A monochorionic twin pregnancy is a type of monozygotic twin pregnancy where the twins share a single chorion. Depending on the sharing of the amnion this can be divided into two types.
monochorionic monoamniotic (MCMA) pregnancy: single amnion
monochorionic diamniotic (MCDA) pregnancy: two am...
A mono nostril falls under the midline facial defects which arise from cleavage anomalies. It can occur as part of many underlying conditions such as
holoprosencephaly: particularly alobar holoprosencephaly
Several other facial anomalies can be associated ...
A monozygotic (MZ) twin pregnancy results from the division of single zygote following fertilisation and shares similar genetic materials. These twins are therefore always of the same gender.
MZ twins account for approximately 30% of all twin pregnancies 1. The estimated incidence...
The mons pubis (plural: montes pubis) refers to the rounded protuberant skin-covered soft tissue overlying the symphysis pubis (in both sexes). It is most prominent in adult females.
In females it forms the most superior part of the vulva and it is also called the mons Veneris (plural: montes V...
MR defecating proctography is a dynamic study for evaluation of the pelvic floor and pelvic organ prolapse.
There are four phases of evaluation:
Method of evaluation
Many variations in the techniques described below exist.
MRI reporting guidelines for cervical cancer help maintain uniformity of reports and assessment of important imaging staging criteria.
The tumor should be measured in three orthogonal planes. Tumors with a maximum diameter >4 cm are usually not amenable to primary radical surgery.
Mucinous carcinoma of the cervix is an uncommon histological subtype of cervical cancer. It falls under the group of adenocarcinoma of the cervix.
As a general rule any mucin-producing tumor will produce very high T2 signal 1.
An enhancing lesion, irregular margin, ...
A mucocele simply refers to accumulation and expansion of a structure by mucus 1. It occurs in a variety of locations which are discussed separately:
paranasal sinus mucocele
lacrimal mucocele 3
mucocele of the mastoid (rare) 4
mucocele of the oral cavity e.g. ranula, mucous retention cysts...
The Müllerian ducts (or paramesonephric ducts) are paired ducts of mesodermal origin in the embryo. They run laterally down the side of the urogenital ridge and terminate at the Müllerian eminence in the primitive urogenital sinus.
In the female, they will develop to form the uterine tubes, ute...
Müllerian duct anomalies (MDAs) are congenital abnormalities that occur when the Müllerian ducts (paramesonephric ducts) do not develop correctly. This may be as a result of complete agenesis, defective vertical or lateral fusion, or resorption failure.
MDAs are estimated to occur...
The Müllerian duct anomaly classification is a seven-class system that can be used to describe a number of embryonic Müllerian duct anomalies:
class I: uterine agenesis/uterine hypoplasia
a: vaginal (uterus: normal/variety of abnormal forms)
Mullerianosis is a rare type of choristoma, in which normal Mullerian-derived structures (endometrium, endosalpinx, and endocervix) are ectopically located in another organ (e.g. the bladder) through a developmental anomaly. Mullerianosis differs from endometriosis in that at least two types of ...
MURCS association refers to the combination of:
MU: Müllerian duct aplasia
R: renal aplasia /renal agenesis
CS: cervicothoracic somite dysplasia
Mushroom cap sign is one of the important signs of deep rectosigmoid endometriosis seen on T2 weighted MRI sequence. It indicates the submucosal involvement in the rectosigmoid colon.
The hypertrophic muscularis propria appears as heterogeneous low signal intensity surrounded by the high signal...
Myometrial cysts are cysts seen in the myometrium and these can be differentiated appropriately based on location and sonological or Doppler features.
They can arise from variable etiology and include:
adenomyosis: these cysts are most often seen in the endomyometrial junc...
Myometritis is a term given when there is inflammation of the myometrium. It can fall under broader umbrella term of pelvic inflammatory disease and can often be associated with endometritis. It can arise in a variety of situation with puerperal situations being the most common. In some situatio...
Myxoid degeneration of leiomyoma is one of the rarer types of degeneration that can occur in a uterine leiomyoma. This term is related but not identical to the term myxoid uterine leiomyoma.
