3Appendix Normal appendix A thin walled tubular structure that may be collapsed or filled with air, fluid or contrast.Normally does not exceed 6mm diameter and has a sharp contour defined by homogeneous low-density mesenteric fat.Originates between the ileocecal valve and the cecal apex on the same side as the valve. (1/3 course inferomedially from the cecum and 2/3 are retrocecal).Tips for finding the appendix: trace the colon from the anus to the cecum. The appendix will be located along the cecum on the opposite side of the ileocecal valve from the ascending colon.Normal air-filled appendix (arrow)
4Appendicitis Demographics: Any age, most commonly 10-30 years old Slightly more common in males (1.4 : 1)Clinically:Abdominal pain, often RLQNauseaVomitingFeverNote enlargement of the appendix (arrows), intraluminal fluid, and adjacent inflammatory stranding
5Possible findings in acute appendicitis Enlarged appendix, > 6 mm in diameterAppendiceal wall thickeningAppendiceal wall enlargementPeriappendiceal fat strandingFocal cecal apical thickeningDetection of an appendicolith - appearing as a ringlike or homogeneous calcification (viewing the CT with bone windows aids in detection).
6Normal Bowel ImagingLarge bowel has haustra scattered all along the colon. The colon also has epiploicae (fat filled tags) on its surface. These haustra and epiploicae separate the large from the small intestine. Colon is filled with feces which has bubbly appearanceThe small bowel is located in the center of abdomenFairly narrow about 2.5 cm tube like structure winds compactly back and forth within the abdominal cavityThe small intestine is identified by valvulae circulares or circular folds on oral contrast study.
7SBO: Postop and paralytic ilues Demograpics:Patients who are postop, have a malignancy, Crohn’s, or hernia.Patients on narcoticsClinically:Constipation, Nausea, and vomitingAbdominal fullness/excessive gasPain and cramps in stomach areaAxial CT scan through the lower abdomen shows multiple fluid-filled and dilated loops of small bowel (white arrows) and collapsed right colon (red arrow) consistent with a mechanical small bowel obstruction.
8SBO: RadiographMultiple dilated small bowel loops are seen (white arrowheads).There is fecal material in the right and left colon (arrows).Air is seen in the rectum.The surgical staples indicate recent abdominal surgery. (black arrowheads).
9Upright Abdominal Film Air - Fluid LevelsDilated Small Bowel
11Large Bowel Obstruction Dilated bowel loops proximal to the obstruction.Arrow points to the etiology of obstruction.
12DiverticulosisSmall saclike outpouchings of mucosa and submucosa through the muscular layers of the wall of the colon.Most common in the sigmoid colonSmall rounded collections of air, feces, or contrast outside the lumen. Ranging from 1mm to 2 cm.Thickening of the muscular wall of the colon is commonNo itis here, this is moderate diverticulosis of the sigmoid colon
13Diverticulosis Demographics: Clinically: Rare before age 40Incidence increases with ageMay be associated with low-fiber dietClinically:Most often asymptomatic, diagnosed incidentallyMay be associated with lower abdominal discomfort, bloating, constipationArrowheads point to multiple diverticula arising from the recto sigmoid. The contrast in diverticula is left over from previously administered GI contrast.
14Diverticulosis- Radiograph This radiograph shows scattered diverticula throughout the abdomen. On the right is a magnified view of the left lower quadrant of the same radiograph. Notice the many scattered diverticula throughout the sigmoid and descending colon (arrows).
15Diverticulitis Demographics: Clinically: See Diverticulosis Abdominal pain, often LLQNauseaVomitingConstipation or diarrheaFeverNote wall thickening in the sigmoid colon (arrows) and adjacent inflammatory changes in the pericolic fat
16Colitis: UC vs Crohn’sCrohn’s – Transmural inflammation usually effects the terminal ileum and proximal colon.Wall thickening 10-20mmOuter wall is irregularActive disease shows layering of the colon (target and halo signs)Chronic disease with fibrosis show homogeneous enhancement of the colon wallFibrous and fat proliferation separate bowel loops-Additional findings – lymph nodes up to 1cm in mesentary, fistulas, sinus tracts, abscesses, phlegmonsUC – Inflammation and diffuse ulceration of the colon mucosa starting in the rectum and extending proximally.Wall thickening (7-8mm) with lumen narrowingOuter wall is smooth
17Ulcerative Colitis Demographics: Clinically: Peak incidence between 15 – 30 years oldEqual incidence in males and femalesClinically:Diarrhea (can be > 10 loose stools / day), often bloodyRectal bleedingPassage of mucus with defecationAbdominal painConstipationFeverNote diffuse thickening of the sigmoid colon (arrows) and minimal adjacent inflammatory stranding
18Example of Ulcerative colitis CT scan of a patient with long-standing ulcerative colitis shows a submucosal halo of fat within the rectum (arrow). There is also perirectal fibrofatty proliferation (*).
