Pre-aortic nodes are part of the abdominopelvic lymph nodes. They include 3 main groups:
drainage from gastric nodes, hepatic nodes and pancreaticosplenic nodes
superior mesenteric nodes
drainage from mesenteric nodes
inferior mesenteric nodes
drainage from mesenteric nodes
The presacral space is located between the rectum and the sacrococcygeal part of the spine.
The presacral space contains a variety of tissue:
superior - peritoneal reflections
inferior - ...
Presbyoesophagus is term that has been traditionally used to describe the manifestations of degenerating motor function in the aging oesophagus.
Presbyoesophagus remains controversial given it was initially described in elderly patients with significant co-morbidities (e.g. dementia, diabetes),...
Primary cutaneous melanoma is the most common subtype of malignant melanoma, a malignant neoplasm that arises from melanocytes. Melanocytes predominantly occur in the basal layer of the epidermis but do occur elsewhere in the body. Primary cutaneous melanoma is by far the most common type of pri...
Primary peritoneal neoplasms comprise of an uncommon group of heterogenous entities.
The list includes:
primary (malignant) peritoneal mesothelioma
primary perioneal multicystic mesothelioma
primary peritoneal well differentiated papillary mesothelioma
Primary pneumatosis intestinalis (PPI) is a benign idiopathic condition in which multiple gas-filled cystic lesions are seen in the gastrointestinal tract wall. The changes are usually seen initially on radiography or CT with CT being the more sensitive test.
Primary pneumatosis i...
Primary retroperitoneal neoplasms are an extremely rare group of tumours (lymphoma is not included in this definition). The most common type is soft tissue sarcoma (90%).
The most common age for presentation is 40-50 years.
Frequently tumours have relative...
A primary serous papillary carcinoma of the peritoneum (PSPCP) is an extremely rare primary peritoneal tumour.
They usually present in postmenopausal women.
Patients tend to present with non-specific complaints such as abdominal pain, anorexia, and abdomina...
The properitoneal fat, deep to the transversalis fascia, fills the posterior pararenal space. Laterally it thickens and forms the properitoneal fat pad, which is an anterior extension of posterior pararenal space.
The properitoneal fat pad is known as a plane in surgical anatomy, a...
Pseudoachalasia is achalasia-pattern dilatation of the oesophagus due to the narrowing of the distal oesophagus from causes other than primary denervation. One of the most common causes is malignancy (often submucosal gastric cancer) with extension in the lower oesophagus. The clinical and imagi...
Pseudomyxoma peritonei refers to the intraperitoneal accumulation of a gelatinous ascites secondary to rupture of a mucinous tumour. The most common cause is a ruptured mucinous tumour of the appendix/appendiceal mucocoele 10.
Occasionally, mucinous tumours of the colon, rectum, stomach, panc...
Pseudopancreatitis refers to the presence of fluid in or around the pancreas in the setting of trauma but in the absence of direct signs of traumatic pancreatic injury. Most patients will have a normal serum lipase level, but amylase has a limited sensitivity and specificity for pancreatic traum...
Pseudopneumoperitoneum describes any gas within the abdominal cavity that masquerades as free intraperitoneal gas or pneumoperitoneum when it is in fact contained within an organ. Correctly identifying pneumoperitoneum is important, but making the diagnosis in error may lead to further unnecessa...
The pseudovein sign can occur with active gastrointestinal bleeding where contrast extravasation during angiography may have a curvilinear appearance as it pools in the gastric rugae or mucosal folds of bowel, mimicking the appearance of a vein. However, contrast in the “pseudovein” persists bey...
Hypertrophic pyloric stenosis (HPS) refers to the idiopathic thickening of gastric pyloric musculature which then results in progressive gastric outlet obstruction.
Pyloric stenosis is relatively common and has a male predilection (M:F ~4:1), and is more commonly seen in Caucasia...
Radiation enteritis is a bowel pathology resulting from toxic effects of radiotherapy on the bowel wall and vasculature.
5-15% of patients treated with radiotherapy (usually > 4500cGy) develop chronic radiation enteropathy.
The clinical presentation is non...
Radiological signs are described across the disciplines of imaging, including the gastrointestinal tract. Fruit-inspired, nature-related, and more feature in the list of signs described for a wide array of pathology. How fascinating are the minds of radiologists work in describing pathology?
Ranson's criteria are useful in assessing prognosis in early acute pancreatitis. The more of the criteria are met the higher the mortality. Ranson's criteria are assessed both at admission and at 48 hours.
age: >55 years
white blood count: >16 000/mm
blood glucose leve...
