Anatomy of the Pelvisin 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 Standard1 2

3

4

1 – Ascending Colon

2 – Ileum

3 – Descending Colon

4 – Iliac Artery

Pelvis Standard

1

1 - Cecum

Pelvis Standard

12

3

1 – Uterus

2 – Ovary

3 - Rectum

Pelvis Standard

112

3

4

1 – Bladder

2 – Uterus

3 – Ovarian Cyst

4 - Rectum

Pelvis Standard

1

1 - Bladder

Pelvis Standard

1

1 - Anus

Pelvis Bone1

2

1 – L – 5

2 – Iliac Crest

Pelvis Bone1

2

1 – Sacral Promontory

2 – SI Joint

Pelvis Bone

1

2

1 – Ilium

2 - Sacrum

Pelvis Bone

1

1 – Ilium (top of acetabulum)

Pelvis Bone

1

2

3

1 – Pubic Bone

2 – Acetabulum

3 - Iscium

Pelvis Bone

12

3

1 – Pubic Rami

2 – Femoral Head

3 – Iscium

Pelvis Bone

12

3

1 – Symphysis Pubis

2 – Femoral Neck

3 – Iscial Tuberosity

Pelvis Bone

1

1 – Pubic and Iscial Ramus