Urinary tract obstruction

Question 1

common causes of UT obstruction

Answer 1

prostatic obstruction
gynaecological cancer and calculi 
inflammatory (TB, infec)
Congenital (cysts)
Neoplastic

Question 2

clinical features upper urinary tract obstruction

Answer 2

dull ache in the flank or loin - provoked by inc in urine volume

complete anuria = strongly suggestive of complete bilateral obstruction

partial obstruction = polyuria as a result of tubular damage and impairment of concentrating mechanisms

Question 3

clinical features bladder outlet obstruction

Answer 3

hesitancy
poor stream
terminal dribbling
sense of incomplete emptying
retention with overflow is characterised by the frequent passage of small quantities of urine
infection usually occurs

Question 4

what might be found on examination in UT obstruction

Answer 4

enlarged bladder or hydronephrotic kidney

pelvic (for malignancy) and rectal (for prostate) exam is essential in determining the cause of obstruction

Question 5

investigations UT obstruction

Answer 5

USS and spiral CT to look at site of obstruction

Question 6

management UT obstruction

Answer 6

surgery if persistent

sometimes definitive relief of obstruction not poss = catheter needed

Question 7

what might happen after elimination of the obstruction

Answer 7

a massive post op diuresis (lots of wee), resulting partly from a solute diuresis from salt and urea retained during obstruction & partly from the renal concentrating defect

Question 8

obstructive uropathy

Answer 8

functional or anatomical obstruction of urine flow at any level of the urinary tract

Question 9

supravesical obstruction

Answer 9

above the level of the bladder

Question 10

infravesical obstruction

Answer 10

below the level of the bladder

Question 11

haemodynamic changes with unilateral ureteral occlusion

Answer 11

1. inc in RBF and hydraulic pressure of fluid in the tubule & collecting system pressure for first 1-2hr
2. 3-4h pressures remain elevated by RBF declines
3. 5h further RBF decline and dec in pressure

Question 12

haemodynamic changes with bilateral ureteral occlusion

Answer 12

small inc in RBF for 90min followed by profound dec
accumulation of vasoactive substances = preglomerular vasodilation and post glomerular vasoconstriction
when obstruction released GFR an RBF remain depressed due to persistent vasoconstriction of afferent arteriole
= post op diuresis (bigger in BUO than UUO)

Question 13

effects of obstruction on tubular function

Answer 13

dysregulation of aquaporin channels = polyuria & impaired concentrating capacity
sodium transport decreased = post obstructed kidneys impaired ability to concentrate and dilute urine

Question 14

sequelae from obstruction

Answer 14

release of angiotensin 2, cytokines and growth factors = changes to kidney
tubulointerstitial fibrosis
tubular atrophy and apoptosis
interstitial inflammation