Matt Luther, MD MSCIDivision of Clinical Pharmacology

Roy Zent, MD PhDDivision of Nephrology & Hypertension

Anatomy

Essential Functions

Renal Dysfunction

Cecil & Carpenter's Essentials of Medicine. 2010.

RC= renal corpuscule

Cx= cortex

V= vein

RP =renal papilla

AV =arcuate vein

MR =medullary ray

C= calyx

P= Papilla

U =Ureter

Mouse Glomerulus, x40, PAS

Trggvason et al. NEJM. 2006

Brenner & Rector, The Kidney, 7th ed.

1. Elimination of waste products

2. Fluid & Electrolyte homeostasis

3. Acid/Base balance

4. Regulation of extracellular fluid volume and blood pressure

5. Endocrine functionsa) Erythropoietin production

b) Vitamin D activation (1-hydroxylation)

c) Target organ for Aldosterone, PTH, ANP, ADH, Vitamin 1,25OH-D3

6. Drug Metabolism and excretion

Glomerular Dysfunction:

1. ↓Solute ClearanceUremia

2. Volume overload

a. Due to excessive protein loss↓Albumin/Oncotic P

b. Due to inadequate fluid excretion

3. Hypertension

4. Proteinuria

5. Na+, K+, Mg++, Water imbalance

Edema/Volume overload

Beggah et al. PNAS. 2002; 99: 7160.

1. Uremic Symptoms• Nausea

• Insomnia

• Fatigue

• Dysgeusia (metallic taste)

• Itching

• Confusion

• Pericarditis

2. Hyperkalemia

3. Hyperphosphatemia

4. Anemia

5. Volume Overload/edema

6. Hypertension

Hemodialysis

What is wrong with my kidney?

Physiologic Assessment

Histology

Kidney Injury Models:

5/6 Nephrectomy

Diabetic Nephropathy

1. Serum/Plasma Electrolytes/Acid/Base

2. Urine electrolytes

3. Renal clearance estimate (BUN/Creatinine)

4. Proteinuria Assessment

5. Volume assessment

http://www.abbottpointofcare.com/

Example: Hypokalemia

Urinary K+ Excretion

Low (Appropriate)Non-renal Loss

•GI•Sweat

High (Inappropriate)Renal Loss

NephSAP 2007. pg 214

Clinical Approach

Can be calculated by measuring plasma creatinine + timed urine creatinine measure

Assumptions: 1. stable creatinine production/excretion (Steady State)2. constant rate of creatinine production3. substance is filtered only, not reabsorbed

Clearance (CL)= theoretical volume of plasma that must be cleared of substance to account for the rate of removal.

CL = Rate of Clearance / Blood ConcentrationCL = U•V/P

U = urine conc., P=plasma conc., V=urine flow rate.

Creatinine

Drug Infusion

or

Body Production

Excretion

Constant Infusion

time[D

rug/M

eta

bolit

e]

Amount In = Amount Out

Drug Infusion

or

Body Production

↓Excretion

ΔCreatinine

Constant Infusion

time[D

rug/M

eta

bolit

e]

Nephrectomy

Amount In ≠ Amount Out

General problems with creatinine as a marker of GFR• Creatinine production is dependent on muscle mass,

gender, age…

• Creatinine is secreted by renal tubules• Secretion affected by drugs (e.g., triamterene,

cimetidine, amiloride)

• Steady state assumption

Specific problems in mice• Standard assay (Jaffe/Picric acid method) is not

specific for creatinine• Interfering substances more of a problem in rodents

than humans

Levey et al. Annals Int Med. 1999; 130(6): 461.

Keppler et al. Kidney Int. 2007; 71(1): 74

Generally Correlates with plasma Creatinine

Increased in:• Hypercatabolic states

• Dehydration

• GI bleeding

• Medications (steroids)

Needs Correlation with Renal Histopathology

Is not a direct measure of GFR

iSTAT EC8+

Inulin is filtered by the kidney with no secretion

Method:

• FITC-Inulin retro-orbital bolus

• Serial plasma sampling

• Simple Clearance Calculation

Qi et al. Am J Phys. 2004. 286(3): F590.

Generally a sign of microvascular/glomerularinjury

Ma et al. Kidney Int. 2000; 58: 1219

Albumin/Creatinine assayBayer DCA 2000

Total Protein Assay

Guan et al. Nature Medicine. 2005; 11: 861

Body Water Content

Urinary Na+ Excretion

Generally recommend assistance of trained pathologist (preferably renal pathologist)

Focus on Severity & Pattern of Injury• Glomerulus

• Tubules & Interstitium

• Vasculature

Various stains are useful:• Periodic Acid-Sciff

• H&E

• Masson Trichrome (matrix/collagen)

• Jones’ Silver Stain (collagen/Basement membrane)

PAS MassonTrichrome

H&E Jones’Silver Stain

http://www.uncnephropathology.org/jennette/ch1.htm

Renal perivascular fibrosisRenal tubular atrophy

Proteinaceous cast

Interstitial Fibrosis

Picrosirius Red Stain, x20Cross-polarized Light, x20

PAS, x20Glomerulosclerosis

Nephrin IHC Nagase. Hypertension. 2006.

http://www.uncnephropathology.org/jennette/ch1.htm

Normal Podocyte Foot Process Effacement

ElectronMicroscopy

Note: Western blot for Glomerular proteins Nephrin, Podocin, Desmin requires glomerular isolation. Not sensitive enough on whole tissue.

Sharma et al. AJP Renal. 2003; 284: 1134

Mesangial Expansion

Arterial Hyalinosis

Zhao. JASN. 2006; 17: 2664

WT db/db

eNOS-

db/db

eNOS- db/db

Fibronectin

Kanetsun et al. Am J Pathology. 2007; 170: 1473

Feature Human db/db MiceeNOS-

db/db MiceObesity Frequent ++ ++

GBM Thickening +++ +/- ++Albuminuria ++ + ++

Mesangial Expansion ++ + ++Arterial Hyalinosis ++ + ++

Nodular Glom. Lesions + - +↓GFR ++ - +

Hypertension Frequent - +Interstitial Fibrosis ++ - -

Tubular Atrophy + - -

Sharma et al. AJP Renal. 2003; 284: 1134