Radiology of Digestive System
Department of Radiology Zhongshan Hospital, Fudan university
RAO Sheng-Xiang
Plain film radiograph
Hepatic angle
Spenic angle
Renal shadow
Psoas muscle
Properitoneal fat strip
Normal CT anatomy
1.LHV, left hepatic vein
2.MHV, middle hepatic
vein;
3.RHV, right hepatic vein;
4.IVC, inferior vena cava
5.Ao,aorta
6.Stomach
12
3 4 5 6
1.LPV, left portal vein
2.Stomach
3.Speen
4.IVC, inferior vena cava
5.Ao,aorta
5
2
3
1
4
1.Gallbladder
2.RPV, right portal vein
3.antrum
4.duodenal bulb
3
4
1
1
1.CA,celiac axis2.Splenic artery3.common hepatic artery4.Duodenum5.Kidney6.Pancreas7.Portal vein8.Adrenal gland
12
3
4
55
67
SMA:superior
mesenteric artery
CBD,common bile duct
Spenic vein
Pancreas
SMV, superior mesenteric
vein
SMA, superior mesenteric
artery
Uncinate process
CTA
SMA, superior
mesenteric artery
CA,celiac axis
Splenic artery
common hepatic artery
main portal trunk; right portal branch; splenic vein; inferior mesenteric
vein; superior mesenteric
vein
RHV, right hepatic vein;
MHV, middle hepatic vein;
LHV, left hepatic vein
IVC, inferior vena cava
pancreatic duct
Upper abdominal calcificationmay be an important sign of diseaseGallstones ,Porcelain gallbladderUrinary CalculiCalcified adrenal glandsPancreatic calcificationTumor calcification……………
Gallstones 15% -20%of gallstones
contain sufficient calcium to be identified on plain film
right upper quadrant laminated appearance(a dense outer rim and
more radiolucent center)
Porcelain gallbladder
calcification in the wall of the gallbladder
indicative of chronic obstruction of the cystic duct, chronic gallbladder inflammation, and an increased risk of gallbladder carcinoma
diffuse Discontinuous mural calcification
Kidney stones
• About 85% of urinary calculi are visible on plain film.
• Staghorn Calculus a large calculus
occupying the collecting system of the left kidney and assuming its shape
Calcified adrenal glands
associated with adrenal hemorrhage in the newborn, tuberculosis, and Addison disease
either side of the first lumbar vertebra
Pancreatic Calcifications
• chronic alcohol-induced pancreatitis
• Coarse and punctate calcifications
• extend upward across the left upper quadrant
Intestinal Distention
• The small bowel is dilated when it exceeds 2.5 to 3.0 cm in diameter.
• The colon is dilated when it exceeds 5 cm in diameter
• The cecum is dilated when it exceeds 8 cm in diameter.
Normal Bowel Gas Pattern
The normal distribution of gas in the stomach and duodenum
The colon----- mottled pattern of stool
The small bowel----a few gas collections
Mechanical bowel obstruction Small Bowel
• Dilated loops of small bowel (>3 cm)• Air-fluid levels that exceed 2.5 cm in length• Air-fluid levels at differing heights within the
same loop (strong evidence of obstruction)• Small bubbles of gas trapped between the
valvulae conniventes
Causes of Small Bowel Obstruction
• Erect radiograph of the abdomen
• Air-fluid levels at different heights
• The valvulae conniventes that extend across the entire diameter of the bowel lumen
Mechanical bowel obstruction Large Bowel
• Most colonic obstructions occur in the sigmoid colon
• Dilation of the colon from the cecum to the point of obstruction
• The colon distal to the obstruction is devoid of gas
Causes of Large Bowel Obstruction
Sigmoid volvulus• A large gas-filled
loop(inverted U shape or a coffee bean shape) without haustra or septa,
• Arising from the pelvis and extending high into the abdomen and often to the diaphragm
• Barium enema: a beaking sign at the point of the twist
Adynamic ileus(Functional ileus)
Decreased or absent peristalsis
Diffuse gaseous, distension of bowel(small bowel and colon,rectum)
Pneumoperitoneum
Common causes:bowel perforation, trauma, recent surgery
Free air beneath the domes of the diaphragm
Dysphagia: Esophagus
• The length of the esophagus is tubular, and its termination is saccular
• A ring: the tubulovestibular junction is formed by a symmetric muscular ring
• B ring : an asymmetric mucosal ring or notch that occurs at the junction of esophageal squamous epithelium with gastric columnar epithelium
The esophageal vestibule demarcated by the muscular A
ring and the mucosal fold of the B ring
B ring (mucosal ring) <14mm---always symptomatic14mm-20mm--50% symptomatic >20mm---asymptomatic
Benign Stricture Resulting from Reflux Esophagitis
usually confined to the distal esophagus
may be tapered, smooth, and circumferential (the classic appearance)
Esophageal carcinomaFour basic radiographic patternsAn annular constricting lesion, appearing as an
irregular ulcerated stricture, is most common. The polypoid pattern causes an intraluminal filling
defect The infiltrative variety grows predominantly in the
submucosa and may simulate a benign stricture. The least common pattern is that of an ulcerated
mass.
