abdomen anatomy

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CVM 6101Radiographic Anatomy of the

AbdomenTravis C. Saveraid, DVM, DACVR

Medical Imaging Department

College of Veterinary Medicine

University of Minnesota

Veterinary Medical CenterUNIVERSITY OF MINNESOTA

CVM 6101 [Imaging Anatomy]

• Goals & Expectations:– Identify specific structures or parts thereof– Understand why the views (projections) look as they

do– Keep in mind that the items listed in the “to know” lists

are from the perspective of practicing radiologists– If asked, be able to describe what soft-tissue (muscle,

tendon, ligament, vessel, or alimentary/parenchymal) structure(s) attach to, pass through, or lie in contact with a given anatomic landmark or region



• Approach:– Introductory lectures defining the important structures

and how they are viewed radiographically– Open session, instructor proctored group laboratory

exercises wherein actual radiographs of the anatomic structures are viewed and understood

– Web-based self-study sets both available on CD and from the web site http://www.academic-server.cvm.umn.edu/radiology//


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• Sources of Information:– Anatomy Textbooks– Radiographic Anatomy Textbooks– General Veterinary Imaging Textbooks– U-MN Medical Imaging web site

http://www.academic-server.cvm.umn.edu/radiology/


To Know List1) liver• 2) spleen• 3) left and right kidneys• 4) urinary bladder• 5) small intestine• 6) colon• 7) rectum• 8) prostate gland• 9) left and right diaphragmatic crura• 10) diaphragmatic cupola• 11) approximate area of the adrenal glands• 12) approximate area of the pancreas• 13) xiphoid of the sternum• 14) approximate area of the uterus• 15) approximate area of the left and right ovaries• 16) stomach: cardiofundic, body, and pylorus/pyloric antrum regions• 17) cecum

18) approximate area of the caudal vena cava, aorta, and iliac (sublumbar) lymph nodes

• 19) region of the falciform fat

Abdominal CT images(single slice)

DorsalSagittal

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(*3 different dogs)

• Left parasagittal

• Midline sagittal

• Right parasagittal

Normal Lateral Views


Normal VD Views


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Normal Canine Abdomen

Normal (Fat) Feline

Normal (Fat) Feline

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Interpretive Background: Abdomen

• Peritoneal organs (surrounded by peritoneum and obscured by peritoneal fluid) include liver, spleen, pancreas, alimentary organs, urinary bladder, uterus, ovary, prostate (depending on location) and mesenteric lymph nodes

• Retroperitoneal organs (only partially surrounded by peritoneum and NOT obscured by peritoneal fluid) include great vessels, kidneys, adrenal glands, ureters (except very distal), urethra and retroperitoneal lymph nodes



• Diaphragm:– V D/D V and R L/L R views– Beware of superimposed structures including

vertebrae, ribs, sternebrae, lungs, stomach, nipples, fascial planes, trachea, etc.

– Remember, the diaphragm is a sling-like muscle that “actively” contracts (caudally) and “passively” relaxes (cranially) [numerous influences such as lungs, abdominal fat, etc.]



• Diaphragm: Specific Morphology– Hiatus for caudal vena cava– Hiatus for aorta– Hiatus for esophagus (esophagus, vagal n)

• For more review, see normal thoracic lecture


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Diaphragm– Aortic hiatus


CVM 6101 [Imaging Anatomy]Diaphragm

– CVC hiatus


CVM 6101 [Imaging Anatomy]Diaphragm

– Esophageal hiatus


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• Stomach:– V D/D V and R L/L R as well as horizontal-

beam views– Beware of superimposed structures including vertebrae,

ribs, sternebrae, lungs, stomach, nipples, fascial planes, liver, etc.

– Remember, the stomach is like a wine skin with an outlet on both ends (distension changes its shape)

– The stomach responds to forces from regional organs and masses by changing shape



• Stomach: Broad Anatomic Regions– Cardia– Fundus– Body– Pylorus



Normal Abdominal Architecture

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• Useful interpretive criteria:– Liver size influences the “fundic-pyloric” axis

• Normally parallel to last 2-3 ribs on lateral view• Normally perpendicular to spine on VD/DV views

– Large liver or right-sided liver mass displaces pylorus caudally and to the left • remember F-P axis effect

– Small liver allows pylorus to drift cranially• remember F-P axis effect


Fundic-pyloric axis

• Normal axis between perpendicular to spine and parallel to caudal ribs


• Stomach:– Appearance changes depending on DV (sternal

recumbency) vs. VD (spinal recumbency) views (with the X-ray beam is centered on the last rib):

