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General Sonography > Cervical Sonography > Flashcards

Cervical Sonography Flashcards

0
Q

Cervical canal/ cervical length

A

Cavity between the internal os and external os
Approximately 35mm in length

53 mm +- 12-13mm before 33 weeks gestation
(20-35 is cutoff)

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1
Q

Location of cervix

A

Extends from the inferior end of the uterus to the superior portion of the vagina

  • internal os
  • external os
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2
Q

Cervical division

A

Cervix divided into supra and infra vaginal segments

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3
Q

Blood supply of uterus

A

From uterine arteries

Uterine arteries become less resistant during pregnancy

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4
Q

Digital exam evaluation

A

Evaluates:

  • dilation of the external os
  • % effacement (cervical length shortens)
  • station of the presenting part
  • position of the cervix
  • consistency of the cervix
  • > for baby to come out, need 100% effacement (10cm dilation of the external os)
  • > cervix is soft before birth
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5
Q

Transabdominal pros

A
  • less invasive
  • less cumbersome (less difficult to do)
  • well accepted by the patient compared to transvaginal sonography
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6
Q

Transabdominal cons

A
  • poor visualization

- apparent artificial lengthening when maternal bladder is full

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7
Q

Transabdominal empty bladder

A

Overcomes bias of artificial lengthening of Transabdominal measurement with full bladder

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8
Q

Transperineal technique

A
  • maternal bladder empty
  • internal cervical so and upper cervical os routinely visualized
  • external os may be obscured by overlying bowel gas
  • put probe on top of labial flap, noninvasive
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9
Q

Pregnancy red flag

A

If cervix is shorter than 3 cm

If internal os appears to have a V or U shape

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10
Q

Transvaginal pros

A
  • reliable
  • reproducible
  • not affected by maternal obesity, cervix position, shadowing from fetus
  • may identify other US risk factors better : intramniotic debris, placenta previa, vasa previa
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11
Q

Transvaginal scan technique

A
  • insert probe in anterior fornix under direct real time vision
  • push posterior
  • pressure in, pullout a bit, then push again
  • relax probe pressure until image begins to blur, then reapply pressure for best image
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12
Q

Voiding before TVS exam

A
  • Brief interval (15 min) b/w voiding and TVS cervical evaluation is a associated with decreased risk for focal myometrial contractions (can impede accurate cervical length)
  • delaying cervical evaluation to later gestational age (21-23 weeks) may decrease focal myometrial contraction incident
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13
Q

% visualization of cervix

A

Transabdominal : 86% w/ full bladder

Translabial : 90%

Transvaginal : 100%

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14
Q

Cervical scan technique

A
  • rotate probe to see best long axis view of the canal
  • find these landmarks in order
    1. Fetus and amniotic fluid
    2. Bladder
    3. Internal os
    4. Cervical canal
    5. External os
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15
Q

Exam length of time

A

Less than 5 min is not enough to detect possible changes in cervical length as well as evaluating funneling

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16
Q

Transvaginal cervical technique

A
  • anterior and posterior cervical width is same size
  • entire canal seen well
  • both internal and external os identified
  • do not get fluid in measurement
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17
Q

Pressure techniques

A

✔️ transfundal pressure (on top of uterus)

✔️ suprapubic pressure (above pubic bones)

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18
Q

Pressure techniques purpose

A
  • performed to establish shortest cervical length

- observe funneling at Internal Cervical Os

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19
Q

Transfundal Pressure

A
  • patient in supine position

- hand placed at fundus of uterus and downward pressure applied

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20
Q

Suprapubic pressure

A
  • patient in supine position

- hand placed just superior to the symphysis pubic bone and downward pressure applied

21
Q

Cervical length measurements

A
  • wait 30 sec before measuring cervix
  • 1st measurement usually longer than subsequent measurements (discard it)
  • measure length repeatedly until change is less than 10%
    (Take multiple measurements)
  • record “shortest best measurement” (do not average poor measurements)
22
Q

Trouble finding a good image?

A
  • make sure the probe is inserted far enough to see the cervix
  • 1st organ seen is always the maternal bladder
23
Q

Trouble finding a good image?

