The document discusses advancements in imaging techniques for ulceroconstrictive diseases of the gut, emphasizing the transition from traditional methods like plain radiographs and barium studies to modern approaches such as CT enterography and MRI. It details various imaging modalities' effectiveness in diagnosing gastrointestinal conditions including tuberculosis and inflammatory bowel diseases. Notably, it highlights the diagnostic advantages of newer techniques in assessing bowel strictures and distinguishing between active inflammation and fibrotic changes in conditions like Crohn's disease and ulcerative colitis.

1. Ulceroconstrictive
Diseases of the Gut

2. INTRODUCTION
• Imaging in ulceroconstrictive lesions of the gut has seen a
paradigm change over the last few decades.
• While earlier conventional imaging studies relied
predominantly on the luminal distension and opacification
of the bowel lumen using positive oral contrast; newer
modalities such as CT and MRI are capable of providing
information on both intraluminal, as well as extrinsic
abnormalities.
• CT enterography (CTE) and MR enterography (MRE) are
unique imaging techniques having the combined
advantages of both CT/MRI and enterography.

3. Plain Radiograph
• The role of plain radiographs has diminished to a great
extent because of the wider availability of crosssectional
modalities.
• They are useful only in a patient with acute or subacute
intestinal obstruction,and presence of
pneumoperitoneum when they are often the first line
modality.
• Enteroliths can be seen sometimes proximal to the site
of obstruction and presence of calcified lymph nodes
can point towards the diagnosis of tuberculosis (TB).

4. Barium Studies
• BMFT, along with colonic evaluation by barium
enema, can give valuable information regarding
both small and large bowel obstructive lesions.
• It is the best imaging technique to evaluate the
mucosal details of small and large bowel.
• There are many classical signs described for TB and
Crohn's disease (CD) on barium studies and they
are good in demonstrating bowel narrowing,
dilatation, mucosal ulcerations, kinking and
clumping of bowel loops and fistulae

5. • Ileocecal TB on barium studies: Barium meal follow through (BMFT) image (A) shows narrowing and
mild mucosal irregularity (thin arrow) in the terminal ileum (string sign) with associated contracted
cecum (thick arrow).
• BMFT image (B) of another patient shows narrowing of terminal ileum which is emptying directly
into ascending colon (outlined arrow) with nonvisualization of cecum (Stierlin's sign).
• BMFT image (C) in a different patient shows fibrotic stricture in the terminal ileum (thin arrow) with
proximal dilatation (star) and contracted cecum.
• BMFT image (D) of another patient shows mild gaping (thin arrow) and filling defect (outlined
arrow) in the region of ileocecal valve (Fleischner's sign) due to edema of the valve.

6. • Single contrast BMFT is usually performed with barium
suspension having 66% w/v barium.
• The major drawback in the evaluation of intestinal strictures by
BMFT is the differentiation of a true stricture from a transient
peristaltic contraction.
• In order to alleviate this drawback, enteroclysis (small bowel
enema) came into practice; wherein the small bowel lumen is
distended through a nasojejunal tube and using diluted barium.
• Enteroclysis yielded superior mucosal details compared to BMFT.
Also, as the distension of bowel lumen was controlled and the
luminal distension was visualized in real-time; this technique was
superior to BMFT in the detection of subtle intestinal strictures.
• However, this technique entails ionizing radiation to the patient
and the yield is also poor when compared with CTE or MRE.
Hence, barium studies should be used only if CT or MR
enterography is not available.

7. • Single contrast barium enema and double contrast
barium enema (DCBE) are two other important
barium studies.
• While single contrast BE is adequate for delineating
the strictures in the large bowel;
• DCBE is preferable in cases of suspected mucosal
lesions such as in ulcerative colitis. However,
colonoscopy is the primary modality of choice in
the evaluation of patients with ulcerative colitis

8. CECT and CT Enteroclysis/CT Enterography
• Contrast-enhanced CT (CECT) is the workhorse of imaging in
suspected intestinal strictures.
• CT enteroclysis combines the benefits of the two,imaging modalities;
good luminal distension similar to a conventional enteroclysis and
visualization of extraluminal/transmural pathologies similar to CECT.
• CT enterography (CTE) is a newer imaging technique wherein the
luminal distension of small bowel is achieved without a nasojejunal
tube
• In this procedure either diluted mannitol/ polyethylene glycol
solution (PEG) is used as neutral oral contrast agent to distend the
bowel loops.
• Radiation dose of a standard CTE study is around 15 mSv compared
to 3-8 mSv for BMFT

