The appendicular artery is a branch of the ileal or posterior caecal 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 is a blind muscular tube that arises from the caecum, which is the first part of the large bowel.
The appendix arises from the posteromedial surface of the caecum, approximately 2-3 cm inferiorly to the ileocaecal valve, where the taeniae coli c...
The Appleby procedure is a type of pancreatic cancer resection.
For some patients with pancreatic cancer involving the body and tail of the pancreas, involvement of the coeliac axis is a classic contraindication to pancreaticoduodenectomy (Whipple procedure).
With the Appleby procedure, ther...
The apple core sign, also known as a napkin ring sign (bowel), is most frequently associated with constriction of the lumen of the colon by a stenosing annular colorectal carcinoma.
The appearance of the apple-core lesion of the colon also can be caused by other diseases...
Apple-peel intestinal atresia, also known as type IIIb or Christmas tree intestinal atresia, is a rare form of small bowel atresia in which the duodenum or proximal jejunum ends in a blind pouch and the distal small bowel wraps around its vascular supply in a spiral resembling an apple peel. Oft...
The arc of Buhler (AOB) is a persistent embryonic anastomotic branch between the 10th and 13th ventral segmental arteries, resulting in a connection between the coeliac artery and superior mesenteric artery (SMA). This arch is independent of both the gastroduodenal and dorsal pancreatic artery.
The arc of Riolan (AOR), also known as the mesenteric meandering artery (of Moskowitz) or central anastomotic mesenteric artery, is an arterio-arterial anastomosis between the superior and inferior mesenteric arteries.
It is an inconstant artery that connects the proximal superio...
Areae gastricae are a normal finding on double contrast images of the stomach.
fine reticular network of barium-coated grooves between 1-5 mm islands/areas of gastric mucosa
may be seen in ~70-80% of patients if there is adequate high-density barium coating of the stomac...
A-rings are a type of distal oesophageal ring. They are above the B-ring and occur a few centimetres proximal to the gastro-oesophageal junction. They represent a physiological contraction of oesophageal smooth muscle covered by mucosa. A-rings are uncommonly symptomatic.
The arrowhead sign refers to the focal caecal thickening centred on the appendiceal orifice, seen as a secondary sign in acute appendicitis. The contrast material in the caecal lumen assumes an arrowhead configuration, pointing at the appendix.
The arrowhead sign is applicable only when enter...
Asbestos related disease, in particular affecting the lung, comprise of a broad spectrum of entities related to the inhalational exposure to asbestos fibres. They can be divided into benign and malignant changes 1-3.
Benign pleural and parenchymal lung disease
asbestos related benign pleural d...
Ascariasis is due to infection with the Ascaris lumbricoides adult worm and typically presents with gastrointestinal or pulmonary symptoms, depending on the stage of development.
Ascaris lumbricoides is widely distributed in tropical and subtropical regions and in other humid ar...
Ascaris-induced pancreatitis is the most common form of parasite-induced pancreatitis.
Ascariasis in parts of India is the second most common form of pancreatitis after gallstones 1. It is rare outside of endemic regions however.
The presentation will be si...
The ascending colon is the second part of the large bowel.
The ascending colon is the continuation of the caecum superior to the ileocaecal valve. It is secondarily retroperitoneal, although it has its own mesentery in approximately 25% of patients and is 15 cm in length 1,2.
Ascites is defined as an abnormal amount of intraperitoneal fluid.
Patients with a large volume of ascites can present with abdominal distension (which may be painful), nausea, vomiting, dyspnoea and peripheral oedema 7, 9.
Ascitic fluid is traditionally chara...
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...
Atrio-oesophageal fistulas are rare pathological connections between the left atrium and the oesophagus.
The presentation is non-specific. Patients may complain of fever, malaise, and/or dysphagia, or present with neurological symptoms 3.
The chief cause of ...
Atrophic gastritis is a chronic condition of autoimmune and non-autoimmune aetiology.
Two types of atrophic gastritis have been described 1-3:
type A: autoimmune
gastric body and fundus atrophy secondary to antiparietal cell antibodies
decreased secretion of acid and intrinsic fa...
Autoimmune pancreatitis (AIP) is a form of chronic pancreatitis associated with autoimmune manifestations on clinical, histological, and laboratory grounds 1.
Distinguishing this entity from other forms of chronic pancreatitis (such as alcohol-induced) is important as steroid treatment is effec...
Autosplenectomy denotes spontaneous infarction of the spleen with resulting hyposplenism.