19Crohn’s Disease Demographics: Clinically: Two peaks of incidence: 15 – 30 and 50 – 80 years oldEqual incidence in males and femalesClinically:Abdominal painDiarrhea (usually non-bloody)SteatorrheaFatigueOral ulcersNote thickening of the terminal ileum (curved arrow) and cecum (straight arrow) and inflammatory changes in the adjacent fat
20Example of Crohns White attenuation: enhancement in ileal Crohn disease. On an intravenous contrast-enhanced CT scan, the enhanced thickened wall of the small bowel (solid arrows) is slightly higher attenuation than the inferior vena cava (open black arrow). The vasa recta are dilated (arrowhead) and separated by increased fat deposition ("creeping fat sign"). Open white arrow = enlarged mesenteric node.
21Colitis: InfectiousPseudomembranous colitis (C. Diff) – Cytotoxic entertoxin ulcerates the mucosa and creates pseudomembranes of mucin, fibrin and inflammatory cellsPancolitis or segmental with irregular wall thickening up to 30 mm with shaggy endoluminal contour.Submucosal edama creates an “accordian pattern”
22Colitis: IschemicUsually occurs in setting of low cardiac output in pts w/ extemsove. But nonocclusive vascular disease.Affects watershed areas most: splenic flexure and rectosigmoid region.Produces halo sign in postcontrast scans, stranding and inflammation in pericolic fatComplications: hemorrhage, pneumatosis,
23Example of Diffuse ischemic colitis CT scan obtained with oral and intravenous contrast material shows diffuse, low-attenuation thickening of the colonic wall (arrows). This is an example of the water halo sign.Water halo sign: diffuse, low-attenuation thickening of the colonic wall (arrows)
24Pseudomembranous colitis Demographics:Most commonly caused by C.diff overgrowth following treatment with antibioticsAdvanced age is risk factorClinically:Watery diarrhea (5-10x per day)Abdominal crampsHematocheziaFeverNote diffuse wall thickening throughout the colon (arrows), and pericolic inflammationReturn to Table of Contents
25Pseudomembranous colitis- cont’d (Left) Axial CT scan of the midabdomen utilizing oral but not intravenous contrast demonstrates marked thickening of the colonic wall (white arrows) producing the so-called "accordion sign." There is a small amount of pericolonic stranding (red arrow) and ascites (green arrow). (Right) Axial CT scan through the pelvis shows marked thickening of the wall of the rectum (yellow arrows) indicating this is a pan-colitis.
26Adenocarcinoma (Colon) Demographics:Uncommon before age 40; 90% of cases are after age 50In the US, male incidence is 25% higher than femaleClinically:Abdominal painChange in bowel habitsHematochezia or melenaIron deficiency anemiaNote circumferential thickening of the cecum (curved arrows) and a hypodense focus within the wall which is due to necrosis (straight arrow)
27Major complication of many types of colitis: Toxic megacolon Dilation> 5cm w/ thinning of colon wall, pneumatosis and perforation
28Colonic volvulus (Usually diagnosed on x-ray) Twisting of folding of an intraperitoneal segment of the colonSigmoid volvulus – apex points toward the left lower quadrantCecal volvulus – apex points toward the right lower quadrant.Swirl sign of SigmoidVolvulus in a 5 yo >
30Liver- AnatomyThe Couinaud classification of liver anatomy divides the liver into eight functionally indepedent segments. Each segment has its own vascular inflow, outflow and biliary drainage. In the center of each segment there is a branch of the portal vein, hepatic artery and bile duct. In the periphery of each segment there is vascular outflow through the hepatic veins.
33Segment 1: The caudate lobe The caudate lobe is anatomically different from other lobes in that it often has direct connections to the IVC through hepatic veins, that are separate from the main hepatic veins.The caudate lobe may be supplied by both right and left branches of the portal vein.
34Identifying segmentsThe first step in correctly identifying the remaining segments is to is to locate the portal vein.The arrow is pointing to the portal vein and, in this image, is at the junctions between the upper and lower segments.
35Identifying segmentsAbove the portal vein will be segments 2, 4a, 8 and 7
36Identifying SegmentsBelow the portal vein will be segments: 3,4b, 5 and 6
37Identify the branches of the hepatic vein Right hepatic vein: divides the right lobe into anterior and posterior segments.Middle hepatic vein: divides the liver into right and left lobes. This plane runs from the inferior vena cava to the gallbladder fossa.Left hepatic vein: divides the left lobe into a medial and lateral part.
38Right lobeIdentify the right hepatic vein which divides the right lobe into anterior (segment 8 & 5) and posterior segments ( segment 6 & 7).Anterior lobe:Segment 8 is located superior to the the portal vein.Segment 5 is Located inferior to the portal veinPosterior Lobe :Segment 7 is located superior to the portal veinSegment 6 is Located inferior to the portal vein
39Left LobeThe left lobe is divided into medial and lateral segments by the left hepatic vein.To the left of the left hepatic vein are segments 2 & 3.Segment 2 is located superior to the portal vein.Segment 3 is located inferior to the portal vein.To the right of the left hepatic vein are segments 4a & 4bSegment 4a is located superior to the portal vein.Segment 4b is located inferior to the portal vein.
