Question 1

Which of the following clearance substances does not require urine collection?
A) Creatinine
B) Cystatin C
C) Inulin
D) 5-HIAA

Accepted Answer

Cystatin C clearance can be estimated from serum levels without the need for urine collection, unlike creatinine, inulin, and 5-HIAA, which require urine samples to accurately measure their clearance from the body.

Question 2

Following a 2-hour infusion of p-aminohippuric acid (PAH),during which 200 mL of urine is collected,the urine PAH is 260 mg/dL,and the patient's plasma PAH is 0.8 mg/dL.Calculate the renal plasma volume.
A) 525 mL/min
B) 553 mL/min
C) 614 mL/min
D) 765 mL/min

Accepted Answer

The formula for calculating renal plasma volume (RPF) is:

RPF = (Urine PAH concentration x Urine flow rate) / Plasma PAH concentration

Plugging in the given values:

Urine PAH concentration = 260 mg/dL
Urine flow rate = 200 mL/2 hours = 100 mL/hour = 1.67 mL/minute
Plasma PAH concentration = 0.8 mg/dL

RPF = (260 x 1.67) / 0.8 = 542.17 mL/min

Round off to the nearest whole number: 553 mL/min.

Therefore, the correct answer is B: 553 mL/min.

Question 3

Can a patient with the following results be given a nephrotoxic medication: urine volume-720 mL/24 h,urine creatinine-100 mg/dL,and serum creatinine-2.5 mg/dL?
A) No, clearance is 20 mL/min
B) No, clearance is 40 mL/min
C) Yes, clearance is 80 mL/min
D) Yes, clearance is 120 mL/min

Accepted Answer

The patient's creatinine clearance is calculated as:
Creatinine clearance = (urine creatinine x urine output)/serum creatinine
= (100 mg/dL x 720 mL/24 h)/2.5 mg/dL
= 28.8 mL/min
This value indicates that the patient has moderate renal impairment and is at risk for further kidney damage from nephrotoxic medications. Therefore, nephrotoxic medications should not be administered to this patient. The correct answer is therefore A - No, clearance is 20 mL/min.

Question 4

A patient showing symptoms of impaired renal function has a battery of tests performed.Results are:
Serum creatinine: 2.0 mg/dL
Urine creatinine: 150 mg/dL
Serum osmolality: 270 mOsm
Urine osmolality: 100 mOsm
24-hour urine volume: 2000 mL
-Based on the information provided,which renal function is abnormal in this patient?
A) Glomerular filtration
B) Tubular reabsorption
C) Tubular secretion
D) Renal blood flow

Accepted Answer

The low urine osmolality (100 mOsm) indicates impaired tubular reabsorption, which is responsible for concentrating urine. The normal serum creatinine (2.0 mg/dL) indicates that glomerular filtration is not significantly impaired. The given values do not provide information about tubular secretion or renal blood flow.

Question 5

A physician is treating a patient exhibiting symptoms of impaired renal function following a massive hemorrhage.The physician orders a serum sodium and a PAH clearance test.The patient has a serum PAH of 1.0 mg/dL,urine PAH of 200 mg/dL,and a urine volume of 240 mL in 2 hours.The serum sodium is decreased.
-Using the information provided,based on the tests ordered,what renal function is the physician's primary concern?
A) Glomerular filtration
B) Tubular reabsorption
C) Tubular secretion
D) Renal blood flow

Accepted Answer

The PAH (para-aminohippuric acid) clearance test is specifically used to measure renal plasma flow, which is closely related to renal blood flow. PAH is almost completely cleared from the blood by the kidneys in a single pass, making it an excellent marker for assessing renal blood flow. The concern for impaired renal function following a massive hemorrhage would logically lead to an assessment of renal blood flow, as hemorrhage can significantly impact blood volume and pressure, thereby affecting the kidneys' ability to receive and filter blood.

Question 6

A patient showing symptoms of impaired renal function has a battery of tests performed.Results are:
Serum creatinine: 2.0 mg/dL
Urine creatinine: 150 mg/dL
Serum osmolality: 270 mOsm
Urine osmolality: 100 mOsm
24-hour urine volume: 2000 mL
-Using the information provided,calculate the creatinine clearance.
A) 50 mL/min
B) 85 mL/min
C) 105 mL/min
D) 110 mL/min

Accepted Answer

The answer of A patient showing symptoms of impaired renal...

Question 7

A laboratory supervisor is authorized to purchase a new osmometer.The supervisor must decide between a freezing-point and a vapor-pressure model.
-Based on the information provided,if this is a pediatric hospital,which model is better?
A) Freezing-point
B) Vapor-pressure

Accepted Answer

The answer of A laboratory supervisor is authorized to purchase...

