In the gallbladder, the Mercedes-Benz sign describes a star-shaped pattern of gas-fissuring within gallstones initially described on an abdominal radiograph 2.
Fissures, usually fluid-filled, are present in close to 50% of gallstones. Less than half of these fissured gallstones contain some amo...
Mesenteric adenitis is a self-limiting inflammatory process that affects the mesenteric lymph nodes in the right lower quadrant, and is clinically often mistaken for acute appendicitis.
Mesenteric adenitis is most common in children and adolescents although it may occasionally aff...
Mesenteric cysts are a very rare cause of abdominal pain, and have a wide range of underlying causes.
Mesenteric cysts are rare, with a reported incidence of 0.5-1 per 100,000 admissions 3.
Patients usually present with abdominal pain and/or mass, althoug...
Mesenteric desmoid tumours are a subtype of desmoid tumours
Desmoids are cytologically bland tumours that appear as infiltrative, well-demarcated tumours that are derived from musculo-aponeurotic structures throughout the body.
in the mesentry, the masses may occur ...
A mesentery is a double layer of peritoneum that encloses the intestines and attaches them to the posterior abdominal wall. The term was originally only used to refer to the double layer of peritoneum that suspends the jejunum and ileum, but its meaning has been widened.
The mesoappendix is a fold of peritoneum around the vermiform appendix and one of the four mesenteries in the abdominal cavity.
It is attached to the lower end of the small bowel mesentery, close to the ileocaecal junction. It usually extends to the tip of the appendix and sometimes suspends th...
Metaplasia is a general pathology term that refers to process when one cell type is replaced by another. It usually occurs in the context of changed cellular environment to which the new cell type is better adapted 1. Examples include 2-5:
Barrett oesophagus: normal squamous epithelium replaced...
MIBG scan is a scintigraphic study that uses metaiodobenzylguanidine labeled to Iodine-123 or Iodine-131. It is indicated in the investigation of phaeochromocytoma.
MIBG is positive in:
olfactory neuroblastoma 1
carcinoid tumour 4
The middle colic artery is a branch of the superior mesenteric artery (SMA). It passes in the layers of the transverse mesocolon to the transverse colon.
The middle colic artery divides into right and left branches. The right branch supplies the right portion of the transverse colon and anastom...
The middle rectal artery, also known as the middle haemorrhoidal artery, is a branch from the anterior division of the internal iliac artery supplying the rectum.
origin: anterior division of the internal iliac artery
supply: inferior rectum, seminal vesicles, prosta...
Midgut volvulus is a complication of malrotated bowel and results in a proximal bowel obstruction and ischaemia.
A midgut volvulus of malrotated bowel can potentially occur at any age but in approximately 75% of cases is within a month of birth 4,6, most within the first week 3, a...
Misty mesentery is a term used to describe the CT appearance of mesenteric fat with increased attenuation. Just as with fat stranding elsewhere, a number of processes can lead to the appearance including infiltration by inflammatory cells, oedema, lymphatic accumulation, haemorrhage, tumour infi...
Mobile caecum is an anatomical variant and is often defined as a failure of the caecum, terminal ileum, and right colon, along with the mesentery, to fuse to the posterior parietal peritoneal wall. This results in increased mobility of the caecum.
It has been estimated to occur in...
The modified CT severity index is an extension of the original CT severity index (CTSI) was developed by Balthazar and colleagues in 1994 for distinguishing mild, moderate and severe forms of acute pancreatitis.
The original CT severity index has been followed internationally and has been very ...
Morgagni hernias are one of the congenital diaphragmatic hernias (CDH), and is characterised by herniation through the foramen of Morgagni. When compared to Bochdalek hernias, Morgagni hernias are:
more often right-sided (~90%)
rare (~2% of CDH)
at low risk of prolapse
The moulage sign is related to sprue, in particular coeliac disease. It occurs where there is a dilated jejunal loop with complete loss of jejunal folds 1. It is said to appear like a tube into which wax has been poured.
History and etymology
Moulage (French: casting/moulding) is the art of ap...
MR defecography is a dynamic study for evaluation of the pelvic floor and pelvic organ prolapse.
There are four phases of evaluation:
Method of evaluation
Many variations in the techniques described below exist.
MR enteroclysis is a technique for evaluation of number of small bowel diseases (especially Crohn disease) using MRI.
A general technique is outlined below
placement of a nasoduodenal tube under fluoroscopic guidance
the small-bowel is distended with 1-3 L of methylcellulose (0.5%)...
MR enterography is a new non-invasive technique for diagnosis of small bowel disorders.
