Veterinary Medicine - October 2008 - (Page 543)

ably with double-contrast cystography in detecting urocystoliths and determining urolith numbers in one study, double-contrast cystography has the added bene t of being a sensitive and speci c indicator of urolith shape and size.2,3 When imaging patients with con rmed urolithiasis or with clinical signs suggestive of urolithiasis, include as much of the urethra as possible since uroliths could be missed (Figures 1A & 1B). Position identi cation labels and other imaging markers so they do not obscure any part of the urinary tract (Figure 1B). If initial imaging results do not reveal an obvious cause of the patient’s clinical signs or are inconclusive, attempt urethral catheterization and perform a retrograde contrast study if necessary. Also, perform a rectal examination to palpate the urethra and rule out other concomitant disorders, such as prostatic disease or urethral neoplasia. When catheterizing a patient’s urethra, you may note a grating sensation as the catheter moves past small uroliths, or the uroliths may prevent catheter passage. Resistance to catheterization is normal at the base of the os penis and pelvic exure in male dogs. Successfully catheterizing a male cat typically requires sedation or anesthesia and appropriate extension of the penis away from the patient’s body (Figure 2). Occasionally, a urinary catheter may pass by uroliths without indicating their presence, especially when you use a relatively small diameter catheter. Ruling out urethroliths and, in some cases, urocystoliths may require performing retrograde cystography or urethrography. This imaging technique may also be indicated to help establish the exact location and approximate number of uroliths (Figure 3). 1A. A lateral abdominal radiograph of a dog examined for the primary complaints of hematuria and dysuria. No uroliths are observed in the urinary tract, including the portion of the urethra that can be seen on the ﬁlm. TREATMENT OVERVIEW If the patient is stable, take steps to determine the likely urolith composition and to develop a treatment plan. If the patient is relatively asymptomatic, monitoring the pet’s condition and establishing measures to prevent further urolith formation may be all that is needed. 1B. A lateral radiograph of the dog from Figure 1A showing the proper positioning of a patient to view the length of the urethra, including the perineal and penile urethra. Note the four radiopaque urethroliths proximal to the os penis (straight arrow). The identiﬁcation label on the ﬁlm (curved arrow) may be obscuring a portion of the urethra. Relieve urethral obstruction If the patient is not stable or has a complicating condition or a urethral obstruction, stabilize the patient and resolve the obstruction. Techniques for propulsing urethral uroliths or plugs (macroscopic aggregate of organic matrix and crystals) retrograde into the bladder or antegrade through the urethral ori ce are discussed in the boxed text titled “Antegrade and retrograde urethral urohydropropulsion in male dogs or cats” on page 548. If a urethral obstruction cannot be safely resolved in a timely manner, perform cystocentesis to decompress the bladder or place a cystostomy tube to allow a temporary outlet for urine until the obstruction can be eliminated. If the patient is at high risk for reobstruction, has had excessive trauma to the urethra in the process of relieving the obstruction, or has 2. Extending the penis and prepuce away from the body of a sedated or anesthetized cat will facilitate transurethral passage of a urinary catheter. VETERINARY MEDICINE October 2008 543

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Veterinary Medicine - October 2008 Contents Leading Off Clinical Exposures Idea Exchange Stalking Stones Vaginitis in Dogs CE Form Advertiser Index Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - October 2008

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