While this type of degeneration is generally considered rare, the highest prevalence for t...
Myxoid uterine leiomyomas are a relatively rare pathological subtype of uterine leiomyomas.
They are not to be confused with myxoid degeneration of a uterine leiomyoma which is a different entity.
Myxoid leiomyomas contain abundant myxoid material between smooth muscle ...
Nabothian cysts, also known as a retention cysts of the cervix 11, are non-neoplastic cystic lesions that occur in relation to the uterine cervix.
Nabothian is generally written without capitalization, i.e. 'nabothian', and not 'Nabothian', as it is an adjectival form derived from ...
The Naegele's formula is simple arithmetic method for calculating the EDD (estimated date of delivery) based on the LMP (last menstrual period).
To the date of the first day of the LMP (e.g. 22nd June 2008):
add seven days (i.e 29th)
subtract 3 months (i.e March)
add one year (i.e 2009)
Neu-Laxova syndrome is a lethal autosomal recessive multiple malformation syndrome with a heterogeneous phenotype.
The clinical spectrum can be quite wide and includes:
dermal / cutaneous
severe skin restriction
decreased fetal movement
Neural tube defect (NTD) refers to the incomplete closure of the neural tube in very early pregnancy, resulting in cranial defects or spinal dysraphism.
The neural tube comprises a bundle of nerve sheath which closes to form brain caudally and spinal cord rostrally. The closure should occur at ...
Non-gestational choriocarcinoma is choriocarcinoma occurring in the absence of a preceding gestation. As opposed to gestational choriocarcinoma, this is a much rarer situation.
In women, they often tend to occur in the ovary. Most ovarian non-gestational choriocarcinomas occur in mix...
Noonan syndrome (NS) is a genetically and phenotypically heterogeneous non-aneuploidic congenital RASopathy. Affected individuals can bear some clinical features similar to that of Turner syndrome.
The estimated incidence is at ~1 in 1000-2500 10. As individuals have normal numbe...
Noonan syndrome with multiple lentigines, previously known as LEOPARD syndrome (LS), is a rare autosomal dominant RASopathy that has many similarities to Noonan syndrome.
Despite a change in formal name, the 'LEOPARD' acronym is still useful to summarize the clinical feat...
Nuchal cord is a term given to the situation where there are one or more loops of umbilical cord wrapped around the fetal neck for ≥360°.
The prevalence is dependent on the extent of coiling and range from ~25% for a single loop to 2.5% for a double loop to ~0.5% for more than two...
The obstetric curriculum is one of our curriculum articles and aims to be a collection of articles that represent the core obstetric knowledge.
Topics pertaining to the normal and abnormal pregnancy, the gravid uterus and fetal environment, placenta, normal fetal development and fet...
This is a basic article for medical students and other non-radiologists
Obstetrics and Gynecology imaging for students curriculum represents a core set of common pathologies seen on the wards, in theater and in the emergency O&G patient.
Fundamental to most imaging of the O&G patient is an und...
An omphalomesenteric duct cyst is a type of true umbilical cord cyst.
The omphalomesenteric duct serves as a communication between the midgut and yolk sac In early embryonic life and usually obliterates between the 9-18th week of gestation. The omphalomesenteric duct cyst is an embry...
Oral-facial-digital syndromes (OFDS) are a group of rare genetic developmental disorder that affects the mouth, face, digits and also may cause some problems on the central nervous, kidney and the other organs.
Some publications have classified at least 13 forms of OFDS based on...
An ovarian adenofibroma is a type of ovarian epithelial tumor. Many authors however overlap this entity with an ovarian cystadenofibroma and consider these tumors often as part of an adenofibroma - cystadenofibroma spectrum.
Adenofibromas are benign compound tumors composed of interm...
The Ovarian-Adnexal Reporting and Data System Magnetic Resonance Imaging (O-RADS MRI) forms the MRI component of the Ovarian-Adnexal Reporting and Data System (O-RADS). This system aims to ensure that there are uniform unambiguous sonographic and MRI evaluations of ovarian or other adnexal lesio...
