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...
Clostridium difficile colitis, also known as pseudomembranous colitis, is a common cause of antibiotic-associated diarrhoea, and increasingly encountered in sick hospitalised patients. If undiagnosed and untreated, it continues to have high mortality. It may be classified as a form of infectious...
Cobblestoning (having a cobblestone appearance) can occur in a number of hollow organs with mucosa, most commonly the bowel, in the setting of Crohn disease.
Longitudinal and circumferential fissures and ulcers separate islands of mucosa, giving it an appearance reminiscent of cobblestones.
There are several described cockade signs in radiology:
cockade sign (intraosseous lipoma)
cockade sign (aorto-left ventricular tunnel) 1
cockade sign (appendicitis) 2
cockade sign (hypertrophic pyloric stenosis) 3
cockade sign (GI tumours) 4
Coeliac artery, also known as the coeliac axis or coeliac trunk, is a major visceral artery in the abdominal cavity supplying the foregut, arising from the abdominal aorta and commonly giving origin to three major arteries: left gastric artery, splenic artery, and common hepatic artery.
Coeliac artery compression syndrome is also known as coeliac axis syndrome, median arcuate ligament syndrome and Dunbar syndrome. It is characterised by upper abdominal angina secondary to compression of the coeliac trunk by the diaphragmatic crurae.
The median arcuate ligament is th...
Coeliac disease, also known as non-tropical sprue, is a T-cell mediated autoimmune chronic gluten intolerance condition characterised by a loss of villi in the proximal small bowel and gastrointestinal malabsorption (sprue).
It should always be considered as a possible underlying aetiology in c...
Coeliac plexus block under image guidance is an easy and safe percutaneous procedure with good outcomes for pain palliation in patients who have chronic abdominal pain related to the coeliac ganglia.
This usually includes patients with advanced cancers, especially from upper abdominal viscera,...
The coffee-bean sign (also known as the kidney bean sign or bent inner tube sign 4) is a sign on an abdominal plain radiograph of a sigmoid volvulus although some authors have also used the term to refer to closed loop small bowel obstructions. Caecal volvulus may be mistaken with sigmoid volvul...
The collar sign, also called the hourglass sign, is a helpful sign for diagnosis of diaphragmatic rupture on coronal or sagittal CT/ MR images and barium studies. It refers to a waist-like or collar-like appearance of herniated organs at the level of the diaphragm.
dependent viscera s...
A colo-enteric fistula is a type of gastrointestinal fistulation wherein there is abnormal communication between the colon and the small bowel.
It can occur from a number of causes which include:
Crohn disease - considered one of the commonest causes
Colon cut-off sign describes gaseous distension seen in proximal colon associated with narrowing of the splenic flexure in cases of acute pancreatitis. Though originally described in abdominal radiographs, this sign has also been demonstrated in contrast enemas and computed tomography 1.
Colonic anastomotic leaks occur in the early or late postoperative phase, in which the enteric anastomosis fails. This may be a small leak that can be managed conservatively or less commonly complete dehiscence requiring repeat surgery.
In one large surgical series, the incidence ...
Colonic diverticulosis refers to the presence of multiple diverticula. It is quite distinct from diverticulitis which describes inflammation and infection of one or multiple diverticula.
Diverticulosis is very common in westernised countries and is typically found in older individ...
Colonic oesophageal interposition is a now rarely performed upper gastrointestinal tract surgical procedure, in which colon is used to replace the distal oesophagus.
This was performed for long oesophageal strictures or in some cases malignancy.
The haustra of the colon are illustrated on plai...
Colonic pseudo-obstruction (also known as Ogilvie syndrome) is a potentially fatal condition leading to an acute colonic distention without an underlying mechanical obstruction. It is defined as an acute pseudo-obstruction and dilatation of the colon in the absence of any mechanical obstruction....
Colonic strictures can be long (>10 cm) or short.
scirrhous colorectal carcinoma (apple core sign)
post surgical (anastamotic stricture)
scirrhous colorectal carcinoma
inflammatory bowel disease
Colon polyps are mucosal outgrowths of the colon wall. They are of interest to physicians and radiologists because of the accepted progression of adenomatous polyps to colon carcinoma.
adenomatous colon polyps
villous colon polyps
Colorectal carcinoma staging can be performed using two systems. The traditional Dukes staging system has largely been replaced by the TNM system, but is nonetheless often used clinically.
