appendix and colon

7/27/2019 Appendix and Colon

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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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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



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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



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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



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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



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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



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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



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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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appendix and colon

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