Peritoneal hydatidosis occurs secondary to seeding of echinococcosis to the peritoneum, usually secondary to rupture of hydatid disease of liver.
Seeding involves the entire peritoneum and gives appearance of an multiloculated mass.
Peritoneal hydatidosis can be pri...
The peritoneal ligaments are double layers of peritoneum that pass from one organ to another or from an organ to one of the abdominal walls.
Suspensory ligaments of the liver
right triangular ligament
left triangular ligament
Peritoneal ligaments of the stomach
Peritoneal mesothelioma is an uncommon primary tumour 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 subtypes (also discussed separately...
Peritoneal metastases, which if of epithelial origin, as most are, and extensive are also known as peritoneal carcinomatosis, are relatively common particularly in tumours of the abdomen and pelvis and generally imply a poor prognosis, often with a significant impact on palliation 1. Less common...
Peritoneal spaces are separate compartments within the peritoneal cavity. These spaces are separated or compartmentalized by various peritoneal ligaments and their attachments.
The peritoneal spaces are important in the peritoneal diseases, ascites, intraperitoneal collections or peritoneal me...
The peritoneum is a large complex serous membrane which forms a closed sac within the abdominal cavity. In the female, this closed sac is perforated by the lateral ends of the fallopian tubes. It is a potential space between the parietal peritoneum lining the abdominal wall and the visceral peri...
Perivascular epithelioid cells tumours (PEComas) are a group of related mesenchymal tumours and tumour-like conditions found in many locations. This group includes:
clear cell 'sugar' tumour of the lung
clear cell myomelanocytic tumour (CCM...
Per-oral oesophageal myotomy (POEM) is a natural orifice endoscopic surgery that has been gaining increasing use as an alternative to traditional oesophageal myotomies (e.g. Heller myotomy and Nissen fundoplication).
With this technique, the endoscopist insufflates the oesophagus with CO2 then ...
Peroral pneumocolon is a technique that can be used during a small bowel follow through (SBFT) to better visualize the ascending colon and terminal ileum.
The goal of a peroral pneumocolon is to create a double contrast study (oral contrast and gas) of the ascending colon and termina...
PET-CT is a combination of cross-sectional anatomic information provided by CT and the metabolic information provided by positron emission tomography (PET).
PET is most commonly performed with 2-[F-18]fluoro-2-deoxy-D-glucose (FDG). Fluorine-18 (F-18) is an unstable radioisotope and has a half-...
Petersen hernias are internal hernias which occur in the potential space posterior to a gastrojejunostomy. This hernia is caused by the herniation of intestinal loops through the defect between the small bowel limbs, the transverse mesocolon and the retroperitoneum, after any type of gastrojejun...
Peutz-Jeghers syndrome is one of the polyposis syndromes. It has an autosomal dominant inheritance and is characterised by:
multiple hamartomatous polyps, most commonly involving the small intestine (predominantly the ileum), but also colon and stomach; mouth and oesophagus are spared
The phrenic ampulla (also known as the oesophageal vestibule) is the region between the A-ring and B-ring of the distal oesophagus.
The gastro-oesophageal junction is below the ampulla (and gastric folds should not enter the region of the ampulla).
The ampulla is more ...
Plummer-Vinson syndrome, also known as the Paterson-Brown-Kelly syndrome, predisposes to hypopharyngeal squamous cell carcinoma and consists of four features:
oesophageal webs or hypopharyngeal webs
The condition is more common in women.
Pneumatosis coli is a descriptive sign presenting radiographically as intramural gas limited to the colonic wall.
There are different terminologies in the medical literature, such as pneumatosis intestinalis, pneumatosis coli, and pneumatosis cystoides intestinalis. Pneumatosis in...
A helpful mnemonic for remembering the causes of pneumatosis intestinalis is:
C: chronic obstructive pulmonary disease
P: pneumatosis cystoides intestinalis
Pneumoperitoneum describes gas within the peritoneal cavity, and is often the harbinger of a critical illness. There are numerous causes and several mimics (see article: pseudopneumoperitoneum).
The most common cause of pneumoperitoneum is from the disruption of the wall of a hollow ...
This is a basic article for medical students and other non-radiologists
Pneumoperitoneum describes gas within the peritoneal cavity and is often the harbinger of a critical illness, often perforation of a hollow viscus. Pneumoperitoneum is distinct from pneumoretroperitoneum (much rarer) and ma...
Pneumoretroperitoneum is by definition presence of gas within the retroperitoneal space.
Pneumoretroperitoneum is always abnormal and has a relatively small differential:
perforated retroperitoneal hollow viscus
peptic ulcer disease
blunt or penetrating abdominal trauma
The Polo Mint sign is a description given to a venous thrombosis on contrast-enhanced CT imaging. When viewed in the axial plane, a thin rim of contrast persists around a central filling defect due to thrombus. This gives an appearance like that of the popular UK mint sweet, the Polo, also refe...
Polyarteritis nodosa (PAN) is a systemic inflammatory necrotising vasculitis that involves small to medium sized arteries (larger than arterioles).
Polyarteritis nodosa (PAN) is commoner in males and typically presents around the 5th to 7th decades. Twenty to thirty percent of p...