• On DV views, the gas is primarily in the cardiac region with less in the pyloric region; fluid is in the body region

• On VD views, the fluid is primarily in the cardiac region with less in the pyloric region; air is in the body region

• Appearance may vary depending on the relative amounts of fluid and gas


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CVM 6101 [Imaging Anatomy]Stomach

– DV– Gas in cardia and

pyloric antrum



Stomach– VD– Gas in body/fundus



• Stomach:– Appearance changes depending on R vs. L recumbent

lateral views (with the X-ray beam is centered on the last rib):

• On R lateral views, the gas is primarily in the cardiac region with fluid in the pyloric region (may look like ball)

• On L lateral views, the gas is primarily in the pyloric region with fluid in the cardiac region

• Appearance may vary depending on the relative amounts of fluid and gas


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Stomach– R lateral

recumbency– Gas in cardia– Fluid in pylorus



– L lateral recumbency

– Gas in pylorus– Fluid in cardia



• Stomach: Specific Morphology– Gastroesophageal Junction– Rugae– Pyloric Antrum/pylorus


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– GastroesophagealJunction



Stomach– Rugae



Stomach– Pyloric Antrum


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• Small Intestine:– V D/D V and R L/L R and horizontal-

beam views– Beware of superimposed structures including

vertebrae, ribs, stomach, nipples, kidneys, spleen, fascial planes, urinary bladder, etc.

– Remember, relative amounts of small bowel gas varies by species (dogs, 30 – 60 %; cats, nearly gasless)


Interpretive Background: Abdomen• Useful interpretive criteria:

– Small bowel can be compared to the width and length of the lumbar vertebral bodies:

• Normal canine or feline small bowel are less than 3 rib widths or less than the height of a lumber vertebral body in diameter

• Concern should arise if the diameter approaches the width of a lumber vertebral body

• Surgical intervention is often indicated if the diameter equals or exceeds the length of a lumber vertebral body



• Small Intestine : Broad Anatomic Regions– Duodenum

• Descending• Ascending

– Jejunum– Ileum


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CVM 6101 [Imaging Anatomy]Small Intestine

– Note gas-fluid “relationship”

– Note gas-fluid “distribution”

– Beware of influences by other regional organs including retroperitoneal fat





• Small Intestine :– Appearance changes depending on DV vs. VD

and R vs. L lateral recumbency views (with the X-ray beam is centered on the last rib):

• Gas and fluid distribution should be even• Gut diameter should be randomly varied, but some

degree of uniformity• Beware of measuring gut wall on recumbent views


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Intestinal wall thickness?

Cross-section axial Cross-section sagittal

WallGas

Wall +Fluid

Gas

Gravity

CVM 6101 [Imaging Anatomy]Small Intestine

– Lateral recumbency



Small Intestine– Dorsal recumbency

(VD)


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• Large Intestine:– V D/D V and R L/L R with occasional

horizontal-beam views– Beware of superimposed structures including

vertebrae, ribs, pelvis, lidneys, stomach, nipples, fascial planes, urinary bladder, prostate gland, small intestine, etc.

– Remember, colonic and cecal gas as well as stool diameter are highly variable



• Large Intestine : Broad Anatomic Regions– Ascending colon– Cecum (big difference between dog and cat)– Transverse colon– Descending colon




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Large Intestine– Lateral view– Post-barium

enema



Large Intestine– Ventrodorsal view



• Large Intestine :– Appearance (basically gas and fluid shifts, not

stool movement) changes depending on R vs. L or dorsal vs. ventral recumbent views (with the X-ray beam is centered on the last rib):

– Varied recumbency can foster differentiating normal variation from abnormal


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• Liver:– V D/D V and R L/L R and, when

indicated, horizontal-beam views– Beware of superimposed structures including

vertebrae, ribs, sternebrae, lungs, stomach, nipples, fascial planes, small intestine, and (occasionally) colon, etc.


CVM 6101 [Imaging Anatomy]• Liver: Broad Anatomic Regions

– Left lateral lobe– Left medial lobe– Quadrate lobe– Porta hepatis (hilus)– Right medial lobe– Right lateral lobe– Caudate lobe:

• Caudate process (R kidney)• Papillary process




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Liver Sagittal


Liver– L lateral

recumbency– R lateral

recumbency


CVM 6101 [Imaging Anatomy]Liver

– Dorsal recumbency


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Liver Mass



Gall Bladder– Normally not seen on

survey radiographs– Opacified with iodinated

contrast medium ingested or injected parenterally

– Opacified with iodinated contrast medium via direct injection

– Contained (roughly) between the R medial and quadrate liver lobes



• Spleen:– V D/D V and R L/L R views– Beware of superimposed structures including vertebrae,

ribs, sternebrae, lungs, stomach, small bowel, large bowel, kidneys, pancreas, occasionally urinary bladder, nipples, fascial planes, etc.

