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. It may result in proximal bowel obstruction with resultant ischaemia if prompt treatment is not instigated.
A midgut volvulus of malrotated bowel can potentially occur at any age but in approximately 75% of cases occur within ...
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 defaecography 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 an invasive technique for MRI evaluation of the small bowel mostly used in Crohn disease.
A general technique includes:
placement of a nasoduodenal tube under fluoroscopic guidance
small bowel distension with 1-3 L of methylcellulose (0.5%) and water solution or ...
MR enterography is a non-invasive technique for diagnosis of small bowel disorders.
MR enterography is most commonly used to evaluate patients with Crohn disease where it is used for assessment of the primary disease and any complications. Other indications include coeliac disease,...
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 mucinous 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...
Mucous fistulas are a connection between bypassed colon and the skin surface. It is a type of colostomy, but instead of letting ingested contents pass out of the body, a mucous fistula allows release of colonic secretions, mucus, and gas so that they do not build up over time.
The mucous fist...
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 type I (MEN1), also known as Wermer syndrome, is an autosomal dominant genetic disease that results in proliferative lesions in multiple endocrine organs, particularly the pituitary gland, islet cells of the pancreas and parathyroid glands.
There are other multiple...
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...
Mycotic aneurysms are aneurysms arising from infection of the arterial wall, usually bacterial. It is a complication of the haematogenous spread of bacterial infection, classically from the heart.
The epidemiology of mycotic aneurysms mirrors that of identifiable risk factors:
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 taeniae coli and thickening of the circular muscular layer 1.
History and etymology
Myochosis coli is from the Ancient Greek for "heaped-up ...
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 ...
This is a basic article for medical students and other non-radiologists
Nasogastric (NG) tube position on chest x-ray should be assessed following initial placement and on subsequent radiographs.
This is a summary article; we have a more in-depth reference article NGT.
Necrotising enterocolitis (NEC) is the most common gastrointestinal condition in premature neonates. It is characterised by inflammation, ischaemia, and permeability of the neonatal bowel wall to bacteria. It is potentially life-threatening with significant associated morbidity 1.
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 a severe form of acute pancreatitis. It is considered a subtype of acute pancreatitis as necrosis usually tends to occur early, within the first 24-48 hours, but can also rarely occur with subacute forms.
A key feature is a significant amount of pancreat...
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 vermiform appendix, some of which are peculiar to this site.
Tumours involving the appendix have been found in only about 1% of all appendectomy specimens 9. Epithelial neoplasms and neuroendocrine tumours represent the vast maj...
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 multisystem disease which involves 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 was practically era...
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 are conditions which may mimic pancreatic neoplasms on imaging. They include:
intrapancreatic accessory spleen
peripancreatic lymph node
Non-specific oesophageal motility disorder (NSMD) is one of the oesophageal dysmotility disorders. It is used to describe patients with oesophageal dysmotility that do not meet diagnostic criteria for other oesophageal motility disorders.
Patients may be asymptomatic or ...
This article lists examples of normal imaging of the gastrointestinal tract and surrounding structures, divided by modality.
example 1: abdominal film
example 2: erect and supine
example 3, example 4: paediatric
example 5: young adult male
example 1, exampl...
In the pre-multidetector CT era, mesenteric lymph nodes were only really appreciated when enlarged. Following the advent of routine volume acquisition CT (and especially coronal reformats) they are commonly seen in normal individuals, which has raised the obvious question of what counts as mesen...
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...
Normal postmortem changes in the gastrointestinal tract refers to the normal changes that can be expected to be seen in the gastrointestinal tract on post-mortem imaging.
The following changes may be present in the abdomen and gastrointestinal tract 1:
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.
This is a basic article for medical students and other non-radiologists
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 a...
Obturator hernias are characterised by bowel herniating between the obturator and the pectineus muscles. They are a rare type of abdominal hernia and can be very difficult to diagnose clinically.
Typically obturator hernias occur in elderly women 3,4 or patients with chronically r...
Octreotide scintigraphy uses 111In-labelled octreotide which is a somatostatin analog; it is also known as an OctreoscanTM, a brand name for 111In-labelled pentetreotide; pentetreotide is a DTPA-conjugated form of octreotide, originally manufactured by Mallinckrodt Nuclear Medicine LLC, which no...
An oesophageal atresia refers to an absence in the 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 bir...
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...
This is a basic article for medical students and other non-radiologists
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.
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 from complete (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 duplication is a rare ma...
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 acute dysphagia.
Depending on the composition of the ingested content, the bolus may be vis...
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 intubation refers to the incorrect placement of an endotracheal tube in the oesophagus. Within minutes its consequences can be catastrophic with the seriousness of its outcome depending largely on the timeliness of its diagnosis.
Accidental oesophageal intubation can h...
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.
Oesophageal leiomyosarcoma is a rare disease. Since first described in 1905, there have been over 164 cases described in the literature.
Oesophageal lipomas (or lipomata) are rare fat-containing oesophageal lesions.
They may account for approximately 0.4% of the benign tumours of the alimentary tract 1. There may be greater male predilection. The average age of presentation is around 50 years.
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 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 can b...
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...
An omentum is a double layer of peritoneum that attaches the stomach to another viscus:
the greater omentum hangs from the greater curvature of the stomach like an apron
the lesser omentum attaches the lesser curvature of the stomach to the liver superiorly
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 diabe...
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 from many aetiologies.
Punctate intraductal calcifications
alcoholic pancreatitis (20-40%) 2
intraductal, numerous, small, irregular
preponderant cause of diffuse pancreatic intraductal calcification
gallstone pancreatitis (2%) 2
Staging of pancreatic ductal adenocarcinoma is traditionally done according to American Joint Committee on Cancer (AJCC) / Union for International Cancer Control (IUCC) TNM system. In 2017 new edition (8th edition) AJCC published with some major changes; now exocrine and endocrine tumours of th...
The ductal embryology of the pancreas 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 s...
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
Mostly flat lesions ...
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...
Pancreatic lipomatosis refers to the fatty replacement of pancreatic parenchyma. This finding is most often associated with obesity and ageing.
It tends to be commonest pathological condition involving the pancreas. The condition may occasionally simulate a mass-like lesion particularly when f...