4D syndrome is a term given to syndromic glucagonomas, a type of pancreatic endocrine tumour.
D: dermatitis (necrolytic migratory erythema, often involving the groin)
D: deep vein thrombosis
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 American Association for the Surgery of Trauma (AAST) injury scoring scales are the most widely accepted and used system of classifying and categorising traumatic injuries. Injury grade reflects severity, guides management, and aids in prognosis. At the time of writing (mid 2016), 32 differe...
The 1994 revision of American Association for the Surgery of Trauma (AAST) splenic injury scale is the most widely used grading system for splenic trauma at the time of writing (mid 2016).
subcapsular haematoma <10% of surface area
capsular laceration <1 cm dept...
AP supine radiograph can be performed as a standalone projection or as part of an acute abdominal series, depending on the clinical question posed, local protocol and the availability of other imaging modalities.
the patient is supine, lying on their back, either on the X-ray ...
The lateral decubitus abdominal radiograph is used to identify free intraperitoneal gas (pneumoperitoneum). It can be performed when the patient is unable to be transferred to, or other imaging modalities (e.g. CT) are not available. The most useful position for detecting free intraperitoneal ai...
The PA erect abdominal radiograph is often obtained in conjunction with the AP supine abdominal view in the acute abdominal series of radiographs. When used together it is a valuable projection in assessing air fluid levels, and free air in the abdominal cavity.
the patient is...
Abdominal adhesions are bands of scar tissue (ﬁbrous or ﬁbrous fatty), most often occurring as a complication of previous abdominal surgery.
Adhesions often occur with
multiple abdominal operations or previous postoperative intra-abdominal complications
history of intra-abdominal i...
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 herniations may be congenital or acquired and come with varying eponyms. They are distinguished primarily based on location and content. 75-80% of all hernias occur in the inguinal region.
Content of the hernia is variable, and may include:
small bowel loops
mobile colon segments (s...
An opacity projecting over the abdomen has a broad differential. Possibilities to consider include:
ingested, e.g. coins, batteries, bones, etc.
artifacts, e.g. object attached to the cloth of the patient like a safety pin or button
iatrogenic, e.g. haemostatic clips, gastric ...
This mnemonic helps to remember the relative echogenicity of abdominal organs on ultrasound:
Darling Parents So Love Kids
From most to least echogenic:
Abdominal paracentesis, more commonly referred to as an ascitic tap, is a procedure that can be performed to collect peritoneal fluid for analysis or as a therapeutic intervention.
diagnostic: especially for newly diagnosed ascites
determine aetiology of ascites
assess for bacter...
AP supine radiograph for neonates is a mobile examination performed on the neonatal unit. It can be taken as a standalone projection or as part of a series including a left lateral decubitus x-ray in cases of suspected perforation.
the patient is supine, lying on their back i...
The lateral view abdominal radiograph is a useful problem-solving view that can complement frontal views of the abdomen. It is different than the lateral decubitus view of the abdomen and looks more like a lateral lumbar spine view.
the patient may be either erect or recumbent...
Abdominal radiography can be useful in many settings. Before the advent of computerised tomography (CT) imaging, it was a primary means of investigating gastrointestinal pathology (and often allowed indirect evaluation of other abdominal viscera).
Although abdominal radiography has...
The abdomen, when looking from in front, is divided into nine regions by imaginary planes (two vertical and two horizontal) forming abdominal surface anatomy. The nine regions are of clinical importance when examining and describing pathologies related to the abdomen. The horizontal planes are o...
Abnormal bowel wall attenuation patterns on CT scan can be grouped under five categories:
water halo sign
fat halo sign
The first three patterns are seen on contrast studies.
It is defined as uniform enhancement of th...
A mnemonic used for abnormal collection of barium anywhere in the body :
Abnormal intra-abdominal gas may be seen on a chest or abdominal radiograph, or CT or MRI.
abnormally located bowel, e.g. Chilaiditi syndrome (bowel interposed between liver and hemidiaphragm), inguinal hernia
Abscesses are focal confined collections of suppurative inflammatory material and can be thought of as having three components 1:
central core comprised of necrotic inflammatory cells and local tissue
peripheral halo of viable neutrophils
surrounded by a 'capsule' with dilated blood vessels a...
The accessory appendicular artery (or artery of Seshachalam) or is a branch of the posterior caecal artery, which in turn 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...
Accessory parotid glands are a normal variant and represent ectopic salivary tissue present away and separate from the main parotid gland 1.
