Abdominal and pelvic anatomy encompasses the anatomy of all structures of the abdominal and pelvic cavities.
This anatomy section promotes the use of the Terminologia Anatomica, the international standard of anatomical nomenclature.
The abdominal cavity is divided into two major compartments, the peritoneum and retroperitoneum, early in fetal development.
The parietal peritoneum is reflected over the peritoneal organs to form a series of supporting peritoneal ligaments, mesenteries and omenta. The peritoneal reflections ca...
Abdominal surface anatomy can be described when viewed from in front of the abdomen in 2 ways:
divided into 9 regions by two vertical and two horizontal imaginary planes
divided into 4 quadrants by single vertical and horizontal imaginary planes
These regions and quadrants are of clinical imp...
The accessory appendicular artery, also known as the artery of Seshachalam, is a branch of the posterior cecal artery. It arises from the ileocolic artery, and runs in the mesoappendix.
The exact prevalence of this accessory artery and its impact upon the risk of appendicitis varies among studi...
Agenesis of the appendix is extremely rare, with an incidence at surgery of approximately 1 in 100,000 laparotomies 1. It is most commonly due to a sporadic etiology. However in the rare genetic condition, familial apple peel jejunal atresia, absence of the appendix is a recognized feature. Also...
Ampulla (plural: ampullae) is an anatomical term used for tubular structures with a short segmental bulbous dilatation:
ampulla (fallopian tube)
ampulla (lacrimal system)
ampulla (semicircular ducts)
ampulla of Vater
ampulla (vas defe...
The ampulla of Vater is a conical structure at the confluence of the common bile duct (CBD) and the main pancreatic duct that protrudes at the major duodenal papilla into the medial aspect of the descending duodenum. The entire structure is encased by smooth muscle fibers that compose the sphinc...
The anal canal is the terminal part of the gastrointestinal tract. Anatomically, the anal canal is referred to as the terminal alimentary tract between the dentate line and anal verge. However, histologically it extends more proximally and includes the columns of Morgagni and anal sinuses. Surgi...
Anal margin or perianal skin is arbitrarily defined as a skin tissue with a radius of 5 cm from the anal verge, consisting of keratinizing squamous epithelial tissue containing hair follicles.
anal margin neoplasms
The anal sphincter is divided into an internal and external anal sphincter. It surrounds the anal canal.
Internal anal sphincter
continuation of inner rectal muscle
thickened, circular muscle fibers, up to 5 mm thick
composed of visceral muscle
External anal sphincter
The anal triangle forms the posterior half of the diamond-shaped perineum. The triangle's three corners are defined by the tip of the coccyx posteriorly and both ischial tuberosities anterolaterally. The anterior border is the transverse perineal muscles and the posterolateral borders are the sa...
The anal verge is part of the anal region and consists of a band of squamous epithelial tissue which lacks hair follicles and extends from the inter-sphincteric groove to the perianal skin.
The anatomy curriculum is one of our curriculum articles and aims to be a collection of articles that represent the core anatomy knowledge for radiologists and imaging specialists.
Head and neck anatomy
Abdominal and pelvic anatomy
Annular pancreas is a morphological anomaly which can cause duodenal obstruction. This condition is important to recognize, as radiologists are frequently the first to make the diagnosis.
The incidence is probably 1 in 250, however its incidence is not accurately reported 1. It is...
The anterior left perihepatic (or subhepatic) space is a potential space located between the diaphragm and the anterosuperior aspect of the left lobe of the liver.
The anterior left perihepatic space is separated from the posterior left perihepatic space by the left lobe of the ...
The anterior left subphrenic space is a potential space between the fundus of the stomach and the left hemidiaphragm 1,2.
The anterior left subphrenic space is a subcompartment of the left supramesocolic space.
medial: falciform ligament (separates it from the anter...
The anterior pararenal space is the portion of the retroperitoneum that lies between the posterior surface of the parietal peritoneum and the anterior reflection of the perirenal fascia.
It contains the duodenum, pancreas and retroperitoneal segments of the ascending and descendi...
The anterior right subhepatic space is a potential space between the inferior surface of the right lobe of the liver and the transverse colon.
The anterior right subhepatic space is separated from Morison’s pouch (also known as the posterior right subhepatic space) by the transve...
The aortic hiatus is one of the three major apertures through the diaphragm and lies at the level of T12. Strictly speaking, it is not a real aperture in the diaphragm, but an osseoaponeurotic opening between it and the vertebral column.
The hiatus is situated slightly to the left of the midli...
The appendicular artery is a branch of the ileal or posterior cecal branch of the ileocolic artery, which is from the superior mesenteric artery.
