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Normal Anatomy Appendix  Normal appendix A thin walled tubular structure that may be collapsed or filled with air, fluid or contrast. Normally does.

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Presentation on theme: "Normal Anatomy Appendix  Normal appendix A thin walled tubular structure that may be collapsed or filled with air, fluid or contrast. Normally does."— Presentation transcript:

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2 Normal Anatomy

3 Appendix  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)

4 Appendicitis  Demographics: Any age, most commonly years old Slightly more common in males (1.4 : 1)  Clinically: Abdominal pain, often RLQ Nausea Vomiting Fever Note enlargement of the appendix (arrows), intraluminal fluid, and adjacent inflammatory stranding

5 Possible findings in acute appendicitis  Enlarged appendix, > 6 mm in diameter  Appendiceal wall thickening  Appendiceal wall enlargement  Periappendiceal fat stranding  Focal cecal apical thickening  Detection of an appendicolith - appearing as a ringlike or homogeneous calcification (viewing the CT with bone windows aids in detection).

6 Normal Bowel Imaging Large 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 appearance The small bowel is located in the center of abdomen Fairly narrow about 2.5 cm tube like structure winds compactly back and forth within the abdominal cavity The small intestine is identified by valvulae circulares or circular folds on oral contrast study.

7 SBO: Postop and paralytic ilues  Demograpics: Patients who are postop, have a malignancy, Crohn’s, or hernia. Patients on narcotics  Clinically : Constipation, Nausea, and vomiting Abdominal fullness/excessive gas Pain and cramps in stomach area Axial 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.

8 SBO: Radiograph  Multiple 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).

9 Air - Fluid Levels Dilated Small Bowel Upright Abdominal Film

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11 Large Bowel Obstruction Dilated bowel loops proximal to the obstruction. Arrow points to the etiology of obstruction.

12 Diverticulosis  Small saclike outpouchings of mucosa and submucosa through the muscular layers of the wall of the colon.  Most common in the sigmoid colon  Small 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 common No itis here, this is moderate diverticulosis of the sigmoid colon

13 Diverticulosis  Demographics: Rare before age 40 Incidence increases with age May be associated with low- fiber diet  Clinically : Most often asymptomatic, diagnosed incidentally May be associated with lower abdominal discomfort, bloating, constipation Arrowheads point to multiple diverticula arising from the recto sigmoid. The contrast in diverticula is left over from previously administered GI contrast.

14 Diverticulosis- 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).

15 Diverticulitis Demographics: See DiverticulosisDiverticulosis Clinically : Abdominal pain, often LLQ Nausea Vomiting Constipation or diarrhea Fever Note wall thickening in the sigmoid colon (arrows) and adjacent inflammatory changes in the pericolic fat

16 Colitis: UC vs Crohn ’ s  UC – Inflammation and diffuse ulceration of the colon mucosa starting in the rectum and extending proximally.  Wall thickening (7-8mm) with lumen narrowing  Outer wall is smooth Crohn’s – Transmural inflammation usually effects the terminal ileum and proximal colon. -Wall thickening 10-20mm -Outer wall is irregular -Active disease shows layering of the colon (target and halo signs) -Chronic disease with fibrosis show homogeneous enhancement of the colon wall -Fibrous and fat proliferation separate bowel loops --Additional findings – lymph nodes up to 1cm in mesentary, fistulas, sinus tracts, abscesses, phlegmons

17 Ulcerative Colitis  Demographics: Peak incidence between 15 – 30 years old Equal incidence in males and females  Clinically : Diarrhea (can be > 10 loose stools / day), often bloody Rectal bleeding Passage of mucus with defecation Abdominal pain Constipation Fever Note diffuse thickening of the sigmoid colon (arrows) and minimal adjacent inflammatory stranding

18 Example 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 (*).

19 Crohn’s Disease  Demographics: Two peaks of incidence: 15 – 30 and 50 – 80 years old Equal incidence in males and females  Clinically : Abdominal pain Diarrhea (usually non- bloody) Steatorrhea Fatigue Oral ulcers Note thickening of the terminal ileum (curved arrow) and cecum (straight arrow) and inflammatory changes in the adjacent fat

20 Example 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.

21 Colitis: Infectious  Pseudomembranous colitis (C. Diff) – Cytotoxic entertoxin ulcerates the mucosa and creates pseudomembranes of mucin, fibrin and inflammatory cells Pancolitis or segmental with irregular wall thickening up to 30 mm with shaggy endoluminal contour. Submucosal edama creates an “accordian pattern”

22 Colitis: Ischemic  Usually 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 fat  Complications: hemorrhage, pneumatosis,

23 Example 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)

24 Pseudomembranous colitis Return to Table of Contents Note diffuse wall thickening throughout the colon (arrows), and pericolic inflammation  Demographics: Most commonly caused by C.diff overgrowth following treatment with antibiotics Advanced age is risk factor  Clinically : Watery diarrhea (5-10x per day) Abdominal cramps Hematochezia Fever

