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FEMALE PELVIC ANATOMY AND SONOGRAPHIC EVALUATION


Commonly Used Quadrant Terminology:
RUQ - Right Upper Quadrant
RLQ - Right Lower Quadrant
LUQ - Left Upper Quadrant
LLQ - Left Lower Quadrant
***Abdomen divided by sagittal plane crossing through midline at umbilicus and a transverse plane crossing through the abdomen at the level of the umbilicus


Addison's Nine Regions:
Right Hypochondrium - liver, GB, hepatic flexure of colon
Epigastric - pancreas, stomach, transverse colon
Left Hypochondrium - spleen, stomach, left kidney (upper pole)
Right Lumbar - right kidney, ascending colon
Umbilical - Transverse colon, small bowel
Left Lumbar - left kidney (mid/lower poles), descending colon
Right Iliac - ovary, seminal vesicle
Hypogastric - bladder, uterus, prostate, rectum, sigmoid
Left Iliac - ovary, seminal vesicle

ANATOMY

Internal Organs:
  • Uterus
  • Fallopian Tubes
  • Ovaries
  • Vagina
  • Accessory Glands
  • Skene's glands-paraurethral gland
  • Bartholin's glands-on either side of vagina
  • Mammary glands- within the breasts

External Structures:
  • Mons Pubis- fatty prominence covering the symphysis pubis
  • Labia Majora- outer lips covering vaginal opening
  • Labia Minora- inner lips, smaller
  • Clitoris- lies below the junction of the labia majora
  • Linea Terminalis- imaginary line connecting superior sacrum to symphysis pubis, separates true and false pelvis
Greater/False Pelvis:
  • Above the pelvic brim
  • Communicates with the abdominal cavity
  • Contains sigmoid colon and ileum
  • Pelvic Muscles=False Pelvis
       o        Rectus Abdominis-forms anterior wall of abdominopelvic cavity, from xiphoid to symphysis pubis
       o        Psoas Major-originates in lumbar vertebral region, connects with iliacus muscle to form iliopsoas muscle

Lesser/True Pelvis:
  • Below the pelvic brim
  • Formed by the bony bowl of the pelvic bones
  • Enclosed inferiorly by membranes and muscles
  • Contains uterus, vagina, fallopian tubes, ovaries, rectum and bladder

Pelvic Muscles in True Pelvis:

  • Levator Ani - most inferior structure; forms the floor of the pelvis; has 3 openings for urethra, vagina and rectum
  • Obturator Internus - located laterally at the acetabulum;  triangular sheet; covers anterior and lateral walls
  • Piriformis - superior and lateral to levator ani muscles, originates from sacrum; covers posterior wall
  • Coccygeus - forms the posterior portion of the pelvic wall; originates from the coccyx

Functions of the Pelvic Skeleton:
  • Provides a weight bearing bridge between spine and ribs
  • Directs the pathway of the fetal head during child birth
  • Protects reproductive organs
Pelvic Spaces:
  1. Anterior Cul-de-Sac:  fold in the peritoneum between anterior uterus and posterior bladder; AKA vesicouterine pouch
  2. Posterior Cul-de-Sac: fold in the peritoneum between posterior uterus and anterior rectum; AKA rectouterine pouch or pouch of Douglas
  3. Space of Retzius: anterior to bladder posterior to symphysis pubis, very unusual for fluid collection, not contiguous with abdominopelvic cavity; AKA retropubic space
Ligaments:

Broad Ligaments:
  • Wing like folds of the peritoneum extending to lateral pelvic walls
  • Separates pelvic cavity into anterior and posterior portions
  • Covers anterior and posterior surfaces of the uterus
  • Encases most of fallopian tubes and round ligament, ovarian ligament and vessels
  • Loosely positions uterus in pelvic cavity
  • Mesovarium - portion of the peritoneum connecting anterior ovary to posterior broad ligament
  • Mesosalpinx - free margin of the broad ligament where the fallopian tube travels
Cardinal Ligaments:
  • AKA Transverse Cervical Ligament of Mackenrodt
  • Band of fibrous tissue and muscle
  • Extends from upper lateral cervix to lateral pelvic wall
  • Contains the uterine and vaginal vessels
Round Ligaments:
  • Fibromuscular bands extending from uterus to labia majora
  • Maintains normal uterine position
  • Assists in birth
Uterosacral Ligaments:
  • Extend from upper cervix to lateral sacrum
  • Determines the uterine position/orientation in the pelvis
Suspensory Ligaments:
  • Folds of peritoneum that contain the ovarian vessels
  • Aids broad ligament in supporting fallopian tubes and ovaries within pelvis
Vagina Anatomy:
  • Anterior to rectum, posterior to urethra
  • Collapsible, fibromuscular tube
  • Outlet covered by hymen
  • Connects to cervix at the fornix
  • Walls should not exceed 1cm thickness
  • Avg cuff measurement 1.4cm

Vagina Physiology:
1.        To receive seminal fluid
2.        Excretory duct for menstruation
3.        Lowest portion of birth canal

