Diagnostic Imaging of the Urinary Tract

Question 1

1. What parts of the urinary tract do you see on radiographs?
2. What part of the urinary tract do you not usually see on radiographs?
3. What part of the urinary tract MAY you see on radiographs?

Answer 1

1. Kidneys, bladder.
2. Ureters, urethra, ovaries.
3. Prostate, uterus.

Question 2

1. Kidneys location on radiograph?
2. Position of right compared to left?

Answer 2

1. Cranial to mid-dorsal abdomen.
2. Right usually lies cranial to the left.
   Often ‘overlap’ on lateral projection.

Question 3

What can be assessed regarding the kidneys on plain radiographs?

Answer 3

Size.
Shape - kidney bean/ovoid. Margination - smooth edges.
Number - 2.
Radiopacity - expect to be soft tissue but may be mineralised.
Position - not likely to change positions due to own pathology but because of pathology of other organs around them.

Question 4

How is kidney size measured on radiograph?

Answer 4

Measure in respect to length of L2.
- dogs – 2.5-3.5 x L2.
- cats – 2.4-3 x L2.
–> 2 x L2 in some ‘normal’ older cats but this does not exclude subclinical renal disease.
VD view best to take for these measurements as helps to separate the right kidney from the left.

Question 5

What kidney abnormalities may be seen on plain radiographs?

Answer 5

mineralisation.
- nephroliths – more round.
- mineralisation of renal tissue itself due to damage.

Question 6

1. Normal bladder position on plain radiograph?
2. Bladder assessment on plain radiograph?
3. Bladder assessment on contrast radiograph?

Answer 6

1. Entirely within the abdomen.
   Neck of bladder around the level of the pelvic brim.
   - incontinence in females = bladder sat back.
2. Is bladder visible at all?
   Is there any change in opacity?
   - radiopaque calculi.
   - emphysematous cystitis.
3. Wall thickness.
   Mucosal surface.
   Filling defects.

Question 7

1. Urethra on plain radiograph.
2. Retrograde contrast study assesses for what in the urethra?

Answer 7

1. Only visible if calculi.
2. Rupture.
   Urethritis / tumour.
   Stricture.

Question 8

1. Position of the prostate on radiograph?
2. Normal prostate size on radiograph?
3. Normal prostate shape on contrast radiograph?
4. Opacity of prostate on radiograph?

Answer 8

1. Intra-pelvic so may not be visible.
   Intra-abdominal if enlarged.
   - often incidental in older, entire male dogs.
2. <70% sacral promontory to pubic brim.
3. Symmetrical around urethra on contrast study.
   - for differentiation of hyperplasia compared to neoplasm or abscessation.
4. Mineralisation or gas may be visible.

Question 9

Differential diagnoses for prostatomegaly?

Answer 9

Benign prostatic hyperplasia (BPH).
Prostatitis.
Abscess.
Neoplasia - look for concurrent vertebral changes – paraneoplastic irregular new bone formation on the back of the lumbar spine, pelvis, caudal vertebrae.
May see paraprostatic cysts:
- usually seen as separate soft tissue masses. May be attached via stalk-like connections.
- May mineralise.

Question 10

Uterus on radiograph.

Answer 10

Occasionally see normal uterus on radiograph.
If enlarged:
- pregnant?
- recent parturition?
- pyometra?
- hydrometra?

Question 11

Pregnancy on radiograph?

Answer 11

3-4w - round soft tissue ‘masses’.
5-6w - large coiled tubular structure.
6-6.5w - foetal mineralisation.
Can check foetal viability on radiograph but only see changes if decay started:
- gas/overlap cranial bones (Spalding’s sign).
BUT ultrasound is better for foetal assessment.

Question 12

1. Why are contrast studies commonly done for the urinary tract?
2. Common contrast studies carried out for the urinary tract?

Answer 12

1. Plain radiographs are limited in terms of contrast between structures and seeing small structures.
2. Intravenous urography - allows us to see kidneys.
   Cystography - allows us to see the bladder.
   Urethrography - allows us to see the urethra.

Question 13

What type of contrast medium should be used for the urinary tract?

Answer 13

Water soluble.
NOT barium - irritant and causes granuloma formation.
Does not matter if ionic or non-ionic but would probably prefer non-ionic over ionic.

Question 14

Excretory urography.
- what can be assessed?
- how administered?
- indications?
- timings?

Answer 14

• Identify / assess kidneys.
• Assess ureters.
• Vesicoureteral junction.
• Bolus of iodinated contrast given into peripheral vein.
• Indicated for:
  – Persistent urinary tract infections.
  – Urinary incontinence.
  – Haematuria.
  – Suspected renal abnormalities.
  –> survey films, palpation.
• Timings:
  – immediately: nephrogram (VD).
  – 5 mins: pyelogram (VD) (renal pelvis).
  – 10 mins: ureterogram (lateral).
  – 15 mins: ureterovesicular junction (lateral).

Question 15

1. Complications of excretory urography?

Answer 15

1. • contrast-induced renal failure.
     – failure of renal pelvis/ureters to opacify.
     – start IV fluids and administer diuretics.
     – usually reversible.
     - anaphylaxis.

Question 16

1. What does cystography do?
2. How is contrast introduced?
3. Types of cystography?

Answer 16

1. Delineates the bladder.
2. Via urinary catheter.
3. • Pneumocystogram – air only, bladder location, shows large masses / marked thickening.
     - Positive contrast cystogram – Iodinated contrast, to establish leakage from the bladder.
     - Double contrast cystogram – both air and positive contrast, delineates wall and contents.

Question 17

Cystography indications.

Answer 17

Dysuria.
Haematuria.
Persistent UTIs.
Pelvic trauma.
To identify bladder e.g. if displaced into rupture / hernia.

Question 18

Potential complications of cystography.

Answer 18

Iatrogenic rupture - no over-filling.
Damage to mucosa by catheter tip.
Air leakage into broad ligament (not serious).
‘Knotting’ of catheter.
Catheterisation of ectopic ureter or reflux - may lead to pyelonephritis.
Air embolism - rare.
– may minimise risk by keeping animal in LEFT lateral recumbency.
–> as traps air in the right ventricular outflow tract rather than going out into the lung.

Question 19

1. What does vaginography / urethrography delineate?
2. What contrast medium is used?
3. How is contrast introduced?
4. At what point is the radiograph taken?

Answer 19

1. Delineates urethra (and vagina).
2. Water-soluble iodinated contrast medium.
3. Foley catheter into distal urethra / vestibule.
4. Taken at end of injection.

Question 20

1. Indications for vaginography / urethrography?
2. Possible complication of vaginography / urethrography?

Answer 20

1. Dysuria.
   Haematuria.
   Persistent UTIs.
   Pelvic trauma.
   To identify bladder e.g. if displaced into rupture / hernia.
   *often precedes a cystography study.
2. Urethral damage.