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 2 1 1 – Ascending Colon 2 – Ileum 3 – Descending Colon 4 – Iliac Artery 3 4

Pelvis Standard 1 1 - Cecum

Pelvis Standard 1 2 1 – Uterus 2 – Ovary 3 - Rectum 3

Pelvis Standard 2 1 – Bladder 2 – Uterus 3 – Ovarian Cyst 4 - Rectum 1

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