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...
The following points may be helpful to distinguish between sigmoid volvulus and cecal volvulus on plain film.
arises in the pelvis (left lower quadrant)
extends towards the right upper quadrant
ahaustral in appearance
sigmoid volvulus causes obstruction of the proximal larg...
Simple pancreatic cysts, also known as true epithelial cysts or retention cysts, are unilocular cysts within the pancreas, lined by a monolayer of epithelium, which lack communication with the pancreatic ducts 1,5. In contradistinction to other solid viscera, simple cysts in the pancreas are a r...
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 air or CO2.
The single contrast techniqu...
Single contrast upper GI technique is a method of imaging the esophagus, stomach, and duodenum with fluoroscopy. "Single contrast" refers to imaging with barium or water-soluble contrast only, without the addition of effervescent granules.
The single contrast upper GI study may be ...
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.
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 (60-100 mL), thus creating restrictive physiology. The postsurgical gastric pouch resembles a banana-s...
Sleeve gastrectomy complications are often evaluated by imaging. For details about the surgical procedure, please see the parental article on sleeve gastrectomy.
Postoperative complications can be classified by etiology or temporality.
staple line leakage
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:
Although anatomically it is stated that the duodenum forms the...
Small bowel atresia corresponds to malformations where there is a narrowing or absence of a portion of the small bowel, which includes:
Small bowel carcinoid tumors are the most common gastrointestinal carcinoid tumors and most frequently involves the terminal ileum.
Small bowel carcinoid tumors account for ~40% of gastrointestinal carcinoid tumors 1.
Small bowel carcinoids are slow growin...
The small bowel feces 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 i...
Regular, smooth generalized 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 motility of the small bowel can also be grossly evaluated.
The small bowel follow through can be useful for evaluation of:
Small bowel imaging aims at assessment of the disorders of small intestine.
barium follow through
Small bowel or mesenteric ischemia may be a life-threatening condition, arising from any one of numerous causes of disturbance of the normal blood flow through the small bowel wall.
It can be divided into acute and chronic forms, with the main underlying etiologies (each discussed s...
Small bowel lymphoma is one of the most common small bowel malignancies, accounting for ~25% of all primary small bowel malignancies, and ~40% of all primary gastrointestinal lymphomas.
Small bowel lymphoma is most commonly secondary extranodal involvement in widespread systemic l...
The small bowel mesentery is a broad fan-shaped fold of peritoneum connecting the loops of jejunum and ileum to the posterior abdominal wall and is one of the four mesenteries in the abdominal cavity.
It is connected to the posterior abdominal wall by its root which measures about 15 cm and ext...
Small bowel mesentery internal hernias are a form internal bowel herniation, involving protrusions of viscera through defects in the peritoneum or bowel mesentery. This type of internal herniation is more often seen in neonates than in adults.
There are two types:
transmesenteric small bowel i...
Small bowel obstruction (SBO) accounts for 80% of all mechanical intestinal obstruction, the remaining 20% results from large bowel obstruction. It has a mortality rate of ~5%.
Classical presentation is cramping abdominal pain and abdominal distension with nausea and vomi...
This is a basic article for medical students and other non-radiologists
Small bowel obstruction (SBO) accounts for 80% of all mechanical intestinal obstruction; the remaining 20% result from large bowel obstruction. It has a mortality rate of 5.5%.
This is a summary article;...
Soft-tissue sarcomas are a heterogeneous group of malignant tumors of mesenchymal origin (sarcoma) that originate from the soft tissues rather than bone. They are classified on the basis of tissue seen on histology. The commoner sarcomas in the adult and pediatric population are listed below.
The solid abdominal viscera (singular: viscus) is a collective term for those internal organs of the upper abdomen that are primarily solid in nature, namely the liver, pancreas, spleen, adrenals, and kidneys. It is used in contradistinction to the hollow abdominal viscera, which includes, the s...
Solitary rectal ulcer syndrome (SRUS) is a chronic, benign disorder characterized by the presence of an abnormality of the rectum in persons who have a long history of straining during defecation. It is a misnomer because only a third of patients have a solitary ulcer, and many have no ulcers at...
