The incidence and prevalence of Inflammatory Bowel Disease (IBD) has increased over the past decades, imposing a growing socioeconomic burden on healthcare systems globally. Most of the morbidity and mortality related to IBD is typically attributed to gut inflammation and its complications; yet the disease is characterized by various extraintestinal manifestations that can be severe. Glomerulonephritis (GN) is of particular interest since a significant proportion of patients evolve into end-stage kidney disease, requiring kidney replacement therapy and associated with high morbidity and mortality. Herein, we review the GN landscape in IBD and define the clinical and pathogenic associations reported to date in the literature. Underlying pathogenic mechanisms suggest either the initiation of antigen-specific immune responses in the inflamed gut that cross react with non-intestinal sites, such as the glomerulus, or that extraintestinal manifestations are gut-independent events that occur due to an interaction between common genetic and environmental risk factors. We present data associating GN with IBD either as a bona fide extraintestinal manifestation or reporting it as an extraneous co-existing entity, involving various histological subtypes, such as focal segmental glomerulosclerosis, proliferative GN, minimal change disease, crescentic GN, but most emphatically IgA nephropathy. Supporting the pathogenic interplay between gut inflammation and intrinsic glomerular processes, enteric targeting the intestinal mucosa with budesonide reduced IgA nephropathy-mediated proteinuria. Elucidating the mechanisms at play would provide insight not only into IBD pathogenesis but also into the gut's role in the development of extraintestinal diseases, such as glomerular diseases.

Retinal drusen are deposits of inflammatory proteins that are found in macular degeneration and glomerulonephritis and result, in part, from complement activation. This was a cross-sectional observational study of individuals with inflammatory bowel disease (IBD) recruited from a Gastroenterology clinic who underwent non-mydriatic retinal photography. Deidentified images were examined for drusen, and drusen counts and size were compared with matched controls, and examined for clinical associations. The cohort with IBD comprised 19 individuals with ulcerative colitis, 41 with Crohn's disease and three with indeterminate colitis, including 34 males (54%) and an overall median age of 48 (IQR 23) years. Their median IBD duration was 7 (IQR 10) years, median CRP level was 7 (IQR 14) mg/L, and 28 (44%) had complications (fistula, stricture, bowel resection etc.), while 28 with Crohn's disease (68%) had colonic involvement. Drusen counts were higher in IBD than controls (12 ± 34, 3 ± 8 respectively, p = 0.04). Counts ≥ 10 were also more common (14, 22%, and 4, 6%, p = 0.02, OR 4.21, 95%CI 1.30 to 13.63), and associated with longer disease duration (p = 0.01, OR 1.06, 95%CI 1.00 to 1.13), an increased likelihood of complications (p = 0.003, OR 6.90, 95%CI 1.69 to 28.15) and higher CRP levels at recruitment (p = 0.008, OR1.02, 95%CI 1.00 to 1.05). Increased retinal drusen were found in all four individuals with Crohn's disease and IgA glomerulonephritis. IBD and drusen may share pathogenetic mechanisms and underlying risk factors such as complement activation.

Case reports suggest an association between inflammatory bowel disease, a chronic autoimmune condition linked to increased circulating IgA levels, and IgA nephropathy, the most common form of primary GN and a leading cause of ESKD.

In a Swedish population-based cohort study, we compared 3963 biopsy-verified IgA nephropathy patients with 19,978 matched controls between 1974 and 2011, following up participants until 2015. Inflammatory bowel disease data and ESKD status were obtained through national medical registers. We applied Cox regression to estimate hazard ratios (HRs) for future inflammatory bowel disease in IgA nephropathy and conditional logistic regression to assess risk of earlier inflammatory bowel disease in IgA nephropathy. We also explored whether inflammatory bowel disease affects development of ESKD in IgA nephropathy.

