Renal

Question 1

What is the formula for bladder volume? In what view is this measured?

Answer 1

Urinary bladder volume = length x width x height x 0.2π

Obtained in the lateral cysto-colic view

Further validation is warranted given small sample size and use of balloons

Question 2

What are free catch alternatives to measuring urine output?

Answer 2

1. Metabolic cages
2. Collection pans
3. Absorbent pads

Question 3

What are the determinants of urine output?

Answer 3

1. Glomerular filtration rate
2. Tubular Reabsorption of water and solutes
3. Impedance to flow

Question 4

What is glomerular filtration rate?

Answer 4

The volume of fluid filtered from the
kidney’s glomerular capillaries into the Bowman capsule per unit time

Question 5

What are the determinants of GFR?

Answer 5

1. Hydrostatic pressure
2. Colloid osmotic forces
3. Permeability of membrane
4. Surface area of membrane

Question 6

At what blood pressures does renal autoregulation maintain a relatively constant renal blood flow?

Answer 6

Mean arterial blood pressures between 80 and 180 mm Hg, autoregulation main-
tains relatively constant renal blood flow, and therefore constant GFR.

Question 7

What mechanisms occur in the kidney when BP falls below 80mmHg MAP?

Answer 7

Decreased renal blood flow –> decreased GFR –> decrease urine output.

Decreased baroreceptor stimulation in response to hypotension and hypovolemia, increases sympathetic input to the kidneys and circulating catecholamine and angiotensin II levels.
These mediators cause renal arteriolar constriction, which further decreases renal blood flow and GFR in an effort to conserve blood volume.