Autosplenectomy is most frequently encountered in patients with homozygous sickle cell disease, although it has also been reported in pneumococcal septicaemia 1, and SLE 2. The demographics t...
Backwash ileitis is seen in patients with ulcerative colitis (UC), where the entire colon is involved. In such cases the terminal ileum is oedematous.
Backwash ileitis extends contiguously backward from the caecum without skip regions. One source estimates it to occur in 6% of patients with UC,...
The ball of wool sign, also referred to as the yarn sign or congealed water lily sign, is an ultrasound appearance, representing degeneration of hydatid cysts (WHO class CE 4). The inner side of the cyst detaches from the cyst wall and folds on itself, causing a change from anechoic (fluid) to a...
The Balthazar score is a subscore within the CT severity index (CTSI) for grading of acute pancreatitis.
The CTSI sums two scores:
Balthazar score: grading of pancreatitis (A-E)
grading the extent of pancreatic necrosis
The Balthazar score was originally used alone, but the addition of a sc...
Bannayan–Riley–Ruvalcaba syndrome (BRRS or BRR syndrome) is a very rare autosomal dominant hamartomatous disorder caused by a mutation in the PTEN gene. It is considered in the family of hamartomatous polyposis syndrome.
There are no formal diagnostic criteria for this disease, but characterist...
Bariatric intragastric balloon therapy is a relatively new form of bariatric surgery, which involves a balloon being endoscopically placed and inflated inside the lumen of the stomach. The balloon resides in the stomach and the mechanism of action is presumably due to stretching the stomach, ind...
Barium peritonitis is a rare complication of gastrointestinal fluoroscopy, and occurs when there is gastrointestinal tract perforation and spillage of barium into the peritoneal cavity.
Barium in the peritoneal cavity is treated as a foreign body with resultant immune response that ...
Barium studies of the small intestine are still considered an effective modality to show the bowel loops in a cost-effective way.
Small bowel follow through (SBFT) or transit study
routine investigation for delineation of all parts the small bowel
done with barium meal after havin...
Barium sulfate (BaSO4), often just called barium in radiology parlance, is a salt of barium, a metallic chemical element with atomic number 56. Barium is considered one of the heavy metals. Unlike barium and many of its other salts, barium sulfate is insoluble in water and therefore very little ...
Barium swallow is a dedicated test of the pharynx, oesophagus, and proximal stomach, and may be performed as a single or double contrast study. The study is often "modified" to suit the history and symptoms of the individual patient, but it is often useful to evaluate the entire pathway from the...
Barrett oesophagus is a term for intestinal metaplasia of the oesophagus. It is considered the precursor lesion for oesophageal adenocarcinoma.
Barrett oesophagus is thought to have a prevalence of 3-15% in patients with reflux oesophagitis. Mean age at diagnosis is 55 years old 5...
Beak sign in pyloric stenosis is one of the fluoroscopic (barium meal) findings which is useful in the diagnosis of congenital hypertrophic pyloric stenosis.
A beak-like tapering projection of barium is seen entering into the narrowed and compressed pyloric ...
Benign oesophageal lesions are less symptomatic than malignant oesophageal lesions, making up for only 1% of clinically apparent oesophageal lesions.
oesophageal leiomyoma (>50%)
oesophageal fibrovascular polyp (~12.5%)
may contain fat
oesophageal duplication cyst (10...
Benign post-traumatic pseudopneumoperitoneum is the presence of ectopic gas typically between the 5th-10th intercostal spaces after high-energy trauma in the absence of other causes of pseudopneumoperitoneum such as pneumomediastinum 9.
Occurs with an incidence of 5% post-trauma...
The Bethesda criteria are an alternative to the Amsterdam criteria for the clinical diagnosis of hereditary non-polyposis colorectal cancer (HNPCC).
Diagnosis of HNPCC is made if any of the following criteria are fulfilled:
Amsterdam criteria are met
2 or more HNPCC related malignancies
Bezoars are accumulations of indigestible contents within the gastrointestinal tract 2.
They are known to cause small bowel obstruction and sometimes CT may demonstrate the bezoar as a mass in the obstructed segment of bowel. The bezoar may be outlined by fluid in the proximally dilated small ...
Bilateral adrenal gland hyperenhancement or intense adrenal enhancement may be a feature of hypotension and forms part of the CT hypoperfusion complex.
Adrenal gland hyperenhancement has been described in paediatric and small adult series or individual cases of haemorrhagic shock, pancreatitis,...
