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
2
Q
kVp
A
- Energy of X-ray photons
3
Q
mAs
A
- Amount of X-ray photons
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
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
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
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
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
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
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
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
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
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
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)
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
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
17
Q
Rugal folds
A
- More in the fundic area
- Can see more when there is gas content
18
Q
Feline gastric wall
A
- Like to deposit fat into it=normal
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
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
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
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
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
24
Q
Large intestine
A
- Cecum, colon, rectum
- Often see cecum in dogs but NOT cats
- Colon: ascending, transverse, descending
25
Q
Cecum: dog
A
- Distinct cecum
- Right cranial to mid abdomen
- Blind ended, coiled, commonly gas filled
26
Q
Cecum: cat
A
- Less developed compared to dog
o NO cecocolic sphincter - Occasionally seen on radiographs as a small blind end out-pouch
27
Q
Normal intestinal diameter
A
- 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
Q
GIT special procedures: contrast studies
A
- 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
Q
Pancreas
A
- 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
Q
*Liver
A
- 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
Q
Normal barrel-chested dog
A
- liver can extend slightly beyond the costal arches
- BUT still sharply margined
32
Q
Normal deep-chested dog
A
- Liver well contained within the costal arches
33
Q
Liver: species differences on VD view
A
- Cat liver sits more towards the right side than in dogs
34
Q
*Gastric axis
A
- INDIRECT measurement for liver size
- Normal range: perpendicular to vertebral column to parallel with intercostal spaces
o Want it between the 2 lines!
35
Q
*Gastric axis: hepatomegaly
A
- 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
Q
*Gastric axis: microhepatia
A
- *cranial deviation
37
Q
Liver on ultrasound
A
- Coarse echotexture
- Portal veins have HYPERECHOIC walls compared to hepatic veins
38
Q
Gall bladder: radiograph
A
- 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
Q
Gall bladder on ultrasound
A
- Contains anechoic (dark=black) bile
- Thin walled
- Surrounded by liver parenchyma
- Might see precipitate in the gall bladder: incidental in older dogs
40
Q
Canine spleen
A
- 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
Q
Feline spleen
A
- 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
Q
Splenomegaly
A
- Feline: will see tail on lateral view (ex. sedation, splenitis, lymphoma)
- Canine: subjective, rounded margins, pushing things dorsally and caudally
43
Q
Spleen on ultrasound
A
- Fine echotexture
- Splenic veins at hilus (just one set)
- More echogenic than liver
44
Q
Kidneys
A
- 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
Q
*How do you measure renal length?
A
- 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
Q
Kidney on ultrasound
A
- Smooth margination
- Well-defined corticomedullary distinction
o Medulla more hypoechoic than cortex - Collapsed renal pelvis w/o fluid dilation
47
Q
*Ureters
A
- 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
Q
Excretory urography: urinary system special procedure
A
- 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
Q
What are the 3 phases of excretory urogram?
A
- Vascular phase: 5-7s (difficult to capture)
a. Opacification of renal arteries - Nephrogram phase: 10s-2mins after injection
a. Opacification of renal parenchyma
b. Cortex is first then medulla
c. Gradually fade out - 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
Q
Urinary bladder and urethra
A
- Bladder visibility depends on size
- Urethra normally NOT visible on plain radiographs
o Need special procedure (retrograde cystourethrogram)
51
Q
Urinary bladder on ultrasound
A
- Anechoic urine
- Wall thickness can vary with distention but should always be even and smooth
o Should be thin and smooth
52
Q
Retrograde(vagino) cystourethrogram
A
- 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
Q
*Additional view for male dog: urinary system
A
- Consider additional lateral view with hip flexed (‘butt shot’) to evaluate the penile urethra without superimposition
54
Q
What are some other pitfalls of male dog (urinary system)?
A
- 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
Q
Mineralized os penis in cats
A
- Seen in 38% of cats
- Don’t mistake it for urolith/calculi
56
Q
*Prostate
A
- 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
Q
Prostate on ultrasound
A
- Small in neutered males
- Large in intact males: bilobed, symmetrical, smooth margination
58
Q
Uterus
A
- 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
Q
Distended uterus
A
- Soft tissue/fluid opaque tubular structure in CAUDAL peritoneum, coursing between colon and urinary bladder
o Small intestines would NOT go that caudal
60
Q
*Uterus on ultrasound
A
- “micky mouse sign” suggests distended uterus