It courses posteriorly to the terminal ileum in the free wall of the mesoappendix to supply the appendix.
The appendix or vermiform appendix (plural: appendices) is a blind muscular tube that arises from the cecum, which is the first part of the large bowel.
The appendix arises from the posteromedial surface of the cecum, approximately 2-3 cm inferior to the ileocecal valve, where th...
The arc of Riolan, also known as the mesenteric meandering artery (of Moskowitz) or central anastomotic mesenteric artery, is an arterioarterial anastomosis between the superior and inferior mesenteric arteries.
It is an inconstant artery that connects the proximal superior mesen...
The ascending colon is the second part of the large bowel.
The ascending colon is the continuation of the cecum superior to the ileocecal valve. It is secondarily retroperitoneal, although it has its own mesentery in approximately 25% of patients and is 15 cm in length 1,2.
Asplenia refers to absence of the spleen thereby leading to deficient splenic function.
Seen in 3% of neonates with structural heart disease and in 30% of patients who die from cardiac malposition. The male-to-female ratio is 2:1.
Asplenia can be classified into two t...
The cecum (plural: ceca or cecums) is the first part of the large bowel and lies in the right lower quadrant of the abdomen.
Blind-ending sac of bowel that lies below the ileocecal valve, above which the large intestine continues as the ascending colon. The cecum measures 6 cm i...
Cantlie's line is a vertical plane that divides the liver into left and right lobes creating the principal plane used for hepatectomy. It extends from the inferior vena cava posteriorly to the middle of the gallbladder fossa anteriorly.
It contains the middle hepatic vein which divides the live...
The cloaca is the terminal portion of the hindgut. It is an embryonic structure (weeks 4-7) in which the distal ends of the gastrointestinal tract and urogenital system share a common channel. The most distal aspect of the cloaca is termed the cloacal membrane.
The cloaca, or portions of it, ca...
Celiac artery, also known as the celiac axis or celiac trunk, is a major visceral artery in the abdominal cavity supplying the foregut. It arises from the abdominal aorta and commonly gives rise to three branches: left gastric artery, splenic artery, and common hepatic artery.
The celiacomesenteric trunk (CMT) represents an uncommon vascular anatomical variant where both the celiac trunk and the superior mesenteric artery have a common origin from the abdominal aorta as a single trunk. Its frequency has been reported to occur in about 1.5% of the population 1,2.
The common bile duct (CBD), which is sometimes simply known as the bile duct, is formed by the union of the cystic duct and common hepatic duct (CHD).
On ultrasound imaging, it is not always possible to confidently see where the cystic duct enters the common hepatic duct to form t...
The common hepatic artery (CHA) is one of the 3 branches of the celiac artery.
The CHA is a terminal branch of the celiac artery, the largest branch coursing to the right.
It passes over anterior to the pancreas, and then inferiorly to the right in the lesser sac...
The common hepatic duct (CHD) is formed by the junction of the right and left hepatic ducts. It joins the cystic duct to form the common bile duct (CBD). It is approximately 4 cm long and 4 mm in diameter.
Together with the cystic duct (laterally) and cystic artery (superiorly), they form Calo...
This congenital intrahepatic portosystemic shunt classification was proposed by Park et al. in 1990 1:
type 1: single large vessel of constant diameter connecting the right portal vein to the inferior vena cava
type 2: localized, peripheral shunt with one or more communications in a single hep...
Congenital portosystemic shunts are rare, extrahepatic or intrahepatic, anatomical abnormalities shunting blood from the portal venous system to the systemic venous system and, thus, avoiding passage through the hepatic acinus.
The term “portosystemic shunt” can be used to refer t...
The conjoint tendon forms when the medial fibers of the internal oblique aponeurosis unite with the deeper fibers of the transversus abdominis aponeurosis. The conjoint tendon then turns inferiorly and attaches onto the pubic crest and pecten pubis 1. It forms part of the posterior wall of the i...
A crus (plural: crura) is an anatomical term used for a structure which resembles a leg.
crus (internal capsule)
crus (semicircular duct)
Multi-slice CT angiography of the splanchnic vessels is a powerful minimally invasive technique for evaluation of the splanchnic vascular system.
The actual procedure will vary depending on institutional protocol/guidelines but below is a typical description 2, 4:
The cystic duct connects the neck of the gallbladder to the common hepatic duct (CHD), draining bile to and from the biliary tree.
The confluence of the cystic duct and the common hepatic duct forms the common bile duct (CBD). The cystic duct is approximately 2-3 cm long and 2-3 ...
