I am unable to make a specific diagnosis based on the information that you present. A drop in the estimated glomerular filtration rate (eGFR) from 68 milliliters per minute per 1.73 meters squared to 53 would be a significant drop. The 24 hour urine collection that you mention, if done carefully and properly should be more accurate. I do suggest that you also have urine testing for blood, protein and infection in order to complete the screening for chronic kidney disease (CKD). I would also suggest repeating the blood test to check for laboratory inconsistency as a cause of the sudden fall in the eGFR.