Dukes (Astler-Coller modification)
stage A: confined to mucosa
stage B: through muscularis prop...
This is a basic article for medical students and other non-radiologists
Colorectal cancer, also called colorectal carcinoma (CRC), is the most common cancer of the gastrointestinal tract and the second most frequently diagnosed malignancy in adults. CT and MRI are the modalities most frequently...
Colorectal carcinoma (CRC) is the most common cancer of the gastrointestinal tract and the second most frequently diagnosed malignancy in adults. CT and MRI are the modalities most frequently used for staging. Surgical resection may be curative although five-year survival rate is 40-50%.
Colovaginal fistula is one form of genitourinary fistula. It is also sometimes classed under a type of gastro-intestinal fistula.
It refers to a communication between the colon (typically the rectum or sigmoid colon) with the vagina.
At times, specific terms are used dependent on th...
Colovesical fistulas are communications between the lumen of the colon and that of the bladder, either directly or via an intervening abscess cavity (foyer intermediaire). When the communication is between the rectum and urinary bladder, the term rectovesical fistula is used.
The comb sign refers to the hypervascular appearance of the mesentery in active Crohn disease. Fibrofatty proliferation and perivascular inflammatory infiltration outline the distended intestinal arcades. This forms linear densities on the mesenteric side of the affected segments of small bowel...
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.
The CBD is approximately 8 cm long and usually <6 mm wide in diameter but this can be dependent on a number of factors including age a...
The common hepatic artery (CHA) is a terminal branch of the coeliac artery.
Origin and course
The CHA is a terminal branch of the coeliac artery, it passes to the right in the lesser sac, and enters the lesser omentum to pass slightly upwards towards the porta hepatis. It gives ...
The common hepatic duct is formed by the junction of the right and left hepatic ducts. It joins the cystic duct to form the common bile duct. It is approximately 4 cm long and 4 mm in diameter.
Together with the cystic duct (laterally) and cystic artery (superiorly), they form Calot's triang...
There are many complications that can occur following gastric banding. It is helpful to divide these into early and late post-surgical complications.
Although the exact mode of presentation can vary depending on the underlying complication common modes of presentation tha...
Complications post optical colonoscopy are most commonly assessed by CT if patients present with abdominal symptoms post colonoscopy. Complications include:
bowel perforation (most common)
lower gastrointestinal haemorrh...
Computed tomographic (CT) colonography, also called CTC, virtual colonoscopy (VC) or CT pneumocolon, is a powerful minimally invasive technique for colorectal cancer screening.
screening test for colorectal carcinoma
colon evaluation after incomplete or unsuccessful conventional c...
Computed tomographic (CT) gastrography, also called virtual gastroscopy (VG), is a noninvasive procedure for the detection of gastric abnormalities.
rapid and noninvasive exam
offers information about local tumor invasion, lymph node and distant metastasis in cases of gastric cance...
A cone-shaped caecum refers to a loss of the normal rounded appearance of the caecum, which instead becomes narrow and cone-shaped with the apex pointing towards the base of the appendix. It is encountered in a number of conditions including:
This congenital extrahepatic portosystemic shunt classification was proposed by Morgan and Superina in 1994 1:
type 1: complete diversion of portal blood into the Inferior vena cava with congenital absence of the portal vein
1a: superior mesenteric vein and splenic vein do not join to form a c...
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: localised, peripheral shunt with one or more communications in a single hep...
Congenital portosystemic shunts are rare anatomical abnormalities linked to abnormal embryological venous development. They can be extrahepatic or intrahepatic. In either case, the underlying abnormality is shunting of blood from the portal venous system to the systemic venous system thus avoid...
Congenital tracheo-oesophageal fistula is a congenital pathological communication between the trachea and oesophagus.
Tracheo-oesophageal fistula and oesophageal atresia have a combined incidence of approximately 1 in 3500 live births 1-3,5. There is only a minimal hereditary/ge...
The conjoint tendon forms when the medial fibres of the internal oblique aponeurosis unite with the deeper fibres 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...
The corkscrew sign describes the spiral appearance of the distal duodenum and proximal jejunum seen in midgut volvulus. It has been identified as a diagnostic indicator of midgut volvulus 1.