10. MRI/MR Enterography
• Although CECT can provide a lot of diagnostic information in
intestinal strictures; it comes with a high radiation burden
• MRI has the advantage of superior soft tissue contrast resolution;
multiplanar imaging capability and lack of any ionizing radiation.
• new ultrafast sequences (True FISP – Cine MR) have made the
real time evaluation of the small bowel possible; which is crucial
for differentiating a stricture from a peristaltic contraction.
• The active lesions tend to show restriction of diffusion
(hyperintense signal on high b value images).
• DWI can be an effective alternative to IV Gadolinium in the
evaluation of lesion activity in inflammatory bowel diseases in
patients in whom Gadolinium based contrast is contraindicated.

11. Ultrasonography and Contrast-
enhanced Ultrasonography
• High-resolution US is an emerging technique to evaluate
bowel disorders and it is very sensitive in detecting bowel
wall abnormalities in the terminal ileum and ileocecal
junction region.
• The spatial resolution of high resolution US is better than
CTE or MRE and it can show wall thickening, dilated
segment of bowel loop and bowel motility in real time.
Increase in bowel and mesenteric vascularity can be
detected on Doppler which is considered as a marker for
disease activity in CD.

12. • Contrast enhanced ultrasonography (CEUS) is a
recent advancement which has been evaluated and
recommended in the evaluation of disease activity in
inflammatory bowel diseases, distinguishing fibrous
from inflammatory strictures, abscesses, and fistula.
• It utilizes a special contrast agent such as sulfur
hexafluoride microbubbles which is given intravenously
to look for areas of abnormal enhancement.
• It can be used even in patients with renal impairment
as the mode of excretion is via breath.

13. ABDOMINAL TUBERCULOSIS
• Abdominal TB constitutes about 17% of all inpatients
admitted with the diagnosis of TB.
• Intestine is the sixth most common of all the
extrapulmonary sites involved by TB.
• TB is caused by Mycobacterium tuberculosis and
abdominal TB generally includes involvement of
gastrointestinal tract, lymph nodes, peritoneum and
solid visceral organs of abdomen.

14. Gastrointestinal Tuberculosis
• GI TB can present either with symptoms related to
bowel like abdominal pain,vomiting, diarrhea and
abdominal distension or systemic symptoms like fever,
loss of appetite and weight.
• TB can involve any part of the gastrointestinal tract, but
ileocecal region is most commonly involved (50–90%).
• Ileocecal TB has three morphological types—ulcerative
(60%), hypertrophic (10%) and ulcerohypertrophic
(30%).
• Spasm, hypermotility, mucosal edema, edema of the
ileocecal valve are the earliest signs of ileocecal TB.

15. • Ileocecal TB on barium studies: Barium meal follow through (BMFT) image (A) shows narrowing and
mild mucosal irregularity (thin arrow) in the terminal ileum (string sign) with associated contracted
cecum (thick arrow).
• BMFT image (B) of another patient shows narrowing of terminal ileum which is emptying directly into
ascending colon (outlined arrow) with nonvisualization of cecum (Stierlin's sign).
• BMFT image (C) in a different patient shows fibrotic stricture in the terminal ileum (thin arrow) with
proximal dilatation (star) and contracted cecum.
• BMFT image (D) of another patient shows mild gaping (thin arrow) and filling defect (outlined arrow) in
the region of ileocecal valve (Fleischner's sign) due to edema of the valve.

16. • Cecum is
pulled out of
the right iliac
fossa which is
often
referred to as
pulled up
cecum
Pulled up cecum: Axial CTE image (A) oblique MPR (B) and sagittal MPR (C) showing
wall thickening and abnormal enhancement involving the cecum (thin arrow) with few
enlarged regional lymph nodes(thick arrow). The cecum is contracted and has migrated
cranially to the right lumbar region suggestive of pulled up cecum in a patient with
ileocecal TB.

17. • High resolution US can also show changes of GI TB
in the form of abnormal wall thickening (>3 mm in
distended state and >5 mm in collapsed state),
inflammation in the surrounding mesentery and
enlarged lymph nodes which may have calcification
and necrosis.
• Bowel wall thickening is a nonspecific finding which
can be seen in Crohn's disease, lymphoma,
amoebiasis and carcinoma.

