Renal Physiology

Question 1

What is the function of Kidney’s?

Answer 1

• fluid + osmotic balance
• excretion of waste products
• blood manufacture
• acid/base metabolism
• blood pressure
• electrolyte metabolism
• gluconeogenesis

Question 2

Approximate the body’s fluid compartments

Answer 2

60% water
1/3 EC fluid
2/3 IC fluid

Question 3

What is the GFR?

Answer 3

Volume of flayed filtered by glomerular capillaries per unit time = rate at which substances cleared from plasma

GFR = Kf x net filtration pressure

Question 4

What is Kf determined by?

Answer 4

• hydraulic properties

- SA

Question 5

How is net filtration pressure calculated?

Answer 5

Glomerular hydrostatic pressure - Bowman’s capsule pressure - Glomerular oncotic pressure

Question 6

What is the GFR determined by?

Answer 6

• hydrostatic pressure
• oncotic pressure
• properties of barrier

Question 7

What does declining GFR imply?

Answer 7

Progression of disease process or reversible problem such as reduced renal perfusion

Question 8

How is GFR measured?

Answer 8

• look at urinary clearance of ideal marker = insulin

- ideal marker = freely filtered at glomerulus, non-toxic, neither secreted or absorbed by kidney

Question 9

Why is plasma creatinine used to measure renal function?

Answer 9

• derived from skeletal muscle
• released at constant rate
• freely filtered
• not reabsorbed/metabolised
• some secretion in PT
• overestimation of GFR when using creatinine clearance

Question 10

When is plasma creatinine constant?

Answer 10

If GFR, nephrons, diet + muscle mass all constant

Question 11

What is the relationship between GFR and Creatinine?

Answer 11

As GFR drops, creatinine rises (hence can use creatinine to estimate GFR)

Question 12

What is the MDRD equation?

Answer 12

• used in Wales
• 4 variables: age, gender, creatinine + ethnicity
• gives more accurate GFR
• not accurate estimates when GFR changing rapidly
• performs well at mid-range GFR but less well at high GFR

Question 13

What are the classical sites for UTI?

Answer 13

Kidney

• acute pyelonephritis
• cortical abscess
• perinephric abscess
• pyonephrosis
• renal calculi

Ureter - urethritis

Bladder - cystitis

Urine - bacteria

Prostate - prostatitis

Urethra - urethritis

Question 14

What are the symptoms of acute pyelonephritis?

Answer 14

• fever
• malaise
• nausea
• vomiting
• abdominal/loin pain

Question 15

What is are the symptoms of pyonephrosis/perinephric abscess?

Answer 15

• riggers
• loin pain
• scoliosis
• loin swelling
• weight loss
• night sweats

Question 16

What are the symptoms of lower tract infections?

Answer 16

• dysuria
• frequency
• haematuria
• nocturia
• suprapubic pain
• urgency
• foul urine

Question 17

What is a vesio-ureteric reflux?

Answer 17

Due to cystoureteric valve incompetence = back flow of infected urine to kidney = acute pyelonephritis = kidney scarring + CKD

Question 18

What is the difference between primary and secondary VUR?

Answer 18

Primary

• most common
• incompetent ureterovesical junction
• shortening of intravesical ureter
• spontaneous resolution with growth

Secondary

• high pressure bladder
• dysfunctional voiding or neurogenic bladder