Rapunzel syndrome is the term for a trichobezoar (gastric 'hair ball') which has a tail-like extension into the small bowel through the pylorus causing gastric outlet obstruction.
Human hair (especially long hair) is resistant to digestion as well as peristalsis. So it tends to stay in the sto...
RASopathies are a class of developmental disorders caused by germline mutations in genes that encode for components or regulators of the Ras/mitogen activated protein kinase (MAPK) pathway.
As a group, RASopathies represent one of the most common malformation syndromes, with an in...
The rat-tail sign is used to refer to the tapering of the inferior oesophagus in achalasia. The same appearance (although it is difficult to see the similarity) is also referred to as the bird beak sign (oesophagus).
Radiological manifestations of recreational drug use are not infrequently seen as the use of recreational drugs is widespread.
Interestingly, recent reports have suggested a decreasing incidence of reported drug use in the general population over the past decade, but it remains th...
Rectal cancer, although sharing many of the features of generic colorectal carcinoma (CRC), has some features that make it unique. These are predominantly related to its anatomical location which has implications in both preoperative imaging assessment and surgical technique.
Demographics and c...
Pelvic MRI protocol for rectal cancer includes:
through tumour (always ensure planes are exactly perpendicular to the wall)
narrow field of view images to be included
Staging strongly influences the success of, and rate of local recurrence following rectal cancer resection. In rectal cancer, pre-treatment MRI is the evaluation of choice, guiding surgical and non-surgical management options.
See: TNM staging system for a general description.
Rectal foreign bodies are not uncommon in emergency departments around the world, and although they are often the source of endless amusement do potentially cause management difficulties.
The incidence varies according to the region, said to be uncommon in Asia and most common in ...
Rectocoele refers to a herniation or bulge of the rectal wall, with the most common type being an anterior rectocoele where the bulge is into the posterior vaginal wall in a female patient. Rectocoeles can also occur posteriorly or laterally. Rectocoele is the term most commonly used by colorect...
The rectosigmoid ratio is a measurement of the diameter of the rectum divided by that of the sigmoid colon during contrast enema. It is of particular use in the diagnosis of Hirschsprung disease.
Normal children have a rectum that is larger than the sigmoid (i.e. rectosigmoid ration >1). In fac...
Rectovesical pouch is the forward reflection of the peritoneum from the lower third of the rectum to the upper part of the bladder in males.
The rectovesical pouch is the lowest part of the peritoneal cavity and usually contains loops of small bowel or sigmoid colon. It is 7.5 cm...
The rectum is the last part of the large intestine. It is located within the pelvis and is the continuation of the sigmoid colon after the rectosigmoid junction and continues as the anal canal at the angle created by puborectalis.
At the level of the S3 vertebral body, the sigmo...
Retained barium in appendix refers to the presence of barium in appendix beyond 72 hours from the start of procedure.
Previously used as a sign of appendicitis.
Retained barium outlining the appendiceal lumen allows evaluation of its width and contou...
Retroperitoneal fasciitis is a rare potentially life-threatening infection of the retroperitoneum. It is the retroperitoneal equivalent of necrotizing fasciitis or non-necrotizing soft tissue fasciitis, and just like its soft tissue counterpart, can also be either necrotizing or not.
Retroperitoneal haemangiomas are almost always of the cavernous haemangioma2.
They tend to be asymptomatic, especially in the early stages of their development, but when present, symptoms are non-specific and due to mass effect on adjacent anatomic structure.
Retroperitoneal hydatid infection refers to the presence of hydatid cyst in the retroperitoneal region of the abdomen. See Hydatid disease for a general discussion.
It is generally seen secondary to intraperitoneal (mainly hepatic) infection. Isolated occurrence is rare.
Retroperitoneal liposarcoma is a subtype of liposarcoma, and is a malignant tumour of mesenchymal origin that may arise in any fat-containing region of the body. It is one of the most common primary retroperitoneal neoplasms 2.
There are five histological types:
A useful for mnemonic to remember which organs are retroperitoneal is:
S: suprarenal (adrenal) gland
D: duodenum (second and third part)
P: pancreas (except tail)
C: colon (ascending and descending)
The retroperitoneum is the part of the abdominal cavity that lies between the posterior parietal peritoneum and anterior to the transversalis fascia.
