Acute kidney injury has been the most common presentation for canine leptospirosis in recent years. Affected dogs may present with lethargy, anorexia, vomiting, abdominal pain, and history of polyuria, oliguria, or anuria. Dogs that survive acute renal failure may return to baseline or progress to chronic kidney disease. Leptospirosis should also be considered in any dog with previously diagnosed chronic kidney disease that develops “acute-on-chronic” kidney injury. Renal tubular damage in leptospirosis may manifest as cylindruria, proteinuria, or glycosuria. In people, acute kidney injury due to leptospirosis is often nonoliguric and can be associated with hyponatremia and hypokalemia. These electrolyte changes have also been noted in canine leptospirosis, along with the expected changes of azotemia, hyperphosphatemia, and acidosis of renal failure. Hyperkalemia is also possible. Polyuria and polydipsia (PU/PD) in the absence of azotemia is a less common manifestation of the renal effects of leptospirosis. PU/PD may be due to a decrease in glomerular filtration rate that is sufficient to cause loss of renal concentrating ability without azotemia. However, PU/PD can also be due to nephrogenic diabetes insipidus