40Normal liver, unenhanced CT Note the areas of hypodensity (arrows), which are normal hepatic and portal veins coursing through the liver.Photo, Armstrong et al, 2004
41Normal liver CT, enhanced Note the increased density of the hepatic and portal veins. Also note the adjacent stomach, which is filled with contrast.Photo, Armstrong et al. 2004
42Homogeneity – Hepatic Neoplasms Knowing which lesions are hypervascular (hyperintense) and which are hypovascular (hypodense) can help identify the type of neoplasm, but the key thing is that they are of a different density than the surrounding liver parenchyma.Hypervascular examples: carcinoid tumor mets, hepatocellular carcinomaHypovascular examples: colon cancer mets, cholangiocarcinomaMost mets, as opposed to primary tumors, are rounded and well demarcated from surrounding parenchyma on enhanced scans.
43Appearance of various liver neoplasms during early arterial phase Hypovascular metastasis due to colon cancerHypovascular primary cholangiocarcinomaCarcinoid tumor metastasis is hypervascularPrimary hepatocellular carcinoma is hypervascular (hypodense area is necrosis)
44Homogeneity – Cysts and Abscesses Contrast also helps identify cysts and abscesses, which contain collections of fluidCysts: Have well-defined margins and are low density (attenuation similar to water), unenhancing lesionsNote: cysts below ~ 1cm in size cannot be reliably distinguished from neoplasmsAbscesses: appear similar to cysts, but usually their walls are thicker (due to surrounding edema) and more irregularMay not be able to distinguish from a necrotic tumor
45Hepatic Cyst vs. Abscess Photo, Novelline et al, 2004Photo Lee et al, 1998Left, hepatic cyst; right, hepatic abscess. Note the thickened wall of the abscess.
46Homogeneity – Liver Trauma Trauma can cause hepatic parenchymal lacerations, subcapsular and intrahepatic hematomasAll are low-density areas relative to contrast-enhanced parenchymaLeakage of contrast = active bleeding
48GallbladderUltrasound is the preferred initial modality in the investigation of right upper quadrant pain.Normal gallbladder on US
49Cholecystitis Demographics: Clinically: "fat, forty, female and fertile ”Incidence increases with ageMay be associated with low-fiber dietClinically:Fever, Nausea, and vomitingPositive Murphy’s SignElevated WBCUS findings: Thick GB wall, stones in GB,absence of echoes posterior to the calculi "Shadowing"
50Gallstones on CTAlthough less sensitive than ultrasound, CT findings include :CholelithiasisGallbladder distensionGallbladder wall thickeningMural or mucosal hyperenhancementPericholecystic fluid and inflammatory fat strandingEnhancement of the adjacent liver parenchyma due to reactive hyperaemiahyperattenuating calculi (arrow) in gallbladder
51PancreasThe head of the pancreas is surrounded by the duodenum as it makes a C-loop around the pancreas. The tail is in the hilus of spleen.With contrast enhancement it has the same density as liver and spleen.It is recognizable by the splenic vein running along posterior inferior groove.The common bile duct traverses through the head of the pancreas and joins with the pancreatic duct at the ampulla of Vater to empty bile into the second or descending part of the duodenum. Normal pancreas
52Pancreatitis Demographics Any age, however less common <45 years Clinically:Abdominal pain, fever, nausea, and vomiting
53Acute Pancreatitis Excepted findings: Enlargement of pancreas due to edemaPeripancreatic inflammation: linear strands in the peripacreatic fatPhlegmonHemorrhagic: Enlarged pancreas with increased density due to hemorrhageNecrosis: On contrast enhanced phases the necrotic pancreatic parenchyma will show decreased or no enhancement when compared with normally enhancing viable tissueDiffusely enlarged pancreas with low density from edemaC: Colon St: Stomach P: Pancreas
54Chronic PancreatitisMay show dilated duct, enlarged pancreas, pseudocyst, calcificationOptimal visualization with helical CT using pancreas-optimized protocol - water as oral contrast agent, initial scan without IV contrast, then contrast infusion using pancreatic cancer protocolLimited usefulness in early chronic pancreatitisMass density in pancreasWhite arrow: PsudocystBlack arrow: Calcifications
55Acute Pancreatitis on KUB Radiographic findings:Cut off sign and IleusCut off sign: abrupt termination of gas within the proximal colon at the level of splenic flexure, seen on abdominal radiographs, CT, and barium enema in patients with acute pancreatitis.White arrowpoints to Transeverse colon cut off at Splenic flexure. No air in descending colon.TC: Transverse colonI: Represents small bowel loops with air suggestive of Ileus
56Chronic Pancreatitis on KUB Radiographic findings:Calcifications in the pancreasPseudocysts: As necrotic pancreatic tissue liquefies, it forms a "pseudocyst”.This may be in the region of the pancreas or extend beyond the pancreatic region.