Kidney failure, also referred to as end-stage renal disease, is a medical condition that is characterized by loss of kidney functions. One of the confirmatory tests for kidney failure is serum creatinine. Creatinine is produced by muscles, and it is filtered through the kidneys and excreted in urine. Since creatinine gets completely filtered and minimally reabsorbed, it is a good indicator of the filtration ability of the kidney. The higher the creatinine in blood, the lower the ability of the kidney to filter the blood, which indicates kidney failure. Biopsy is a test that involves extraction of a tissue for analysis in order to determine the extent or cause of the condition. It is usually indicated as a test for malignancy. Ultrasound scan is a test using sound waves with higher frequencies, typically for medical imaging for masses or cysts. Blood urea nitrogen is a test that checks the urea nitrogen in the blood indicated to evaluate both liver and kidney functions, it is not as specific for kidney diseases as creatinine.