Imaging the urinary tract: Correct use of radiography and ultrasonography (Proceedings)

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Imaging the urinary tract: Correct use of radiography and ultrasonography (Proceedings)

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Apr 01, 2010

Survey radiography is commonly used to image the urinary tract and provides information on size, shape, opacity, location and, margination of urinary organs. This modality is rapid and cost effective for screening animals with suspected urinary tract disease. Contrast procedures, including cystography and excretory urography, are special radiographic procedures that provide additional information. Cystography is performed with positive and or negative contrast media and is used to identify calculi, mural changes and bladder rupture. Positive contrast urethrography is often performed in male dogs and cats to detect urethral lesions such as stenosis, rupture or calculi. Excretory urography opacifies the excretory pathway-kidneys to urethra and is valuable for studying the renal parenchyma, pelvises, ureters and urinary bladder.

The urinary tract is commonly evaluated when clinical signs of urinary tract problems are observed and is complimentary to radiographic findings because the internal architecture of organs can be observed...

Ultrasonography is useful for evaluating the presence of lower (bladder and urethra) and upper (kidneys and ureters) urinary tract disease. Diagnostic information can be obtained at little or no risk to the animal and is not compromised by the presence of disease. Urinary tract ultrasonography is often used in lieu of excretory urography and cystography.

Radiography of the urinary tract

• Technical considerations
     o Regular or high speed screens with long scale contrast if analog
     o Digital images provide excellent scale of contrast and are equal or superior to analog
     o Two views = standard, must make extra lateral to visualize os penis and urethral in males.
• Conditions identified with survey radiography
     o Renomegaly and decreased renal size
     o Change in shape
     o Solitary kidney
     o Retroperitoneal swelling/loss of contrast
     o Radiopaque urocalculi
     o Bladder masses
• Excretory urography
     o Indications
1) Confirming rupture of the excretory pathway
• Pelvis, ureter and bladder
• Important in trauma cases
2) To determine renal size, shape and location
3) Confirm renal mass lesions suspected on survey radiographs
4) Visualization of the renal pelves, ureters and urinary bladder (ex. ectopic ureters)
5) Qualitative assessment of renal function
• Nuclear scintigraphy is superior—GFR
     o Contraindications
1) Dehydration, anuria, severe proteinuria and co-existing congestive heart failure are the most important contraindications in veterinary medicine.
2) Hypersensitivity (rare).
     o Technique
1) Contrast media
• Ionic iodinated media
     o Meglumine and sodium diatrizoates or iothalamates
     o Dose = 400 mg iodine / lb BW, IV
• Non ionic iodinated media—expensive, carry less risk for hypersensitivity.
2) Two views-immediate, 5 min, 15 min, 30 min, 45 min. Oblique views for ureters.
• Cystography
     o Includes pneumocystography, double contrast cystography (DCT) and positive contrast cystography
     o Conditions identified
1) Bladder rupture (positive contrast)
2) Cystitis (double contrast)
3) Neoplasia
4) cystic calculi (double contrast)
5) Location of urinary bladder in relation to surrounding viscera, e.g. prostate (pneumocystography). Defines prostate
6) Anatomic defects (double contrast)
     o Contraindications
1) Known hypersensitivity to iodinated contrast media (rare)
2) Known vascular lesion—pneumocystogram-risk for air embolism
     o Contrast media
• Air or carbon dioxide
1) Ionic iodinated media (sometimes diluted 50/50 w/ HOH)
2) Can also use non ionic, but more expensive
     o Notes
1) Balloon tipped catheters recommended
2) Distend urinary bladder fully and to effect, do not calculate dose and inject—palpate while injecting and stop when distended. For instance fibrotic urinary bladders will not distend normally.
3) For DCT, add air, then contrast medium to prevent air bubbles
4) Make x4 90 degree orthogonal projections for DCT.
• Urethrocystography
     o Indications
1) Diagnosis of strictures, calculi, neoplasms and rupture of the urethra
2) Partial or complete urinary obstruction
3) Evaluation of the prostate
4) Contraindication-patient at risk for air embolism
     o Contrast media
1) Air, perform pneumocystogram first
2) Same as for cystogram
     o Notes
1) Best suited for males
2) Make radiographic exposure during mid-injection
3) Additional lesions may be identified with simultaneous pneumocystogram.