Colon (PBR 2) Flashcards
A term that is generic for a lesion that protrudes from the mucosal surface of the GI tract
Polyp
The term does not imply a histologic diagnosis
This refers to radiolucency in a contrast media pool caused by a protruding mass lesion
Filling defects
On CT and barium enema examinations, filling defects maybe polyps, tumors, plaques, air bubbles, feces, mucus, or foreign objects
“Bowler hats”
Polyps
*Creator’s notes
Remember BP
Most common malignancy of the GI tract
Fourth most common malignant tumor
Colorectal adenocarcinoma
Frequent or common locations of colorectal adenocarcinoma
Rectum and rectosigmoid area (50%)
Sigmoid colon (25%)
Remaining are evenly distributed throughout the remainder of the colon (25%)
Morphologic patterns of colorectal adenocarcinoma
Annular constricting lesion
(most common - 2 to 6 cm in diameter, with raised everted edges and ulcerated mucosa)
Polypoid tumor
(less common, some having the frond-like appearance of villous carcinoma)
Infiltrating scirrhous tumor
(common in gastric carcinoma, are rare in the large intestine, unless the patient has ulcerative colitis)
Most frequent/common complication of colorectal adenocarcinoma?
Obstruction
Other complications: Perforation Intussusception Abscess Fistula formation
Diseases that are at increased risk of colon carcinoma
Ulcerative colitis
Crohn disease
Familial adenomatous polyposis syndrome
Peutz–Jeghers syndrome
Local staging of colorectal adenocarcinoma is best evaluated by what imaging method?
Transrectal or colonocopic US
CT and MR are used for more advanced disease and to detect recurrence
Cross-sectional imaging findings of colorectal adenocarcinoma
- Polypoid primary tumor (usually >1 cm)
- “apple core” lesions with bulky, irregular thickening of the colon wall and irregular narrowing of the lumen 3. Cystic, necrotic, and hemorrhagic areas within the tumor mass, especially when the tumor is large
- Linear soft tissue stranding into the pericolonic fat often indicative of tumor extension through the bowel wall
- Enlarged regional lymph nodes (>1 cm) representing lymphatic spread of tumor
- Distant metastases, especially in the liver
Common locations of tumor recurrences
- At the operative site, near the bowel anastomosis
- In lymph nodes that drain the operative site
- In the peritoneal cavity
- In the liver and distant organs
The majority of colorectal cancers are believed to arise from pre-existing adenomatous polyps, the detection of colon polyps is a major indication for colonoscopy and imaging studies of the colon
What is the rule of “rule of thumb” in adenomatous polyps?
Polyps less than 5 mm are almost all hyperplastic, with a risk of malignancy less than 0.5%
Polyps 5 to 10 mm size are 90% adenomas, with a risk of malignancy of 1%
Polyps 10 to 20 mm in size are usually adenomas, with a risk of malignancy of 10%
Polyps larger than 20 mm are 50% malignant
These polyps are nonneoplastic mucosal proliferations
They are round and sessile
Nearly all are less than 5 mm in size
Hyperplastic polyps
These polyps are distinctly premalignant and a major risk for development of colorectal carcinoma
Adenomatous polyps
Approximately 5% to 10% of the population older than 40 years have adenomatous polyps
These polyps represent 1% of colon polyps
They are a common cause of rectal bleeding in children
These polyps are seen in Peutz–Jeghers syndrome
Hamartomas polyps
Polyps that are usually multiple and associated with inflammatory bowel disease
They account for less than 0.5% of colorectal polyps
Inflammatory polyps
Polyposis syndrome in which colorectal cancer will eventually develop in nearly all patients
The inheritance pattern is autosomal dominant with high penetrance
Familial adenomatous polyposis syndrome
Polyps typically carpet the entire colon
Patients are at risk for numerous extracolonic manifestations including carcinomas of the small bowel, thyroid carcinoma, and mesenteric fibromatosis.
Patients with associated bone and skin abnormalities including cortical thickening of the ribs and long bones, osteomas of the skull, supernumerary teeth, exostoses of the mandible, and dermal fibromas, desmoids, and epidermal inclusion cysts have been diagnosed as what syndrome?
Gardner syndrome
Those with associated tumors of the central nervous system have been grouped as Turcot syndrome
These are variations of the same disease
Diseases that cause hamartomatous polyposis syndrome
Peutz-Jeghers syndrome
Cowden disease
Cronkhite-Canada syndrome
Dark pigmented spots on the skin and mucous membranes are characteristic of what hamartomatous polyposis syndrome?
