Obstruction Physiology

Question 1

Unilateral ureteral obstruction

Answer 1

Decreased cortical perfusion (glomeruli), increased flow to medulla. Renal blood flow and ureteral first rise, then fall.

Question 2

Bilateral ureteral obstruction

Answer 2

Increased cortical perfusion and decreased medullary perfusion (opposite of unilateral 2/2 buildup of vasoactive substances such as ANP)

Question 3

Post-obstructive diuresis

Answer 3

Occurs after release of bilateral ureteral obstruction, 3-10x increase in urine production; pathologic if kidneys excrete salt and water in excess of that retained during the obstruction

Question 4

Post-obstructive diuresis mechanisms

Answer 4

1) Impaired sodium reabsorption due to tubular damage
2) Impaired urinary concentration ability
3) Solute diuresis due to excretion of retained urea
4) Presence of a circulating natriuretic factor (ANP)

Question 5

Post-obstructive diuresis treatment

Answer 5

Give access to free fluids, if unable to drink give fluids at less than maintenence rate; monitor electrolytes