The Ovarian-Adnexal Imaging Reporting and Data System, (O-RADS), aims to ensure that there are uniform unambiguous sonographic and MRI evaluations of ovarian or other adnexal lesions, accurately assigning each lesion to a risk category of malignancy being present, which informs the appropriate m...
The Ovarian-Adnexal Reporting and Data System Ultrasound (O-RADS US) forms the ultrasound component of the Ovarian-Adnexal Reporting and Data System (O-RADS). This system aims to ensure that there are uniform unambiguous sonographic and MRI evaluations of ovarian or other adnexal lesions, accura...
The ovarian artery is a paired structure and is the main gonadal artery in females.
The ovarian artery arises anterolaterally from the aorta just inferior to the renal arteries and superior to the inferior mesenteric artery (between L2 and L3).
Descends caudally ...
Ovarian borderline mucinous cystadenomas are a subtype of ovarian mucinous tumors and, as the name stands, are intermediate between mucinous cystadenomas and mucinous cystadenocarcinomas.
They account for ~ 10-15% of all ovarian mucinous tumors.
They are microscopicall...
The most commonly adopted ovarian cancer staging system is the FIGO staging system. The most recent staging system is from 2014 1:
CT is considered the best imaging modality for staging ovarian cancer. 4.
stage I: tumor limited to the ovaries
tumor limited to one ovary
Ovarian carcinoid tumors are very rare sub type of ovarian tumor. They are usually classified under ovarian germ cell tumors (monodermal teratoma 5). The term carcinoid tumor of the ovary can be used to described primary ovarian carcinoid tumors or metastatic carcinoid tumors to the ovary. The f...
Ovarian choriocarcinoma is a rare sub type of ovarian germ cell tumor.
They account for less than 1% of ovarian tumors.
In pre-menarchal patients, the tumors manifest with iso-sexual precocity (approximately 50% of cases) and other symptoms associated with...
Ovarian collision tumors are an uncommon ovarian neoplasm where there is co-existence of two adjacent but histologically distinct tumors in an ovary with no histologic admixture at the interface.
The exact pathogenesis is not well known. They are most commonly composed of ovarian ter...
Ovarian cysts are commonly encountered in gynecological imaging, and vary widely in etiology, from physiologic, to complex benign, to neoplastic.
Small cystic ovarian structures should be considered normal ovarian follicles unless the patient is pre-pubertal, post-menopausal, pregnan...
An ovarian cystadenocarcinofibroma (CACF) is an extremely rare ovarian tumor. The tumor has a fibrous component is considered as the malignant counterpart of an ovarian cystadenofibroma (CAF) 1. There is very little literature on the imaging findings of these.
Ovarian cystadenofibromas are a relatively uncommon benign epithelial ovarian tumor where the fibrous stroma remains a dominant component of the neoplasm. As a group, they are thought to represent ~1.7 % of all benign ovarian tumors 3.
Lesions can be bilateral in ~15% of cases. Altho...
Ovarian cystadenoma is a broad term given to a certain types of ovarian epithelial tumors. This can include
ovarian serous cystadenoma
ovarian borderline serous cystadenoma
ovarian mucinous cystadenoma
ovarian borderline mucinous cystadenoma
Ovarian cystic neoplasms can be either benign or malignant and can arise from epithelial, stromal, or germ cell components. In general, the risk of malignancy in unilocular cystic tumors <10 cm in women over the age of 50 years is thought to be low 3,4.
ovarian mature cystic teratoma
Ovarian dysgerminomas are a type of germ cell tumor of the ovary. They are the most common malignant germ cell tumors of the ovary and are thought to account for ~1% of all ovarian neoplasms 5.
They are rare ovarian tumors that occur predominantly in young women (majority occurrin...
Ovarian ectopic pregnancies are rare when compared to other types of ectopic pregnancy such as tubal ectopic.
The ovary is the anatomic site of less than 3% of ectopic pregnancies 5.
Patients present with abdominopelvic pain during the first trimester (usu...
