Urine

Question 1

What is the normal urine volume?

Answer 1

1 to 2 Liters

intake of water - insensible losses = urine output

Question 2

What are signs of impaired dilution?

Answer 2

impaired dilution = impaired water excretion = water retention = hyponatremia

can be associated with low urine

high urine OSM (ADH present)

Question 3

What is a normal specific gravity?

Answer 3

1.005 to 1.035

Question 4

What are the categorical values for proteinuria?

Answer 4

1+ = 30 mg/dL

2+ = 100 mg/dL

3+ = 500 mg/dL

4+ = >2000 mg/dL

Question 5

In the setting of metabolic acidemia, what should high urine pH raise suspicion for?

Answer 5

renal tubular acidosis

Question 6

What is the maximal tubular reabsorption of glucose?

Answer 6

300 mg/dL

Question 7

What is the urine anion gap in gap acidosis?

Answer 7

Urine K + Urine Na + Urine NH4 = Urine Cl + excreted anions (ex. ketoacids)

Question 8

What pathological process would give a dipstick positive urine with no RBCs on microscopy?

Answer 8

rhabdomyolysis, hemolysis, and dilute urine

low specific gravity

Question 9

What are the causes for hematuria?

Answer 9

GU cause

contamination

if RBC casts, proteinuria, or dysmorphic RBCs are present, suggests glomerulonephritis

Question 10

causes of leukocyturia

Answer 10

contamination

infection (vaginitis, urethritis, bladder, kidney)

inflammation of the kidney or bladder - interstitial cystitis, interstitial nephritis, eosinophils classically associated, though evidence does not support

Question 11

What do nitrites in the urine indicate?

Answer 11

some bacteria convert nitrates to nitrites

can be detected on dipstick

may be colonization or infection

Question 12

hyaline cast

Answer 12

found in normal urine

can also found in people who are dehydrated

fomred due to slow flow of urine

Question 13

What happens to the tubular cells in the case of AKI, morphologically?

Answer 13

proximal tubular cells lose their brush borders, undergo swelling, and blebbing of microvilli during injury, leading to cast formation

Question 14

pigmented cast

Answer 14

suggests ATN or rhabdomyolysis

Question 15

white cell cast

Answer 15

allergic interstitial nephritis

pyelonephritis

Question 16

fatty cast

Answer 16

often can see maltese crosses

suggests nephrotic syndrome

Question 17

maltese crosses

Answer 17

dead renal tubular epithelial cell filled with cholesterold from the lipiduria that occurs with nephrotic syndrome

Question 18

urine indices for obstruction

Answer 18

300-500 U Osm

>40 UNa

>1 FE Na

don’t rely on indices to diagnose, better to image or use a foley catheter

Question 19

What is the difference between prerenal and ATN?

Answer 19

depends on whether or not the tubules are working

in ATN, tubules are not functional, so spilling sodium (FE Na > 1 and UNa > 40)

can’t concentrate or dilute in ATN (UOsm < 350)

Question 20

What are the urine indices for prerenal injury?

Answer 20

U Osm > 500

U Na < 20

FE Na < 1

Question 21

What are the indices for AGN, and what features help diagnose it?

Answer 21

U Osm 300-500+

U Na < 40

Fe Na < 1

also presence of hematuria, proteinuria, and casts

Question 22

What are the values for high and low potassium?

Answer 22

< 20 mEq/day is low - serum potassium is likely low

> 40 mEq/day is high - serum potassium is likely high

Question 23

normal urine creatinine

Answer 23

15-20 mg/kg per day in females

20-25 mg/kg/day in males

Question 24

normal urine sodium

Answer 24

100-260 mEq/24 hours (varies on intake)

Question 25

normal urine potassium

Answer 25

25-125 mmol/24 hours (variable)

Question 26

normal urine chloride

Answer 26

100-250 mmol/24 (variable)

Question 27

When is a urine chloride measurement useful?

Answer 27

non-gap metabolic acidosis

metabolic alkalosis

Question 28

What are the cuases of saline resistance metabolic alkalosis (U Cl > 20)?

Answer 28

alkali ingestion

adrenal excess - hyperaldosteronism, Cushing’s Disease, meds (steroids)

Bartter’s syndrome

Gitelman’s syndrome

Liddle’s syndrome

Licorice

“Refeeding” alkalosis

Question 29

What are the causes of saline responsive metablic alkalosis (U Cl <10)

Answer 29

GI loss - vomiting, diarrhea (with Cl-), and adenoma

post hypercapnia

diuretics

Question 30

What does specific gravity measure and what SG is isosthenuria?

Answer 30

measures how concentrated the urine is

isosthenuria occurs at 1.012

lower means dilure, and higher means concentrated

each unit of specific gravity approximates 1150 (range of urine Osm)/28 (range of urine Osm)

Question 31

What is the calculation of urine osmols from specific gravity?

Answer 31

40 Osm per 0.001 unit of specific gravity