Dog Urinary Calculi
The formation of calculi, or urinary stones, in the kidney is rare in small animals, but their occurrence in 
the bladder and urethra is common, especially in the dog.
Calculi vary in size, shape, and composition. In size they range from that of a grain of sand to that of a pea or larger. In shape they may be round and smooth or rough and irregular. They may consist of more or less hard concretions of salts, such as phosphates, oxalates, or orates, or of soft, waxy formations of nitrogenous material, when they are known as cosine stones.
The formation of the concretions (calculi) in the bladder may bedew to a general systemic disturbance, to local inflammatory diseases of the urinary tract which produce an excess of salts in the urine, or to food or water rich in salts of various kinds.
The symptoms produced by bladder stones depend to some extent on their type, number, and size. Large, hard calculi produce the most pronounced symptoms. Urination may be difficult, and there may be small amounts of blood in the urine after severe straining, and constant dribbling of urine. Pus may also appear in the urine, there may be tenderness and pain in the region of the bladder, and the animal may move stiffly and stand with an arched back. In severe cases, general depression with loss of appetite and symptoms of uremic poisoning (chills, trembling, extreme weakness, and stupor) may develop.
Calculi in the urethra result from the stones that are formed in the bladder and lodge in the urethra. They are more common in the male than in the female dog. Affected animals make frequent attempts to urinate; there is evidence of pain and sometimes complete stoppage of urine, with a greatly distended bladder. Symptoms of calculi in the bladder may also be evident silver nitrate.