Best Noninvasive Predictor of Renal Function in Assessing Adult Sickle Nephropathy

Background: Sickle cell disease is a common inherited blood disorder. Kidney disease is a major cause of problems in people with sickle cell disease. In order to identify kidney problems early and stop the progression of kidney disease, doctors need the most accurate tests to check kidney function. Researchers hope to understand more about how to test for kidney disease in people with sickle cell disease. Objective: To determine which of two different lab tests is the best to measure kidney function in adults with sickle cell disease. Eligibility: People 18 years and older who have sickle cell disease Design: Participants will be screened with a medical history and blood tests. Participants will have up to 3 visits. Participants will collect their urine in a special container over 24 hours. At the first visit, participants will have blood tests. They will bring their container of urine to the visit. They will have an iothalamate test. For the test, they will get a catheter: a small tube will be inserted into a vein. A special contract agent will be injected into the vein. Blood will be collected over the next 4 hours to test kidney function. Participants will return the next day for a second visit. They will have blood tests. They will have an MRI. For the MRI, they will like on a table that slides into a machine that takes pictures of the kidneys. They may have the MRI in a third visit. ...