The most common indication is to evaluate patients with Crohn disease (CD).
Actual procedure will vary depending on institutional protocol/guidelines but below is a typical descripti...
Mucinous adenocarcinomas of the appendix are on the malignant end of the spectrum of the mucinous neoplasms that affect the caecal appendix.
For the mucinous carcinomas involving the remainder of the colon, please refer to the article on mucinous carcinoma of the colon.
Mucinous carcinoma of the colon is a distinct form of colorectal cancer found in 10-15% of patients with colorectal cancer. It differs from the conventional adenocarcinoma in terms of clinical and histopathological characteristics.
For the caecal appendix, please refer to the article on mucinou...
Mucinous cystadenocarcinomas of the pancreas are a type of pancreatic mucinous tumour. It is considered the more malignant counterpart of a mucinous cystadenoma of the pancreas.
Like the more benign mucinous cystadenomas, these are found almost exclusively in females 4.
Mucinous cystadenomas (MCN) of the pancreas are a type of mucinous cystic neoplasm of the pancreas.
Previously believed to occur exclusively in middle age females 5, it has occasionally been described in males 6-7.
It is a large uni/multilocular cystic pancreatic neopl...
Mucinous cystic neoplasms of the pancreas are the most common cystic neoplasm of the pancreas and include:
mucinous cystadenoma of pancreas
mucinous cystadenocarcinoma of pancreas
intraductal papillary neoplasms (IPMN) of the pancreas: sometimes classified separately
Mucinous neoplasms of the appendix are epithelial tumours of the appendix that produce mucin. According to a panel of specialists consensus published in 2016, a new nomenclature and classification for the appendiceal mucinous neoplasms based on their histologic type and biologic behaviour has be...
Muir-Torre syndrome is a rare variant of hereditary nonpolyposis colorectal cancer (HNPCC), characterised by sebaceous neoplasms (e.g adenoma, epithelioma or carcinoma) and keratoacanthocytomas as well as at least one internal malignancy:
gastrointestinal malignancies (most common of internal ...
Multiple endocrine neoplasia (MEN) type I is also known as Wermer syndrome.
Primary hyperparathyroidism is one of the commonest presentations.
The abnormality is related to a tumour suppressor gene located in chromosome 11q13. MEN type I is an autosomal domina...
Mushroom cap sign is one of the important signs of deep rectosigmoid endometriosis seen on T2 weighted MRI sequence. It indicates the submucosal involvement in rectosigmoid region.
Hypertrophic muscularis propria appears as heterogeneous low signal intensity surrou...
The mushroom sign (also called umbrella sign) is a radiological sign described in pyloric stenosis on barium examination.
This sign refers to the impression made by the hypertrophic pylorus on the duodenal cap.
cervix sign of pyloric stenosis
target sign of pyloric st...
Mycosis fungoides (MF), also known as cutaneous T-cell lymphoma, is a type of malignant T-cell lymphoma that primarily involves the skin.
In the United States, it is more common in males and African Americans. In Europe, it accounts for ~6% of all non-Hodgkin lymphomas. It is rar...
Myochosis coli is an uncommonly used term to denote the shortening and thickening of the colon seen in diverticulosis.
This is due to shortening of the taenia coli and thickening of the circular muscular layer 1.
Nasogastric (NG) tube position on chest x-ray should be assessed following initial placement and on subsequent radiographs.
This is a summary article; we do not have a more in-depth reference article.
x-rays are only performed when the position ...
Assessment of nasogastric (NG) tube positioning is a key competency of all doctors as unidentified malpositioning may have dire consequences, including death.
The ideal position should be in the sub-diaphragmatic position in the stomach - identified on a plain chest radiograph as overlying the ...
Necrotising enterocolitis (NEC) is the most common gastrointestinal condition in premature neonates, and continues to have significant mortality and morbidity.
NEC usually develops 2-3 days following birth, with 90% developing within the first 10 days of life 4. The incidence is i...
Necrotising enterocolitis (NEC) can be staged into three groups, helping to guide appropriate treatment. In general, stage I and II are managed medically whereas stage III is managed surgically.
lethargy, temperature instability, apnoea, bradycardia
emesis, abdominal d...
Necrotising pancreatitis (NP) represents the severe form of pancreatitis. It is considered a subtype of acute pancreatitis as necrosis usually tends to occurs early, within the first 24-48 hours, but can also rarely occur with subacute forms.
A key feature is a significant amount of pancreatic ...