Peutz-Jeghers syndrome
Risk of carcinoma arising from coexisting adenomatous polyps is 2% to 20%
Patients are also at risk for breast cancer, uterine and ovarian cancer, and early age cancer of the pancreas
This is a syndrome of multiple hamartomas including hamartomatous polyposis of the GI tract, with goiter and thyroid adenomas and increased risk of breast cancer and transitional cell carcinoma of the urinary tract
The syndrome is autosomal dominant and affects mainly Caucasians
Cowden disease
All patients have mucocutaneous lesions with facial papules, oral papillomas, and palmoplantar keratoses
A hamartomatous polyposis syndrome
This is a disease of older patients with a mean age of onset of 60 years
Polyps are distributed throughout the stomach, small bowel, and colon
Associated skin findings include nail atrophy, brownish skin pigmentation, and alopecia
Patients present with watery diarrhea and protein-losing enteropathy
Cronkhite-Canada syndrome
Lymphoid hyperplasia may involve the colon
The normal lymphoid follicular pattern of diffuse tiny nodules 1 to 3 mm in diameter with characteristic umbilication is most common where?
In the terminal ileum and cecum but may involve any portion of the colon
The nodular lymphoid hyperplasia pattern of diffuse nodules larger than 4 mm is associated with allergic, infectious, and inflammatory disorders
Most lymphomas of the colon are what of what type?
Non-Hodgkin B-cell lymphoma
Involvement of the cecum or rectum is most common with anal and rectal lymphoma frequent in AIDS patients
*Creator’s note:
Similar to SB lymphoma
Account for nearly all mesenchymal tumors of the colon
Gastrointestinal stromal tumors (GISTs)
True colonic leiomyomas and leiomyosarcomas are very rare
GISTs are much less common in the colon than in the stomach and small bowel
May appear as exophytic, mural, or intraluminal masses
Ulceration is relatively frequent
Hemorrhage, cystic change, necrosis, and calcification are more common in larger tumors
Most common submucosal tumor of the colon
It is most frequent in the cecum and ascending colon
Nearly 40% present with intussusception
Lipoma
Barium studies demonstrate a smooth, well-defined elliptical filling defect, usually 1 to 3 cm in diameter
The tumors are soft and change shape with compression
CT or MR demonstration of a fat density tumor is definitive
Extrinsic lesions that commonly cause mass effect on the colon that may simulate intrinsic disease
Endometriosis
Benign and malignant pelvic masses
Extrinsic inflammatory process (appendicitis, pelvic abscess, diverticular abscess, PID)
This is uncommon idiopathic inflammatory disease involving primarily the mucosa and submucosa of the colon
The disease consists of superficial ulcerations, edema, and hyperemia
Ulcerative colitis
What is the radiographic hallmarks of ulcerative colitis
Granular mucosa
Confluent shallow ulcerations
Symmetry of disease around the lumen
Continuous confluent diffuse involvement
In ulcerative colitis
What causes the granular pattern?
Early fine, granular pattern is produced by mucosal hyperemia and edema that precedes ulceration
A coarse granular pattern is produced later by the replacement of diffusely ulcerated mucosa with granulation tissue
In ulcerative colitis
After mucosal hyperemia and edema, what is the next tissue changes?
Superficial ulcers spread to cover the entire mucosal surface
The mucosa stippled with barium adhering to the superficial ulcers
In ulcerative colitis
These are deeper ulcerations of thickened edematous mucosa with crypt abscesses extending in the submucosa
Collar button ulcers
Late changes of ulcerative colitis
Late changes include a variety of polypoid lesions
Pseudopolyps are mucosal remnants in areas of extensive ulceration
In ulcerative colitis
Theses are small islands of inflamed mucosa
Inflammatory polyps
Postinflammatory polyps are mucosal tags that are seen in quiescent phases of the disease
In ulcerative colitis
These are postinflammatory polyps with a characteristic worm-like appearance
Filiform polyps
Pattern of involvement of ulcerative colitis
Involvement typically extends from the rectum proximally in a symmetric and continuous pattern
What happens to the terminal ileum in ulcerative colitis?
