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Gut and Liver is an international journal of gastroenterology, focusing on the gastrointestinal tract, liver, biliary tree, pancreas, motility, and neurogastroenterology. Gut atnd Liver delivers up-to-date, authoritative papers on both clinical and research-based topics in gastroenterology. The Journal publishes original articles, case reports, brief communications, letters to the editor and invited review articles in the field of gastroenterology. The Journal is operated by internationally renowned editorial boards and designed to provide a global opportunity to promote academic developments in the field of gastroenterology and hepatology. +MORE
Yong Chan Lee |
Professor of Medicine Director, Gastrointestinal Research Laboratory Veterans Affairs Medical Center, Univ. California San Francisco San Francisco, USA |
Jong Pil Im | Seoul National University College of Medicine, Seoul, Korea |
Robert S. Bresalier | University of Texas M. D. Anderson Cancer Center, Houston, USA |
Steven H. Itzkowitz | Mount Sinai Medical Center, NY, USA |
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Carolina Palmela1, Farhad Peerani2, Daniel Castaneda3, Joana Torres4, Steven H. Itzkowitz4
Correspondence to: Steven H. Itzkowitz, Division of Gastroenterology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1069, New York, NY 10029-6574, USA, Tel: +1-212-241-8788, Fax: +1-646-537-8647, E-mail: steven.itzkowitz@mountsinai.org
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Gut Liver 2018;12(1):17-29. https://doi.org/10.5009/gnl16510
Published online April 6, 2017, Published date January 15, 2018
Copyright © Gut and Liver.
Primary sclerosing cholangitis (PSC) is a chronic, progressive cholestatic disease that is associated with inflammatory bowel disease (IBD) in approximately 70% of cases. Although the pathogenesis is still unknown for both diseases, there is increasing evidence to indicate that they share a common underlying predisposition. Herein, we review the epidemiology, diagnosis, disease pathogenesis, and specific clinical features of the PSC-IBD phenotype. Patients with PSC-IBD have a distinct IBD phenotype with an increased incidence of pancolitis, backwash ileitis, and rectal sparing. Despite often having extensive colonic involvement, these patients present with mild intestinal symptoms or are even asymptomatic, which can delay the diagnosis of IBD. Although the IBD phenotype has been well characterized in PSC patients, the natural history and disease behavior of PSC in PSC-IBD patients is less well defined. There is conflicting evidence regarding the course of IBD in PSC-IBD patients who receive liver transplantation and their risk of recurrent PSC. IBD may also be associated with an increased risk of cholangiocarcinoma in PSC patients. Overall, the PSC-IBD population has an increased risk of developing colorectal neoplasia compared to the conventional IBD population. Lifelong annual surveillance colonoscopy is currently recommended.
Keywords: Inflammatory bowel disease, Cholangitis, sclerosing, Diagnosis, Liver transplantation, Colorectal neoplasms
Inflammatory bowel disease (IBD) is a chronic idiopathic inflammatory disease of the gastrointestinal tract. Up to 50% of patients may develop extraintestinal manifestations (EIM) during their disease course.1 One such EIM is primary sclerosing cholangitis (PSC), described for the first time in 1965.2 PSC is a chronic and progressive cholestatic disease, characterized by inflammation and fibrosis of the intrahepatic and/or extrahepatic ducts,3 that may result in liver cirrhosis and eventually end-stage liver disease.3 Orthotopic liver transplantation (OLT) is the only potentially curative therapy for PSC, with survival rates of 85% and 70% at 5 and 10 years, respectively.3 Without OLT, half of symptomatic patients die within 12 to 15 years.