Neonatal appendicitis is rare, presumably in part due to the short funnel shape to the appendix at that age. Symptoms are non-specific and may mimic necrotising enterocolitis.
The causes of neonatal pneumoperitoneum are different from adult pneumoperitoneum and include:
perforated hollow viscus
necrotising enterocolitis (NEC): most common
meconium ileus in cystic fibrosis
intestinal atresia or web
peptic ulcer disease
There are a number of neoplasms that can involve the appendix, some of which are peculiar to this site.
Tumours involving the appendix have been found in only about 1% of all appendectomy 9. Epithelial neoplasms and neuroendocrine tumours represent the gross majority of the tumour...
Neuhauser sign refers to a soap bubble appearance seen in the distal ileum in cases of meconium ileus, related to the air mixed with meconium. It may be seen with barium enema if contrast passes beyond the ileocaecal valve or with small-bowel follow-through.
Although classically described with ...
Niacin (vitamin B3) deficiency, also known as Pellagra, is a multisystemic disease with manifestations from the skin, gastrointestinal tract and central nervous system.
It use to be widespread until the early twenty century, but after fortification of flour with niacin it is prac...
Nodular filling defects due to mucosal lesions in the duodenum are due to a number of processes. For a differential list which includes non-mucosal lesions see duodenal filling defects.
The differential diagnosis for mucosal lesions includes:
heterotopic gastric mucosa
Non-neoplastic solid lesions of the pancreas (NNSLP) are conditions which may mimic pancreatic neoplasms on imaging. They include:
intrapancreatic accessory spleen
congenital anomalies, such as prominent pancreatic lobulations and bifid pancr...
Non-specific oesophageal motility disorder (NSMD) is one of the oesophageal dysmotility disorders. It is used to described patients with oesophageal dysmotility that do not meet diagnostic criteria for other oesophageal motility disorders.
Patients may be asymptomatic or...
example 1: abdominal film
example 2: erect and supine
example 3, example 4: paediatric
example 5: young adult
example 6: young adult male
example 1, example 2, example 3: barium swallow
example 1: upper GI series
example 1: barium follow through
Mesenteric lymph nodes had, during the era of single thick slice CT been only really appreciated when enlarged. With the advent of multidetector volume acquisition CT (and especially coronal reformats) they are commonly seen in normal individual and thus have raised the obvious question of what ...
There are a number of normal oesophageal contours or impressions that are encountered when performing a barium swallow. It is important to be able to differentiate normal contours and their variants, as well as contours that may indicate disease. Below is a list of anatomical structures that may...
The northern exposure sign has been described as a high specificity sign in sigmoid volvulus. On a supine abdominal radiograph, the apex of the sigmoid volvulus is seen above (cranial to) the transverse colon.
Obstructive jaundice represents a set of conditions that cause jaundice by obstructing the flow of bile into the duodenum anywhere along the intrahepatic or extrahepatic biliary tree.
This is a summary article; read more in our article on jaundice.
Obturator hernias are a rare type of abdominal hernia, and can be clinically very difficult to diagnose.
Typically obturator hernias occur in elderly women 3-4 or patients with chronically raised intra-abdominal pressure (e.g. ascites, COPD, chronic cough)4. It has been suggested...
An octreoscan is a scinitigraphic study that uses 111In labelled octreotide which is a somatostatin analog. It is particularly useful for assessment of neuroendocrine tumours.
glomus jugulare tumour
An oesophageal atresia refers to an absence in contiguity of the oesophagus due to an inappropriate division of the primitive foregut into the trachea and oesophagus. This is the most common congenital anomaly of the oesophagus.
It is thought to occur in ~1:3000-4500 live births ...
Oesophageal atresia is closely related to tracheo-oesophageal fistula and can be divided into1:
type A: isolated oesophageal atresia (8%)
type B: proximal fistula with distal atresia (1%)
type C: proximal atresia with distal fistula (85%)
type D: double fistula with intervening atresia (1%)
Oesophageal bronchus refers to the rare occurrence where a bronchus arises directly from the oesophagus.
It is more common in females with a M:F of 1:2 2.
Oesophageal bronchi may be the main bronchus, which gives rise to oesophageal lung, or may be a lobar bronchu...
Oesophageal cancer staging can depend slightly on whether the tumour is squamous cell or adenocarcinoma subtype. Due to the lack of a serosal layer, oesophageal cancer often tends to have mediastinal spread at the time of diagnosis.
Tx: primary tumour cannot be...
Oesophageal cancer is a relatively uncommon tumour that occurs within the oesophagus of affected individuals. Patients present with symptoms of increasing dysphagia that progress from solid foods to liquids.
