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Urolithiasis This condition arises due to the deposit of minerals as stones or gravel (uroliths) in the urinary tract. The presence of these uroliths may go unnoticed, but those responsible for clinical signs should be removed. The minerals can be phosphate (struvite), cystine, urate, oxalate, or carbonate. The rate of formation depends on the conditions within the urinary tract and the concentration of mineral secreted in the urine. Alkaline urine speeds the formation of phosphate uroliths, acid urine predisposes to cystine uroliths. Most bitches suffer from phosphate, males tend to form cystine, oxalate, and urate uroliths. Certain animals, or breeds, have intrinsic defects in the kidneys which result in over excretion of minerals in the urine, for example urate stone formation in Dalmatians. In other breeds urate stones are usually a result of a concurrent liver disorder. Uroliths may be present in the bladder without causing clinical signs, they can be responsible for irritation of the bladder wall, or even acute obstruction of urine flow. Bitches usually present as a case of cystitis, urinating frequently and often containing blood. Males often present with complete or partial urinary obstruction. This will lead to bladder distension with the back pressure on the kidneys causing uraemia and vomiting. X-rays or catheterisation will reveal the position of the blockage. Contrast agents placed in the bladder will reveal those types of urolith which do not show on plain X-rays. Treatment with modification of the diet to dissolve the uroliths can be used in animals not in urgent need of surgical removal. Prescription diets are available which can change the urine pH and contain reduced levels of protein, calcium, magnesium and phosphorus. Antibiotics to control urinary infection should be administered. In cases of urinary obstruction immediate relief from pressure by catheterisation, surgical removal of uroliths, or draining the bladder with a needle and syringe must be carried out before acute renal failure develops. In males suffering from recurrent urinary obstruction an operation known as a permanent urethrostomy can be carried out to divert the urine away from the narrowest portion of the urethra which is most likely to block. The urethra will open instead in the perineal or pre-scrotal region. Prevention is through adjusting the acidity of the urine to prevent urolith formation, prompt treatment of any urinary infections, and increasing fluid intake and urine output to reduce the mineral concentrations in the urine. The use of prescription diets can help to achieve this. |
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