In patients with malrotation and volvulus, the distal duodenum and proximal jejunum do not cross the mid...
Cornual ectopic pregnancies are rare and represent a gestational sac within the cornua of a bicornuate or septate uterus.
Although sometimes interchangeably used with interstitial pregnancy, cornual pregnancy specifically refers to the presence of a gestational sac within a rudime...
Corrosive oesophagitis usually occurs from accidental or suicidal ingestion of caustic substances (e.g. lye, household cleaners, bleaches, washing soda), and is harmful to the oesophagus due to their alkali medium. The stomach is not affected as the gastric acid can neutralize these substances, ...
Cowden syndrome, also known as multiple hamartoma syndrome, is characterised by multiple hamartomas throughout the body and increased risk of several cancers.
Type 2 segmental Cowden syndrome is the association of Cowden syndrome with a Cowden naevus, when it is considered a type o...
The crescent in a doughnut sign refers to the transverse ultrasound appearance of intestinal intussusception, and is a variation of the target sign (which is also known as the doughnut sign)
The doughnut is formed by concentric alternating echogenic and hypoechogenic bands. The echogenic bands ...
Cricopharyngeal bar refers to the radiographic appearance of a prominent cricopharyngeus muscle contour on barium swallow.
The terms cricopharnygeal bar and cricopharyngeal muscle spasm/achalasia are often used synonymously but this is incorrect because studies have demonstrated th...
Cricopharyngeal muscle spasm is also known as cricopharyngeal achalasia, although some authors distinguish between these entities, and may present as a cause of dysphagia.
There is confusing use of the terms cricopharyngeal muscle spasm, cricopharyngeal achalasia and cricopharyngea...
Crohn disease, also known as regional enteritis, is an idiopathic inflammatory bowel disease characterised by widespread discontinuous gastrointestinal tract inflammation. The terminal ileum and proximal colon are most often affected. Extraintestinal disease is common.
Due to the overlap in clinical presentation of Crohn disease (CD) and ulcerative colitis (UC), imaging often has a role to play in distinguishing the two. Distinguishing features include:
CD: small bowel 70-80%, only 15-20% have only colonic involvement
UC: rectal involvement 9...
Cronkhite–Canada syndrome is a type of non-hereditary hamartomatous polyposis syndrome characterised by rash, alopecia, and watery diarrhea.
There is a recognised male predilection. Patients typically are middle age, in their 60th 1.
Patients typically pres...
This is a basic article for medical students and other non-radiologists
CT abdomen is an increasingly common investigation that is used to help make diagnoses of a broad range of pathologies. A CT abdomen in its simplest form is a CT from diaphragm to symphysis pubis performed 60 seconds after ...
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:
CT colonography reporting and data system is a method devised to standardise CT colonography reporting.
It primarily classifies abnormalities into colonic (C) and extra-colonic (E).
C0: inadequate study
C1: normal colon/benign lesion: routine screening ...
Computed tomographic (CT) enteroclysis refers to a hybrid technique that combines the methods of fluoroscopic intubation-infusion small bowel examinations with that of abdominal CT 1.
CT enteroclysis is complementary to capsule endoscopy in the elective investigation of small-bowel...
Computed tomographic (CT) enterography is a non-invasive technique for diagnosis of small bowel disorders.
evaluates the entire thickness of the bowel wall
offers information about the surrounding mesentery, the mesenteric vasculature and the perienteric fat
useful in the assessm...
CT hypotension complex refers to the predominantly abdominal imaging features that occur in the context of profound hypotension. Multiple abdominal organs can display atypical appearances not related to the initial trauma but reflect alterations in perfusion secondary to hypovolemia which affect...
CT peritoneography is an examination used to assess difficulties with peritoneal dialysis.
Recurrent peritonitis with difficulty with fluid exchange abdominal wall or genital soft-tissue oedema, localized bulging of the abdomen, and poor ultrafiltration.
CT polytrauma/multitrauma, also called trauma CT, whole body CT (WBCT) or panscan, is an increasingly used investigation in patients with multiple injuries sustained after significant trauma.
Clinical assessment and mechanism of injury may underestimate injury severity by 30% 8. There is some e...
