Glomerular filtration Practice Questions

Question 1

Which region of the nephron reabsorbs the highest percentage of filtered bicarbonate?

Accepted Answer

Proximal tubule

Answer

Collecting duct

Answer

Thick ascending limb

Answer

Distal tubule

Question 2

A healthy 30-year-old female has a measured creatinine clearance of 100 mL/min. She has a filtration fraction (FF) of 25%. Serum analysis reveals a creatinine level of 0.9 mg/dL and an elevated hematocrit of 0.6. Which of the following is the best estimate of this patient’s renal blood flow?

Accepted Answer

1.0 L/min

Answer

1.2 L/min

Answer

600 mL/min

Answer

800 mL/min

Answer

400 mL/min

Question 3

A patient is receiving daily administrations of Compound X. Compound X is freely filtered in the glomeruli and undergoes net secretion in the renal tubules. The majority of this tubular secretion occurs in the proximal tubule. Additional information regarding this patient's renal function and the renal processing of Compound X is included below:

Inulin clearance: 120 mL/min
Plasma concentration of Inulin: 1 mg/mL
PAH clearance: 600 mL/min
Plasma concentration of PAH: 0.2 mg/mL
Total Tubular Secretion of Compound X: 60 mg/min
Net Renal Excretion of Compound X: 300 mg/min

Which of the following is the best estimate of the plasma concentration of Compound X in this patient?

Accepted Answer

2 mg/mL

Answer

3 mg/mL

Answer

There is insufficient information available to estimate the plasma concentration of Compound X

Answer

1 mg/mL

Answer

0.5 mg/mL

Question 4

On cardiology service rounds, your team sees a patient admitted with an acute congestive heart failure exacerbation. In congestive heart failure, decreased cardiac function leads to decreased renal perfusion, which eventually leads to excess volume retention. To test your knowledge of physiology, your attending asks you which segment of the nephron is responsible for the majority of water absorption. Which of the following is a correct pairing of the segment of the nephron that reabsorbs the majority of all filtered water with the means by which that segment absorbs water?

Accepted Answer

Proximal convoluted tubule via passive diffusion following ion reabsorption

Answer

Distal convoluted tubule via passive diffusion following ion reabsorption

Answer

Distal convoluted tubule via aquaporin channels

Answer

Thick ascending loop of Henle via passive diffusion following ion reabsorption

Answer

Collecting duct via aquaporin channels

Question 5

A scientist is studying the excretion of a novel toxin X by the kidney in order to understand the dynamics of this new substance. He discovers that this new toxin X has a clearance that is half that of inulin in a particular patient. This patient's filtration fraction is 20% and his para-aminohippuric acid (PAH) dynamics are as follows:

Urine volume: 100 mL/min
Urine PAH concentration: 30 mg/mL
Plasma PAH concentration: 5 mg/mL

Given these findings, what is the clearance of the novel toxin X?

Accepted Answer

60 mL/min

Answer

1,500 mL/min

Answer

600 mL/min

Answer

300 mL/min

Answer

120 mL/min

Question 6

A 73-year-old male is brought in by ambulance after he was found to be lethargic and confused. He has not been routinely seeing a physician and is unable to recall how he came to be in the hospital. His temperature is 99°F (37°C), blood pressure is 150/95 mmHg, pulse is 75/min, and respirations are 18/min. His past medical history is significant for poorly controlled diabetes and longstanding hypertension, and he says that he has not been taking his medications recently. Labs are obtained and shown below:

Serum:
Na+: 142 mEq/L
Cl-: 105 mEq/L
K+: 5 mEq/L
HCO3-: 16 mEq/L
Urea nitrogen: 51 mg/dL
Glucose: 224 mg/dL
Creatinine: 2.6 mg/dL

Which of the following changes would most likely improve the abnormal parameter that is responsible for this patient's symptoms?

