Review on basic GIT Anatomy & Introduction on Abdominal X-ray

1. GIT Anatomy
Liza de la Cruz, M.D.

2. Embryonic Precursors of the GI Tract
Origin Vascular Supply Derivatives
& Nerve
Innervation
Foregut Celiac Artery, Pharynx, lower respiratory tract,
Vagus Nerve Esophagus, Stomach, Liver,
(T12) pancreas, Biliary Tree, duodenum
Midgut SMA, Vagus Distal duodenum, SB, Ascending
Nerve (L1) colon
Hindgut IMA, Pelvic Transverse colon, Rectum, Bladder,
Nerve (L3) Urethra
•Pouchlike extension of the yolk sac
•6 – 12 wks GA
•270 degrees counterclockwise rotation OMV
•Peritoneal fixation (Trietz → ileocecal valve)

4. Pharynx

5. Esophagus
• Tubular → vestibule
• OLIC
• Devoid of serosal lining
• Striated & Smooth
• A ring, B ring, Z line
• GEJ
• A.L.L

6. Stomach
Stomach – FBA
Fundus – posteriorly
C&P
Body & Antrum – anteriorly
G

7. Small Bowel
• 7m long
• Jejunum 2/5
• Ileum 3/5

9. Large Bowel
• 1.5 m
• Taenia coli & haustra
• Sigmoid colon

12. Peritoneum
1. Ligament – formed by 2 folds of peritoneum
supporting a structure within the peritoneal
cavity
2. Omentum – specialized structure connecting
stomach to an additional structure
3. Mesentery – 2 peritoneal folds connecting a
portion to the retroperitoneum

15. FL
GC
TM PC

16. CL
FL
LO
LO
GO
GO
TM TM

17. Retroperitoneal Space
boundaries:
• Superior – diaphragm
• Anterior - posterior
parietal peritoneum
• Posterior - transversalis
fascia
• Inferior - pelvic brim

18. Intraperitoneal Retroperitoneal
Pancreatic tail Pancreas (head, neck, body)
Stomach
1st part of the duodenum (duodenal 2nd, 3rd, 4th part of duodenum
cap)
Jejunum, Ileum, Cecum
Transverse Colon Ascending & Descending Colon
Sigmoid Colon Rectum
Liver, GB and Spleen Kidney, Ureters, Suprarenal Gland
Abdominal Aorta
IVC

19. Retroperitoneal Space

20. Retroperitoneal space
1. Anterior pararenal
2. Perirenal
3. Posterior pararenal

21. Compartmental Anatomy of the Pelvis
1. Cul-de Sac (Pouch of Douglas/Retrovesical Pouch)
2. Extraperitoneal Space – pelvic diaphragm →
retropubic space of Retzius
3. Perineum

22. Liver

23. Couinaud Liver Segments
• I – caudate
LEFT
• II – superior lateral
• III – inferior lateral
• IVa – superior medial
• IVb – inferior medial
RIGHT
• V – inferior anterior
• VI – inferior posterior
• VII – superior posterior
• VIII– superior anterior

24. Fissures

25. Biliary Tree

26. Pancreatic Anatomy

27. Spleen
• Largest lymphoid organ
• No hematopoietic activity in adults
• Sequesters dead RBCs, WBCs & plt
• Reservoir for RBC
• Variations
Lobulations & Clefts
Accesory spleen – @ hilum
Wandering spleen – d/t lax splenic ligaments

28. Still hungry for more…

29. Approach to Abdominal X-ray

30. Most Common Views:
1. Supine
2. Erect
3. Left lateral decubitus
4. Cross Table Lateral

31. Contrast studies
1. Barium swallow – cervical & thoracic
esophagus
2. UGIS – esophagus → duodenal bulb
3. SBFT – UGIS with sequential study q 15-30
min until barium reaches the cecum
4. Enteroclysis – jejunum
5. Double contrast – barium coats, air distends
(mucosal detail)

32. Radiologic Anatomy of the Abdomen
• Gas pattern
• Liver shadow
• Splenic shadow
• Renal shadows
• Psoas shadows
• Flank stripes
• Bones
• Note for any abnormal calcifications

33. Normal Abdominal Gas
• Normal gas seen only in (1) Stomach-
“magenblasse” and (2) Colon.
• In Infants – normally present throughout the
small bowel
• After birth – seen throughout the intestinal
tract

34. Liver & Splenic Shadow
Liver: Anterior RUQ of the abdomen
Spleen: Posterior LUQ of the abdomen

35. Renal Shadow
• Lie on either side of the lumbar spine
• Located in the retroperitoneal space, usually from
T11 – L3 .
• L kidney is about 2 cm higher than right kidney.
• Renal length: adult: 11 – 15 cm, children: 6-12 cm.
• Kidneys may move up to 10 cm on deep inspiration

36. • Pro-peritoneal fat layer (flank stripes)
– Lateral margin of the anterior parietal peritoneum are
bounded externally by a thin layer of fat which is sufficient
to cause a radiolucent stripe.
– obscured with abnormalities in the intra-peritoneal space
affecting the peritoneum such as peritonitis or ascites.
•Psoas Line
-Entirely located in the retroperitoneal space
-Could be seen because of the fat surrounding it gives
contrast to the water density muscle

37. Abnormal Gas Pattern
Too Much Too Little Wrong place
Ileus (+) Large Mass Pneumatosis intestinalis
Bowel Obstruction Ascites Pneumoperitoneum

38. Intestinal Obstruction Ileus
•Air filled, dilated intestine • entire bowel is uniformly
proximal to the point of dilated
obstruction
•Little or no air distal to the
obstruction
•No Pre-sacral gas
•Air fluid levels

39. Pnemoperitoneum

43. Central displacement of
the loops of bowel,
a uniform grayness to
the abdomen, loss of
any definition of the
edge of the spleen or
liver and displacement
of the bowel loops out
of the pelvis

44. Dog Ear Sign

45. Falciform Ligament Sign

46. Mercedes Benz Sign

47. References
Brant, William E., Helms, Clyde A. Fundamentals of Diagnostic
Radiology. 3rd ed. Philadelphia: Lippincott Williams &
Wilkins, 2007.
Dahnert, Wolfgang. Radiology Review Manual. 6th ed.
Philadelphia: Lippincott Williams & Wilkins, 2007.
Dudek, Ronald W. High-Yield Gross Anatomy. 2nd edition.
Philadelphia: Lippincott Williams & Wilkins, 2002.
Le, Tao, Bhushan, Vikas, Vasan, Neil, et al. 20th ed. McGraw-
Hill Companies, 2010.

48. Thank you for your kind attention.