In Western countries, the reported incidence of PSC is 0.07 to 1.3 per 105/yr, and the prevalence is 8.5 to 13.6 per 105.4,5 About 70% of patients with PSC have underlying IBD, most frequently ulcerative colitis (UC) in over 75% of cases.6 The prevalence of IBD in PSC patients ranges from 50% to 99% across different studies.6 Several factors could explain this large variation. In a recent systematic review, the studies that used both endoscopic and histological criteria for IBD diagnosis, showed a higher median percentage of IBD among PSC patients.6 Geographic differences could also contribute to this variation. Asian studies report a lower prevalence of IBD in PSC patients in comparison to European and American populations.7,8 However, in some of these studies, IBD diagnosis was established or excluded based on registry data or notes in medical files without reviewing original endoscopy or histology. In fact, a recent Japanese report by Sano
Although there may be a possible common pathogenesis between PSC and IBD, the two disorders can occur at different times. PSC may be diagnosed many years after proctocolectomy for colitis, and conversely IBD can appear many years after the initial diagnosis of PSC or even after OLT altogether.10 In most reports, IBD diagnosis precedes that of PSC.11,12 In a recent report, Sinakos
PSC is likely to have an underlying multifactorial etiology, with a predominant immune-mediated process.3 PSC and IBD are interrelated conditions that may well share an underlying predisposition (Fig. 1). Both diseases share common antibodies, such as those directed against cytoplasmic and nuclear antigens of neutrophils with a characteristic perinuclear staining pattern (p-ANCA). p-ANCA antibodies have been found in 26% to 85% of PSC patients and in up to 68% of patients with UC.3
From a genetic standpoint there is increasing evidence that PSC is distinct from UC and CD. Large-scale genome-wide association studies (GWAS) have identified close to 200 independent loci associated with IBD.16,17 Most of these loci are shared between UC and CD.16 GWAS studies in PSC have identified a total of 16 PSC susceptibility loci.18 In the most recent genetic analysis there was surprisingly limited overlap between PSC and IBD loci.19 Half of the PSC loci failed to show a robust association with IBD, suggesting overlapping yet distinct genetic mechanisms.19 Genetic predisposition to autoimmune bile duct injury triggered by toxic or infectious agents that may gain access through the diseased colon is potentially a major mechanism leading to PSC in IBD patients.
Two hypotheses that link PSC and IBD include the “gut lymphocyte homing” hypothesis and the “leaky gut” hypothesis.20 Activated lymphocytes from the inflamed and permeable gut may enter the enterohepatic circulation and persist as memory cells that cause hepatic inflammation.21,22 Some molecular features, such as chemokines and adhesion molecules, are shared by the liver and intestine and could contribute to lymphocyte binding at both sites.21 T cells activated in the gut during active IBD could differentiate into effector cells with the ability to bind to both hepatic and mucosal endothelium. The activation and expansion of these memory cells in the liver could eventually lead to the induction of MAdCAM-1 and CCL25 in the liver, promoting the recruitment of CCR9+ α4β7+ mucosal T cells and the development of inflammation.23 Findings such as PSC development after colectomy for IBD, or the development of IBD after OLT for PSC, have led some investigators to suggest that aberrant homing of lymphocytes between the intestine and liver could be involved in the pathogenesis of the PSC-IBD phenotype.21
The “leaky gut” hypothesis refers to the association between progressive hepatic and biliary injury and increased intestinal permeability and translocation of bacterial metabolites from the gut.24 The liver receives approximately 75% of its blood supply from the splanchnic circulation and is constantly exposed to both beneficial and noxious molecules from the intestinal microbiome.25 This so-called “gut-liver axis” is essential for the maintenance of health but may also play an important role in pathogenesis of liver and intestinal diseases.25,26 In IBD there is a known intestinal microbiome dysbiosis, characterized by lower biodiversity and decreased bacteria of the
The interaction between microbiota and bile acid (BA) metabolism may also play an important role in the PSC-IBD phenotype. Recent evidence supports the existence of BA dysmetabolism in IBD patients due to impaired microbiota enzymatic activity.27 One of the contributing factors for the difference in phenotype between PSC-IBD patients and IBD controls may be altered concentration and/or composition of colonic BA impacting on gut microbiota and stool BA metabolism.
In summary, PSC-IBD pathogenesis is still unclear but this phenotype is likely to have an underlying multifactorial etiology, influenced by genetic predisposition, immune-mediated processes and altered gut microbiota (Fig. 1).
