HI, thanks for using healthcare magic The kidneys are located to the back, this is the reason that when testing for kidney related pain, doctors usually palpate the back. Kidney disease does not cause constipation but it is possible that if the kidneys are very really not working well, itching can occur. The constipation would be due changes in the bowel/intestines. Itching can also be due to liver disease, allergies, infection or side effect of medication. Oral antihistamines and topical steroids can help with the itching, these would be over the counter. Blood tests should be done to check for liver function and infection, also to check for allergies as well. I hope this helps