Ch 22: Kidney Disease

Question 1

What do red cell casts in the urine indicate?

Answer 1

glomerulonephritis (p. 914)

Question 2

In what conditions are renal tubular cell casts seen?

Answer 2

acute tubular necrosis, interstitial nephritis (p. 914)

Question 3

What is the formula for the fractional excretion of sodium (FE_Na)?

Answer 3

FE_Na = [Urine_Na / Serum_Na] / [Urine_Cr / Serum_Cr] X 100%

Question 4

What is oliguria defined as?

Answer 4

urinary output less than 400 - 500 ml per day, or less than 20 ml/hr

Question 5

What does a Fe_Na < 1% suggest?

Why?

Answer 5

Prerenal azotemia

With a decreased GFR, the kidney will reabsorb salt and water avidly if there is no intrinsic tubular dysfunction, thus patients with prerenal causes should have a low fractional excretion percent of sodium.

(p. 917)

Question 6

What is the Cockcroft-Gault formula and what is it used for?

Answer 6

It is used to estimate creatinine clearance (C_Cr), which incorporates age, sex, and weight to estimate creatinine clearance from plasma creatinine levels without any urinary measurements:

If female, multiple the final answer by 0.85.

Question 7

The Cockcroft-Gault formula overestimates GFR in patients who are _____ or _________ and is most accurate when normalized for a body surface area of 1.73 m2.

Answer 7

obese, edematous

Question 8

BUN is synthesized mainly in the _____ and is the end product of _______ __________.

Answer 8

liver, protein catabolism

Question 9

Urea reabsorption may be decreased in volume _______ patients, whereas volume depletion causes increased urea reabsorption, in conjunction with increased ______ reabsorption, from the kidney, increasing BUN.

Answer 9

replete, sodium

Question 10

A normal BUN:creatinine ratio is…

Answer 10

…10:1.

Question 11

Indications for percutaneous needle biopsy include…

(Name 7)

Answer 11

(1) unexplained acute kidney injury or CKD
(2) acute nephritic syndromes
(3) unexplained proteinuria and hematuria
(4) previously identified and treated lesions to plan future therapy
(5) systemic diseases associated with kidney dysfunction, such as systemic lupus erythematosus (SLE), Goodpasture syndrome, and granulomatosis with polyangiitis (eFigure 22–3), to confirm the extent of renal involvement and to guide management
(6) suspected transplant rejection, to differentiate it from other causes of acute kidney injury
(7) to guide treatment

Question 12

After biopsy, hematuria occurs in….

Answer 12

…..nearly all patients, but less than 10% will have macroscopic hematuria.

Question 13

With patients who are taking cyclosporine to prevent kidney allograft rejection, kidney biopsy is often necessary to….

Answer 13

….distinguish transplant rejection from cyclosporine toxicity.

Question 14

Studies have shown that __________ ________ improves outcome in acute kidney injury.

Answer 14

nephrology referral

Question 15

Rhabdomyolysis of clinical importance commonly occurs with a serum creatine kinase (CK) greater than…

Answer 15

…20,000 – 50,000 international units/L.

Question 16

What test will be falsely positive in the setting of rhabdomyolysis?

Answer 16

The urine dipstick for hemoglobin/hematuria.

Question 17

The most common drugs to cause interstitial nephritis are…

Answer 17

…penicillins and cephalosporins, sulfonamides and sulfonamide-containing diuretics, NSAIDs, rifampin, phenytoin, and allopurinol.

Question 18

Clinical features of acute interstitial nephritis can include…

Answer 18

…fever (more than 80% of cases), rash (25–50%), arthralgias, and peripheral blood eosinophilia (80%).