URINARY CALCULI ABSTRACT
Thanks to the Journal of the American Veterinary Medical Association for permission to reprint 2009;234:214 ABSTRACT
Composition and Characteristics of Urinary Calculi from Guinea Pigs
Michelle G. Hawkins, VMD, DABVP; Annette L. Ruby, BA; Tracy L. Drazenovich, DVM; Jodi L. Westropp, DVM, PHD, DACVIM
Objective—To determine the mineral composition of calculi, anatomic locations of the calculi, and findings of urinalysis and bacteriologic culture of urine and calculi in guinea pigs with urolithiasis.
Animals—127 guinea pigs.
Procedures—Records of urinary calculi that had been submitted to the University of California Stone Laboratory from 1985 through 2003 were reviewed. In addition, submissions of urinary calculi for evaluation by the laboratory were prospectively solicited from 2004 through 2007. Prospectively obtained calculi were accompanied by a urine sample for urinalysis and bacteriologic culture and a completed questionnaire. All calculi were analyzed by use of polarized light microscopy and infrared spectroscopy. A subset of calculi was examined by means of x-ray diffractometry (XRD).
Results—83% (43/52) of calculi from the laboratory database and 93% (70/75) of calculi that were prospectively solicited were composed of 100% calcium carbonate. Analysis via XRD confirmed that 5 of 6 calculi from a subset that had the greatest gross morphologic variation were composed of 100% calcite. Although many guinea pigs had received antimicrobials before bacteriologic cultures of urine were performed, Corynebacterium renale was isolated from 5 urine samples.
Conclusions and Clinical Relevance—Contrary to findings of other studies, urinary calculi analyzed for the present study were most commonly composed of 100% calcium carbonate, and infrared spectroscopy or XRD was necessary to differentiate this mineral from others. Treatments, including diet and husbandry practices, should be developed to help prevent development of calcium carbonate calculi in guinea pigs. (J Am Vet Med Assoc 2009;234:214–220)
* Wikipedia definition of corynebacterium renale referenced May 2010:
Corynebacterium renale is a pathogenic veterinary bacterium that causes cystitis and pyelonephritis in cattle.
C. renale is a facultatively anaerobic Gram positive organism, characterized by non-encapsulated, non-sporulated, immobile, straight or curved rods with a length of 1 to 8 µm and width of 0.3 to 0.8 µm, which form ramified aggregations in culture (looking like "Chinese characters").
The bacterium is sensitive to the majority of antibiotics, such as the penicillins, ampicillin, cephalosporins, quinolones, chloramphenicol, tetracyclines, cefuroxime and trimethoprim.
 "Bovine Cystitis and Pyelonephritis". The Merck Veterinary Manual. 2006.