Lysosomal storage disorders (LSDs) form a large group of clinical entities, more than forty now described, with the common etiological theme being the presence of dysfunctional lysosomal proteins, with the secondary accumulation of toxic metabolites inside the cellular lysosomes.
Macroamylasemia is the presence of serum amylase of a large molecular size, seen in both otherwise healthy individuals, and also in various diseases. Amylase seems to be able to self-polymerize and/or form complexes with other blood proteins, e.g. immunoglobulins.
Macrolipasemia is the presence of serum lipase of a large molecular size, seen occasionally in otherwise healthy individuals, but more commonly in various diseases. Lipase is able to self-polymerize and/or form complexes with other blood proteins e.g. immunoglobulins.
The term magenstrasse refers to a tubular portion of the stomach adjacent to the lesser curve of the stomach. It is a favored route by food, fluids and drugs as they flow from the cardia/fundus to the gastric outlet 1.
Magenstrasse is an old German anatomical term that has come back into common...
Magnetic resonance cholangiopancreatography (MRCP) is a non-invasive imaging technique to visualize the intra and extrahepatic biliary tree and pancreatic ductal system.
It can provide the diagnostic range equivalent to the ERCP and so it can replace the ERCP in high risk patients to avoid sign...
This is a basic article for medical students and other non-radiologists
Malignant biliary tract obstruction (MBTO) represents a group of conditions that cause obstructive jaundice. While most examples are the result of pancreatic head cancers, other malignancies may be causative.
Malignant esophageal neoplasms are much more common than benign esophageal neoplasms, especially if the patient is symptomatic.
esophageal carcinoma (90%)
esophageal squamous cell carcinoma (SCC)
esophageal spindle cell carcinoma
Malignant peritoneal mesothelioma is an uncommon primary tumor of the peritoneal lining. It shares epidemiological and pathological features with - but is less common than - its pleural counterpart, which is described in detail in the general article on mesothelioma. Other abdominal subtypes (al...
Barium meal has been frequently used to differentiate malignant and benign gastric ulcers:
Features suggesting benign gastric ulcer
outpouching of ulcer crater beyond the gastric contour (exoluminal)
smooth rounded and deep ulcer crater
smooth ulcer mound
smooth gastric folds that reach the...
Mallory-Weiss tears occur due to violent projection of gastric contents against the lower esophagus, which results in mucosal and submucosal tear with involvement of the venous plexus. The resultant clinical syndrome is known as Mallory-Weiss syndrome.
Patients present w...
Malone antegrade continence enema is a surgical procedure where the vermiform appendix or ‘neoappendix’ is used to create a small stoma at the abdominal wall allowing antegrade enemas to be administered to empty the colorectum. This procedure is important particularly in children and adolescents...
The marginal artery of Drummond, also known as the marginal artery of the colon, is a continuous arterial circle or arcade along the inner border of the colon formed by the anastomoses of the terminal branches of the superior mesenteric artery (SMA) and inferior mesenteric artery (IMA).
Remembering the colon vascular supply can be confusing because of inconstant collateral vascularization, therefore mnemonics can be helpful.
One way to remember the location of the marginal artery of Drummond is to remember that it runs distally to the root of the mesentery (near the colon).
Mass-forming chronic pancreatitis occurs in around 30% of cases of chronic pancreatitis, where a mass or a focal enlargement of the pancreas is usually seen on imaging. In many instances, it poses a challenge as the epidemiology and imaging appearances overlap those of pancreatic adenocarcinoma....
The differential diagnosis of a mass in the inguinal region includes:
hydrocele of the canal of Nuck
spermatic cord hydrocele
lymphadenopathy or necrotic lymph node
aneurysm or pseudoaneurysm of the femoral artery
Maydl hernias (alternative plural: herniae) are defined as the presence of two small bowel loops within a single hernial sac, that is, there are two efferent and two afferent loops of bowel, forming a "W" shape. Hence sometimes known as a W hernia or a hernia-in-W.
This type of hernia is more p...
McBurney point is defined as a point that lies one-third of the distance laterally on a line drawn from the umbilicus to the right anterior superior iliac spine. Classically, it corresponds to the location of the base of the appendix 1.
