Renal dysplasia in dogs is a developmental abnormality of one or both kidneys that is present when a puppy is born. It is characterized by small, misshapen kidneys that don’t mature normally. The causes of renal dysplasia aren’t well-understood. It may be caused by bacterial or viral infection of fetal tissues; canine herpesvirus is one potential contributor. Alternatively, it may happen because the mother is exposed to toxins while she’s pregnant, or because the fetus is physically traumatized. Genetics almost certainly play a significant role. Some dogs with renal dysplasia never act sick. When symptoms do occur, they usually aren’t very specific and may include urinary abnormalities, failure to have normal heat cycles, appetite and weight loss, stunted growth, pale mucous membranes, dull dry hair coat, poor body condition, weakness, lethargy, depression, vomiting, diarrhea, oral ulcers, bad breath and pain. When an owner notices several of these symptoms, they should seek veterinary advice.