A
  • find lowermost edge of the empty bladder -> internal os should be directly below
  • cervical axis may not lie in mid-plane of body -> move probe left and right
24
Q

Uterine didelphysis

A
  • estimated to occur in 1/3,000 women
  • uterus is present as a paired organ
  • will have a double cervix
  • complete separation of uterus = 2 vaginas, but one is usually blocked
  • ask about success rate w/ tampons (don’t work because you need 2)
  • note in which uterus the pregnancy is in
25
Q

Cervical length at 24 weeks

A

1st percentile - 13mm 21% PTD (pre term delivery)

5th percentile - 20 mm 12%

10th percentile - 26 mm 8%

25th percentile - 30 mm 5%

50th percentile - 35 mm 3.4%

26
Q

Candidates for TV US

A
  • women w/ suspected cervical incompetence
  • women w/ symptoms of preterm labor in current pregnancy (uterine contractions)
  • asymptomatic pregnant women w/ risk factors for preterm birth
  • wine w/ suspected placenta previa or low lying placenta
  • women w/ suspected cervical pregnancy
27
Q

Changes of Internal Os w/ funneling

A
  • cervical canal shortens progressively and an opening of a funnel shaped internal cervical os occurs until complete cervical effacement is achieved
  • the letters T Y V U illustrate cervical changes that can be seen
28
Q

Changes of internal cervical Os

A

T rust

Y our

V aginal

U ltrasound

29
Q

Funneling - functional length

A

Cervical length distal to the funnel extending to external cervical os

30
Q

Funneling - funnel length

A

Length of a line that connects the apex of the funnel to the superior edge of the base of the funnel

  • from cervix (opening up) to internal os
31
Q

Cervical incompetence

A
  • affects 1% of pregnant women

- 2nd trimester painless dilation followed by fetal expulsion

32
Q

Risk factors for cervical incompetence

A
  • in utero exposure to DES
  • major uterine anomalies
  • history of cervical trauma
  • history of recurrent spontaneous and therapeutic abortions
  • history of precipitous labor or advanced dilation before labor onset
33
Q

Preterm labor (PTL)

A

-diagnosis is made when cervical change is noted on serial digital examinations of the cervix (do at 37-38 weeks)

34
Q

Preterm birth (PTB)

A

Any delivery that occurs before 37 completed weeks

35
Q

Signs of preterm labor

A
  • vaginal discharge
  • pelvic or lower abdominal pressure
  • constant low full backache
  • mild abdominal cramps
  • regular or frequent contractions or uterine tightening
  • PROM (premature rupture of membranes, water breaks, baby MUST come out)
36
Q

Major risk factors for spontaneous PTL

A
  • multiple gestation
  • previous preterm delivery
  • abdominal surgery during pregnancy
  • uterine anomaly
  • hydramnios (too much amniotic fluid)
  • history cone biopsy
  • more than one 2nd trimester termination
37
Q

Surgical techniques to strengthen the cervix

A
  • shirodkar cerclage (requires anterior displacement of the bladder
  • McDonalds Cerclage (purse string technique, thread through cervix, want to place it closer to internal os)
  • Transabdominal cerclage
  • performed prophylactically (just in case, ahead of needed time, better safe than sorry) at 12-15 weeks gestation
38
Q

Other treatment to strengthen the cervix

A

Progesterone supplementation

  • cost effective
  • safe
  • accepted by patients
  • widely available
39
Q

Abdominal cerclage

A
  • performed b/w 11-13 weeks
  • bladder flap created
  • cesarean delivery is necessary (suture is left in place if future fertility is desired)
40
Q

Placenta previa

A
  • 3 recognized variations
    > total
    > partial
    > marginal
  • gestational age at time of US greatly influences incidence of placenta previa
  • TVS best for visualization
41
Q

Placenta previa incidence

A
  • incidence w/ TAS is reported to be 5% during 2nd trimester - at delivery 0.5%
  • incidence with TVS is reported to be 1.1% - at delivery 14%
  • placenta overlapping the internal cervical os by more than 10mm identified women at risk of previa at delivery
42
Q

Vasa Previa

A
  • presence of fetal blood vessels across the internal cervical os
  • blood vessels near the internal cervical os may be detected with TAS/TVS
  • Color/duplex Doppler can confirm fetal origin of the vessels
43
Q

Placenta previa and Vasa Previa

A

Both require c-section

44
Q

Cervical pregnancy

A
  • incidence varies: 1/2500 to 1:12,422
  • 1% of ectopic pregnancies
  • c-section scars increase the risk
45
Q

Lesson #1

A

TVS and TPS are more reproducible than images obtained by TAS full bladder

46
Q

Lesson #2

A

After 20 weeks gestation, the cervix appears to shorten or efface slightly with increasing gestational age

  • median values: 35-40 mm at 24-28 weeks
  • median values: 30-35 mm after 32 weeks
47
Q

Lesson #3

A

2 findings that are consistently associated with an increased risk of preterm birth:

1- cervical length less than the 10th (25mm) to 25th (30mm)

2- appearance of funnel at ICO that is greater than 40-50% of total cervical length

48
Q

Preme

A

Birth less than 32 weeks

49
Q

Late pre-term

A

32-37 weeks, still complications involved

50
Q

Funneling

A

Only normal after 36 weeks

General Sonography (2 decks)

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