Colon (PBR 2)

Question 1

A term that is generic for a lesion that protrudes from the mucosal surface of the GI tract

Answer 1

Polyp

The term does not imply a histologic diagnosis

Question 2

This refers to radiolucency in a contrast media pool caused by a protruding mass lesion

Answer 2

Filling defects

On CT and barium enema examinations, filling defects maybe polyps, tumors, plaques, air bubbles, feces, mucus, or foreign objects

Question 3

“Bowler hats”

Answer 3

Polyps

*Creator’s notes
Remember BP

Question 4

Most common malignancy of the GI tract

Fourth most common malignant tumor

Answer 4

Colorectal adenocarcinoma

Question 5

Frequent or common locations of colorectal adenocarcinoma

Answer 5

Rectum and rectosigmoid area (50%)
Sigmoid colon (25%)
Remaining are evenly distributed throughout the remainder of the colon (25%)

Question 6

Morphologic patterns of colorectal adenocarcinoma

Answer 6

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)

Question 7

Most frequent/common complication of colorectal adenocarcinoma?

Answer 7

Obstruction

Other complications: 
Perforation
Intussusception
Abscess
Fistula formation

Question 8

Diseases that are at increased risk of colon carcinoma

Answer 8

Ulcerative colitis
Crohn disease
Familial adenomatous polyposis syndrome
Peutz–Jeghers syndrome

Question 9

Local staging of colorectal adenocarcinoma is best evaluated by what imaging method?

Answer 9

Transrectal or colonocopic US

CT and MR are used for more advanced disease and to detect recurrence

Question 10

Cross-sectional imaging findings of colorectal adenocarcinoma

Answer 10

1. Polypoid primary tumor (usually >1 cm)
2. “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
3. Linear soft tissue stranding into the pericolonic fat often indicative of tumor extension through the bowel wall
4. Enlarged regional lymph nodes (>1 cm) representing lymphatic spread of tumor
5. Distant metastases, especially in the liver

Question 11

Common locations of tumor recurrences

Answer 11

1. At the operative site, near the bowel anastomosis
2. In lymph nodes that drain the operative site
3. In the peritoneal cavity
4. In the liver and distant organs

Question 12

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?

Answer 12

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

Question 13

These polyps are nonneoplastic mucosal proliferations

They are round and sessile

Nearly all are less than 5 mm in size

Answer 13

Hyperplastic polyps

Question 14

These polyps are distinctly premalignant and a major risk for development of colorectal carcinoma

Answer 14

Adenomatous polyps

Approximately 5% to 10% of the population older than 40 years have adenomatous polyps

Question 15

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

Answer 15

Hamartomas polyps

Question 16

Polyps that are usually multiple and associated with inflammatory bowel disease

They account for less than 0.5% of colorectal polyps

Answer 16

Inflammatory polyps

Question 17

Polyposis syndrome in which colorectal cancer will eventually develop in nearly all patients

The inheritance pattern is autosomal dominant with high penetrance

Answer 17

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.

Question 18

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?

Answer 18

Gardner syndrome

Those with associated tumors of the central nervous system have been grouped as Turcot syndrome

These are variations of the same disease

Question 19

Diseases that cause hamartomatous polyposis syndrome

Answer 19

Peutz-Jeghers syndrome
Cowden disease
Cronkhite-Canada syndrome

Question 20

Dark pigmented spots on the skin and mucous membranes are characteristic of what hamartomatous polyposis syndrome?

Answer 20

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

Question 21

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

Answer 21

Cowden disease

All patients have mucocutaneous lesions with facial papules, oral papillomas, and palmoplantar keratoses

Question 22

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

Answer 22

Cronkhite-Canada syndrome

Question 23

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?

Answer 23

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

Question 24

Most lymphomas of the colon are what of what type?

Answer 24

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

Question 25

Account for nearly all mesenchymal tumors of the colon

Answer 25

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

Question 26

Most common submucosal tumor of the colon It is most frequent in the cecum and ascending colon Nearly 40% present with intussusception

Answer 26

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

Question 27

Extrinsic lesions that commonly cause mass effect on the colon that may simulate intrinsic disease

Answer 27

Endometriosis Benign and malignant pelvic masses Extrinsic inflammatory process (appendicitis, pelvic abscess, diverticular abscess, PID)

Question 28

This is uncommon idiopathic inflammatory disease involving primarily the mucosa and submucosa of the colon The disease consists of superficial ulcerations, edema, and hyperemia

Answer 28

Ulcerative colitis

Question 29

What is the radiographic hallmarks of ulcerative colitis

Answer 29

Granular mucosa Confluent shallow ulcerations Symmetry of disease around the lumen Continuous confluent diffuse involvement

Question 30

In ulcerative colitis What causes the granular pattern?

