Kidney tumors are often difficult to diagnose. Usually, a parent notices a lump or mass in the abdominal area while dressing or bathing a child who has no other symptoms. By this time, the tumor is generally very large. Sometimes the tumor is found during routine doctor visits when the pediatrician palpates the toddler’s abdomen. Kidney tumors are occasionally diagnosed when the child is evaluated for other unrelated reasons, such as accidental trauma to the abdominal area.

Some children with kidney tumors have abdominal pain, and up to 25 percent have blood in the urine. Blood may be visible to the naked eye or it may only be seen with a microscope. About 25 percent of children have high blood pressure at diagnosis.

Other signs and symptoms of kidney tumors include fever, diarrhea, weight loss, shortness of breath, urogenital infections, and anemia (low number of red blood cells). The child may feel tired and unwell.