NAFLD sensitizes the liver to injury and increases the risk of developing acute or chronic liver failure following another liver injury.Other rare hepatobiliary manifestations of Crohns disease include: cholangiocarcinoma, granulomatous hepatitis, cholelithiasis, autoimmune hepatitis, hepatic abscess, and pericholangitis.Renal and Urological
Nephrolithiasis, obstructive uropathy, and fistulization of the urinary tract directly result from the underlying disease process. Nephrolithiasis is due to calcium oxalate or uric acid stones. Calcium oxalate is due to hyperoxaluria typically associated with either distal ileal CD or ileal resection. Oxalate absorption increases in the presence of unabsorbed fatty acids in the colon. The fatty acids compete with oxalate to bind calcium, displacing the oxalate, which can then be absorbed as unbound sodium oxalate across colonocytes and excreted into the urine. Because sodium oxalate only is absorbed in the colon, calcium-oxalate stones form only in patients with an intact colon. Patients with an ileostomy are prone to formation of uric-acid stones because of frequent dehydration. The sudden onset of severe abdominal, back, or flank pain in patients with IBD, particularly if different from the usual discomfort, should lead to inclusion of a renal stone in the differential diagnosis.Urological manifestations in patients with IBD may include ureteral calculi, enterovesical fistula, perivesical infection, perinephric abscess, and obstructive uropathy with hydronephrosis. Ureteral compression is associated with retroperitoneal extension of the phlegmonous inflammatory process involving the terminal ileum and cecum, and may result in hydronephrosis severe enough to cause hypertension.Immune complex glomerulonephritis presenting with proteinuria and hematuria has been described in children and adults with CD or UC.
Crohns is associated with an increased intake of animal protein, milk protein, and an increased ratio of omega-6 to omega-3 polyunsaturated fatty acids. Those who consume vegetable proteins appear to have a lower incidence of Crohns disease. Consumption of fish protein has no association.Smoking increases the risk of the return of active disease (flares). The introduction of hormonal contraception in the United States in the 1960s is associated with a dramatic increase in incidence, and one hypothesis is that these drugs work on the digestive system in ways similar to smoking. Isotretinoin is associated with Crohns.Although stress is sometimes claimed to exacerbate Crohns disease, there is no concrete evidence to support such claim. Dietary microparticles, such as those found in toothpaste, have been studied as they produce effects on immunity, but they were not consumed in greater amounts in patients with Crohns. The use of doxycycline has also been associated with increased risk of developing inflammatory bowel diseases. In one large retrospective study, patients who were prescribed doxycycline for their acne had a 2.25-fold greater risk of developing Crohns disease. Pathophysiology
During a colonoscopy, biopsies of the colon are often taken to confirm the diagnosis. Certain characteristic features of the pathology seen point toward Crohns disease; it shows a transmural pattern of inflammation, meaning the inflammation may span the entire depth of the intestinal wall. Ulceration is an outcome seen in highly active disease. There is usually an abrupt transition between unaffected tissue and the ulcer—a characteristic sign known as skip lesions.