19. • Ileocecal TB: Axial CECT image showing circumferential wall thickening
involving the cecum (thin arrow) with surrounding fat stranding and enlarged
lymph nodes (outlined arrow). The above features are suggestive of TB.

20. • In the early stage CTE may show nonspecific
inflammatory changes in the form of stratified wall
thickening in distal ileum, ileocecal junction and
cecum which can later progress to more severe
homogeneous wall thickening and narrowing
leading to obstruction

21. • Fibrotic stricture in TB: CTE images (A and B) and MRE images (C and D)
showing circumferentialwall thickening involving the terminal ileum and ileocecal
junction (thin arrow) causing mild proximal obstruction. The wall thickening is
hypointense on T2-weighted image (C) and showing homogeneous enhancement
on postcontrast image (D) suggestive of fibrosis.

22. • Small bowel obstruction with enteroliths: Axial CECT image (A) and
coronal MPR (B) show a short segment ileal stricture (outlined arrow).
• There is marked proximal dilatation of small bowel with air-fluid level (star)
suggestive of small bowel obstruction. Also noted is presence of multiple
enteroliths (thin arrow).

23. • Axial CECT and coronal MPR image showing clumped dilated
proximal jejunal loops which are encapsulated by a thick membrane
(outlined arrow) all around suggestive of sclerosing encapsulating
peritonitis (cocoon formation). There is associated loculated ascites
(star) seen.

24. • Ileocecal TB: MRE T2-weighted images (A and B) showing wall thickening which is
hyperintense involving the ileocecal region (thin arrow) with enlarged regional
lymph nodes (outlined arrow). The wall thickening shows diffusion restriction on
diffusion weighted b-800 image (C) and hyperenhancement on post-gadolinium
image (D) suggestive of active disease.

25. Duodenal Tuberculosis
• It constitutes only about 2% of all GI TB.
• CT may show thickening of the duodenal wall commonly
involving the second and the third part, which may be
associated with stricture and proximal dilatation.
• Duodenal TB can mimic CD, lymphoma and carcinoma
and it is usually difficult to differentiate them. Biopsy is
confirmatory for the diagnosis.

26. • Duodenal TB: Axial CTE image (A) coronal MPR (B) and curved MPR (C) of a patient
who presented with vague abdominal pain and weight loss showing irregular
thickening and narrowing of third part of duodenum (thin arrow). Endoscopic biopsy
revealed caseating granulomas and the patient responded to ATT.

27. Peritoneal Tuberculosis
• Involvement of peritoneum, mesentery and omentum are
grouped under peritoneal TB.
• Spread of infection is either from rupture of involved lymph
nodes or direct extension across the bowel wall.
• Peritoneal involvement manifests as thickening of the
peritoneum (2–6 mm) with or without associated nodules.
• On USG the peritoneal thickening is seen as hypoechoic lesions
and on CECT it is seen as smooth or nodular peritoneal
thickening and enhancement.
• Tuberculous ascites usually shows low serum ascites albumin
gradient (SAAG <1.1 g/dL) and elevated levels of adenosine
deaminase (ADA) and lymphocytes.

28. • There are three types of peritoneal involvement
based on the amount of ascites and associated
features :
• 1. Wet type—most common type, gross free or
loculated ascites.
• 2. Fibrotic-fixed type—less common, with matted
bowel loops, mesenteric masses and loculated
ascites.
• 3. Dry-plastic type—rare, nodular dense fibrotic
reaction of peritoneum

29. • Peritoneal TB: Axial CECT image of abdomen showing loculated ascites
(star) with smoothly thickened enhancing peritoneal lining (thin arrow)
and associated omental thickening (thick arrow). The above features are
suggestive of wet type of peritoneal TB.

30. Lymph Nodal TB
• Mesenteric, omental, peripancreatic, periportal and
upper retroperitoneal lymph nodes are commonly
involved in TB.
• Enlarged lymph node with peripheral enhancement and
central necrosis is the commonest type of appearance
and is relatively specific for TB. However, central
necrosis can be seen in malignancies, aggressive
lymphoma and Whipple's disease.

31. • Liver and lymph nodal TB: Axial CECT images (A and B) showing a
focal hypodense lesion in the liver (thin arrow) and multiple
periportal and peripancreatic necrotic lymphadenopathy (thick
arrow). These findings are consistent with macronodular type of liver
lesions and lymph nodal involvement in TB.