Clinically, McBurney point is relevant for the elicitation...
The McKeown procedure ("tri-incisional esophagectomy") is a type of esophagectomy, that is similar in concept to an Ivor Lewis procedure, but it tends to be used for esophageal lesions that are higher in the esophagus.
stomach mobilized, the esophagus
"gastric tube" may ...
Meandering main pancreatic duct (MMPD) comprises of a reverse Z-type and loop-type of pancreatic ducts.
These ductal variants are found in ERCP and MRCP studies. The exact incidence is not known.
Increased incidence of meandering pancreatic duct has been reported in patients with idiopathic re...
Meckel diverticulitis is the inflammation of Meckel diverticulum, which is the most common congenital structural abnormality of the gastrointestinal tract 3. Despite this, it is an uncommon cause of acute abdomen and is often not correctly diagnosed pre-operatively.
This article focuses on Mec...
Meckel diverticulum is a congenital intestinal diverticulum due to fibrous degeneration of the umbilical end of the omphalomesenteric (vitelline) duct that occurs around the distal ileum. It is considered the most common structural congenital anomaly of the gastrointestinal tract.
Meconium ileus refers to a neonatal bowel obstruction of the distal ileum due to abnormally thick and impacted meconium. Unlike in the meconium plug syndrome, the meconium is abnormal in consistency.
Meconium ileus is more common in white populations and affects both sexes almost ...
Meconium peritonitis refers to a sterile chemical peritonitis due to intra-uterine bowel perforation and spillage of fetal meconium into the fetal peritoneal cavity. It is a common cause of peritoneal calcification.
The estimated prevalence is at ~1 in 35,000.
The medial fossae are concave depressions of peritoneum in the paravesical space bounded by the medial umbilical folds and the lateral umbilical folds. The fossae are contained within the inguinal (Hesselbach’s) triangle. The right medial fossa typically partially contains the cecum and/or ileum...
The medial umbilical folds are bilateral raised ridges of parietal peritoneum in the deep aspect of the anterior abdominal wall formed by the underlying medial umbilical ligaments running from the pelvis to the umbilicus. The medial umbilical ligaments are anatomical remnants of the obliterated ...
A mediastinal pseudocyst is the extension of pancreatic pseudocyst into the posterior mediastinum through esophageal or aortic hiatus or rarely through the foramen of Morgagni. It is a rare complication of acute or chronic pancreatitis.
It can present with symptoms due to...
Medical devices in the abdomen and pelvis are important to be recognized, just like medical devices of the chest. Often we ignore these devices, considering them to be incidental and non-pathological, however it is essential to be aware of potential complications.
Megaesophagus or diffuse esophageal dilatation can be caused by a variety of conditions.
Some of the more common causes are given below 1-3:
malignant stricture, e.g. esophageal cancer, ca...
Melioidosis is an infectious disease caused by the bacterium Burkholderia pseudomallei (previously known as Pseudomonas pseudomallei) and is a multisystem disorder which may affect the lungs, brain, visceral organs, or musculoskeletal system.
Melioidosis is a disease of the monsoo...
Mnemonics to remember the classic triad of multiple endocrine neoplasia type 1 (MEN1) are:
P: pituitary adenoma: prolactinoma is commonest
P: pancreatic endocrine tumors
P: parathyroid proliferative disease
parathyroid hyperplasia (most common)
Ménétrier disease, also known as giant hypertrophic gastritis or hypoproteinemic hypertrophic gastropathy, is a form of rare idiopathic hypertrophic gastropathy.
Rare disease with incidence <1 per 200,000. Bimodal in distribution, children often <10 years; adult forms 30-60 years,...
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 (rare plural: adenitides) (less commonly called mesenteric lymphadenitis (rare plural: lymphadenitides)) is a self-limiting inflammatory process that affects the mesenteric lymph nodes in the right lower quadrant and is clinically often thought initially to be acute appendici...
Mesenteric arteritis is an unusual cause of mesenteric ischemia. However, it should be considered when locations are atypical such as stomach, duodenum, rectum (small and large intestine involved at the same time) with the involvement of the genitourinary system, especially in young patients 1....
