Renal Assessment

Question 1

Functions of the kidney

Answer 1

-Excretory: Filtration, Reabsorption, Secretion
-Endocrine (hormones): EPO, RAAS, Aldosterone
-Metabolic: Vitamin D, Calcium, Phosphorus, Insulin and Steroid metabolism

Question 2

Factors altering Serum Creatinine

Answer 2

Age/Weight/Gender (female): lower muscle mass
Diet: protein increases creatinine
Exercise: increases muscle breakdown –> increases creatinine

Drugs: inhibit the secretion of creatinine through the kidney -> INCREASE in creatinine

–> Cimetidine (H2 blocker, gastric acid), Cobicistat and dolutregaivr (HIV), dronedarone (antiarrhythmic), Trimethropim (TMX or bactrim component), Probenecid (uricosurics for gout), ARBs and ACEi

Question 3

BUN

Answer 3

-Measurement of the amount of Urea and nitrogen in the blood
-represents a balance between Urea production and Urea removal

Question 4

What does an elevated BUN mean?

Answer 4

in general, it indicates a worse renal function bc the kidney is responsible for eliminating urea

Question 5

What is GFR used for?

Answer 5

-> measures blood passage through the glomerulus

-mainly used for staging chronic kidney disease
-sometimes for drug dose adjustment (f.e. Metformin)

Question 6

What is Creatinine Clearance (CrCl) used for?

Answer 6

-> measures elimination of SCr
-used for most drug adjustments
-typically higher than CrCl

Question 7

Why might CrCl be better for measuring kidney function?

Answer 7

-bc creatine is being filtered and secreted in the proximal tubule, thereby measuring both processes

-GFR only measures the filtration rate (by the amount of blood that passes the glomerulus)

Question 8

What are the CrCl equations to determine renal function?

Answer 8

-Cockcroft and Gault: for most dosing
ranges from 0 - 120 ml/min

-Jeliffe Equation: used when height and weight are unknown (underestimates renal function)

-Schwartz Equation: used in pediatric patients

Question 9

Cockroft and Gault Equation

Answer 9

CrCl (ml/min) = (140-Age) IBW / SCr x 72
if female: *0.85

IBW = 50kg + (2.3 * every inch over 5ft)
for me 1ft 5in = 65inch * 2,3)
female 45kg + (2.3 * every inch over 5ft)

Question 10

When is adjusted body weight used?

Answer 10

When the actual BW is 125% of the IBW (so calculate IBW first)

Adj. BW = IBW + 0.4 (ActBW - IBW)

Use Actual BW: if the Actual BW is smaller than the IBW

Question 11

Limitations of the Cockroft and Gault Equation

Answer 11

-The study was done with 249 male
-they used the actual BW, not the IBW
-some drugs are studied using the actual BW -> the equation uses IBW

Question 12

Misinterpretation of low SCr

Answer 12

-low SCr indicates efficient kidney function
-in older patients, it doesn’t have to mean that the kidney is working well
-SCr is low in older patients due to lower muscle mass -> low muscle breakdown -> low creatinine

Question 13

Factors used to stage chronic kidney disease CKD

Answer 13

-GFR
-Urinary Albumin to Creatinine Ratio (ACR): how much Albumin escapes the kidney and ends up in the urine

a healthy kidney has a high GFR and a low ACR

Question 14

What is important when CKDs are staged?

Answer 14

-Stable renal function (stable GFR and ACR values) for 3 months
-estimates on patients with acute kidney injury are not accurate!

Question 15

What are optimal GFR and ACR values?

Answer 15

GFR: >90 –> G1
AACR: < 30 mg/g –> A1

Microalbuminuria: 30-300 mg/g –> A1 - A2
Macroalbuminuria: > 300 mg/g –> A3

Question 16

At what stage should dialysis for patients with acute kidney injuries be considered?

Answer 16

-around G4 –> GFR of 15-29

Q: How are values in patients with kidney injuries measured, since their values have to be stable for 3 months?

Question 17

Symptoms of CKD

Answer 17

Stage 1-2:
Asymptomatic, Microalbuminuria, SCr and BUN elevated

Stage 3-5: Edema, Fatigue, Pruritus, Nausea, Anemia, Macroalbuminuria, persistently elevated SCr/BUN