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DIAGNOSTIC IMAGING > 3 – Abdominal Radiographic Principles and Anatomy > Flashcards

3 – Abdominal Radiographic Principles and Anatomy Flashcards

1
Q

Effacement/silhouetting

A
  • If 2 structures of the same opacity are contacting, we cannot tell their margins apart
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2
Q

kVp

A
  • Energy of X-ray photons
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3
Q

mAs

A
  • Amount of X-ray photons
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4
Q

Image optimization

A
  • Thoracic has high intrinsic contrast (gas filled lungs surrounding soft tissue CV structures)
    o Uses high KvP and lower mAs
  • Abdomen has low intrinsic contract
    o Uses lower kVp and higher mAs
    o Show narrow scale of grey and can exaggerate the intrinsic contrast of abdominal content
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5
Q

What are the standard view for abdominal radiographs?

A
  • Left lateral
  • Right lateral
  • Ventrodorsal
  • *include the entire abdomen (large dogs may need 2 images per view)
    o Few cm cranial to diaphragm and few cm caudal to coxofemoral joints
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6
Q

Positioning tips

A
  • Keep pelvic limbs relax to allow expansion of abdominal cavity and prevent skin folds
    o Perpendicular to spine on lateral view
    o Flexed (frog leg) in VD view (otherwise will get a skin fold)
  • Take exposure at end expiration to allow expansion of abdominal cavity and reduce organ crowding
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7
Q

Straight radiographs: how do you check?

A
  • Lateral views: Transverse process of vertebrae should be superimposed on lateral views (“Nike swoosh”)
  • VD view: spinous process of the vertebrae should be end on
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8
Q

What is a systematic approach for looking at abdominal radiographs?

A
  • Peritoneal and retroperitoneal spaces: contrast
  • GIT
  • Parenchymal organs
  • Abdominal walls, diaphragm
  • Extra-abdominal structures
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9
Q

What should be visible normally in the abdomen?

A
  • Peritoneal space
    o GIT
    o Liver
    o Spleen
    o Pancreas
    o Urinary bladder (not when empty)
    o Prostate
    o Uterus (if distended)
  • Retroperitoneal space
    o Kidneys
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10
Q

What organs are considered peritoneal?

A
  • Those ENTIRELY covered with visceral peritoneum
    o Liver, gallbladder, spleen, pancreas, GIT, mesenteric lymph nodes, blood vessels
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11
Q

What organs are considered retroperitoneal?

A
  • Those only PARTIALLY covered by visceral peritoneum
    o Kidneys, ureters, adrenal glands, major blood vessels, aortic lymph nodes
  • *communicates cranially with the mediastinum through the aortic hiatus in the diaphragm
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12
Q

What is “serosal detail” or “serosal contrast”?

A
  • Ability to see the margins of abdominal organs
  • *fat is present in both spaces and provides contrast for visualization of soft tissue opaque organs
    o Can be altered with decreased fluid/soft tissue added OR increased when gas opacity is added
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13
Q

Decrease in serosal detail: causes/reasons

A
  • Lack of intraabdominal fat (emaciated animals, young animals)
  • Presence of brown fat in young animals (ex. 2-3 months old)
    o Higher water content (closer to soft tissue opaque)
  • Superimposed external material
  • Underexposure
  • Diseases (pathological)
  • Ex. ascites
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14
Q

Increase in serosal detail: causes/reasons

A
  • Due to free gas within peritoneal/retroperitoneal space=pneumoperitoneum/pneumoretroperitoneum
  • Often pathological
  • Can be post-operative (can last up to 3 weeks, volume should decrease over time)
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15
Q

What can be used to help ID pneumoperitoneum?

A
  • Horizontal beam radiography
  • Free gas will gloat against gravity to the highest point of abdomen
    o Look under ribs on a horizontal beam VD view
    o Look under xyphoid on a horizontal beam lateral view
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16
Q

What are the differences in canine and feline stomach position?

A
  • On VD/DV projection
    o Dog pylorus extends RIGHT CRANIAL peritoneum
    o Cat pylorus stays close to midline
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17
Q

Rugal folds

A
  • More in the fundic area
  • Can see more when there is gas content
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18
Q

Feline gastric wall

A
  • Like to deposit fat into it=normal
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19
Q

What is the purpose of 2 lateral views when looking at the stomach?

