Gastrointestinal Imaging

Accordion sign	• Contrast between thickened folds (accordion sign) Pseudomembranous colitis (PMC)
Bull's eye pattern (hypoechoic halo around lesion)	LIVER US FOR METASTASIS Echogenic metastases • GI malignancy • HCC • Vascular metastases Hypoechoic metastases • Most metastases are hypovascular. • Lymphoma • Bull's eye pattern (hypoechoic halo around lesion) Nonspecific sign but frequently seen in bronchogenic carcinoma Hypoechoic rim represents compressed liver tissue and tumor fibrosis. Calcified metastases: hyperechoic with distal shadowing • All mucinous metastases: colon > thyroid, ovary, kidney, stomach Cystic metastases: necrotic leiomyosarcoma; mucinous metastases
Carman's (meniscus) sign*	*Results from the fluoroscopically induced apposition of rolled halves of the tumor margin forming the periphery of the ulcerated carcinoma; meniscus refers to meniscoid shape of ulcer. Malignant Peptic Ulcer
Central dot sign	The “central dot sign” is a very specific sign of Caroli disease in which portal radicals are partially or completely surrounded by abnormally dilated and ectatic bile ducts on both sonography and CT.
Colon cutoff sign	Barium: colon cutoff sign acute pancreatitis
Comb sign	• Comb sign: vasa recta stretched out along one wall of colon Crohn disease (regional enteritis)
Courvoisier's sign	Courvoisier's sign (enlarged, nontender GB), 25% Adenocarcinoma (PDAC) of pancreas
Crohn-Stierlin sign like deep ulcers of Infectious Colitis	Campylobacter SU, DU Usually in distal colon Amebiasis SU, DU Diffuse but most severe in right colon (ameboma); small bowel rarely affected Tuberculosis DU Loss of demarcation between cecum and terminal ileum (Stierlin sign); lymph nodes Lymphogranuloma venereum DU Rectal strictures typical Yersinia DU Typically terminal ileum, cecum
CT Bowel Target Sign	• Ischemia • Vasculitis • Hemorrhage • Inflammatory bowel disease • Angioedema: ACEi, hereditary, allergic reaction • Portal hypertension • NSAIDs
CT Bowel Target Sign	CT Bowel Target Sign • Ischemia • Vasculitis • Hemorrhage • Inflammatory bowel disease • Angioedema: ACEi, hereditary, allergic reaction • Portal hypertension • NSAIDs
Cullen's sign	Periumbilical ecchymosis (Cullen's sign)
Cystic fibrosis	AP radiograph in a newborn with cystic fibrosis shows numerous dilated bowel loops typical of a low intestinal obstruction. A bubbly appearance is noted in left lower quadrant bowel loops  related to gas mixing with meconium. PA water-soluble contrast enema ishows a mildly small sigmoid and descending colon with transition at the splenic flexure to a normal proximal colonic caliber. Note the numerous meconium plugs in the proximal colon.
Dilatation of smaller venous branches (>5 mm) of pancreas	Dilatation of smaller venous branches (>5 mm): an indirect sign of venous encasement
Double duct sign	Ductal obstruction in pancreatic adenocarcinoma • Pancreatic duct obstruction; pseudocysts are rare. • Common bile duct obstruction with pancreatic duct obstruction (double duct sign: also seen with pancreatitis) • Tumors in the uncinate process may not cause ductal obstruction. Double-duct sign: dilated biliary vessel accompanies portal veins.
Double-duct sign: dilated biliary vessel accompanies portal veins.	Ultrasound Signs of Intrahepatic Bile Duct Dilatation Double-duct sign: dilated biliary vessel accompanies portal veins.
Double-rim sign	• Double-rim sign: pericyst, endocyst Echinococcus (hydatid disease)
Double-target sign	• Double-target sign: wall enhancement with surrounding hypodense zone (edema) 30% contain gas Pyogenic abscess
Duodenal Wind Sock Sign	Duodenal wind sock sign in a patient with duodenal diverticulum. Image from an upper gastrointestinal series clearly demonstrates an intraluminal duodenal diverticulum (arrows) surrounded by a narrow radiolucent line (arrowheads). The diverticulum, arising in the second portion of the duodenum and extending to the third portion, was confirmed at surgery.
