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Ezekiel T. Arteta
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PLAIN FILM
Detects colonic obstruction, colonic ileus, and the toxic megacolonsyndrome in IBD
SINGLE CONTRAST
Demonstrates anatomy and tonus (contraction) of colon, along with mostabnormalities
DOUBLE CONTRAST
Allows visualization of lumen with any polyps or lesions
CT
Determines the presence and extent of extracolonic disease
UTZ
Rarely used because of intraluminal gas
Imaging
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Anatomy
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Function
Formation, transport, and evacuation of feces
Water absorption by the right colon
Physiology
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Filling Defect radiolucency in a barium pool caused by a protruding mass lesion.
May be caused by polyps, tumors, air bubbles, feces, mucus, or foreign objects.
Polyp
Protrusions from the mucosa
Does not imply a histologic diagnosis
Colon Filling Defects/ Mass Lesions
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Most common malignancy of the GI tract
Location:
Rectum and Rectosigmoid area (50%)
Sigmoid Colon (25%)
Most developed from preexisting adenomasMost are annular constricting lesions, with raised everted edges andulcerated mucosa.
Spreads through
Colorectal Adenocarcinoma
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Colorectal Adenocarcinoma
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Spreads through: Direct Invasion into pericolonic fat and adjacent organs
Lymphatic Invasion to regional nodes
Hematogenous Invasion through the portal veins to the liver and the systemic
circulation
Most common complication is obstruction
Colorectal Adenocarcinoma
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Risk factors: Ulcerative colitis
Crohns disease
Familial Adenomatous Polyposis
Peutz-Jeghers syndrome
Clinical Features
Peak age 50-70 years
Weight loss
Blood in stool
Loss of appetite
Change in bowel habits
Colorectal Adenocarcinoma
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Imaging Methods Transrectal or Colononoscopic US: Local disease staging
CT and MR: For more advanced disease and to detect recurrence
CT is the method of choice for tumor recurrence because it can survey the whole
abdominal cavity
Colorectal Adenocarcinoma
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Cross-Sectional Findings
Polypoid Primary Tumor (usually >1 cm)
Apple-core lesions
Cystic, necrotic, and hemorrhagic areas within the tumor mass
Linear soft tissue stranding into the pericolonic fat
Enlarged regional lymph nodes
Distant metastases, especially in the liver
Thickening of the wall of the uninvolved colon proximal to the tumor
Colorectal Adenocarcinoma
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Annular Adenocarcinoma(Single Contrast Study)
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Localized mass that projects from the mucosa into the lumen.
Presence is a major indication for barium studies of the colon
Rules of Thumb:
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Hyperplastic polyps Nonneoplastic; round and sessile, nearly all are smaller than 5
mm
Adenomatous polyps Distinctly premalignant; major risk for developing
adenocarcinoma
Neoplasms with a core of connective tissue
Hamartomatous polyps (juvenile polyps) common cause of rectal bleeding in children
Inflammatory polyps
usually multiple; associated with inflammatory bowel disease
Polyps
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Polyp
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Bowler Hat Sign
Polyp
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Polyp
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2/3 inherited, 1/3 spontaneous
Autosomal dominant
Tubulovillous adenomas that becomes prominent at age 20
Colorectal cancer will eventually develop in nearly all patients
Tx: total colectomy with rectal mucosectomy and ileoanal pouchconstruction
Familial Adenomatous PolyposisSyndrome
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Familial Adenomatous PolyposisSyndrome
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Less commonly involved than the stomach or small bowel Anal and rectal lymphoma= frequent in AIDS patients
Morphology
Multinodular (lymphomatous polyposis)
Solitary (resemble a polypoid carcinoma)
Lymphoma
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Rectal Lymphoma
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Most common submucosal tumor of the colon
Most frequent in the cecum and ascending colon
Nearly 40% present with intussusception
Appearance:
Barium: smooth, well-defined, elliptic filling defect, usually 1 to 3 cm in diameter
CT: fat-density tumor (definitive)
Lipoma
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Ulcerative Colitis
Crohns Disease
Infectious Colitis
Toxic Megacolon
Pseudomembranous Colitis
Amoebiasis
Colon Inflammatory Diseases
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Idiopathic inflammatory disease involving primarily the mucosa andsubmucosa of the colon
Peak age: 20 to 40 years, onset after age 50 is common.
Superficial ulcerations, edema, and hyperemia
Granular mucosa, confluent shallow ulcerations, symmetry of diseasearound the lumen, and continuous confluent diffuse involvement.
