Diagnostic Imaging of the Urinary System

How large should the kidneys of dogs and cats be on radiograph?

Dogs 2.5-3.5 x size of L2

Cats neutered 1.9-2.6/entire 2.1-3.2 x L2

What are radiographic contrast studies useful for assessing?

Intrapelvic structures (urethra)

Bladder rupture

With an intravenous urography can see kidneys and ureters

What are the possible contrast medias?

Negative: air, CO2

Positive: iodine based

What should you do before a contrast study?

Take plain images

Enema (easier to see when colon is empty)

What is negative contrast cystogram (pneumocystogram) best for assessing?

Bladder position and wall thickness

What is a positive contrast cystogram best for assessing?

Bladder position, bladder rupture, etc

What is a double contrast cystogram?

Combination of 1-5mL of contrast and then air

What is a double contrast cystogram best for assessing?

Position, luminal content, wall thickness

Which type of bladder contrast study is most useful?

Double contrast cystogram

How is contrast for urethra assessment administered for males?

Retrograde urethrogram: catheter in distal urethra

Demonstrates urethra and possibly prostate

How is contrast for urethra assessment administered for females?

Retrograde vaginourethrogram: catheter through vulva

Demonstrates vestibule, vagina, urethra

Could also inject the contrast into the vestibule rather than using a catheter

Is this short axis or long axis view of the kidney?

Long axis

Short or long axis?

Short

Which kidney is more difficult to image on ultrasound? Why?

Right because it can be quite cranial and dorsal and is often within the ribcage

In which species is the kidney more mobile and rounded (cat or dog)?

Cat

Are ureters usually visible on ultrasound?

Not unless they are distended but can see the proximal aspect at the renal pelvis

What characteristics should you assess about the kidneys during ultrasound?

Location

Size

Shape

Margins

Component (cortex, medulla, corticomedullary junction, pelvis, ureter)

Echogenicity

Echotexture

If you see diffuse parenchymal changes what would be on your differential list?

Acute renal disease/failure

Chronic renal disease

Renal dysplasia

Chronic endstage kidney

Neoplasia (eg lymphoma esp if it is affecting both kidneys)

If you see pelvic dilation/hydronephrosis what would be on your differential list?

Obstruction

Pyelonephritis

Neoplasia

If you see focal changes what would be on your differential list?

Neoplasia

Calculi

Cysts

Abscesses

What does acute renal disease look like on ultrasound?

Rounded, hazy kidney

Reduced corticomedullary definition

• Nephritis

• Tubular necrosis

• Acute renal failure

Appearance could be normal in acute disease

What does chronic renal disease look like on ultrasound?

Changes are non-specific and often bilateral

Heterogenous corticies

Reduced cortico-medullary definition

Indentations suggest old infarcts

What does renal dysplasia look like on ultrasound?

Changes can range from mild to severe

Loss of corticomedullary definition

Distorted outline/abnormal shape

Small/difficult to recognize

Usually seen in young animals

What does chronic endstage kidney disease look like on ultrasound?

Loss of normal architecture

Small/difficult to identify kidney

Often in older animals

Which view is best for viewing pelvic dilation/hydronephrosis?

Short axis view

What does a ureteral obstruction look like on ultrasound?

Normal pelvis shape

Ureter visible to point of obstruction

Check bladder neck and other kidney!

What does neoplasia look like on ultrasound?

Irregular/abnormal shape to pelvis

Disrupted architecture

What do renal masses look like on ultrasound?

Disruption of normal renal architecture

Distortion of outline/abnormal shape

May be difficult to identify kidney if it has been fully infiltrated by the lesion

How are renal masses diagnosed?

Seen on ultrasound, FNA/biopsy for diagnosis

What do calculi look like on ultrasound?

Hyperechoic with shadowing

Located in calyces/pelvis

What do cysts look like on ultrasound?

Anechoic/cloudy

Located anywhere

Can be single or multiple

Usually well defined

What causes renal cysts?

Can be congenital

Associated with chronic inflammation

Polycystic kidney disease (PKD)

What do abscesses look like on ultrasound?

Anechoic/cloudy

Irregular margins

Surrounding reaction

Located anywhere

Different to differentiate from cyst

How thick should the urinary bladder wall be on ultrasound?

1-2mm thick

Is it better if bladder is full or empty when assessing with ultrasound?

Full

More difficult to locate if empty

Must be distended to assess wall thickness

If wall changes are seen on ultrasound of the bladder what should be on your differentials list?

Cystitis

Mass (neoplasia or inflammatory polyps)

Rupture

If contents are seen on ultrasound of the bladder what should be on your differentials list?

Calculi

Blood clots

Cell debris

Emphysematous cystitis

How thick will the bladder walls appear with cystitis?

>0.2cm

What are the differentials for bladder masses? How would you distinguish them?

Neoplasia or inflammatory polyps

Neoplasia can look irregular and can be extensive
If you see layers in the mass it is likely a polyp

What should you check for when ultrasounding bladder masses?

Check for ureteral obstruction or hydronephrosis

What does bladder rupture look like on radiograph?

Free fluid → loss of serosal detail

Defect not visible

Extravasation of contrast

Which types of calculi can you see on radiographs and which can you not?

Can see Struvite and Oxalate (they are radio-opaque)

Cannot see Cysteine or Urate (lucent)

What does gas in the bladder seen on radiograph indicate?

Could be either iatrogenic or emphysematous cystitis

What could suspended content in the bladder seen on a radiograph be?

Concentrated urine

Cell debris

Hemorrhage

Mucus

How can you tell if gas in the bladder is iatrogenic or emphysematous cystitis?

If it is little bubbles that adhere to walls it is emphysematous cystitis

What landmark can you use when finding the prostate on ultrasound?

The proximal urethra - follow the urethra to find it

What does the prostate look like on ultrasound?

Bilobed

Echogenicity similar to spleen

Capsule

How common is benign prostatic hyperplasia and what types of dogs are most susceptable?

VERY common

Entire male dogs

What does benign prostatic hyperplasia look like on ultrasound?

Hyperechoic

Heterogenous

Radiating pattern

Often associated with cysts but not always

What does prostatitis look like on ultrasound?

Acute inflammation: hypoechoic

Chronic inflammation: hyperechoic and mottled

What does prostatic neoplasia look like on ultrasound?

Mottled

Mineralization

Locally invasive

Which dogs are prone to prostatic neoplasia?

Castrated

Where are you likely to see metastasis from prostatic neoplasia?

Pelvis and lumbar vertebrae

Lungs

Differentiate prostatic cysts vs abcesses

Cysts: within prostate, variable size, well defined

Abscess: indistinct margins, cloudy contents, surrounding reaction

Is this a cyst or abscess?

Cyst

Cyst or abscess?

Abscess

Where are para-prostatic cysts located?

Outside the prostate/adjacent to it

What does a para-prostatic cyst look like on imaging

Mineralized rim on radiograph (not all of them)

Looks like multiple bladders on ultrasound

Could be displacing the bladder

Is an ectopic ureter visible on ultrasound?

Only if distended

If insertion is beyond pelvic inlet it is not visible

What type of contrast study?

Negative contrast cystogram (pneumocystogram)

What type of contrast study?

Double contrast cystogram

What type of contrast study?

Positive contrast cystogram