Fleischner's sign	• Marked hypertrophy: ileocecal valve (Fleischner's sign) Intestinal tuberculosis (TB) • TB: narrow cecum (Fleischner's sign), narrow Crohn's may produce same appearance, terminal ileum (Stierlin's sign)
Focal liver lesions	cystic lesions
Focal liver lesions	hypervascular liver lesions I: Hemangioma: female predominance, hepatic artery vascular supply, peripheral nodular globular interupted enhancement with progressive centripital fill-in, large lesions can demonstrate a central scar or calcification, unencapsulated. Typical type hemangioma and Giant type hemangioma >5cm Focal Nodular Hyperplasia: young female, composed of varying degrees of hepatocytes, bile ducts and Kuppfer cells - will take up Tc-99m Sulfer Colloid, - will take up Eovist on delayed hepatic phase Multiple in 1/4 of cases Blood supply entirely from the hepatic artery (like hemangioma) - seen as a hypertrophied feeding vessel to the mass but no internal hypervascularity, homogeneously hypervascular (to IVC level enhancement) - no internal neovascularity of tumor vessels (cf adenomas or HCC) - Stelth lesions (cant find them on venous fase) -flower morphology - well circumscribed homogenous (cf HCC) - hypertrophied feeding vessel to center (without substantial neovascularity) Oftern invisible in the venous phase 50%deonstarate central scar (esp. when large) -scar can enhance on delayed images No capsule Hepatic Adenoma: female predominance; highly associated with Oral Contraceptive Pill use, steroids, steatosis, and glycogen storage disease; can present with hemorrhage in 20%; Primarily composed of hepatocytes and Kuppfer cells (no bile duct component so wont take up Eovist); Hepatic "adenomatosis" without OCP use; Malignant degeneration to HCC is rare.  Hepatic artery vascular supply; heterogeneously hypervascular on the arterial phase - fat - hemorrhage; variable appearance on the venous phase and delayed images (washout/isodense/hypodense); oftern encapsulated on venous and delayed images; can have a central scar - underlying history is critical, uable to distinguish from HCC or hypervascular metastasis without a specific history
Focal liver lesions	Solid liver masses I : Metastases: hypovascular and hypervascular; cholangiocarcinoma; lymphoma; epitheliod hemangioendothelioma liver metastases is the most common site of solid organ metastases; most common hepatic metastases are hypovascular; most common lesions colon, lung, breast, pancreas, neuroendocrine, melanoma, stomach; 50% of colorectal carcinoma  patientspet, or biopsy; dont assume these lesions are benign Approach to small hepatic hypodensities: When dealing with a lesion that is >15mm in  size should be able to distinguish benign from malignant lesions; these lesions may need further characterised with MRI, PET, or biopsy; dont assume lesions are benign. In a patient WITHOUT an underlying malignancy, <15mm 100="" ajr="" are="" as="" benign="" br="" follow="" is="" lesion="" mri="" necessary.="" no="" ones="" or="" report="" up=""> In a patient with known malignancy, only 12.7% are malignant, 80% remain benign (Schwarts). Dont overcall small lesions, pay attention to lesion morphology, look for hypervascularity at the rim of the lesion / surrounding lesions, solid component, nodularity, or perilesional edema; worry more about multiple lesions; follow lesions over time if they are truly "too small to characterise" Hypervascular metastasis: "MR CT PET" Melanoma, Renal cell carcinoma, Choriocarcinoma, Thyroid cancer, PET-Pancreatic + Neuroendocrine Tumour; use MIP images to identify subtle lesions. Require Arterial phase images, good indication for MIP imaging, Cholangiocarcinoma;
