Neural tube defect (NTD) refers to the incomplete closure of the neural tube in very early pregnancy.
The neural tube comprises of a bundle of nerve sheath which closes to form brain at the anterior end and spinal cord at the posterior end. The closure should occur at around the 28th day of co...
Non-gestational choriocarcinoma is choriocarcinoma occurring in the absence of a preceding gestation. As opposed to a gestational choriocarcinoma, this is a much rarer situation.
In women they often tend to occur in ovary. Most ovarian non-gestational choriocarcinomas occur in mixed...
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...
Oro-facial-digital syndromes (OFDS) are a generic name for a variety of genetically heterogeneous disorders that result in malformations of the mouth, teeth, jaw, facial bones, hands, and feet.
There are several (at least 13 2 ) recognised subtypes which include:
OFDS type I: G...
An ovarian adenofibroma is a type of ovarian epithelial tumor. Many authors however overlap this entity with an ovarian cystadenofibroma and consider these tumors are often as part of a adenofibroma - cystadenofibroma spectrum.
Adenofibromas are benign compound tumors composed of int...
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...
An 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 w...
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, pregnant, or the m...
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.
An ovarian cystadenofibroma (CAF) is 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.
Although generally classified as an epithe...
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 (1-3%) when compared to other types of ectopic pregnancy such as tubal ectopic.
Risk factors include pelvic inflammatory disease, IUCD use, endometriosis, in vitro fertilisation-embryo transfer 3, and previous adnexal surgery 4. Pa...
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. It contains a single oocyte.
An ovarian follicle can be initiated to grow and develop, culminating in ovulati...
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 generalised 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 ~20% 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 mucino...
Ovarian serous cystadenocarcinoma is an ovarian epithelial tumor at the malignant end of the spectrum of ovarian serous tumors.
They account for the largest proportion of malignant ovarian tumors 1, representing over 50-80% of all malignant epithelial ovarian tumors 4. The prevale...
Ovarian serous cystadenomas are a type of benign ovarian epithelial tumor at the benign end of the spectrum of ovarian serous tumors.
Serous cystadenomas account for ~60% of ovarian serous tumors 1. They are the commonest type of ovarian epithelial neoplasm. The peak incidence is ...
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 an 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...
Ovarian teratomas is 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 is often due to oestrogenic effects of the ovarian tumor.
Such tumors include:
ovarian epithelial tumors
endometroid carcinoma of the ovary
may have synchronous endometrial carcinoma or endometrial hyperplasia, prese...
Ovarian vein syndrome is a relatively rare condition where a dilated ovarian vein causes notching, dilatation, or obstruction of the ureter. This is usually secondary to varicoses of the ovarian vein or ovarian vein thrombosis and occurs at the point where the ovarian vein crosses the ureter.
Ovarian vein thrombosis (actually most often a 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 th...
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 ovoid in shape and measure approximately 1.5-3.0 cm x 1.5-3.0 cm x 1.0-2.0 cm (length x width x thickness) ...
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. It can be expressed in other neoplasms and in several normal human tissues. It can play an important role in gynecological malignancy and is a surrogate marker for HSILs (high-grade squamous intraepithelial lesions). It has also been employed to f...
Pallister-Killian syndrome (PKS) is an extremly rare chromosomal anomaly.
It may be more prevalent in woman of advanced age 4.
It is a polymalformative complex with tetrasomy of isochromosome 12p although many cases are mosaic.
The majority of cases are th...
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 (POCs) 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.
They typically occur in women at the ages of 20-40 years old.
Most are asymptomatic, although patient...
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.
It likely originates as a pedunculated subserosal leiomyoma that twists and torses from its uterine pedicle. The contact with ...
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.
paraurethral duct cyst
paraurethral duct abscess
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 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% cases being und...
Pelvic lipomatosis or pelvic fibrolipomatosis represents excessive deposition of fat in pelvis due to overgrowth of adipose cells leading to compression of pelvic organs.
The condition usually presents in patients 20-50 years of age. The condition is predominantly (2/3 of cases) s...
Pelvic masses in females carry a broad differential diagnosis:
benign adnexal cyst: 34%
pelvic malignancy: 14%
pelvic inflammatory disease: 8%
Extra-gynecological masses, e.g. colorectal carcinom...
A dedicated MRI protocol is crucial for accurate MRI evaluation of endometrial carcinomas.
Imaging is optimally peformed after 3 hours of fasting to reduce bowel peristalsis and following administration of an anti-peristaltic agent unless contra-indicated.
Supine position using a pelvic phased...
It is important to have a systematic way of approaching a case with pelvic pain in the exam.
Most examinations are performed using ultrasound. Always say that you would further assess the uterus with 3D ultrasound. You may also say that in my department we would perform a sonohysterogram. Only...
Evaluation of known endometriosis with MRI requires a slightly different protocol to a routine pelvic MRI (see Pelvic MRI protocol: routine), and should probably be reserved for known cases of endometriosis rather than for the assessment of pelvic pain.
