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review course > Stones > Flashcards

Stones Flashcards

1
Q

2 basic ways ESWL breaks stones

A
  1. cavitation and 2. direct stress (comprssive and shear)
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2
Q

at what point does cavitation have its effect

A

negative portion of pressure wave

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3
Q

at what point does direct stress have its effect

A

positive portion of pressure wave

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4
Q

cavitation in eswl and tissue injury

A

formation of microbubbles in renal tissue parenchyma/blood vessels proposed as mediator of ESWL induced tissue injury

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5
Q

absolute contraindications to ESWL - 5

A

pregnancy, coagulopathy, distal obstruction, calcified renal artery aneurism, untreated UTI

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6
Q

if cant correct coagulopathy/ stop antiplatelet - stone tx of choice

A

URS

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7
Q

what is max skin to stone distance and where is this applicable

A

< 10 cm on axial CT as MEAN distance at 0,45,90 deg in obese people

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8
Q

BMI and ESWL

A

BMI is independent predictor of ESWL failure

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9
Q

SFR for 2 cm stone with ESWL

A

20%

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10
Q

stone hounsefield and ESWL success

A

> 1000 = inferior SFR rate

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11
Q

stone types that dont work in ESWL

A

CaOx monohydrate, cystine, brushite

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12
Q

infundibulopelvic angle and ESWL

A

> 70 is good

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13
Q

infundibular width and ESWL

A

< 5 mm is good

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14
Q

infundibular length and ESWL

A

> 3 cm is good

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15
Q

ESWL machine with higher perinephric hematoma rate

A

SLX-F2 (3%)

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16
Q

RF’s for bleeding - 4

A

DM, HTN, obesity, coagulopathy

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17
Q

mechanical percussion and inversion

A

helps in SFR after ESWL

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18
Q

alpha blockers after ESWL

A

helps in SFR after ESWL, and pain

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19
Q

when to place stent prior to ESWL - 2

A

large stone burden with steinstrasse risk, high grade obstruction

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20
Q

ideal shock wave rate

A

60/min= higher stone clearance/reduce retreatment

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21
Q

stricture rate for URS

A

2%

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22
Q

ureteral perforation rate for urs

A

5%

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23
Q

why get renal access to calyx end-on vs side-on

A

end on have lower risk of hitting interlobular arteries which cross infundibula

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24
Q

4 indications for PCNL other than stone > 2 cm

A

lower pole stone > 1 cm, cystine stone, pts who must be stone free (pilots), anatomic abnormalities

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25
Q

location of ideal calyx for PCNL access

A

upper pole calyx eventhough there is risk of pulm complications

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26
Q

absolute indications for tube after pcnl besides stones - 5

A

significant collecting system inj, excessive hemorrhage, multiple tracts, pyonephrosis

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27
Q

hydrothorax rate for PCNL

A

2%

28
Q

prone considerations in anesthesia for obese pts - 2

A

reduced total lung capacity and FRC w abd compression, IVC compression with reduced preload and impaired oxygenation

29
Q

ways to overcome anesthesia considerations for obese patients - 3

A
  1. lateral decubitus and supine positioning, 2. awake endotracheal intubation and self positioning, 3. PCNL under local anesthesia and sedation.
30
Q

indications for PCNL - 7

A

> 2 cm stone, staghorn, lower pole > 1 cm, cystine stone, pts who must be stone free (pilots), failure of other treatments, assd anatomical abnormalites

31
Q

3 differences in pcnl outcome in obese patients

A
  1. longer operative time, 2. decreased SFR, 3. significantly higher retreatment rate
32
Q

problem with stent/nephrostomy during pregnancy

A

increased # procedures due to encrustation and pain

33
Q

ureteroscopy in obese patients

A

equal outcome to non-obese

34
Q

imaging for stones in pregant females

A

can do ultra low does ct - not associated with fetal or maternal harm

35
Q

stone passage and location at dx

A

20% @ prox ureter, 70% @ diatal ureter

36
Q

who gets expectant mgmt of stone

A

< 10 mm and well controlled sx + periodic evaluation + medical therapy

37
Q

2 medical adjuncts

A

CCB (65% passage) and alpha blockers (55% passage)

38
Q

why alpha blocker

A

less side effects vs ccb

39
Q

how meds work in stones

A

stops ureteral spasm

40
Q

“indication” to ESWL

A

uncomplicated < 2 cm

41
Q

contraindications - 6

A
  1. bleeding problm, 2. preg, 3. aneurism (aortic > 5 cm, renal > 2 cm), 4. untx UTI, 5. obstruction distal to stone, 6. inability to visualize stone
42
Q

4 effects of ESWL on stone

A
  1. spall, 2. cavitation, 3. squeezing aka sheer stress, 4. superfocusing
43
Q

what is squeezing/ sheer stress?

A

shock wave passes through stone faster than water resulting in acoustic mismatch and squeezing effect on surface

44
Q

what is superfocusing

A

as shock wave moves through stone (moves faster) wake of pressure forms behind shock wave and focus in mid stone.

45
Q

what is spall

A

Some energy is internally reflected into stone

46
Q

what is cavitation

A

negative pressure of shock wave creates cavitation bubble

47
Q

4 factors affecting ESWL outcome

A
  1. body habitus, 2. stone size, 3. stone location, 4. stone composition
48
Q

ideal skin to stone distance

A

< 10 cm ideal, >12 cm is bad

49
Q

how to determine skin to stone distance

A

PICTURE p.406

50
Q

stone free rate for 1, 1.5, 2 cm stone

A

80%, 72%, 60%

51
Q

J urol 2001, albala and woods - ESWL vs PCNL for lower pole stones

A

SWL 35%, PCNL 95% stone free

52
Q

stone density and ESWL success

A

hounsfield units suggest stone fragility - HU < 500 = 100% success, > 1000 = 50% success

53
Q

SWL attributes affecting stone fragmentation

A

acoustic output and focal volume

54
Q

focal zone vs focal point

A

focal point - acoustic energy focused to a point in space. Focal zone - zone of high pressure (50% focal point) around focal point. The latter varies by lithotriptors

55
Q

2 biggest effects on stone breakage

A

acoustic mismatch causing sheer stress and cavitation - both happen on SURFACE of stone

56
Q

effect of focal zone size on stone breakage

A

focal zone should include stone surface to expose stone to cavitation/sheer stress

57
Q

stone motion and focal zone

A

larger focal zone keeps stone exposed to shock wave during motion (breathing)

58
Q

4 physician controlled variables in SWL

A
  1. coupling, 2. rate, 3. anesthesia, 4. power
59
Q

what is coupling

A

joining pt to lithotriptor via medium (water bath, or jel)

60
Q

potential effect of coupling

A

air pockets can form at junction btw pt and coupler - more bubbles = poorer effect. 8% coverage by air pockets = 60% decrease breakage

61
Q

anesthesia effect on stone free rate

A

GETA 90% stone free, sedation 55%

62
Q

power effect on stone

A

shocks cause hematoma on kidney. pre-treatment with low energy shock waves can have protective effect on kidney - vasoconstrictive effect on kidney

63
Q

complications of SWL

A

hematoma, ureteral obstruction, delayed issues (DM/HTN)

64
Q

effect of SWL on HTN

A

dose dependent, and older ppl more suceptible

65
Q

indications for URS

A

unfavorable for SWL (HU >1000, lower pole), bleeding diathesis

66
Q

holmium stone breakage MOA

A

photothermal

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