It is divided into three spaces by the perirenal fascia and is best visualised using CT or MRI. The three spaces are:
anterior pararenal space
The reverse figure 3 sign (also known as the E sign) is seen on barium swallows in patients with a coarctation of the aorta and is the medial equivalent of the figure 3 sign seen on plain chest radiographs. It is formed by prestenotic dilatation of the ascending aorta, indentation of the coarcta...
The Revised Atlanta classification of acute pancreatitis (2012) is an international multidisciplinary classification of the severity of acute pancreatitis, updating the 1991 Atlanta classification. This has been further revised in 2016 6.
The worldwide consensus aims for an internationally agre...
Richter hernias are an abdominal hernia where only a portion of the bowel wall is herniated and comprise 10% of strangulated hernias. These hernias progress more rapidly to gangrene than other strangulated hernias but obstruction is less frequent.
In contrast to most other types of ...
The right colic artery may arise directly from the superior mesenteric artery (SMA) but often arises from a common trunk with the ileocolic artery or middle colic artery.
It courses to the right to the ascending colon and divides into a descending branch that supplies the lower portion of the a...
Right colic flexure (or hepatic flexure) is used to describe the bend in the colon as the ascending colon continues as the transverse colon.
Connective tissue connects this part of the colon to the anterior pararenal fascia, descending part of the duodenum (D2) and head of pancr...
The right gastric artery is a branch of the common hepatic artery which supplies the lesser curvature of the stomach.
The right gastric artery branches off from the common hepatic artery as it turns into the lesser omentum. It runs along the lesser curvature of the stomac...
The right gastroepiploic artery (RGA) arises from the gastroduodenal artery as it divides into its two terminal branches, the right gastroepiploic artery and the superior pancreaticoduodenal artery.
The RGA passes between the first part of the duodenum and the pancreas, ...
Right iliac fossa mass is a common clinical presentation and has a range of differentials that need to be excluded. Radiology plays an important role in this differentiation.
The right subphrenic space (a.k.a. right anterior space, right subdiaphragmatic space) is a potential space that lies between the right lobe of the liver and the inferior surface of the diaphragm.
This is a subcompartment of the supracolic compartment. It reaches as far as the up...
The Rigler sign, also known as the double wall sign, is seen on a radiograph of the abdomen when the air is present on both sides of the intestine, i.e. when there is air on both the luminal and peritoneal side of the bowel wall.
Pneumoperitoneum may be a result of perforation or, from recent i...
Ring shadows are radiographic signs seen on either chest x-rays or on upper gastrointestinal fluoroscopy:
ring shadow (chest)
ring shadow (abdomen)
Rokitansky-Aschoff sinuses are diverticula of the gallbladder wall which may be microscopic or macroscopic. Histologically, they are outpouchings of gallbladder mucosa that sit within the gallbladder muscle layer.
They are not of themselves considered abnormal, but may be ass...
Rose-thorn ulcers or rose-thorn appearance refers to deep penetrating linear ulcers or fissuring typically seen within stenosed terminal ileum with a thickened wall. They appear as thorn-like extraluminal projections on barium studies and this appearance is one of the typical signs of Crohn dise...
In many centers, laparoscopic Roux-en-Y gastric bypass has become the most common bariatric procedure for morbid obesity.
In this operation, the stomach is stapled or divided to form a small pouch (typically <30 mL in volume), which empties into a Roux limb of the jejunum of varying length (ty...
A Roux limb may be formed in multiple different gastrointestinal surgeries, including
bariatric surgery, e.g.
Roux-en-Y gastric bypass
partial pancreaticoduodenectomy (Whipple procedure)
In these surgeries the small bowel is ...
The rugal folds are the mucosal folds within the stomach that give the distinctive appearance on barium studies.
The rule of 2s is a useful mnemonic for Meckel diverticulum.
occur in 2% of the population
are 2 inches (5cm) long
are 2 feet (60cm) from the ileocaecal valve
2/3rds have ectopic mucosa
2 types of ectopic tissue are commonly present (mostly gastric and pancreatic)
The saber sign refers to a pattern of gas distribution seen in supine abdominal radiographs of patients with pneumobilia. A sword-shaped lucency is apparent in the right paraspinal region of the upper abdomen representing arching gas extending from the common bile duct into the left hepatic duc...
A sandwich sign, sometimes known as a hamburger sign, refers to a mesenteric nodal mass, either para-aortic or not, giving an appearance of a hamburger. Confluent lymphadenopathy on both sides of the mesenteric vessels gives rise to an appearance described as the sandwich sign 2.
