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GIT IMAGING
Lecture 4
Barium follow through : is the standard contrast examination that involves drinking 200 – 300 ml
then taking films at regular intervals until the barium reaches the colon. It may take 2-3 hours.
The indications are:
1.inflammatory bowel disease (crhon's)
2.suspected stricture
3.malabsorption
4.enterocutaneous fistula
5.malrotation
6.post-small bowel resection
Enteroclysis (small bowel enema) is an alternative contrast procedure that distends the bowel with
excellent mucosal detail, but it involves intubation with a nasoduodenal tube through which barium is
injected and followed by water or methyl cellulose to propel barium through the bowel
CT scan using oral Gastrografin or water after 4-6 hours fasting can show thickening of bowel wall,
irregularity of mucosa and SB tumors
US and MRI has a limited role
Normal appearance of the small bowel
The normal SB occupies the central lower abdomen.
The terminal ileum enters the medial aspect of the cecum through the ileocecal valve.
Normal mucosa exhibit a feathery appearance.
The diameter of SB loop should not exceeds 3 cm .
Signs of disease of the small intestine
Dilatation: more than 3 cm e.g. paralytic ileus, malabsorption and SB obstruction
Thickened mucosal folds: e.g. edema, hemorrhage & inflammation
Stricture : e.g. Crohn's, TB and lymphoma
Ulceration: e.g. Crohn's, TB and lymphoma
Filling defect: tumor, polyp
Diverticulum:
Malrotation:
Crohn's disease
It is non-specific granulomatous inflammatory disease of unknown etiology, it nearly always
affect the terminal ileum or other several parts of the small and large intestine, leaving normal
intervening bowel, forming the skip lesions.
The major radiological signs on barium examinations are :
1.strictures(string sign) are variable in length
2.contraction of the cecum, this is seen with a diseased terminal ileum
3.dilatation of the bowel may be seen proximal to narrowed areas
4.ulcers :are quite deep. Fine ulceration + mucosal edema=cobblestone appearance
5.thickening,distortion and effacement of mucosal folds
6.separation of loops of bowel due to bowel wall thickening or an inflammatory mass
7.fistula to other loops of SB, colon, bladder or vagina
8.signs of malabsorption
Small bowel ischemia
A life threatening condition with thrombosis or embolus occlusion of the SMA producing thickening and mucosal edema,
may extend to perforate into the peritoneal cavity. The features are best demonstrated by CT scan.
Tuberculosis
Affects the ileocecal region indistinguishable from crohns, but sometimes with other associated features e.g. LAP and
peritoneal ascites
Lymphoma
Extremely difficult to differentiate from crohns , but other findings associated include: hepatosplenomegaly, enlarged
mesenteric LN, marked thickening of bowel loops and lymphomatous deposits in the liver and spleen .
Malabsorption
Definitive diagnosis is done by jejunal biopsy
The imaging signs include:
1.small bowel dilatation
2.thickening of mucosal folds
3.the barium may be diluted
Large intestine
Colonoscopy is now the gold standard for examining the colonic mucosa.
If the colonoscopist fails to reach the cecum, the large bowel may be investigated by performing
either a barium enema or a CT pneumocolon
Barium enema: bowel preparation is important to get rid of the fecal material, barium is run into the
colon under gravity, air is then blown in, to push the barium around the colon to give the double
contrast effect. Barium enema is helpful in extensive diverticular disease being prepared for
resection, colonic carcinoma, stricture, filling defect and ulceration.
CT pneumocolon: useful to identifying malignant tumors of the colon. A rectal tube is inserted and the
colon is distended with gas(CO2 or air). IV contrast agent is given to enhance any tumors that may be
present. Neither barium nor Gastrografin is used. CT pneumocolon images can be reconstructed to a
three-dimentional display and viewed as "virtual colonoscopy"
MRI has limited role in investigation of the colon due to movements artefacts from bowel peristalsis.
MRI is mainly used to evaluate the rectum and anal canal, where movement artefacts are minimal.
Imaging signs of disease of the large intestine
Narrowing of the lumen: may be due to spasm, stricture formation or compression by an extrinsic mass. Common
causes for stricture include: carcinoma, diverticular disease, crohn's disease and ischemic colitis
The following points should be assessed to diagnose the nature of stricture:
1.neoplastic strictures have shouldered edges, irregular lumen, are rarely> 6 cm
whereas benign strictures classically have tapered ends, a relatively smooth outline and may be of any length.