This is a summary article; read more in our article on oesophageal c...
Oesophageal carcinoma is relatively uncommon. It tends to present with increasing dysphagia, initially to solids and progressing to liquids as the tumour increases in size, obstructing the lumen of the oesophagus.
Oesophageal cancer is responsible for <1% of all cancers and 4-10% ...
Oesophageal diverticula are sac or pouch projections arising from the oesophagus.
They can occur in all ages but more frequent in adults and elderly people.
Oesophageal diverticula are either:
true diverticula: include all oesophageal layers
false diverticula: contai...
Duplication of the oesophagus has a range of macroscopic appearances, ranging from complete (which is very rare) to partial cystic duplication (oesophageal duplication cyst). It is the second most common gastrointestinal tract duplication after that of the ileum.
A complete duplic...
Oesophageal duplication cysts are a type of congenital foregut duplication cyst.
Less common compared to other foregut duplication cysts. There may be an increased male predilection 5.
Patients are generally asymptomatic but may complain of dysphagia due to...
Oesophageal dysmotility refers to the pathological disruption of the normal sequential and coordinated muscle motion of the oesophagus to transport food from the oropharynx to the stomach. It is an umbrella term used to refer to the common pathophysiological endpoint of dysmotility that can be c...
Oesophageal fibrovascular polyps are benign intraluminal submucosal pedunculated tumours that can grow significantly and cause dysphagia symptoms. They usually occur in the upper third of the oesophagus, at the level of the upper oesophageal sphincter.
They were previously denomin...
Oesophageal food impaction (or steakhouse syndrome) refers to a food bolus acutely obstructing the oesophagus.
The main symptom is usually of acute dysphagia.
Depending on the composition of the ingested content, the bolus may be ...
The oesophageal hiatus is the opening in the diaphragm through which the oesophagus passes from the thoracic to abdominal cavity. It is one of three apertures in the diaphragm and is located in the right crus.
It is situated in the muscular part of the diaphragm at the level of T10 and is ellip...
Oesophageal leiomyoma is a benign smooth-muscle neoplasm of the oesophagus. It is the most common benign tumour of the oesophagus.
It is most frequently presents in young and middle age groups (20-50 years). The overall incidence is around 8-43 per 10,000 autopsy series 4.
Oesophageal leiomyomatosis is rare benign condition.
It usually presents at childhood. There is a recognised increased female predilection.
It is considered a hamartomatous condition and is associated with abnormal diffuse proliferation of smooth muscle fibres in dista...
Oesophageal leiomyosarcoma is a rare malignant tumour of the oesophagus of smooth muscle origin.
The first case of oesophageal leiomyosarcoma was described in 1905. Since then, there have been over 164 cases described in the literature.
Fluoroscopy - Bari...
A mnemonic to remember the causes of an oesophageal mass is:
CALL the MVP
Oesophageal myotomy (or Heller myotomy) is a procedure that can be performed to treat a lower oesophageal sphincter (LES) that fails to relax (e.g. achalasia). The procedure involves a longitudinal incision of the distal oesophageal musculature to break the sphincter tone.
A fundoplication wrap...
Oesophageal perforation is a rare but serious medical emergency with a very high mortality rate, especially if the diagnosis is delayed.
Most patients are in their 60s with a slight male predominance 5.
If a perforation is not detected during the procedure...
Oesophageal intramural pseudodiverticulosis is an uncommon condition in which there are numerous small outpouchings within the oesophageal wall.
It is a rare condition, found in <1% of oesophagrams. It may occur at any age, but is more common between ages 50 and 70. There is a sl...
Oesophageal squamous papilloma is an uncommon finding on oesophagography (barium swallow). It is a benign lesion, but it is difficult to differentiate it from osophageal carcinoma on oesophagography and the diagnosis is usually made with endoscopic biopsy.
Oesophageal stents are a treatment option in patients with oesophageal strictures. It is most commonly used for symptomatic relief in those with dysphagia secondary to malignancy. The stent is typically covered in nature and inserted endoscopically or fluoroscopically. The distal oesophagus is t...
Oesophageal strictures refer to any persistent intrinsic narrowing of the oesophagus.
The most common causes are fibrosis induced by inflammatory and neoplastic processes. Because radiographic findings are not reliable in differentiating benign from malignant strictures, ...
Oesophageal webs refer to an oesophageal constriction caused by a thin mucosal membrane projecting into the lumen.
Oesophageal webs tend to affect middle-aged females.