Accessory parotid glands are not rare and are seen in ~20% of the general population 2.
Located on the masseter muscle, ante...
The accordion sign is seen on CT examinations of the abdomen and refers to the similarity between the thickened oedematous wall of pseudomembranous colitis to that of an accordion. The appearance arises as a result of oral contrast being trapped between oedematous haustral folds and pseudomembra...
Achalasia (primary achalasia) refers to a failure of organised oesophageal peristalsis with an impaired relaxation of the lower oesophageal sphincter (LOS), resulting in often marked dilatation of the oesophagus and food stasis. Obstruction of the distal oesophagus (often due to tumour) has been...
The acute abdominal series is a common set of abdominal radiographs obtained to evaluate bowel gas.
The acute series is used for a variety of indications including:
determine the amount of bowel gas, with possible bowel distention
asses air-fluid levels
Acute cholecystitis refers to the acute inflammation of the gallbladder. It is the primary complication of cholelithiasis and the most common cause of acute pain in the right upper quadrant (RUQ).
most common in those with gallstones
fat, fertile (20-40), female patients...
Acute gastritis is a broad term for myriad causes of gastric mucosal inflammation.
Depends on the aetiology (see below).
nausea and vomiting
loss of appetite
infection: H. pylori (most com...
Acute necrotic collections (ANCs) are an early, local complication of necrotising pancreatitis.
The following are the latest terms according to the updated Atlanta classification to describe fluid collections associated with acute pancreatitis 1,2:
fluid collections in interstitia...
Acute pancreatitis refers to acute inflammation of the pancreas and is a potentially life threatening condition.
The diagnosis of acute pancreatitis is made by fulfilling two of the following three criteria 8:
acute onset of persistent, severe epigastric pain (i.e. pain consistent with acute p...
Acute pancreatitis refers to acute inflammation of the pancreas and is a potentially life threatening condition.
epidemiology is dependant on the cause of pancreatitis
gallstones, idiopathic, alcohol, malignancy, metabolic conditions
acute onset, severe ce...
Acute peripancreatic fluid collections (APFC) are an early complication of acute pancreatitis that usually develop in the first four weeks. After four weeks, the term pseudocysts is used. The absence of necrosis differentiates APFCs from acute necrotic collections (ANC), that is, APFCs occur in ...
Acute superior mesenteric artery occlusion, which can then result in an acute mesenteric ischaemia, can be a life threatening event related to the artery supplying the majority of the small bowel and right side of the colon.
An acute occlusion is an uncommon event that typically...
Acute superior mesenteric vein thrombosis is one of the less common causes of intestinal ischaemia.
For a general discussion refer to intestinal ischaemia.
Compared to acute superior mesenteric artery occlusion or ischaemia secondary to small bowel obstruction, acute superior m...
Duodenal adenocarcinoma is the most common primary malignancy of the duodenum.
Adenocarcinoma is the most common primary malignant neoplasm of the duodenum. It represents 0.3% of all gastrointestinal malignancies. It accounts for 50-70% of small bowel adenocarcinomas occurring ei...
Primary adenocarcinoma of the small bowel is about 50 times less common than colonic carcinoma.
Almost 50% of small bowel adenocarcinomas are found in the duodenum, especially near the ampulla. In the remaining cases, the jejunum is more commonly involved than the ileum1.
Adenomyomatosis of the gallbladder is a hyperplastic cholecystosis of the gallbladder wall. It is a relatively common and benign cause of diffuse or focal gallbladder wall thickening. It is most easily seen on ultrasound and MRI.
Adenomyomatosis is relatively common, found in ~9%...
Adrenal lymphangiomas, also known as cystic adrenal lymphangiomas, are rare, benign vascular adrenal lesions.
According to one series, there may be a slight right-sided and female predilection 3.
They usually remain asymptomatic throughout life and are almo...
Adrenal metastases are the most common malignant lesions involving the adrenal gland. Metastases are usually bilateral but may also be unilateral. When unilateral involvement is thought to be more prevalent on the left side (ratio of 1.5:1).
They are thought to be present in up to...
Adrenal washout can be calculated using the density value of an adrenal mass on non-enhanced, portal venous phase and 15 minutes delayed CT-scans. It is primarily used to diagnose adrenal adenoma.
[(HUportal venous phase) - (HUdelayed)] / [(HUportal venous phase) - (HUnon-enha...