Accepted Answer

Increased glomerular capillary hydrostatic pressure

Answer

Increased Bowman's space hydrostatic pressure

Answer

Decreased filtration coefficient

Answer

Increased Bowman's space oncotic pressure

Answer

Decreased glomerular capillary hydrostatic pressure

Question 7

A 58-year-old man presents to the Emergency Department after 3 hours of intense suprapubic pain associated with inability to urinate for the past day or two. His medical history is relevant for benign prostatic hyperplasia (BPH) that has been under treatment with prazosin and tadalafil. Upon admission, he is found to have a blood pressure of 180/100 mm Hg, a pulse of 80/min, a respiratory rate of 23/min, and a temperature of 36.5°C (97.7°F). He weighs 84 kg (185.1 lb) and is 175 cm (5 ft 7 in) tall. Physical exam, he has suprapubic tenderness. A bladder scan reveals 700 ml of urine. A Foley catheter is inserted and the urine is drained.  Initial laboratory tests and their follow up 8 hours after admission are shown below.
Admission 8 hours after admission
Serum potassium 4.2 mmol/L Serum potassium 4.0 mmol/L
Serum sodium 140 mmol/L Serum sodium 142 mmol/L
Serum chloride 102 mmol/L Serum chloride 110 mmol/L
Serum creatinine 1.4 mg/dL Serum creatinine 1.6 mg/dL
Serum blood urea nitrogen 64 mg/dL Serum blood urea nitrogen 62 mg/dL
Urine output 250 mL Urine output 260 mL
A senior attending suggests a consultation with Nephrology. Which of the following best justifies this suggestion?

Accepted Answer

Urine output

Answer

Estimated glomerular filtration rate (eGFR)

Answer

Serum creatinine (SCr)

Answer

Serum blood urea nitrogen (BUN)

Answer

Serum potassium

Question 8

A researcher is investigating the effects of a new antihypertensive medication on renal physiology. She gives a subject a dose of the new medication, and she then collects plasma and urine samples. She finds the following: Hematocrit: 40%; Serum creatinine: 0.0125 mg/mL; Urine creatinine: 1.25 mg/mL. Urinary output is 1 mL/min. Renal blood flow is 1 L/min. Based on the above information and approximating that the creatinine clearance is equal to the GFR, what answer best approximates filtration fraction in this case?

Accepted Answer

17%

Answer

10%

Answer

33%

Answer

50%

Answer

25%

Question 9

A 48-year-old woman comes to the physician for a follow-up examination. At her visit 1 month ago, her glomerular filtration rate (GFR) was 100 mL/min/1.73 m2 and her renal plasma flow (RPF) was 588 mL/min. Today, her RPF is 540 mL/min and her filtration fraction (FF) is 0.2. After her previous appointment, this patient was most likely started on a drug that has which of the following effects?

Accepted Answer

Constriction of the efferent arteriole

Answer

Inhibition of the renal Na-K-Cl cotransporter

Answer

Constriction of the afferent arteriole

Answer

Relaxation of urinary smooth muscle

Answer

Inhibition of vasopressin

Question 10

A 75-year-old woman is brought to a physician’s office by her son with complaints of diarrhea and vomiting for 1 day. Her stool is loose, watery, and yellow-colored, while her vomitus contains partially digested food particles. She denies having blood or mucus in her stools and vomitus. Since the onset of her symptoms, she has not had anything to eat and her son adds that she is unable to tolerate fluids. The past medical history is unremarkable and she does not take any medications regularly. The pulse is 115/min, the respiratory rate is 16/min, the blood pressure is 100/60 mm Hg, and the temperature is 37.0°C (98.6°F). The physical examination shows dry mucous membranes and slightly sunken eyes. The abdomen is soft and non-tender. Which of the following physiologic changes in glomerular filtration rate (GFR), renal plasma flow (RPF), and filtration fraction (FF) are expected?

Accepted Answer

Decreased GFR, decreased RPF, increased FF

Answer

Decreased GFR, decreased RPF, decreased FF

Answer

Decreased GFR, decreased RPF, no change in FF

Answer

Increased GFR, increased RPF, increased FF

Answer

Increased GFR, decreased RPF, increased FF

Glomerular filtration

Study Resources

Lessons

Questions

Flashcards

Lessons

Glomerular structure and function

Filtration barrier components

Determinants of GFR

Starling forces in glomerular filtration

Renal blood flow autoregulation

Filtration fraction

GFR measurement methods

Tubuloglomerular feedback

Myogenic autoregulation

Hormonal influences on GFR

GFR in pathophysiological states

Age-related changes in GFR

Clinical estimation of GFR

Practice Questions

Flashcards

About Glomerular filtration for USMLE

Lessons in Glomerular filtration

Master Glomerular filtration