During a median follow-up of 12.6 years, 196 (4.95%) patients with IgA nephropathy and 330 (1.65%) matched controls developed inflammatory bowel disease (adjusted HR, 3.29; 95% confidence interval [95% CI], 2.73 to 3.96). Inflammatory bowel disease also was more common before a confirmed IgA nephropathy diagnosis. Some 103 (2.53%) IgA nephropathy patients had an earlier inflammatory bowel disease diagnosis compared with 220 (1.09%) controls (odds ratio [OR], 2.37; 95% CI, 1.87 to 3.01). Both logistic regression (OR, 2.60; 95% CI, 2.02 to 3.35) and time-varying Cox regression (HR, 1.84; 95% CI, 1.33 to 2.55) demonstrated that inflammatory bowel disease was associated with increased ESKD risk in patients with IgA nephropathy.

Patients with IgA nephropathy have an increased risk of inflammatory bowel disease both before and after their nephropathy diagnosis. In addition, among patients with IgA nephropathy, comorbid inflammatory bowel disease elevates the risk of progression to ESKD.

Little is known about clinical characteristics and kidney outcome in patients with biopsy-proven immunoglobulin A nephropathy (IgAN) in a context of inflammatory bowel disease (IBD).

We conducted a retrospective multicenter study with centralized histological review, to analyze the presentation, therapeutic management and outcome of 24 patients suffering from IBD associated IgAN relative to a cohort of 134 patients with primary IgAN without IBD.

Crohn's disease and ulcerative colitis accounted for 75% and 25% of IBD-associated IgAN cases, respectively. IBD was diagnosed before IgAN in 23 cases (a mean of 9 years previously) and was considered active at IgAN onset in 23.6% of patients. Hypertension was present in 41.7% of patients. Urinary protein-to-creatinine ratio exceeded 100 mg/mmol in 70.8% of patients (mean: 254 mg/mmol). Estimated glomerular filtration rate (eGFR) exceeded 60 ml/min/1.73m2 in 13/24 patients and only one patient required dialysis. In the Oxford MEST-C classification of renal biopsies, 57% were M1, 48% E1, 76% S1, 57% T1+T2 and 38% C1+C2. Steroids were administered in 50% of cases. After a mean follow-up of 7.2 years, four patients (16.7%) had a poor kidney outcome: end-stage renal disease (n = 3) or a > 50% decrease in eGFR from initial values (n = 1). A similar evolution was observed in patients with primitive IgAN.

This first case series suggests that IBD-associated IgAN have frequent inflammatory lesions at onset and variable long-term outcome.

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.

Kaposi's sarcoma (KS) is a vascular tumor arising in association with human herpesvirus-8 (HHV-8) infection, and different variants show different clinical presentations. Isolated intestinal KS in the background of Crohn's disease (CD) is exceedingly rare with only 3 cases reported in the English literature (from 1966 to 2016).

Herein, we report a case of intestinal KS in a 21-year-old HIV-negative Ethiopian male with a long-standing history of steroid therapy for his underlying IgA nephropathy. Recent gastrointestinal biopsies confirmed an additional diagnosis of CD. Despite the addition of Infliximab to his therapy, his CD remained refractory, and a laparoscopic-assisted ileocolectomy was performed to alleviate a partial small bowel obstruction. Examination of his terminal ileum demonstrated a polypoid mass with adjacent incidental ileal submucosal nodules. These nodules were composed of plump spindle cells with scattered mitoses and vascular channels with extravasated red blood cells. Intratumoral hyaline globules were also noted. Immunohistochemistry revealed HHV-8 positivity, confirming the histologic impression of KS.

Here we report the fourth case of KS in CD in an HIV-negative patient and only the third case of isolated intestinal KS in the setting of CD. A review of the literature suggests that attenuation of immunosuppressive therapy may be adequate management of iatrogenic KS in the absence of a systemic HHV-8 infection.

Kidney disease as a complication of inflammatory bowel disease (IBD), including Crohn disease (CD) and ulcerative colitis (UC), has been the subject of case reports. However, no cases series examining IBD and kidney disease has been published to date. This study aimed to evaluate a large series of kidney biopsy specimens from patients with IBD to better define the spectrum and relative frequencies of IBD-associated kidney pathology.

