somewhere in the neighborhood of 10-25% of people with CD have kidney issues related to their CD. Most often the kidney involvement is in the form of kidney stones. But there are other kidney issues that are seen in CD patients. They are quite rare. For example, from one of my sources I found this reference: "Hydronephrosis occurs in 3 to 6 percent of patients with Crohn's disease and may be due to ureteral obstruction as a result of intra-abdominal scarring.."
There are several places online to check the side effects of medications [medicinenet.com] and there are also places to check for interactions of medicines [www.drugdigest.org]. I don't believe that asacol or sulfasalazine are knwon to cause kidney problems other than discoloring the urine. However, I would closely read the side effect listings.
Moderator Crohn's Disease Forum
CD, Ankylosing Spondylitis, lupus, small fiber peripheral neuropathy, avascular necrosis, peripheral artery disease, degenerative disc disease, and a host of other medical problems.