Lab Approach to a Patient with Renal Disease

Question 1

What is reabsorbed at the PCT?

Answer 1

Na+, Cl-, HCO3-, K+, H20, glucose, AA

Question 2

What is secreted at the PCT?

Answer 2

H+, organic acids, bases

Question 3

What is reabsorbed at the Descending Loop of Henle?

Answer 3

Nothing

Question 4

What is secreted at the Descending Loop of Henle?

Answer 4

H2O

Question 5

What is reabsorbed at the Ascending Loop of Henle?

Answer 5

Na+, Cl-, K+, Ca++, HCO3-, Mg++

Question 6

What is secreted at the Ascending Loop of Henle?

Answer 6

H+

Question 7

What is reabsorbed at the DCT?

Answer 7

Na+, Cl-, Ca++, Mg++, HCO3-, K+, H2O (w/ ADH)

Question 8

What is secreted at the DCT?

Answer 8

K+, H+

Question 9

What is Azotemia? Uremia?

Answer 9

Azotemia: ↑ BUN w/o symptoms
Uremia: ↑ BUN & Cr w/ symptoms

Question 10

If you decrease GFR by 50%, what will happen to your plasma creatinine levels?

Answer 10

Plasma creatinine will increase to twice the normal value (if creatinine production by the body remains the same)

Question 11

What is the formula for Fractional Na and what is the reference range?

Answer 11

FENa = (Na excretion / total filtered load) x 100

Na excretion = (Urine Na) / (Serum Na)
Total Load = (Urine Creatinine) / (Serum Creatinine)

Reference Range: [Urine Na] < 20 mEq/L & FENa < 1.0

Question 12

What is the reference range for Specific Gravity?

Answer 12

1.003 - 1.035

Question 13

What are some causes of pseudohematuria?

Answer 13

• Excessive consumption of beets, berries, or rhubarb
• Food coloring
• Certain laxatives
• Pain Medications

Question 14

What do RBC in cellular casts suggest? WBC in cellular casts? Granular casts? Muddy-brown casts?

Answer 14

RBC: glomerulonephritis
WBC: acute/chronic pyelonephritis
Granular: nonspecific, acute, chronic disease
Muddy-Brown: Tubular Damage (ATN)

Question 15

What is the use of a Plain Radiograph of the Abdomen (KUB)

Answer 15

Kidney size and shape
Detection of nephrolithiasis
(radiopaque) and nephrocalcinosis

Question 16

What is the use of Ultrasonography & CT scanning?

Answer 16

• Kidney size/shape
• Obstruction &radiolucent stones
• Simple vs. complex cysts
• Early evaluation of polycystic kidney
• Dx. evaluation of renal mass

Question 17

What is the use of an Intravenous Pyelogram?

Answer 17

• Kidney size/shape & calyceal anatomy
• Dx of medullary sponge kidney and papillary necrosis
• Detection of site/cause of obstruct.

Question 18

What is the use of a Radionuclide Study?

Answer 18

• Detection of urinary obstruction & urine leak
• Screening for renal artery stenosis
• Assessing renal arterial flow

Question 19

What is the use of a Renal Arteriography?

Answer 19

• Detection of renal artery stenosis
• Assessing for evidence of vasculitis
• Distinguishing vascular vs. solid masses

Question 20

What is the use of a Voiding Cystourethogram?

Answer 20

-Detection of vesicoureteral reflux

Question 21

What is the use of a Retrograde/Antegrade Pyelography?

Answer 21

• Determining site of obstruction

- Placement of ureteral stent

Question 22

What is the use of a MRI (Kidney)?

Answer 22

Detection of Renal Mass and Renal Vein Thrombosis