US gynae & obstetrics Flashcards
what is included in the gynae US
- uterus
- ovaries
- fallopian tube
- bladder
- adnexa
- pouch of douglas
anatomy of uterus
- pear-shaped organ
function of uterus
- provides mechanical protection, nutritional support and waste removal for pregnancy
- contractions of muscular walls during labour is responsible for pushing out fetus
variations in uterine positions
- anteverted
- midposition/ axial
- retroverted
- anteflexed
- retroflexed
location of ovaries
- varies due to laxity of ligamentous attachments
- ovaries usually seen lateral to the uterus
- internal iliac vessels are found at the posterolateral border of the ovaries
what is menstrual and ovarian cycle
- repeating series of changes in the endometrium
- avg of 28 days
3 phases of menstrual cycle
- menstrual phase
- proliferative phase
- secretory phase
2 phases of ovarian cycle
- follicular phase
- luteal phase
describe what happens during the menstrual phase
- functional layer of endometrial lining of the uterus is shed and exits through vagina
- slowly rising levels of FSH and LH secreted by pituitary gland –> cause development of ~20 primary follicles
- pri follicles grow and develop into secondary follicles –> release estrogen and low level of progesterone
describe what happens during the proliferative phase
- after ~5 days, estrogen levels rise and enters proliferative phase
- endometrium begins to regenerate, blood vessels and glands begin to regrow
- ~ day 9, only one healthy secondary follicle becomes dominant while other follicles become antretic
- dominant follicle continues to grow in size and is responsible for producing large amounts of estrogen during late follicular phase
describe what happens during ovulation
~ day 14, high levels of estrogen causes FSH and LH to rise rapidly
- spike in LH cause ovulation –> mature dominant follicle ruptures and release egg
- follicles that did not rupture degenerate and their eggs are lost
- level of estrogen decreases when extra follicles degenerate
describe what happens during secretory phase
- after ovulation, menstrual cycle enters the secretory phase
- ovarian cycle enters the luteal phase
- cells in the follicle that ruptured during ovulation undergoes changes and form the corpus luteum –> produces significant amount of progesterone and smaller amount of estrogren
- progesterone facilitates the regrowth of the uterine lining to prepare for implantation
- progesterone also inhibits release of further FSH and LH –> prevents any further egg and follicles from developing
what happens if no egg is fertilised
- corpus luteum degenerates and levels of estrogen and progesterone decreases, initiating the next menstrual cycle
- decrease in progesterone also allows hypothalamus to send GnRH to anterior pituitary, releasing FSH and LH and starting cycle again
possible causes for abnormal PV bleed
- irregular menstrual cycle
- menorrhagia
- dysmenorrhea
- postmenopausal bleeding
possible causes of pelvic pain
- torsion
- pelvic inflammatory disease
- ruptured cyst
common clinical indications that warrants a gynae scan
- abnormal vaginal discharge
- amenorrhea
- pelvic mass
- infertility
- follicle monitoring
- locate intrauterine contraceptive device (IUCD)
- developmental abnormality
- postpartum complications (RPC)
- abnormal PV
- pelvic pain
2 types of sonographic methods performed in gyane
transabdominal (TA)
- transducer placed on lower abdomen to acquire images of the female pelvis
transvaginal (TV)
- transducer placed within the vaginal cavity
advantages of TA approach
- non-invasive (for female who has never had sexual intercourse before, whose hymen remains unbroken: virgo intacta)
- visualises the entire pelvis
- gives a global overview
limitations of TA apporach
- patients unable to fill the bladder will result in poor quality image
- patient unable to hold bladder for duration of scan - feel uncomfortable
- obese patients (fats attenuate signals)
- retroverted uterus
advantages of a TV approach
- examinations of patients who are unable to fill up bladder
- examinations of obese patients
- examinations of retroverted uterus
- allows use of higher-frequency transducers –> better resolution, better image quality & better anatomic detail
- better detail and characterisation of the internal characteristics of the internal characteristics of a pelvic mass
- better detail of the endometrium
limitations of TV approach
- because of higher frequencies, FOV is limited
- orientation difficult for larger masses (extend if out FOV)
- limited depth (superiorly or laterally placed ovaries or masses may not be visualised)
contraindications of TV
patient:
- is a virgin
- is an elderly
- refuses
what transducer is used for TA scan
- low frequency (1-5MHz) curvilinear probe
- provides adequate penetration and large footprint to image the reproductive organs and surroundings
why is full bladder required for a TA scan
- bladder located anterior to the uterus
- full bladder provides an acoustic window for the US waves to pass through
- also displaces small bowels from FOV - bowel gas obscures visualisation of uterus and ovaries and any pelvic mass
what if patient has overdistention of bladder
- compromised evaluation
- ask patient to partially empty bladder
how to scan bilateral adnexal regions to include both ovaries and surrounding
angle to probe, using the bladder as an acoustic window, to image ROI
