(1)
Department of Fetal Medicine and Obstetric & Gynecological Ultrasound, Manipal Hospital, Bangalore, Karnataka, India
11.1 Ovarian Torsion
Torsion is one of the most common gynaecological emergencies. It is the result of the twisting of a structure or a mass, with resultant compromise in vascular flow. The ovary is the most common organ that undergoes torsion. In addition, torsion may also be seen in paraovarian cysts or tubal masses like a hydrosalpinx. Very often, the fallopian tube twists along with the ovary, a phenomenon referred to as adnexal torsion. Ovarian torsion can result in ischaemia and necrosis, which in turn could lead to loss of the ovary (Fig. 11.1).
Fig. 11.1
Diagrammatic representation of ovarian torsion, with the ovary twisted on its ligamentary supports, causing ovarian ischaemia
Torsion is more common in ovaries that are enlarged with a mass and is less common in masses/ovaries that are fixed with adhesions, like in the cases of endometriosis and malignancies. Torsion in young girls is known to occur, at times, even in the absence of an ovarian mass. This has been explained by the possibility of long ligamentous supports of the ovary which increase the potential for ovarian torsion.
Right-sided torsion is more common than left, which is believed to be because of the presence of the sigmoid colon on the left, which reduces the likelihood of torsion due to limited space. Torsion is often triggered off by exercise or any other activity that causes a sudden change in intra-abdominal pressure. An early diagnosis of torsion is important for prompt management of these cases, so as to save the ovary. The present recommendation is laparoscopic detorsion of the ovary, with the ovary being left behind even if it looks gangrenous. This is because recovery of ovarian function is seen in more than 90% of ovaries on a follow-up scan done 6–8 weeks (up to 6 months) later. In the small remainder of cases, the ovaries become atrophic and no follicles are seen in follow-up scans (Oelsner et al. 2003). Surgical removal of the ovary is resorted to if there is a possibility of a malignant tumour or cyst, or in women who are postmenopausal or perimenopausal.
Diagnosis of torsion is by clinical suspicion, supported by ultrasound findings.
Clinical Features of Torsion
These are often non-specific and include:
Pain which is usually of sudden onset, sharp and localised to the lower abdomen. It is generally moderate to severe in intensity with many patients, therefore presenting at the ‘emergency’ department of hospitals. Pain could be acute or intermittent. Very often there is a history of some activity, bowel movement or exercise, that triggered off the pain.
History of nausea or vomiting is seen in about half the cases and a few may complain of pyrexia.
Tenderness and/or a palpable mass is often noted on examination.
In most studies, the diagnostic accuracy of ultrasound for diagnosis of ovarian torsion was found to be about 50–75 %. Therefore, in most centres, laparoscopy is considered as the gold standard for diagnosis of torsion in patients with a clinical suspicion of torsion. However, in experienced hands, ultrasound accuracy can be improved significantly with proper and careful evaluation, to above 90%.
Ultrasound Features of Torsion
Ultrasound findings in torsion can be grouped into two broad categories – the first category includes ultrasound features that are commonly seen in torsion but are not very specific, and the second category includes three ultrasound features that are more specific and therefore more useful in diagnosis. The three features in the second category are the whirlpool sign of the pedicle, abnormal Doppler flows and the follicular ring sign.
Common ultrasound findings in torsion (non-specific) (Figs. 11.2, 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, 11.9)
An enlarged ovary is a very common feature, but not specific to torsion. One of the reasons for an enlarged ovary in torsion is that torsion is known to occur in ovaries that are already enlarged (to 4–5 cm or more) due to functional cysts (like corpus luteal cysts), neoplastic masses (particularly dermoid cysts) and hyperstimulated ovaries. Congestion and oedema of the ovary secondary to torsion also contribute to its increased size.
Cysts, when present, are often haemorrhagic and thick walled.
Fig. 11.2
Ovaries enlarged with cysts: (a) dermoid, (b) fibroma, (c) neoplastic serous cystadenoma, (d) corpus luteal cysts. (c, d) Cysts show turbid contents and thick walls
The ovarian stroma appears oedematous (enlarged/swollen, excessive stromal tissue with no/few follicles). The stroma may appear heterogeneous and a little hyperechoic, because of haemorrhage and oedema. The entire ovary may appear solid, particularly on a transabdominal scan. There may be complete loss of architecture in necrotic torsed ovaries.
Torsed ovaries typically show multiple, peripheral, cortical follicles, because the oedematous stroma pushes the antral follicles to the periphery.
Fig. 11.3
Ovarian stroma in torsion. (a) Case of right ovarian torsion, with normal left ovary. The torsed right ovary shows peripheral, scattered antral follicles and thick hyperechoic, heterogeneous stroma, due to oedema and haemorrhage. (b) Solid-appearing torsed ovary on TAS. (c) Heterogeneous-appearing necrotic ovary with complete loss of architecture
The ovary may be placed in an unusual location, like anterior to the uterus or on the opposite side. It could also be impacted in the pouch of Douglas.
Fig. 11.4
Torsed ovaries in an unusual location. (a) Torsed right ovary seen on the left side of the abdomen. (b) Torsed ovary lying anterior to the uterus
The ovaries are generally tender to touch. If the patient has already been administered with some painkiller, then the tenderness may be significantly reduced.
Some amount of free fluid is a very common feature of torsion, but again not specific. This is because minimal free fluid is seen in a large variety of cases that have nothing to do with torsion.
Fig. 11.5
Free fluid in the POD
The pedicle of the torsed ovary appears as an extra-ovarian mass. On long section, it appears as an elongated and heterogeneous mass. On transverse section, it is circumscribed and generally has a bright echogenic centre like a ‘target sign’ which is the central axis of the twisted pedicle. This ‘target sign’ is very useful inidentifying the twisted pedicle in cases of torsion. The transverse section of the twisted pedicle can appear hyperechoic with multiple concentric hypoechoic stripes or may show hypoechoic beads within, which are nothing but engorged veins within the twisted pedicle.
Though the pedicle is a more specific feature (i.e. it is not seen in other conditions), because its appearance can vary and resemble a large number of other pelvic structures (like the fallopian tube), identifying it can be difficult, limiting its diagnostic utility in torsion.
Fig. 11.6 (a, b)
LS of the pedicles of torsed ovaries, appearing as an elongated, heterogeneous mass in two different cases (arrows)
Fig. 11.7
TS of pedicles of torsed ovaries in three different patients. The pedicle appears as a circumscribed mass (a) that is hyperechoic with multiple concentric hypoechoic stripes (arrow), (b) has hypoechoic beads within (engorged veins) (arrows), (c) has a bright echogenic centre – ‘target sign’
Fig. 11.8
Pedicles of torsed ovaries in two different cases (a, b) showing varied, atypical appearance, making them difficult to identify
Often the tube gets torsed along with the ovary. This is difficult to identify on ultrasound, because other than the fimbrial end, the tube does not have specific features to help identify it. Only occasionally (more often if there is fluid surrounding it), one may see a thickened segment of the fallopian tube close to the pedicle. This may or may not show flow, depending on the severity of torsion.
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