The CT severity index (CTSI) is based on findings from a CT scan with intravenous contrast to assess the severity of acute pancreatitis. The severity of computed tomography findings have been found to correlate well with clinical indices of severity.
The CTSI sums two scores:
The cupola sign is seen on a supine chest/abdominal radiograph in the presence of pneumoperitoneum.
It refers to non-dependent gas that rises within the abdominal cavity of the supine patient to accumulate underneath the central tendon of the diaphragm in the midline. It is seen as lucency ove...
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. The cystic duct is approximately 2-3 cm long and 2-3 mm in ...
Abdominal manifestations in cystic fibrosis are common, varied and nearly all organ systems can be affected. Only 39% of patients with cystic fibrosis (CF) have pulmonary symptoms as their sole complaint 1. 7% of CF patients do not present until adulthood.
For a general discussion of cystic fib...
The differential for cystic lesions of the pancreas includes:
intraductal papillary mucinous neoplasm (IPMN)
serous cystadenoma uncommonly uni/macrolocular
simple pancreatic cyst
pancreatic cysts occur in association with
von Hippel Lindau syndrome
A mnemonic for causes of cystic lesions in the spleen is:
Cystic or necrotic appearing lymph nodes can be caused by a number of infectious, inflammatory or malignant conditions:
squamous cell carcinoma metastases
plasmacytoid T-cell leukemia
acute myeloid leukemia
herpes simplex lymphadenit...
A cystic retroperitoneal lesion can carry a relatively broad differenital which includes:
retroperitoneal cystic lymphangioma
retroperitoneal mucinous cystadenoma
retroperitoneal cystic teratoma
retroperitoenal cystic mesothelioma
pseudomyxoma retroperitonei with cystic change
De Garengeot hernias are femoral hernias that contain the appendix. It is a rare phenomenon, with only 1% of all femoral hernias containing the appendix (and usually found incidentally at surgery), and only 0.08-0.13% containing an incarcerated acute appendicitis (sometimes detected on pre-opera...
Degloving bowel injuries are a rare type of bowel and mesenteric injury only being described a handful of times in the literature 1-5. In these injuries the bowel is stripped of its mesentery and muscle, leaving a "mucosal tube" 2,3. Perforation may or may not be present.
Degloving injuries can refer to a number of conditions:
degloving soft tissue injury
Morel-Lavallee lesion (closed degloving soft tissue injury)
intramuscular degloving injury
degloving bowel injury
Dehiscence is a general term referring to 'splitting open' and is used in a variety of contexts in medicine generally and radiology more specifically.
The two most common usages are:
splitting open of a wound (e.g. sternal dehiscence)
loss of bone separating one structure from another (e.g. ...
The dependent viscera sign is one of the signs of diaphragmatic rupture on axial CT or MR images, where herniated viscera lie against the posterior thoracic wall in a dependent position, as they are no longer supported by the diaphragm.
collar sign (or hourglass sign)
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 length and is secondarily retroperitoneal. It descends down and is attached to the left posterior abdomin...
Desmoplastic small round cell tumours are a rare and highly aggressive primary peritoneal malignancy.
They are usually seen in young adolescents and has male predominance with a mean survival of 2-3 years.
It usually presents with a palpable abdominal mass ...
The diaphragm is the dome-shaped muscle that separates the thoracic cavity from the abdominal cavity, enclosing the inferior thoracic aperture.
The muscular fibres of the diaphragm originate around the circumference of the inferior thorax and converge to a common insertion point ...
Diaphragmatic rupture often results from blunt abdominal trauma. The mechanism of injury is typically a motor-vehicle collision.
Given that the most common mechanism is motor vehicle collisions, it is perhaps unsurprising that young men are most frequently affected. The estimated ...
Dieulafoy lesions are uncommon but important causes of acute gastrointestinal bleeding. A Dieulafoy lesion is characterised by a dilated tortuous submucosal artery that erodes overlying gastrointestinal mucosa.
contributes to ~1.5% of all acute gastrointestinal bleeding 1
Diffuse colonic nodularity on barium enema or CT colonography has a range of possible etiologies:
lymphoid hyperplasia (tend to be small and discrete)
lymphoma (tend to be larger nodules and confluent)
urticaria (closely spaced polygonal lesions, history is often helpful)
Diffuse/distal oesophageal spasm (DOS) is a motility disorder of the oesophagus. On barium swallow, DOS may appear as a corkscrew or rosary bead oesophagus, but this is uncommon. Manometry is the gold-standard diagnostic test.
