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• There was a time when small-bowel follow-through (SBFT) was the
only and primary method of diagnosing diseases of the small bowel.
• Endoscopic methods for evaluating the small bowel, including
ileocolonoscopy, capsule endoscopy, and double- balloon enteroscopy,
offer distinct advantages for assessing superficial mucosal
abnormalities and obtaining biopsies for histologic assessment.
• However, endoscopic evaluation is invasive and may be limited by
bowel strictures, and techniques such as double-balloon enteroscopy
and wireless capsule endoscopy require special equipment and
expertise that are available only at large tertiary-care centers. Moreover,
no endoscopic technique allows assessment of extraenteric
• In recent years, there has been renewed interest in small bowel
imaging using a variety of techniques such as ultrasound(US),
contrast enhanced ultrasound (CEUS), computed tomography (CT),
magnetic resonance imaging (MRI), computed tomography
enteroclysis/enterography (CTEc/CTEg) and magnetic resonance
enteroclysis/enterography ( MREc/MREg) and the small bowel
• CT and MR enterography have proven superior to conventional
barium examinations since they provide essential information
about transmural and extramural involvements, and about the
complications that may determine surgical treatment (obstruction,
• CT enterography was first introduced by Raptopoulos et al in
1997 as a modification to ‘‘standard’’ abdomino-pelvic CT
examination to specifically examine the small bowel in detail,
notably to assess the extent and severity of Crohn’s disease.
• They combined neutral (low-density) oral contrast with ‘‘enteric
phase’’ CT to optimise contrast resolution between mucosa and
lumen, thereby maximising conspicuity of abnormalities
arising from the small bowel wall.
• Several authors have subsequently described similar
techniques, which are broadly categorised into:
– CT enterography (where patients drink oral contrast) and
– CT enteroclysis (luminal contrast is introduced via a
nasojejunal tube placed fluoroscopically prior to CT
• Although superior jejunal distension is attained using enteroclysis,
the convenience, efficiency and superior patient experience
achieved with CT enterography make it the preferred technique at
The CT-enteroclysis is a moderately reproducible examination because
small-bowel distension is the major difficulty.
It depends on the probe position, which is not always optimal, intestinal
peristalsis, and reabsorption of the opacifying contrast agent.
Furthermore, it is an irradiating exam that is uncomfortable for the
For this reason, many teams perform CT-enteroclysis without a probe,
which requires slow and progressive ingestion of the contrast agent,
providing less complete distension, probably limiting the detection of
CT enteroclysis is complementary to capsule endoscopy in the
elective investigation of small-bowel disease, with a specific role in
the investigation of Crohn disease, small-bowel obstruction , and
unexplained gastrointestinal bleeding.
CT enteroclysis is considered significantly superior to conventional
enteroclysis in depicting Crohn disease associated intra- and extra-
mural abnormalities .
The patient should not have eaten solid food for 8 h.
Water should be authorized so as to reduce the phenomenon of water
resorption by the small intestine during intestinal infusion, which
increases with dehydration.
• Metoclopramide (10 mg)
– given orally 75 minutes before the CT scan
– stimulates gastric emptying.
• Glucagon (1 mg) OR Buscopan (20mg)
– administered intravenously immediately prior to
– decrease small bowel peristalsis.
• The technique of CT enterography combines
– small bowel distension with a neutral or low-density oral contrast
– abdomino-pelvic CT examination during the enteric phase
following administration of intravenous contrast.
• Patients drink approximately 1.5–2 l of oral contrast over
• Patient compliance is central to the success of CT enterography, and
supervision and encouragement during the drinking phase is
• Optimising luminal distension will facilitate rapid and efficient luminal
navigation, enabling accurate detection and characterisation of
In CT enteroclysis an enteroclysis catheter is used.
It is a 13-F catheter with a 150 cm long, with 2.8-mm external
diameter and 2.1-mm internal diameter and a distal balloon that
prevents gastroduodenal reflux. The balloon is inflated with 20– 25
ml of air and fixed in Treitz’s angle.
The catheter is placed with fluoroscopic guidance. Patients tolerate
nasal passage in a seated position better than oral passage because the
gag reflex is avoided.
