Renal question bank

Renal
by Medical Educator Renal

Renal medicine, also known as nephrology, is a fascinating field of medicine that focuses on the study and treatment of kidney diseases. The kidneys play a vital role in maintaining the body’s fluid balance, regulating blood pressure, and filtering waste products from the blood. Medical students who delve into renal medicine will explore various aspects, including kidney anatomy, renal physiology, renal pathology, and the management of kidney disorders.

If you’re a medical student interested in expanding your knowledge of renal medicine, why not put your understanding to the test with our multiple choice questions? Our carefully curated questions cover a wide range of topics, from the basics of renal function to the diagnosis and treatment of specific renal conditions. Whether you’re preparing for an exam or simply want to challenge yourself, our multiple choice questions provide an engaging way to assess your knowledge and reinforce important concepts.

Table of Contents

Cause of CRF

What is the commonest cause of end stage renal failure in the UK?

  • Hypertension
  • Reflux Nephropathy
  • Glomerulonephritis of any cause
  • Adult polycystic Kidney disease
  • Diabetes Mellitus

Diabetes is still the commonest reason to be on dialysis in the UK.

Diabetes makes up for approximately 30% of the UK cases of CRF with the others being divided in into the other groups.

Common Causes of Chronic Renal Failure
Diabetes Mellitus
Hypertension

Glomerulonephritis of any cause

Adult polycystic Kidney disease

Reflux Nephropathy/ chronic infection
Glomerulonephritis of any cause

Creatine supplement

A 24 year old man with type 1 diabetes has his renal function measured routinely.

He tells you in the past 3 days he has been using the dietry supplement creatine, at the “maximum” dose.

What effect would you expect this to have on the standard lab measurement of his renal function?

  • No effect
  • Will underestimate true renal function
  • Will overestimate true renal function

Will underestimate true renal function.

Creatine is protine found in muscle. Its metabolised to creatinine.

Assuming creatine is absorbed and metabolised it is likely to raise his serum creatinine (although only by a small amount).*

AS such it will seem he has a higher serum creatinine, and therefore whatever measurement you use to measure his renal function (EGFR, Creatinine clearance/ U&E’s) it will underestimate his ‘true’ renal function,

*Dietary supplements in athletes
ACC Current Journal Review, Volume 11, Issue 1, January-February 2002

EGFR Bodybuilder

A 26 year old Afro-Caribbean bodybuilder presents following a routine medical with concerns about his renal function. The following are noted: weight 130kg height 172cm. BP 112/78 Urinalysis negative. Pulse 48 regular. PEFR 620 (NR>500). He is asymptomatic

Na134(135-145mmol/l)
K4.3(3.5-5.1mmol/l)
U4.3(4-9mmol/l)
Creatinine141(60-100 micromols/l)

What is the most likely explanation for his “abnormal blood tests”?

  • Normal for him
  • Lab error on creatinine measurement
  • Intrinsic renal disease
  • Drug associated renal disease
  • Infection associated renal disease

Normal for him

Creatinine is formed from the breakdown of muscle. It is used to estimate glomerular filtration by measuring the level in the bloodstream.

But…

Your serum creatinine will depend on your muscle mass. This can be difficult to measure but in a body builder with a BMI of >30 a modest increase increase in creatinine is normal. This means 2 things

A creatinine of 140 may be normal for a body builder.

A creatinine of 100 may be highly abnormal in a frail 82 year old woman with little muscle mass. It provides only a guide towards actual GFR.

Filtration

Which of the following statements is correct about renal filtration?

  • The afferent arteriole supplies blood to the glomerulous where it is filtered into the Bowman’s space then the filtrate passes into the proximal convoluted tubule
  • The efferent arteriole supplies blood to the glomerulous where it is filtered into the Bowman’s space then the filtrate passes into the proximal convoluted tubule
  • The efferent arteriole supplies blood to the glomerulous but is not the source of the blood which is actually filtered by the kidney
  • The afferent arteriole supplies blood to the glomerulous but is not the source of the blood which is actually filtered by the kidney

The afferent arteriole supplies blood to the glomerulous where it is filtered into the Bowman’s space then the filtrate passes into the proximal convoluted tubule.

