Fluid therapy is the cornerstone of supportive care in veterinary medicine. In dogs and cats with preexisting confirmed or suspected pulmonary disease, concerns may exist that the fluid therapy may impair gas exchange, either through increases in hydrostatic pressures or extravasation. Colloidal therapy is more likely to magnify lung injury compared with isotonic crystalloids. Radiographic evidence of fluid overload is a late-stage finding, whereas point-of-care ultrasound may provide earlier information that can also be assessed periodically at the patient side. Cases should be evaluated individually, but generally a conservative fluid therapy plan is preferred with close monitoring of its tolerance.