Kidney volume belongs to roughly equal, and the difference will not be very big. If it appears that one side of the kidney is obviously large and one side is small, further detailed examination is needed to clarify whether the disease is present. The usual possible causes: 1. Kidney atrophy, such as the appearance of unilateral kidney atrophy, there will be a smaller kidney volume. Atrophy is commonly caused by trauma, infection, vascular inflammatory atrophy, such as vascular, thrombosis, etc. 2, renal tumor, the kidney volume on the side of the tumor appears to be larger than that on the normal side, and is accompanied by obvious unsmooth renal envelope, protruding outward, with nodular masses, etc. Patients may also have symptoms of lumbar pain and hematuria, which require further enhancement of CT and other examinations. 3. hydronephrosis, the volume of the kidney on the hydronephrosis side is also larger than that on the normal side. It is often accompanied by obstructive factors such as stones or ureters. CT or ultrasound of the whole urinary tract is needed to check and rule out.