Lower GI Radiographic Appearances

Flashcards are designed to assist in memorizing key concepts related to lower GI radiographic appearances, including imaging modalities, findings, and diagnostic criteria.

What imaging studies are primarily used to diagnose and follow Crohn’s disease?

Small bowel contrast studies and CT.

Why are small bowel contrast exams useful in Crohn’s disease?

They help diagnose the disease and monitor progression.

What is the cobblestone appearance in Crohn’s disease?

An irregular mucosal pattern caused by alternating ulceration and edematous mucosa.

What does the string sign represent?

Severe narrowing of the bowel lumen due to inflammation and fibrosis.

Where is the string sign most commonly seen?

The terminal ileum.

What are skip lesions?

Diseased bowel segments separated by normal bowel.

Why are skip lesions important diagnostically?

They help differentiate Crohn’s disease from ulcerative colitis.

Why are fistulas common in Crohn’s disease?

Because inflammation involves all layers of the bowel wall.

What does bowel wall thickening on CT indicate in Crohn’s disease?

Inflammation and/or scarring.

What effect does bowel wall thickening have on the lumen?

It causes luminal narrowing.

Which procedures are used to diagnose ulcerative colitis?

Sigmoidoscopy and colonoscopy.

Why are sigmoidoscopy and colonoscopy effective for ulcerative colitis?

Because the disease originates in the rectum.

What imaging exam is used to assess disease progression in ulcerative colitis?

Large bowel contrast enemas.

What does mucosal damage look like on contrast enemas in ulcerative colitis?

An irregular mucosal wall.

What are collar button ulcers?

Small ulcerations extending into the mucosa.

What causes loss of haustral markings in ulcerative colitis?

Chronic inflammation and fibrosis.

What does narrowing of the lumen indicate in ulcerative colitis?

Fibrotic changes of the bowel wall.

What is meant by a 'stove pipe' or 'pipe stem' colon?

A smooth, featureless colon with loss of haustra.

What are pseudopolyps?

Islands of regenerating mucosa between ulcerated areas.

What imaging modalities are used for toxic megacolon?

Plain abdominal radiography and CT.

What is the key plain radiographic finding in toxic megacolon?

Marked dilation of the colon, most often the transverse colon.

What does pneumoperitoneum indicate in toxic megacolon?

Bowel perforation.

What is the purpose of the 3–6–9 rule?

To determine if the bowel is abnormally dilated.

What is the normal diameter of the small bowel?

Less than 3 cm.

What is the normal diameter of the large bowel?

Less than 6 cm.

What is the normal diameter of the appendix?

Less than 6 mm.

What is the normal diameter of the cecum?

Less than 9 cm.

What do measurements above the 3–6–9 rule suggest?

Bowel obstruction or paralysis.

Which imaging modality provides the most accurate bowel measurements?

CT.

What CT findings are seen in toxic megacolon?

Bowel dilation, loss of haustral markings, and bowel wall ulceration.

Why are barium studies contraindicated in toxic megacolon?

High risk of bowel perforation.

What imaging modality was traditionally used for diverticular disease?

Barium enema.

When are barium enemas safe in diverticular disease?

In diverticulosis without active inflammation.

When are barium enemas contraindicated?

In active diverticulitis.

What contrast is used instead during diverticulitis?

Water-soluble contrast.

What do diverticula look like on barium enema?

Outpouchings of contrast from the bowel wall.

What is the saw-tooth appearance?

Irregular bowel contour caused by fibrotic tissue replacing circular muscle.

What complications may be seen radiographically in diverticular disease?

Fistulas, abscesses, or perforation.

Why is CT preferred over enemas for diverticular disease?

It is more sensitive and can show inflammation.

What does CT demonstrate in diverticulitis?

Diverticula, bowel wall thickening, abscesses, fistulas, and perforation.

What imaging studies are used to evaluate volvulus?

Plain abdominal radiography, contrast enema, and CT.

What may a plain AP abdomen show in volvulus?

Gross bowel distension due to obstruction.

What classic sign is seen on contrast enemas in volvulus?

The bird’s beak sign.

What does the bird’s beak sign indicate?

The exact site of bowel twisting.

When should water-soluble contrast be used instead of barium?

When there is significant abdominal distension and risk of perforation.

What CT sign is diagnostic of volvulus?

The whirlpool sign.

Why is CT often preferred for volvulus?

It is better tolerated and clearly shows the twist.

What imaging modalities are used for intussusception?

Plain radiography, contrast enema, CT, and ultrasound.

What does a plain abdomen image show in intussusception?

Bowel obstruction and possibly an abdominal mass.

What is the cup-shaped or mushroom-cap filling defect?

Abrupt termination of contrast with a concave defect at the intussusception.

What is the coiled spring appearance?

Barium trapped between folded bowel walls.

What is the target or doughnut sign?

Concentric rings representing telescoped bowel segments.

What determines whether CT shows the actual telescoped bowel?

The plane of image reconstruction.

What imaging studies are used for imperforate anus?

Plain abdominal radiographs and horizontal beam lateral abdomen.

What is seen on plain abdominal images in imperforate anus?

Bowel obstruction and absence of air in the rectum and anus.

Why is a horizontal beam lateral done with the patient prone?

Air rises to the level of obstruction, outlining the atresia.

Why is a lead marker placed at the anus?

To measure the distance from the obstruction.

What defines a high rectal atresia?

Obstruction located more than 2 cm from the anal marker.

What defines a low rectal atresia?

Obstruction located less than 2 cm from the anal marker.

When are barium enemas used for colorectal carcinoma?

When colonoscopy is unsuccessful.

Why is a double-contrast barium enema preferred?

It detects both infiltrating and proliferating tumors.

How do all colorectal tumors appear radiographically?

As filling defects.

How do proliferating tumors appear?

As polyps or masses projecting into the lumen.

What appearance do infiltrating tumors have?

Apple core or napkin ring appearance.

What is a virtual colonoscopy used for?

Screening for colorectal cancer.

Why is contrast-enhanced CT used in colorectal carcinoma?

For staging and assessing recurrence.

What is trans-rectal ultrasound used for?

Rectal cancer staging and assessing bowel wall involvement.