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Trends in Feline Urolith Composition
PA G E 6
A D VA N C E S
uroliths include urate (sodium or ammonium salt), xanthine, apatite, brushite, silica, dried solidified blood (DSB), cystine, potassium magnesium pyrophosphate, and newberyite.
Objectives To evaluate trends in uroliths composition in cats.
Procedure Submission forms to a urinary stone reference laboratory were reviewed and included 5,230 uroliths presented over 20 years. Each cat’s age, sex, breed, and stone location were recorded.
Results
TRENDS IN FELINE UROLITH COMPOSITION Background Urolithiasis causes clinical signs of the lower urinary tract in 15% to 21% of affected cats. Uroliths in the upper portion of the urinary tract can cause ureteral obstruction, acute renal failure, and death. Treatment of feline uroliths usually involves surgical removal or medical dissolution, voiding urohydropropulsion, or lithotripsy. In a recent Canadian study, the most common minerals contained in uroliths from cats were struvite and calcium oxalate. Calcium oxalate also is currently the most common component in calculi from the upper portion of the urinary tract in cats. Other possible components of feline
The stones contained struvite, calcium oxalate, urates, DSB, apatite, brushite, cystine, silica, potassium magnesium pyrophosphate, xanthine, and newberyite. Struvite and calcium oxalate were the most commonly detected minerals. During the past 20 years, the ratio of calcium oxalate stones to struvite stones had increased significantly. However, during the last 3 years of the study, the percentage of struvite stones (44%) was higher than the percentage of calcium oxalate stones (40%). Both types were usually found in the urinary bladder. During the last 20 years, the number of calcium oxalate-containing calculi in the upper portion of the urinary tract increased significantly. The number of apatite uroliths declined significantly, and DSB stone numbers increased significantly, compared with all other stone types. There was no significant difference in the number of urate stones.
Author Conclusion The increasing proportion of calcium oxalate uroliths in the last 20 years could be a result of alterations in commercial cat diets. However, the decreased percentage of calcium oxalate calculi and increased percentage of struvite calculi observed in the last 3 years may indicate a more recent trend in the frequency of these uroliths.
Inclusions Eight figures, 2 tables, 34 references.
Editor Annotation In 1993, the frequency of calcium oxalate and struvite calculi in cats was equal. A
A D VA N C E S
substantial increase in calcium oxalate uroliths continued thereafter. This is attributed by most authorities to overzealous use of acidifying and potentially magnesiumrestricted diets. A recent emerging trend revealed that 44% of feline uroliths are now struvite, while 40% are calcium oxalate. There was a prediction for Himalayan and Persian cats to form struvite or calcium oxalate uroliths, and males were overrepresented with regard to calcium oxalate. There was a significant decrease in apatite calculi, which is most likely secondary to acidifying diets. There was an increase in DSB containing uroliths. There was no significant change in the occurrence of urate stones (9% per year), and most do not have portosystemic shunts based on normal serum bile acid concentration. Other calculi (cystine, newberyite, xanthine, silica, brushite, or potassium magnesium pyrophosphate) could not be assessed for a meaningful change in incidence because of small numbers analyzed. (MM) Cannon AB, Westropp JL, Ruby AL, et al. Evaluation of trends in urolith composition in cats; 5,230 cases (1985-2004). J Am Vet Med Assoc 2007;231:570-576.
PAG E 7
A D VA N C E S
uroliths include urate (sodium or ammonium salt), xanthine, apatite, brushite, silica, dried solidified blood (DSB), cystine, potassium magnesium pyrophosphate, and newberyite.
Objectives To evaluate trends in uroliths composition in cats.
Procedure Submission forms to a urinary stone reference laboratory were reviewed and included 5,230 uroliths presented over 20 years. Each cat’s age, sex, breed, and stone location were recorded.
Results
TRENDS IN FELINE UROLITH COMPOSITION Background Urolithiasis causes clinical signs of the lower urinary tract in 15% to 21% of affected cats. Uroliths in the upper portion of the urinary tract can cause ureteral obstruction, acute renal failure, and death. Treatment of feline uroliths usually involves surgical removal or medical dissolution, voiding urohydropropulsion, or lithotripsy. In a recent Canadian study, the most common minerals contained in uroliths from cats were struvite and calcium oxalate. Calcium oxalate also is currently the most common component in calculi from the upper portion of the urinary tract in cats. Other possible components of feline
The stones contained struvite, calcium oxalate, urates, DSB, apatite, brushite, cystine, silica, potassium magnesium pyrophosphate, xanthine, and newberyite. Struvite and calcium oxalate were the most commonly detected minerals. During the past 20 years, the ratio of calcium oxalate stones to struvite stones had increased significantly. However, during the last 3 years of the study, the percentage of struvite stones (44%) was higher than the percentage of calcium oxalate stones (40%). Both types were usually found in the urinary bladder. During the last 20 years, the number of calcium oxalate-containing calculi in the upper portion of the urinary tract increased significantly. The number of apatite uroliths declined significantly, and DSB stone numbers increased significantly, compared with all other stone types. There was no significant difference in the number of urate stones.
Author Conclusion The increasing proportion of calcium oxalate uroliths in the last 20 years could be a result of alterations in commercial cat diets. However, the decreased percentage of calcium oxalate calculi and increased percentage of struvite calculi observed in the last 3 years may indicate a more recent trend in the frequency of these uroliths.
Inclusions Eight figures, 2 tables, 34 references.
Editor Annotation In 1993, the frequency of calcium oxalate and struvite calculi in cats was equal. A
A D VA N C E S
substantial increase in calcium oxalate uroliths continued thereafter. This is attributed by most authorities to overzealous use of acidifying and potentially magnesiumrestricted diets. A recent emerging trend revealed that 44% of feline uroliths are now struvite, while 40% are calcium oxalate. There was a prediction for Himalayan and Persian cats to form struvite or calcium oxalate uroliths, and males were overrepresented with regard to calcium oxalate. There was a significant decrease in apatite calculi, which is most likely secondary to acidifying diets. There was an increase in DSB containing uroliths. There was no significant change in the occurrence of urate stones (9% per year), and most do not have portosystemic shunts based on normal serum bile acid concentration. Other calculi (cystine, newberyite, xanthine, silica, brushite, or potassium magnesium pyrophosphate) could not be assessed for a meaningful change in incidence because of small numbers analyzed. (MM) Cannon AB, Westropp JL, Ruby AL, et al. Evaluation of trends in urolith composition in cats; 5,230 cases (1985-2004). J Am Vet Med Assoc 2007;231:570-576.
PAG E 7