The sign is sp...
A Schatzki ring, also called Schatzki-Gary ring, is symptomatically narrow oesophageal B-ring occurring in the distal oesophagus and usually associated with a hiatus hernia.
Relatively common, lower oesophageal rings are found in ~10% of oesophagrams.
Scirrhous carcinoma of the gastrointestinal tract is a subtype of primary adenocarcinoma of the gastrointestinal (GI) tract.
It is the least common type of primary adenocarcinoma involving mainly the stomach and the colon.
The tumour demonstrates an infiltrative behavi...
Scleroderma, also known as systemic sclerosis, is a multisystem autoimmune connective tissue disorder. As such, it affects many separate organ systems, which are discussed separately:
musculoskeletal manifestations of scleroderma
pulmonary manifestations of scleroderma
cardiac manifestations ...
Gastrointestinal manifestations of scleroderma can occur in up to 90% of patients with scleroderma 2 with the commonest site of GI involvement being the oesophagus.
As clinical presentation, radiographic appearances and differential diagnosis vary with the location of involvement these are disc...
Sclerosing encapsulating peritonitis is a rare benign cause of acute or subacute small bowel obstruction. It is characterised by total or partial encasement of the small bowel within a thick fibrocollagenous membrane.
The condition was originally termed abdominal cocoon. It has als...
Sclerosing mesenteritis (or mesenteric panniculitis) is an uncommon idiopathic disorder characterised by chronic non-specific inflammation involving the adipose tissue of the bowel mesentery.
Typically this condition afflicts adults in their sixties with mild male predilection, ...
The seatbelt sign is both a clinical and radiological sign. It is simply the presence of bruising/abrasions in the distribution of a seatbelt (i.e. horizontal and/or diagonal) across the abdomen, chest and sometimes neck.
A positive seatbelt sign, in combination with abdominal pain or tenderne...
The seatbelt syndrome is the constellation of traumatic injuries associated with three-point seatbelts:
lumbar spine fracture
Segmental arterial mediolysis (SAM) is an increasingly recognised vascular disease of the middle-aged and elderly and a leading cause of spontanoeus intra-abdominal haemorrhage. It is characterised by fusiform aneurysms, stenoses, dissections and occlusions within splanchnic arterial branches. I...
Segmental pancreatitis is not a distinct entity in itself but describes an imaging differential.
With segmental pancreatitis, a patient presents with clinical pancreatitis (signs, symptoms, laboratory markers), but on imaging, only a portion of the gland appears to have c...
SeHCAT (23-seleno-25-homo-tauro-cholic acid) is a radiopharmaceutical used in the investigation of bile salt malabsorption, which is a cause of chronic diarrhoea.
physical half-life: 118 days
Uses, dosage and timings
A capsule containing SeHCAT is ingested with water. The pa...
The semilunar line, linea semilunaris or Spigelian line is a bilateral vertical curved line in the anterior abdominal wall where the layers of the rectus sheath fuse lateral to the rectus abdominis muscle and medial to the oblique muscles.
It is the site of a Spigelian hernia.
A sentinel loop is a short segment of adynamic ileus close to an intra-abdominal inflammatory process.
The sentinel loop sign may aid in localising the source of inflammation. For example, a sentinel loop in the upper abdomen may indicate pancreatitis, while one in the right lower quadrant may ...
Serous cystadenoma of the pancreas (or microcystic adenoma) is an uncommon type of benign cystic pancreatic neoplasm.
There is a recognised strong female predilection (M:F ~ 1:4) and usually presents in middle age to elderly patients (>60 years of age).
Serrated polyposis syndrome (SPS), also called hyperplastic polyposis syndrome, is characterised by the presence of multiple serrated polyps or a mixture of serrated and hyperplastic polyps, with the exact number required for diagnosis dependent on location and family history.
SPS has an hetero...
Seurat spleen is an angiographic appearance seen following blunt trauma to the spleen. Multiple small punctate regions of intraparenchymal contrast extravasation lead to a spotted appearance.
History and etymology
The term refers to a likeness between the angiographic appearance and the artwor...
Shading sign is an MRI finding typically seen in an endometrioma. It may also be seen with some endometrioid tumours (e.g endometrioid carcinoma of the ovary)
It helps to distinguish endometriomas from other blood-containing lesions (e.g. haemorrhagic corpus luteum cysts), with a sensitivity of...
