This document summarizes the anatomy and ultrasound appearance of the small intestine and large intestine. It describes the layers of the intestinal wall and provides details on the divisions and sections of the small intestine including the duodenum, jejunum and ileum. It also describes the parts of the large intestine including the cecum, colon, rectum and anal canal. Common intestinal pathologies like appendicitis, diverticulitis, Crohn's disease and ulcerative colitis are discussed along with their typical ultrasound findings.

3.  also called the small bowel.
 is the part of the
gastrointestinal tract
following the stomach and
followed by the large
intestine.
 extends from the pyloric
sphincter of the stomach to
the ileocecal valve, where it
joins the large intestine at a
right angle.
 Digestion and absorption of
food occur in this portion of
the alimentary canal .

4. Size
 Adult human male
> average length 6.9 m (22 feet 6 inches)
 Adult human female
> 7.1 m (23 feet 4 inches)
 Its diameter gradually diminishes from approximately
1 ½ inches (3.8cm) in the proximal part to
approximately 1 inch (2.5 cm) in the distal part.

5. Intestinal wall
 The normal intestinal wall is seen as a multilayered area with
hyperechoic bowel content at the center.
 Five distinct layers can be depicted on sonography:
1. inner hyperechoic layer - which is the interface
between the mucosa and the bowel contents.
2. second hypoechoic layer- which is the deep mucosa.
3. third hyperechoic layer - which is the submucosa
4. fourth hypoechoic layer - which is the muscle proper
5. last outer hyperechoic layer - which is the serosa
and the serosal fat

8. Division
 The small
intestine is
divided into
three portions:
> Duodenum
> Jejunum
> Ileum

9. Duodenum
 The name duodenum is from the
Latin duodenum digitorum, or
"twelve fingers' breadth".
 is 8 to 10 inches (20 to 24 cm) in
length.
 It is retroperitoneal and relatively
fixed in position.
 The duodenum is divided into four
sections: first (superior), second
(descending), third (horizontal
or inferior), and fourth
(ascending) portions.

10.  The segment of the first portion is called the duodenal
bulb because of its radiographic appearance when it is
filled with an opaque contrast medium.
 The second portion is about 3 or 4 inches (7.6 to 10cm)
long. This segment passes inferiorly along the head of the
pancreas and in close relation to the undersurface of the
liver.
 The third portion passes toward the left at a slight superior
inclination for a distance of about 2 1/2 inches (6 cm) and
continues as the fourth portion on the left side of the
vertebrae.
 The duodenal loop, which lies in the second portion, is
the most fixed part of the small intestine and normally
lies in the upper part of the umbilical region of the
abdomen; however, its position varies with body habitus
and with the amount of gastric and intestinal contents.

11.  The duodenum is largely responsible for the
breakdown of food in the small intestine, using
enzymes.
 The duodenum also regulates the rate of emptying of
the stomach via hormonal pathways. Secretin and
cholecystokinin are released from cells in the
duodenal epithelium in response to acidic and fatty
stimuli present there when the pylorus opens and
releases gastric chyme into the duodenum for further
digestion.

12. Jejunum
 is the middle section of the small intestine.
 is wider, its diameter being about 4 cm., and is thicker
and more vascular.
Ileum
 is the final section of the small intestine
 is narrow, its diameter being 3.75 cm. and its coats
thinner and less vascular than those of the jejunum.
 The jejunum and ileum are attached to the posterior
abdominal wall by an extensive fold of
peritoneum, the mesentery, which allows the freest
motion, so that each coil can accommodate itself to
changes in form and position.

13.  The large intestine is about 5 feet ( 1 .5 m) long and is
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greater in diameter than the small intestine.
It begins in the right iliac region, where it joins the ileum of
the small intestine, forms an arch surrounding the loops of
the small intestine, and ends at the anus.
The wall of the large intestine contains the same four layers
as the walls of the esophagus, stomach, and small intestine.
The main functions of the large intestine are reabsorption
of fluids and elimination of waste products.
The large intestine takes about 16 hours to finish the
digestion of the food. It removes water and any remaining
absorbable nutrients from the food before sending the
indigestible matter to the rectum.

