Medical application of transabdominal ultrasound
in gastrointestinal diseases
Department of Emergency Medicine
National Taiwan University Hospital
Real-time ultrasound has become a standard technique in evaluation of
intraabdominal disorders. It is a good tool easily available and without radiation. For
the first-line physicians, only anatomic explanation by ultrasound is not enough.
Combining ultrasound findings with history taking and physical examination is very
important, and may lead to more rapid and appropriate management of patients. That
means taking ultrasound not only as an image tool but also physicians’ “secondary
Besides intraabdominal solid organs, ultrasound has also been applied on
hollow organs, that is the gastrointestinal tract. For the solid organs, including liver,
gallbladder, pancreas, kidneys, spleen etc, ultrasound has been applied widely and
every field has set up its standard diagnostic picture. Its application is considered
easier than the gastrointestinal tract. For survey of the gastrointestinal tract, from
esophagogastric junction to rectum, ultrasound can also play its important diagnostic
role. Maybe bowel gas is a main problem for ultrasound imaging, but most causes can
get some clinical implication form the study. Gas is may be a friend for sonographer
in evaluation of GI tract. For example, free air means hollow organ perforation; air in
close space usually means abscess; air in a tract means a fistula or perforation hole.
Role of ultrasound in gastrointestinal diseases
The application of ultrasound in the gastrointestinal tract is as followings: 1.
For screening of GI symptoms. 2. Localize and define the nature of GI lesions. 3.
Evaluation of severity of GI lesions. 4. Follow-up of GI lesions after treatment. 5. As
a assistant tool added to other image modalities. 6. Preventing hazardous and
unnecessary procedures. 7. Promoting efficient works in ER. For screening of GI
symptoms, it may be not as efficient as when applied to solid organs, especially early
GI tract cancer. But for acute lesions or conditions such colitis, ileus or perforation,
etc, sometimes it works. Evaluation of severity of GI lesions gives much clinical
implication to physicians, because the treatments depend on the severity of GI lesions.
Preventing hazardous and unnecessary procedures by ultrasound is an important issue,
especially in emergency service. It includes 1. to prevent hazardous endoscopic
procedures in PPU, colon perforation and diverticulitis. 2. to prevent hazardous enema
for colon perforation & diverticulitis. 3. to prevent unnecessary enema for upper GI
obstruction. About the promoting efficient works in ER, it is time and money-saving
and makes quick diagnosis. For example, if we detect fluid-filled stomach, NG tube
will be inserted for drainage to prevent aspiration & to facilitate efficient endoscopic
How to apply GI ultrasound
First, to familiar with ultrasound anatomy of GI tract is very important. For
gross anatomy, we should realize the fixed portion and unfixed portion of GI tract.
Fixed portion of GI tract includes EG junction, duodenum, ascending colon,
descending colon & rectum. Unfixed portion of GI tract includes small bowels,
transverse colon and sigmoid colon. Terminal ileum and appendix, which connect the
fixed cecum, are considered partially fixed and not difficult to scanning by ultrasound.
For the macroscopic anatomy, we should realize the layering of walls of GI tract and
also the characteristic ultrasound pictures of different segments of GI tract.
Five-layered structure of GI tract wall is the basic concept (fig. 1) . Loss of the
stratifications always means abnormal events. Characteristic ultrasound pictures of
small bowels and colon is different. Small bowels reveals with folds of Kerckring
(valvulae conniventes) which present on ultrasound as small “spikes” with short
distance from each other on small bowel wall. On the other side, colon shows
haustration which looks like “bamboo” on ultrasound.
Second, selection of proper MHz of ultrasound probes is essential. Usually, 5 or
7 MHz for average or thin patients is recommended. For heavy patients, 3 MHz is
considered. Of course, it depends on the operators.
Third is ultrasound scanning method. Scanning may be generalized but more
focused over target area with symptom/sign. It may be started from fixed portions to
mobile portions, A/D/R colon to T/S colon and colon to small bowel. Longitudinal
and transverse scanning should be used alternatively.
Recognize the abnormal GI tract lesions
When scanning the GI tract, what to check is:
Wall thickening Location of lesions Perienteric change
degree intraluminal fat tissue
distribution mural lymph node
Intraluminal lesion usually indicates foreign bodies such as bezoars. GIST sometimes
presents with exophytic growing.
Characters of abnormal GI tract lesions were as follow:
Layered appearance Loss of layered appearance
Compressible Lack of compressibility
Intermittent peristalsis Increased thickness ( > 4 mm )
Decrease in intraluminal gas or fluid
Using compression method, the diseased bowel usually does not change its
Sometimes, indirect signs on echogram for diseases of GI tract are helpful. It
includes free air, creeping fat, air in portal vein, whirlpool sign, etc.
Application of ultrasound in GI diseases
EG junction Hiatal nernia
Stomach Gastric ulcer
Duodenum Duodenal ulcer
Small bowel Perforation
Bezoar, fish bone, chicken bone
Echo signs which may help diagnosis of GI tract diseases
Echo sign Diseases
Aurora sign Pneumatosis intestinalis
Circle sign Pneumatosis intestinalis
Dome sign Diverticulitis
Hay-fork sign Intussusception
Multi-centric sign Intussusception
Key-Board sign Intestinal obstruction
Peudokidney sign Bowel tumor
Target sign Intussusception
US characters for individual GI diseases
Appendicitis Distended & fixed ( without peristalsis )
( diameter > 6 mm )
Echogenic appendiceal fat
For equivocal case – US doppler may be helpful
Diverticulitis Hypoechoic outpouchings from GI wall
Containing echogenic materials
- air, fecal material, enteroliths
neighboring bowel wall thickening
perienteric echogenic fat change
local anechoic abscess with echogenic foci
( “dirty shadow” from air )
Right sided diverticulitis More common in the Asian population
Must be D/D with appendicitis
Consevative treatment is the first choice
Epiploic appendagitis Echogenic fingerlike projection arising from colon
Echogenic & mass-like pericolonic fat
Torsion or venous thrombosis of epiploic
Pseudomenbranous colitis prominent gyral pattern of submucosa
Ischemic colitis segmental wall thickening, most R-S-D colon
Crohn disease Transmural involvement
Acute phase – echogenic band of SM layer
Chronic phase – hypoechoic thickening
Fistula :hypoechoic tract with echogenic air bubble
Perienteric fat – creeping fat
Adenopathy – 20 %
Small bowel obstrcuction Dilated, fluid-filled bowel loops
Edematous wall due to vascular or lymphatic
To-and fro motion of bowel content
Whirlpool sign for volvulus
In conclusion, It is possible to figure out lesions of GI tract by ultrasound.
Through the daily practice, although operator-dependent, there may be “ general rules
“ in proceeding ultrasound on diseases of GI tract.