The female pelvis is accustomed to a wide range of natural and pathologic conditions that a woman may experience in her life. The uterus significantly enlarges during pregnancy. The ovaries can be subject to various natural and pathologic states ranging from benign cysts to advanced ovarian carcinoma.
From the gross anatomy of the female pelvis to the microscopic anatomy, form follows function and allows for reproductive processes as well the possibility for pathologic conditions. The anatomy of the female genitourinary organs (see the image below) is addressed in the following section, along with certain anatomic variants.
The bony female pelvis is formed by two paired hip bones (each of which is made up of ilium, ischium, and pubis), the sacrum, and the coccyx. The pelvic brim divides the false pelvis above from the true pelvis below. The lumbosacral joint (between L5 and the base of the sacrum), sacroiliac joint, sacrococcygeal joint, and pubic symphysis make up the joints of the pelvis.
The pelvic viscera are covered by 2 layers of peritoneum. This broad ligament extends from the lateral margin of the uterus to the lateral pelvic wall. It comprises the mesovarium, which supports the ovary with the posterior leaf of the broad ligament; the mesosalpinx, which suspends the uterine tube; and the mesometrium, which is the major part of the broad ligament below the mesosalpinx and mesometrium.
The female pelvic organs include the ovaries, uterine (fallopian) tubes, uterus, cervix, urinary bladder, ureters, vagina, and rectum (see the images below).
The ovary is divided into a cortex and a medulla. Follicles in varying stages (according to the menstrual cycle) are found within the outer cortex. With each cycle, 1 follicle develops into a Graafian follicle, leading to ovulation. After ovulation, this follicle becomes the corpus luteum. Corpora lutea of varying stages, as well as corpora albicantia, are present in the ovarian cortex.
The medulla of the ovary is generally made up of loosely arranged mesenchymal tissue, along with small clusters of round to polygonal epithelial-appearing cells around vessels and nerves, which are also steroid-producing. The uterine tube consists of epithelium containing ciliated columnar cells, nonciliated cells, and columnar secretory cells.
The endometrium during the menstrual cycle is under the influence of ovarian hormones, specifically follicle-stimulating hormone and luteinizing hormone. The hypothalamic-pituitary-ovarian axis drives the menstrual cycle.
During the follicular phase, as a single ovum develops, estrogen production by the dominant follicle increases over the first 2 weeks of the 28-day menstrual cycle. The estrogen level peaks just before ovulation and then declines. During the luteal phase, progesterone is made by the corpus luteum; the progesterone level rises during the last half of the cycle and then falls to a basal level just before menstruation.
The endometrium is made up of glands that are straight tubular structures lined by regular, tall pseudostratified columnar cells and stroma that are compact spindle cells.Its basal third is not hormonally responsive; the remaining endometrium (both glands and stroma) undergoes rapid growth during the proliferative phase of the menstrual cycle. The glands have numerous mitotic figures. The secretory phase is notable for subnuclear vacuoles, predecidual changes, and finally stromal breakdown and the onset of menses.
The external os of the cervix is covered by stratified nonkeratinizing squamous epithelium. The internal os is lined by columnar, mucus-secreting epithelium, which dips down into the stroma to produce endocervical glands. The point at which the squamous and glandular epithelium meet is the squamocolumnar junction.
A combination of ingrowth of the squamous epithelium and metaplasia transforms this area into squamous epithelium and forms the transformation zone. It is in the transformation zone, including the squamocolumnar junction, that precancerous cervical lesions leading to squamous cell carcinoma of the cervix develop, often in the absence of routine Papanicolaou (Pap) screening.
The ureters, bladder, and urethra are lined by transitional epithelium (urothelium). The bladder has bundles of smooth muscle fibers that collectively form the detrusor muscle.
Congenital uterine abnormalities
Congenital uterine abnormalities can lead to infertility and recurrent pregnancy loss. The incidence ranges from 3-4% for fertile and infertile women, 5-10% for women with recurrent miscarriages, and more than 25% of women with late miscarriages and preterm deliveries. Uterine abnormalities can originate from failure of midline fusion of embryologic (Mullerian) structures. Some examples are as follows:
Septate uterus (most common) – A septum divides the uterus into 2 halves
Unicornuate uterus – 1 communicating and usually 1 noncommunicating contralateral horn (often with ipsilateral renal agenesis)
Bicornuate uterus – 2 separate uterine cavities share a common lower segment and a single cervix
Arcuate uterus – This is a heart-shaped uterus
Uterus didelphys (didelphic uterus) – The paramesonephric (Mullerian) ducts completely lack fusion, often with 2 compete uterine cavities and 2 cervices
Vaginal septum – This is usually a longitudinal band of tissue, often found in uterus didelphys
Congenital ureteral abnormalities
Congenital ureteral abnormalities are as follows:
Bifid ureters – The upper pole and lower pole ureters join proximal to the bladder
Double ureters – The upper pole ureter and lower pole ureter empty separately into the bladder
Ectopic ureter – Rarely, a ureter can insert into the bladder at some other location besides the trigone; the ectopic ureter usually enters caudally and can enter the urethra or even some point outside the urinary tract (eg, the distal third of the vagina)
Pelvic kidney – This is lower-than-normal positioning of the kidney; patients with an ectopic kidney have an approximately 15% incidence of other genital abnormalities
Ureterocele – This is a congenital defect in which the distal ureter balloons at its opening in the bladder; it is often associated with a duplicated urinary system
One of the most common pathophysiologic conditions within the lower female reproductive tract is uterine fibroids (myomas, leiomyomata uteri). Fibroids are benign smooth muscle tumors whose incidence is approximately 25% in the general population and can be even higher in the black population.
