Download Gastrointestinal Tract 07

Gastrointestinal Tract
(Effective February 2007)
(1%-5%)
Anatomy of GI Tract
Esophagus
• bulls-eye or “target”
• EG junction seen on
sagittal scan
posterior to left lobe
of liver and anterior
to aorta
Anatomy of GI Tract
Stomach – stores food and aids in digestion
• Fundus
• body or corpus
– lesser curvature
– greater curvature
•
Pylorus
– Antrum
– canal or bulb
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supporting ligaments
greater curvature
• greater omentum
• gastrophrenic
ligament
• gastrosplenic
ligament
• lienorenal ligament.
lesser curvature
• gastrohepatic
ligament
• lesser omentum.
Small intestines
Most of the digestion and absorption of food takes
place (pancreatic enzymes and bile)
• three parts: duodenum, jejunum, and ileum.
–
•
about 23 feet long and 1 inch wide
avalvulae conniventes (valves of Kerckring)
–
linear echoes representing mucosal folds spaced 3
– 5mm apart that slow down the passage of food to
create a greater absorbing area → “Keyboard
sign”
duodenum is divided into four parts
•
#1 pylorus and runs upward and backward on the right
side of the first lumbar vertebra
#2 runs anterior to the right kidney on the right side of
the second and third lumbar vertebrae
•
–
The common bile duct and main pancreatic duct pierce the
duodenal wall midway down its posterior aspect.
2
duodenum is divided into four parts
•
•
#3 horizontally to the left, following the
inferior margin of the pancreatic head
#4 runs upward and to the left, and then
runs forward at the duodenojejunal junction.
–
ligament of Treitz ascends to the right crus and
holds the junction in position
Jejunum and Ileum
• jejunum arises from the duodenum and
extends for 2 m
• inner walls –
– circular folds of the mucous membrane,
– villi; the valvulae conniventes are large folds
of mucous membrane
• ileocecal orifice
– marks the entry into the large intestine and
serves as a landmark to find the appendix.
Large Intestine
• divided into the
–
–
–
–
–
–
–
vermiform appendix
Cecum
ascending (to hepatic flexure)
Transverse
descending (to splenic flexure)
colon,
rectum.
The colon is divided into segments called
haustra.Ψ
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Vascular Supply
Esophagus
• inferior thyroid branch supplies the upper
esophagus.
• The descending thoracic aorta supplies
the midesophagus
• The left inferior phrenic artery supplies the
lower end of the esophagus.
Varices may arise from gastroesophageal
arteries.
Vascular Supply
Stomach
•
branches of the hepatic artery,
–
•
right gastric arterial branch, the pyloric and right
gastroepiploic
left gastric artery.
Gastrointestinal Tract
The five layers of bowel:
• Mucosa: directly contacts intraluminal contents; line
with epithelial folds, echogenic
•
Submucosa: contains blood vessels and lymph
channels
•
Muscularis: contains circular and longitudinal bands
of fiber
•
•
Serosa: thin, loose layer of connective tissue
Mesothelium: covers intraperitoneal bowel loops
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Measurements
• wall of the GI tract should measure <5
mm, or <3 mm when distended
– from the edge of the echogenic core to the
outer border of the anechoic halo
Stomach
• Could look like cystic mass in LUQ
• GE Junction seen to the left of the midline as a
bull’s-eye or target structure
• gastric antrum can be seen as a target in the
midline
Duodenum
• Usually, a gas- or fluid-filled duodenal cap
is seen lateral to the pancreatic head.
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Small Bowel
• fluid or contrast media
filled small bowel can
visualize the valvulae
conniventes
– seen as linear echo
densities spaced 3 to
5 mm apart
– known as a keyboard
sign
– The small bowel wall
is <3 mm thick.
Appendix
• located on the abdominal wall under
McBurney’s point.
– McBurney’s point - drawing a line from the right ASIS
to the umbilicus—at the midpoint of this line lies the
root of the appendix. Ψ
• Fusiform structure <6 mm in caliber, 8 to
10 cm long Ψ
Appendix Technique
• high-resolution linear array transducer
should be used
• Graded compression over the area of
maximum tenderness
• visibility of the retrocecal and paracecal
areas is improved by displacing gas and
other bowel loop contents from the
scanning field
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Abnormalities of the Appendix
• appendicitis
– lesion in the RLQ.
– noncompressible mass
– diameter is >6 mm
– muscular wall thickness is >3 mm.
Abnormalities of the Appendix
• Perforation or Abscess
– loculated pericecal fluid
– prominent pericecal fat
– circumferential loss of the submucosal layer
of the appendix.
• Crohn’s Appendicitis
– With Crohn’s ileocolitis the appendix may be
involved 25% of the time
Abnormalities of the Appendix
Appendiceal Tumors
• Primary adenocarcinomas of the appendix
are rare.
• A primary adenocarcinoma may manifest
as acute appendicitis with perforation.
• Often only seen by pathologist
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Colon
• haustral markings 3 to 5 cm apart in the
ascending and transverse colon When
fluid filled
• descending colon appears as a tubular
structure with an echogenic border.
• Layers of the colon :
– mucosa, submucosa, muscularis propria,
serosa, and subserous fatty tissue.
Benign Tumors
Polyp
• seen with fluid distention of the stomach
– solid masses adherent to the gastric wall
• Leiomyomas
– most common tumor of the stomach
– hypoechoic mass continuous with the
muscular layer of the stomach
Malignant Tumors
Gastric Carcinoma
• 90-95% malignant tumors of the stomach
are carcinomas
• ½ of the tumors occur in the pylorus, and
¼ in the body and fundus.
• ultrasound study will show
– a target or pseudokidney sign Ψ
– possibly gastric wall thickening.
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Malignant Tumors
• Leiomyosarcoma
– second most common gastric sarcoma
– globular or irregular and may become huge
– outstrips blood supply → central necrosis →
cystic degeneration and cavitation.
• Metastatic Disease
– rare - originates as melanoma or lung or
breast cancer.
Crohn’s Disease Ψ
• AKA regional enteritis
– recurrent granulomatous inflammatory
disease that affects the terminal ileum and/or
any level of the colon.
• involves entire thickness of the bowel wall.
• Physical symptoms include diarrhea,
fever, and RLQ pain.Ψ
• There is rigidity to pressure exerted from
the transducer.
• Peristalsis is absent or sluggish.
• There is dilation with hyperperistalsis and
water and air stasis.
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Laboratory values
Gastrin
• blood hormone
– stimulates intestinal movement and secretion of juices
– elevates in acute and chronic peptic ulcer disease
Serum Amylase
• elevates in intestinal obstruction, perforated
ulcers; pancreatitis
Feces
• examined for presence of blood, fat, bile, and
• parasites
Hernia
Peritoneal Fluid
(including Inflammatory Fluid Collections)
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