One cause of renal cortex thinning may be nephron loss due to chronic renal disease, according to Sharing in Health. Another possible cause is reflux nephropathy, a condition caused by renal atrophy resulting from infected or sterile urine, as noted by the University of Virginia School of Medicine.
Chronic kidney disease, as opposed to acute kidney injury, is often responsible for a thinned cortex in addition to small, shrunken kidneys, commonly under 10 centimeters long, explains The Merck Manual. End-stage renal disease makes specific diagnosis difficult, but the best tool for diagnosis is a renal biopsy whenever possible. Unfortunately, if after testing the kidneys are found to be fibrotic, a renal biopsy is not advisable, says Merck.
Ultimately, there are several conditions that might cause renal cortex thinning, but as Dr. Michael Lioudis of Cleveland Clinic notes, cortical thinning is simply a change in the overall proper functioning of the kidneys, and a doctor must be consulted to figure out the underlying cause.
Dr. Lioudis goes on to say that to obtain an accurate diagnosis a doctor must order a complete medical workup, including a list of herbal and over-the-counter medications taken, a detailed medical history, and lab tests such as blood draws and a urinalysis.