Diffuse oesophageal spasm differs from hypercontracting oesophagus ...
Diffuse/disseminated peritoneal leiomyomatosis (DPL), also known as leiomyomatosis peritonealis disseminata, is an exceedingly rare benign disorder characterised by multiple vascular leiomyomas growing along the submesothelial tissues of the abdominopelvic peritoneum.
DPL is usual...
Diffuse small bowel disease may be caused by a number of conditions may be generalised multisystem disorders or conditions that effect the bowel in a global fashion:
Discrete colonic ulcerations are nonspecific findings, and can be due to:
Distal intestinal obstruction syndrome (DIOS) is one the of many abdominal manifestations of cystic fibrosis. In older children or young adults with cystic fibrosis, the distal small bowel may become obstructed with a mucofaeculent material in the distal ileum and right colon.
Diverticular disease covers a range of pathologies and may account for a wide variety of presentations.
Outpouchings of bowel result in blind-ended diverticula in communication with the lumen of the bowel. They most commonly occur within the sigmoid colon, although they may be presen...
Diverticulitis is one of the presentations of diverticular disease and is most often a complication of colonic diverticulosis. Differentiating one from the other is critical since uncomplicated diverticulosis is mostly asymptomatic and acute diverticulitis is a potentially life-threatening illne...
This is a basic article for medical students and other non-radiologists
Diverticulitis is one of the presentations of diverticular disease and is most often a complication of colonic diverticulosis. Differentiating one from the other is critical since uncomplicated diverticulosis is mostly asym...
Diverticula are out-pouchings of a hollow viscus and can be either true or false.
contains all layers of the wall of the parent organ (typically mucosa, muscular layer and serosa)
e.g. Meckel diverticulum
does not contain all layers (typically mu...
The doge cap sign is a radiographic sign of pneumoperitoneum. It presents as a triangular-shaped gas lucency in the right upper quadrant on abdominal radiographs due to air in the Morison pouch, which resembles the medieval caps worn by Italian doges.
Agenesis of the dorsal pancreas is an extremely rare congenital pancreatic anomaly.
While complete agenesis of the dorsal pancreas is extremely rare, partial agenesis of the dorsal pancreas is thought to be most common than ventral pancreatic agenesis 4.
While many pati...
Double barrel sign is an imaging appearance of two lumens adjacent to each other.
It can be seen in:
dilated bile duct adjacent to portal vein
double barrel aorta: aortic dissection
double barrel oesophagus: oesophageal dissection
The double bubble sign is seen in infants and represents dilatation of the proximal duodenum and stomach. It is seen in both radiographs and ultrasound, and can be identified antenatally 2.
Causes include 1,2:
The double contrast barium enema is rapidly being replaced by CT colonography, but remains in some centres for:
the detection of polyps and colorectal cancer
follow up screening for postoperative colorectal cancer
evaluation of diverticular disease
investigation of non-sp...
Double contrast barium enema technique is a method of imaging the colon with fluoroscopy. "Double contrast" refers to imaging with the positive contrast of barium sulfate contrast (rarely water-soluble iodinated contrast) as well as with the negative contrast of gas (CO2 preferable). An exam wit...
The double duct sign refers to the presence of simultaneous dilatation of the common bile and pancreatic ducts. Being an anatomical sign it can be seen on all modalities that can visualise the region, including: MRI, CT, ultrasound and endoscopic retrograde cholangiopancreatography (ERCP).
The double track sign is a radiological sign described in pyloric stenosis on various imaging modalities.
Double streaks of barium passing through the narrow pylorus 1.
On fluid aided real-time examination, the pyloric fluid is compressed into smaller tracks as it is...
The double wall sign is another name for the Rigler sign. It is a sign of pneumoperitoneum with gas outlining both sides of the bowel wall. It is seen when large amounts of free gas, >1000 mL, are present.
It should be distinguished from the false double wall sign which refers to two dilated lo...
Down syndrome (or trisomy 21) is the most common trisomy and also the commonest chromosomal disorder. It is a major cause of intellectual disability, and also has numerous multi-system manifestations.
According to the world health organisation (WHO), the approximate worldwide inci...