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, although...
Mesenteric desmoid tumors are a subtype of desmoid tumors.
Desmoids are cytologically bland tumors that appear as infiltrative, well-demarcated tumors that are derived from musculo-aponeurotic structures throughout the body.
in the mesentery, the masses may occur spor...
Mesenteric ischemia, also commonly referred to as bowel or intestinal ischemia, refers to vascular compromise of the bowel and its mesentery that in the acute setting has a very high mortality if not treated expediently. Mesenteric ischemia is far more commonly acute than chronic in etiology. Th...
Mesenteric lipomas are uncommon benign fat-containing lesions .
Like other lipomas, they are comprised of mature adipocytes.
Although described on both CT and ultrasound, they are more commonly seen on CT.
proliferation of homogenous adipose tissue in the mes...
In the premultidetector CT era, mesenteric lymph nodes (often shortened to mesenteric nodes) were only really appreciated when enlarged. Following the advent of routine volume acquisition CT (and especially coronal reformats) lymph nodes in the mesentery are commonly seen in normal individuals, ...
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 ileocecal junction. It usually extends to the tip of the appendix and sometimes suspends the...
The mesorectal fascia is a layer of connective tissue enclosing the perirectal fat that surrounds the rectum. It is an important anatomical structure in rectal cancer staging, as it forms the circumferential resection margin for the non-peritonealised portion of the rectum.
Mesorectal lymph nodes refers to lymph nodes that are present in the mesorectal fascia. Their assessment is important in the staging of colorectal tumors such as rectal cancer and anal cancer.
According to one study, the majority of nodes were located in the proximal two-thirds ...
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 a changed cellular environment to which the new cell type is better adapted 1. Examples include 2-5:
Barrett esophagus: normal squamous epithelium replace...
MIBG scan is a scintigraphic study that uses metaiodobenzylguanidine, norepinephrine analog, labeled to iodine-123 or iodine-131. It is indicated in the investigation of pheochromocytoma.
MIBG is positive in:
olfactory neuroblastoma 1
carcinoid tumor 4
The middle colic artery is a branch of the superior mesenteric artery (SMA) and supplies the marginal artery.
The middle colic artery passes in the layers of the transverse mesocolon to the transverse colon and divides into right and left branches
right branch supplies the right portio...
The middle rectal artery, also known as the middle hemorrhoidal 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, prostat...
Midgut volvulus is a complication of malrotated bowel. It may result in proximal bowel obstruction with resultant ischemia 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 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, edema, lymphatic accumulation, hemorrhage, tumor infiltr...
Mobile cecum is an anatomical variant and is often defined as a failure of the cecum, terminal ileum, and right colon, along with the mesentery, to fuse to the posterior parietal peritoneal wall. This results in increased mobility of the cecum.
It has been estimated to occur in 10...
Mobile cecum syndrome refers to a symptomatic mobile cecum, manifesting as chronic intermittent right lower quadrant pain and distension.
Uncommon diagnosis in that 10% of the population who have a mobile cecum, as it is usually asymptomatic.
Owing to a redundant mesoc...
The modified CT severity index is an extension of the original CT severity index (CTSI) which 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...
Morgagni hernias (alternative plural: herniae) are one of the congenital diaphragmatic hernias (CDHs), and are characterized by herniation through the foramen of Morgagni. When compared to Bochdalek hernias, Morgagni hernias tend to be:
more often right-sided (~90%)
rare (~2% ...
The moulage sign is related to sprue, in particular celiac 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/molding) is the art of appl...
MR defecating proctography 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.
Note: This article is intended to outline some general principles of protocol design. The specifics will vary depending on MRI hardware and software, radiologist's and referrer's prefere...
MR enterography (MRE) is a non-invasive technique for the diagnosis of small bowel disorders.
Note: This article is intended to outline some general principles of protocol design. The specifics will vary depending on MRI hardware and software, radiologist's and referrer's preference, institutio...
Mucinous adenocarcinomas of the appendix are at the malignant end of the spectrum of the mucinous neoplasms that affect the cecal appendix.
For the mucinous carcinomas involving the remainder of the colon, please refer to the article on mucinous carcinoma of the colon.