Ovarian embryonal carcinomas are rare and malignant germ cell tumors of the ovary.
It is found predominantly in children and adolescents (average age 14 years).
Precocious puberty or menstrual irregularity occurs in 60% 2. The tumor can secrete beta-hCG and...
Ovarian fibromas are a benign ovarian tumor of sex cord / stromal origin. Although fibromas account for ~4% of all ovarian neoplasms, they are the most common sex cord ovarian tumor.
Fibromas occur at all ages but are most frequently seen in middle-aged women.
Ovarian fibromatosis (OF) refers to a rare benign phenomenon where there is tumor-like ovarian enlargement due to diffuse ovarian fibrosis.
It may have a predilection towards younger pre-menopausal females (age range around 13-39 years) with a mean age of presentation of 25 years ...
Ovarian fibrosarcoma is a malignant mesenchymal fibroblastic tumor of the ovary that has multiple mitotic figures which is the most important factor in histopathological diagnosis (4 or more mitotic figure per 10 high power fields).
Ovarian fibrosarcoma is a very rare malignant o...
Ovarian fibrothecomas comprise tumors in the spectrum of ovarian sex cord / stromal tumors where there are components of both an ovarian fibroma and an ovarian thecoma.
Most occur in adult women, with ~66% in postmenopausal women. Although they account for ~1% of all ovarian tumo...
An ovarian follicle (also known as a Graafian follicle in its mature state) is the basic unit of female reproductive biology and is composed of roughly spherical aggregations of cells and contains a single oocyte.
An ovarian follicle can be initiated to grow and develop, culminat...
An ovarian follicular cyst is type of simple physiological ovarian cyst.
The terms "ovarian cyst" and "ovarian follilcular cyst" are often used interchangeably. These two terms describe lesions >3 cm, and it is important to differentiate them from an "ovarian follicle" which is <3 ...
Ovarian hyperstimulation syndrome (OHSS) is a complication of ovarian stimulation treatment (ovarian induction therapy) for in vitro fertilisation. Rarely, it may also occur as a spontaneous event in pregnancy (see spontaneous ovarian hyperstimulation later in the article).
The clinical syndrom...
Ovarian hyperthecosis (OHT) is a condition where there is a presence of luteinized thecal cells within a hyperplastic ovarian stroma.
Clinical manifestations include hyperandrogenism, obesity, hypertension, and impaired glucose tolerance. Virilization has been reported to...
A hypointense ovarian lesion on T2 weighted MRI is usually a sign of benignity. The low signal is considered to be due to fibrosis and blood products 1.
Lesions that can give this appearance include 1:
Ovarian lymphoma can refer to
primary involvement of the ovaries with lymphoma (i.e. primary ovarian lymphoma): very rare
secondary ovarian involvement of the ovaries with generalized lymphoma (i.e. secondary ovarian lymphoma): more common scenario
Mucinous cystadenocarcinoma of the ovary is a rare malignant ovarian mucinous tumor. This type can account for 5-10% of all ovarian mucinous tumors. It is a type of ovarian epithelial tumor.
Retrospective studies have suggested that many mucinous carcinomas initially diagnosed as pr...
Mucinous cystadenoma of the ovary is at the benign end of the spectrum of mucin-containing epithelial ovarian tumors.
The estimated peak incidence is at around 30-50 years of age.
They comprise approximately 80% of mucinous ovarian tumors and 20-25% of all benign ovarian tumors....
Ovarian mucinous tumors are a subgroup of ovarian epithelial tumors. They represent 10-15% of all ovarian tumors and ~10% of all malignant ovarian tumors. They are subdivided according to their malignant potential and clinical behavior into:
ovarian mucinous cystadenoma
ovarian borderline muci...
Ovarian serous cystadenocarcinoma is the malignant form of ovarian serous tumor, the most common type of ovarian epithelial tumor. It is the most common type of ovarian malignancy.
Increasingly, high-grade serous carcinoma and low-grade serous carcinoma are recognized as distinct tumor types ra...