A retrospective review of native kidney biopsy specimens obtained from March 2001 to June 2012 identified 83 patients with IBD. Standard processing of all biopsy specimens included light microscopy, immunofluorescence, and electron microscopy.

There were 45 cases of CD and 38 cases of UC represented. The most common indication for kidney biopsy was acute or chronic kidney failure (63% [52 of 83]) and nephrotic-range proteinuria (16% [13 of 83]). IgA nephropathy was the most common diagnosis (24% [20 of 83]), followed by interstitial nephritis (19% [16 of 83]), arterionephrosclerosis (12% [10 of 83]), acute tubular injury (8% [7 of 83]), proliferative GN (7% [6 of 83]), and minimal-change disease (5% [4 of 83]). When compared, the frequency of IgA nephropathy in IBD was significantly higher than in all other native renal biopsy specimens from the same time period (24% [20 of 83] versus 8% [2734 of 33,630]; P<0.001). Of the 16 cases of interstitial nephritis, 9 (56%) had current or recent past exposure to aminosalicylates, including all cases of granulomatous interstitial nephritis.

IBD is associated with a spectrum of kidney diseases most commonly affecting the glomerular and tubulointerstitial compartments. IgA nephropathy is the most frequent kidney biopsy diagnosis in IBD and has a significantly higher diagnostic prevalence compared with all non-IBD kidney biopsy specimens. This may reflect a common pathogenic mechanism. Although many cases of tubulointerstitial nephritis are related to aminosalicylate exposure, the possibility of a direct relationship with IBD cannot be ruled out.

IgA nephropathy has been reported as a renal involvement in Crohn's disease. Crescentic IgA nephropathy, which accounts for fewer than 5% of cases of IgA nephropathy, has a poorer prognosis than other forms of crescentic glomerulonephritis. We recently experienced a case of rapidly progressive IgA nephropathy concurrent with exacerbation of Crohn's disease.

An 18-year-old male diagnosed with Crohn's disease underwent a hemicolectomy 2 years prior previously. He had maintained a state of Crohn's disease remission with 5-aminosalicylic acid treatment. Four months prior to referral to the nephrology clinic, he experienced non-bloody diarrhea. He simultaneously developed proteinuria and microscopic hematuria with deterioration of renal function. Based on renal biopsy findings, the patient was diagnosed with crescentic IgA nephropathy. Immunostaining for interleukin-17 in renal tissue and previous exacerbated colonic ulcers was positive. Steroid pulse therapy was administered, followed by high-dose glucocorticoid and oral cyclophosphamide therapy. The patient's renal function recovered and his gastrointestinal symptoms were alleviated.

We report a case of crescentic IgA nephropathy presenting with exacerbation of Crohn's disease, and present a review of the literature focusing on the pathophysiologic relationship between these two conditions.

Thin basement membrane nephropathy (TBMN) patients with additional inflammatory diseases and IgA nephropathy (IgAN) have not been reported before. It was unclear that if the prognosis of these patients is better or worse than patients with IgAN and TBMN, or IgAN patients with normal glomerular basement membrane (GBM).

We first reported five TBMN patients with additional inflammatory diseases and IgAN: three were with rheumatoid arthritis, and two had Crohn's disease. Clinical and laboratory features were analyzed between this group (group 3), IgAN patients with normal GBM (group 1), and patients with TBMN and IgAN (group 2).

Significant differences were observed in serum levels of IgG, IgA, and IgM between groups 1 and 3, p < 0.001, and between groups 2 and 3, p < 0.001. Glomerular filtration rate (GFR) in group 3 was significantly lower than that of groups 1 and 2, p < 0.01, respectively.

The prognosis of these patients is worse than patients with IgAN and TBMN or IgAN patients with normal GBM. Serum immunoglobulin levels and GFR in these patients were different from patients with IgAN and TBMN, or IgAN patients with normal GBM.

