thanks for your query
Skin pigmentation is common in patients with chronic renal diseases.
It is due to increased production of pigmentation hormones in such patients.
sometimes can cause increased pigmentation.
Now the treatment for the same is in the form of improvement of the renal parameters.
There is not much that can be done for the same.
Over the exposed sites, you can the a lightening agent like kojic acid
Use a sunscreen regularly.
Hope it helps
Dr Geetika Paul