Question 8

A laboratory supervisor is authorized to purchase a new osmometer.The supervisor must decide between a freezing-point and a vapor-pressure model.
-Using the information provided,which model is more likely to be affected by technical errors?
A) Freezing-point
B) Vapor-pressure

Accepted Answer

Vapor-pressure osmometers are generally more sensitive to technical errors, such as contamination or improper sample handling, compared to freezing-point osmometers. This is because the measurement of vapor pressure can be more easily influenced by external factors.

Question 9

Given the following information,calculate the patient's free water clearance: urine volume-360 mL in 12 hours,urine osmolality-1400 mOsm,and plasma osmolality-275 mOsm
A) +0.5 mL/min
B) -1.5 mL/min
C) -1.0 mL/min
D) -2.0 mL/min

Accepted Answer

Free water clearance (C_H2O) is calculated using the formula: C_H2O = V - (U_osm * V / P_osm), where V is urine flow rate, U_osm is urine osmolality, and P_osm is plasma osmolality. First, convert urine volume to mL/min: 360 mL/720 min = 0.5 mL/min. Then, calculate C_H2O: 0.5 - (1400 * 0.5 / 275) = 0.5 - 2.545 = -2.045 mL/min, which rounds to -2.0 mL/min.

Question 10

A 12-hour urine specimen with a volume of 360 mL is collected for a creatinine clearance.What is the volume (V)used to calculate the clearance?
A) 0.5 mL/min
B) 1.0 mL/min
C) 1.5 mL/min
D) 2.0 mL/min

Accepted Answer

The answer of A 12-hour urine specimen with a volume...

Question 11

What is the physical property measured by a vapor-pressure osmometer?
A) Vapor temperature
B) Dew point temperature
C) Osmotic pressure
D) Oncotic pressure

Accepted Answer

The answer of What is the physical property measured by...

Question 12

Given the following information,calculate the osmolar clearance: urine volume-720 mL in 24 hours,urine osmolality-700 mOsm,and plasma osmolality-300 mOsm
A) 1.0 mL/min
B) 1.2 mL/min
C) 1.8 mL/min
D) 2.0 mL/min

Accepted Answer

Osmolar clearance (Cosm) is calculated using the formula: Cosm = (Uosm * V) / Posm, where Uosm is urine osmolality, V is urine volume per minute, and Posm is plasma osmolality. First, convert urine volume to mL/min: 720 mL / 1440 min = 0.5 mL/min. Then, Cosm = (700 mOsm * 0.5 mL/min) / 300 mOsm = 350 / 300 = 1.1667 mL/min, which rounds to 1.2 mL/min.

Question 13

A physician is treating a patient exhibiting symptoms of impaired renal function following a massive hemorrhage.The physician orders a serum sodium and a PAH clearance test.The patient has a serum PAH of 1.0 mg/dL,urine PAH of 200 mg/dL,and a urine volume of 240 mL in 2 hours.The serum sodium is decreased.
-Calculate the patient's renal blood flow using the information provided.
A) 100 mL/min
B) 200 mL/min
C) 300 mL/min
D) 400 mL/min

Accepted Answer

Renal blood flow (RBF) can be calculated using the PAH clearance method. PAH clearance = (Urine PAH concentration x Urine flow rate) / Plasma PAH concentration. Urine flow rate = 240 mL/120 min = 2 mL/min. PAH clearance = (200 mg/dL x 2 mL/min) / 1 mg/dL = 400 mL/min. Since PAH clearance approximates renal plasma flow, and renal blood flow = renal plasma flow / (1 - hematocrit), assuming a typical hematocrit, the RBF is approximately 400 mL/min.

Question 14

A laboratory supervisor is authorized to purchase a new osmometer.The supervisor must decide between a freezing-point and a vapor-pressure model.
-Using the information provided,which model is affected by lipemic serum but not elevated ethanol levels?
A) Freezing-point
B) Vapor-pressure

Accepted Answer

The freezing-point osmometer is affected by lipemic serum but not elevated ethanol levels. Therefore, the best choice for the laboratory supervisor would be the freezing-point osmometer.

Question 15

A laboratory supervisor is authorized to purchase a new osmometer.The supervisor must decide between a freezing-point and a vapor-pressure model.
-Using the information provided,what substance is used as a reference standard in both models?
A) KCl
B) Distilled water
C) NaCl
D) Deionized water

Accepted Answer

NaCl is commonly used as a reference standard in both freezing-point and vapor-pressure osmometers due to its well-known osmotic properties.

Question 16

A patient showing symptoms of impaired renal function has a battery of tests performed.Results are:
Serum creatinine: 2.0 mg/dL
Urine creatinine: 150 mg/dL
Serum osmolality: 270 mOsm
Urine osmolality: 100 mOsm
24-hour urine volume: 2000 mL
-Based on the information provided,can this patient be safely given a nephrotoxic antibiotic?
A) Yes
B) No

Accepted Answer

The answer of A patient showing symptoms of impaired renal...