Luminal contrast and distension
• Neutral or low-density oral contrast media are a
prerequisite for good-quality CT enterography because:
– they maximise contrast between the lumen and
enhancing small bowel wall,
– facilitating assessment of mucosal thickening and
wall stratification/enhancement patterns
– inexpensive, well tolerated by patients, and effective for
distending the stomach, duodenum, and jejunum.
– inadequate distension due to rapid reabsorption.
• polyethylene glycol (PEG) electrolyte solution
– Gastrointestinal side-effects.
• 0.1% w/v ultra-low-dose barium with
• sorbitol, a nonabsorbable sugar alcohol
– promotes luminal distention and
– limits resorption of water across the length of the small bowel.
– The attenuation of low-concentration barium is only 20 HU.
– Fewer side effects than are associated with PEG.
– Unpleasant taste & loose bowel movements or diarrhea very
soon after the scan
• Positive oral contrast agents (containing iodine or barium)
– not routinely used for CT enterography
– they obscure mucosal enhancement, intraluminal haemorrhage and
assessment of subtle mural disease.
– problematic in creating three-dimensional images if CT
angiography is concurrently being performed—for example, in the
assessment of gastrointestinal blood loss.
• May be preferred for some clinical situations
– establish fistula patency
– exact site of mechanical obstruction
– known serosal disease,
– detection of some primary tumors, and
– patients with an iodine allergy.
A volume of less than 1.5L is unlikely to be sufficient to adequately
distend the small bowel without active inflammation, and a subcentimetre
mass could be missed; although,according to many authors, good-quality
examinations can be achieved with smaller volumes.
In enteroclysis Intestinal filling takes place with an electrical pump
which provides homogenous and good-quality opacification, a high and
constant flow rate, and excellent safety because pressure and flow rate
can be monitored and regulated permanently. The flow rate chosen should
be from 180 to 200 mL/min, with 2 L of contrast agent.
• For the evaluation of the upper small intestine only,
– patients drink a total of two 450-mL bottles of the agent, with a 10-
minute interval between each bottle.
– Water achieves the same results, is less expensive, and is better
tolerated by patients.
• For the evaluation of the complete small intestine,.
– Patients are given three 450-mL bottles, each of which is consumed
at about 15-minute intervals. The last 150 to 200 mL is consumed
just before the patient gets on the scanner.
• In small patients and patients with history of previous
small bowel resection
– smaller volumes of oral contrast may be sufficient, judged
mainly by patient tolerance.
• In addition, intravenous contrast is an essential component of CT
• It enables evaluation of:
– wall thickening,
– mucosal enhancement,
– the supplying and draining blood vessels, and
– the presence or absence of GI bleeding.
• 100 to 125 mL of intravenous contrast at a rate of 3 to 5 mL/sec,
initiating the scan acquisition after a 60-second delay.
• Maximal small bowel enhancement on MDCT has been reported
by Schindera et al to be 50 s after administration of intravenous
contrast or 14 s after aortic peak enhancement.
• Therefore administer contrast intravenously during this enteric
• The enteric phase is similar to the pancreatic phase; therefore, CT
enterography also optimises demonstration of most pancreatic
• This is particularly relevant for clinicians, given that symptoms of
pancreatic tumour can mimic luminal disease.
• However, lack of portal venous phase imaging is rarely a problem
for patients undergoing CTE because subtle liver metastases are
rarely the target of imaging in this patient group.
• Acquisition of both arterial and venous phase images at
30s and 60s respectively.
• The arterial phase images are critical for:
– appreciating bowel wall for mucosal hyperenhacement
– engorgement of the adjacent vasa recta, all of which are
important signs of bowel inflammation.
• The venous phase images are important not only for
– evaluating the bowel, but also the
– other parenchymal organs of the abdomen (i.e., liver, spleen,
– the extraenteric manifestations of Crohn’s disease,
– the venous mesenteric vasculature, and
– hypovascular bowel tumors.
CT acquisition with no injection of iodated contrast medium should be
done after intestinal filling, unless perfusion has failed, in order to
check the catheter position when monitoring irradiation.
Images are acquired with thin collimation, with acquisition of 0.625-
0.75 mm slices, which are then reconstructed into 3-5 mm axial
slices for routine interpretation.
Coronal and sagittal multiplanar reconstructions are directly created at
the CT scanner following the acquisition of the axial source images.
