When tests have determined that a patient has excessive protein in their urine or impaired kidney functioning, a percutaneous kidney biopsy can help diagnose the problem. This procedure is performed in the hospital with the patient under sedation. Here, the physician extracts a small tissue sample from the patient’s kidney via a thin needle that is introduced through the skin on the back. With the assistance of ultrasound imaging, the specific location for the biopsy is identified and three or four tissue samples may be taken over the course of approximately one hour. Most patients can leave the hospital on the same day as their kidney biopsy procedure. In certain circumstances when a percutaneous biopsy is not recommended, an open biopsy may be performed. Here, the physician extracts a tissue sample from the kidney through a small incision while the patient is under general anesthesia. This more invasive method requires a hospital stay of at least 12 hours.