Adynamic ileus is the failure of passage of enteric contents through small bowel and colon that is not mechanically obstructed. Essentially it represents the paralysis of intestinal motility.
Patients may be asymptomatic or present with symptoms similar to a mechanical bo...
Afferent loop syndrome is an intermittent partial or complete mechanical obstruction of the afferent limb of a gastrojejunostomy.
The syndrome classically refers to obstruction of the upstream limb of a side-to-side gastrojejunostomy, but has also been used to refer to the biliopancreatic limb ...
Human alpha fetoprotein (AFP) elevation may occur in a vast number of conditions:
liver tumours (hepatocellular carcinoma, hepatoblastoma)
<10 ng/ml is within normal limits
>20 ng/ml is above normal limits but has low specificity for tumor since it may occur in a setting of diffuse live...
AIDS defining illnesses are conditions that in the setting of a HIV infection confirm the diagnosis of AIDS, and do not commonly occur in immunocompetent individuals 2. According to the CDC surveillance case definition 1, they are:
bacterial infections: multiple or recurrent
Allgrove syndrome (also known as triple A syndrome) is an autosomal recessive condition that consists of three main findings:
The Alvarado score is a clinical predictor of the likelihood of acute appendicitis:
right lower quadrant tenderness (+2)
elevated temperature (37.3°C or 99.1°F) (+1)
rebound tenderness (+1)
migration of pain to the right lower quadrant (+1)
nausea or vomiting (+1
Amoebic colitis is a type of infectious colitis, more common in tropical and subtropical areas. The causative agent is a trophozoite of Entamoeba histolytica. The cyst form may live normally in the colon as commensal.
Amoebic colitis presents with abdominal pain and dysen...
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 term ampullary tumour generally refers to either benign or malignant neoplasms that arise from the glandular epithelium of the ampulla of Vater, including 1:
ampullary adenoma (adenoma of ampulla of Vater)
ampullary carcinoma (carcinoma of ampulla of Vater)
According to some authors, ampu...
The Amsterdam criteria are used in the diagnosis hereditary non polyposis colorectal cancer (HNPCC).
Amsterdam Criteria I
Initial description in 1991:
> or equal to 3 relatives with colorectal cancer (CRC)
> or equal to 1 case in a first degree relative
> or equal to 2 successive g...
Amyand hernia is a rare form of inguinal hernia in which the vermiform appendix is located within the hernial sac. It is seen in less than 1% of inguinal hernia.
It should not be confused with an appendix-containing femoral hernia, known as De Garengeot hernia.
Amyloidosis is a heterogeneous disease or even considered a constellation of diseases resulting in a deposition relatively similar proteins. It has many causes and can affect essentially any organ system.
There may be male predilection. Typically affects middle aged individuals a...
Anal atresia (or imperforate anus) refers to a spectrum of anorectal abnormalities ranging from a membranous separation to complete absence of the anus.
The estimated incidence is 1 in 5000 births.
Clinically there is no anal opening. It can be broadly be classified in...
The anal canal is the terminal part of the gastrointestinal tract.
The anal canal measures ~4 cm long and is continuous with the rectum at the anorectal junction, which is the right angle the rectum takes at levator ani (i.e. the pelvic floor).
The anal canal is a muscular tub...
Anal cancer is a relatively uncommon malignancy. It accounts for less than 2% of large bowel malignancies and 1-6% of anorectal tumours (~1.5% of all gastro-intestinal tract malignancies in the Unites States 14).
There may be a slight male predilection where its incidence has bee...
The accepted TNM staging of anal cancer is as follows 1:
Primary tumour (T)
TX: primary tumour cannot be assessed
T0: no evidence of primary tumour
Tis: carcinoma in situ
T1: tumour 2 cm or less in greatest dimension
T2: tumour >2 cm but <5 cm in greatest dimension
T3: tumour >5 ...
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 fibres, up to 5 mm thick
composed of visceral muscle
External anal sphincter
The anatomy curriculum is one of our curriculum articles and aims to be a collection of articles that represent the core anatomy knowledge.
Head and neck anatomy
Abdominal and pelvic anatomy
Lower limb anatomy
Upper limb anato...
An angiosarcoma of the spleen is a rare malignent splenic neoplasm. The term is usually given to describe a primary angiosarcoma of the spleen although angiosarcoma elsewhere can also rarely metastasise to the spleen. Despite its absolute rarity, a splenic angiosarcoma is considered the most co...