At the same time, isotropic 0.5-0.75 mm images are used for 3-D post-
• Two separate sets of 3-D reconstructions:
– Maximum intensity projection (MIP) imaging
• Effective for evaluation of the mesenteric vasculature
• Not only the main aortic branch vessels, but also tiny
mesenteric branches which are typically not readily
visualized on the axial source images.
• Areas of bowel hyperemia and mesenteric vascular
engorgement (i.e., “comb sign”, opacification of the vasa
recta) are also easily identified using this technique;
– Volume rendering (VR)
• most useful in displaying the entirety of the small bowel, and
illustrating the relationship of adjacent small bowel loops,
subtle areas of bowel wall thickening, abnormal mucosal
enhancement, and extra-enteric manifestations of Crohn’s
• To avoid intravenous contrast-induced nephropathy,
– limit the use in frail and diabetic patients.
– consider reducing the volume of intravenous contrast,
– ensure patients are well hydrated before the examination and
– monitor renal function closely afterwards.
• A large volume of oral contrast is contraindicated
– who are fluid-restricted owing to clinical conditions such as
renal or heart failure.
• Following CT enterography examination, patients are encouraged
to remain in the radiology department for approximately 45 min
because they reasonably frequently experience severe, or short-
Variations to the basic protocol -
• In patients where active gastrointestinal bleeding is suspected
(and endoscopic work-up is negative) a multiphase scan
protocol can be used to identify sites of occult gastrointestinal
• This protocol would frequently include pre-contrast, arterial,
venous and delayed phase CT examinations of the abdomen and
• Rarely, this can be used in emergency situations to
identify the site of bleeding.
• However, the radiation burden is approximately three times
higher, and therefore potential radiation risks should be
balanced against patient benefit.
LOW-DOSE CT TECHNIQUE
• peak incidence of Crohn’s disease is in patients between the
ages of 20-40 years;
• a sizeable percentage of cases are diagnosed in children (15%);
• the disease has a mild female predominance i.e. radiation
• These include
– Automated tube current modulation, which alters the tube
current (mAs) based on the patient’s size and density;
– Automated tube potential modulation, which alters the
scanner’s tube potential (kVp) based on the patient’s size
and density; and
– Iterative reconstruction, an alternative to traditional filtered
back projection reconstruction techniques, which allows the
acquisition and reconstruction of diagnostic quality images
at far lower radiation doses
In general, CT-enteroclysis also extends the duodenum by reflux and,
with good distension, the normal wall measures approximately 1 mm.
The different normal layers of this wall are not visible. This wall hosts a
great number of folds. The duodenal papillae and mucous anomalies are
not visualized by CT-enteroclysis.
The small bowel wall’s normal thickness varies greatly depending on
The wall is sometimes barely visible or less than 1 or 2 mm if distension
is substantial. It appears thicker (3-4 mm) when the intestine is flat or
only slightly distended.
Axial and Coronal images of normal CT-
enteroclysis, with optimal and homogenous
Filling was done with a mannitol-based
The false-positive results generally correspond to partial volume
effects of the valvulae conniventes, intestinal spasms, and functional
It seems that invagination is very difficult to demonstrate because its
analysis is highly subjective and there is no reference method to
It can be confused with simple intestinal contraction or an intestinal
fold , but not with organic invagination because it does not result in
It is therefore indispensable to take multiplanar reformations to limit
Example of a false-positive result:
a. Pseudothickening of the bowel wall at
the left flank (arrow),
b. Actually corresponding to an intestinal-
jejunal fold when the loop is uncoiled with
multiplanar reformations (arrow).
Example of a false-positive result: Pseudotarget of a
loop at the left flank (arrow) corresponding to a
jejunal valvulae conniventes.
Example of a false-positive
a Example of functional jejunal
invagination or intestinal spasm
appearing as a stenosing wall
thickening after injection of
iodinated contrast product.
b Analysis of the other
acquisition phases can
eliminate the nonpathological
aspect of this image because it
Example of false-positive result
for a tumor (arrow):
a axial view,
b oblique view.
Chronic intestinal bleeding
The performance of CT-enteroclysis in diagnosing obscure intestinal
bleeding is poor because in this indication, the most frequently found
lesions in decreasing order of frequency are :
i. Arteriovenous malformations (or angiodysplasia) , very frequent
after 50 years of age,
ii. Ulcerations secondary to NSAIDs,
There is no precise consensus on the best diagnostic strategy in these
situations of obscure chronic intestinal bleeding. However, age plays an
important role in the diagnostic decision.