2.ulceration may be seen in strictures due to crohn's disease, and sacculation of the colon is a feature of
ischemic strictures
3.narrowing in diverticular disease is accompanied by other signs of diverticular disease and may appear similar
to neoplastic stricture
4.site of the stricture can help in diagnosis. Diverticular disease is usually confined to sigmoid. Ischemic
strictures are usually centered between the splenic flexure and sigmoid . Crohn's disease and TB have a
predilection for the cecum
5.extrinsic compression cause a smooth narrowing of the colon frequently from one side only and often
displaces the colon.
Dilatation: caused by obstruction, paralytic ileus, volvulus, ulcerative colitis with toxic megacolon and
Hirschprung's disease & megacolon
Filling defect: may be intraluminal, mural or extrinsic. In clean colon, a filling defect is likely to be a polyp
or an neoplasm. Feces may cause filling defect with no attachment to the wall and completely surrounded
by barium and freely mobile. Intramural hemorrhage, edema or air in wall all cause multiple smooth
defects arising from bowel wall. Intussusception causes a unique filling defect
Diverticula and muscle hypertrophy: are seen in diverticular disease
Ulceration: recognized as small projections from the lumen into the wall of the bowel in a fuzzy or shaggy
appearance. Caused mainly by ulcerative colitis & crohn's disease
Ulcerative colitis
Always involve the rectum, sometimes extends to involve the whole colon
Radiological signs:
1.widespread shallow ulcer is the cardinal sign. Ulcers may be deep in severe cases
2. widening of the presacral space due to peri-rectal edema
3. loss of the normal colonic haustra in the affected portions of the colon
4.narrowing and shorting of the colon giving the appearance of rigid tube
5.pseudopolyps ( swollen mucosa between ulcers) seen as filling defects
6.strictures are rare and likely to be due to carcinoma in longstanding disease
7.abnormal dilated ileum due to reflux through an incompetent ileocecal valve
8.toxic megacolon is a serious complication diagnosed by plain abdominal film or native CT. Due to
the risk of perforation, barium enema, colonoscopy and CT pneumocolon should be avoided
Crohn's disease of the colon
The colon may be the only part of the alimentary tract to be involved, but usually the disease affects
the small bowel if the colon is involved
Radiological signs of early stage of the disease are :
1.loss of haustration
2.narrowing of the lumen
3.shallow ulceration
4.cobblestone appearance, combination of mucosal edema and criss-crossing ulceration
Radiological signs of late stage of the disease are:
1.deep ulcers penetrating muscular layer (rose-thorn ulcers or deep fissures)
2.more extensive deep ulceration produce fistulae and abscess formation
3.strictures are common , smooth tapered ends
4.when involved the cecum is usually contracted
5.the disease may involve one portion of the circumference of the bowel
6.skip lesions are diagnostic feature
7.the rectum is often spared
8.ileocecal valve is normal or narrowed; terminal ileum stenosed
Diverticular disease:
Out-pouching of the mucosa through the muscular layer of the bowel wall
Very common particularly in adults, commonest in the sigmoid.
The diverticulae when filled with barium produce a spherical out-pouching with an narrowed neck
(diverticulosis), some pouches do not fill with barium when inflamed (diverticulitis) causing symptoms
such as sepsis, diarrhea or obstruction.
The colon may show "saw tooth serrated" appearance from muscle hypertrophy.
More extensive lesions produce perforation with fistulae into the bladder, SI or vagina,
Pericolic abscess and sometimes pneumoperitoneum.
A stricture may occur in an area of recognizable diverticular disease otherwise canot be differentiated
from carcinoma.
Ischemic colitis
Mucosal hemorrhage & edema cause indentations into the lumen of bowel (thumb prints)
A long smooth tapered ends stricture involving the splenic flexure with sacculations
Colorectal tumors
Polyps
Best investigated by endoscopy. May be sessile or on a stalk, single or multiple.
Features suggest malignancy are: size>2 cm, short thick stalk, irregular surface & rapid rate of growth.
Carcinoma
May arise anywhere in colon but commonest in rectosigmoid and cecum.
In rectosigmoid, it is often annular obstructing stricture whereas cecal carcinoma can become large
without obstruction.
A barium enema shows annular carcinomas as an irregular stricture with shouldered edges (apple-core
appearance), usually < 6 cm in length. The polypoid or fungating carcinoma causes an irregular filling
defect projecting into the lumen of the bowel.
Volvulus
Frequently seen in sigmoid and less often in cecum
The twisted loop becomes greatly distended and proximal bowel dilatation is noted
The diagnosis can be made from plain film
Ba enema will show smooth tapered narrowing with marked dilatation of proximal bowel
Intussusception
It is the invagination of one segment of the bowel into another. Infants and young children are
much more liable than adults. The commonest type is ileocolic. The diagnosis in children is often
made by US. In adults, it is almost always due to the presence of a neoplasm.