Ovarian serous cystadenomas are a type of benign ovarian epithelial tumor at the benign end of the spectrum of ovarian serous tumors.
Serous ovarian tumors are traditionally described with a "cyst-" prefix because of their primarily cystic composition, e.g. cystadenoma, cystadenoca...
Ovarian serous neoplasms are the commonest of four general types of the epithelial ovarian tumors, and are more prevalent than the mucinous ovarian tumors.
Serous ovarian neoplasms are subdivided into benign, borderline, and malignant lesions according to their malignant potential and clinical ...
Ovarian Sertoli-Leydig cell tumors (SLCT), also known as ovarian androblastomas, are a subtype of ovarian sex cord-stromal tumor.
They are rare and only account for ~0.5% of all ovarian tumors. While they can present at any age, they typically present <30 years old, with a mean ag...
Ovarian teratomas are the most common group of ovarian germ cell tumors.
They can be divided into 3 main sub types
mature ovarian teratoma
immature ovarian teratoma
struma ovarii tumor
Ovarian thecomas are benign ovarian tumors of sex cord / stromal (mesenchymal) origin. They are thought to account for approximately 0.5-1% of all ovarian tumors. As ovarian thecomas secrete estrogen, they are described as functional ovarian tumors.
They typically present in older...
Ovarian torsion, also sometimes termed adnexal torsion or tubo-ovarian torsion, refers to rotation of the ovary and portion of the fallopian tube on the supplying vascular pedicle.
It can be intermittent or sustained and results in venous, arterial and lymphatic stasis. It is a gynecological e...
Ovarian transposition is a surgical procedure in which the ovaries are displaced from the pelvis before pelvic radiation therapy in order to protect them from radiation injury.
It is performed in premenopausal women with a variety of pelvic malignancies (e.g cervical cancer, rectal cancer, and ...
Ovarian tumors are relatively common and account for ~6% of female malignancies. This article focuses on the general classification of ovarian tumors. For specific features, refer to the subarticles.
Primary ovarian tumors
Surface epithelial-stromal ovarian tumors (60-70%)...
There are several ovarian tumors associated with endometrial thickening and this is often due to oestrogenic effects of the ovarian tumor.
Such tumors include:
ovarian epithelial tumors
endometrioid carcinoma of the ovary
may have synchronous endometrial carcinoma or endometrial hyperplasia,...
Ovarian vein syndrome is a relatively rare condition where a dilated ovarian vein (ovarian venous varix) causes notching, dilatation, or obstruction of the ureter. This is usually secondary to varicosities of the ovarian vein or ovarian vein thrombosis and occurs at the point where the ovarian v...
Ovarian vein thrombosis (actually most often thrombophlebitis) occurs most commonly in postpartum patients and can result in pulmonary emboli. A presentation is usually with acute pelvic pain in the postpartum period, then termed puerperal ovarian vein thrombosis or postpartum ovarian vein throm...
Ovarian yolk sac tumors, also known as endodermal sinus tumors, are a type of ovarian germ cell tumors.
Ovarian yolk sac tumor is a rare malignant ovarian germ cell tumor that usually occurs around the second decade of life. It is considered the most common malignant germ cell tum...
The ovaries are paired female gonads of the reproductive and endocrine systems. They lie within the ovarian fossa on the posterior wall of the true pelvis.
The ovaries are firm and ovoid in shape and measure approximately 1.5-3.0 cm × 1.5-3.0 cm × 1.0-2.0 cm (length x width x th...
Overlapping fetal fingers is an antenatal ultrasound observation where the fetal fingers are seen to overlap each other. It may be seen seen with a concurrent clenched fetal hand. If the hand is clenched typically the 2nd finger is seen to overlap the 3rd 4.
a well re...
p16 is a widely used immunohistochemical marker indicating expression of the cell cycle protein cyclin-dependent kinase inhibitor 2A, which is upregulated by human papillomavirus (HPV) infection. In the uterine cervix, p16 positivity supports the diagnosis of a high-grade squamous intraepithelia...