Chronic intestinal bleeding and tumors after 50 years of age
It is recommended to begin with an esogastroduodenoscopy and a
colonoscopy, then if these exams are negative, a videocapsule
recording is indicated.
After the age of 50, CT-enteroclysis has a very minor place since
angiodysplasia is frequently the cause of bleeding and this is not
detected on CT. However, CT-enteroclysis is often done before
videocapsule endoscopy because it can verify the absence of stenosis
that may block the capsule.
Chronic intestinal bleeding and tumors before 50 years of age
CT-enteroclysis comes after gastroscopy and colonoscopy because a
bowel tumor must be sought first and foremost, with angiodysplasia
less frequent at this age.
The best indications come from carcinoid syndromes and digestive
tract hemorrhage syndromes recurring over several months with
negative gastroscopy and colonoscopy.
CT-enteroclysis is a technique that can detect tumors less than 1 cm
Acute digestive tract bleeding
In an emergency situation, videocapsule endoscopy has no place
because it lasts 8 h and its progression depends on peristalsis. In
addition, if the patient is in hemorrhagic shock this exam is not
Therefore, CT enteroclysis and/or the double-balloon enteroscope
On the contrary, when the patient is doing well, videocapsule
endoscopy can easily be performed.
CT enteroclysis seems to be an indisputable, high-performance
technique in detecting small-bowel tumors as long as optimal
intestinal distension is obtained.
In staging tumors, small-bowel tumors present a diagnostic
difficulty for both the clinician and the radiologist because they are
rare (<5% of tumors of the digestive tract), their nonspecific
symptoms delay diagnosis, and in particular their small size at the
initial evolving stage.
CT enteroclysis can differentiate between epithelial and conjunctive
Malignant tumors concern the
GISTs with malignancy criteria
Type B or T lymphomas are born of lymphoid tissue.
Carcinoid tumors are neuroendocrine tumors.
Metastases appear either from intrinsic involvement (peritoneal
carcinomatosis) or hematogenic involvement .
Most frequent malignant tumors are stromal tumors (GISTs),
adenocarcinomas and lymphomas.
Lipomas are the most frequent benign tumors.
Hypervascular lesions generally correspond to carcinoid tumors,
stromal tumors, or certain metastases.
The adenocarcinomas enhance less intensely and are often
stenosing. Lymphomas, on the other hand, enhance very little and
are associated with multiple adenopathies.
Lipomas are very easy to identify on CT because of their
Circumferential thickening of the jejunum with aneurysmal dilatation and low enhancement
after injection and therefore highly suggestive of lymphoma. The double-balloon enteroscope
and the pathological report nevertheless diagnosed mucinous adenocarcinoma.
CT and endoscopic aspect (videocapsule)
of an adenocarcinoma of the
jejunum appearing as budding and
Peutz-Jeghers syndrome. CT-enteroclysis demonstrated several ileal polyps
Example of a single fibrous polyp on CT-enteroclysis and endoscopic
Lipoma of the
in a digestive
Ileal stromal tumor revealed by abdominal
pain. The tumor’s characteristics are seen
a Budding endoluminal mass,
b Hypervascular heterogeneous mass with
large feeding artery,
c A few necrotic areas and intralesional
Voluminous ileal stromal tumor on CT-
enteroclysis: budding endoluminal mass,
hypervascular heterogeneous mass with
large feeding artery.
Type B ileal lymphoma seen as a
homogenous thickening of the wall with
regular contours and little enhancement,
confirmed by surgery.
Ileal endoluminal carcinoid tumor (arrows) corresponding to
stenosing hypervascular wall thickening.
Videocapsule endoscopy found an oval submucous ileal nodule.
Rectal adenocarcinoma metastasized to the jejunum (arrows): spiculated
tumor, slightly vascularized.
CT enteroclysis showing a strongly enhanced poorly outlined tumour located in
the lumen of the jejunum with Metastasis to the lymph node (small arrow) and
Metastases to the liver (arrows).