Malignant Stricture Abrupt narrowing with
irregular mucosa The prominent
shoulders are characteristic of tumor
Polypoid Squamous Cell Carcinoma
Esophageal achalasia
• usually at age 30 to 50 years
• Absence of peristalsis of body of esophagus
• Failure of the LES to relax with swallowing
• Smooth,tapered or beaklike appearance
Anatomy of the Upper GI Tract
Normal anatomy of stomach
composed of the cardia, fundus, body, and antrum
A well-distended stomach has a wall thickness of approximately 5 mm
Benign Ulcer(1)
• Projection beyond the lumen of stomach
• soomth lucent line (collar ) at the neck of ulcer
Benign Ulcer(2)
Hampton line :a thin, sharp, lucent line that traverses the orifice of the ulcer.
Benign Ulcer(3)
Radiating folds extending into the crater
Malignant ulcer
location within the lumen of the stomach
nodular, rolled, irregular, or shouldered edges
Gastric adenocarcinoma
The most common malignancy in the stomachThe pattern of spread : local extension , distant metastases drop metastases to the ovaries
• Polypoid Gastric Carcinoma. a lobulated filling defect (arrows) in the antrum of the stomach.
CT:focal wall thickening
diffuse wall thickening
a lobular mass with or without ulceration
destruction of the multilayered pattern or
with transmural enhancement
regional lymphadenopathy; metastases
CT:
Focal wall thickening
transmural enhancement
CT:diffuse wall thickening
Locally invasive gastric adenocarcinoma
• heterogeneous thickening of the gastric fundus.
• growing into the splenic hilum , left adrenal gland
• A large heterogeneous mass in the body of the stomach
• round and contains an ulcer
• A large metastasis lies in the liver
Lymphatic spread
Gastrointestinal stromal tumors (GISTs)
extragastric
(most cases)
Growth pattern)
polypoid in appearance (small GISTs)
Large, heterogeneous exophytic mass
Extensive ulceration of the mass
Diffuse Liver Disease
Fatty liver
Cirrhosis
Fatty liver(Steatosis)
In normal adults, the precontrast attenuation value of the liver is consistently higher than that of the spleen
Milder degrees of diffuse steatosis :the attenuation value of the liver is less than that of the spleen
Marked diffuse steatosis :the liver parenchyma is lower in attenuation than the hepatic blood vessels
• The attenuation value of the liver parenchyma is markedly lower than that of the spleen
• The intrahepatic vessels stand out as hyperattenuating structures
Focal fatty infiltration
• The same imaging features as diffuse infiltration
• Vessels run their normal course through the area of involvement
(lack of mass effect )
Cirrhosis
hypertrophy of the caudate lobe and left lobe
with shrinkage of the right lobe
inhomogeneity of hepatic parenchyma,
irregularity (nodularity) of the liver surface,
Extrahepatic signs :evidence of portal
hypertension, splenomegaly, and ascites
• nodularity of the liver contour
• atrophy of the medial segment (M) and enlargement of the lateral segment
• prominent notch in the right posterior surface of the liver
Focal Liver diseases
Cyst
Hemangioma
Hepatocellular carcinoma
metastasis
Cyst:CT appearance
a well-circumscribed, homogeneous mass of
near-water-attenuation value (less than 20
HU)
no enhancement after IV contrast medium
administration
• Two large well-circumscribed, homogeneous, near-water-density masses
• no discernible wall
Hemangioma
the most common benign liver tumor
fed by hepatic artery branches
internal circulation is slow
generally remain stable in size over time
• well-defined, hypodense on unenhanced scans
• Enhancement pattern : nodular enhancement from the periphery of the lesion and proceeding toward the center gradually
Precontrast CT :an attenuation value similar to that of the blood in the inferior vena cava(IVC)
Arterial phase :multiple areas of globular, peripheral enhancement. Note that the enhanced portions of the mass have an attenuation value
similar to that of the intrahepatic vessels.