Although the preclinical physiology knowledge has already been tested in preclinical exams, you will still be questioned on key aspects of physiology.

Remember the renal corpuscle constitutes the afferent arteriole and efferent arteriole. The filtrate passes into Bowman’s space. The efferent arteriole carries blood back through the renal vein.
proximal convoluted tubule to the ..
loop of henle to the..
distal convoluted tubule to the..
collecting duct

Glomerular filtration rate (GFR) quiz

Creatinine is commonly used to estimate glomerular filtration rates.
It is actually actively secreted by the kidney actively also.
Using this information when using creatinine to measure GFR would you expect it to:

  • Overestimate the GFR
  • Underestimate the GFR
  • The secretion would have no effect on the GFR measurement

Overestimate the GFR

What are the properties of an ideal substance used to estimate the glomerular filtration rate of the kidneys: i.e. the ml’s a minute of plasma the kidneys are filtering a minute. (normal=90-120ml/min)?

  • Completely freely filtered by kidney
  • >95% initial filtration by kidney
  • Minimal filtration by kidney (<5%)
  • Not filtration by the kidney
  • None of the answers listed here

Not filtration by the kidney

To measure the kideys filtration ideally you want a substance that is frely filtered by the kidney.

E.g. if there are 5 units of substance x in 100 ml of plasma that is filtered by the kidney, the ideal substance would freely filter completely from the plasma into the filtrate. I.e. all 5 units would filter out. (not 3 units or 4.8 units!)

What are the properties of an ideal substance used to estimate the glomerular filtration rate of the kindeys: i.e. the ml’s a minute of plasma the kidneys are filtering a minute. (normal=90-120ml/min)?

  • Substance completely reabsorbed by kidney following filtration
  • >95% reabsorbed following initial filtration by kidney but not completely reabsorbed
  • Minimal reabsorption by kidney (<5%)
  • No reabsorption by kidney
  • None of the answers listed here

No reabsorption by kidney

Continue this on from the previous question imagining the ideal substance used to measure GFR:
I.e. if there are 5 units of substance x in 100ml of plasma filtered by the kidney and all 5 units have been filtered into the filtrate. If the kidneys are reabsorbing this substance from the filtrate (e.g. 1.6 units reabsorbed in the loop of henle through active transport) then its not giving a true reflection of filtration: its giving a reflection of filtration and reabsorption.

Therefore the ideal substance would be freely filtered and not reabsorbed

What are the properties of an ideal substance used to estimate the glomerular filtration rate of the kindeys: i.e. the ml’s a minute of plasma the kidneys are filtering a minute. (normal=90-120ml/min)?

  • Highly actively secreted by the kidney
  • No active secretion
  • Minimal active secretion by kidney

If the kidneys are actively secreting the substance e.g. in the loop of henle then again any measurements will not be a simple measure of filtration, but a measure of filtration and active secretion.

Therefore the ideal substance for measuring glomerular filtration rate would be freely filtered, not reabsorbed, and not actively secreted by the kidney.

What are the properties of an ideal substance used to estimate the glomerular filtration rate of the kindeys: i.e. the ml’s a minute of plasma the kidneys are filtering a minute. (normal=90-120ml/min)?

  • Continuously produced at a steady state, by the kidney
  • Continuously produced at a steady state, not by the kidney
  • Diurnally produced, by the kidney
  • Diurnally produced, not by the kidney
  • None of the above answers

If you’re going to use a substance to measure kidney function it would be ideally produced at a constant level.

You want a substance that isn’t produced by the kidney! Imaging in acute renal failure: the kidney would not produce the substance and a “low level” would give false reassurance regarding the renal function.