The most frequent inflammatory involvement of the small bowel is
Crohn disease: chronic ulcerous and stenosing granulomatous
progression in the young adult most often found in the terminal
CT is a reference technique to study wall thickening, abdominal fat,
and the complications of inflammatory disease of the small bowel
with a strong impact on patient management.
Skip lesions in Crohn disease. Axial CTE section depicts two inflammatory small
bowel strictures (arrows) separated by a segment of normal distended small bowel
(arrowheads), characteristic findings of Crohn disease.
Manifestations of active Crohn disease. (2a) Axial CTE section shows mucosal
hyperenhancement (black arrow) and mural stratification (white arrow) of the terminal
ileum, an appearance that contrasts markedly with that of nondiseased ileal segments
(*). (2b) Axial CTE section from another patient shows mesenteric hypervascularity
(arrowheads) adjacent to the involved bowel segment.
Fistula formation in Crohn disease. Coronal volume-rendered CTE sections
obtained in two patients depict ileo-ileal fistulas (arrowheads in a) and an
ileocolonic fistula (arrow in b).
Coronal volume-rendered CTE sections from two patients (a and b) demonstrate
prominence of the vasa recta, or “comb sign” (arrows).
Crohn disease complicated with terminal ileitis:
Submucous edema and mucous uptake of contrast medium
responsible for the target aspect.
On CT, diverticulum generally corresponds to an extraluminal
image, rounded, with a fluid, gas, or fluid-gas content,
communicating with the intestinal lumen.
On CT-enteroclysis, diverticula more often appear as fluid since they
fill simultaneously with the intestinal loops.
Congenital diverticula are more frequently found on the
antimesenteric edge than acquired diverticula found on the
mesenteric edge where the vessel penetrates .
a axial view,
b coronal view.
Meckel diverticulum is inconstant and rare since it is found in only
2% of autopsies.
It is most often asymptomatic and is manifested by its hemorrhagic,
inflammatory, occlusive, and tumoral complications.
In CT-enteroclysis abundant filling of the small intestine loops by
enteroclysis theoretically easily distinguishes between diverticulum
and intestinal loop.
Merckels diverticulum seen by by
Confirmed by surgery
In cases of low-grade occlusion, the ingestion of contrast product or
its injection in the nasogastric catheter before the CT examination
makes it possible to differentiate incomplete occlusions that can be
treated medically from complete surgical occlusions.
However this examination must be done with a double-function
catheter (infusion and aspiration) to avoid any problems.
However, this practice is debatable since it increases endoluminal
pressure in a static intestine with possible microbial proliferation
and a consequential risk of septic discharge.
• CT enterography will continue to be incorporated into wider
clinical measures of Crohn’s disease, particularly given the
promise that objective CT findings such as mural
hyperenhancement can be quantitated.
• Continuing technical developments in CT image
reconstruction will substantially reduce the radiation dose at
CT enterography, which is already the same or less than
routine abdominal CT.
• The use of dual-source CT systems will permit wider use
of low-energy CT scanning, which will
– increase the conspicuity of hypervascular
– permit further radiation dose reduction.
A. Normal CT
B. With 140 kV
C. With 80 kV tube
Low-Dose 18F-FDG PET/CT Enterography
• Low-dose 18F-FDG PET/CTE, compared with CTE, may
improve the detection and grading of active inflammation in
patients with Crohn disease.
CTE demonstrates mural thickening and mucosal enhancement in loop of ileum (arrow) involved with Crohn
disease. Corresponding 18F-FDG uptake is seen on PET. Excellent anatomic registration of PET and CTE
findings on PET/CTE
PET/CTE also may reveal clinically significant findings, such as
enterocolic fistula, not evident on PET or CTE alone.
Axial CTE image (A) demonstrates thickened loop of ileum (white arrow) in pelvis and unremarkable adjacent
loop of sigmoid colon (black arrow). No fistula was appreciated on CTE.
Corresponding 18F-FDG PET image (B) reveals increased tracer uptake in ileum (arrow) consistent with active
Crohn disease; however, anatomic detail is insufficient to suggest enterocolic fistula.
Fused PET/CTE image (C) clearly demonstrates 18F-FDG uptake (arrow) bridging ileum and sigmoid colon,
with focal uptake present in wall of sigmoid colon. PET/CTE diagnosis of enterocolic fistula was confirmed at