25 Pseudomembranous 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.

26 Adenocarcinoma (Colon)  Demographics: Uncommon before age 40; 90% of cases are after age 50 In the US, male incidence is 25% higher than female  Clinically : Abdominal pain Change in bowel habits Hematochezia or melena Iron deficiency anemia Note circumferential thickening of the cecum (curved arrows) and a hypodense focus within the wall which is due to necrosis (straight arrow)

27 Major complication of many types of colitis: Toxic megacolon  Dilation> 5cm w/ thinning of colon wall, pneumatosis and perforation

28 Colonic volvulus (Usually diagnosed on x-ray)  Twisting of folding of an intraperitoneal segment of the colon  Sigmoid volvulus – apex points toward the left lower quadrant  Cecal volvulus – apex points toward the right lower quadrant. Swirl sign of Sigmoid Volvulus in a 5 yo >

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30 Liver- Anatomy The 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.

31 Couinaud classification of liver anatomy

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33 Segment 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.

34 Identifying segments The 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.

35 Identifying segments Above the portal vein will be segments 2, 4a, 8 and 7

36 Identifying Segments Below the portal vein will be segments: 3,4b, 5 and 6

37 Identify 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.

38 Right lobe  Identify 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 vein Posterior Lobe : ○ Segment 7 is located superior to the portal vein ○ Segment 6 is Located inferior to the portal vein

39 Left Lobe  The 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 & 4b ○ Segment 4a is located superior to the portal vein. ○ Segment 4b is located inferior to the portal vein.

40 Normal 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

41 Normal 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

42 Homogeneity – 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 carcinoma Hypovascular examples: colon cancer mets, cholangiocarcinoma  Most mets, as opposed to primary tumors, are rounded and well demarcated from surrounding parenchyma on enhanced scans.

43 Appearance of various liver neoplasms during early arterial phase Carcinoid tumor metastasis is hypervascular Primary hepatocellular carcinoma is hypervascular (hypodense area is necrosis) Hypovascular metastasis due to colon cancer Hypovascular primary cholangiocarcinoma

44 Homogeneity – Cysts and Abscesses Contrast also helps identify cysts and abscesses, which contain collections of fluid  Cysts: Have well-defined margins and are low density (attenuation similar to water), unenhancing lesions Note: cysts below ~ 1cm in size cannot be reliably distinguished from neoplasms  Abscesses: appear similar to cysts, but usually their walls are thicker (due to surrounding edema) and more irregular May not be able to distinguish from a necrotic tumor

45 Hepatic Cyst vs. Abscess Photo, Novelline et al, 2004Photo Lee et al, 1998 Left, hepatic cyst; right, hepatic abscess. Note the thickened wall of the abscess.

46 Homogeneity – Liver Trauma  Trauma can cause hepatic parenchymal lacerations, subcapsular and intrahepatic hematomas  All are low-density areas relative to contrast-enhanced parenchyma  Leakage of contrast = active bleeding

47 Hepatic Laceration Photo,

48 Gallbladder  Ultrasound is the preferred initial modality in the investigation of right upper quadrant pain. Normal gallbladder on US

49 Cholecystitis US findings: Thick GB wall, stones in GB, absence of echoes posterior to the calculi "Shadowing"  Demographics: "fat, forty, female and fertile ” Incidence increases with age May be associated with low- fiber diet  Clinically : Fever, Nausea, and vomiting Positive Murphy’s Sign Elevated WBC

50 Gallstones on CT  Although less sensitive than ultrasound, CT findings include : Cholelithiasis Gallbladder distension Gallbladder wall thickening Mural or mucosal hyperenhancement Pericholecystic fluid and inflammatory fat stranding Enhancement of the adjacent liver parenchyma due to reactive hyperaemia hyperattenuating calculi (arrow) in gallbladder

51 Pancreas  The 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

52 Pancreatitis  Demographics Any age, however less common <45 years  Clinically: Abdominal pain, fever, nausea, and vomiting

53 Acute Pancreatitis  Excepted findings: Enlargement of pancreas due to edema Peripancreatic inflammation: linear strands in the peripacreatic fat Phlegmon Hemorrhagic: Enlarged pancreas with increased density due to hemorrhage Necrosis: On contrast enhanced phases the necrotic pancreatic parenchyma will show decreased or no enhancement when compared with normally enhancing viable tissue Diffusely enlarged pancreas with low density from edema C: Colon St: Stomach P: Pancreas

54 Chronic Pancreatitis  May show dilated duct, enlarged pancreas, pseudocyst, calcification  Optimal visualization with helical CT using pancreas-optimized protocol - water as oral contrast agent, initial scan without IV contrast, then contrast infusion using pancreatic cancer protocol  Limited usefulness in early chronic pancreatitis Mass density in pancreas White arrow: Psudocyst Black arrow: Calcifications

55 Acute Pancreatitis on KUB  Radiographic findings: Cut off sign and Ileus Cut 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 colon I: Represents small bowel loops with air suggestive of Ileus

56 Chronic Pancreatitis on KUB  Radiographic findings: Calcifications in the pancreas Pseudocysts: As necrotic pancreatic tissue liquefies, it forms a "pseudocyst”.This may be in the region of the pancreas or extend beyond the pancreatic region.


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