Somatostatinomas are a rare type of neuroendocrine tumor. They may represent around 1% of all gastro-entero-pancreatic endocrine neoplasms.
The presentation can be variable. Patients with functional somatostatinoma may present with an "inhibitory syndrome" which is a tria...
Lymphadenopathy is quite common, and it can be very difficult to differentiate malignant lymphadenopathy from reactive nodal enlargement.
Several gray scale and color Doppler features favor malignancy in a lymph node.
Gray scale parameters that favor malignancy
size: larger-more likely malign...
The sphincter of Oddi (also known as the sphincter of ampulla or choledochal sphincter) is a complex of four smooth muscle sphincters within the duodenal wall. It surrounds, and helps fix to the duodenum, the duct of Wirsung, common bile duct and the ampulla of Vater 1,2.
When relaxed it allow...
Sphincter of Oddi dysfunction is a functional disorder in which stenosis or dyskinesia of the sphincter of Oddi obstructs drainage from the common bile duct.
The disorder is associated with history of cholecystectomy, in which case it is also called postcholecystectomy syndrome. T...
Spigelian-cryptorchidism syndrome is the association of Spigelian hernias and cryptorchidism in children.
It is reported that ~50% (range 28-75%) range of pediatric patients with Spigelian hernias will have ipsilateral cryptorchidism 1,2.
Along with Spigelian hernia and cryptorchi...
Spigelian hernia, also known as lateral ventral hernia, is a type of abdominal hernia along the semilunar line, resulting in herniation between the muscles of the abdominal wall.
They are rare and account for ~1% (range 0.1-2%) of ventral hernias 2,3. The incidence is thought to p...
The spleen is an organ of the hematological system and has a role in immune response, storage of red blood cells and hematopoiesis.
The spleen is a wedge-shaped organ lying mainly in the left upper quadrant (left hypochondrium and partly in the epigastrium) and is protected by th...
The spleen size varies with a child's age.
The three numbers below represent the 10th percentile, median, and 90th percentile for the long axis of the spleen (cm)
0-3 months: (3.3, 4.5, 5.8 cm)
3-6 months: (4.9, 5.3, 6.4 cm)
6-12 months: (5.2, 6.2, 6.8 cm)
1-2 years: (5.4, 6.9, 7.5 cm)
Splenic amyloidosis is rare as an isolated entity. Most often it is associated with either systemic amyloidosis or hepatic amyloidosis.
In general, splenic involvement in amyloidosis is rather frequent (5-10% of cases 6,7).
Symptoms include abdominal mass a...
The splenic artery is one of three branches celiac trunk and supplies the spleen as well as large parts of the stomach and pancreas.
Origin and course
The splenic artery is one of the terminal branches of the celiac trunk, passing from the celiac axis toward the splenic hilum, t...
Splenic artery aneuryms are the commonest visceral arterial aneurysm formation as well as the 3rd commonest abdominal aneurysm (after the aorta and iliac vessels). Aneurysms are usually saccular in configuration and they can either be in the form of a true aneurysm (much more common) or as a pse...
Splenic artery pseudoaneurysms are a rare type of pseudoaneurysm arising from any portion of the splenic artery and its branches.
Unlike splenic artery true aneurysms, splenic artery pseudoaneurysms will nearly always present with symptoms 2. While there occurrence may b...
Brucellosis is a common zoonosis, which is particularly prevalent in Mediterranean countries. It produces a multisystemic illness that can present with a broad spectrum of clinical manifestations and complications 1.
This article is focusing on the splenic involvement by brucellosis. For genera...
Splenic calcifications can occur is various shapes and forms and can occur from a myriad of etiological factors.
The usual calcification observed in radiographs are the multiple, miliary form presenting numerous small rounded densities averaging from three to five millimeters in diameter where ...
Splenic epithelial cysts, also referred as splenic epidermoid cysts or primary splenic cysts, are unilocular fluid lesions with thin and smooth walls and no enhancement. They represent ~20% of cysts found in the spleen, and are usually an innocuous incidental imaging finding.