Answer 30

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

Question 31

In ulcerative colitis After mucosal hyperemia and edema, what is the next tissue changes?

Answer 31

Superficial ulcers spread to cover the entire mucosal surface The mucosa stippled with barium adhering to the superficial ulcers

Question 32

In ulcerative colitis These are deeper ulcerations of thickened edematous mucosa with crypt abscesses extending in the submucosa

Answer 32

Collar button ulcers

Question 33

Late changes of ulcerative colitis

Answer 33

Late changes include a variety of polypoid lesions Pseudopolyps are mucosal remnants in areas of extensive ulceration

Question 34

In ulcerative colitis Theses are small islands of inflamed mucosa

Answer 34

Inflammatory polyps Postinflammatory polyps are mucosal tags that are seen in quiescent phases of the disease

Question 35

In ulcerative colitis These are postinflammatory polyps with a characteristic worm-like appearance

Answer 35

Filiform polyps

Question 36

Pattern of involvement of ulcerative colitis

Answer 36

Involvement typically extends from the rectum proximally in a symmetric and continuous pattern

Question 37

What happens to the terminal ileum in ulcerative colitis?

Answer 37

The terminal ileum is nearly always normal Rare backwash ileitis may produce an ulcerated but patulous terminal ileum

Question 38

CT findings of ulcerative colitis

Answer 38

1. Wall thickening, often with “halo sign” of low- density submucosal edema 2. Narrowing of the lumen of the colon 3. Pseudopolyps, and pneumatosis coli with megacolon

Question 39

Complications of ulcerative colitis

Answer 39

1. Strictures, usually 2 to 3 cm or more in length and commonly involving the transverse colon and rectum 2. Colorectal adenocarcinoma, with an approximate risk of 1% per year of disease 3. Toxic megacolon (2% to 5% of cases) may be the initial manifestation 4. Massive hemorrhage

Question 40

Associated extraintestinal diseases of ulcerative colitis

Answer 40

Sacroiliitis mimicking ankylosing spondylitis (20% of cases) Eye lesions including uveitis and iritis (10% of cases) Cholangitis Increased incidence of thromboembolic disease

Question 41

Hallmark of Crohn colitis

Answer 41

1. Early aphthous ulcers 2. Later confluent deep ulcerations 3. Predominant right colon disease 4. Discontinuous involvement with intervening regions of normal bowel 5. Asymmetric involvement of the bowel wall 6. Strictures 7. Fistulas 8. Sinus formation

Question 42

In Crohn disease How is pseudodiverticula formed?

Answer 42

Pseudodiverticula of the colon are formed by asymmetric fibrosis on one side of the lumen, causing saccular outpouches on the other side

Question 43

In Crohn disease What is the rectal finding?

Answer 43

Involvement of the rectum is characterized by deep rectal ulcers and multiple fistulous tracts to the skin

Question 44

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

Answer 44

Infectious colitis Pericolonic fluid and intraperitoneal fluid may be present

Question 45

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

Answer 45

Toxic megacolon Transmural inflammation causes deep ulcers that may extend to the serosa surface, large areas of denuded mucosa, and loss of muscle tone

Question 46

Radiographic finding of toxic megacolon

Answer 46

1. Marked dilation of the colon (transverse colon >6 cm) with absence of haustral markings 2. Edema and thickening of the colon wall 3. Pneumatosis coli 4. Evidence of perforation Barium studies should be avoided because of risk of perforation

Question 47

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

Answer 47

Pseudomembranous colitis Disease presents as fulminant inflammatory bowel disease with diarrhea and foul stools

Question 48

Causes of pseudomembranous colitis

Answer 48

Antibiotics (any that change bowel flora) Intestinal ischemia (especially following surgery) Irradiation Long-term steroids Shock Colonic obstruction

Question 49

Conventional radiographs of pseudomembranous colitis

Answer 49

1. Dilated colon 2. Nodular thickening of the haustra 3. Ascites *Creator's notes: Nonspecific

Question 50

Barium enema finding of pseudomembranous colitis

Answer 50

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

Question 51

CT scan finding pf pseudomembranous colitis

Answer 51

1. Marked wall thickening up to 30 mm (average 15 mm) with halo or target appearance 2. Characteristic stripes of intraluminal contrast media trapped between nodular areas of wall thickening (the “accordion sign”) 3. Mild pericolonic fat inflammation disproportionate with the marked colonic wall inflammation 4. Ascites (35%)

Question 52

"Accordion sign" is seen on what disease?