– Remember, the spleen is attached to the stomach by the gastrosplenic ligament, but the spleen can move around freely within limits (beyond which it becomes a splenic torsion)


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• Spleen: Broad Anatomic Regions– Head– Body– Tail





Spleen– Lateral view

(1o tail)


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Spleen– VD View (1o body)


Splenic Mass



• Pancreas:– V D/D V and R L/L R views– Typically pancreas is NOT visible (exception

fat cats)– Remember, pancreas has a close relationship to

the greater omentum, the descending duodenum and the transverse colon/stomach interface


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• Pancreas: Broad Anatomic Regions– Head (bile ducts)– Right limb– Left limb




CVM 6101 [Imaging Anatomy]Pancreas “regions”

– R lateral view– Pancreatitis (haze

caudal to stomach)


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Pancreas “regions”– VD view– Pancreatitis (haze in

RUQ)


Pancreatic Mass



• Kidneys & Ureters:– V D/D V and R L/L R views– Beware of superimposed structures including

vertebrae, ribs, stomach, nipples, spleen, pancreas, small bowel, large bowel, occasionally urinary bladder, fascial planes, etc.

– Remember, kidneys and the proximal +/- 80% of the ureters are functionally retroperitoneal


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Interpretive Background: Abdomen• Kidneys & Ureters

– Kidney size (on VD view) is compared to the length of the 2nd lumbar vertebral body• Normally dog kidneys between 2.5 and 3.5 L-2

lengths• Renal pelvic width (seen only with intravenous

contrast medium) is no more than 2 – 3 mm• Normally cat kidneys between 2.4 and 3.0 L-2

length– Note with advancing age, old cat kidneys

(particularly when neutered) approach 2.0 L-2 lengths



• Kidneys & Ureters: Broad Anatomic Regions– Parenchyma:

• Cortex• Medulla

– Hilus (sinus)– Pelvis– Pelvic recesses


Dorsal Plane CT and MR images

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Cranial margin of right kidney

• Not usually visible (dogs) because of close relationship with the liver in the renal fossa of the caudate process of the caudate liver lobe


Kidneys & Ureters– R lateral view– Preferred because

R recumbency fosters kidney cranial-caudal separation



Kidneys & Ureters– VD view– Preferred because

available measurements are standardized from the VD view against the length of L2 vertebral body


R

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CVM 6101 [Imaging Anatomy]Kidneys &

Ureters– R lateral

view– Intravenous

urogram(iodine) [L stricture]



Kidneys & Ureters– VD view– Intravenous urogram

(iodine) [L stricture]


Kidney Mass


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Adrenal Glands– Normally not seen on

survey radiographs– Very close to aorta and

caudal vena cava (e.g. tumor invasion problem)

– Masses displace ipsilateral kidney

– L adrenal mass


Left Adrenal Mass


• Urinary Bladder and Urethra:– V D/D V and R L/L R views– Beware of superimposed structures including

vertebrae, pelvis, small bowel, large bowel nipples, fascial planes, etc.

– Remember, bladder is a “holding tank” for urine delivered from the kidneys via the ureters; size and shape are, therefore, variable


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• Urinary Bladder: Broad Anatomic Regions– Trigone:

• 2 ureters• 1 urethra

– Apex



• Urethra: Broad Anatomic Regions– Male:

• Prostatic portion (within prostate gland)• Membranous portion (from prostate gland to the

tuber ischii)• Penile portion (from the tuber ischii to the external

urethral orifice)



Urinary Bladder– R lateral view


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Urinary Bladder– VD view


CVM 6101 [Imaging Anatomy]Urinary Bladder and

Urethra in a male dog– Positive contrast

(iodine), distension urethrocystogram

– Lateral view– URETHRAL NOTE:

prostatic portion larger than either membranous or penile portions



Urinary Bladder and Urethral in a male dog– Positive contrast

(iodine) urethrocystogram

– VD view– URETHRAL NOTE:

prostatic portion larger than either membranous or penile portions


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• Uterus & Ovaries:– V D/D V and R L/L R views– Beware of superimposed structures including vertebrae,

urinary bladder, bony pelvis, colon and small bowel, stomach, nipples, fascial planes, prepuce/penis, etc.

