Or the official name for Crohn's patients with kidney stones, "extraintestinal complication".
These are probably the most commonly encountered kidney complications of IBD—particularly oxalate stones. Kidney stones are more common in Crohn's patients with disease of the small intestine than in the general population because of fat malabsorption. Fat binds to calcium, leaving oxalate (a type of salt) free to be absorbed and deposited in the kidney, where it can form into stones. The risk for developing kidney stones of this type is higher in people who have had a number of small bowel resections and are therefore more prone to dehydration. Their urine is more concentrated, a condition that is more likely to lead to stone formation. Symptoms may include sharp pain, nausea, vomiting, and blood in the urine. Kidney stone treatment calls for an increased fluid intake together with a low-oxalate diet (one that's rich in juices and vegetables).
I've had kidney stones several times in my long Crohn's career, some of the time resulting in surgery. My favorite was when they put a stent in. Putting it in wasn't the hard part (I was out), it was taking the damn thing out that was painful. Oh yea, did I mention I was awake for that and they use a local freezing gel?! Let me tell you, there was NO freezing happening down there!! I felt it all!!
Now a days, I'm pretty careful on drinking and eating too much dairy or calcium. I found out early that I cannot take calcium pills or supplements as they caused me to start having flank pain (kidney pain) in my back where it all starts.
After much research and trial and error, I discovered (for me anyway), that drinking raspberry tea as soon as I start feeling that "feeling" in my back made the pain go away. Just drinking it plain. No milk, no sugar, no nothing, just tea. Now I drink raspberry tea at least once a week to help out my kidneys and I haven't had a problem in years now. Ironically, raspberry tea contains calcium, obviously not enough to cause problems.