Diagnostic Ultrasound - Abdomen and Pelvis

Cervix
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Anatomy: Pelvis
GROSS ANATOMY
Overview
• Begins at inferior narrowing of uterus (isthmus)
○ Supravaginal portion: Endocervix
○ Vaginal portion: Ectocervix
• Endocervical canal: Spindle-shaped cavity communicates
with uterine body and vagina
• Internal os: Opening into uterine cavity
• External os: Opening into vagina
• Largely fibrous stroma with high proportion of elastic fibers
interwoven with smooth muscle
• Endocervical canal lined by mucus-secreting columnar
epithelium
○ Epithelium in a series of small V-shaped folds (plicae
palmatae)
• Ectocervix lined by stratified squamous epithelium
• Squamocolumnar junction near external os but exact
position variable
• Nabothian cysts are commonly seen
○ Represent obstructed mucus-secreting glands
• Entire cervix is extraperitoneal
○ Anterior: Peritoneum reflects over dome of bladder
above level of internal os
○ Posterior: Peritoneum extends along posterior vaginal
fornix, creating rectouterine pouch of Douglas (cul-desac)
• Arteries, veins, nerves and lymphatics
○ Arterial supply
– Descending branch of uterine artery from internal iliac
artery
○ Venous drainage
– To uterine vein and drains into internal iliac vein
○ Lymphatics
– Drain into internal and external iliac lymph nodes
○ Innervation
– Sympathetic and parasympathetic nerves from
branches of inferior hypogastric plexuses
• Variations with pregnancy
○ Nulliparous: Circular external os, arterial waveform
shows high resistivity index (RI)
○ During pregnancy: Changes become apparent by ~ 6
weeks of gestation
– Softened and enlarged cervix due to engorgement
with blood with decreased RI of uterine artery
– Hypertrophy of mucosa of cervical canal: Increased
echogenicity of mucosal layer
– Increased secretion of mucous glands: Increased
volume of mucus ± mucus plug in cervical canal
○ Parous: Larger vaginal part of cervix, external os opens
out transversely with an anterior and posterior lips
• Variations with age: Cervix grows less with age than uterus
○ Neonatal: Adult configuration due to residual maternal
hormonal stimulation
○ Infantile: Cervix predominant with cervix to corpus
length ratio ~ 2:1
○ Prepubertal: Cervix to corpus length ratio ~ 1:1
○ Reproductive: Uterus predominant, cervix to corpus
length ratio ≥ 1:2
○ Postmenopausal: Overall reduction in size
Anatomy Relationships
• Anterior
○ Supravaginal cervix: Superior aspect of posterior bladder
wall
○ Vaginal cervix: Anterior fornix of vagina
• Posterior
○ Supravaginal cervix: Rectouterine pouch of Douglas
○ Vaginal cervix: Posterior fornix of vagina
• Lateral
○ Supravaginal cervix: Bilateral ureters
○ Vaginal cervix: Lateral fornices of vagina
• Ligamentous support: Condensations of pelvic fascia
attached to cervix and vaginal vault
○ Transverse cervical (cardinal) ligaments
– Fibromuscular condensations of pelvic fascia
– Pass to cervix and upper vagina from lateral walls of
pelvis
○ Pubocervical ligaments
– Two firm bands of connective tissue
– Extend from posterior surface of pubis, position on
either side of neck of bladder and then attach to
anterior aspect of cervix
○ Sacrocervical ligaments
– Fibromuscular condensations
– Attach posterior aspect of cervix and upper vagina
from lower end of sacrum
– Form 2 ridges, one on either side of rectouterine
pouch of Douglas
IMAGING ANATOMY
Ultrasound
• Transabdominal scan
○ Mucus within endocervical canal usually creates
echogenic interface
○ In periovulatory phase, cervical mucus becomes
hypoechoic due to high fluid content
○ Mucosal layer: Echogenic
– Thickness and echogenicity shows cyclical changes
similar to endometrium
○ Submucosal layer: Hypoechoic
○ Cervical stroma: Intermediate to echogenic
• Transvaginal scan
○ Angle of insonation should be optimized for best
visualization
○ Imaging may be improved with withdrawal of probe into
mid vagina
MR
• Important in local staging of cervical cancer
• Uniform intermediate signal on T1WI
• Zonal anatomy on T2WI
○ Endocervical canal: High signal
○ Cervical stroma: Predominately low signal, contiguous
with junctional zone
○ Outer layer of smooth muscle (variably present):
Intermediate signal
○ Parametrium: Variable signal intensity
– Cardinal ligament and associated venous plexuses
high signal
– Sacrocervical ligament low signal