– Remember, the ovaries and uterus are both intraperitoneal (mix with bowel, hard to find)

– Normal ovaries and uterus on rarely seen on survey films



Uterus & Ovaries: Broad Anatomic Regions– Uterus:

• Horns• Body• Cervix

– Ovaries


Ovarian Mass


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Uterus & Ovaries– Enlarged L ovary– VD view


CVM 6101 [Imaging Anatomy]Uterus (spoon

technique)– R lateral view– NOTE: from

dorsal to ventral colon uterine body urinary bladder


CVM 6101 [Imaging Anatomy]Uterus (spoon

technique)– R lateral view– NOTE: from

dorsal to ventral colon uterine body urinary bladder


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• Uterus & Ovaries: Contrast Morphology– Hysterosalpingogram

• Cervix• Uterine body• Uterine horns• Oviduct


CVM 6101 [Imaging Anatomy]• Uterus & Ovaries:

Contrast Morphology– Retrograde vaginogram

• Vestibule• Vagina• External urethral orifice • Cervix



• Prostate Gland:– V D and R L/L R views– Beware of superimposed structures including

vertebrae, pelvis, colon/rectum, urinary bladder, nipples, fascial planes, prepuce, etc.

– Remember, the prostate gland position varies with age so position may be as much a function of age as it is size


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Prostate Gland: Broad Anatomic Regions– R lobe– L lobe– Urethral fossa– Note: Not normally visible on neutered dogs.


CT Prostate Sagittal


Prostate Gland– Lateral view– NOTE: should be a

uniform soft tissue opacity


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Prostate Gland– VD view


Interpretive Background: Abdomen• Useful interpretive criteria:

– Prostate gland size (on lateral view) in the dog is measured against the distance between the sacral promontory and the leading edge of the pubic bone (pubic-promontory distance)

• Normally dog prostate gland less than 70 % of the pubic-promontory distance in planes either perpendicular or parallel to the pubic-promontory plane

• Position of canine prostate gland varies with age and it is not abnormal to find the prostate gland outside the pelvic canal in older dogs apparently without prostatic disease

• Remember, neutering should effectively render the canine prostate gland indistinguishable after 4-6 months unless there are other complications


Prostatic Measurement


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• Useful interpretive criteria:– Normally cat prostate glands are not seen and

the role of radiography or ultrasonography in feline prostatic disease has yet to be determined


CVM 6101 [Imaging Anatomy]Sublumbar Lymph Nodes[medial iliac & lumbar aortic]

– Normally not seen on survey radiographs

– Retroperitoneal– Lateral view


Normal medial iliac lymph node

Sublumbar Mass


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Sublumbar Lymph Nodes[medial iliac & lumbar aortic]

– Masses displace descending colon and urinary bladder ventrally

– Lateral view


CVM 6101 [Imaging Anatomy]Major Abdominal

Vessels– Caudal Vena Cava

(CVC) and Aorta (mostly retroperitoneal)

– Portal Vein (intraperitoneal)


– Local/regional masses may invade


Aorta


Vessels– Caudal Vena Cava

(mostly retroperitoneal)


– Local/regional masses may invade


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Vessels– Aorta (mostly

retroperitoneal)– Normally not seen on

survey radiographs– Local/regional masses

may invade



Vessels– Portal Vein

(intraperitoneal)– Normally not seen on

survey radiographs– Subject to anatomic

anomalies



• Remember:– Radiation is “through and through”– Medial Lateral = Lateral Medial

*EXCEPT for effects of gravity on gas, fluid, and organ shape

– Patient anatomy, cooperation, and status may dictate how views are made

– Oblique views facilitate clarification(less superimposition)


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Specific References: ABDOMEN• Grandage J: Posture, gravity and radiographic

interpretation. J Am Vet Radiol Soc 22:80, 1979.

• Grandage J: Radiology of the dog’s diaphragm. J Small Anim Pract 15:1, 1974.

• Bhargava AK, Rudy JL, Diesem CD: Radiographic anatomy of the pleura in dogs as visualized by contrast pleurography. J Am Vet Radiol Soc 10:61, 1969.


General References: ABDOMEN• Thrall DE (ed): Textbook of Veterinary

Diagnostic Radiology. WB Saunders, Philadelphia, 2002.

• Burk RL, Feeney DA: Small Animal Radiology and Ultrasonography. Saunders/Elsevier, Philadelphia, 2003


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