Causes of swelling in patients with kidney diseases can be various. 1. Very high protein is passing in urine, which can lead to low albumin in blood, subsequently causing swelling in the legs. 2. Very poor function of kidneys, which can be judged by serum creatinine report. 3. Poor pumping capacity of the heart. 4. Some drugs. First step: Decide the severity of edema which can be judged by direct examination of the patient by doctor. Second step is to get serum creatinine, albumin, and urine protein creatinine ratio (UPCR) investigations to decide whether it is due to kidney disease, heart disease, or something else.