C h a p t e r 4 0
Disorders of the Female Genitourinary System
1031
to five decades. Approximately 5% to 10% of repro-
ductive-age women have some degree of endometrio-
sis.
28,30
Risk factors may include early menarche and
late menopause; short menstrual cycles (<28 days), lon-
ger duration (>5 days) or heavier flow cycles; increased
menstrual pain; and other first-degree relatives with the
condition.
Several theories attempt to explain the origin of the
dispersed endometrial lesions that occur in women with
endometriosis.
6,7,28
One theory, the
regurgitation/implan-
tation theory
, suggests that menstrual blood containing
fragments of endometrium is forced upward through
the fallopian tubes into the peritoneal cavity. Retrograde
menstruation is not an uncommon phenomenon, and it
is unknown why endometrial cells implant and grow in
some women but not in others. A second theory, the
vas-
cular
or
lymphatic theory
, suggests that the endometrial
tissue may metastasize through the lymphatics or vascular
system. Another theory, the
metaplastic theory
, proposes
that dormant, immature cellular elements, spread over
a wide area during embryonic development, persist into
adult life and then differentiate into endometrial tissue.
Genetic and immune factors also have been studied as
contributing factors to the development of endometriosis.
Endometriosis usually becomes apparent in the
reproductive years when the lesions are stimulated by
ovarian hormones in the same way as normal endome-
trium, becoming proliferative, then secretory, and finally
undergoing menstrual breakdown. Bleeding into the
surrounding structures can cause pain and the develop-
ment of significant pelvic adhesions. Symptoms tend to
be more severe premenstrually, subsiding after cessation
of menstruation. Pelvic pain is the most common pre-
senting symptom; other symptoms include back pain,
dyspareunia, and pain on defecation and micturition.
Endometriosis is associated with infertility because of
adhesions that distort the pelvic anatomy and cause
impaired ovum release and transport.
The gross pathologic changes that occur in endome-
triosis differ with location and duration. In the ovary,
the endometrial tissue may form cysts (i.e., endome-
triomas filled with old blood that resembles choco-
late syrup [chocolate cysts]).
6
Rupture of these cysts
can cause peritonitis and adhesions. Elsewhere in the
pelvis, the tissue may take the form of small hemor-
rhagic lesions that may be black, bluish, red, clear,
or opaque (Fig. 40-11). Some may be surrounded by
scar tissue.
Endometriosis may be difficult to diagnose because
its symptoms mimic those of other pelvic disorders and
the severity of the symptoms does not always reflect the
Colon
Ovary
Rectouterine
pouch
Uterovesical fold
Uterine serosa
Bladder
Peritoneum
Umbilicus
Small bowel
Fallopian tube
FIGURE 40-10.
Common locations of
endometriosis in the pelvis and abdomen.
FIGURE 40-11.
Endometriosis. Implants of endometrium on
the ovary appear as red-blue nodules. (From Mutter GL, Prat J,
Schwartz DA.The female reproductive system, the peritoneum
and pregnancy. In: Rubin R, Strayer DS, eds. Rubin’s
Pathology: Clinicopathologic Foundations of Medicine. 6th ed.
Philadelphia, PA: Wolters Kluwer Health | Lippincott Williams &
Wilkins; 2012:903.)