Uterine Anatomy:
  • Hollow, thick-walled muscular organ
  • Inner mucus layer = endometrium
  • Muscle layer = myometrium 
  • Outer serous layer = perimetrium
  • Cervix connects uterine cavity with vagina
  • Internal os - opening from uterus into cervix
  • External os - opening from cervix to vagina
Three Wall Layers:
  • Endometrium - innermost layer, varies in thickness during the menstrual cycle due to proliferation and sloughing
  • Myometrium - middle layer, thickest layer, involved in birth
  • Perimetrium - outermost layer; serosa; composed of fibrous connective tissue
Location/Landmarks:
  • Round, Cardinal and Uterosacral ligaments suspend the uterus in the pelvic cavity
  • Sits between two layers of the Broad Ligament
  • Posterior to bladder
  • Anterior to rectosigmoid colon
Size:
  • Neonatal - Cervix much longer than the body/fundus
  • Prepubertal - Average 3cm x 0.7cm; body half the size of the cervix
  • Adult - average 8 x 5 x 3cm nulliparous, 1:1 ratio of cervix and body/fundus length
  • Adult - average multiparous, body/fundus 2 x longer than cervix
  • Postmenopausal - segment ratio remains same, overall organ atrophy
Uterine/Cervix Position:
  • Anteverted - uterus forms a 90 degree angle with the cervix
  • Anteflexed - uterine body forms a sharp angle with the cervix, folds over sharply on the cervix
  • Retroverted - uterine body tips posteriorly with a small angle between the corpus and the cervix
  • Retroflexed - uterine body folds posteriorly at a very sharp angle to the cervix
  • Dextroflexed - uterine body flexed to the right
  • Dextroposition - entire uterus is displaced to the right
  • Levoflexed - uterine body flexed to the left
  • Levoposition - entire uterus is displaced to the left

Uterine Arterial Supply:
  • Internal Iliac Artery AKA Hypogastric Artery
  • In a non-pregnant patient, the internal iliac artery is smaller in caliber than the external iliac artery
  • Divides into anterior and posterior segments
  • Anterior segment branches
  1. Umbilical artery
  2. Inferior vesicle artery
  3. Middle rectal artery
  4. Uterine artery
  5. Vaginal artery
  • Uterine artery flow is of moderate velocity and high resistance
  • Resistance increases with age until diastolic flow is absent or nearly absent (RI 1.0)
Uterine Venous Drainage:
  • Uterine veins empty into the internal iliac veins
  • In a non-pregnant patient, the internal iliac vein is smaller in caliber than the external iliac vein
  • Merges with the external iliac vein to form the common iliac vein
  • Drains pelvic organs
PHYSIOLOGY OF THE UTERUS
  • Menstruation - menarche usually occurs age 11-14 years
  • Pregnancy
  • Labor and expulsion of fetus at birth
Endometrial Anatomy:
  • Endometrium Varies with age, menstrual phase and HRT
  • Premenopausal NL <14mm
  • Postmenopausal with estrogen HRT NL <8mm
  • Postmenopausal with combined estrogen and progesterone HRT NL 10-12mm
  • Postmenopausal no HRT <5mm
Endometrial Blood Supply:
  • Internal Iliac Artery - Uterine Artery - Arcuate Artery - Straight and Spiral Arteries
  • Uterine - courses along lateral margin between layers of broad ligament
  • Arcuate - circle the uterus
  • Straight - supply deeper 1/3 of endometrium, does NOT slough off with menstruation
  • Spiral - sloughed off and reformed after menses, respond to ovarian hormones
Hormones of the Menstrual Cycle:
Gonadotropin Releasing Hormone (GnRH):
  • Secreted by the hypothalamus when estrogen levels are low
  • Stimulates pituitary gland to produce and release luteinizing hormone and follicle stimulating hormone
Follicle Stimulating Hormone:
  • Secreted by the anterior pituitary gland
  • Stimulates estrogen production
  • Responsible for follicle and ova maturation
Luteinizing Hormone:
  • Secreted by the anterior pituitary gland
  • Stimulates theca cells to produce androgens that are converted into estrogen
  • Responsible for ovulation and corpus luteal development
Estrogen:
  • Naturally produced steroid hormone
  • Responsible for the development of reproductive organs and maintains their function during reproductive years
  • Causes development of secondary sex characteristics such as axillary and pubic hair, breast development, fat deposits on breasts, thighs and buttocks
  • Stimulates endometrium to thicken prior to ovulation
Estradiol:
  • The principle component of estrogen formed by ovarian follicles, adrenal cortex and the placenta
  • Responsible for reproductive development and maintenance
  • Linked to endometriosis, fibroids and carcinoma
Estriol:
  • Component of estrogen
  • Only produced in the placenta (pregnancy)
Estrone:
  • Component of estrogen
  • Only type of estrogen found in the postmenopausal woman
Progesterone:
  • Produced by the corpus luteal cells post-ovulation
  • Responsible for endometrial proliferation for implantation
  • Blocks the development of new follicles
  • Stimulates uterine blood supply for pregnancy
  • Causes breasts to prepare for lactation but inhibits lactation during pregnancy
  • Causes formation of cervical mucus
Prolactin:
  • Produced by the pituitary gland; stimulates milk production with pregnancy
  • Milk production usually begins within 2-3 days post partum
Oxytocin:
  • Produced by the pituitary gland; causes ductal contraction with lactation
Endometrial Cycle:
Day 1-5 Menstrual Phase:
  • At the onset and during menstruation, estrogen and progesterone levels are very low causing the uterus to shed the lining
  • <4mm endometrial thickness at the end of menstruation
Day 6-10: Early Proliferative Phase:
  • Increasing estrogen levels cause endometrial proliferation
  • 5-8mm endometrial thickness
  • Early phase - endometrium appears as a thin hyperechoic line
Day 11-13: Late Proliferative Phase:
  • Increasing estrogen levels continue to cause endometrial proliferation
  • <11mm endometrial thickness at the end of the late phase
  • Late phase - endometrium appears thickened and hypoechoic line centrally
Day 14 -28: Secretory Phase:
  • Increased estrogen and progesterone levels cause a decrease in FSH and LH levels
  • Mucus is produced in the cervix with ovulation
  • Endometrium continues to thicken
  • If no fertilization occurs the corpus luteal cyst involutes causing decreased progesterone levels until menstruation begins on Day 1
  • 9-16mm endometrial thickness; thickened hyperechoic appearance


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