Biliary cast syndrome is a complication that occurs after liver transplantation, where dark solid bilirubin casts develop in the biliary tree, causing biliary obstruction.
This should be differentiated from biliary sludge, which represents thickened bile that has not precipitated.
Biliopancreatic diversion was a development on the jejunoileal bypass type of bariatric surgery. It can be performed with or without a duodenal switch.
The procedure involves
distal gastrectomy, with formation of a gastric pouch
gastroenterostomy, with formation of a ~250 cm Roux limb (normal...
Billroth II gastrojejunostomy is a procedure that has been performed for tumour or severe ulcer disease in the distal stomach.
There are many variations on the procedure, but they generally involve resection of the diseased portion of the distal stomach and a side-to-side anastomosis of the res...
The bird's beak sign of the oesophagus is used to refer to the tapering of the inferior oesophagus in achalasia. The same appearance (although it is difficult to see the similarity) is also referred to as the rat-tail sign.
The appearance, although classically occurring in primary achalasia, ca...
The bird beak sign of the right colon is tapering obstruction of the inferior part of right colon seen on contrast enema or CT scan with rectal contrast indicating caecal volvulus.
This sign can help to differentiate caecal volvulus from caecal bascule, in particular on a contrast/barium enema ...
Bird's beak sign of the sigmoid is one of the signs of sigmoid volvulus. It represents gradual narrowing/tapering of sigmoid colon up to the level of obstruction during contrast/barium insertion to the rectum or on CT.
When located in the sigmoid colon, it suggests the diagnosis of sigmoid volv...
Blind loop syndrome (or "blind pouch syndrome") is an event that may occur after an end-to-end or end-to-side bowel anastomosis. Dilatation and stasis of the bypassed bowel may lead to bacterial overgrowth, breakdown of bile salts, and result in nutritional problems. It may even eventually lead ...
A helpful mnemonic for remembering the features of a Bochdalek hernia is:
B: back and medial, usually on the left side
B: bad (associated with pulmonary hypoplasia)
Body packing refers to the internal concealment of drugs within the gastrointestinal tract or other orifices. People who do this may be called body packers, (drug) mules, stuffers, couriers or swallowers. Drugs may be concealed within condoms, foil, latex or cellophane.
There is ...
Boerhaave syndrome refers to an oesophageal rupture secondary to forceful vomiting and retching.
It tends to be more prevalent in males, with alcoholism a risk factor. The estimated incidence is ~ 1:6000.
They are often associated with the clinical triad of...
Bouveret syndrome refers to a gastric outlet obstruction secondary to impaction of a gallstone in the pylorus or proximal duodenum. Thus, it can be considered a very proximal form of gallstone ileus.
Bouveret syndrome occurs most commonly in elderly women. The presenting...
Bowel and mesenteric trauma can result from blunt force, penetrating and iatrogenic trauma.
The bowel and mesentery are injured in ~2.5% (range 0.3-5%) of blunt force abdominal trauma 1,3,5,8. However not surprisingly, bowel and mesenteric injuries are more frequent after penetrat...
This is a basic article for medical students and other non-radiologists
Bowel dilatation is a relatively non-specific sign than can be seen on most imaging modalities. In bowel obstruction, dilatation may be demonstrated on a plain radiograph providing the bowel is filled with gas.
Bowel obstructions are common and account for 20% of admissions with "surgical abdomens". Radiology is important in confirming the diagnosis and identifying the underlying cause.
Bowel obstructions are usually divided according to where the obstruction occurs, and since imaging appearances, und...
Bowel perforation can occur in many different settings, but the more common are
bowel obstruction (both small and large)
severe ulcer disease
direct tumour invasion
iatrogenic e.g. perioperative
Oesophageal perforation is technically a bowel...
This is a basic article for medical students and other non-radiologists
Bowel perforation is an acute surgical emergency where there is a release of gastric or intestinal contents into the peritoneal space.
This is a summary article; read more in our article on bowel perfora...
A mnemonic to remember causes of bowel sacculation is:
C: Crohn disease
Bowel wall thickening is a useful finding on imaging studies and has a number of different causes.
The reason for bowel wall thickening depends on the underlying etiology, but includes submucosal edema, hemorrhage, and neoplastic infiltration.
In describing bo...