A papillary serous carcinoma of the cervix (PSCC) is an uncommon histological type of cervical cancer. It is considered a sub type of adenocarcinoma of the cervix.
Accodring to some studies, there was a bimodal age distribution, with one peak occurring before the age of 40 years ...
Papillary serous carcinoma of the endometrium is an uncommon histological subtype of endometrial carcinoma accounting for only 5-10% of all such tumors 2. It is considered type II endometrial adenocarcinoma and has a clinically aggressive form with an early extension of the tumor via Fallopian t...
Papillary squamous cell carcinoma (PSCC) of the cervix is a distinct subtype of squamous cell carcinoma of the cervix.
These tumors are characterized by a papillary architecture containing fibrovascular cores and moderate to severe dysplasia without any of frank keratinization and ko...
The parametrium is a band of fibrous tissue that separates the supravaginal portion of the cervix from the bladder. It extends on to its sides and laterally between the layers of the broad ligaments.
The uterine artery and ovarian ligament are located in the parametrium.
The parametrium is imp...
Paraovarian cysts are remnants of Wolffian duct in the mesosalpinx that do not arise from the ovary. They account for ~10-20% of adnexal masses 3,4.
Paraovarian cysts are also sometimes referred to as paratubal cysts or hydatid cysts of Morgagni 14.
They typically oc...
Paraovarian cystadenoma is a usually benign adnexal tumor that does not arise from the ovary. There is an association with Von Hippel Lindau syndrome.
typically seen as a unilateral cystic adnexal lesion
may be a simple cyst, or contain solid nodular a...
Parasitic leiomyomas are considered a type of extra-uterine leiomyoma and present as peritoneal pelvic benign smooth-muscle masses separate from the uterus.
This sort of leiomyoma likely originates as a pedunculated subserosal leiomyoma that twists and torses from its uterine pedicl...
The paraurethral ducts (or Skene ducts) drain the paraurethral glands of the female urethra. There is one duct, draining each gland, on each side, just proximal to the external urethral meatus.
History and etymology
Skene ducts are named after the Scottish-American gynecologist Alexander John...
Paraurethral duct cysts are retention cysts that form secondary to inflammatory obstruction of the paraurethral (Skene) ducts in females.
The cysts are lined by stratified squamous epithelium due to their origin from the urogenital sinus.
Partial hydatidiform mole is a type of hydatidiform mole, which in turn falls under the spectrum of gestational trophoblastic disease.
Clinical signs and symptoms such as abdominal pain, cramps of the lower abdomen and vaginal bleeding during pregnancy are common but non...
Parturition-induced pelvic instability is a rare condition seen in women following vaginal delivery.
The incidence of symphyseal rupture after vaginal delivery ranges from one in 600 to one in 30,000 deliveries 1.
Predisposing factors include multiparity, complicated delivery, ...
A pelvic abscess refers to a walled-off collection of pus in the pelvis.
Some of the causes include:
pelvic inflammatory disease (tubo-ovarian abscess)
iatrogenic e.g. post-surgical
inflammatory bowel disease
pelvic actinomycosis infection
Pelvic actinomycosis infection is a rare but serious infection caused by Actinomyces sp., an opportunistic gram-positive bacteria usually introduced by foreign bodies specially IUCDs, surgery, or trauma. It generally falls under the broader spectrum of pelvic inflammatory disease.
A dedicated pelvic MRI protocol is very useful for imaging assessment of cervical carcinoma.
Although the FIGO is a clinical staging, the 2009 revised FIGO staging encourages the use of MRI to complement clinical staging.
Imaging is optimally performed after three hours of fasting...
Pelvic congestion syndrome (some prefer pelvic venous insufficiency 9) is a condition that results from retrograde flow through incompetent valves in ovarian veins. It is a commonly missed and potentially-treatable cause of chronic abdominopelvic pain.
It tends to be more common ...
Pelvic inflammatory disease (PID) is a broad term that encompasses a spectrum of infection and inflammation of the upper female genital tract, resulting in a range of abnormalities.
The highest incidence is seen among sexually-active women in their teens, with 75% of cases being ...