Pet guinea pigs frequently have uroliths, and the calculi can be found in the kidney, ureters, bladder, or urethra. Clinical signs depend on the location and size of the stones. Hematuria and stranguria are common if the stones are in the lower urinary tract. Stones in the ureters are very painful, and the patient may present with inappetence and decreased activity. If the calculi are large enough, they may be palpated, but diagnosis is based on radiographic findings. Since the stones typically comprise calcium salts (calcium oxalate or calcium phosphate), they are usually readily visible on radiographs. Normal guinea pig urine is alkaline (pH >8.5) and contains calcium crystals. The exact etiopathogenesis of calculi is unknown, but diet probably plays a role. Stones are surgically removed, but the recurrence rate is high. Reducing calcium in the diet by limiting intake of alfalfa hay may be helpful. Avoiding foods with high oxalic acid content, such as spinach, parsley, and vitamin C, is helpful. While all guinea pigs need vitamin C, if the amount is limited to 25 to 100 mg/day significant hyperoxaluria is unlikely to occur. Potassium citrate has also been used by the author after stone removal.
COMMENTARY: Making sure the guinea pig has plenty of fresh water may also help reduce the risk for recurrence. Until the etiopathogenesis of these stones in guinea pigs is better understood, they will continue to recur at high rates.
Guinea pig urolithiasis. Hoefer HL. EXOTIC DVM 6.2:23-25, 2004.