Symptomatic fibroids are a common indication for hysterectomy in the United States. They can be intramural (within the myometrium), submucosal (beneath the endometrium), or subserosal (beneath the serosa). Small subserosal fibroids can be surgically managed by means of hysteroscopic resection. Fibroids can be asymptomatic, or patients can present with menorrhagia, pelvic pressure, bowel symptoms, or urinary symptoms. Fibroids (especially submucosal) can be a cause of female infertility.
Endometriosis is the presence of ectopic endometrial glands and stroma. The exact incidence is unknown, because the only reliable method to diagnose the condition is direct visualization at the time of surgery (usually diagnostic laparoscopy). Endometriosis can lead to pelvic pain, dysmenorrhea, and infertility. Endometriosis implants can be found anywhere in the pelvis, and even extrapelvic implants have been reported.
Commonly, implants can be found on the ovaries, uterosacral ligaments, uterine serosa, and rectovaginal septum. The classic implant is blue-black in appearance, containing hemosiderin deposits (from trapped old blood). Frequently, however, the implants are nonspecific but atypical appearing. Treatment includes surgical ablation and medical management aimed at eliminating cyclic menstruation, such as oral contraceptives and gonadotropin-releasing hormone agonists.
Ureteral reflux is more common in females postnatally. Primary vesicoureteral reflux is usually due to congenital shortening and loss of longitudinal muscle of the intravesicular ureter. Secondary vesicoureteral reflux can be caused by anatomic and functional causes. Reflux and ureteropelvic junction (UPJ) obstruction are both congenital, and both may present as hydronephrosis.
Reflux may cause recurrent urinary tract infection and renal scarring and may lead to renal failure, especially in the pediatric population. UPJ obstruction can be caused by crossing vessels or nonperistalsis segments. Patients need an appropriate workup. Some patients with mild disease need no surgical intervention; others need intervention (such as nephrostomy, ureteral stent, or urinary diversion) to prevent loss of renal function.
An increased risk for ureteral injury exists during female pelvic surgery. If the ureter is damaged at the pelvic brim, then a primary ureteroureterostomy can be performed. This type of injury can result from clamping and incising the suspensory ligament of the ovary. Additionally, when pelvic anatomy is distorted, iatrogenic midureteral injury can occur–for example, in cases of ovarian cancer debulking surgeries or salpingo-oophorectomies in which pelvic adhesions or endometriosis exist.
If the ureteral injury is lower or more proximal to the bladder, as when the uterine arteries are clamped and incised during hysterectomy, then ureteroneocystostomy can be performed. The ureter is reimplanted into the bladder or a flap of bladder is made into a tube that can be anastomosed to the ureter. A so-called psoas hitch can be performed, in which the tube of bladder is sutured to the iliopsoas fascia above the iliac vessels. In this way, the ureter can be anastomosed to the bladder with less tension.
This approach is often required when the distal ureteral segment is transected and compromised, and it has a success rate of 95-100%. If the injury is to the lower two thirds of the ureter and the bladder cannot be brought up in the psoas hitch procedure, then a Boari flap or transureteroureterostomy can be performed. A pedicle of bladder is swung upward and used to bridge the gap to the injured ureter.
Pelvic hemorrhage can result from uterine atony after delivery, from trauma, or from vessel injury during surgical procedures. During cesarean section, several surgical methods can be used to control hemorrhage from uterine atony: uterine compression sutures (B-lynch sutures), uterine artery ligation, internal iliac artery ligation, and intrauterine tamponade balloons.
An important point regarding internal iliac artery (hypogastric artery) ligation is that ligation of the anterior division of the internal iliac artery is needed to control pelvic hemorrhage. Inadvertent ligation of the posterior division in part results in necrosis of the gluteal muscles.
Another method for controlling pelvic hemorrhage is uterine artery embolization, in which a catheter is advanced via the femoral artery, the bleeding point is identified with contrast imaging, and the branch of the uterine artery involved is embolized with an absorbable material.
In certain cases of hemorrhage, the ovarian vessels may intentionally or unintentionally become embolized. To embolize ovarian vessels, a catheter must be placed above the level of the renal artery and then advanced to the ovarian vessels; the mesenteric artery must be identified beforehand to prevent ischemic damage to the bowel.