Note that most (~8...
Splenic hemangiomas, also known as splenic venous malformations, splenic cavernous malformations, or splenic slow flow venous malformations, while being rare lesions, are considered the second commonest focal lesion involving the spleen after simple splenic cysts 5,12 and the most common primary...
Splenic haemangiomatosis involves multiple, diffuse splenic hemangiomas replacing its entire parenchyma. It is a very rare entity.
It can occur as a manifestation of systemic angiomatosis or, less commonly, confined to the spleen (diffuse isolated splenic haemangiomatosis). There is ...
Splenic infarction is a result of ischemia to the spleen, and in many cases requires no treatment. However, identification of the cause of infarction is essential.
Splenic infarcts can occur due to a number of processes, involving either arterial supply, the spleen itself or the...
There are a number of splenic lesions and anomalies:
Benign mass lesions
splenic cyst (mnemonic)
splenic hemangioma: commonest benign spl...
Splenic lymphangiomas are relatively rare benign tumors that correspond to abnormal dilatation of lymphatic channels that can be either congenital or acquired. On imaging, they usually present as lobulated and multiloculated cystic lesions without solid component or significant enhancement.
Splenic peliosis is an unusual benign disorder characterized by the presence of irregular cystic blood-filled cavities.
Most patients are asymptomatic although very rarely patient can present with spontaneous organ rupture.
Recognized associations include
Splenic siderotic nodules, also known as Gamna-Gandy bodies, of the spleen, are most commonly encountered in portal hypertension. The pathophysiological process is the result of microhemorrhage resulting in hemosiderin and calcium deposition followed by fibroblastic reaction.
Splenic trauma can occur after blunt or penetrating trauma or secondary to medical intervention (i.e. iatrogenic). The spleen is the most frequently injured internal organ after blunt trauma.
In blunt trauma, the spleen can account for up to 49% of abdominal organ injuries 2.
The splenic vein drains the spleen, part of the pancreas, and part of the stomach.
Origin and course
The splenic vein is formed by splenic tributaries emerging at the splenic hilum in the splenorenal ligament at the tip of the tail of pancreas. It runs in the splenorenal ligame...
Splenomegaly refers to enlargement of the spleen. The upper limit of normal adult splenic length is traditionally cited at 12 cm, but lengths upwards of 14 cm can be seen in normal, taller males 7.
Massive splenomegaly is variably defined, including when the spleen is 5 standard deviations abov...
Splenorenal ligament, also known as the lienorenal ligament is a peritoneal ligament. It represents the dorsal most part of dorsal mesentery and forms part of the lateral border of the lesser sac. It is continuous with the gastrosplenic and phrenicocolic ligaments 1.
Splenosis is one type of ectopic splenic tissue (the other being accessory spleen). It is an acquired condition and is defined as autoimplantation of one or more focal deposits of splenic tissue in various compartments of the body.
Abdominal splenosis is seen after abdominal trauma or surgery (...
Spontaneous splenic rupture (SSR) (or atraumatic splenic rupture) is rare, especially when compared to traumatic splenic rupture.
The pathogenesis of atraumatic splenic rupture is not well understood. Splenomegaly is present in almost all patients (~95%), although rupture of normal ...
Sprue is the collective term for the malabsorptive gastrointestinal enteropathies although it may be used to refer directly to tropical sprue. It is composed of two entities:
non-tropical sprue / celiac disease
In each, the radiologic features are not sensitive enough to confir...
Stab wounds are a form of penetrating trauma that may be self-inflicted or inflicted by another person either accidentally or intentionally. They may be caused from a variety of objects and may occur anywhere in the body.
Although commonly caused by a knife as well, slash injuries ...
Stack of coins sign refers to the appearance of small bowel folds that are smoothly and uniformly thickened 1. The margins between the folds are sharply delineated and the arrangement of clearly demarcated parallel folds is likened to a stack of coins or a picket fence. This sign is distinct fro...
