Pathology

Question 1

_____ still has coagulation factors and _____ doesn’t.

Answer 1

Plasma still has coagulation factors and serum doesn’t.

Question 2

Order a BUN and creatinine on everyone with _____ or ______, everyone
with an _____ (except “trace protein” or “honeymoon
cystitis”), everyone on the general medical inpatient service, or
any life-threatening injury or illness.

Answer 2

Order a BUN and creatinine on everyone with newlydiagnosed
hypertension or newly-diagnosed diabetes, everyone
with an abnormal urinalysis (except “trace protein” or “honeymoon
cystitis”), everyone on the general medical inpatient service, or
any life-threatening injury or illness.

Question 3

INCREASED BUN caused by:

Answer 3

Increased protein catabolism

Diet high in protein

Upper GI bleed

Physiologic stress

Question 4

UREA “BUN” – blood urea nitrogen is the body’s way of disposing of _____.

Answer 4

UREA “BUN” – blood urea nitrogen is the body’s way of disposing of ammonia.

Question 5

Urea is filtered by the _____. When flow is ____, urea tends
to be reabsorbed passively – hence it tends to rise faster than
_______ when the kidney is underperfused

Answer 5

Urea is filtered by the glomerulus. When flow is slow, urea tends
to be reabsorbed passively – hence it tends to rise faster than
Creatinine when the kidney is underperfused

Question 6

Prerenal \_\_\_\_\_ (underperfused kidney –
 clinically, the most common cause of elevated BUN)

Answer 6

Prerenal azotemia (underperfused kidney –
clinically, the most common cause of elevated BUN)

Question 7

Causes of prerenal azotemia:

Answer 7

Dehydration

Hemorrhage / shock

Congestive heart failure

Liver failure –
hepatorenal syndrome

Question 8

____ azotemia (the kidney itself is damaged)

Answer 8

Renal azotemia (the kidney itself is damaged)

Question 9

Causes of Renal Azotemia

Answer 9

Acute renal injury

Medications

Acute kidney disease

Chronic kidney disease

(catastrophic illness)

Question 10

Causes of Post-renal azotemia (the urine is blocked)

Answer 10

Prostatism

Kidney Stone

Tumors

Injury

Question 11

DECREASED BUN:

Answer 11

• Protein malabsorption
• Protein wasting (nephrotic syndrome)
• Liver failure
• Overhydration

Question 12

The breakdown product of creatine phosphate,
released at a steady rate from skeletal muscle

Answer 12

CREATININE

**One’s level reflects muscularity. **

Creatinine is filtered by the glomerulus and also secreted by the
tubules. When flow is slow, creatinine is still secreted actively –
hence it tends to rise less than BUN when the kidney is
underperfused.

Question 13

INCREASED CREATININE:

Answer 13

Kidney failure (acute, chronic)

Huge muscle mass

Cooked meat in diet?
Rhabdomyolysis?
Creatine powder? (probably not)

Medications (cimetidine, trimethoprim) inhibit
tubular secretion)

Question 14

The _____ of _____ by the body and in the urine makes it possible to report other values as “per gram of _____” to allow for variable dilution by water in the urine, rather than requiring a 24 hour specimen for quantitation.

Answer 14

The constant output of creatinine by the body and in the urine makes it possible to report other values as “per gram of creatinine” to allow for variable dilution by water in the urine, rather than requiring a 24 hour specimen for quantitation.

Question 15

______ is the classic estimate of glomerular filtration rate (GFR).

Answer 15

CREATININE CLEARANCE is the classic estimate of glomerular filtration rate (GFR).

Clearance = [conc in urine] x urine volume / [conc in plasma]

Question 16

Cystatin C / “gamma trace protein” is produced in small, constant amounts by all _________ cells and is superior to creatinine as an indicator of GFR / renal function.

Answer 16

Cystatin C / “gamma trace protein” is produced in small, constant amounts by all nucleated cells and is superior to creatinine as an indicator of GFR / renal function.

Question 17

Increased BUN &/or creatinine

Answer 17

AZOTEMIA

Question 18

The kidney is underperfused

Answer 18

PRERENAL AZOTEMIA

Question 19

The kidney is damaged.

Answer 19

RENAL AZOTEMIA

Question 20

BUN / creatinine ratio

Around __ in health and in renal azotemia.

Around __ in prerenal azotemia, GI bleeding & postrenal
azotemia.

Answer 20

BUN / creatinine ratio

Around 10 in health and in renal azotemia.

Around 20 in prerenal azotemia, GI bleeding & postrenal
azotemia.

Question 21

FRACTIONAL EXCRETION OF SODIUM

FENa = ((_____)x(serum Cr))/((serum Na)x(_____))

Answer 21

FENa = ((urine Na)x(serum Cr))/((serum Na)x(urine Cr))

Question 22

FRACTIONAL EXCRETION OF SODIUM

Often _____ prerenal azotemia / shock /
hepatorenal syndrome, plugged tubules (pigment nephropathy)

Often _____ acute renal injury.

Answer 22

Often less than 1% prerenal azotemia / shock /
hepatorenal syndrome, plugged tubules (pigment nephropathy)

Often more than 2% acute renal injury.

Question 23

The _____ of the urine can be estimated on the floor using a hygrometer (“urinometer”), refractometer, or dipstick.

Answer 23

The specific gravity of the urine can be estimated on the floor using a hygrometer (“urinometer”), refractometer, or dipstick.

Question 24

If someone can concentrate the urine above SG _____ and/or osmolality >___ mOsm/Kg(L), the medulla is working properly.

Answer 24

If someone can concentrate the urine above SG 1.020 and/or osmolality >800 mOsm/Kg(L), the medulla is working properly.

Question 25

In acute renal injury, the specific gravity is usually close to that of
plasma – ___ (“isosthenuria”). Osmolality is usually not much
more than for plasma, around
___ mOsm/Kg(L).

Answer 25

In acute renal injury, the specific gravity is usually close to that of
plasma – 1.010 (“isosthenuria”). Osmolality is usually not much
more than for plasma, around
300-350 mOsm/Kg(L).

Question 26

In prerenal azotemia, the specific gravity is more likely to be ____, and osmolality above ___ mOsm/Kg(L).

Answer 26

In prerenal azotemia, the specific gravity is more likely to be high, and osmolality above 500 mOsm/Kg(L).

Question 27

Regardless of when the patient gives the specimen, if it sits without _____ or _____, you’ll get zero glucose, alkaline urine, and vanished formed elements (thanks to the bacteria).

Answer 27

Regardless of when the patient gives the specimen, if it sits without refrigeration or preservative, you’ll get zero glucose, alkaline urine, and vanished formed elements (thanks to the bacteria).

Question 28

Foamy urine

Answer 28

Usually from proteinuria or conjugated bilirubinuria

Question 29

Concentration is measured by _____,
estimated on dipstick.

Answer 29

Concentration is measured by specific gravity,
estimated on dipstick.

Dilute urine (SG < 1.007)
(“hyposthenuria”):
Diabetes insipidus OR
your patient drank a
lot of water.

ISOSTHENURIA:
SG stuck at 1.010
suggests the renal
tubules are not working.