Focal liver lesions	hypervascular liver lesions II: Hepatocellular Carcinoma: 3rd leading cause of death worldwide; strong male predilection; Risk factors Hepatitis B and C, Cirrhosis, Fatty Liver; Management options - surgery, chemoembolisation, transplant MDCT sensitivity for HCC is >90%; Sensitivity for lesions <2cm -="" br="" diffuse="" false="" for="" increase="" lesions="" multifocal="" patterns="" positives="" small="" solitary="" three=""> Hypervascular in the arterial phase, homogeneous for lesions <3cm a="" br="" can="" capsule="" central="" delayed="" encapsulated="" enhancement="" fat="" have="" hemorrhage="" images="" in="" internal="" of="" on="" or="" phase="" scar="" the="" venous="" washout="" with=""> Protocol: arterial phase is critical - late arterial (30 to 35 seconds) preferred; delayed images may be useful - 14 % of HCC only seen on delayed images, typically well differenciated HCC's HCC Criteria for liver transplant Milan Criteria: Single lesion <5cm 3="" 3cm="" br="" disease="" invasion="" lesions="" liver="" metastatic="" no="" outside="" smaller="" the="" then="" vascular=""> UCSF Criteria: Single lesion les then 6.5cm; 3 lesions smaller then 4.5cm; No vascular lesions invasion; No metastatic disease outside the liver Fibrolamellar HCC: Young patient without hx of cirrhosis; theoretically less aggressive; large, lobulated aggressive looking; hypervascular with delayed washout, encapsulated, central scar Ca++; adenopathy common Vascular Shunts: do not confuse perfusion abnormalities with HCC, peripheral; wedge shaped; central vessel sign; increasingly common with cirrhosis. Be caucious in dealing with small hypervascular foci <6mm 3-6="" be="" followed="" for="" in="" increase="" months="" represent="" say="" should="" shunts="" size="" small="" statistically="" td="" that="" vascular="">
Focal liver lesions	Solid liver masses II : Cholangiocarcinoma: tumor arising from the bile duct epithelium; 95% adenocarcinoma; Associated PSC, choledochal cysts, drug exposures (such as thoratrast), congenital hepatic fibrosis, viral hepatitis 3 forms of cholangiocarcinoma: Intrahepatic: mass forming intrahepatic cholangiocarcinoma; periductal infiltrating cholangiocarcinoma - segmental or lobar enhancing tissue in liver intraductal cholangiocarcinoma: ductal lumen Hilar Colangiocarcinoma arise from the confluence: Extrahepatic cholangiocarcinoma that arise from common bile duct: Variable appearance, peripheral hypervascularity on arterial phase images (and sometimes venous phase), hypovascular lesions, avid delayed enhancement, dilaed bile ducts (with bile thickening) in a lobar or segmental distribution, capsular retraction, lobar or segmental atrophy Hepatic lymphoma: primary lymphoma is rare; usually secondary lymphoma involvement; poorly enhancing solid or multiple masses; look for lymphadenopathy. Look for abdominal lymphadenopathy, splaying of vessels instead of coming together of vessels Epitheliod Hemangioendothelioma: Multiple hypodense lesions at the periphery; confluent lesions; capsular retaraction; peripheral enhancement with "ring or target" morphology
Grey Turner's sign	GI hemorrhage, metabolic abnormalities, flank ecchymosis (Grey Turner's sign)
Halo sign	Mural and Extramural Changes (CT Findings) • Circumferential submucosal low attenuation surrounded by higher outer attenuation: halo sign Crohn disease (regional enteritis)
Hampton's line: 1- to 2-mm lucent line around the ulcer†	†This line is caused by thin mucosa overhanging the crater mouth seen in tangent; it is a reliable sign of a benign ulcer, but present in very few patients.