Patients with the PSC-IBD phenotype have demographic features resembling PSC cases, although the PSC diagnosis tends to occur at a younger age, when compared with PSC-only controls (mean age, 33.6±17.2 years vs 58.9±18.2 years; p<0.001).9 The incidence is higher in males and is more prevalent in young and middle-aged patients.13–15 The age at clinical onset of IBD is controversial. Some reports indicate that the mean age for IBD diagnosis is higher among PSC-IBD patients compared with IBD controls,15 but a recent study reported that PSC-UC patients had a UC diagnosis at a significantly earlier age compared with UC controls (mean age, 24.5 years vs 33.8 years).31
As stated above, the co-occurrence of PSC with IBD is associated with a distinct IBD phenotype (Fig. 2). PSC-IBD patients typically have mild intestinal disease activity and an increased incidence of extensive colitis and pancolitis, rectal sparing and backwash ileitis (Table 1).9,10,12,13,15,31–38 Extensive colonic involvement, irrespective of the IBD subtype (i.e., CD vs UC), is the primary IBD phenotype associated with PSC. From a population-based cohort of 579 PSC patients in the Netherlands, pancolitis was observed in 94% of PSC-UC patients and in 96% of PSC-CD patients.37 Though rare, some patients with ulcerative proctitis and Crohn’s ileitis have concomitant PSC.37,39 Although pancolitis is a characteristic finding of PSC-IBD patients, it occurs at variable rates (35% to 95% of patients).6 Some cases are endoscopically diagnosed as right-sided IBD.11 In a recent systematic review, the majority of studies addressing disease activity found that the prevalence of inflammation was highest in the right colon and lowest toward the distal colon.6,9,12 This pattern of inflammation was significantly different from matched non-PSC IBD-controls.6,9,12
The frequency of rectal sparing and backwash ileitis in PSC-UC patients differs among reports. A recent systematic review reported an incidence of rectal sparing from 6% to 66% (versus 2% to 25% in IBD without PSC) and of backwash ileitis between 5% and 46% (compared to 3% to 24% in UC without PSC).6 It is worth noting that since PSC-IBD patients typically have quiescent disease, microscopic inflammation may still be present in spite of an endoscopically normal-appearing rectum.12 The frequency of rectal sparing and backwash ileitis should be investigated in future studies using a consensus definition.
In PSC-CD patients, the anatomic location of the disease differs from patients with isolated CD. Colonic involvement is the most often reported (37% to 82%), followed by ileocolic involvement (22% to 58%), and rarely isolated ileal involvement (2% to 5%).6 In PSC-CD patients there is a lower frequency of stricturing and penetrating disease compared to patients with isolated CD.6,39
Despite the higher prevalence of pancolitis, the intestinal inflammation in PSC-IBD patients is usually quiescent leading to mild symptoms, reduced use of steroids and decreased rates of hospitalization.9,10 On histological grounds, the colonic inflammation is also very mild, with only focal basal plasmacytosis and occasional mild cryptitis.10 Schaeffer
There is conflicting evidence regarding the course of IBD after OLT for PSC. Several reports demonstrated worsening colitis activity following OLT in approximately 30% of PSC-IBD patients.3 Furthermore, de-novo IBD after OLT has also been reported and it may develop in 14% to 30% of PSC patients up to 10 years after transplantation.40 Retrospective studies comparing IBD activity before and after liver transplantation found that endoscopic colonic inflammation was more frequent after OLT, as was the rate of relapse and overall clinical IBD activity.41,42 A retrospective study of 31 patients with PSC-UC who received OLT, showed that the Mayo score was higher after transplantation compared with the pre-transplant score (mean score, 2.91±0.9 vs 6.64±3.7; p=0.009).38 The above findings have led to the speculation that the diseased PSC liver somehow keeps colonic inflammation in check. Several factors may be associated with a worse course of IBD after OLT such as a new balance in the immune system favoring an immune-mediated attack against the colonic mucosa, the presence of active IBD at the time of transplantation, discontinuation of 5-aminosalicylates, infrequent use of azathioprine and the use of tacrolimus.35,42 Haagsma
Of note, the worsening of IBD after OLT has not been universally confirmed. Jorgensen
PSC-IBD patients who undergo proctocolectomy with ileal pouch anal anastomosis (IPAA) have a higher risk of developing pouchitis, which affects 13.8% to 90% of cases (versus 33% in patients with conventional IBD).6,13,15 Nonetheless, the long-term outcomes are often satisfactory,45 with the incidence of pouch failure in PSC-IBD patients subjected to IPAA being similar to IBD-only patients.6 Mathis
