Evaluation of urine provides useful information that facilitates rapid diagnosis, treatment, and prevention of many urinary and nonurinary disorders. Results of urinalysis are particularly helpful in verifying or eliminating diagnostic possibilities formulated on the basis of observations from the history and physical examination. For example, consider a dehydrated 12-year-old miniature schnauzer being examined for persistent vomiting. Evaluation of urine specific gravity facilitates localizing the underlying cause. Negative fluid balance in a dog with primary gastrointestinal disease but adequate renal function would be expected to promote compensatory renal tubular reabsorption of water in excess of solute from glomerular filtrate (i.e., formation of urine with a specific gravity greater than 1.030). However, if an inappropriate degree of compensatory urine concentration is observed (urine specific gravity < 1.030), secondary gastrointestinal disorders (e.g., renal, hepatic, and adrenal diseases and certain toxicities) are far more likely to cause vomiting than primary gastrointestinal diseases (e.g., gastritis, pyloric obstruction) or pancreatitis.