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 LowCVP High Heart size IncreasedS3 +EDP High ______________________________________These patients have different diseases

AGN vs CHF (cont)

AGN CHFBP rises falls Facial edema + -Renin low high Aldosterone low high AVP low high

AGN vs CHF (cont)

AGN CHFDigitalis - +CO high lowA-V O2 Δ low highA-V pH Δ low high

Characteristics of Edematous Diseases

Primary Secondary Nephritic CHF Renal Failure Cirrhosis NS NS

ECF vol high highPlasma vol high highBP high low CO high low to high

Characteristics of Edematous Diseases 2

Primary Secondary

Nephritic CHF Renal Failure Cirrhosis NS NS

GFR low* lowRBF nl* lowerFF low highRenin low highAldo low high

Characteristics of Edematous Diseases 3 Primary Secondary

Nephritic CHF Renal Failure Cirrhosis NS NS

SNS activity Nl IncreasedADH Low HighFNa Excretion Low Low

Primary Salt Retention

Salt retention

EABV

BPEdema

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 Secondary Nephritic CHF Renal Failure Cirrhosis NS NS

ECF vol high highPlasma vol high highBP high low CO high low to high

Characteristics of Edematous Diseases------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Primary Secondary

Nephritic CHF Renal Failure Cirrhosis NS NS

GFR low* lowRBF nl* lowerFF low highRenin low highAldo low high

Characteristics of Edematous Diseases------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Primary Secondary

Nephritic CHF Renal Failure Cirrhosis NS NS

SNS activity Nl IncreasedADH Low HighFNa Excretion Low Low