A
  • Helps evaluate different parts of the stomach
  • Fundus sits in left dorsal abdomen
  • Pylorus sits in right ventral abdomen
  • *gravity effects gas and fluid distribution in the gastric lumen
    o On left lateral: fluid fills the fundus, gas fills the pylorus
    o On right lateral: fluid fills pylorus, gas fills the fundus
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20
Q

Duodenum

A
  • Fairly consistent position
  • Diameter may be slightly larger than jejunum
  • Parts
    o Duodenal bulb/cranial duodenal flexure
    o Descending duodenum
    o Caudal duodenal flexure
    o Ascending duodenum
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21
Q

Canine duodenal Peyer’s patches (‘pseudoulcers’)

A
  • Normal anatomy
  • Lymphoid aggregates on the antimesenteric border of the GIT
  • More prominent in YOUNG dogs
  • Don’t mistake them for pathological ulcers
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22
Q

What is the normal feline SI appearance?

A
  • ‘string of pearls’=represents NORMAL peristalsis
  • In fat cats with large amount of peritoneal fat, SI can appear centralized in one region of the peritoneum
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23
Q

SI luminal gas

A
  • Normal to see SOME
  • Amount varies with species: typically dogs > cats
  • Post-prandial GIT tend to contain more gas
  • Distressed or dyspneic patient can have more gas due to aerophagia
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24
Q