Patients are usually asymptomatic and the finding may be incidental and unimportant. Howe...
Oesophagectomy (or esophagectomy) is a surgical procedure that involves excision of the majority of the oesophagus and part of the proximal stomach, usually as a treatment for oesophageal carcinoma or carcinoma of the gastric cardia, although benign conditions (e.g. stricture) can be treated wit...
The oesophagus is a muscular tube that conveys food and fluids from the pharynx to the stomach.
The oesophagus is 23-37 cm long with a diameter of 1-2 cm and is divided into three parts:
cervical: continuous with the hypopharynx, commences at the lower border of cricoid cartilag...
The omega sign can refer to a number of different anatomical structures or signs:
omega sign (epiglottitis)
omega sign (hand bump on the precentral gyrus)
Omental cake refers to infiltration of the omental fat by material of soft-tissue density. The appearances refer to the contiguous omental mass simulating the top of a cake. Masses on the peritoneal surfaces and malignant ascites may also be present.
The most common cause is metasta...
Omental infarction is a rare cause of acute abdomen resulting from vascular compromise of the greater omentum. This condition has a non-specific clinical presentation and is usually managed conservatively. The term along with epiploic appendagitis is grouped under the broader umbrella term intra...
Omental torsion is defined as a twist of the omentum along its long axis with consequent impeding of its vascularity that may mimic acute abdomen 1.
Omental torsion is a rare cause of acute abdominal pain that occurs in the third to fifth decade of life with slight male predomina...
Omphalomesenteric fistula occurs as aresult of failure of obliteration of the omphalomeseneric duct. It is one of the congenital fistulas of gastrointestinal tract .
Treatment of choice is often a partial trans umbilical resection with umbilical restitution.
Oral cholecystography was a procedure used to image the gallbladder, now largely superseded by ultrasound and MRCP. It was first described by Graham et. al in 1925, using sodium tetraiodophenolphthalein.
Although rarely performed now, more modern techniques used other cholegraphic agents such...
A useful mnemonic to help remember the order of structures in the porta hepatis from anterior to posterior is:
D: ducts (right and left hepatic duct branches)
A: arteries (right and left hepatic artery branches)
V: vein (portal vein)
E: epiploic foramen (of Winslow)
The pancreas is a retroperitoneal organ that has both endocrine and exocrine functions: it is involved in the production of hormones (insulin, glucagon and somatostatin), and also involved in digestion by its production and secretion of pancreatic juice.
The pancreas can be divid...
A pancreas transplant is a procedure performed in some medical centers in which a donor pancreas is transplanted to a recipient. The donor pancreas is typically cadaveric, but may rarely be a segment from a living donor 1. The transplant is meant to establish normoglycemia in patients with dia...
Pancreatic atrophy is non-specific and is common in elderly patients, although in younger patients it can be a hallmark of pathology. Most commonly it is associated with aging, obesity and end-stage chronic pancreatitis.
It occurs principally with fatty replacement of the pancreas (pancreatic ...
Pancreatic calcifications can arise form many aetiologies.
Punctate intraductal calcifications
acute alcoholic pancreatitis (20-40%)
intraductal, numerous, small, irregular
preponderant cause of diffuse pancreatic intraductal calcification
idiopathic: no underlying ca...
Both endocrine and exocrine tumours of the pancreas are now staged by a single pancreatic staging system.
Staging of pancreatic ductal adenocarcinoma is with the TNM system, and as a majority of tumours are not-resectable, this is mostly achieved with imaging (typically CT scan) although laparo...
The pancreatic ductal embryology is moderately complicated, leading to a number of anatomical variants of the pancreatic ducts, many of which are clinically significant.
The normal arrangement is for the entire pancreas to be drained via a single duct, to the ampulla of Vater through the sphinc...
Pancreatic intraductal tubulopapillary neoplasms (ITPNs) are rare variants of intraductal papillary neoplasms. Unlike an IPMN, an ITPN does not produce mucin.
Incidence/prevalence is unclear. Small series show an even male:female distribution and an average age of presentation of ...
Pancreatic intraepithelial neoplasia (PanIN) is a precursor lesion to pancreatic ductal adenocarcinoma, but the frequency at which this transition occurs is unknown.
Increasing incidence with age 1. Risk factors:
pancreatic lipomatosis 3
More commonly locat...
Pancreatic lipomas are uncommon mesenchymal tumors of the pancreas.
Rarely symptomatic, they are most often detected incidentally on cross-sectional imaging for another purpose. If they do cause symptoms, it will typically be those related to regional mass effect from the...