Review of Adnexal Anatomy
The broad ligament (Figure 1) is a peritoneal fold that attaches the ovaries,
fallopian tubes,
and uterus to the pelvic sidewall and floor.
It is divided into three main sections,
named after the adjacent structure: the mesovarium (ovaries),
mesosalpinx (fallopian tubes),
and mesometrium (uterus).
The ovaries are also supported by the ovarian ligaments (sometimes referred to as the utero-ovarian ligaments) connecting them to the uterus.
The ovarian vessels are contained within the infundibulopelvic ligament,
also known as the suspensory ligament of the ovaries,
which is a fold of the broad ligament that connects the ovary laterally to the pelvic sidewall.
The ovarian arteries,
which originate from the abdominal aorta,
anastomose with the uterine arteries,
which originate from the internal iliac artery (Figure 2).
Mechanism of Torsion
Ovarian torsion occurs when an ovary rotates around its attachment structures,
usually both the infundibulopelvic and ovarian ligaments.
The term adnexal torsion is used when the fallopian tube turns as well.
Occasionally,
the fallopian tube twists around the infundibulopelvic and ovarian ligaments without involving the ovary,
a condition referred to as isolated tubal torsion.
Torsion may occur spontaneously,
but is often secondary to a lead point (usually a cyst or adnexal lesion).
When torsion causes occlusion of the blood supply within the infundibulopelvic ligament,
venous and lymphatic outflow are usually initially compromised to a greater degree than arterial inflow,
leading to a positive feedback cycle of increasing edema and vascular compression.
Eventually,
loss of ovarian function and necrosis can occur due to infarction.
Further complications include hemorrhage,
peritonitis,
and,
in the case of tubal torsion,
hydrosalpinx.
If not removed,
necrotic tissue involutes or amputates,
leaving sequelae of pelvic adhesions which can result in pelvic pain and infertility.
Torsion may also be intermittent,
with detorsion occurring before infarction,
or partial,
where perfusion is not fully compromised.
In these situations,
adverse effects are much less likely at the time of presentation,
however there remains potential for the condition to deteriorate into more constant or complete torsion.
Risk Factors
Ovarian masses,
especially cysts and neoplasms larger than 5 cm in diameter,
are the primary risk factor for ovarian and adnexal torsion [1].
Since these masses are related to reproductive hormones and their cycles,
risk of torsion increases in women of reproductive age,
undergoing ovulation induction,
and pregnancy.
Prior history of adnexal torsion also seems to be a risk factor: in a retrospective review of 216 cases,
close to 18% had suffered from at least one prior adnexal torsion event [2].
Risk factors for isolated tubal torsion are more varied.
Factors intrinsic to the tubal anatomy,
physiology,
and patholgy include: hydrosalpinx,
tubal tortuosity,
abnormal tubal peristalsis or spasms,
tubal ligation devices,
infection,
paratubal and broad ligament lesions,
ectopic pregnancy,
and congenital anomalies.
Extrinsic factors include pelvic adhesions,
endometriosis,
uterine enlargement (due to pregnancy or tumors),
and trauma [3-5].
A review of patients with isolated tubal torsion revealed that,
despite the multitude of possible causes,
24% had normal-appearing tubes.
The most common identified pathology was hydrosalpinx (18%,
unclear if this finding was a cause or effect of torsion).
13% percent had infection and 12% of torsions were diagnosed during pregnancy [6].
The most accepted current etiology of isolated tubal torsion focuses on hypermobility,
which may be due to hyperlaxity of pelvic ligaments and excessively elongated Fallopian tubes and mesosalpinx [7].
Incidence
A nationwide study conducted in South Korea using data from 2009-2011 found the overall incidence of ovarian/adnexal torsion among women of all ages to be 5.9 per 100,000,
while the incidence among among women of reproductive age (15–45 years) was higher at 9.9 per 100,000 women [8].
A more focused analysis of the pediatric population,
performed using United States hospitalization data,
estimated the incidence of ovarian/adnexal torsion in patients aged 1-20 years to be 4.9 per 100,000.
The same analysis revealed that oophorectomy was performed in 58% of the identified cases [9].
A separate review of pediatric literature found the mean age of ovarian/adnexal torsion to be 11.6 years,
of which 43.4% cases were premenarchal and 56.6% postmenarchal [10].
Ovarian and tubal masses account for the majority of torsion cases.
A retrospective analysis of 10 years of pathology records at a single institution found that neoplasms accounted for 46% and cysts 48% of cases ovarian/adnexal torsion.
Most of these lesions (89%) represented benign processes [11],
with teratoma as the most common type of neoplasm.
Torsion is more likely to occur with benign masses than malignant,
due to the higher likelihood of malignant masses being fixed in place.
Malignant masses are reported to account for fewer than 2% of total cases of torsion in premenopausal women [1],
with the rate increasing after menopause,
likely due to the higher prevalence of malignancy in this population.
Ovarian/adnexal torsion without an underlying mass may also be encountered,
particularly in the premenarchal and reproductive age populations where ongoing changes affecting the weight and size of the ovary can predispose to torsion.
Limited studies have proposed a relationship between enlargement due to early polycystic ovarian syndrome and ovarian/adnexal torsion without other identifiable pathology in premenarchal women [12].
Interestingly,
the right ovary and fallopian tube are more likely to undergo torsion.
Proposed explanations for this discrepancy are that the right ovarian ligament is longer than the left and that the sigmoid colon may play a role in preventing left-sided torsion [13].
Isolated tubal torsion is considerably rarer than ovarian/adnexal torsion.
One study reported an estimated rate of just 1 in 1.5 million women [14].
In the pediatric population,
a 20-year review of literature found that 55.6% of isolated tubal torsion cases were primary,
while 44.4% were secondary to an underlying adnexal pathology [5].
The same study found that 30% of the patients were premenarchal,
while 70% were postmenarchal.
The mean presentation age was 13.2 years.