Imaging of the urinary system Flashcards
What do kidneys look like on US?
Cat - oval
Dog - bean
Should be good corticomedullary definition
Cortex is hypoechoic compared to the spleen
Medulla is hypoechoic compared to the cortex
Renal pelvis <2mm
What size should the kidney be?
Cat - 3.7-4.4
Dog - 5.5-9.1 x aorta diameter
What suggests an obstruction?
Defintely if renal pelvis >13mm
But below that can also be obstructed
What can cause renal pelvis dilation?
PUPD
IVFT
Pyelonephritis
Obstruction (stricture/ ligature/ ureterolith/ cells)
What are normal findings in bladder radiography?
bladder is of homogenous fluid opacity, is in size and shape, may be partially located within the pelvic canal.
Intrapelvic location of the bladder may be noted, there is unclear clinical significance.
The normal urethra is not visible on survey radiographs.
With contrast, normal urinary bladder has a wall thickness of 1 mm (cats) to 2 mm (dogs) and has a smooth mucosal surface
Although generally considered safe, what are the possible adverse events associated with contrast cystography?
hematuria, infection, (hemorrhagic) cystitis or urethritis, dissection of contrast medium into the bladder wall, iatrogenic bladder or urethral rupture, knotting or breakage of the catheter, and air embolization if using room air as contrast agent
What can positive cystogram be used for?
bladder rupture or abnormal communication with adjacent structures (eg, urethrorectal fistula)
Distinguishing the urinary bladder from caudal abdominal masses
Evaluating the position of the urinary bladder in the case of abdominal, inguinal, or perineal hernias.
What is double contrast cystography used for?
evaluating mural and luminal bladder lesions
Method of choice for the evaluation of the urinary bladder if ultrasonography is not available.
When does the urethra not appear equal in contrast radiography?
The prostatic urethra in dogs is wider than the membranous urethra
In male dogs mild narrowing may be observed at the ischial arch
The penile urethra in cats narrows progressively from the ischial arch to the external urethral orifice.
The colliculus seminalis may appear as a physiologic focal filling defect in male dogs and cats.
In cats a physiologic filling defect is associated with the dorsal urethra representing the urethral crest
What is acoustic shadowing and what causes it in the urinary tract?
Acoustic shadowing occurs because of mineral or air interfaces causing loss of echo intensity deep to the interface because of absorption and/or reflection. Mineral interfaces such as uroliths typically cause strong distal hypoechoic to anechoic shadows. Air interfaces typically cause echogenic (“dirty”) distal shadows because of concurrent reverberation artifact. This artifact is seen when gas is present within the bladder lumen or wall
What may cause debris within the bladder?
crystals, protein, cells, cellular debris, calculi, or fat droplets, and urinalysis is necessary for evaluation of the clinical significance
How may advanced imaging be used to assess the lower urinary tract?
CT excretory urography to evaluate the ureterovesicular junction in patients with suspected ureteral ectopia
CT or MRI to evaluate intrapelvic lesions.
assessing origin and extent of intrapelvic masses, identifying lesions associated with the pelvic urethra such as wall thickening or calculi, and evaluating surrounding structures including the spine and regional lymph nodes for the presence of additional lesions (eg, metastatic disease).
CT has proven superior to ultrasound in accurately measuring the size of bladder wall masses
How may cystitis or urethritis appear on imaging?
may not show any abnormalities in early or mild cases. In chronic/ more severe cases ultrasound or double-contrast cystography may show diffuse thickening and irregularity of the urinary bladder wall, especially in the cranioventral portion of the bladder
May also see intraluminal material due to the presence of inflammatory products and/or hemorrhage, mineral sediment, or cystic calculi. Mineralization of the bladder wall secondary to severe chronic cystitis has been described but is very rare
What is emphysematous cystitis?
due to infection with gas-producing bacteria such as Escherichia coli or Clostridium species
most commonly seen in animals with diabetes mellitus but may affect other patients as well.
How does emphysematous cystitis appear on imaging?
on survey radiographs - variable size gas opacities associated with the bladder wall (and possibly the lumen)
Ultrasonographically, these gas inclusions appear as hyperechoic areas with distal reverberation artifacts.
Care must be taken to distinguish these pathologic gas accumulations from intraluminal gas introduced during cystocentesis, catheterization, or endoscopy, and this can be accomplished by repositioning the dog.