what does full bladder cause on a TV scan
- uncomfortable during scan
- cause artifact on TV scan image
in TV scan, what axis correlates to the sagittal plane
- long axis = sagittal plane
- plane perpendicular to sagittal = coronal plane
ovaries are most easily located in which plane
coronal
describe an anterverted uterus
uterus tilted forward, towards bladder
describe a retroverted uterus
- uterus tilted backward, away from bladder
normal sonographic appearance of the female pelvis
- pear-shaped
- diameter and length of body double that of the cervix
- outline of uterus should be smooth
- normal adult uterus varies in size:
*parity increases the size in uterus
*after menopause, uterus atrophies
normal measurements of nulliparous uterus
- L: 8cm
- W: 5cm
- AP diameter: 4cm
normal measurements of primiparas
1cm increase in each dimension of a nulliparous uterus
- L: 9cm
- W: 6cm
- AP diameter: 5cm
normal measurements of multiparas
2cm increase in each diameter of a nulliparous uterus
- L: 10cm
- W: 7cm
- AP diameter: 6cm
thickest portion of the uterus
myometrium
what is myometrium made up of
muscle tissue
what are the 3 layers of myometrium
- inner layer
- intermediate later
- outer layer
describe the inner layer of the myometrium
- just adjacent to and surrounds the endometrium
- hypoechoic and thin
describe the intermediate layer
- thickest, homogeneous, and show low to moderate echogenicity
describe the outer layer of the myometrium
- thin layer separated from the intermediate layer by the arcuate vessels
what is the 2 layers of endometrium
functional layer - thickens during menstrual cycle and sheds during menses
basal layer - remains intact throughout the cycle and contains the arteries which supply the functional layer as it thickens
sonographic appearance of endometrium
varies throughout the menstrual cycle
endometrial cavity
- is a thin echogenic line
- result of specular reflection from the interface between the opposing surfaces of the endometrium
describe the sonographic appearance during menstrual phase
- endometrium is a thin echogenic line
- there can be clots and fluid present within the uterine cavity
describe the sonographic appearance during the early proliferative phase
- thin echogenic line
- normal endometrial thickness: 4-8mm
describe the sonographic appearance during the late proliferative phase (periovulatory)
- classic triple line appearance is seen in an endometrium
- endometrium appears echogenic around its periphery and in the midline, and hypoechoic in between
- hypoechoic areas are the functional layer while the peripheral echogenic layers are the basal layers
- normal endometriual thickness: 6-10mm
describe the sonographic appearance in the secretory phase
- functional layer become increasingly echogenic until it merges with the equally echogenic basal layer to appear as a thick echogenic secretory-phase-endometrium
- endometrium appears thick and echogenic
- normal thickness: 7-14mm
how is the endometrium measured
- measure on the longitudinal or sagittal image of the midline uterus, showing entire endometrium in continuity to the cervical canal
- measure at the thickest portion
- ensure the calipers are placed on the outer echogenic border
normal sonographic appearance of ovary
- ellipsoidal in shape
- homogenous echotexture
- central slightly more echogenic medulla
- usually has multiple well-defined anechoic cystic follicles within
- appearance changes with phase of the menstrual cycle
normal sonographic appearance of ovary during early proliferative phase
- many anechoic, well-defined, small cystic follicles stimulated by FSH and LH develop and grow in size
normal sonographic appearance of ovary during ovulation
- dominant anechoic cystic follicle with well defined borders seen within ovary (around day 9)
normal sonographic appearance of ovary after ovulation
corpus luteum has variable appearances:
- hypoechoic/ isoechoic
- thin or thick walls
- presence or absence of cystic centre
- cystic centre which may or may not contain internal echoes
- on colour doppler, shows a “ring of fire” due to peripheral vascularity
appearance of cervix
- cervical canal is a thin echogenic line
- outline of cervix should be smooth and the cervical wall of homogenous echotexture
appearance of the vagina
- hypoechoic tubular structure with a
- central echogenic linear line representing the apposed surfaces of the vaginal mucosa
types of uterine malformations
- arrested development of the Mullerian ducts
- failure of fusion of the Mullerian ducts
- failure of resorption of the median septum
possible sites of fibroid/ leiomyoma/ myoma
- intramural
- submucosal
- subserosal
- pedunculated
endometrium thickness
1-14mm
what is endometrium thickness affected by
- stimulated by estrogen
- involuted by progesterone
possible causes of endometrial thickening
- dysfunctional uterine bleeding
- endometrial hyperplasia
- hormonal replacement therapy (HRT)
- tamoxifen treatment
- endometrial carcinoma
- endometrial polyps
- endometritis
types of obstruction in the genital tract
part
- colpos = vaginal distention
- metrocolpos = uterine cavity and vaginal distention
content
- blood = haemato
- fluid = hydro
- pus = pyo
features of PCOS
- chronic anovulation
- sub-fertility
- irregular menstrual cycles
- oligo or amenorrhea with occasional heavy bleeding