While PSC is often associated with a distinctive IBD phenotype,35 the effect of IBD on the natural history and disease behavior of PSC is less well defined. In PSC patients with concomitant IBD, the PSC phenotype may differ when compared to PSC patients without IBD. Combined intrahepatic and extrahepatic biliary involvement has been described to be more common in PSC-IBD patients compared to PSC patients alone (81.5% vs 46.2%, p<0.05),46 but has not always been described in the literature. At least two other retrospective reviews have refuted the finding of a higher prevalence of intra- and extra-hepatic biliary involvement in patients with coexisting IBD.47,48
Long-term PSC outcomes also do not seem to be associated with the presence or disease severity of IBD. In a natural history study of 305 Swedish PSC patients, associated IBD had no prognostic significance on the need for OLT or liver-related deaths.49 Similarly, transplant-free survival rates, cirrhosis rates, and mortality of PSC patients were found to be independent of concomitant IBD in a retrospective Israeli study of 141 PSC patients.48 Navaneethan
In contrast to the majority of findings reported in the aforementioned studies, some of the PSC-IBD literature suggests that the rapidity of PSC disease progression may be contingent upon the specific IBD phenotype. A retrospective case-controlled study utilizing the Oxford PSC and IBD databases revealed that major event-free survival (cancer, OLT or death) was prolonged in the PSC-CD group compared to the PSC-UC group (Cox regression, p=0.04).39 The authors postulate that this may be explained by the increased prevalence of small-duct PSC in PSC-CD patients compared to PSC-UC patients, which was also suggested by Rasmussen
PSC recurrence (rPSC) after OLT occurs in 30% to 50% of patients, usually 10 years posttransplantation.54 Akin to the data available regarding the relationship between IBD and PSC disease progression, the presence of concomitant IBD in PSC patients has not been unanimously identified as a risk factor for rPSC. In a systematic review of autoimmune liver diseases after transplantation, there was no statistically significant difference in the rate of rPSC in patients with and without IBD.55 In another retrospective analysis of 31 PSC patients who underwent OLT, 5-year survival rates, infectious complications, frequency of rejection and need for re-transplantation did not differ based on whether patients had coexisting IBD.56 Moreover, a retrospective analysis of 105 PSC patients who underwent OLT revealed no correlation between rPSC and IBD activity.57 On the contrary however, in another study PSC patients with UC had significantly more rPSC compared to PSC patients without UC.58 Several publications have described that an intact colon is a strong predictor of rPSC and that colectomy potentially has a protective effect against rPSC. In a cohort of 230 PSC patients who underwent OLT, colectomy pre- and peri-OLT conferred a protective effect against rPSC in the transplanted graft.59 Moreover, an intact colon prior to OLT was the strongest predictor of rPSC. Joshi
Despite opposing evidence on the association of IBD with rPSC, data supports that PSC-IBD patients are at risk for a greater number of acute cellular rejection (ACR) episodes post-OLT.62,63 In a retrospective chart review of 55 PSC patients who underwent OLT, the incidence of acute rejection was higher in PSC-IBD patients compared to PSC patients (27/31 vs 10/24, p=0.0006).64 Moreover, PSC-IBD patients who were diagnosed with IBD at a younger age were more likely to develop severe acute rejection. In spite of the increased incidence of ACR in this study, 5-year survival rates and rPSC post-OLT did not vary based on the presence of concomitant IBD.
Since its initial description by Broome
The mechanisms underlying the increased risk of CRN in PSC-IBD patients remain unknown. Different authors proposed a variety of mechanisms that may be partially responsible for this outcome (summarized in Table 3), though these are still not conclusive. In rat models, BA have been found to have a carcinogenic potential94,95 (specifically secondary BA, like deoxycholic acid).96 A different stool BA abundance and/or composition could potentially be involved in the right-sided CRN risk observed in PSC-IBD,97,98 although this has never been demonstrated. Whether the specific dysbiosis that has been described in PSC-IBD could be involved in this risk remains unknown.99–102 Other mechanisms described include inactivation of the Farnesoid X receptor pathway,87,103,104 shown to be involved in hepatic and colonic inflammation and CRC, and polymorphisms in two genes in the chromosome 6p21. A more comprehensive understanding of the PSC pathogenesis and the involved BA dysmetabolism and microbiota dysbiosis will probably help to clarify the mechanisms involved in the increased CRN risk in these patients.
