Renal and urological complications are relatively frequent extraintestinal complications of Crohn’s disease and ulcerative colitis. With regard to their site and the mechanism of their development they are divided into three groups. Indirect complications caused by metabolic consequences or immune mechanisms include urolithiasis, renal amyloidosis and glomerulonep- hritis. Direct complications which develop as a result of the spread of the aggressive disease beyond the gastrointestinal tract into neighbouring tissues and structures include acalculous hydronephrosis, fistulae communicating with the ureter or urinary bladder, in exceptional cases with the urethra, and perinephritic abscesses. The third group is formed by iatrogenically condi- tioned damage of the kidneys (medicamentous treatment), of the urinary bladder, ureter or sexu- al functions (surgery). As to the incidence the most serious complication of idiopathic intestinal complications is urolithiasis. Contrary to the general population, in 80 % oxalate concrements are found and much less frequently urate concrements. In the pathogenesis of the development of oxalate lithiasis malabsorption of bile acids and fats participates as well as impaired permeability of the mucosa of the large intestine.

        Key words: Crohn’s disease – ulcerative colitis – urolithiasis – nephrotoxicity