RENAL STONE FORMATION IN PATIENTS WITH INFLAMMATORY BOWEL-DISEASE

Kidney stones are more common in patients with inflammatory bowel dise ase (IBD) than in the general population. The main lithogenetic risk f actors were evaluated in patients affected by Crohn's disease and ulce rative colitis. Our results show the presence of several factors, besi des hyperoxaluria, in patients with IBD although their behaviour appea rs different in Crohn's disease and ulcerative colitis at pre- and pos t-operative stages. Before surgery in patients with Crohn's disease we found a decreased citrate (p < 0.001) and magnesium (p < 0.005) excre tion together with a low urinary volume (p < 0.001) and pH (p < 0.005) . After surgery patients with Crohn's disease showed a further reducti on of magnesium and citrate. Patients with ulcerative colitis before s urgery showed a reduced citrate excretion (p < 0.05) and a more acidic pH (p < 0.05) than healthy subjects. Surgical treatment of proctocole ctomy with ileal pouch-anal anastomosis seems to increase the risk of stone formation; in fact, after surgery we observed a relevant decreas e of urinary volume (p < 0.001), pH (p < 0.0001) and urinary excretion of citrate (p < 0.0001) as well as magnesium (p < 0.005). Patients wi th IBD seem to be at greater risk of stone formation than patients wit h idiopathic calcium lithiasis; in fact, they show a lower excretion o f citrate (p < 0.001) and magnesium (p < 0.001) together with a low ur inary pH (p < 0.001) and volume (p < 0.001). Urinary volume reduction is probably one of the major risk factors together with the decrease o f small molecular weight inhibitors that is a constant finding in all patients with IBD.