Answer 52

Pseudomembranous colitis Stripes of intraluminal contrast media trapped between nodular areas of wall thickening

Question 53

Barium study finding of amebiasis

Answer 53

``` 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

Question 54

Complications of amebiasis

Answer 54

Strictures Amebomas consisting of a hard fixed mass of granulation tissue that may simulate carcinoma Toxic megacolon Fistulas, particularly following surgical intervention

Question 55

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

Answer 55

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

Question 56

Imaging finding of ischemic colitis

Answer 56

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

Question 57

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

Answer 57

Cathartic colon

Question 58

Imaging findings of tubercolitis

Answer 58

1. Marked thickening of the wall of the colon and terminal ileum 2. Markedly enlarged lymph nodes, often with low central attenuation or calcification 3. Common fistulae and sinus tracts 4. Colitis may be segmental or diffuse 5. Short strictures may mimic colon cancer 6. Thickening of the peritoneum and extensive abdominal adenopathy suggest the disease Findings mimic Crohn disease

Question 59

These are pedunculated fatty structures that occur in rows on the external aspect of the colon adjacent to the anterior and posterior taenia coli

Answer 59

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

Question 60

CT finding of epiploic appendages

Answer 60

1. 1- to 4-cm ovoid mass with central fat density and surrounding inflammation abutting the wall of the colon 2. A hyperdense enhancing rim surrounds the mass (“ring sign”) 3. Inflammatory changes may extend into the adjacent peritoneum 4. A central high attenuation dot is often present representing the central thrombosed vessels 5. Infracted tissue may eventually calcify

Question 61

Ring sign is seen on what disease?

Answer 61

Epiploic appendagitis

Question 62

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

Answer 62

Colon diverticulosis Diverticulosis without diverticulitis is a cause of painless colonic bleeding that may be brisk and life threatening

Question 63

Colon diverticula are classified as true diverticula True or false

Answer 63

False Colon diverticula are false diverticula because the sacs lack all of the elements of the normal colon wall

Question 64

Conventional abdominal radiographs findings of colonic diverticula

Answer 64

Gas-filled sacs parallel to the lumen of the colon

Question 65

Barium study finding of colonic diverticula

Answer 65

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

Question 66

Inflammation of diverticula, usually with perforation and intramural or localized pericolic abscess

Answer 66

Acute diverticulitis Diverticulitis eventually complicates approximately 20% of the cases of diverticulosis.

Question 67

Complications of acute diverticulitis

Answer 67

Obstruction Bleeding Peritonitis Sinus tract and fistula formation

Question 68

Diverticulitis is a less common cause of colon obstruction than is colon carcinoma True or false

Answer 68

True Obstruction due to diverticulitis is often temporarily relieved by smooth muscle relaxants such as glucagon

Question 69

Colon bleeding is less often associated with diverticulosis than diverticulitis True or false

Answer 69

False Bleeding is more common in diverticulosis

Question 70

Process of diverticular abscesses What happens to them?

Answer 70

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

Question 71

Barium enema examination for acute diverticulitis is considered safe except on what cases?

Answer 71

When signs of free intraperitoneal perforation or sepsis are present

Question 72

What are the hallmarks of diverticulitis on barium enema

Answer 72

Deformed diverticular sacs Demonstration of abscess Extravasation of barium outside the colon lumen

Question 73

What is "double tract sign" and what disease is it seen?

Answer 73

Barium leaks into the abscess cavities, or forms tracks paralleling the colon lumen and often connecting multiple perforated sacs Seen in acute diverticulitis

Question 74

CT finding of acute diverticulitis

Answer 74

1. Localized wall thickening 2. Inflammation of pericolonic fat 3. Pericolonic abscess 4. Diverticula at or near the site of inflammation 5. Common involvement of the adnexa with fluid collections and fistulae

Question 75

Screening examination of choice for confirming the presence of, and often localizing, lower GI bleeding

Answer 75

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

Question 76

Angiography requires bleeding rates of how many mL/min to be visualized?

Answer 76

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.

Question 77

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

Answer 77

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