In Crohn's, the lining of the gut can also lead to kidney stone development
Another factor to consider is the intestinal permeability of the GI tract. Intestinal permeability refers to the lining of the GI tract, which helps control what material can travel in and out of the intestines, stomach, etc. through the gut wall. When the gut wall becomes more permeable (material passes through more easily), oxalate flows through the GI tract and can form stones.
A common result of Crohn’s is malabsorption of dietary intake. This is due to inflamed and dysfunctioning mucous membranes and also diarrhea. In turn, this can potentially lead to overly-high absorption of nutrients, which causes passive diffusion of oxalate. When paired with the formation of calcium-fatty acid salts due to the dysfunctioning mucous membranes, these two factors can lead to serious formation of kidney stones.
All this to say, avoid foods and other substances that irritated the gut wall. Many people who have Crohn’s partake in a gluten-free diet, whether they have low-tolerance for gluten or are Celiac. Likewise, if certain substances are prone to cause diarrhea for you, avoid those.