Renal amyloidosis as a late complication of Crohn's disease: a case report and review of the literature from Japan

Insights into renal and urological complications of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic condition characterized by immune-mediated inflammation in the gastrointestinal tract, which follows a relapsing and remitting course. Apart from affecting the gastrointestinal tract, IBD also has extra-intestinal manifestations (EIMs). While the etiology of extraintestinal manifestation remains unclear, it is theorized to be based on immunological responses influenced by genetic factors. Renal involvement is one of the EIMs observed in ulcerative colitis and Crohn's disease. The renal manifestations in IBD patients encompass a range of conditions including nephrolithiasis, amyloidosis, tubulointerstitial nephritis, glomerulonephritis (GN), obstructive pathologies, and chronic kidney disease (CKD). The incidence of CKD in IBD patients varies from 5%-15%. The decline in renal function can stem from various factors such as direct inflammatory damage to the kidneys leading to glomerular or tubular injury, or from complications like recurrent stones, amyloidosis, or GN. Additionally, nephrotoxic medications used in treating IBD, such as TNF-α inhibitors, calcineurin inhibitors, and aminosalicylates, can exacerbate the decline in renal function. Currently, there is a lack of consensus regarding these patients' screening and renal function monitoring. This review aims to assess the existing literature on the different renal complications among individuals with IBD, shedding light on their pathophysiology and management.

Renal Manifestations of Inflammatory Bowel Disease

Renal and urinary involvement has been reported to occur in 4% to 23% of inflammatory bowel disease (IBD) patients. Parenchymal renal disease is rare and most commonly affects glomerular and tubulointerstitial compartments. The most common findings on renal biopsy of IBD patients are IgA nephropathy and tubulointerstitial nephritis. Overall morbidity of IBD-related renal manifestations is significant, and there is often only a short window of injury reversibility. This, along with subtle clinical presentation, requires a high index of suspicion and routine monitoring of renal function. There are no established guidelines for the optimal screening and monitoring of renal function in IBD patients.

Renal Involvement in Inflammatory Bowel Diseases

The prevalence of extraintestinal manifestations in inflammatory bowel diseases varies from 6% to 46%. The aetiology of extraintestinal manifestations remains unclear. There are theories based on an immunological response influenced by genetic factors. Extraintestinal manifestations can involve almost every organ system. They may originate from the same pathophysiological mechanism of intestinal disease, or as secondary complications of inflammatory bowel diseases, or autoimmune diseases susceptibility. The most frequently involved organs are the joints, skin, eyes, liver and biliary tract. Renal involvement has been considered as an extraintestinal manifestation and has been described in both Crohn's disease and ulcerative colitis. The most frequent renal involvements in patients with inflammatory bowel disease are nephrolithiasis, tubulointerstitial nephritis, glomerulonephritis and amyloidosis. The aim of this review is to evaluate and report the most important data in the literature on renal involvement in patients with inflammatory bowel disease. Bibliographical searches were performed of the MEDLINE electronic database from January 1998 to January 2015 with the following key words (all fields): (inflammatory bowel disease OR Crohn's disease OR ulcerative colitis) AND (kidney OR renal OR nephrotoxicity OR renal function OR kidney disease OR renal disease OR glomerulonephritis OR interstitial nephritis OR amyloidosis OR kidney failure OR renal failure) AND (5-aminosalicylic acid OR aminosalicylate OR mesalazine OR TNF-α inhibitors OR cyclosporine OR azathioprine OR drugs OR pediatric).

Renal manifestations and complications of inflammatory bowel disease

Renal manifestations and complications are not rare in patients with inflammatory bowel disease (IBD) and may present as nephrolithiasis, amyloidosis, tubulointerstitial nephritis, and glomerulonephritis. Symptoms of renal impairment are not always specific and since the underlying bowel disease is preponderant, renal function deterioration may be underestimated. Additionally, medical treatment of patients with IBD such as aminosalicylates, cyclosporine, and tumor necrosis factor-α inhibitors can cause renal complications, although direct correlation to bowel disease is not always clear. The well-documented renal manifestations and complications of IBD, as well as the possible renal side effects of new drugs, emphasize the need for periodic evaluation of renal function. New markers of renal function may facilitate early diagnosis and unravel the complex mechanisms responsible for kidney damage. The purpose of this review is to summarize the renal manifestations and complications as well as the markers of renal function utilized in IBD, attempting to shed more light on the pathophysiology of renal damage in IBD.