The descending colon is the continuation of the transverse colon after the left colic flexure, where the colon loses its mesentery.
The descending colon measures up to 25 cm in length and is secondarily retroperitoneal. It descends down attached to the left posterior abdominal w...
The diaphragm is the dome-shaped muscle that separates the thoracic cavity from the abdominal cavity, enclosing the inferior thoracic aperture.
The muscular fibers of the diaphragm originate around the circumference of the inferior thorax and converge to a common insertion point ...
The duodenojejunal (DJ) flexure or junction is the anatomical border between the duodenum and the jejunum.
The DJ flexure is located anterolateral to the aorta at the level of the upper border of the second lumbar vertebra. It makes a sharp turn anteroinferiorly to become the jej...
The duodenum is the first part of the small intestine and is the continuation of the stomach.
The duodenum is a 20-30 cm C-shaped hollow viscus predominantly on the right side of the vertebral column. It lies at the level of L1-3 and the convexity of the duodenum (called the duod...
Duplex appendix is a rare anomaly of the appendix and is usually discovered incidentally during surgery for appendicitis.
Duplication of the vermiform appendix is extremely rare. It is found in only 1 in 25,000 patients (incidence ~0.004%) operated on for acute appendicitis. Altho...
Ectopic pancreatic tissue, also known as heterotopic pancreatic tissue, refers to the presence of pancreatic tissue in the submucosal, muscularis or subserosal layers of the luminal gastrointestinal tract outside the normal confines of the pancreas and lacking any anatomic or vascular connection...
Epiploic appendages (or appendix epiploica, plural: appendices epiploicae) are peritoneum-lined protrusions of subserosal fat that arise from the surface of the large bowel.
Epiploic appendages typically measure 1.5 x 3.5 cm but have been reported to measure up to 15 cm in lengt...
The epiploic foramen (also called the foramen of Winslow) is a passage between the greater (general peritoneal space) and lesser sac (omental bursa), allowing communication between these two spaces.
It has the following borders:
anterior: the free edge of the lesser ...
Esophageal lymph node stations are those nodal stations in the neck, chest, and abdomen considered regional (rather than distant) for the purpose of esophageal cancer staging. This list reflects the map provided in the 8th edition of the American Joint Committee on Cancer (AJCC) Cancer Staging M...
The falciform ligament is a broad and thin peritoneal ligament. It is sickle-shaped (Latin: "falciform") and a remnant of the ventral mesentery of the fetus.
It is situated in an anteroposterior plane but lies obliquely so that one surface faces forward and is in contact with the peritoneum beh...
The eponym Fallopian may refer to:
Fallopian canal (facial nerve canal)
Fallopian tube (uterine duct)
Fallopian ligament (inguinal ligament)
History and etymology
It is named after Gabriele Falloppio (also known by his Latin name Fallopius), Italian anatomist (1523-1562).
The femoral canal is the medial compartment of the femoral sheath, an inverted cone-shaped fascial space medial to the common femoral vein within the upper femoral triangle. It is only 1-2 cm long and opens superiorly as the femoral ring. It serves two purposes:
allows the femoral vein to expan...
The femoral ring is the superior opening of the femoral canal. Its boundaries are:
medial: lacunar ligament
anterior: medial part of the inguinal ligament
lateral: femoral vein within the intermediate compartment of the femoral sheath
posterior: pectineal ligament overlying the pectineus mus...
Fishtail pancreas (also known as pancreas bifidum or bifid tail of the pancreas) is a rare anatomical variant of the pancreas produced by a branching anomaly during its development. It is named as such due to the fishtail-like appearance of the pancreas.
It is a rare anatomical an...
The foramina of Morgagni, also known as the sternocostal triangles, are small defects in the posterior aspect of the anterior thoracic wall between the sternal and costal attachments of the diaphragm. The internal thoracic vessels descend through these foramina to become the superior epigastric ...
The fossa of Landzert is a congenital mesentery defect. It is present in about 2% of autopsy series and is formed due to non-fusion of the inferior mesentery to the parietal peritoneum. It is found to the left of the fourth part of the duodenum.
The inferior mesenteric vein runs along its (ante...
The fossa of Waldeyer, also known as the mesentericoparietal fossa, is a congenital mesentery defect. It is found in about 1% of autopsy series and is formed due to non-fusion of the ascending mesocolon to the posterior parietal peritoneum.
The superior mesenteric artery runs along its (anterio...
Agenesis of the gallbladder describes the rare congenital absence of the gallbladder.
overall incidence is estimated <0.1% (range 0.04-0.1%)
reported 3:1 female predominance of symptomatic cases
equivalent gender distribution in autopsy cases
Gallbladder triplication is an extremely rare anomaly. There are three types of gallbladder triplication are described according to the number of cystic duct and their insertion:
Three gallbladders and three cystic ducts which unite to form a common cystic duct before joining the common bile du...