The terminal ileum is nearly always normal
Rare backwash ileitis may produce an ulcerated but patulous terminal ileum
CT findings of ulcerative colitis
- Wall thickening, often with “halo sign” of low- density submucosal edema
- Narrowing of the lumen of the colon
- Pseudopolyps, and pneumatosis coli with megacolon
Complications of ulcerative colitis
- Strictures, usually 2 to 3 cm or more in length and commonly involving the transverse colon and rectum
- Colorectal adenocarcinoma, with an approximate risk of 1% per year of disease
- Toxic megacolon (2% to 5% of cases) may be the initial manifestation
- Massive hemorrhage
Associated extraintestinal diseases of ulcerative colitis
Sacroiliitis mimicking ankylosing spondylitis (20% of cases)
Eye lesions including uveitis and iritis (10% of cases)
Cholangitis
Increased incidence of thromboembolic disease
Hallmark of Crohn colitis
- Early aphthous ulcers
- Later confluent deep ulcerations
- Predominant right colon disease
- Discontinuous involvement with intervening regions of normal bowel
- Asymmetric involvement of the bowel wall
- Strictures
- Fistulas
- Sinus formation
In Crohn disease
How is pseudodiverticula formed?
Pseudodiverticula of the colon are formed by asymmetric fibrosis on one side of the lumen, causing saccular outpouches on the other side
In Crohn disease
What is the rectal finding?
Involvement of the rectum is characterized by deep rectal ulcers and multiple fistulous tracts to the skin
Colonic disease that may be caused by a variety of bacteria (Salmonella, Shigella, Escherichia coli), parasites, viruses (cytomegalovirus, herpes), and fungi (histoplasmosis, mucormycosis)
Most cause a pancolitis with edema and inflammatory wall thickening with infiltration of pericolonic fat
Infectious colitis
Pericolonic fluid and intraperitoneal fluid may be present
This is a potentially fatal condition characterized by marked colonic distention and risk of perforation
It occurs as a complication of fulminant colitis often caused by ulcerative colitis, Crohn disease, pseudomembranous colitis, use of antidiarrheal drugs, and hypokalemia
Toxic megacolon
Transmural inflammation causes deep ulcers that may extend to the serosa surface, large areas of denuded mucosa, and loss of muscle tone
Radiographic finding of toxic megacolon
- Marked dilation 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 should be avoided because of risk of perforation
This is an inflammatory disease of the colon, and occasionally involving the small bowel, characterized by the presence of a pseudomembrane of necrotic debris and overgrowth of Clostridium difficile
Pseudomembranous colitis
Disease presents as fulminant inflammatory bowel disease with diarrhea and foul stools
Causes of pseudomembranous colitis
Antibiotics (any that change bowel flora)
Intestinal ischemia (especially following surgery)
Irradiation
Long-term steroids
Shock
Colonic obstruction
Conventional radiographs of pseudomembranous colitis
- Dilated colon
- Nodular thickening of the haustra
- Ascites
*Creator’s notes:
Nonspecific
Barium enema finding of pseudomembranous colitis
Irregular lumen with thumbprint indentations similar to ischemic colitis
Superficial ulcers are common
Plaque-like defects on the mucosal surface are due to the pseudomembranes
CT scan finding pf pseudomembranous colitis
- 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 (the “accordion sign”)
- Mild pericolonic fat inflammation disproportionate with the marked colonic wall inflammation
- Ascites (35%)
“Accordion sign” is seen on what disease?
Pseudomembranous colitis
Stripes of intraluminal contrast media trapped between nodular areas of wall thickening
Barium study finding of amebiasis
Aphthous ulcers Deep ulcers A symmetric disease Skip areas (mimic's Crohn colitis)
The cecum and rectum are the primary sites of colonic disease
The terminal ileum is characteristically not involved
Complications of amebiasis
Strictures
Amebomas consisting of a hard fixed mass of granulation tissue that may simulate carcinoma
Toxic megacolon
Fistulas, particularly following surgical intervention
Also known as neurtopenic colitis
This is a potentially fatal infection of the cecum and ascending colon usually seen in patients who are neutropenic and immunocompromised by chemotherapy
Typhilitis
Concentric, often marked, thickening of the wall of the cecum and ascending colon with prominent pericolonic inflammatory changes are characteristic
Patients are at risk for colon ischemia
Imaging finding of ischemic colitis
Early changes include thickening of the colon wall, spasm, and spiculation
As blood and edema accumulate within the bowel wall, multiple nodular defects are produced in a pattern called “thumbprinting”
CT demonstrates symmetrical or lobulated thickening of the bowel wall with an irregularly narrowed lumen
Submucosal edema may produce a low-density ring bordering on the lumen (target sign)
Air in the abnormal bowel wall (pneumatosis) is highly suggestive of ischemia
Diseases that is due to chronic irritation of the mucosa by laxatives including castor oil, bisacodyl, and senna
The involved colon may be dilated and without haustra, or narrowed
The right colon is most commonly affected
Bizarre contractions are often observed
The diagnosis is made by clinical history
Cathartic colon
Imaging findings of tubercolitis
- Marked thickening of the wall of the colon and terminal ileum
- Markedly enlarged lymph nodes, often with low central attenuation or calcification
- Common fistulae and sinus tracts
- Colitis may be segmental or diffuse
- Short strictures may mimic colon cancer
- Thickening of the peritoneum and extensive abdominal adenopathy suggest the disease
Findings mimic Crohn disease
These are pedunculated fatty structures that occur in rows on the external aspect of the colon adjacent to the anterior and posterior taenia coli
Epiploic appendages
They occur in greatest concentration in the cecum and sigmoid colon sparing the rectum
Epiploic appendagitis is caused by ischemic infarction of these structures, often resulting from torsion
CT finding of epiploic appendages
- 1- to 4-cm ovoid mass with central fat density and surrounding inflammation abutting the wall of the colon
- A hyperdense enhancing rim
surrounds the mass (“ring sign”) - Inflammatory changes may extend into the adjacent peritoneum
- A central high attenuation dot is often present representing the central thrombosed vessels
- Infracted tissue may eventually calcify
Ring sign is seen on what disease?