One would hypothesize that once indefinite or low-grade dysplasia (LGD) is diagnosed in PSC-IBD, the rate of progression to high-grade dysplasia or CRC would be faster than in IBD patients. However, while some studies have described the rate of progression of indefinite and LGD in IBD-only patients, the rate of progression of CRN in patients with PSC-IBD has not been thoroughly studied. In a small study with 10 patients, one-third of the patients progressed from LGD to advanced neoplasia over a mean follow-up of 13±11 months, suggesting a faster rate of progression as compared to what has been described in IBD alone.105
Since many patients with PSC require OLT,106 some uncertainty exists regarding the effect of the strong immunosuppressive agents in the post-OLT setting, leading to an increased risk for CRN versus the “protective” effect of curing the PSC on the risk of CRN. Some of the initial studies107,108 showed that there was no difference in the rate of CRN in the post-OLT PSC-IBD group compared to post-OLT non-IBD/PSC and nontransplanted PSC-IBD patients. More recent studies have suggested that there may be even a 4-fold greater risk of CRN, though there was no evidence of any relevant impact on mortality.109,110 Particularly, one study suggested that patients who developed LGD after OLT had a slower rate of progression and were less likely to have progressive neoplasia or persistent LGD.111
Another subset of the PSC-IBD population who are at risk for neoplasia are the patients who have undergone an IPAA, given that their increased incidence of pouchitis theoretically leads to severe mucosal atrophy and subsequent pouch malignancy.112 Although a small study showed an increased risk of ileal pouch dysplasia in PSC-IBD compared to non-IBD and non-PSC populations separately,113 a larger study that included 65 patients suggested a low risk of 5.6% in 5-year for pouch or cuff dysplasia (95% CI, 1.8% to 16.1%).114 Particularly, CRC has been documented but is extremely uncommon after IPAA.115 There are no specific surveillance guidelines for post-IPAA PSC-IBD patients, so most experts prefer annual pouchoscopies as standard care for PSC patients, even though the risk seems to be low.
Given that the risks of CRN have been widely described in the PSC-IBD population, the different gastroenterology societies have commented on recommendations for surveillance in this group. Current recommendations support the use of annual colonoscopy and biopsies in PSC-IBD patients from the time of PSC diagnosis, without taking into account the duration of IBD since it is often not known.116,117 No specific recommendations on the management and follow-up of indefinite or LGD exist for this high-risk population that may be more prone to be referred for colectomy, given the elevated risk of CRC. Hence, further studies are needed to better determine the outcomes regarding low-grade and indefinite dysplasia in PSC-IBD patients.
UDCA118 has been in the past considered an option in the prevention of CRN in PSC-IBD patients. However, studies have shown mixed results: some of them with decreased risk of CRN,119,120 others not showing any effect in the incidence of neoplasia,89,121,122 and others even showing an increased risk with high-dose UDCA, usually in the first 6 years after the medication was started.123 A meta-analysis in 2013, evaluating eight studies with 763 PSC-IBD patients, concluded that there is a preventive effect for the development of advanced CRN when taking UDCA (OR, 0.35; 95% CI, 0.17 to 0.73), with a more pronounced effect with the 8 to 15 mg/kg/day dose (OR, 0.19; 95% CI, 0.08 to 0.49).124 Therefore, while there might be a protective effect, more studies are needed to draw more definitive conclusions.
In a recent large retrospective review of 399 PSC-IBD patients from the Mayo Clinic, a prolonged duration of IBD was associated with an increased risk of cholangiocarcinoma (CCA) in PSC patients.125 This increased risk equated to a 33% increased risk per 10 years of IBD and the risk was not modified by colectomy. Furthermore, in the subset of PSC-IBD patients requiring colectomy, patients who underwent surgery due to colonic neoplasia or dysplasia as opposed to refractory disease were also at a significantly higher risk of CCA. From an earlier published study conducted at Mayo Clinic, although IBD was not associated with CCA risk, proctocolectomy was a significant risk factor on univariate analysis for the development of CCA in PSC patients (relative risk, 4.43).126 It is unclear if the observed elevated cancer risk may be secondary to the effect of immunosuppression or the severity of intestinal inflammation.