The peak ...
Mucinous carcinoma of the colon is a distinct form of colorectal cancer found in 10-15% of patients with colorectal cancer. It differs from conventional adenocarcinoma in terms of clinical and histopathological characteristics.
For the cecal appendix, please refer to the article on mucinous ade...
Mucinous cystadenocarcinomas of the pancreas are a type of pancreatic mucinous tumor. 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 tumors of the appendix that produce mucin. They represent a spectrum of malignant potential, and are the most common cause of pseudomyxoma peritonei.
According to a panel of specialists consensus published in 2016 (Per...
Mucous fistulas are a surgically-formed 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...
Muir-Torre syndrome is a rare variant of hereditary nonpolyposis colorectal cancer (HNPCC), characterized 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 1 (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 the rectosigmoid colon.
The hypertrophic muscularis propria appears as heterogeneous low signal intensity surrounded by the high signal...
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.
double track sign
Mycosis fungoides (MF) is a type of malignant cutaneous primary T-cell lymphoma.
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 rare in Asian countries.
It is usual...
Mycotic aneurysms are aneurysms arising from infection of the arterial wall, usually bacterial. It is a complication of the hematogenous spread of bacterial infection, classically from the heart.
Mycotic aneurysms are thought to represent only a minority of (0.7-2.6%) of all aort...
The myenteric plexus (also known as the Auerbach plexus) (plural: plexuses) refers to a network of nerves between the layers of the muscular propria in the gastrointestinal system. Among other things, the plexus helps regulate peristalsis in the gastrointestinal tract.
The plexus is part of the...
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 ...
The napkin ring sign may refer to either of the following imaging findings:
napkin ring sign (colon): colonic stenosis such as due to colon cancer
napkin ring sign (coronary): coronary artery vulnerable plaque
A napkin ring is a decorative household item used in some Western societies to hold...
Assessment of nasogastric (NG) tube positioning is a key competency of all doctors as unidentified malpositioning may have dire consequences, including death.
Evaluation of Nasogastric tube
A correctly placed nasogastric tube should 10:
descend in the midline, following 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.
Necrotizing enterocolitis (NEC) is the most common gastrointestinal condition in premature neonates. It is characterized by inflammation, ischemia, and permeability of the neonatal bowel wall to bacteria. It is potentially life-threatening with significant associated morbidity 1.
Necrotizing enterocolitis (NEC) can be staged into three groups, to guide appropriate treatment based on the work of Bell et al. 1. In general, stage I and II are managed medically whereas stage III is managed surgically.
lethargy, temperature instability, apnea, bradyc...
Necrotizing 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...
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...
Neonatal appendicitis is rare, presumably in part due to the short funnel shape of the appendix at that age. Symptoms are non-specific and may mimic necrotizing enterocolitis.
The causes of neonatal pneumoperitoneum are different from adult pneumoperitoneum and include:
perforated hollow viscus
necrotizing 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.
Tumors involving the appendix have been found in only about 1% of all appendectomy specimens 9. Epithelial neoplasms and neuroendocrine tumors represent the vast major...
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 ileocecal valve or with small-bowel follow-through.
Although classically described with m...
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-occlusive mesenteric ischemia is the second most common cause of acute mesenteric ischemia, with a higher incidence in hospitalized and critical care patients.
Non-occlusive mesenteric ischemia accounts for ~25% (range 20-30%) of acute mesenteric ischemia. It most commonly af...
Non-specific esophageal motility disorder (NSMD) is one of the esophageal dysmotility disorders. It is used to describe patients with esophageal dysmotility that do not meet diagnostic criteria for other esophageal motility disorders.
Patients may be asymptomatic or pres...
This article lists examples of normal imaging of the gastrointestinal tract and surrounding structures, divided by modality.
example 2: erect and supine
example 3: pediatric
example 4: pediatric
example 5: young adult male
There are a number of normal esophageal 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.
The nutcracker phenomenon, also known as nutcracker anatomy or left renal vein entrapment, refers to the anatomic or pathophysiologic entity wherein the superior mesenteric artery compresses and impedes outflow of the left renal vein into the inferior vena cava. It can be a common incidental fin...