B5.078 Ureteral Obstruction

Question 1

normal pathway of urine from formation to excretion?

Answer 1

glomerulus > PCT > loop of henle > DCT > collecting duct > minor calyx > major calyx > renal pelvis > bladder > urethra

Question 2

variation in presentation of urinary obstruction

Answer 2

can be permanent if not treated
congenital or acquired
acute or chronic
unilateral or bilateral

Question 3

what is hydronephrosis

Answer 3

dilated renal pelvis, calix, or ureter
can be present without obstruction
need radiologic findings to confirm

Question 4

typical symptoms of acute obstruction

Answer 4

flank pain secondary to stretch of renal collecting system
nausea/vomiting
anuria- severe and urgent issue

Question 5

lab studies for diagnosis of obstruction

Answer 5

UA
BMP (can assess renal fxn)
fractional excretion of Na+
GFR calculated for you

Question 6

what can fractional excretion of Na+ tell you about obstructive symptoms

Answer 6

prerenal <1%
intrarenal
post renal >4%

Question 7

main 2 imaging modalities for urinary obstruction

Answer 7

US and CT

Question 8

pros and cons of US

Answer 8

first line modality
widely available, cheap, no radiation, no contrast
can visualize hydronephrosis, but can not necessarily see obstruction (can’t prove w ultrasound alone)
can’t see ureters well

Question 9

pros and cons of CT

Answer 9

great anatomic detail
fast, accurate, safe
high sens for most calculi
limited in seeing obstructive processes that aren’t stones (tumors and strictures): need to use 3 phase CT, urogram

Question 10

excretory radiography

Answer 10

used in developing countries without CT available

single plate films sequentially (5 min intervals)

Question 11

retrograde/anterograde pyelography

Answer 11

injection of contrast into renal system to determine site of obstruction
commonly done in surgery

Question 12

Whitaker test

Answer 12

very invasive
percutaneous nephrostomy, tests pressures along urinary tract
rarely performed

Question 13

change in GFR with unilateral urinary obstruction

Answer 13

acute: GFR preserved

mid/late: GFR declines

Question 14

change in GFR with bilateral urinary obstruction

Answer 14

GFR immediately decreases and persists until fixed

Question 15

path of damage in obstruction

Answer 15

pressure form obstruction moves distal to proximal

glomerulus is the last impacted structure, most preserved

Question 16

effects of severe obstruction

Answer 16

urine produced will exit renal pelvis by lymphatic/venous drainage
impacts tubular function (poor concentrating ability)
as obstruction progresses, AQPs are down regulated so urine is not concentrated

Question 17

2 types of post obstructive diuresis

Answer 17

1. physiological: elimination of excess free water and solutes that have accumulated
2. pathological: loss of renal concentrating ability due to down regulation of AQP and Na+ channels

Question 18

impact of pathological post obstructive diuresis

Answer 18

sodium transport decreases
salt wasting
concentrating defects
deficit in ability to acidify urine
Mg2+ excretion markedly increased

Question 19

gross appearance of kidney after 2 days of obstruction

Answer 19

dilation of collecting system
blunting of papilla tips
increased weight due to edema
thinning of kidney parenchyma due to increased dilations
large cystic appearance w weight loss due to loss of renal tissue

Question 20

microscopic appearance of kidney after 2 days of obstruction

Answer 20

tubulointerstitial effects
dilation of tubules
fibrosis, inflammatory cells, apoptosis
glomerulosclerosis over time due to hyperfiltration injury/chronic inflammation

Question 21

clinical impacts after 2 days of obstruction

Answer 21

HTN (upregulation of RAA)

relief of block and blocking angiotensin 2 receptors will help combat rise in BP

Question 22

clinical impacts of chronic obstruction

Answer 22

compensatory growth in other kidney

increase due to cell hypertrophy, not hyperplasia (no more nephrons)

Question 23

first step in treatment of renal stones

Answer 23

pain management, symptom control

Question 24

how is pain managed in renal stones

Answer 24

opioids first line: rapid onset
NSAIDs for renal colic pain, but don’t use for people with compromised renal fxn
hydration

Question 25

when do you need to drain a kidney due to a stone?

Answer 25

evidence of infection: fever, leukocytosis, UA findings, imaging consistent with infection
won’t treat stone, but will drain infection
place ureteral stent or tube in OR

Question 26

how do you treat a renal stone itself?

Answer 26

lithotripsy: breaks down stone

Question 27

treatment of congenital causes of urinary obstruction

Answer 27

reconstruction or endolypotomy
endolypotomy: scope up the ureter, lateral cut at point of obstruction, place stent to allow ureter to heal around it to increase caliber

Question 28

what if a kidney has <10% function due to obstruction?

Answer 28

remove it, won’t survive on its own

Question 29

symptoms of pathologic post obstructive diuresis

Answer 29

edema, CHF, HTN

Question 30

who gets pathologic post obstructive diuresis

Answer 30

bilateral obstructions
older men
chronic renal retention

Question 31

treatment of pathologic post obstructive diuresis

Answer 31

normal renal fxn, normal mental state: free access to oral fluids
altered mental status: IV fluids at rate below maintenance, excess loss supplemented with repletion of electrolytes as needed