Ulcerative Colitis
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Radiographic Hallmarks:
Granular mucosa
Confluent shallow ulcerations
Symmetry of disease around the lumen
Continuous confluent diffuse involvement
Morphology:
Collar button ulcers: deeper ulcerations of thickened edematous mucosa with crypt abscesses
extending in the submucosa
Coarse granular pattern by replacement of diffusely ulcerated mucosa with granulation tissue
Ulcerative Colitis
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Collar Button Ulcers
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Late Changes:
Pseudopolyps= mucosal remnants in areas of extensive ulceration
Inflammatory polyps= small islands of inflamed mucosa
Postinflammatory polyps= mucosal tags that are seen in quiescent phases of the disease
Filiform polyps= postinflammatory polyps with a wormlike appearance
Hyperplastic polyps= may during healing after mucosal injury
Ulcerative Colitis
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CT Findings Halo sign: low-density submucosal edema with wall thickening
Narrowing of the lumen of the colon
Pseudopolyps
Pneumatosis coli with megacolon
Complications:
Strictures
colorectal adenocarcinoma
Ulcerative Colitis
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Complications: Strictures
Colorectal adenocarcinoma
Toxic megacolon
Massive hemorrhage
Ulcerative Colitis
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Strictures
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Lead Pipe Sign
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Involves the colon in two thirds of cases
Isolated to the colon in approximately one third of all cases
Hallmarks:
Early aphthous ulcers
Later confluent deep ulcerations
Predominant right colon disease
Discontinuous, asymmetric involvement
Strictures, fistulas, and sinus formation
Crohns Disease
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Ulcerative Colitis Crohn Colitis
Circumferential disease Eccentric disease
Regional (continuous disease) Skip lesions (discontinuous disease)
Predominantly left-sided Predominantly right-sided
Rectum usually involved Rectum normal in 50% of casesConfluent shallow ulcers Confluent deep ulcers
No aphthous ulcers Aphthous ulcers early
Collar button ulcers Transverse and longitudinal ulcers
Terminal ileum usually normal Terminal ileum usually diseased
Terminal ileum patulous Terminal ileum narrowed
No pseudodiverticula Pseudodiverticula
No fistulas Fistulas common
High risk of cancer Low risk of cancer
Risk of toxic megacolon No toxic megacolon
Ulcerative Colitis vs. Crohns Disease
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Etiologic Agents:
Bacteria (Salmonella, Shigella, E. coli)
Parasites
Viruses (CMV, Herpes)
Fungi (Histoplasmosis, Mucormycosis)
Most cause a pancolitis with edema and inflammatory wall thickening withinfiltration of pericolonic fat
Pericolonic fluid and intraperitoneal fluid may be present.
Infectious Colitis
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CMV Colitis
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Potentially fatal
Marked colonic distension and risk of perforation
Complication of fulminant colitis
Radiographic Findings:
Marked dilatation of the colon (transverse colon >6 cm) with absence of haustral markings
Edema and thickening of the colon wall
Pneumatosis coli
Evidence of perforation
Barium studies must be avoided
Toxic Megacolon
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Inflammatory disease characterized by the presence of a pseudomembraneof necrotic debris and overgrowth ofClostridium difficile
Radiographic Findings:
Dilated colon
Nodular thickening of the haustra
Ascites
Pseudomembranous Colitis
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CT findings:
marked wall thickening up to 30 mm (average 15 mm) with halo or target appearance
characteristic stripes of intraluminal contrast media trapped between nodular areas of wall
thickening (accordion sign)
Mild pericolonic fat inflammation disproportionate with the marked colonic wall inflammation
ascites
Pseudomembranous Colitis
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Pseudomembranous Colitis
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Infection by the protozoan parasite Entamoeba histolytica
Barium studies demonstrate a disease that closely mimics Crohn colitis
Primary areas: cecum and rectum (terminal ileum is characteristically notinvolved)
Amoebiasis
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Diverticulosis
Diverticulitis
Diverticular Diseases
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Acquired condition
Mucosa and muscularis mucosae herniate through the muscularis propria ofthe colon wall, producing a saccular outpouching
False diverticula
Common with age over 75 years oldMajor risk factor: low-residue diet
Most common site: sigmoid colon
Diverticulosis
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Severely affected portions of bowel are usually shortened in length, resulting incrowding of the thickened circular muscle bundles.
Diverticulosis without diverticulitis is a cause of painless colonic bleeding
Radiographical Findings:
gas-filled sacs parallel to the lumen of the colon Barium studies show diverticula as barium or gas-filled sacs outside the colon lumen
Diverticulosis
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CT Findings Thickened colon wall and distorted luminal contour
diverticula are shown as well-defined gas-, fluid-, or contrastfilled sacs outside the
lumen
Diverticulosis
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Diverticulosis
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inflammation of diverticula, usually with perforation and intramural orlocalized pericolic abscess
Complications:
Bowel obstruction
Bleeding
Peritonitis
Sinus tract and fistula formation
Diverticulitis
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inflammation of diverticula, usually with perforation and intramural orlocalized pericolic abscess
Complications:
Bowel obstruction
Bleeding
Peritonitis
Sinus tract and fistula formation
Diverticulitis
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Barium Studies deformed diverticular sacs
demonstration of abscess
extravasation of barium outside the colon lumen
CT Findings
localized wall thickening
inflammation of pericolonic fat
pericolonic abscess
diverticula at or near the site of inflammation
Diverticulitis
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Diverticulitis
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Filling of the appendix is attained most reliably by single-contrast bariumenema examination
Failure to fill the appendix with barium on barium enema examination is notdefinitive evidence of appendiceal disease.
Both CT and US have proven extremely useful in the diagnosis of
appendiceal disease, especially acute appendicitis
Appendix
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arises from the posteromedial aspect of the cecum at the junction of the taeniacoli, approximately 1 to 2 cm below the ileocecal valve.
blind-ended tube that is 5 to 10 mm in diameter (on barium studies) andapproximately 8 cm in length, although it may be up to 30 cm long.
mucosa is heavily infiltrated with lymphoid tissueOn CT and US, the normal appendix appears as a thin-walled tube less than 6 mmin diameter
Anatomy
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Anatomy (CT Scan)
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most common cause of acute abdomenresults from obstruction of the appendiceal lumen
Bacterial infection causes gangrene and perforation with abscess
Most periappendiceal abscesses are walled off, but free perforation and
pneumoperitoneum occasionally occur
Acute Appendicitis
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Plain films will demonstrate an appendiceal calculus (appendicolith orfecalith) in approximately 14% of patients
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