Therefore the ideal substance for measuring glomerular filtration rate would be produced at a steady state by the body, freely filtered by the kidney, not reabsorbed, and not actively secreted by the kidney.

GFR formula

What equation would you use to estimate the creatinine clearance?
This is not a formula you are expected to memorise you can work it out from first principles

Creatinine Concentration serum= P (mg /ml)
Plasma Urine creatinine concentration= U (mg/ml)
Urine Flow rate =V (ml/ minute)

  • (U x V) / P
  • (U x P) / V
  • V x ( P / U)
  • U x V x P
  • P x (U / V)

Easy!

(U x V) / P

I.e. if you’re urine has 0.5mg/ml of creatinine and you’re making 1 ml minute of urine, then in 1 hour you will have filtered 30mg of creatinine out of the bloodstream.

If you know the serum concentration of the creatinine: then you can divide the number by P [ formula (U x V) / P] to get your creatinine clearance.

Measuring GFR

Which of the following substances is best placed to measure glomerular filtration rate?

  • Insulin
  • Inulin
  • Creatinine
  • Parathyroid hormone
  • Creatine

Inulin is a little unique! Inulin is a polysacchride freely filtered by the kidney but not reabsorbed. Its also not actively secreted thus giving it the ideal properties needed to measure GFR.

GFR formula practice

Using the formula (U x V) / P

Creatinine Concentration serum= P (mg /ml)
Plasma Urine creatinine concentration= U (mg/ml)
Urine Flow rate =V (ml/ minute)

If a patient passes 1.5l of urine in 24 hours and the total creatinine in the urine when measured is 2000mg then what is the correct way of calculating the creatinine clearance?

  • (2000x 1440)/ P
  • ((2000/1440) x (1500/1440)) / P
  • (2000) x (1500) / P
  • ((2000/24) x (1500/24)) / P
  • None of the listed answers are correct

((2000/1440) x (1500/1440)) / P

Remember your units!
U= mg per ml
So if you excrete a total of:
2000mg of urine in 24 hours, you’re excreting
2000/24 mg of rine in 1 hour or
2000/(24×60) mg of urine per minute
24×60=1440= the minutes in a day

Therefore you have to divide by 1440 for both U and V to get mg per minute and ml per minute respectively.

Anorexia case

A 36 year old presents with malaise/ lethargy anorexia and a 2 day history of fever and right loin pain. She has had no nause or vomiting.

Examination reveals the following positive findings:
Temperature 392
Non specific loin pain

Urinalysis shows the following

UrinalysisResult
Blood+++
Protein+++
Leukocytes–
Ketones+
glucose–

What is the most likely diagnosis from the following?

  • Pelvic inflammatory disease
  • Renal stone
  • Pyelonephritis
  • Urinary tract infection
  • Appendicitis

Pyelonephritis

Renal stones classically cause excruciating not insidious onset loin pain

Appendicitis is less likely than pyelonephritis (no nausea or vomiting)

Simple UTI’s do not cause loin pain

What is the significance of the ketones?

  • She is likely to have Type I diabetes mellitus
  • She is likely to have Type II diabetes mellitus
  • She has a metabolic acidosis
  • She has a lactic acidosis
  • None of the answers listed here

She has a metabolic acidosis

She has no glycosuria. Although it would be important to check her serum glucose its highly likely that the ketones simply reflect anorexia: i.e. not eating because of currant illness.

An ultrasound scan is shown which shows the a markedly dilated renal pelvis. What is the most likely diagnosis?