Stepladder sign may refer to:
intracapsular breast implant rupture (ultrasound)
gas-fluid levels in obstructed small bowel (erect abdominal radiograph)
Stepladder sign represents the appearance of gas-fluid distended small bowel loops that appear to be stacked on top of each other, typically observed on erect abdominal radiographs in the setting of small bowel obstruction.
Stercoral colitis refers to a condition where the presence of impacted feces in the colonic lumen is associated with inflammation and distention of the affected colon segment.
It is seen primarily in elderly patients (often bedbound as a consequence of dementia, stroke, or orthope...
Stercoral perforation is defined as a bowel perforation due to pressure necrosis from a fecal mass (fecaloma) 1. It is an uncommon, but life-threatening, complication of unresolved fecal impaction and can be a cause of acute abdomen secondary to fecal peritonitis.
It may represent...
The Stierlin sign refers to repeated emptying of the cecum, seen radiographically as barium remaining in the terminal part of the ileum and in the transverse colon. This occurs due to irritation of the cecum caused by M. tuberculosis. It is not specific for tuberculosis and can also be seen in C...
The stomach is a muscular organ that lies between the esophagus and duodenum in the upper abdomen. It lies on the left side of the abdominal cavity caudal to the diaphragm at the level of T10.
The stomach ("normal" empty volume 45 mL) is divided into distinct regions:
Stomal ulcers may occur after surgery for peptic ulcer disease, and are more common in settings of a retained gastric antrum or an incomplete vagotomy (occurrences which are not common with modern surgical technique). There is also a higher risk with Zollinger-Ellison syndrome.
Strangulated in the context of hernias refers to an incarcerated hernia in which the hernial opening is so constricted that the arterial supply is compromised, leading to ischemia and eventually gangrene. It is a surgical emergency.
Streak ovaries are a form of ovarian dysgenesis and are associated with Turner syndrome. Occasionally they may be functional and secondary sexual characteristics may develop.
Streak ovaries are seen when there is abnormality or absence of the X chromosome.
The string of beads sign is the description typically given to the appearance of the renal artery in fibromuscular dysplasia (FMD) but may also be used to describe the appearance of splanchnic arteries in segmental arterial mediolysis (SAM). It refers to the appearance arising from the stenoses ...
String of pearls sign can refer to:
string of pearls sign on an abdominal radiograph of fluid-filled dilated small bowel loops
string of pearls sign on ultrasound in polycystic ovarian syndrome
string of pearls sign for angiographic appearances in fibromuscular dysplasia
The string of pearls (or beads) sign can be seen on upright or decubitus abdominal radiographs as well as on CT in patients with small bowel obstruction, increased intraluminal fluid, and slow resorption of intraluminal gas.
It consists of an obliquely or horizontally oriented row of small gas ...
The gastrointestinal string sign (also known as the string sign of Kantor) refers to the string-like appearance of a contrast-filled bowel loop caused by its severe narrowing.
Originally used to describe the reversible narrowing caused by spasms in Crohn disease, it is now used for any severe n...
The string sign may refer to:
angiographic string sign
gastrointestinal string sign
string sign of parosteal osteosarcoma
Stump appendicitis refers to inflammation of the residual appendiceal tissue post appendectomy.
Partial removal of the appendix with a residual stump allows for a chance of recurrent appendicitis. Chances of a partial removal are found to be higher in cases where there is a wrong ide...
Subcapsular splenic hematomas are a type of splenic hematoma that occurs beneath the splenic capsule.
They can occur in both traumatic and non-traumatic situations.
abdominal: splenic trauma 3, a subcapsular hematoma is part of imaging criteria for grades I-III of the ...
Subdiaphragmatic free gas is one of the ways of detecting presence of free intraperitoneal gas (i.e. pneumoperitoneum). It is the presence of free, extraluminal gas in the anterior subhepatic space.
Subdiaphragmatic free gas is well appreciated as the g...
The Sudeck point (or Sudeck critical point) refers to a specific location in the arterial supply of the rectosigmoid junction, namely the origin of the last sigmoid arterial branch from the inferior mesenteric artery (IMA) 1.
This arterial branch usually forms an anstomosis with a branch of th...
