3
+
EDP
High
______________________________________
These patients have different diseases
AGN vs CHF (cont)
BP
Facial edema
Renin
Aldosterone
AVP
AGN
CHF
rises
+
low
low
low
falls
high
high
high
AGN vs CHF (cont)
Digitalis
CO
A-V O2 Δ
A-V pH Δ
AGN
CHF
high
low
low
+
low
high
high
Characteristics of Edematous Diseases
Primary
Nephritic
Renal Failure
NS
ECF vol
Plasma vol
BP
CO
high
high
high
high
Secondary
CHF
Cirrhosis
NS
high
high
low
low to high
Characteristics of Edematous Diseases 2
Primary
Nephritic
Renal Failure
NS
GFR
RBF
FF
Renin
Aldo
low*
nl*
low
low
low
Secondary
CHF
Cirrhosis
NS
low
lower
high
high
high
Characteristics of Edematous Diseases 3
Primary
Nephritic
Renal Failure
NS
SNS activity
Nl
ADH
Low
FNa Excretion Low
Secondary
CHF
Cirrhosis
NS
Increased
High
Low
Primary Salt Retention
EABV
Salt
retention
BP
Edema
Renin
Aldo
AVP
Consequences of Primary Salt Retention
• Facial edema
• Normal Na
• Hypertension
Secondary Salt Retention
Consequences of Secondary Salt Retention
• Dependent edema
• Hyponatremia
• BP falls
• Hypokalemia
• Metabolic alkalosis
Nephrotic Syndrome – Low EABV
• Plasma volume may be reduced
• High renin
• Renal underperfusion
• Increased Na excretion after vol expansion or water immersion
• Increased SNS activity
• BP rises after remission
Nephrotic Syndrome – High EABV
• Plasma vol nl or increased
• Low renin
• No response to vol expansion
• Low FF
• BP falls after remission
Implications for Diuretic Rx
• Patients with nephritic edema will respond
• CHF – depends on Starling curve
• NS will respond if EABV is high
• Cirrhosis - rarely does any good
Conclusions
• Edema always results from renal salt retention
• Primary edema – EABV is expanded
• Secondary edema – contracted EABV cause the salt retention
Secondary Salt Retention
Characteristics of Edematous Diseases
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Primary
Nephritic
Renal Failure
NS
ECF vol
Plasma vol
BP
CO
high
high
high
high
Secondary
CHF
Cirrhosis
NS
high
high
low
low to high
Characteristics of Edematous Diseases
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
GFR
RBF
FF
Renin
Aldo
Primary
Secondary
Nephritic
Renal Failure
NS
CHF
Cirrhosis
NS
low*
nl*
low
low
low
low
lower
high
high
high
Characteristics of Edematous Diseases
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Primary
Nephritic
Renal Failure
NS
SNS activity Nl
ADH
Low
FNa Excretion Low
Secondary
CHF
Cirrhosis
NS
Increased
High
Low