The gastric bubble is a radiolucent rounded area generally nestled under the left hemidiaphragm representing gas in the fundus of the stomach.
On a lateral radiograph, the gastric bubble is usually located between the abdominal wall and spine. It can be seen on chest or abdominal plain films. I...
Gastric lymph node stations were originally divided into 16 groups proposed by the Japanese Research Society for Gastric Cancer in 1963.
The areas of stomach which drain into regional lymph nodes:
cardia and proximal lesser curvature drain into left gastric lymph nodes, then int...
The gastroduodenal artery (GDA) is a terminal branch of the common hepatic artery which mainly supplies the pylorus of the stomach, proximal duodenum, and the head of the pancreas. Due to its proximity to the anterior wall of the first part of the duodenum, the gastroduodenal artery is one of th...
The gastrointestinal tract includes any part of the oral cavity, oropharynx, hypopharynx, esophagus, stomach, small bowel, colon, rectum and anal canal.
The gastro-esophageal junction (GEJ) (also known as the esophagogastric junction) is the part of the gastrointestinal tract where the esophagus and stomach are joined.
The GEJ is normally mostly intra-abdominal and is 3-4 cm in length. To some extent, the esophagus slides in and ...
The gastrosplenic ligament is a peritoneal ligament which is formed by ventral part of dorsal mesentery.
The gastrosplenic ligament extends from the greater curvature of the stomach to the hilum of the spleen. It contains the short gastric arteries.
To facilitate clinical description, the general topography of the abdomen is divided into four quadrants or nine regions by lines on the surface of the anterior abdominal wall. The four quadrants are created by vertical and horizontal lines passing through the umbilicus, whereas the nine regions...
The great vessel space is the fourth retroperitoneal space along with the anterior and posterior pararenal spaces, and the perirenal space 1,2. Unlike other retroperitoneal spaces, it is not well-defined by fascial planes and thus disease processes affecting other retroperitoneal spaces can also...
The Griffiths point, also known as Griffiths critical point, refers to the site of watershed anastomosis between the ascending left colic artery and the marginal artery of Drummond occurring in the region of the splenic flexure. Most anatomy texts describe the location as two-thirds along the tr...
The haustral folds (Latin: haustrum, plural: haustra) represent folds of mucosa within the colon. The haustra refer to the small segmented pouches of bowel separated by the haustral folds. They are formed by circumferential contraction of the inner muscular layer of the colon.
The outer longitu...
The hepatoduodenal ligament is a peritoneal ligament of lesser omentum containing the portal triad. 1
The hepatoduodenal ligament is a thickening of the right edge of the lesser omentum and forms the anterior margin of the epiploic foramen. It extends from the porta hepatis to th...
The hepatogastric (gastrohepatic) ligament is a peritoneal ligament that together with the hepatoduodenal ligament forms the lesser omentum. It derives from the embryonic ventral mesentery.
The hepatogastric ligament extends from the fissure of the ligamentum venosum and porta he...
The ileocecal valve separates the terminal ileum from the cecum and functions to regulate flow between these two structures and prevent reflux from the cecum into the small intestine.
The ileocecal valve consists of two muscular layers of ileum, an upper and lower lip, that are ...
The ileocolic artery is a branch of the superior mesenteric artery (SMA) that runs obliquely to the ileocecal junction. It divides into an ileal branch that supplies the terminal ileum and anastomoses with the terminal SMA and a colic branch. It also gives off anterior and posterior cecal arteri...
The ileum is the final part of the small intestine, following the duodenum and jejunum.
The ileum is not to be confused with the ilium - the associated plural/adjectival forms are ilea/ileal and ilia/ilial respectively.
The ileum is 2-4 m in length and is separated ...
The medical terms ileum and ilium have been causing great confusion to medical students and junior doctors alike for decades now. Only separated by one letter, the second vowel, the pronunciation may be identical, or differ slightly with the i sound resembling that in "bit" for ilium (ɪlɪəm) or ...
The inferior lumbar triangle, also known as the Petit triangle, is an anatomical space through which inferior lumbar hernias can occur.
inferiorly: iliac crest
anteriorly: external oblique muscle
posteriorly: latissimus dorsi muscle
floor: internal oblique muscle
The inferior mesenteric artery (IMA) is one of the three non-paired major visceral arteries in the abdominal cavity arising from the abdominal aorta and supplying the hindgut. It is the smallest of the three anterior visceral branches of the abdominal aorta.