The superior mesenteric artery (SMA) is one of the three non-paired major visceral arteries in the abdominal cavity arising from the abdominal aorta and supplying the midgut.
Single vessel arising anteriorly from the abdominal aorta at the level of L1, usually just below ...
There are two distinct vascular compression disorders due to compression of another structure by the superior mesenteric artery. The terminology is sometimes confusing and they can occur in association.
superior mesenteric artery syndrome (Wilkie syndrome): compression of the third part of th...
Superior mesenteric artery (SMA) syndrome, also known as Wilkie syndrome, is a rare acquired vascular compression disorder in which acute angulation of the superior mesenteric artery (SMA) results in compression of the third part of the duodenum, leading to obstruction.
It should not be confuse...
The superior mesenteric vein (SMV) accompanies the superior mesenteric artery (SMA) and drains the midgut to the portal venous system.
Origin and course
Mesenteric venous arcades, which accompany the arteries, unite to form the jejunal and ileal veins in the small bowel mesenter...
Superior mesenteric venous thrombosis can result from number of conditions. It can account for around 5-15% of all mesenteric ischemic events.
It can be classified in various ways:
acute: acute superior mesenteric venous thrombosis
chronic: chronic superior mesenteric venous thrombosis
The superior pancreaticoduodenal artery is a branch of gastroduodenal artery that supplies the duodenum and pancreas.
Superior pancreaticoduodenal artery arises after branching off from gastroduodenal artery. It divides into anterior and posterior divisions which supply the pylor...
The superior rectal artery is an artery that supplies bloods to the rectum down to the level of the levator ani 2.
origin: the terminal branch of the inferior mesenteric artery is the superior rectal artery
course: descends into the pelvic cavity in the sigmoid mesocolon, crossing the...
The supraduodenal artery (SDA) is a branch of the gastroduodenal artery (GDA). It arises soon after the origin of the GDA posterior to the first part of the duodenum and supplies the anterosuperior part of the first and second parts of the duodenum, contributing to the rich arterial anastomotic ...
The supramesocolic space is the peritoneal space above the root of the transverse mesocolon. The inframesocolic space lies below the root of the transverse mesocolon.
It can be arbitrarily divided into right and left supramesocolic spaces and subspaces. These are normally in communication with ...
The supravesical fossae are concave depressions of peritoneum in the paravesical space bounded by the median umbilical fold and the medial umbilical folds. It partially overlies the inguinal (Hesselbach’s) triangle. The supravesical fossae are usually occupied by small bowel loops and the urinar...
Surgical hemostatic material is used to control bleeding intraoperatively and is hence frequently intentionally left in the operative bed, not to be confused with a gossypiboma which is caused by foreign material left behind in error. Its use has increased with the advent of minimally invasive s...
There are various classic surgical positions for patients to be placed in for procedures, which have been adopted/repurposed for interventional radiology and some diagnostic procedures:
reverse Trendelenburg position
lateral decubitus position
Syphilis is the result of infection with the gram negative spirochete Treponema pallidum, subspecies pallidum. It results in a heterogeneous spectrum of disease with many systems that can potentially be involved, which are discussed separately.
Despite the discovery of penicillin...
Systemic lupus erythematosus (SLE) is a complex autoimmune disease with multisystem involvement. Although abnormalities in almost every aspect of the immune system have been found, the key defect is thought to result from a loss of self-tolerance to auto-antigens.
There is a stron...
Gastrointestinal manifestations in patients with systemic lupus erythematosus are common and may involve any region of the gastrointestinal tract or visceral organs.
Patients with abdominal or gastrointestinal involvement by systemic lupus erythematosus may have a variety...
The taeniae coli are the three outer muscular bands of the colon. They sit on top of the inner circumferential layer and result in the classical appearance of the colon: the haustral markings are interrupted unlike the valvulae conniventes within the small bowel.
Tailgut duplication cysts, also known as retrorectal cystic hamartomas, are rare congenital lesions that are thought to arise from vestiges of the embryonic hindgut.
There is a recognized strong female predilection. While it can present at any age, presentation is usually at arou...