Trends change in composition of feline uroliths - DVM
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Trends change in composition of feline uroliths

Problem list

Urocystoliths associated with inflammation of the lower urinary tract were identified on the basis of the history, physical examination and laboratory test results.

Initial diagnostic plans

To evaluate the entire urinary tract for evidence of uroliths and other possible causes of inflammation, survey abdominal radiography and double contrast cystography were planned.

Follow-up studies

Figure 1: Survey lateral abdominal radiograph of a 4.5 year-old spayed female domestic shorthair cat illustrating tow radiodense urocystoliths.
Survey radiographs of the abdomen revealed two elliptical, radiodense uroliths in the bladder lumen (Figure 1). Double contrast cystography revealed slight thickening of the bladder wall and irregularity of the bladder mucosa (Figure 2).

On the basis of available data, what is the probable mineral composition of the uroliths? The following observations were interpreted to indicate that the urocystoliths were composed of sterile struvite:

  • Radiographic density of the uroliths,
  • Struvite crystalluria,
  • Alkaline urine pH,
  • Negative in vitro culture of urine for aerobic bacteria.

Medical dissolution of uroliths

Figure 2: Lateral view of a double contrast cystogram illustrating the urocystoliths described in Figure 1.
How would you manage this patient if it were you, a family member or your cat? Would you recommend surgery, medical dissolution or a combination of the two? In a prospective clinical trial of medical dissolution of feline struvite urocystoliths in 20 cats performed at the Minnesota Urolith Center, consumption of a magnesium restricted diet designed to promote formation of acid urine (Prescription Diet Feline s/d; Hill's Pet Nutrition Inc.) resulted in dissolution of struvite uroliths in four to five weeks (JAVMA 196: 697-733, 1990). After informing the client of the benefits and risks associated with surgery and medical management, the client requested medical management.

Accordingly, the owners were instructed to feed the canned formulation of Feline s/d in sufficient quantity to maintain stable body weight. Plans were to continue this regimen of therapy for one additional "insurance month" following survey radiographic confirmation of urolith dissolution.

Figure 3: Survey lateral abdominal radio-graph of the cat described in Figure 1 obtained 13 days after initiation of management with a struvitolytic diet. The urocystoliths are about one-third their premanagement size.
The owner indicated that the clinical signs of hematuria and dysuria gradually subsided during a two-week period following initiation of dietary therapy. Thirteen days after initiation of therapy, physical examination revealed no abnormalities. Evaluation of a urine sample collected by cystocentesis revealed that the urine specific gravity was 1.026 and the pH was 6.5. Crystalluria was not observed. Although the urine was yellow in color, hematuria was detected by microscopic examination of urine sediment. These findings (acid urine pH, no struvite crystalluria, and reduction in specific gravity) indicate owner and patient compliance with dietary recommendations. Survey radiography revealed that the urocystoliths were approximately one-third their original size (Figure 3). The owners were shown the pre- and post-treatment radiographs to reinforce the need for continued therapy, and to praise them for compliance with management recommendations. They were advised to continue therapy with the calculolytic diet.


Source: DVM360 MAGAZINE,
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