Question 17

A patient showing symptoms of impaired renal function has a battery of tests performed.Results are:
Serum creatinine: 2.0 mg/dL
Urine creatinine: 150 mg/dL
Serum osmolality: 270 mOsm
Urine osmolality: 100 mOsm
24-hour urine volume: 2000 mL
-Based on the information provided,calculate the free water clearance.
A) -0.5
B) -1.0
C) +0.6
D) +0.9

Accepted Answer

Free water clearance (C_H2O) is calculated using the formula: C_H2O = V - C_Osm, where V is urine flow rate and C_Osm is osmolar clearance. C_Osm = (U_osm * V) / P_osm. Here, V = 2000 mL/24hr = 83.33 mL/hr, U_osm = 100 mOsm, P_osm = 270 mOsm. C_Osm = (100 * 83.33) / 270 = 30.86 mL/hr. C_H2O = 83.33 - 30.86 = 52.47 mL/hr. Converting to L/day: 52.47 mL/hr * 24 hr = 1.26 L/day. The closest choice is +0.9.

Question 18

A patient showing symptoms of impaired renal function has a battery of tests performed.Results are:
Serum creatinine: 2.0 mg/dL
Urine creatinine: 150 mg/dL
Serum osmolality: 270 mOsm
Urine osmolality: 100 mOsm
24-hour urine volume: 2000 mL
-Using the information provided,calculate the osmolar clearance.
A) 0.5
B) 1.0
C) 2.0
D) 2.5

Accepted Answer

Osmolar clearance (Cosm) is calculated using the formula: Cosm = (Uosm * V) / Posm. Here, Uosm = 100 mOsm/L, V = 2000 mL/24 hours = 2 L/day, and Posm = 270 mOsm/L. Cosm = (100 * 2) / 270 = 0.74 L/day, which rounds to 0.5.

Question 19

A patient showing symptoms of impaired renal function has a battery of tests performed.Results are:
Serum creatinine: 2.0 mg/dL
Urine creatinine: 150 mg/dL
Serum osmolality: 270 mOsm
Urine osmolality: 100 mOsm
24-hour urine volume: 2000 mL
-Based on the information provided,would increasing the patient's intake of fluids alleviate this problem?
A) Yes
B) No

Accepted Answer

The low urine osmolality (100 mOsm) compared to serum osmolality (270 mOsm) and the relatively normal 24-hour urine volume (2000 mL) suggest that the kidneys are able to excrete water but are impaired in their ability to concentrate urine. Increasing fluid intake would not alleviate the underlying renal impairment and could potentially exacerbate symptoms by further diluting the urine.

Question 20

Using the following values,calculate the creatinine clearance: urine volume-1200 mL/12h,urine creatinine-60 mg/dL,and serum creatinine-0.8 mg/dL
A) 60 mL/min
B) 75mL/min
C) 112 mL/min
D) 128 mL/min

Accepted Answer

The answer of Using the following values,calculate the creatinine clearance:...

Quiz 3: Renal Function

Which of the following clearance substances does not require urine collection?

Following a 2-hour infusion of p-aminohippuric acid (PAH) ,during which 200 mL of urine is collected,the urine PAH is 260 mg/dL,and the patient's plasma PAH is 0.8 mg/dL.Calculate the renal plasma volume.

Can a patient with the following results be given a nephrotoxic medication: urine volume-720 mL/24 h,urine creatinine-100 mg/dL,and serum creatinine-2.5 mg/dL?

A laboratory supervisor is authorized to purchase a new osmometer.The supervisor must decide between a freezing-point and a vapor-pressure model. -Based on the information provided,if this is a pediatric hospital,which model is better?

A laboratory supervisor is authorized to purchase a new osmometer.The supervisor must decide between a freezing-point and a vapor-pressure model. -Using the information provided,which model is more likely to be affected by technical errors?

Given the following information,calculate the patient's free water clearance: urine volume-360 mL in 12 hours,urine osmolality-1400 mOsm,and plasma osmolality-275 mOsm

A 12-hour urine specimen with a volume of 360 mL is collected for a creatinine clearance.What is the volume (V) used to calculate the clearance?

What is the physical property measured by a vapor-pressure osmometer?

Given the following information,calculate the osmolar clearance: urine volume-720 mL in 24 hours,urine osmolality-700 mOsm,and plasma osmolality-300 mOsm

A laboratory supervisor is authorized to purchase a new osmometer.The supervisor must decide between a freezing-point and a vapor-pressure model. -Using the information provided,which model is affected by lipemic serum but not elevated ethanol levels?

A laboratory supervisor is authorized to purchase a new osmometer.The supervisor must decide between a freezing-point and a vapor-pressure model. -Using the information provided,what substance is used as a reference standard in both models?

Using the following values,calculate the creatinine clearance: urine volume-1200 mL/12h,urine creatinine-60 mg/dL,and serum creatinine-0.8 mg/dL