Annular pancreas is a morphological anomaly which can cause duodenal obstruction. This condition is important to recognise, because radiologists are usually the first person to diagnose such a condition.
The incidence is probably 1 in 250, however incidence is not accurately repor...
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...
Antibiotic-associated diarrhoea can be broadly divided into two groups:
Clostridium difficile colitis
The former is a life threatening condition, requiring prompt diagnosis and treatment whereas the later is milder and self limiting.
Both result from changes in the bo...
The antral nipple sign refers to redundant pyloric mucosa protruding into the gastric antrum and is seen in pyloric stenosis.
cervix sign of pyloric stenosis
target sign of pyloric stenosis
shoulder sign of pyloric stenosis
An antral pad sign is a feature seen on a spot radiograph of the upper gastrointestinal tract obtained with orally administered contrast material. It refers to the the extrinsic impression or indentation on the postero-inferior aspect of the antrum. The impression is generally arcuate and smooth...
The aortic hiatus is one 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 midline ...
Aorto-enteric fistulation is an uncommon catastrophic cause of gastrointestinal haemorrhage. Aortic fisultas can be primary (associated with an abdominal aortic aneurysm) or secondary (associated with graft repairs).
The annual incidence of primary aorto-enteric fistulas is thoug...
Aphthous ulcers are deep mucosal ulcers of the gastrointestinal mucosa.
infective inflammatory conditions
noninfective inflammatory conditions
idiopathic granulomatous gastritis
Appendiceal carcinoids are rare overall but represent the most common tumour of the appendix. The appendix is also one of the most common (but not the most common) locations for gastrointestinal carcinoid tumours.
Appendiceal carcinoids can present as the obstructive cau...
Appendiceal intussusception happens when appendix segment is pulled into itself or into the cecum. This condition can mimic various chronic and acute abdominal conditions, with an important entity to be recognized, since it could be mistaken as a cecal mass.
Appendiceal mucinous cystadenomas are rare tumours of the appendix. They are considered a benign equivalent of an appendiceal mucinous cystadenocarcinoma.
They may be histologically present in around 0.3% appendiceal resection specimens 3.
A commonly descr...
Appendiceal mucocoeles occur when there is abnormal accumulation of mucus within the appendix. The tenacious and viscous mucus causes obstruction of the appendiceal neck and results in dilatation of the lumen.
The reported prevalence at appendectomy is 0.2-0.3%. They are thought t...
Appendicitis is inflammation of the vermiform appendix. It is a very common condition in general radiology practice and is one of the main causes of abdominal surgery in young patients. CT is the most sensitive modality to detect appendicitis.
Acute appendicitis is typically a dis...
Appendicitis occurs when there is inflammation of the vermiform appendix. It is a very common condition and is a major cause of abdominal surgery in young patients. CT is the most sensitive modality to detect appendicitis although its use should be limited because of the radiation dose required ...
An appendicolith is a calcified deposit within the appendix. They are present in a large number of children with acute appendicitis and may be an incidental finding on an abdominal radiograph or CT. Incidence may be increased among patients with a retrocaecal appendix.
Although the c...
Appendicular abscess is considered the most common complication of acute appendicitis.
Ultrasound is the first investigation advised to evaluate a suspected appendicular pathology. Findings of an appendicular abscess include:
fluid collection (hypoechoic) in ...
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 (vermiform = worm-like) 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, ...
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 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 arc of Buhler (AOB) is a persistent embryologic connection between the coeliac artery and superior mesenteric artery. This arch is is independent of both the gastroduodenal and dorsal pancreatic artery.
It travels vertically, ventral to the abdominal aorta. It is present in 1-4% of indivi...
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...
The arrowhead sign refers to the focal caecal thickening centered on the appendiceal orifice, seen as a secondary sign in acute appendicitis. The contrast material in the cecal 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 a...
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 its own mesentery in approximately 25% of patients and is 15cm in length 1,2.
Ascites is defined as an abnormal amount of intraperitoneal fluid.
Patients with 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 charact...
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...
This is a basic article for medical students and other non-radiologists
NG tube placement is commonly assessed using a chest radiograph although local protocol may dictate that pH assessment of NG aspirate be used in the first instance to confirm position of the NG tube.
There are recognised l...
Atrial-oesophageal fistulas are rare pathological connections between the left atrium and the oesophagus.
The presentation is non-specific. Patients may complain of fever, malaise, dysphagia or present with neurological symptoms 3.
The chief cause of atrial-...
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...