We describe herein a case of IgA nephropathy in a 34-year-old woman with Crohn's disease (CD) treated with infliximab. CD first appeared at the age of 15 years. An elemental diet was started for remission maintenance. Ten years later, the patient suffered from a recto-vaginal fistula and subtotal colectomy with stoma formation was performed. At the age of 33 years, the patient was investigated for painless macroscopic hematuria and proteinuria. Renal biopsy revealed IgA nephropathy. Mizoribine was started but proteinuria persisted. Due to diarrhea she was admitted to our hospital, and scheduled maintenance therapy with infliximab was initiated. After the first infliximab infusion, the patient presented significant clinical improvement in both diarrhea and proteinuria with concomitant decrease of C-reactive protein to normal levels and proteinuria ~1 g/day. This represents the first report of infliximab treatment in a patient with IgA nephropathy associated with CD and clarifies the importance of tumor necrosis factor-alpha (TNFα) in immunity to renal disease. Further studies are needed to draw firm conclusions for the safety of infliximab in patients with IgA nephropathy.

A number of case reports link the use of 5-aminosalicylic acid (5-ASA) to interstitial nephritis in patients with inflammatory bowel disease (IBD).

To investigate whether the long-term use of 5-ASA has harmful effects on renal function in patients with IBD.

A retrospective analysis of 171 consecutive outpatients with Crohn's disease or ulcerative colitis was conducted. Serum creatinine levels and body weight were measured before and after treatment to calculate the creatinine clearance (CrCl) rate.

In 171 patients (93 women, 78 men), the mean (+/- SD) dose of 5-ASA was 3.65+/-0.85 g/day with a cumulative dose of 11+/-7.7 kg over an interval of 8.4+/-5.9 years. Serum creatinine concentrations increased from 76.8 micromol/L to 88.7 micromol/L (n=171; P<0.0001) and the CrCl rate fell significantly from 104.6 mL/min to 93.1 mL/min (n=81; P<0.0001). There was one case of interstitial nephritis reported. Treatment groups included mesalamine (74.3%), sulfasalazine (15.2%) and combination (sulfalsalazine/mesalamine [10.5%]) with treatment durations of 7.2+/-4.5, 12.3+/-8.7 and 11.2+/-6.7 years, respectively. The duration of treatment was the most important covariate for change in CrCl and when analyzed by treatment group, those treated with sulfasazine had a strong correlation (r=-0.54, P=0.0145), while nonsignificant in the mesalamine group (r=0.06, P=0.7017). The decline in CrCl was negatively correlated with the pretreatment CrCl rate (r=-0.34; P=0.0024) and positively correlated with the mean daily dose of 5-ASA (r=0.32; P=0.0034).

The present study is the first to demonstrate a significant dose- and treatment duration-dependant decline in CrCl. The risks need to be further evaluated because 5-ASA is widely used for long-term maintenance therapy in patients with IBD.

IgA-nephropathy is the most common primary chronic glomerulonephritis worldwide. Beside the primary IgA-nephropathy (IgA-nephropathy with an unknown origin), there are more and more cases, which are associated with diseases of other organs. Although the causality is often not obvious, these forms are called secondary IgA-nephropathy. In this study, the authors cover only the secondary forms of IgA-nephropathy with relation to gastroenterology in a broader sense that includes the liver. They would like to draw the attention to the necessity of analyzing also the associate occurrence of gastrointestinal diseases (principally liver diseases, coeliac disease, Crohn's disease, ulcerative colitis) in patients with IgA-nephropathy, as well. They think that it would be expedient to organize a nationwide clinical analysis that would search the frequency of occurrence of IgA-nephropathy in the above mentioned gastrointestinal diseases.