The increased predisposition to malignant transformation may not only apply to the biliary system in PSC-IBD patients. From a population-based study in New Zealand, 14 of 60 PSC-IBD patients developed a malignant complication including CRC, hepatocellular carcinoma or CCA whereas none of the 19 PSC patients without IBD did.51 Nevertheless, in another study of 66 PSC patients, the prevalence of malignant complications was not dependent on the presence or absence of IBD,46 nor did it play a role in a natural history study of 305 Swedish PSC patients49 or a long-term single-center study of 200 PSC patients.127
IBD affects about 70% of patients with PSC. Although there is likely an underlying shared predisposition for PSC and IBD, the pathogenesis of these interrelated conditions is still unknown. These diseases are likely to be influenced by genetic predisposition, immune-mediated processes and altered gut microbiota. Clinically, PSC-IBD patients demonstrate a right-to-left gradient of colonic inflammation as well as an increased incidence of extensive colitis, rectal sparing and backwash ileitis. Despite the higher prevalence of pancolitis, the intestinal inflammation is usually quiescent leading to mild symptoms, reduced use of steroids and decreased rates of hospitalization. Nevertheless, post-IPAA, the rates of pouchitis in PSC-UC patients are higher compared to non-PSC UC patients. While PSC is associated with a distinct IBD phenotype, the effect of IBD on the natural history and disease behavior of PSC, including recurrent PSC post-OLT, is less well defined. Overall, the PSC-IBD population has an increased risk of developing CRN and CRC compared to the IBD-only population. Moreover, IBD may also be also associated with an increased risk of CCA in PSC patients.
In summary, PSC-IBD is a puzzling disease with a very special phenotype (Fig. 2); a better understanding of the mechanisms underlying the cross talk between the liver and the gut is needed and could lead to the development of new strategies.
S.H.I. was funded in part by a grant from The Chemotherapy Foundation. F.P. would like to acknowledge the Canadian Institutes of Health Research and the Canadian Association of Gastroenterology for supporting his advanced inflammatory bowel disease fellowship and research.
GWAS, genome-wide association studies.
Studies Evaluating IBD Extension, Backwash Ileitis, and Spared Rectum in PSC-IBD Patients Compared to IBD-Only Controls
Study | Year | No. of patients | IBD extension (proctitis/left-sided/pancolitis) % | Backwash ileitis % | Rectal sparing % | ||||
---|---|---|---|---|---|---|---|---|---|
PSC-IBD | IBD | PSC-IBD | IBD | PSC-IBD | IBD | PSC-IBD | IBD | ||
Olsson | 1991 | 55 | 1,445 | 5.5/NA/94.5 | 38.2/NA/61.8 | NA | NA | NA | NA |
Loftus | 2005 | 71 | 142 | NA/NA/87 | NA/NA/54 | 51 | 7 | 52 | 6 |
Sokol | 2008 | 75 | 150 | NA | NA | 18.7 | 24 | 20 | 13.3 |
Joo | 2009 | 40 | 40 | 0/7.5/85 | 0/35/45 | 10 | 7.5 | 27.5 | 25 |
Sano | 2011 | 20 | 60 | 5/5/35 | 30/31.7/35 | NA | NA | NA | NA |
Ye | 2011 | 21 | 63 | NA/NA/95.2 | NA/NA/55.6 | 42.9 | 3.2 | 38.1 | 1.6 |
Marelli | 2011 | 96 | 0 | 0/10/90 | NA | NA | NA | NA | NA |
Jorgensen | 2012 | 110 | 0 | NA/3/55 | NA | 20 | NA | 65 | NA |
O’Toole | 2012 | 103 | 2,649 | 1/22.3/54.4 | 7.9/24.5/25 | NA | NA | NA | NA |
Boonstra | 2012 | 80 | 80 | 2.5/2.5/65 | 5/20/43.8 | 5 | 2.5 | 10 | 1.3 |
Gelley | 2012 | 20 | 0 | 15/15/55 | NA | NA | NA | NA | NA |
Schaeffer | 2013 | 97 | 0 | 0/17.5/43.4 | NA | NA | NA | NA | NA |