  • Pyelonephritis
  • Hydronephrosis
  • Renal abscess
  • Renal Cancer
  • None of the answers listed here

Hydronephrosis

A dilated renal collecting system suggests a hydronephrosis. This may be casued by any obstruction to the ureter,
e.g.
Stone
Cancer
Infiltration

Nephrotic syndrome

A patient has suspected nephrotic syndrome. The patient goes on to have a 24 hour urine collection.
What is the cut off for urinary protein in a 24 hour period?
Please select the most accurate answer:

  • >5g 24 hours
  • >3g in 24 hours
  • >500mg in 24 hours
  • >50mg in 24 hours
  • None of the above listed answers

3g in 24 hours

Nephrotic range protienris is between 3 -3.5g in 24 hours.
Diagnosis is via a 24 hour protein colleciton
A “spot” albumin creatinine ration can be done on an MSU to give an idea of the 24 hour protein excretion but is less accurate.

Obstructive Uropathy

An 80 year old man from a nursing home (with dementia) presents with acute renal failure and non specific abdominal pain. A week ago his renal function was normal. His blood tests are as follows.

Na 147 (135-145)

K 4.1 (3.5-5.1)

U 20 (4-9)

Creatinine 396 (60-100)

Hb 11 (13-18)

Which of the following is most likely to identify a reversible cause for his renal failure?

  • Abdominal exam
  • Blood pressure
  • Urinalysis&MSU
  • Rectal exam
  • Blood glucose

Rectal exam

Although he may have a urinary tract infection the most likely reversible cause will be urinary retention caused by either:

1) faecal impaction and subsequent urethral obstruction

2) prostatic hypertrophy resulting in urethral obstruction

An abdominal exam may identify a palpable bladder caused by said obstruction, however it would not identify the cause of the obstruction.

Trimethoprim adverse effects

A patient is on long term nitrofuramtoin as prophylaxis against urinary tract infections. What adverse effect would you be concerned about?

  • Lung disease
  • Vascular disease
  • Skin disease
  • Renal disease
  • Gut disease

Lung disease

Nitrofuramtoin is associated with pulmonary fibrosis and lung injury. Other drugs that cause pulmonary fibrosis include:

Amiodarone

Bleomycin

Methotrexate.

This is of key importance in OSCE exams. You may be told: This patient takes trimethoprim for recurrent UTI’s: please examine the respiratory system. Always try to link the initial instruction with the clinical findings.

Which blood test measures EGFR

The normal glomerular filtration rate for the kidneys is 90-120ml/min.Which blood test is used to estimate the glomerular filtration rate?

  • Creatinine
  • Urea and creatinine
  • Creatinine and electrolytes
  • Creatinine and albumin
  • None of the answers listed here

Creatinine
To measure how much blood the kidneys have “filtered” you use the serum creatinine measurement. You do not need to know the other blood measurements.

PSA Test

A 55 year old man asks you for a PSA test as part of what he feels a “well man” check.
You wish to give him some more information about the PSA check
Is the following statement true or false?

“There is no national screening programme currently in the UK for prostate cancer.”

  • True
  • False

FALSE

There are trials ongoing regarding PSA testing as part of a screening programme. An excellent review is available at http://www.annals.org/cgi/content/full/149/3/192

Is the following statement true or false?

“If the PSA level is high even with a normal rectal examination we would recommend an ultrasound scan of the prostate and a prostatic biopsy”

  • True
  • False

FALSE

Current trial protocol use a PSA of> 3 micrograms/L. They then recommend USS and biopsy as neither tool on their has the required sensitivity.

Is the following statement true or false?

“the subsequent investigations following a high PSA carry an approximate 20% complication rate”

  • True
  • False

FALSE

TRUS (trans rectal ultrasound) and biopsy carry a 1-5% complication rate which include prostatitis/ bleeding and infection.

An excellent review is available here debating the benefits of testing. http://www.annals.org/cgi/content/full/149/3/192

Is the following statement true or false?

“a low normal PSA in the abscence of symptoms essentially excludes prostate cancer”

  • True
  • False

FALSE

Prostate cancer is the commonest non skin cancer in men.
30% of small prostate cancers will have a normal PSA
Therefore the absence of symptoms and a normal PSA do not rule out prostate cancer.