Hirschsprung Disease (HD)	Hirschsprung Disease (HD) Anteroposterior fluoroscopic spot radiograph scout in an infant with infrequent stooling shows moderate to large stool load without other specific abnormality. The bones appear normal. AP radiograph shows multiple dilated loops of bowel throughout abdomen, most consistent with a distal bowel obstruction. There are no calcifications, free air, pneumatosis, or soft tissue masses. AP contrast enema shows the catheter has been removed. There is less spasm, but there is still a small rectum. RS ratio < 1.  The initially distended lateral view of the colon to the splenic flexure is the key view for a well-performed enema. Lateral contrast enema shows a narrow rectum with transition to the dilated colon at the rectosigmoid junction consistent with Hirschsprung disease. Note the spasm in the distal segment. Lateral contrast enema shows borderline RS ratio, meconium within the small left colon, and a transition zone at the splenic flexure (black open), suggesting MPS. Symptoms did not improve, and biopsy was performed in this pathologically proven HD. Often presents at birth with distal bowel obstruction Contrast enema primary findings Rectosigmoid ratio < 1 Transition most commonly sigmoid Transition often missed if at anorectal verge; enema misinterpreted as normal Other supporting CE findings Distal colonic spasm Colitis Irregular contractions Mucosal irregularity Delayed evacuation Total colonic Hirschsprung Small colon without transition ± intraluminal terminal ileal calcification Higher incidence in Down syndrome, especially total colonic disease Radiologic transition not equivalent to histologic transition, especially in long-segment HD
light bulb sign of a hypervascular lesion—and its feeding vessel	Fibrous nodular hyperplasia: enhancement after intravenous administration of a microbubble contrast agent.
Lightbulb sign	• Hyperintense (similar to CSF) on heavily T2W sequences (lightbulb sign) Hemangioma
Liver overlap sign	• Liver overlap sign: overlaps lower margin of liver Volvulus
Meconium Ileus	Meconium Ileus: microcolon; obstruction is usually in the terminal ileum; associated with cystic fibrosis AP radiograph in a newborn with bilious emesis shows a paucity of bowel gas centrally with displacement of gas-containing bowel to the left abdomen, suggestive of a central mass or fluid collection. No free air or air fluid levels; no calcifications to suggest perforation. AP radiograph in a newborn with failure to pass meconium shows numerous dilated bowel loops, typical of a distal obstruction. While the size and location of some of the loops could suggest colon, these loops were all dilated small bowel. Lateral radiograph in a neonate shows no free air or air fluid levels but does show dilated loops of bowel, suggestive of distal bowel obstruction. No calcifications to suggest perforation are seen. PA contrast enema shows a microcolon. Contrast refluxing into the terminal ileum outlines meconium pellets, typical of meconium ileus, seen with distal ileal fillings defects. Contrast could not be refluxed further into the proximal dilated small bowel. Anteroposterior contrast enema shows microcolon with terminal ileum filled with meconium plug and pellets like "pearls on a string", consistent with meconium ileus. Longitudinal ultrasound shows multiple meconium-filled dilated small bowel loops with wall-thickening. Mild ascites is noted. Transverse ultrasound shows a dilated, meconium-filled bowel loop with wall thickening. The constellation of findings is consistent with a complicated meconium ileus, and a superimposed segmental volvulus was found at surgery. Cystic fibrosis testing was positive. Sagittal ultrasound shows a dilated bowel loop in the right abdomen with wall thickening and meconium impaction. Mild ascites is noted. A contrasted enema subsequently showed a microcolon. Necrotic small bowel was surgically resected in this complicated meconium ileus. Surgery is required for simple meconium ileus from CF Complications: Perforation = AP Radiograph: Several calcifications are seen in the right upper quadrant; This patient had an in utero bowel perforation due to meconium ileus in CF. Perforation is likely due to ischemic loop of bowel. Goal of therapeutic enema - prone patient; contrast in the dilated loops proximal to the terminal ileal obstruction