32. INFLAMMATORY BOWEL DISEASE
• Inflammatory bowel disease comprises a group of
bowel disorders characterized by idiopathic chronic
inflammation of bowel.
• It includes mainly Crohn's disease and ulcerative
colitis

33. Crohn's Disease
• Crohn's disease is a transmural granulomatous inflammatory
process of the bowel wall characterized by waxing and waning
course and discontinuous involvement of the bowel, which can
be complicated by fistulae and abscesses.
• Small intestine involvement is seen in 70% of cases, most
commonly at the terminal ileum and colonic involvement can
be seen in up to 50% .
• Patients present with pain abdomen, diarrhea, low grade fever
and easy fatigability
• imaging can differentiate active inflammatory CD from
fibrostenotic CD.
• Active CD is managed by medical treatment whereas
fibrostenotic CD may need surgical management.

35. • Double contrast barium enteroclysis was the
imaging modality of choice before the emergence
of cross sectional modalities like CTE and MRE.
• Bowel wall thickening is the most common finding
in patients with CD. It is usually symmetrical and
circumferential, most commonly involving the
terminal ileum and the ileocecal junction.

36. • aphthous ulcers
seen in the
active phase of
disease as
punctate
collection of
barium with
surrounding
radiolucent halo
due to mucosal
edema

37. • When the disease
progresses, the
ulcers coalesce
and form deep
linear ulceration
separating out
the edematous
mucosa. This is
seen on barium
studies as cobble
stoning.

40. • Stratified wall enhancement in active CD: Coronal CTE images (A
and B) and sagittal MPR (C) showing thickening and stratified
wall enhancement involving the ileal loops (thin arrow) which is
a sign of active inflammatory stage of CD.

41. • Active CD: MRE images showing thickening of ileocecal junction (thin
arrow) which is hyperintense on T2-weighted images (A and B), restricting
diffusion on diffusion weighted image (C) and showing intense
enhancement on postcontrast T1-weighted images (D).

42. • Recognising fibrosis on imaging is crucial for the
management of CD because those patients are
often considered for surgery as they are unlikely to
benefit from medical therapy.
• MRE has an edge over CTE in this regard as fibrosis
manifests as hypointensity on both T1 and T2-
weighted images and shows progressive
homogeneous enhancement in delayed phase

43. • Pseudosacculations in fibrotic CD: Coronal T2-weighted image (A) of MRE study showing
wall thickening and multiple segments of luminal narrowing involving the ileal loops (thin
arrow). There are multiple pseudosacculations seen in the antimesenteric border (outlined
arrow).
• Axial postcontrast T1 weighted image (B)shows homogeneous wall enhancement of the
involved loop. The above imaging features are characteristic o fibrostenotic stage of CD.

44. Skip Lesions
• This is defined as multifocal areas of involvement
with normal healthy bowel in between.
• It is considered as an important sign to differentiate
CD from other infective processes like TB but is not
very specific

45. Comb Sign
• Comb sign is a
manifestation of
prominent vasa
recta due to
increase in
vascularity in the
mesentery. It is
regarded as one
of the specific
signs of active
inflammation
Coronal CTE image showing a segment of dilated ileal loop
with increasedmesenteric vascularity (comb sign) (thin
arrow) in a patient with CD. Presence of comb sign is a
marker of active inflammatory stage of CD.

46. Ulcerations
• It may be seen
as irregularity
of the wall or
thin linear
hyperintensity
extending into
the wall.
T2-weighted coronal image of MRE showing hyperintense
outpouching (thin arrow) in the distal ileal loop suggestive of deep
ulceration in a patient with CD.

48. Ulcerative Colitis
• Ulcerative colitis (UC) is a characterized by
superficial inflammation involving the colon.
• The colonic involvement in UC is symmetric and
contiguous.
• Rectum is involved in almost all cases with varying
length of proximal colonic involvement sometimes
involving the entire colon (pancolitis)
• Occasionally, terminal ileum can be affected and
becomes edematous and dilated when the entire
colon is involved and is called backwash ileitis

52. • Lead pipe sign in chronic UC. Barium study images (A and B) of a patient with
ulcerative colitis showing diffuse luminal narrowing and loss of haustrations
(thin arrow) involving the entire colon without any skip areas. This
featureless appearance of colon in chronic UC is known as lead pipe sign.