The inferior mesenteric vein drains blood from the distal portion of the colon as well as the rectum (i.e. the hindgut).
Origin and course
The inferior mesenteric vein drains the mesenteric arcade of the hindgut (comprising of distal transverse, descending, and sigmoid colon). ...
The inferior pancreaticoduodenal artery is the first branch of the superior mesenteric artery (SMA), though it often arises from the first jejunal branch.
It anastomoses with branches of the superior pancreaticoduodenal artery (from the gastroduodenal artery) and it supplies the head of the pan...
The inferior thoracic aperture connects the thorax with the abdomen.
The inferior thoracic aperture is irregular in shape and is more oblique and much larger than the superior thoracic aperture. The diaphragm occupies and closes the inferior thoracic aperture, thereby separating ...
The inframesocolic space is the peritoneal space below the root of the transverse mesocolon. The supramesocolic space lies above the transverse mesocolon's root.
The compartment can be divided into two unequal spaces posteriorly by the mesentery of the small bowel as it runs from...
The inguinal canal is a passage in the anterior abdominal wall that transmits structures from the pelvis to the perineum formed by the fetal migration of the gonad from the abdomen into the labioscrotal folds.
The inguinal canal has an oblique course, is 4 cm in length and has tw...
The internal iliac lymph nodes (often shortened to internal iliac nodes) are the lymph nodes found adjacent to the internal iliac artery and its branches and drain the regions supplied by these vessels. This encompasses a large area from the genitalia anteriorly, the psoas muscle posteriorly and...
The internal oblique muscle (IOM) is one of the muscles that form the anterior abdominal wall. Inferiorly, it contributes towards the formation of the inguinal ligament.
origin: originates along the whole length of the lumbar fascia, from the anterior two-thirds of the iliac crest and ...
The ischioanal (or ischiorectal) fossa is a fat-filled space of the perineum.
The ischioanal fossa is a paired triangular-shaped space lateral to the anal canal with an apex directed anteromedially towards the pubic symphysis. Each ischioanal fossa is separated from the other by...
Isthmus (plural isthmi) is an anatomical term and refers to a slender structure joining two larger components. Some of these uses of the word isthmus are now rarely used or only seen in older texts and articles:
isthmus (auditory tube)
isthmus (auricle of the ear)
The jejunal and ileal branches of the superior mesenteric artery are variable in number.
They pass in the two layers of the mesentery to the jejunum and ileum and progressively divide and join in a series of anastomosing arcades. From the arcades, straight arteries (also known as the vasa recta...
The jejunum is arbitrarily defined as the proximal two-fifths of the small intestine and is, on average, about 3 m in length.
Compared to the ileum, the jejunum has more valvulae conniventes and fewer folds per unit length. Like the ileum, the normal jejunal wall thickness is les...
There are a few differences that can help differentiate jejunum and ileum 1-3:
jejunum: upper left part of the peritoneal cavity
ileum: lower right part of the peritoneal cavity
jejunum: greater caliber (<3 cm), thicker walls and more vascular
ileum: lesser calib...
Kommerell diverticula occur in some anomalies of the aortic arch system. It usually refers to the bulbous configuration of the origin of an aberrant left subclavian artery in the setting of a right-sided aortic arch. However, it was originally described as a diverticular outpouching at the origi...
This article lists a series of labeled imaging anatomy cases by system and modality.
CT head: non-contrast axial
CT head: non-contrast coronal
CT head: non-contrast sagittal
CT head: angiogram axial
CT head: angiogram coronal
CT head: angiogram sagittal
CT head: venogram axial
The large intestine (or large bowel) is a 1.5 meter muscular tube that extends from the cecum to the rectum. It has three outer longitudinal muscular layers called taenia coli, which are about 30 cm shorter than the length of the large bowel causing characteristic sacculations interrupted by inc...
The lateral fossae are concave depressions of peritoneum in the paravesical space that lie between the lateral umbilical folds and the lateral parietal peritoneum. The lateral fossae are the smallest of the anterior paravesical fossae, and typically partially contain the cecum and/or sigmoid col...
The lateral umbilical folds are bilateral raised ridges of parietal peritoneum in the deep aspect of the anterior abdominal wall overlying the inferior epigastric vessels. The paired folds originate medial to the deep inguinal ring and end at the arcuate line on the posterior aspect of the anter...
The left colic artery is the first branch of the inferior mesenteric artery.
It ascends retroperitoneally, dividing into two branches:
passes anteriorly to the left kidney, then enters the
transverse mesocolon, and passes superiorly to supply the upper part of the...