Meconium Plug Syndrome (cf Muconium Ileus) MPS aka small left colon syndrome	The patient's mother had diabetes mellitus.  Infant whose mother was treated for preeclampsia with magnesium sulfate. Baby with ?cystic fibrosis; bilious emesis, premature infants AP Radiograph: shows generalized gaseous distention of small bowel loops and proximal colon (though it is often not possible to differenciate small and large bowel in the neonate) with no rectal gas. Ascending and transverse colon filled with meconium. No free air or abnormal calcifications to suggest complication. PA contrast enema shows a normal rectal caliber with decreased size of the sigmoid and descending colon. There is a normal caliber transverse colon. Note the unopacified dilated proximal small bowel loops. Contrast enema may outline a meconium cast, multiple fillings defects are present A normal rectosigmoid ratio, small left colon, and a transition zone to dilated colon at the level of the splenic flexure. PA contrast enema better shows the transition point at the splenic flexure (cf with Hirshprug Disease). The colonic function (motility) recovers following this study, with resoloution of emesis and intestinal obstrction, is typical of meconium plug syndrome. Lateral contrast enema: in a newborn with bilious emesis shows a normal rectal caliber with small sigmoid colon. Shows small left colon with abrupt transition zone to dilated bowel at the splenic flexure.  Meconium is seen in the distal colon. US: dilated small bowel llops; right colon is filled with meconium; alternating normal and reversed peristalsis or abscence of peristalsis. Rectal biopsy showed normal ganglion cells. CT: not required Differential diagnosis: Meconium Ileus: microcolon; obstruction is usually in the terminal ileum; associated with cystic fibrosis Hirschprung disease: typical segmental rectosigmoid stenosis; abrupt change in diameter of the colon with dilated proximal colon Ileal atresia: microcolon; small bowel loops distal to the atresia are narrowed
Meconium Plug Syndrome (cf Muconium Ileus) MPS aka small left colon syndrome	Digital rectal examination must be performed prior to the prior to contrast enema to exclude anorectla malformation.
Meniscus sign (ERCP, CT)	Extrahepatic biliary dilatation - Lithiasis-related disease
Moulage sign	Hypersecretion and mucosal atrophy cause the moulage sign (rare). Malabsorption
Negative Murphy's sign	• Gangrenous cholecystitis: rupture of GB; mortality, 20% gangrene causes nerve death so that 65% of patients have a negative Murphy's sign.
Neonatal Distal Bowel Obstruction	Findings of contrast enema (CE) limit differential diagnosis: Colonic vs. small bowel process Antenatal or prenatal midgut volvulus late in natural history (ischemia); ileus can mimic distal bowel obstruction Hirschsprung disease more common in patients with Down syndrome Consider meconium ileus if family history of cystic fibrosis Meconium plug syndrome associated with maternal Mg++ therapy, maternal diabetes No rectal opening in male or single perineal opening in female patient with ARM Abdominal radiographs: Many dilated bowel loops ± air-fluid levels If dilated bowel loops but no air-fluid levels, suspect meconium ileus If CE and upper GI (UGI) normal in face of obstruction, consider omphalomesenteric duct remnant anomaly
Northern exposure sign	Northern exposure sign: dilated twisted sigmoid colon projects above transverse colon Volvulus
Obliteration of fat around celiac axis or SMA	Extrapancreatic extension • Most commonly retropancreatic (obliteration of fat around celiac axis or SMA one sign of incurability)