Sinakos | 2013 | 129 | 0 | NA/12.4/58.9 | NA | 11.6 | NA | 24 | NA |
Studies Evaluating the Risk of Colorectal Neoplasia in PSC-IBD Patients
Study | Year | Type of study | No. of patients | Outcome |
---|---|---|---|---|
Broome | 1992 | Prospective | 72 UC patients followed to see presence of CRN | 28% of patients with CRN and/or DNA aneuploidy had IBD and PSC, which was statistically significant (p=0.0004). |
Broome | 1995 | Prospective | 40 Patients with PSC-UC vs 2 groups of 40 UC-only patients | Risk of CRN in PSC-UC was 9%, 31%, and 50% after 10, 20, and 25 years of disease, compared to 2%, 5%, and 10% in UC-only patients (p<0.001). |
Brentnall | 1996 | Prospective | 20 Patients with PSC-UC vs 25 UC-only patients | Colonic neoplasia was present in 45% of PSC-UC patients, vs 16% in UC-only (p=0.002). |
Leidenius | 1997 | Retrospective | 48 Patients with PSC-UC vs 45 UC-only patients | CRN presented in 29% of PSC-UC patients, vs 9% in UC-only (p<0.05). |
Marchesa | 1997 | Retrospective | 27 Patients with PSC-UC vs 1,185 UC-only patients | Colonic neoplasia was present in 59.5% of PSC-UC patients vs 11.5% in UC-only patients (RR, 6.9; 95% CI, 3.0–16.0). |
Shetty | 1999 | Prospective | 132 Patients with PSC-UC vs 196 UC-only patients | CRN presented in 25% of PSC-UC patients, vs 5.6% in UC-only (adjusted RR, 3.15; 95% CI, 1.37–7.27; p<0.001). |
Jess | 2007 | Retrospective | 43 Patients with CRN, vs 102 control patients | PSC was associated with a higher risk of developing CRN (OR, 6.9; 95% CI, 1.2–40). |
Terg | 2008 | Prospective | 1,333 Patients with UC-39 had PSC, which were matched to two control patients | CRC presented in 18% of PSC-UC patients, vs 2.6% in matched UC-only patients (p=0.006). Risk of CRC in PSC-UC was 11% and 18% after 10 and 20 years vs 2% and 7% in UC-only, respectively (p=0.002). |
Sokol | 2008 | Prospective | 75 Patients with PSC-IBD vs 152 IBD-only patients | 25 Years cumulative risk of CRN was 23.4% in PSC-IBD vs 0% in IBD-only (p=0.002). PSC was a risk factor for CRC (OR, 10.8; 95% CI, 3.7–31.3). |
Lindstrom | 2011 | Prospective | 28 Patients with PSC-CD vs 46 CD-only patients | CRN presented in 32% of PSC-CD patients, vs 7% in CD-only (OR, 6.78; 95% CI, 1.65–27.9; p=0.016). |
Ananthakrishnan | 2014 | Retrospective | 224 Patients with PSC-IBD, from a pool of 5,506 CD and 5,522 UC patients | PSC-IBD had a higher risk of CRC (OR, 5.00; 95% CI, 2.80–8.95) and digestive tract cancer (OR, 10.4; 95% CI, 6.86–15.76), compared to IBD-only patients. |
Navaneethan | 2016 | Retrospective | 223 Patients with PSC-UC vs 50 with PSC-CD | PSC-UC patients had higher risk for colonic neoplasia compared to PSC-CD (35.9% vs 18%, p=0.009). |
Proposed Mechanisms for the Increased Risk of Colorectal Neoplasia in PSC-IBD Patients
Mechanism | Explanation |
---|---|
Genetic | Polymorphisms present in TNFα promoter and specific genome associations in proximity to HLA complex on chromosome 6p21 have been associated with a higher likelihood of developing CRN. |
Bile acid | Cholestasis favors decreased intestinal BA reabsorption. Microbiota convert primary BA to secondary BA, which have a carcinogenic potential. |
FXR pathway | FX secretion by the intestine is induced by the presence of BA. Normally, FX leads to a decrease in the production of BA by the liver. |
Microbiome | Gut bacteria are presumed to act on altered BA composition resulting in proinflammatory and procarcinogenic compounds. |
Gut and Liver 2018; 12(1): 17-29
Published online January 15, 2018 https://doi.org/10.5009/gnl16510
Copyright © Gut and Liver.