Large intestine

A
  • Cecum, colon, rectum
  • Often see cecum in dogs but NOT cats
  • Colon: ascending, transverse, descending
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25
Cecum: dog
- Distinct cecum - Right cranial to mid abdomen - Blind ended, coiled, commonly gas filled
26
Cecum: cat
- Less developed compared to dog o NO cecocolic sphincter - Occasionally seen on radiographs as a small blind end out-pouch
27
Normal intestinal diameter
- Measured serosa to serosa - SI o Dogs: <1.6 times L5 height on lateral o Cats: <12mm or <2 times L2 endplate height on lateral - Colon o Cats: <1.28 times L length on lateral radiographs - *DO NOT MEASURE GI WALL THICKNESS ON RADIOGRAPHS
28
GIT special procedures: contrast studies
- ALWAYS perform plain survey radiographs first - Positive contrast: agents more opaque than GI content (ex. barium, iodine) - Negative contrast: agents more lucent than GI content (ex. room air, CO2) - Indications: determine location, transit time, ID obstruction - Contraindications: lesion visible on normal radiographs, GIT perforation suspected - Challenges: long procedure, sedation and stress affect transit time - Ex. esophagram, gastrogram, upper GI, colonogram
29
Pancreas
- Normally NOT seen radiographically o Other than occasionally the LEFT lobe is visible in cats (‘fat cats’) - Ultrasound: difficult to see for untrained eyes, all about anatomy
30
*Liver
- lies b/w diaphragm (cranially) and stomach (caudally) - homogenously soft tissue opaque - assessment of liver size best made by noting the position of the stomach (“gastric axis”) - caudoventral liver margin should be a SHARP TRIANGLE, w/o extending much beyond the costochondral arches on the lateral view o variation with different canine body conformation (feline=more consistence) o mild variation with respiratory phase
31
Normal barrel-chested dog
- liver can extend slightly beyond the costal arches - BUT still sharply margined
32
Normal deep-chested dog
- Liver well contained within the costal arches
33
Liver: species differences on VD view
- Cat liver sits more towards the right side than in dogs
34
*Gastric axis
- INDIRECT measurement for liver size - Normal range: perpendicular to vertebral column to parallel with intercostal spaces o Want it between the 2 lines!
35
*Gastric axis: hepatomegaly
- Liver extends too far beyond the ribs - Rounded margins - Use gas cap in stomach to draw gastric axis o *caudal deviation of the gastric axis!
36
*Gastric axis: microhepatia
- *cranial deviation
37
Liver on ultrasound
- Coarse echotexture - Portal veins have HYPERECHOIC walls compared to hepatic veins
38
Gall bladder: radiograph
- Located to right of midline - Homogenously fluid opaque - Normally, NOT visible as superimposed and effaced by liver o Occasionally seen in cats: ventral border of it can protrude slightly BEYOND liver border on lateral view
39
Gall bladder on ultrasound
- Contains anechoic (dark=black) bile - Thin walled - Surrounded by liver parenchyma - Might see precipitate in the gall bladder: incidental in older dogs
40
Canine spleen
- Head of spleen is FIXED in dorsal left abdominal quadrant by the gastrosplenic ligament - Distal end/tail is MOVEABLE and can even fold upon itself
41
Feline spleen
- Thinner and smaller than in dogs - Splenic tail is LESS variable in location: sits along LEFT ABDOMEN o Should NOT see splenic tail on lateral radiograph
42
Splenomegaly
- Feline: will see tail on lateral view (ex. sedation, splenitis, lymphoma) - Canine: subjective, rounded margins, pushing things dorsally and caudally
43
Spleen on ultrasound
- Fine echotexture - Splenic veins at hilus (just one set) - More echogenic than liver
44
Kidneys
- L kidney is left behind (CAUDAL) - Cranial pole of R kidney effaces with R liver (renal fossa of caudate lobe) - Normal fat opacity in feline renal hilus: radiolucent area in renal hilus
45
*How do you measure renal length?
- On VD projection - Avoid overlap of renal silouettes - Avoid uneven magnification - Dogs: 2.5-3.5 x L2 length - Cats: 2-3 x L2 length
46
Kidney on ultrasound
- Smooth margination - Well-defined corticomedullary distinction o Medulla more hypoechoic than cortex - Collapsed renal pelvis w/o fluid dilation
47
*Ureters
- When normal, not visible on plain radiographs or US - Sometimes able to see soft tissue opaque nodule-like structures in plane of caudal ureters in dogs on lateral radiographs o End on deep circumflex iliac vessels
48
Excretory urography: urinary system special procedure
- Positive contrast administered IV (ex. iodine, NOT barium-based contrasts) - Visualize urinary structures that are normally not visible - Can indirectly evaluate renal function - Risks: may have immediate adverse reactions, contrast-induced acute renal failure (rare) - Contraindications: dehydrated, hypotension, acnuric renal failure, known hypersensitivity
49
What are the 3 phases of excretory urogram?
1. Vascular phase: 5-7s (difficult to capture) a. Opacification of renal arteries 2. Nephrogram phase: 10s-2mins after injection a. Opacification of renal parenchyma b. Cortex is first then medulla c. Gradually fade out 3. Pyelogram phase: last a variable amount of time depending on a. Contrast dose b. Renal perfusion c. GFR d. Patient hydration status e. Patency of urinary system
50
Urinary bladder and urethra
- Bladder visibility depends on size - Urethra normally NOT visible on plain radiographs o Need special procedure (retrograde cystourethrogram)
51
Urinary bladder on ultrasound
- Anechoic urine - Wall thickness can vary with distention but should always be even and smooth o Should be thin and smooth
52
Retrograde(vagino) cystourethrogram
- Imaging studies after a positive contrast agent is administered RETROGRADE via the urethra - Positive contrast: iodine (NOT barium-based contents) - Locate lower urinary tract, look for leakage/rupture, evaluate intraluminal and intramural diseases What are some potential complications with retrograde(vagino) cystourethrogram? - Iatrogenic trauma to lower urinary tract during catheterization - Knotting of urinary catheter within the bladder - Very rarely: gas embolization into vascular system (can result in serious pulmonary embolism)
53
*Additional view for male dog: urinary system
- Consider additional lateral view with hip flexed (‘butt shot’) to evaluate the penile urethra without superimposition
54
What are some other pitfalls of male dog (urinary system)?
- Nipples on prepuce - Secondary centre of ossification of the os penis o Typically at proximal end of ox o Aligned with os penis: easily mistaken for stone or os penis fracture
55
Mineralized os penis in cats
- Seen in 38% of cats - Don’t mistake it for urolith/calculi
56
*Prostate
- Visibility depends on reproductive status - Large and more variable in intact male dogs: benign prostatic hyperplasia o ‘double bubble’ appearance - Atrophied and NOT visible in neutered male dogs, unless disease - NOT visible in cats
57
Prostate on ultrasound
- Small in neutered males - Large in intact males: bilobed, symmetrical, smooth margination
58
Uterus
- Visibility depends on reproductive status o NOT visible in spayed or anestrus animals o More visible with distention (pregnancy, diseases) - Pregnancy can be diagnosed on rads after fetal mineralization (43d in dog, 38d in cat)
59
Distended uterus
- Soft tissue/fluid opaque tubular structure in CAUDAL peritoneum, coursing between colon and urinary bladder o Small intestines would NOT go that caudal
60
*Uterus on ultrasound
- “micky mouse sign” suggests distended uterus

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