Omega sign	Omega sign: asymmetric wall involvement results in contracture and C-shaped loop on small bowel series Crohn disease (regional enteritis)
Pancreatitis causes identifiable on CT scan	Gallstone pancreatitis: if gall stones present, look at CBD and ampulla, Autoimmune Pancreatitis: - Chronic inflammatory pancreatitis = mixed inflammatory infiltrate; Rare 2%; Minimal abdominal pain; weight loss, recent-onset DM; Elevated IgG4; Respond to steroids - Diffuse enlargement of the pancreas (rarely focal); diffuse or segmental narrowing of the pancreatic duct; Minimal peripancreatic stranding; Low attenuation capsule like rim - may show delayed enhancement; Strictures of the CBD  - thickening and enhancement - Extrapancreatic findings: retropancreatic findings; retroperitoneal fibrosis; salivary gland enlargement; renal involvement = renal infarcts or discreat renal parenchymal lesions; Lung disease (reticular nodules or ground-glass); mediastinal adenopathy Pancreatic Malignancy: - not always so easy; may require follow up; Pancreatic cancer can cause pancreatitis 5%; ductal obstruction is rare in pancreatitis; Pancreatitis infiltrates anteriorly; pancreatic cancer infiltrates posteriorly No identifiable: alcoholism, hypercholestrolism etc APPROACH TO Pancreatitis Identify causes of pancreatitis on CT; Determine severity and prognosis; evaluate for complications of necrosis, fluid collections and vacular complications; Use the correct revised Atlanta classification and nomanclature;  Guide therapy
Pancreatitis veneous and arterial complications	Veneous thrombosis: - Splenic vein thrombosis: intimal injury secondary to adjacent inflammation; Mass effect and compression of vein - SMV and portal vein thrombosis less common - Look for varices: Omental and gastroepiploic So look at the Central Veins SMV in axial and coronal plains; serching for varicies Psudoaneurysms: Pancreatic enzymes weaken arterial wall; most common sites: - splenic artery 40%; GDA 30%; pancreaticoduodenal arcade 20%; Gastric 5%; Hepatic 2% Arterial phase is critical Mortality is >90% if psudoaneurysm ruptures So use MIP imaging to hunt down the psedoaneurysms
Peripheral washout sign	Peripheral washout sign (when seen) is characteristic of metastases.
Positive Murphy's sign	Positive Murphy's sign (sensitivity, 60%; specificity, 90%) Acute cholecystitis Xanthogranulomatous cholecystitis
Ram's horn sign	Ram's horn sign: loss of antral fornices with progressive narrowing from antrum to pylorus Crohn disease (regional enteritis)
Ring or halo sign	Thick folds without malabsorption pattern (edema, tumor hemorrhage) (Fig. 3-107, A and B) Criteria: folds >3 mm. By CT, the edema in small bowel wall may appear as ring or halo sign. Two types: • Diffuse: uniformly thickened folds • Focal: nodular thickening (“pinky printing”), analogous to “thumbprinting” in ischemic colitis, stack-of-coins appearance, picket fence appearance. Causes Submucosal edema • Ischemia • Enteritis Infectious Radiation • Hypoproteinemia • Graft-versus-host reaction Submucosal tumor • Lymphoma, leukemia • Infiltrating carcinoid causing venous stasis Submucosal hemorrhage • Henoch-Schönlein disease • Hemolytic-uremic syndrome • Coagulopathies (e.g., hemophilia, vitamin K, anticoagulants) • Thrombocytopenia, disseminated intravascular coagulation Nodules • Mastocytosis • Lymphoid hyperplasia • Lymphoma • Metastases • Polyps • Crohn disease Small Bowel Stack of Coins Appearance • Anticoagulation • Vasculitis • Trauma • Ischemia • Carcinoid Small Bowel Luminal Narrowing • Ischemia • Vasculitis • Hemorrhage • Radiation • Collagen vascular disease • Inflammatory bowel disease • Tumor • Adhesions CT Bowel Target Sign • Ischemia • Vasculitis • Hemorrhage • Inflammatory bowel disease • Angioedema: ACEi, hereditary, allergic reaction • Portal hypertension • NSAIDs Gracile Small Bowel Tubular “toothpaste” appearance on small bowel series • Graft-versus-host disease • Cryptosporidium
Sentinel clot sign	SPLEEN Blood clot is of high CT density and often located near source of bleeding: sentinel clot sign.