Bronchogenic cysts and oesophageal duplication cysts are embryological foregut duplication cysts and are also differential diagnoses for a cystic mediastinal mass.
asymptomatic bronchogenic cyst
symptomatic oesophageal cyst in the case of peptic ulceration
Brunner gland adenomas are hyperplastic areas of the Brunner glands within the duodenum that are greater than 1 cm. They tend to be 1-2 cm in diameter, although case reports have described tumours of up to 12 cm diameter. Where the diameter of focal hyperplasia is less than 1 cm, the term Brunne...
Brunner gland hyperplasia results from disproportionate overgrowth of Brunner glands in the duodenum as a result of hyperacidity.
Hyperplasia begins at the pylorus and extends distally within the first 2/3 of the duodenum. Where the focal growth of hyperplastic cells is greater than 1cm in diam...
Major duodenal papilla is a conic or cylindric protuberance at the medial aspect of the descending or horizontal duodenum at the site of the sphincter of Oddi. It is finding on small bowel follow-though (and endoscopy) and has a relatively long differential.
On cross sectional imaging, the unde...
Buried bumper syndrome (BBS) is a rare but important complication in patients with percutaneous endoscopic gastrostomy (PEG) tube, occurring by migration of the internal bumper along its track. The tube may get lodged anywhere between the gastric wall and the skin and lead to life-threatening co...
CA 19-9 (carbohydrate antigen 19-9 or cancer antigen) is a serum antigen (monosialoganglioside) that has increased diagnostic use in the management of several malignancies, mainly of hepatopancreaticobiliary origin. It is non-specific, however, and can rise in both malignant and non-malignant co...
The caecal bar sign is a secondary sign in acute appendicitis. It refers to the appearance of inflammatory soft tissue at the base of the appendix, separating the appendix from the contrast-filled caecum.
Caecal bascule is an uncommon type of caecal volvulus in which the caecum folds up over itself in an anteromedial orientation. In contrast to the more common forms of volvulus, there is no axial "twisting" component 4. A caecal bascule may occur in the setting of a large and mobile caecum and c...
Caecal volvulus describes torsion of the caecum around its mesentery which often results in obstruction. If unrecognised, it can result in bowel perforation and faecal peritonitis.
Caecal volvulus accounts for ~10% of all intestinal volvuluses, and generally occur in somewhat youn...
The caecum 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 ileocaecal valve, above which the large intestine continues as the ascending colon. The caecum measures 6 cm in length and can have ...
Candida oesophagitis is the most common cause of infectious oesophagitis that commonly affects immunocompromised patients. On imaging, it is characterised by irregular plaque-like lesions separated by normal mucosa and small (<1cm) ulcers, which are assessed on oesophagogram studies.
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 symptoms of carbolic acid poisoning can be recalled using the mnemonic:
C: CNS depression
C: constricted pupil
C: carboluria (smoky urine)
C: corneal deposition
Serum carcinoembryonic antigen (CEA) is a cell-adhesive glycoprotein that was discovered in colorectal cancer in 1965, and is hence one of the oldest and most used tumour markers. Its name derives from its normal expression in fetoembryonic liver, gut and pancreas tissue.
Normal range of CEA is...
Carcinogens are substances known to cause cancer. They include:
Nasopharynx / nasal passage
ionising radiation (not technically a substance)
polyaromatic hydrocarbons (PAH)
Carcinoid syndrome refers to a spectrum of symptoms that result from excessive hormone (mainly serotonin) secretion.
Occurs equally between the sexes, most commonly in the 40-70 year age group 3.
Diarrhoea is the most common and earliest symptom but others...
Carcinoid tumours are a type of neuroendocrine tumour that can occur in a number of locations. Carcinoid tumours arise from endocrine amine precursor uptake and decarboxylation (APUD) cells that can be found throughout the gastrointestinal tract as well as other organs (e.g. lung). In general, t...
Carcinosarcomas are highly malignant biphasic tumours with both carcinomatous (epithelial) and sarcomatous (bone, cartilage, or skeletal muscle) components.
It can arise in many organs:
lung 5: pulmonary carcinosarcoma
oesophagus 1: oesophageal carcinosarcoma
genitourinary tract ...
The Carman meniscus sign describes the lenticular shape of barium in cases of large and flat gastric ulcers, in which the inner margin is convex toward the lumen. It usually indicates a malignant ulcerated neoplasm; in cases of benign gastric ulcers, the inner margin is usually concave toward th...
The Carney triad (not to be confused with the related Carney Stratakis syndrome, or the unrelated Carney complex) is a rare syndrome defined by the coexistence of three tumours:
extra-adrenal paraganglioma (e.g. spinal paraganglioma)
initially, only functioning extra-adrenal paragangliomas wer...
