Diagnostic Imaging of the Urogenital Tract Flashcards
What are the 5 main considerations of diagnostic imagine of the urogenital tract?
Mass effect
Effacement
When is prostatomegaly suspicious?
Contrast studies - which study when?
Stones are not equal in radiography
What are the common presentations of urogenital disorders/disease?
Pollakisuria, stranguria, discoloured urine, polyuria, anuria, incontinence, vulval discharge, etc
What are the 3 commonly available methods for imaging the urogenital tract?
Radiography
Contrast radiography
Ultrasound
What is plain radiography useful for?
Shape, size, location, but not internal architecture or ureters
List the pros and cons of plain radiography
Pros:
- Readily accessible
- Low-operator dependency
- Easy to perform
- Low risk
Cons:
- Limited information
- Ionising radiation
What is contrast radiography useful for?
Same as plain radiography + internal architecture or luminal space, ureters
List the pros and cons of contrast radiography
Pros:
- Good quality information
- Readily accessible
Cons:
- Ionising radiation
- Slightly increased risk
- Operator dependent
What is ultrasound useful for?
Shape, size, internal architecture or luminal space, less good ureters
List the pros and cons of ultrasound
Pros:
- High quality information
- No ionising radiation
- Low risk
Cons:
- Slightly less accessible
- Highly operator dependent
Describe the normal appearance of the uterus and ovaries on radiography
Not visible on radiographs unless greatly enlarged
Describe the normal appearance of the uterus and ovaries on ultrasound
Difficult - the body is located between the urinary bladder ventrally and the descending colon dorsally
How does a pyometra appear on radiography?
Dilated, soft tissue opacity loops originating between bladder and colon
Mass effect displacing the intestines cranially and dorsally
How does a pyometra appear on ultrasound?
Fluid dilation of the uterine horns and body
Thin or thick, cystic wall
Where is the prostate located on normal radiography?
Caudal to the bladder, may be partly within the pelvic canal
Describe the size/shape and opacity of the normal prostate on radiography
Size: dependent on neutering status
Rule-of thumb (entire): ≤70% height of the pelvic inlet
Shape: Symmetrical, ovoid to round, urethra centrally
Opacity: homogeneous soft tissue opacity
What are the 3 causes of prostatomegaly?
Benign prostatic hyperplasia
Prostatitis
Prostatic neoplasia
Describe the main features of Benign prostatic hyperplasia
Entire dogs
Symmetrical enlargement
Soft tissue opacity
Describe the main features of prostatitis
Entire dogs!
Most marked enlargement
Regular or irregular shape
May see mineralisation
± Loss of serosal detail
Describe the main features of prostatic neoplasia
Especially in castrated dogs!!
Mineralisation
Asymmetrical
Irregular shape
± Loss of serosal detail
In neutered dog mineralisation very specific for …?
Prostatic neoplasia
Where does prostatic neoplasia metastasize to?
Medial iliac lymph nodes and lumbar vertebrae (periosteal reaction, lysis) and lung
Name 3 contrast studies
Cystography
Retrograde urethrography
Intravenous urography
Which contrast media can be used in cystography?
Positive
- Iodine containing
- NOT barium
Negative
- Air
- CO2 or N2O
Which contrast studies can only use positive iodine containing contrast?
Retrograde urethrography
Intravenous urography
What are the principles of cystography
Catheterise and empty bladder
instill/insufflate with contrast medium (air/gas or iodine-based contrast) until reasonably distended
Describe the uses of a Pneumocystogram
Great for assessment of position and to identify “radiolucent” calculi (urate/cysteine), masses, clots
Describe the uses of a double contrast cystogram
Uses only a small amount of positive contrast and is great for mucosal detail and “radiolucent” stones, masses, clots
Describe the uses of a positive contrast cystogram
Great for position, shape, and most importantly integrity (bladder tears/rupture)
How do the following appear on double contrast cystography:
Calculi
Blood clots
Air bubbles
Calculi = central defects in the contrast pool
Blood clots = may adhere to the bladder wall, often irregular, can appear everywhere
Air bubbles = iatrogenic, at the pool margins
Describe the principles of retrograde urethrogram/vaginourethrogram
- Catheterise, empty bladder, inflate bladder moderately with air/gas (creating back pressure)
- Place catheter tip in tip of penis/just within vulva and clamp
- Inject iodine-based contrast and expose at end of injection
- Needs to be done under GA as it is painful
Describe the principles of intravenous urography
Intravenous injection of iodine-based contrast medium and documentation of its transition through the kidneys, ureters and into the bladder with multiple radiographs
For a diagnostic study of intravenous urography what features are needed?
- Adequate renal function and hydration
- Good patient preparation (fasting, enema)
- GA/heavy sedation
- Multiple VD and lateral radiographs at short intervals
- Time! - Can take up to 2 hours to carry this out
Which contrast is best for visualisation of the bladder?