IV (or IM) Buscopan® is administered to r...
Pelvic ultrasound is usually the initial modality for imaging gynaecologic pathology, including acute pelvic pain and chronic pelvic pain. The exam normally involves two components: a transabdominal (TA) evaluation and a transvaginal (TV) / endovaginal (EV) evaluation.
Normal ultrasound anatomy...
The term pelvis can refer to either the bony pelvis or the pelvic cavity.
The bony pelvis is formed by the sacrum and coccyx and a pair of hip bones ("ossa coxae"), which are part of the appendicular skeleton. Its primary function is the transmission of forces from the axial skelet...
Perigestational hemorrhage refers to hemorrhage that occurs around the fetus during the gestational period. The spectrum of hemorrhage includes:
chorionic hemorrhage: caused by the separation of the chorion from the endometrium
subchorionic hemorrhage: most common type, occurs between the cho...
Getting a film with perigestational hemorrhage in the exam is one of the many exam set-pieces that can be prepared for.
Transabdominal and transvaginal (TV) pelvic ultrasound shows an anteverted uterus with an intrauterine gestational sac. MSD is 20 mm in TV study with a single, l...
Perinatal lethal hypophosphatasia (PLH) is the most severe form of hypophosphatasia. If untreated, it is lethal in all cases.
The estimated incidence is at ~1:100,000 live births.
As with all hypophosphatasia cases, this is due to a mutation in chromosome 1q3...
The perineum is a diamond shaped region below the pelvic diaphragm and is divided by an imaginary line drawn between the ischial tuberosities into anteriorly the urogenital triangle and posteriorly the anal triangle.
The perineum is bounded by the pubis anteriorly, the ischial tu...
Peritoneal inclusion cyst (PIC) (also known as a peritoneal pseudocyst and benign cystic mesothelioma) is a type of cyst-like structure that appears in relation to the peritoneum and results from a non-neoplastic reactive mesothelial proliferation.
Peritoneal inclusion cysts occur...
There are several periurethral cystic lesions. These include:
female genitourinary tract:
Gartner duct cyst
epidermal inclusion cyst of the vagina
Skene duct cyst
Bartholin gland cyst
endometrial cyst of perineal-vulval-vaginal region
male genitourinary trac...
Perivascular epithelioid cells tumors (PEComas) are a group of related mesenchymal tumors and tumor-like conditions found in many locations. This group includes:
clear cell 'sugar' tumor of the lung
clear cell myomelanocytic tumor (CCMMT)
A persistent right umbilical vein (PRUV) is an uncommon vascular anomaly which is often detected in utero.
The estimated prevalence is ~2 per 1000 births 1,2.
In the normal situation, the right umbilical vein begins to obliterate in the ~4th week of gestation and disap...
It is important to have a systematic way of approaching a case with per vaginal bleeding in the exam.
intrauterine fetal demise
PET-CT is a combination of cross-sectional anatomic information provided by CT and the metabolic information provided by positron emission tomography (PET).
PET is most commonly performed with 2-[F-18]fluoro-2-deoxy-D-glucose (FDG). Fluorine-18 (F-18) is an unstable radioisotope and has a half-...
Physiological gut herniation is a natural phenomenon that occurs in early pregnancy. It usually occurs from around 6-8 weeks up until 12-13 weeks in-utero, after which the bowel returns to the abdominal cavity.
It occurs as a result of the bowel (particularly ileum) growing faster ...
Physiological pelvic intraperitoneal fluid refers to the presence of a small volume of free fluid in the pelvis, particularly the pouch of Douglas. It occurs in young females of reproductive age and can be a mimic of traumatic free fluid in abdominal trauma.
Unfortunately, pelvic free fluid may...
Getting a film with placental abruption (premature separation of placenta from uterus) in the exam is one of the many exam set-pieces that can be prepared for.
Transabdominal and transvaginal pelvic ultrasound show a single live fetus with gestational age of 27 weeks. The cervix i...
Placental calcification has been considered a manifestation of “aging” of the placenta. It commonly increases with gestational age.
Delayed placental calcification
Accelerated placental calcification
normal placental maturity
maternal thrombotic disorder...
Placental chorioangiomatosis is an extremely rare condition where numerous placental chorioangiomas involve the placenta. The individual chorioangiomas can be of varying size.
Recognised complications include
precipitation of fetal hydrops 2
fetal cerebral embol...
Placental fusion is a phenomenon that can occur in a twin pregnancy. This can occur to varying degrees. Determination of chorionicity on ultrasound can sometimes be difficult if there has been a placental fusion.
Placental grading (Grannum classification) refers to an ultrasound grading system of the placenta based on its maturity. This primarily affects the extent of calcifications. In some countries, the use of placental grading has fallen out of obstetric practice due to a weak correlation with advers...