Ulcerative colitis is rarely associated with immunoglobulin A nephropathy (IgAN). The development of IgA nephropathy complicates further the clinical course of patients with ulcerative colitis. A 72-year old man with a 30-year history of ulcerative colitis requiring colectomy and modest renal insufficiency secondary to complications of nephrolithiasis and renal artery stenosis developed glomerular hematuria, proteinuria and progressive renal failure. Percutaneous kidney biopsy revealed IgAN with extensive glomerular and interstitial sclerotic changes. After resection of a chronically infected ileo-rectal pouch, renal function improved, while hematuria and proteinuria gradually disappeared without specific treatment of the IgAN. The manifestations of IgAN complicating ulcerative colitis can be improved with effective treatment of the bowel disease even when there are extensive sclerotic changes in the kidneys.

A case of glomerulonephritis in a 35-year-old man with Crohn's disease is described here. The patient presented with severe diarrhea, nephrotic range proteinuria, hematuria, microangiopathic hemolytic anemia, thrombocytopenia, hypocomplementemia, acute renal failure requiring hemodialysis, cryoglobulinemia, and extensive thrombotic gangrene of the distal upper and lower limbs. The patient did not respond to plasmapheresis and steroid therapy and died of upper gastrointestinal bleeding. Renal tissue obtained at autopsy showed IgA-mediated antiglomerular basement membrane crescentic glomerulonephritis. Linear staining of the glomerular basement membrane by non-IgG antibodies is quite unusual with only 11 cases previously reported in the worldwide literature, 8 caused by IgA. Glomerulonephritis is a rarely reported extraintestinal manifestation of inflammatory bowel disease, and there are only 24 previously described cases that are reviewed and summarized in this report. Glomerulonephritis occurred in the setting of active bowel inflammation in all cases, circulating immune complexes were found in nearly half the cases, and serum complements usually were normal. Renal insufficiency and nephrotic range proteinuria were typically present at the time of diagnosis of glomerulonephritis and most often improved in parallel with treatment of the gastrointestinal disorder. The histologic findings were varied and included membranoproliferative glomerulonephritis, mesangioproliferative glomerulonephritis, membranous nephropathy, IgA nephropathy, and IgM nephropathy. Thus, the authors present the first case of glomerulonephritis caused by antiglomerular basement membrane disease in association with inflammatory bowel disease.

Mesalamines are slow-release formulations of 5-aminosalicylic acid (5-ASA) and are effective as primary treatment and maintenance therapy in inflammatory bowel disease. Interstitial nephritis is a recognized side effect. We report two cases of biopsy-confirmed interstitial nephritis in patients being treated with 5-ASA. Both had a trial of steroid therapy. One patient had partial recovery of renal function but the other patient was in chronic renal failure and likely was approaching the need for dialysis. Interstitial nephritis is an under-recognized complication of 5-ASA therapy. Early identification and withdrawal of this drug can lead to a partial or complete reversal of renal dysfunction.

Renal and urologic complications are not uncommon in patients with inflammatory bowel disease, and can be directly or indirectly related to the underlying disease process or its treatment. Many of these patients have asymptomatic disease, or the urinary symptoms are nonspecific or overshadowed by bowel symptoms. By the time a urinary complication is considered, significant disease progression or renal damage may have occurred. These risks necessitate a high degree of diligence and periodic urologic evaluation as part of the long-term management of patients with inflammatory bowel disease.

Renal disease is an unfrequent extraintestinal manifestation of chronic inflammatory bowel disease.

A 12-year-old girl suffered from recurrent abdominal pain, diarrhea and growth impairment due to Crohn's disease of ileocaecal region. After six months of nutritional rehabilitation, an ileo-caecal resection was performed because of intestinal stenosis. The surgical procedure was followed by parietal abcess and cutaneous fistula. One year later, a purulent secretion came out of the fistula associated with fever, hematuria and acute renal failure. Renal biopsy confirmed IgA nephropathy. The course was favorable under parenteral nutrition and after surgical closure of the sigmoido-cutaneous fistula. The microscopic hematuria only persisted but the nephropathy did not relapse even during a further digestive exacerbation.

IgA nephropathy has been reported in association with chronic inflammatory bowel disease. Its mechanism remains unclear: increased mucosal IgA production in inflammatory bowel, increased serum IgA and/or immune complex deposition in the renal mesangium appear the most relevant hypotheses.