Cystography
Which contrast is best for visualisation of the urethra (bladder)
Retrograde urethrogram
Which contrast is best for visualisation of the ureters and kidenys
Intravenous urogram
What are the indications for cystography?
Radiolucent calculi, bladder masses, bladder rupture/integrity, chronic cystitis
What are the indications for retrograde urethrography?
Stranguria (urethrolith, stenosis, inflammation, neoplasia), integrity, ectopic ureter
What are the indications for an intravenous urogram?
Suspected ectopic ureter, ureteroliths, ureteral stenosis; renomegaly; integrity
What are the potential problems of intravenous urography?
Inadequate renal function, dehydration, iodine hypersensitivity
Describe the normal radiographic appearance of the bladder
Pear-shaped, smoothly marginated, soft tissue opacity in caudoventral abdomen
Describe the normal appearance of the bladder on ultrasound
Pear-shaped organ in the caudal abdomen with anechoic contents
Describe chronic cystitis on diagnostic imaging
Not visible on plain radiographs
Ultrasound - Irregularly thickened wall, Blood clots
Which contrast is used for cystitis
Double contrast cystography
- Thickened (cranioventral) wall
- Irregular mucosa
- Blood clots
Describe the appearance of different bladder calculi on radiography
Accumulate in the most dependent part of the bladder (centrally)
Visibility depended on radiopacity and size:
- Struvite, oxalate, calcium phosphate: moderate to marked
- Silicate: moderate
- Cystine and urate: non-opaque to faint
Describe the appearance of bladder masses on radiography
Not visible on plain radiographs (effacement).
Defect in the contrast pool or soft tissue opacity on pneumocystogram.
Predilection site: trigonum, dorsal bladder wall
Describe the appearance of bladder masses on ultrasound
Most commonly urothelial cell carcinoma (previously TCC)
Sessile, polypoid echoic mass
What is the most common cause of a bladder rupture
Trauma induced
How can bladder ruptures be diagnosed using diagnostic imaging?
- Plain radiographs: may see loss of serosal detail and small bladder.
- If suspected, do positive contrast cystography.
- Leakage of contrast.
- Ultrasound rarely able to show defect, but will see free fluid
What is the only way to accurately assess the urethra
Through retrograde (vagino)urethrogram - Smoothly marginated, slightly varying diameter
Describe the normal appearance of the kidneys on radiography - location, opacity, shape, margination
Location: retroperitoneal space, left kidney usually more caudally
Opacity: homogeneous soft tissue opacity ± fat at the hilus
Shape: bean-shaped in dog, slightly more rounded in cats
Margination: sharp and smooth
How can you assess if the kidneys are of normal size?
Best assessed on VD radiographs
Dog: length of normal kidneys should be between 2.5 and 3.5x length L2 vertebral body
Cat: normal renal length ~ 1.9-2.6x length L2
Describe the normal appearance of kidneys on ultrasound
Cortex: Echoic, similar or hypoechoic to liver
Medulla: Near anechoic, least echogenicity of all organs
Renal pelvis and diverticula (renal sinus):
- Hyperechoic (bright)
- Should not contain any urine (anechoic)
Renomegaly will cause a mass effect where?
Ventrally displaced colon
List the causes of a unilateral irregular/focal Renomegaly
Neoplasia
Cysts
Abscess, haematoma
List the causes of a bilateral irregular/focal Renomegaly
Neoplasia/metastasis
PKD = polycystic kidney disease
FIP
List the causes of a unilateral smooth (generalised) Renomegaly
Neoplasia
Hydronephrosis
Perinephric pseudocyst
List the causes of a bilateral smooth (generalised) Renomegaly
AKI
Pyelonephritis
Lymphoma
FIP
Pyelectasia and hydronephrosis both show?
Dilation of the renal pelvis
What is pyelectasia?
Mild to moderate dilation secondary to diuresis or inflammation (pyelonephritis)
What is hydronephrosis?
Moderate to severe often secondary to obstruction (ureteral calculi, masses), overall enlargement of the kidney
What are the causes of small kidneys (microrenale)
CKD
Atrophy
Dysplasia (congenital)
Describe the changes seen on diagnostic imaging with CKD
Non-specific and poor correlation with function
Changes with CKD are variable and kidney may appear normal in early stages
‘Classic endstage’: small and irregular, but maybe smooth
Ultrasound: poor corticomedullary definition, small, irregular
Describe the appearance of renal cysts on ultrasound
Renal cysts maybe solitary, develop as part of CKD or if multiple indicate polycystic kidney disease (PKD)
Thin walled
Mostly unicameral
Distal acoustic enhancement
May distort surface
Describe the normal position of ureters on diagnostic imaging
Usually not visible on plain radiographs or ultrasound, but IVU very useful!
Where are the ureters located?
Retroperitoneum, lateral to the spine on VD
Size: 1-2 mm, peristalsis