Polyglandular autoimmune syndromes (PAS) are a rare set of diseases characterised by the presence of ≥2 autoimmune endocrine disease.
Three types of PAS have been described.
PAS type I
a.k.a. APECED (autoimmune polyendocrinopathy, candidiasis and ectodermal dystrophy) or MEDAC (mu...
The polyposis syndromes are disorders in which more than 100 gastrointestinal polyps are present throughout the GI tract:
hereditary nonpolyposis colorectal cancer
familial adenomatous polyposis syndrome (FAPS)
Polysplenia syndrome, also known as left isomerism, is a type of heterotaxy syndrome where there are multiple spleens congenitally as part of left-sided isomerism.
Polysplenia is seen predominantly in female patients. It is usually diagnosed in childhood or adulthood, later than a...
In portal hypertension, chronic portal venous congestion leads to dilatation and ectasia of the submucosal vessels in the stomach (portal hypertensive gastropathy), small bowel (portal hypertensive enteropathy) and/or large bowel (portal hypertensive colopathy). This may result in upper or lower...
Portal vein calcification is a rare radiologic finding which can be seen in long-standing portal venous hypertension.
Calcium may be deposited in a thrombus or in the wall of the portal vein and is more rarely found in the splenic vein and superior mesenteric vein.
One of the propos...
Portal venous gas is the accumulation of gas in the portal vein and its branches. It needs to be distinguished from pneumobilia, although this is usually not too problematic, when associated findings are taken into account along with the pattern of gas (i.e. peripheral in portal venous gas, cent...
The portal venous system refers to the vessels involved in the drainage of the capillary beds of the GI tract and spleen into the capillary bed of the liver.
Blood flow to the liver is unique in that it receives both oxygenated and deoxygenated blood. As a result, the partial pressure of oxygen...
Portosystemic collateral pathways (also called varices) develop spontaneously via dilatation of pre-existing anastomoses between the portal and systemic venous systems. This facilitates shunting of blood away from the liver into the systemic venous system in portal hypertension, as a means for r...
The portosystemic shunt ratio is a measure performed using ultrasound to quantify the abnormal flow of portal venous blood that is shunted away from the hepatic sinusoidal circulation in the context of a congenital portosystemic shunt 1.
The ratio is determined using the following e...
The posterior pararenal space is the smallest and most clinically insignificant portion of the retroperitoneum.
It is filled with fat, blood vessels and lymphatics, but contains no major organs.
posteriorly: bound by transversalis fascia
anteriorly: bound by posteri...
Postoperative free intraperitoneal gas refers to the presence of gas in the peritoneal cavity following a surgical procedure and may result from open or laparoscopic surgical techniques.
Postoperative free intraperitoneal gas is also referred to as postoperative pneumoperitoneum...
Post-transplant lymphoproliferative disorder (PTLD), also referred as post-transplant lymphoproliferation disorder, represents a variety of conditions ranging from lymphoid hyperplasia to malignancy, included in the 2008 WHO classification of tumours of haematopoietic and lymphoid tissues. It ca...
PPP syndrome is the extremely rare association of pancreatitis, panniculitis, and polyarthritis.
Most commonly affects middle-aged male patients with a history of heavy alcohol use 1,2.
In the majority of cases, abdominal symptoms are mild or absent, makin...
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...
Pseudopneumoretroperitoneum is the radiographic finding of gas within the abdominal region that mimics the appearance of pneumoretroperitoneum (cf. the analogous pseudopneumoperitoneum i.e. abdominal gas that erroneously suggests pneumoperitoneum).
Causes of pseudopneumoretroperitoneum include...
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, with an incidence of approximately 2-5 per 1,000 births, and has a male pred...
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.
For discussion of other gastrointestinal foreign bodies, please see: bezoars.
The patient u...
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. MRI is the modality of choice for the staging of rectal cancer, to guide surgical and non-surgical management options. MRI is used at diagnosis, following downstaging chemoradiotherapy, and...
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 ...
Rectocele refers to a herniation or bulge of the rectal wall, with the most common type being an anterior rectocele 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 colorectal...
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 ratio >1). In fact...
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 anorectal angle created by puborectalis.
At the level of the S3 vertebral body,...
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.
For a general discussion, and for links to other system specific manifestations, please refer to the article on hydatid disease.
It is generally seen secondary to ...
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 is an international multidisciplinary classification of the severity of acute pancreatitis, updating the 1992 Atlanta classification. It was initially revised in 2012 and then further updated in 2016 6.
The worldwide consensus aims for an...
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 subhepatic space, or hepatorenal pouch, lies between the upper pole of the right kidney and the inferior surface of the right lobe of the liver.
This is a subcompartment of the supracolic compartment. The space can be further subdivided in to two other spaces by its re...
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 right supramesocolic space is an arbitrary subdivision of the supramesocolic space, which lies between the diaphragm and the transverse colon.
The right supramesocolic space is separated from the left supramesocolic space by the falciform ligament, and can be divided into thr...
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, recent instru...
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)
Ruptured omphalocoele occurs when there is rupture of the outer membrane of an omphalocoele. When this happens the eviscerated fetal bowel looks free floating and distinction from gastroschisis becomes difficult. However the abdominal defect generally tends to be larger and may contain liver wit...
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...