Small Bowel Imaging	Use 1L as a contrast agent (neutral contrast agent); inexpensive and well tolerated; allows good visulaisation of the enhancing bowel wall; does not interfere with 3D imaging. Disadvantages: empties quickly; not optimal distension of the distal small bowel Evaluation of mesenteric vessels use .75mm, but for abdominal organs use 5mm Arterial and venous phase 120CC of non-ionic contrast, Arteries: Celiac Axis - supplies lower esophagus to the descending duodenum.  Hepatic,splenic and left gastric branches. gastroduodenal artery is usually the first branch of teh common hepatic artery and provides an important collateral pathway between the celiac axis and the SMA SMA: supplies the midgut - 3rd and 4th portions of the duodenum , jejunum, ileum, right colon, transverse colon ro splenic flexure; inportant collateral pathways between the SMA and IMA - Marginal artery of Drummond, Arc of Riolan IMA: supplies colon from the splenic fexure to the rectum - left colic, marginal, sigmoid, superior hemorrhoidals; Important collateral pathways - Lumbar branches to abdominal aorta , sacral artery, and internal iliac arteries Use Saggital projection for evaluating mesenteric vessels; Anatomical varients: Celiac Axis and the SMA arise from a common trunk from the aorta Median arcuate ligament syndrome: inferior crura from the diaphragm is low and causes compression and stenosis of the celiac trunk Veins: Portal vein - superior mesenteric vein and the inferior mesenteric vein (splenic vein )
Sonographic Murphy's sign	Acalculous cholecystitis on US • No calculi • Sludge and debris • Usually in critically ill patients • Same findings as in calculous cholecystitis: Sonographic Murphy's sign GB wall thickening (>2 mm) Pericholecystic fluid May occur in absence of any of the above findings
Stierlin sign	Loss of demarcation between cecum and terminal ileum (Stierlin sign); • Narrowed terminal ileum (Stierlin sign) Infectious colitis - Intestinal tuberculosis (TB) Deep Ulceration
String sign	String sign: tubular narrowing of intestinal lumen (edema, spasm, scarring depending on chronicity) Crohn disease (regional enteritis) Crohn disease: aphthous ulcers → linear fissures → nodules → cobblestone → stricture, spasm (string sign), fistula
T2 lightbulb sign (lesion has CSF intensity)	T2 lightbulb sign (lesion has CSF intensity) Hemangioma Cysts Cystic metastases Cystadenocarcinoma
Target sign	Chemotherapy-induced enteropathy appears as nonspecific focal or diffuse bowel wall thickening with or without the target sign or as regional mesenteric vascular engorgement and haziness, more often in distal small bowel. Drug chemotherapy-induced enteritis
Target sign	Mural and Extramural Changes (CT Findings) • Inner and outer layers surrounding low-attenuation middle layer: target sign; middle layer of fat density; chronic, middle layer of water density Crohn disease (regional enteritis)
Target Sign	The target sign of thickened bowel wall on contrast-enhanced CT scans of the abdomen consists of three layers that comprise contrast-enhanced inner and outer layers of high attenuation between which a layer of decreased attenuation can be seen. The target sign is seen with various diseases of the bowel in which submucosal edema, inflammation, or both are present. The inner and outer layers of the target sign represent the enhancing mucosa and the muscularis propria, respectively. The low attenuation of the middle layer results from submucosal edema or inflammation Many malignant liver lesions may show a hypoechoic halo—the target sign of a liver lesion (Fig. 10C). The cause of this sonolucent halo is controversial and is nonspecific and can also be seen in hepatocellular carcinoma, adenoma, focal nodular hyperplasia, hemangioma, lymphoma, and fungal microabscesses A reversed target sign with hyperechoic rim due to septal fibrosis and increased vascularity was described in cirrhotic liver nodules. The target sign was also described on ultrasound of metastatic melanoma of the breast
Torricelli-Bernoulli sign	Crescent-shaped necrosis (Torricelli-Bernoulli sign) in large GIST
Wall-echo-shadow (WES triad, double-arc sign)	Wall-echo-shadow (WES triad, double-arc sign) is seen if the GB is contracted (type II) and completely filled with stones; however, WES triad can also be seen with: Porcelain GB (calcification of GB) Emphysematous cholecystitis
Water lily sign	• Water lily sign Echinococcus (hydatid disease)