• Equilibrium phase : near-complete enhancement of the mass with an attenuation value equivalent to that of the blood in the inferior vena cava(IVC) and hepatic veins
T2WI:marked hyperintense
Hepatocellular carcinoma
• The most common primary malignancy of the liver
• Risk factors : cirrhosis, chronic hepatitis• Growth patterns: solitary massive, multinodular, and diffuse
infiltrative• Serum α-fetoprotein(AFP) levels are often
elevated
Hypervascular :contrast enhancement on
arterial phase images, with diminishing
enhancement on delayed phase images
Tumor thrombus
Tumor capsule: a sharply marginated rim
Necrosis: central low
density
The satellite lesions
T2WI T1WI
AP PP DP
Portal Vein Thrombosis
Multiple hypodense
nodules ----HCC
Filling defect with the
vein
Metastases
The most common malignant masses in the liver
Most commonly originate from the GI tract, breast, and lung
Necrosis, fibrosis, calcification, or hemorrhage within the mass
The most common enhancement pattern :continuous ring-like enhancement
• Multiple
• Hypoattenuating lesions
with mild continuous rim
enhancement
T2WI:a central area of hyperintensity
rim enhancement
Normal MR Cholangiopancreatography (MRCP).
Biliary Dilatation
• Diameter of intrahepatic bile ducts larger than 40% of the diameter of the adjacent portal vein
• Dilation of the common duct greater than 6 mm
• Gallbladder diameter greater than 5 cm
Causes of Biliary Tract Obstruction
Choledocholithiasis
approximately 20% of cases of obstructive
jaundice in the adult
CT:high-density calcification within the duct
MRCP has shown good sensitivity (86% to
100%) and specificity (85% to 100%) for ductal
stones
MRCP
Filling defects
Cholangiocarcinoma
arise from the epithelium of bile ducts and are usually adenocarcinomas
Growth patterns include mass forming, periductal infiltrating, and intraductal polypoid
• Mass forming
• periductal infiltrating
• Intraductal polypoid
Peripheral cholangiocarcinoma
Delayed enhancementbiliary dilatationAtrophy (liver)
Perihilar and extrahepatic cholangiocarcinomas
typically exhibit an infiltrating growth pattern focal, circumferential thickening of the bile
duct with proximal dilatationperihilar lesions may be similar in appearance
to the intrahepatic, mass-forming type of cholangiocarcinoma, or may manifest as an intraluminal polypoid mass
Pancreatic carcinoma
• a highly lethal tumor • CT is recommended for initial imaging
assessment• CT:a hypodense mass that distorts the
contour of the gland• obstruction of the common bile duct and
pancreatic duct and atrophy of pancreatic tissue beyond the tumor
A B
C D
Signs of unresectability
• tumor involvement of adjacent organs• enlarged regional lymph nodes (>15 mm)• encasement or obstruction of peripancreatic
arteries or veins • metastases in the liver• peritoneal carcinomatosis
Pancreatic Carcinoma: Nonresectable
• encases and narrows the celiac axis and its branches
• partially envelopes the aorta
• Plain film radiographs of the abdomen are important for the assessment of the acute abdomen
• CT, US, and MR provide comprehensive evaluation of the abdomen, including the peritoneal cavity, retroperitoneal compartments, abdominal and pelvic organs, blood vessels, and lymph nodes
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