Shock bowel is the appearance of the bowel in a state of hypotension. It is usually seen as part of the CT hypoperfusion complex.
thickened bowel loops (>3 mm) with enhancing walls (the reason the condition was previously known as "shock bowel")
on non-contrasted im...
The short gastric arteries are a group of short arteries arising from the terminal splenic artery and the left gastroepiploic artery which supply the fundus of the stomach along it's greater curvature.
The vessels are short in length, variable in number and course through the gastrosplenic liga...
The Shwachman-Diamond syndrome (SDS) or Shwachman-Bodian-Diamond syndrome (SBDS) is a rare autosomal recessive disorder characterised by 1 :
exocrine pancreatic insufficiency
bone marrow hypoplasia (cyclic neutropenia)
Patients with Shwachman-...
The sigmoid arteries are branches, between two-to-four, of the inferior mesenteric artery (IMA) and supply the sigmoid colon.
origin: inferior mesenteric artery
course: after arising from IMA, these branches descend to the left in the sigmoid mesocolon
superiorly with ...
The sigmoid colon is the continuation of the descending colon.
After the distal descending colon has curved medially it enters the pelvis, where it gains a mesentery and is then called the sigmoid colon. It measures approximately 15 cm in length.
It has a "S" (Greek letter sigm...
The sigmoid mesocolon
is a fold of peritoneum that attaches the sigmoid colon to the pelvic
wall and one of the four mesenteries in the abdominal cavity.
It has an "inverted V" line of attachment, the apex of which is
near the division of the left common iliac artery.
The left limb descends...
Intersigmoid hernias, also known as sigmoid mesocolon hernias, occur when small bowel loops protrude into a peritoneal pocket (intersigmoid fossa) formed between two adjacent sigmoid segments and their mesentery.
Sigmoid mesocolon hernias account for ~5% of all internal hernias 1-...
Sigmoid volvulus is a cause of large bowel obstruction and occurs when the sigmoid colon twists on its mesentery, the sigmoid mesocolon.
Large bowel volvulus accounts for ~5% of all large bowel obstructions, with ~60% of intestinal volvulus involving the sigmoid colon 6. It is mor...
Single contrast barium enema is a method of imaging the colon with fluoroscopy and is similar in concept to the double contrast barium enema. "Single contrast" refers to imaging with barium or water-soluble contrast only, without addition of gas or CO2.
The single contrast techniqu...
A Sister Mary Joseph nodule is a metastatic lesion involving the umbilicus. The most common primary source is an intra-abdominal adenocarcinoma.
Umbilical metastases are uncommon, reportedly present in 1-3% of all intra-abdominal and/or pelvic malignancy 7.
The Sitz marker study is an older technique to estimate colonic transit time.
In constipation it can help distinguish between slow colonic transit and a defecation disorder.
The patient ingests a number of radio-opaque markers (plastic rings containing radio-opaque mat...
A mnemonic for the skin changes associated with mercury poisoning is:
Sleeve gastrectomy is a bariatric surgical procedure involving resection of the greater curvature of the fundus and body of the stomach to leave approximately 15% of the original gastric volume (60 to 100 cc), thus creating a restrictive physiology. The post-surgical gastric pouch resembles a ba...
The small bowel (or small intestine) is the section of bowel between the stomach and the colon. It has distinctive mucosal folds, valvulae conniventes, and is made up of three functional units:
See main article: barium studies of sma...
Small bowel atresia corresponds to malformations where there is a narrowing or absence of a portion of the small bowel, which includes:
The small bowel carcinoid tumours are the most common gastrointestinal carcinoid tumours. Within the small bowel, the most common site is at the terminal ileum.
Small bowel carcinoid tumours account for ~40% of gastrointestinal carcinoid tumours 1.
The small bowel faeces sign can be observed on abdominal CT scans. The sign has been described as a finding specific for small bowel obstruction or another severe small bowel abnormality (e.g. metabolic or infectious disease). While the reported prevalence of the sign in small bowel obstruction ...
Regular, smooth generalised thickening
congestive cardiac failure (CCF)
anticoagulation or bleeding diathesis
IgA vasculitis (Henoch-Schonlein purpura)
Small bowel follow through (SBFT) is a fluoroscopic technique designed to obtain high resolution images of the small bowel. The function of the small bowel can also be evaluated.
The small bowel follow through can be used for evaluation of small bowel abnormalities, including:
Small bowel imaging aims at assessment of the disorders of small intestine.
barium follow through