Items tagged “variants”
28 results found
Article
Uterus didelphys
Uterus didelphys is a type of Müllerian duct anomaly (class III) where there is a complete duplication of uterine horns as well as duplication of the cervix, with no communication between them.
Epidemiology
Didelphic uteri account for approximately ~8% (range 5-11%) of Müllerian duct anomali...
Article
Pancreas
The pancreas (plural: pancreata) is an unpaired, mostly retroperitoneal organ that has endocrine and exocrine functions, with a role in glucose metabolism and digestion.
Gross anatomy
Location
The pancreas is located at approximately the L1-L2 vertebral level in the anterior pararenal space o...
Article
Persistent right umbilical vein
A persistent right umbilical vein (PRUV) is an uncommon vascular anomaly which is often detected in utero.
Epidemiology
The estimated prevalence is ~2 per 1000 births 1,2.
Pathology
In the normal situation, the right umbilical vein begins to obliterate in the ~4th week of gestation and disap...
Article
Pancreas divisum
Pancreas divisum represents a variation in pancreatic ductal anatomy that can be associated with abdominal pain and idiopathic pancreatitis. It is characterized, in the majority of cases, by the dorsal pancreatic duct (i.e. main pancreatic and Santorini ducts) directly entering the minor papilla...
Article
Accessory peroneal muscles
Accessory peroneal muscles are a group of accessory muscles that can occur in the foot region as a normal variant in some individuals. The peroneal compartment is known as the lateral compartment of the leg.
Peroneus quartus muscle
Originally, several accessory muscles were distinguished in th...
Article
Multiple gallbladders
Multiple gallbladders are a rare anatomic anomaly characterized by the presence of one or more accessory gallbladder.
Epidemiology
Prevalence demonstrates regional variation between 1 in 50 (India) to 1 in 3800 (USA) 4.
Clinical presentation
Multiple gallbladders are typically found incident...
Article
Cyamella
A cyamella is a rare sesamoid bone that exists as a normal variant within the popliteus tendon, characteristically located at the lateral aspect of the distal femur in the popliteal groove.
Cyamella is best seen on the AP view of plain radiograph as opposed to fabella, which is best appreciated...
Article
Persistent hypophyseal canal
Persistent hypophyseal canal, also known as the craniopharyngeal canal when larger than 1.5 mm in diameter, is a rare congenital defect characterized by communication through the central skull base between the nasopharynx and the pituitary fossa.
Terminology
There are a number of terms that r...
Article
Extrarenal pelvis
Extrarenal pelvis refers to the presence of the renal pelvis outside the confines of the renal hilum; it is a normal anatomic variant.
Epidemiology
It is found in ~10% of the population 2.
Radiographic features
Ultrasound
An extrarenal pelvis usually appears dilated, erroneously suggesting...
Article
Episternal ossicles
Episternal (or suprasternal) ossicles are accessory bones and a normal variant of the sternum. They result from supernumerary ossification centers and are seen in ~4% (range 1-7%) of the population.
Gross anatomy
Episternal ossicles are usually located posterior or superior to the superior bor...
Article
Cerebellar agenesis
Cerebellar agenesis is a rare congenital abnormality which can result from failure to develop normal cerebellar tissue or destruction of normally developed tissue.
For a more general overview of cerebellar malformations, please refer to the article on classification systems for malformations of...
Article
Crista terminalis
The crista terminalis is a smooth muscular ridge in the superior aspect of the right atrium, formed following resorption of the right valve of the sinus venosus. It represents the junction between the sinus venarum, the "smooth" portion of the right atrium derived from the embryologic sinus veno...
Article
Interarterial course of the right coronary artery
Interarterial course of the right coronary artery may occur if the right coronary artery (RCA) has an aberrant origin from the left coronary sinus. The interarterial course occurs because the artery passes between the ascending aorta and the pulmonary trunk.
It is an uncommon anatomic variant w...
Article
Interarterial course of the left coronary artery
An interarterial course of the left coronary artery is defined as the origination of the left main or left anterior descending coronary artery from the right coronary sinus of Valsalva, with a course between the ascending aorta and the pulmonary artery trunk.
Terminology
An interarterial cour...
Article
Bipartite medial cuneiform
A bipartite medial cuneiform is an anatomical variant where there are two ossification centers involving the medial cuneiform. In many cases, the overall shape of the medial cuneiform is conserved, although the size of the two combined bones is larger than that of a normal medial cuneiform.
Epi...
Article
Accessory muscles of the ankle
Accessory muscles of the ankle are muscular anatomical variants that are usually asymptomatic but rarely cause symptoms or might be encountered on imaging studies.
The following accessory muscles around the ankle have been described 1-4:
posteromedial/flexor compartment
accessory flexor digit...
Article
Tibioastragalus anticus of Gruber muscle
The tibioastragalus anticus of Gruber (TAAG) muscle or anterior tibiotalus muscle is a rare accessory muscle of the ankle and an anatomical variant.
Summary
origin: lateral tibial surface and the interosseous membrane of the distal third of the lower leg
insertion: anterior superolateral neck...
Article
Peroneocalcaneus internus muscle
The peroneocalcaneus internus muscle, also known as fibulocalcaneus internus muscle of MacAlister, is a rare accessory muscle of the ankle and an anatomical variant with an estimated prevalence of about 1%. It is often bilateral if present.
Summary
origin: the medial surface of the distal...
Article
Tibiocalcaneus internus muscle
The tibiocalcaneus internus muscle is a rare accessory muscle of the ankle and an anatomical variant with an unknown prevalence.
Summary
origin: medial crest of the lower third of the tibia
insertion: medial surface of the calcaneus approximately 1-2 cm anterior to the Achilles tendon
Gross ...
Article
Extensor hallucis capsularis tendon
The extensor hallucis capsularis tendon, also known as secondary extensor hallucis longus, accessory extensor tendon of the first metatarsophalangeal joint, extensor ossis metatarsi hallucis or extensor ossis primi internodii hallucis is an accessory tendon or muscle of the ankle and an anatomic...