Epiploic appendagitis
This is an acquired condition in which the mucosa and muscularis mucosae herniate through the muscularis propria of the colon wall, producing a saccular outpouching
Colon diverticulosis
Diverticulosis without diverticulitis is a cause of painless colonic bleeding that may be brisk and life threatening
Colon diverticula are classified as true diverticula
True or false
False
Colon diverticula are false diverticula because the sacs lack all of the elements of the normal colon wall
Conventional abdominal radiographs findings of colonic diverticula
Gas-filled sacs parallel to the lumen of the colon
Barium study finding of colonic diverticula
Barium- or gas-filled sacs outside the colon lumen
Sacs vary in size from tiny spikes to 2 cm in diameter
Most are 5 to 10 mm in diameter
They may occur anywhere in the colon but are most common and usually most numerous in the sigmoid colon
Inflammation of diverticula, usually with perforation and intramural or localized pericolic abscess
Acute diverticulitis
Diverticulitis eventually complicates approximately 20% of the cases of diverticulosis.
Complications of acute diverticulitis
Obstruction
Bleeding
Peritonitis
Sinus tract and fistula formation
Diverticulitis is a less common cause of colon obstruction than is colon carcinoma
True or false
True
Obstruction due to diverticulitis is often temporarily relieved by smooth muscle relaxants such as glucagon
Colon bleeding is less often associated with diverticulosis than diverticulitis
True or false
False
Bleeding is more common in diverticulosis
Process of diverticular abscesses
What happens to them?
Most diverticular abscesses are quickly walled off and confined, but free perforation with pus and air in the peritoneal cavity and diffuse peritonitis may occur
Sinus tracts may lead to larger abscess cavities in the peritoneal or retroperitoneal compartments.
Fistulas are most common to the bladder, vagina, or skin, but may develop to any lower abdominal organ including fallopian tubes, small bowel, and other parts of the colon
Barium enema examination for acute diverticulitis is considered safe except on what cases?
When signs of free intraperitoneal perforation or sepsis are present
What are the hallmarks of diverticulitis on barium enema
Deformed diverticular sacs
Demonstration of abscess
Extravasation of barium outside the colon lumen
What is “double tract sign” and what disease is it seen?
Barium leaks into the abscess cavities, or forms tracks paralleling the colon lumen and often connecting multiple perforated sacs
Seen in acute diverticulitis
CT finding of acute diverticulitis
- Localized wall thickening
- Inflammation of pericolonic fat
- Pericolonic abscess
- Diverticula at or near the site of inflammation
- Common involvement of the adnexa with fluid collections and fistulae
Screening examination of choice for confirming the presence of, and often localizing, lower GI bleeding
Radionuclide imaging studies
Technetium-99m sulfur colloid or Tc-99m-red blood cell studies are capable of detecting bleeding at rates below 0.1 mL/min
Angiography requires bleeding rates of how many mL/min to be visualized?
0.5 mL/min or greater
Angiography is more specific than scintigraphy in demonstrating the anatomic cause of bleeding and offers the possibility of nonoperative treatment by embolization.
This refers to ectasia and kinking of mucosal and submucosal veins of the colon wall
The condition results from a chronic intermittent obstruction of the veins where they penetrate the circular muscle layer
Angiodysplasia
A maze of distorted, dilated vascular channels replaces the normal mucosal structures and is separated from the bowel lumen only by a layer of epithelium
