Thanks for posting your query.
The discoloration on your back is not likely to be associated with any kidney problems.
The pain in the lower back is often found in people whose work involves physical effort. In some cases it can be due to weakness of muscles of the back. Regular exercise to strengthen the back muscles often help. It can be due to trauma too. In other cases it can be due to slipped disc
, any deformity
of spine , infection or growth. The discoloration sounds like collection of blood under skin from trauma which is gradually getting absorbed. It can also come from excessive use of heating pad
You can wait for 4-5 weeks for the discoloration to fade spontaneously and avoid applying any heat pads. In case the discoloration persists, then do consult a dermatologist
for proper diagnosis and prescription medicines.
I hope this answers your query.
In case you have additional questions or doubts, you can forward them to me, and I shall be glad to help you out.
Please accept my answer in case you do not have further queries.
Wishing you good health.
Dr. Praveen Tayal.