UA Book Q's Chp. 4

The daily volume of urine excreted normally ranges from

600 to 1800 mL/day.

Another name for excessive thirst is

polydipsia

The excretion of large volumes of urine (>3 L/day) is called

polyuria

When the body is dehydrated, the kidneys

excrete solutes in as small a volume of urine as possible.

The excretion of less than 400 mL of urine per day is called

oliguria

What Does Not produce nocturia

anuria

What following conditions can produce nocturia

• pregnancy.

• chronic renal disease.

• fluid intake at night.

What will not influence the volume of urine produced?

Carbohydrate ingestion

What Will influence the volume of urine production?

• Diarrhea

• Exercise

• Alcohol ingestion

What solutes are present in the largest molar amounts in urine?

Urea, chloride, and sodium

Renal excretion is not involved in the elimination of

normal byproducts of fat metabolism.

The concentration of which substances provides the best means of distinguishing urine from other body fluids?

Creatinine and urea

What is the definition of the osmolality of a solution?

The number of solute particles per kilogram of solvent

The osmolality of a solution containing 1.0 mole of urea is equal to that of a solution containing

0.5 mole of NaCl.

The maximum osmolality that urine can achieve is determined by the

osmolality of the medullary interstitium

Serum osmolality remains relatively constant, whereas the urine osmolality ranges from

one to three times that of serum

Osmolality is a measure of solute

number

What solutes, if added to pure water, affects the specific gravity of the resultant solution more than it affects its osmolality?

glucose

Occasionally the specific gravity of a urine specimen exceeds that physiologically possible (i.e., >1.040). What substance when found in urine could account for such a high value?

Mannitol or radiation dyes

In a patient with chronic renal disease, in whom the kidneys can no longer adjust urine concentration, the urine specific gravity would be

1.010

Which of the following features is not a colligative property?

Osmotic pressure depression

List 3 colligative property

1. Boiling point elevation

2. Freezing point depression

3. Vapor pressure depression

An advantage of freezing point osmometry over vapor pressure osmometry is its

ability to detect volatile substances.

Osmolality measurements are considered to be a more accurate assessment of solute concentration in body fluids than are specific gravity measurements because

All solutes contribute equally

The freezing point of a urine specimen is determined to be −0.90°C. What is the osmolality of the specimen?

484 mOsm/kg

The ultrafiltrate in the urinary space of the glomerulus has a specific gravity of

1.010 and the same osmolality as the blood plasma

Which renal function is assessed using specific gravity and osmolality measurements?

Concentrating ability

A fluid deprivation test is used to

assess renal concentrating ability.

A fluid deprivation test involves the measurement of serum and urine

osmolality

The volume of plasma cleared per minute in excess of that required for solute elimination is called the

free-water clearance

A free-water clearance value of −1.2 would be expected from a patient experiencing

dehydration

Calculate the osmolar and free-water clearances using the following patient data.

Serum osmolality: 305 mOsm/kg

Urine osmolality: 250 mOsm/kg

Urine volume: 300 mL/2 hours

Is this individual excreting more water than is necessary for solute removal?

AND

Is the osmolar clearance “normal” (i.e., 2.0 to 3.0 mL/ min)?

yes

Calculate the osmolar and free-water clearances using the following patient data.

Serum osmolality: 305 mOsm/kg

Urine osmolality: 250 mOsm/kg

Urine volume: 300 mL/2 hours

If an individual excretes more water than necessary for solute removal AND has a normal osmolar clearance, and a Free-water clearance is obtained, would the urine be considered Hypo-osmotic or hyperosmotic?

Hypo-osmotic

What is an endogenous substance used to measure glomerular filtration rate?

Creatinine

Renal clearance is defined as the volume of

plasma cleared of a substance in a time interval.

Creatinine is a good substance to use for a renal clearance test because it

Has a constant plasma concentration

What groups would be expected to have the greatest 24-hour excretion of creatinine?

Men

Creatinine clearance results are “normalized” using an individual’s body surface area to account for variations in the individual’s

Muscle Mass

The following data are obtained from a 60-year-old female who is 4′8″ tall and weighs 88 lb:

Plasma creatinine: 1.2 mg/dL

Urine creatinine: 500 mg/L

Urine volume: 1440 mL/24 hours

Calculate the creatinine clearance.

Calculate the normalized creatinine clearance.

Creatinine Clearance: 42 mL/min

Normal Creatinine Clearance: 58 mL/min

The following data are obtained from a 60-year-old female who is 4′8″ tall and weighs 88 lb:

Plasma creatinine: 1.2 mg/dL

Urine creatinine: 500 mg/L

Urine volume: 1440 mL/24 hours

Creatinine Clearance: 42 mL/min

Normal Creatinine Clearance: 58 mL/min

Are these results normal for the patient?

Yes

A 24-hour urine collection is preferred for determination of creatinine clearance because of diurnal variation in the

glomerular filtration rate

Which of the following situations results in an erroneous creatinine clearance measurement?

A 24-hour urine collection maintained at room temperature throughout the collection

A 45-year-old female African-American had her serum creatinine determined using a creatinine method that is not calibrated to an IDMS reference method. Her serum creatinine was 1.5 mg/dL; what is her eGFR using the appropriate MDRD equation?

48 mL/min/1.73 m2

The glomerular filtration rate is controlled by

the renal blood flow.

For measurement of renal plasma flow, p-aminohippurate is an ideal substance to use because it

is secreted completely in its first pass through the kidneys

What percentage of the total cardiac output is received by the kidneys?

25%

Measuring the quantity of hydrogen ion excreted as titratable acids and ammonium salts in urine provides a measure of

tubular secretory function.

The oral ammonium chloride test evaluates the ability of the tubules to secrete

ammonia and hydrogen