Glucosuria
History. A client presents her 10-year-old female miniature schnauzer with the complaint of a dramatic increase in water consumption and urine volume over the previous 2 weeks.
Clinical Examination.
No major abnormalities are found on physical examination. The dog appears alert and is moderately overweight. The urinalysis reveals 4+ glucose (normally negative) and urine specific gravity of 1.030. The plasma glucose level is tested immediately and is 275 mg/dL (normal, 80-120 mg/dL).Comment. The dog has diabetes mellitus, which results from a relative or absolute deficiency of insulin secreted from the β cells of the pancreas. The insulin deficiency results in elevated plasma glucose levels. Cilucose is freely filtered by the glomerulus and normally is entirely reabsorbed by the proximal tubule. As the plasma glucose level rises, the glucose concentration in the glomerular filtrate rises, ∖∖rhen it exceeds the reabsorptive capacity of the proximal tubule (the renal threshold) of approximately 180 mg/dL, glucose appears in the urine (glucosuria). The glucose acts as an osmotic agent and increases the volume of urine excreted. The dog then drinks more waler to replace the excessive fluid loss.
Treatment. Treatment of diabetes mellitus in veterinary patients usually involves the administration of insulin injections two to three times each day, with adjustments of the dose in accordance with frequent evaluations of the plasma or urine glucose values. When the insulin dosage is appropriate, the plasma glucose level is normalized, the glucosuria disappears, and the urine volume and water consumption decrease.