- usually presents from menarche (puberty)
PCOS is a syndrome consisting of
- amenorrhea
- hirsutism
- obesity
- enlarged, polycystic ovaries
advantages of using a TA approach on fetus
- pushes uterus up out of pelvis and into a horizontal position
- displaces gas-filled bowel loops
- provide visualisation of the cervical os
- acts as a landmark
- enables visualisation of the adnexa
limitations of a full bladder in obstetric TA scan
- painful for patient
- may distort gestation sac/ uterus
- may deviate uterus
- may push uterine walls together so a normal placenta looks low
- may push uterus deep into the pelvis
display function for a first trimester fetus
B-mode
M-mode
display function for a second trimester fetus
B-mode
Colour doppler
display function of a third trimester fetus
B-mode
Colour doppler
Pulsed doppler
3D/4D
ultrasound intensity of the display functions from least to most intense
B-mode < M-mode < colour doppler < pulse doppler
when is the first trimester scan done
11-14 weeks
what is gravidity/ gravida
- refers to total number of conceptions
- nulligravid - no pregnancy
- primigravida - first pregnancy
- gravida 4 - fourth pregnancy
what does the 4 digit numbers in gravida represent
- full term births
- premature births
- abortions
- live children
what is parity/ para
- refers to total number of births that weighed more than 500g
- twins counted as 1 pregnancy
- primipara - delivered 1 preg
- multipara - delivered 2+ preg
4 methods to calculate GA
- LMP
- fundal height
- b hCG
- US measurements - most accurate during first trimester (8-10 weeks)
how LMP calculates GA
date of LMP +7days, -3months, +1year
how is fundal height done to determine GA
felt by doc’s hand; in cm; topmost portion of uterus to SP
when does GA start its calculation from
- first day of LMP
- ovulation normally occurs ~14 days before onset of next period
- for the first 2 weeks of a 40-week pregnancy, mother is not pregnant, but the 2 weeks is included in the GA
when is the average EDD
40 weeks after LMP
normal sonographic appearance in early pregnancy
- endometrium appears thickened with decidual reaction noted
- early GS appears as a round anechoic area surrounded by hyperechoic ring = “double decidual sign”
- yolk sac and embryo/fetal pole must be visualised when GS diameter >25mm
- fetal heartbeat can be confidently observed when CRL >7mm
- GS in normal position
how to determine GA with US
1st tri, done by either:
- crown-rump-length
- measuring GS
how is measurement of GS done
can do either:
- avg diameter
- volume estimation (AxBxCx0.523)
how is measurement of CRL done
- longest measurement of the fetus (from crown to rump)
- care taken to exclude sac
4 different types of multiple gestation pregnancies
- monochrionic
- dichorionic
- monoamniotic
- diamniotic
how can fetal heartrate be measured
- M-mode
- pulsed doppler
US of fetal death
- no FH
- pointing of GS
- low position of GS
- large GS with small or absent embryo
- abnormal size and shape of YS
- appearances do not match dates
- no fetal movement
- spalding sign of fetal head
- diffused oedema of entire fetus
types of abortion
- complete
- incomplete
- inevitable
- missed
- threatened
sonographic indication of an ectopic pregnancy
- b hCG >1800mlU/ml and
- intrauterine GS not identified
- live fetus seen outside of uterus
- tubal echogenic ring may be seen
- echogenic rim surrounding a hypoechoic center
- colour doppler may show peripheral vascularity
- possible hemoperitoneum or free fluid in POD
sonographic appearance of a tubal pregnancy
- tubal echogenic ring may be seen
- echogenic rim surrounding a hypoechoic center
- colour doppler may show a peripheral vascularity
- possible hemoperitoneum or free fluid
normal nuchal translucency measurement
< 2.5mm
should be measured with fetus in supine position
what is acrania/ anencephaly
absence of a fetal skull with freely exposed brain tissue to amniotic fluid
what is thickened nuchal translucency
associated with chromosomal abnormality
what is cystic hygroma
- fluid-filled sac that results from a blockage in the lymphatic system
- can progress to hydrops and eventually fetal death
2 types of abdominal wall defect
- omphalocele
- gastroschisis
what are the 3 views done to view fetal head/brain
- ventricular
- thalamic
- cerebellar
how is BPD measured
from outer table of skull to inner table
how is HC measured
perimeter around the outer skull border
when can HC be used for dating
- unsure of LMP
- irregular LMP cycles
- no previous dating
what is the cerebellar view for
to evaluate the shape and size of the cerebellum
how does the cerebellum look like
seen as a ‘dumbbell’ shape in the posterior fossa
what can TCD equates to
gestational age
normal occipital horn measurement
< 10mm
combined anterior horn normal measurement
<20mm when BPD is <6.5cm
normal binocular distance
space between orbits = width of one eye
when leiomyoma turns cancerous, it is known as
leiosarcoma
what type of leiomyoma is missed on what type of US scan
TA - small fibroids
TV - pedunculated
what is the GA of a fetus of first trimester
4-14 weeks
what is the GA of a fetus of second trimester
14-28 weeks
what is the GA of a fetus of third trimester
28 weeks onwards
normal NT measurement
< 2.5mm
what does abnormal NT measurement indicate
associated with chromosomal abnormality
what are the 3 vessels present in the umbilical cord
2 arteries + 1 vessel