The cases featured in these video lectures are specifically selected to teach important concepts in radiology over a broad range of topics. The tutorials vary in difficulty from basic to advanced. For maximum learning, try the cases for yourself in Radiopaedia quiz mode first.
We love this ser...
Castleman disease, also known as angiofollicular lymph node hyperplasia or giant lymph node hyperplasia, is an uncommon benign B-cell lymphoproliferative condition. It can affect several regions of the body although commonly described as a solitary mediastinal mass.
There are two distinct subty...
The caterpillar sign is a radiological sign described in pyloric stenosis.
It refers to the appearance of stomach on an upper gastrointestinal radiographic series or plain abdominal radiograph 1,2. On these imaging modalities in a patient with pyloric stenosis, the stomach appears distended, ai...
A catchy and early learnt mnemonic for recalling some of the causes of pancreatitis is:
I GET SMASHED
E: ethanol (alcohol)
M: mumps (and other infections) / malignancy
S: scorpion stings/spider bites
Cavernous venous malformation, also traditionally referred to as a cavernous haemangioma (despite it not being a tumour) or cavernomas, are non-neoplastic slow flow venous malformations found in many parts of the body.
Despite the ubiquity of use of the traditional terms cavernoma...
Cavitary mesenteric lymph node syndrome is seen in association with coeliac disease and is characterised by the triad of:
low-attenuation lymphadenopathy that sometimes contains fat-fluid levels
CEC syndrome refers to the combination of coeliac disease, epilepsy and bilateral occipital calcifications. This is also known as Gobbi syndrome. Patients with cerebral calcifications and coeliac disease without epilepsy are considered as having an incomplete form of CEC syndrome 1.
The centipede sign is seen as engorged mesenteric vessels in cases of acute sigmoid diverticulitis which gives an appearance similar to a centipede 1.
The cervix sign of pyloric stenosis describes indentation of the pylorus into the fluid-filled antrum, seen in pyloric stenosis.
antral nipple sign
target sign of pyloric stenosis
shoulder sign of pyloric stenosis
Chagas disease, also referred as trypanosomiasis, is a tropical parasitic infection with a wide spectrum of clinical manifestations, since it can virtually affect any organ, but there are characteristic radiological features.
Chagas disease is endemic to Central and South America....
Chalasia is a condition most commonly identified in infants and young children, and is related to congenital incompetence of the lower oesophageal sphincter, allowing unrestricted reflux of gastric contents. This contrasts with achalasia, where there is restriction at the gastro-oesphageal junct...
Chilaiditi sign refers to the interposition of bowel, usually colon, between the inferior surface of the right hemidiaphragm and the superior surface of the liver. It may be misinterpreted as a true pneumoperitoneum resulting in unnecessary further investigations and/or therapy. The presence of ...
Chilaiditi syndrome is the anterior interposition of the colon to the liver reaching the under-surface of the right hemidiaphragm with associated upper abdominal pain; it is one of the causes of pseudopneumoperitoneum.
Colonic gas in this position may be misinterpreted as true pneumoperitoneum ...
Use only the size of the tumor during evaluation of response to chemotherapy has some pitfalls and limitations, especially when the estimated response for specific tumors such as gastrointestinal stromal tumour (GIST).
The Choi response criteria for GIST proposed that tumour attenuation could p...
Cholecystoduodenal fistula refers to a fistulous connection between the gallbladder and the duodenum. It is considered the most common type of enterobiliary fistulation.
Can vary but some can present with Bouveret syndrome 3 or a gallstone ileus.
There are many signs in radiology that are related to Christmas:
snowcap sign in avascular necrosis
in total anomalous pulmonary venous return
in pituitary macroadenomas
snowstorm appearance in complete hydatidiform and testicular microlithiasis
holly leaf sign in calcified pl...
Chronic mesenteric ischaemia is an uncommon type of intestinal ischaemia usually affecting elderly patients as a result of significant stenosis of two or more mesenteric arteries.
Normally seen in patients older than 60 years of age and is three times more common in women.
Chronic pancreatitis represents the end result of a continuous, prolonged, inflammatory and fibrosing process that affects the pancreas. This results in irreversible morphologic changes and permanent endocrine and exocrine pancreatic dysfunction.
The most common cause of chronic p...
The circumferential resection margin (CRM) is a term used in rectal carcinoma excision surgery (such as total mesorectal excision (TME)).
Pathologic evaluation of the resection margin on the excised rectum has been considered important for determining the risk of local recurrence. A margin of ≤...