A10. Urinary tract imaging: Purpose, and indications

A variety of imaging modalities are used in the evaluation of the urinary tract.

CT urography

CT urography refers to a contrast CT taken in a phase where the contrast has entered the urinary system. It's one of the most commonly used procedures used to image the upper urinary tract (renal pelvis and ureters).

Procedure
- A non-contrast CT is taken
- IV contrast is injected
- Several CT scans are taken afterwards when the contrast is in the urinary system
Is generally used instead of regular x-rays and IV urography
Indications
- Gold standard for stones and renal masses
- Staging of renal and bladder cancers
- Hydronephrosis
- Trauma
- Retroperitoneal masses
- Retroperitoneal lymph nodes
- Adrenal masses

Ultrasound

Ultrasound is also widely used in the evaluation of the urinary tract. It may be used to evaluate the kidneys, look for kidney stone, measure bladder volume, and evaluate the testicles. When a transrectal probe is used, the prostate can be evaluated as well.

Indications
- Renal tumour
- Renal cysts
- Nephrolithiasis (not as good as CT)
- To guide kidney biopsy or intervention
- Hydronephrosis
- Bladder stone
- Urinary retention
  - Ultrasound can measure the amount of urine remaining in the bladder after urination
- Testicular torsion
- Cryptorchidism
- Epididymitis
Can also evaluate
- Kidney
  - Size
  - Shape
  - Location
  - Masses
  - Cysts
- Bladder
  - Size
  - Wall thickness
  - Colour doppler allows visualization of the ureteral jet
- Prostate
  - Using transrectal probe
  - Size
  - Shape
  - Masses
- Scrotum
  - Presence/absence
  - Cryptorchidism in the inguinal canal
  - Inguinal lymph nodes

Modalities which are rarely used

These modalities have largely been replaced by CT urography.

Plain abdominal x-ray
- Also called kidney-ureter-bladder (KUB) film
- Not much used
- Indications
  - Stones
    - Only those with high calcium content
  - Calcifications
  - Evaluate position of urinary stents
Intravenous (IV) urography
- Not much used (replaced by CT)
- Also called IV pyelography or excretory urography
- Procedure
  - A normal KUB (a scout film) is taken
  - IV contrast is applied
  - X-rays taken 5, 10, and 15 minutes after IV
  - As the contrast is filtered by the kidneys and excreted, different parts of the urinary tracts are visible
- Indications
  - Stones
    - Can see all stones
  - Haematuria
Retrograde urography
- Procedure
  - A ureteral catheter is placed by cystoscopy
  - The catheter is advanced to the renal pelvis
  - A scout image is taken
  - Contrast is retrogradely instilled into the renal pelvis through the catheter
  - Fluoroscopic images are taken
- Indications
  - Same as IV urography, but used in case of contrast allergy
Anterograde urography
- Procedure
  - A catheter is inserted percutaneously into the renal pelvis
  - A scout image is taken
  - Contrast is anterogradely instilled into the renal pelvis
  - Fluoroscopic images are taken
- Indications
  - Same as retrograde urography, but used in cases where retrograde is impossible
Static cystography
- Procedure
  - Scout image is taken
  - A Foley catheter is placed
  - Contrast material is instilled into the bladder through the catheter
  - Multiple images are taken with the bladder full of contrast
  - The contrast is drained out of the bladder
  - A post-drainage image is taken
- Indications
  - Bladder trauma
  - Bladder fistulae
Voiding cystography
- Procedure
  - Scout image is taken
  - A Foley catheter is placed
  - Contrast material is instilled into the bladder through the catheter
  - The catheter is withdrawn
  - Fluoroscopy is taken while the patient voids the contrast
- Indications
  - Vesicoureteral reflux
  - Voiding problems
  - Evaluation of posterior urethra
MRI
- May be used if CT is contraindicated or for staging of malignancy