15. The large intestine has four main parts:
Cecum
Colon
Rectum
Anal canal

16. Cecum - is the pouchlike portion of the large intestine
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and is below the junction of the ileum and the colon .
- is approximately 2 1/2 inches (6 cm) in length and 3
inches (7.6 cm) in diameter.
The vermiform appendix is attached to the posteromedial
side of the cecum.
The appendix is a narrow, wormlike tube that is about 3
inches (7.6 cm) long.
The ileocecal valve is just below the junction of the ascending
colon and the cecum. The valve projects into the lumen of
the cecum and guards the opening between the ileum and
the cecum.

17. Left colic flexure
right
flexure
Descending colon
Ascending colon
Taenia coli
Haustra
Ileocecal valve
Cecum
Sigmoid colon
Anus

18. Colon- is subdivided into
ascending, transverse, descending, and sigmoid
portions.
Transverse colon
Sigmoid colon
rectum

19.  The ascending colon passes superiorly from its junction
with the cecum to the undersurface of the liver, where it joins
the transverse portion at an angle called the right colic
flexure (formerly hepatic flexure).
 The transverse colon, which is the longest and most
movable part of the colon, crosses the abdomen to the
undersurface of the spleen. The transverse portion then
makes a sharp curve, called the left colic flexure (formerly
splenic flexure), and ends in the descending portion.
 The descending colon passes inferiorly and medially to its
junction with the sigmoid portion at the superior aperture of
the lesser pelvis.
 The sigmoid colon curves to form an S-shaped loop and
ends in the rectum at the level of the third sacral segment.

20. Rectum
 extends from the sigmoid colon to the anal canal.
 is approximately 6 inches (15 cm) long. The distal
portion, about 1 inch (2.5 cm) in length, is constricted
to form the anal canal .
 Following the sacrococcygeal curve, the rectum passes
inferiorly and posteriorly to the level of the pelvic floor
and then bends sharply anteriorly and inferiorly into the
anal canal, which extends to the anus.

21. Anal Canal
 The anal canal terminates at
the anus, which is the
external aperture of the large
intestine
 It forms an angle with the
lower part of the rectum, and
measures from 2.5 to 4 cm. in
length.
 Just above the anal canal is a
dilation called the rectal
ampulla.
 The rectum and anal canal
thus have two
anteroposterior curves, a fact
that must be remembered
when an enema tube is
inserted.
Rectal
ampulla
canal
Anus

22.  Adults: Do not eat or drink 8 hours before exam.
 Children: Do not eat or drink 4 hours before study
or skip 1 meal.
 Necessary medications may be taken with a small
amount of water only.
 No chewing gum.

23.  Severe abdominal pain
 Inflammatory Bowel Diseases
 Neoplastic Bowel Diseases
 Management of intestinal obstruction

24.  The choice of transducer for bowel assessment largely depends on the patient's body
habitus and the distance between the probe and the object of study.
For a regular scan of the abdomen:
> abdominal transducer (2-5 MHz)
For a detailed examination of the intestine:
> A 2.5- to 5.0-MHz curvilinear probe is used for a heavy
patient.
> A 7.0- to 12.0-MHz linear transducer, which facilitates
high-resolution sonography, is used for an average-size or
thin patient and generally for assessment of superficial
abnormalities.

25.  In patients with localized abdominal pain, the sonographic examination
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can be started at the point of maximum tenderness.
An area of interest is carefully analyzed with a high-resolution linear probe
and graded compression sonography if possible.
The compression resembles palpation of the abdomen. Gentle but adequate
graded compression is applied to decrease the distance between the probe
and the area of interest and to displace gas and fecal material.
For average-size and thin patients, a 7.0- to 12.0-MHz linear probe
normally is sufficient for detailed evaluation of the area of interest and
assessment of the peristalsis, compressibility, and rigidity of the segment in
question.
For obese patients and patients in whom the affected bowel segment is
distant from the abdominal surface, a lower-frequency curvilinear probe
should be used, and a fair amount of pressure must be applied to obtain
images of diagnostic quality.

29. Appendicitis
> is an inflammation of the
appendix. It occurs when
the appendix becomes
blocked, often by stool, a
foreign body, or cancer.
Blockage may also occur
from infection, since the
appendix swells in response
to any infection in the body.

