Anatomy of the Pelvis
in Computed Tomography
Michael C. Ficorelli, RT
Lesson Description
To explain the various exams pertaining to the
pelvis using computed tomography,
incorporating cross sectional anatomy from
images
Lesson Description
• To be able to identify anatomy within the pelvis.
Understand the clinical indications for exams. To
understand the methods of patient scanning,
positioning, and protocols. To understand indications
for contrast.
CT of the Pelvis
Pelvis
• Provides structural support for the body and
contains both the male and female
reproductive organs
• Bony Pelvis – contains the sacrum, coccyx and
two innominate bones
Bony Pelvis
Bony Pelvis
• Sacrum – Triangular shaped bone formed by 5
fused vertebrae
– S-1 contains prominent ridge on anterior surface
referred to as sacral promontory – separates
abdomen from pelvis
– Transverse process of the 5 are fused to form the
lateral mass (ala)
– Sacral foramina – located within the lateral mass for
transmission of the sacral nerves
• Coccyx – 3 to 5 fused small bony segments
Bony Pelvis
Bony Plevis
• Innominate bone – Made of 3 bones
– Ilium – largest and superior portion
• Body and ala
• Superior rim – Iliac crest
– Slopes downwards to ASIS (Anterior Superior Iliac Spine) and PSIS
• Body is uppermost portion of acetabulum
– Ischium – inferior portion
• Body and 2 rami
• Superior ischial ramus extends posteriorly and inferiorly to ischial tuberosity
(you sit on it)
• Body is lowermost portion of acetabulum
• Greater and Lesser sciatic notches extend from ischial spine and allows
transmission of nerves and vessels
• Obrturator Foramen – opening enclosing the union of pubic and ischial rami
– Pubis – lower anterior portion of acetabulum
• Body and 2 rami (superior and inferior)
• Bodies of both sides meet at midline – Symphysis Pubis
Bony Pelvis
Pelvic Muscles
• Rectus Abdominus – anterior surface of
abdomen and pelvis
• Psoas Muscle – Lateral to the lumbar
vertebrae and medial to the ilium
• Gleuteus Muscles
– Maximus - outermost
– Medius
– Minimus – innermost (lateral to pelvic bone)
Pelvic Muscles
Perineum
• Posterior to pubic arches; anterior to coccyx
• 2 divisions
– Anal Triangle – contains inferior 1/3 of anal canal
and sphincter muscles
– Urogenital diaphragm – openings of the urethra
and vagina in females; urethra and root structures
of penis in males
Pelvic Organs
• Bladder – lies on the pelvis floor immediately posterior to
symphysis pubis and is responsible for the storage of urine
– Pyramid shaped
– Storage capacity 750 cc Max
– Urethra – muscular tube which drains urine from the bladder
• Rectum – Terminal colon extending from L-3
– Anus – Exit
– Anal Sphincter – ring of muscle fibers under voluntary control
• Prostate Gland – largest accessory gland in the male
reproductive system
– Inferior to the bladder and surrounds the urethra
Bladder and Prostate
Pelvic Vasculature
• Abdominal Aorta descends into the pelvic cavity
and bisects at the level of L-4 into the Right and
Left Iliac arteries
– Right and Left Iliac bifurcate again at the level of the SI
Joints into Internal and External Iliac arteries
• Internal and External Iliac Veins run similar
courses as the arteries and meet at the level of
the SI joints to form the Right and Left Iliac Veins
– Meet at L-4 to form the IVC
Pelvic Vasculature
Pelvis Standard
1
2
1 – Ascending Colon
3
2 – Ileum
3 – Descending Colon
4 – Iliac Artery
4
Pelvis Standard
1
1 - Cecum
Pelvis Standard
1
2
1 – Uterus
2 – Ovary
3 - Rectum
3
Pelvis Standard
11
2
1 – Bladder
3
2 – Uterus
3 – Ovarian Cyst
4 - Rectum
4
Pelvis Standard
1
1 - Bladder
Pelvis Standard
1 - Anus
1
Pelvis Bone
1
2
1–L–5
2 – Iliac Crest
Pelvis Bone
1
1 – Sacral
Promontory
2 – SI Joint
2
Pelvis Bone
1
1 – Ilium
2 - Sacrum
2
Pelvis Bone
1 – Ilium (top of
acetabulum)
1
Pelvis Bone
1
1 – Pubic Bone
2 – Acetabulum
3 - Iscium
3
2
Pelvis Bone
1
2
1 – Pubic Rami
2 – Femoral Head
3 – Iscium
3
Pelvis Bone
1
2
1 – Symphysis Pubis
2 – Femoral Neck
3 – Iscial Tuberosity
3
Pelvis Bone
1 – Pubic and Iscial
Ramus
1