30. Ultrasound of appendicitis:
 The normal appendix presents as a small, easily
compressible, concentrically layered, mobile, blindending, sausage-like structure. The diameter is usually less than 7
mm, but is incidentally large. The normal appendix is mobile, may
have a collapsed lumen, but also may contain air or some fecal
material, and rarely a little fluid. Power Doppler reveals scarce or
no vascular signal and there is no hyperechoic, non-compressible
inflamed fat around the appendix.
 The typical appearance of an inflamed appendix is that of a
concentrically layered, non-compressible sausage-like structure
demonstrated in a fixed posi-tion at the site of maximum
tenderness. The average maximum diameter is 9 mm with a
variation from 7 to 17 mm.

32. A
B
—20-year-old man with acute nonperforating appendicitis. Long-axis (A) and
transverse (B) sonograms of appendix typically situated in right iliac fossa show
enlarged (9.6 mm) appendix (long arrows) and prominent hyperechoic inflamed
periappendiceal fat (short arrows).

33. Diverticulitis
 Is a common digestive disease which
involves the formation of pouches
(diverticula) within the bowel wall.
Diverticulitis results when one of these
diverticula becomes inflamed.
 Doctors aren't sure what causes
diverticula in the colon
(diverticulosis). But they think that a
low-fiber diet may play a role. Without
fiber to add bulk to the stool, the colon
has to work harder than normal to
push the stool forward. The pressure
from this may cause pouches to form
in weak spots along the colon.
 Diverticulitis happens when feces get
trapped in the pouches (diverticula).
This allows bacteria to grow in the
pouches. This can lead to
inflammation or infection.

34.  On sonography, inflamed diverticula appear as bright echogenic foci
with acoustic shadowing or a ring-down artifact within or beyond the
thickened gut wall.
56-year-old man with acute
sigmoid diverticulitis.
Transverse gray-scale image
through left lower quadrant
shows wall thickening of
sigmoid colon (arrowheads)
with associated diverticulum
(calipers). Adjacent
mesenteric and omental fat
(F) is abnormally echogenic
and attenuating, obscuring
deeper structures.

35. Crohn’s Disease
 Crohn's disease is an inflammatory bowel disease (IBD). It
causes inflammation of the lining of your digestive
tract, which can lead to abdominal pain, severe diarrhea
and even malnutrition. Inflammation caused by Crohn's
disease can involve different areas of the digestive tract in
different people.
 Sonographically, there is marked mural thickening of the
ileum, which shows decreased or no peristalsis and is not
compressible. Classically, all layers are involved and layer
structure is often locally disturbed, the earliest sign being
echolucent changes in the submucosa. There is
inflammation of the fatty mesentery and
omentum, recognizable as hyperechoic, noncompressible
tissue adjacent to the ileum.

36. Fig. 4 —6-year-old
boy with Crohn
disease. Gray-scale
ultrasound image
shows dramatic
circumferential wall
thickening of two
adjacent small-bowel
loops (arrowheads).
Note also increased
echogenicity of
adjacent mesenteric
fat (F), indicating
inflammation.

37.  Fig. 8 —17-year-old girl
with Crohn disease.
Power Doppler image of
terminal ileum
(arrowheads) shows wall
thickening and mural
hyperemia, indicating
active inflammation.
Note also enlarged
adjacent mesenteric
lymph node (arrow)
surrounded by echogenic
fat.

38. Ulcerative colitis
 is a disease that causes inflammation and sores
(ulcers) in the lining of the large intestine (colon ). It
usually affects the lower section (sigmoid colon) and
the rectum.
 Cytomegalovirus is the most commonly associated
pathogen in colitis in post-transplant patients. Other
causes for colitis include ischemic
factors, parasites, and radiation.
 Sonographic findings include long
segment, concentric, regular thickening of the colonic
wall.

39.  45-year-old woman
with ulcerative colitis.
Long-axis sonogram of
sigmoid colon
(arrows) in left lower
quadrant shows
concentric diffuse wall
thickening (12
mm, calipers) of entire
sigmoid colon, mainly
due to thickening of
mucosa.

40.  52-year-old woman with
infectious colitis. Grayscale ultrasound image
shows concentric wall
thickening and blurring
of normal mural
stratification
(arrowheads) in colon.
Power Doppler image
(inset) reveals marked
hyperemia (arrow) in
affected segment.

41. THE END.
Reported by: JOAN C. VARGAS
JONATHAN MANAOIS