Carolina Palmela1, Farhad Peerani2, Daniel Castaneda3, Joana Torres4, Steven H. Itzkowitz4
1Division of Gastroenterology, Surgical Department, Hospital Beatriz Ângelo, Loures, Portugal, 2Division of Gastroenterology, Department of Medicine, University of Alberta, Edmonton, AB, Canada, 3Division of Internal Medicine, Mount Sinai St. Luke’s and Mount Sinai West Hospitals, Mount Sinai, New York, NY, USA, 4Division of Gastroenterology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
Correspondence to: Steven H. Itzkowitz, Division of Gastroenterology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1069, New York, NY 10029-6574, USA, Tel: +1-212-241-8788, Fax: +1-646-537-8647, E-mail: steven.itzkowitz@mountsinai.org
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Primary sclerosing cholangitis (PSC) is a chronic, progressive cholestatic disease that is associated with inflammatory bowel disease (IBD) in approximately 70% of cases. Although the pathogenesis is still unknown for both diseases, there is increasing evidence to indicate that they share a common underlying predisposition. Herein, we review the epidemiology, diagnosis, disease pathogenesis, and specific clinical features of the PSC-IBD phenotype. Patients with PSC-IBD have a distinct IBD phenotype with an increased incidence of pancolitis, backwash ileitis, and rectal sparing. Despite often having extensive colonic involvement, these patients present with mild intestinal symptoms or are even asymptomatic, which can delay the diagnosis of IBD. Although the IBD phenotype has been well characterized in PSC patients, the natural history and disease behavior of PSC in PSC-IBD patients is less well defined. There is conflicting evidence regarding the course of IBD in PSC-IBD patients who receive liver transplantation and their risk of recurrent PSC. IBD may also be associated with an increased risk of cholangiocarcinoma in PSC patients. Overall, the PSC-IBD population has an increased risk of developing colorectal neoplasia compared to the conventional IBD population. Lifelong annual surveillance colonoscopy is currently recommended.
Keywords: Inflammatory bowel disease, Cholangitis, sclerosing, Diagnosis, Liver transplantation, Colorectal neoplasms
Inflammatory bowel disease (IBD) is a chronic idiopathic inflammatory disease of the gastrointestinal tract. Up to 50% of patients may develop extraintestinal manifestations (EIM) during their disease course.1 One such EIM is primary sclerosing cholangitis (PSC), described for the first time in 1965.2 PSC is a chronic and progressive cholestatic disease, characterized by inflammation and fibrosis of the intrahepatic and/or extrahepatic ducts,3 that may result in liver cirrhosis and eventually end-stage liver disease.3 Orthotopic liver transplantation (OLT) is the only potentially curative therapy for PSC, with survival rates of 85% and 70% at 5 and 10 years, respectively.3 Without OLT, half of symptomatic patients die within 12 to 15 years.
In Western countries, the reported incidence of PSC is 0.07 to 1.3 per 105/yr, and the prevalence is 8.5 to 13.6 per 105.4,5 About 70% of patients with PSC have underlying IBD, most frequently ulcerative colitis (UC) in over 75% of cases.6 The prevalence of IBD in PSC patients ranges from 50% to 99% across different studies.6 Several factors could explain this large variation. In a recent systematic review, the studies that used both endoscopic and histological criteria for IBD diagnosis, showed a higher median percentage of IBD among PSC patients.6 Geographic differences could also contribute to this variation. Asian studies report a lower prevalence of IBD in PSC patients in comparison to European and American populations.7,8 However, in some of these studies, IBD diagnosis was established or excluded based on registry data or notes in medical files without reviewing original endoscopy or histology. In fact, a recent Japanese report by Sano
Although there may be a possible common pathogenesis between PSC and IBD, the two disorders can occur at different times. PSC may be diagnosed many years after proctocolectomy for colitis, and conversely IBD can appear many years after the initial diagnosis of PSC or even after OLT altogether.10 In most reports, IBD diagnosis precedes that of PSC.11,12 In a recent report, Sinakos
PSC is likely to have an underlying multifactorial etiology, with a predominant immune-mediated process.3 PSC and IBD are interrelated conditions that may well share an underlying predisposition (Fig. 1). Both diseases share common antibodies, such as those directed against cytoplasmic and nuclear antigens of neutrophils with a characteristic perinuclear staining pattern (p-ANCA). p-ANCA antibodies have been found in 26% to 85% of PSC patients and in up to 68% of patients with UC.3
From a genetic standpoint there is increasing evidence that PSC is distinct from UC and CD. Large-scale genome-wide association studies (GWAS) have identified close to 200 independent loci associated with IBD.16,17 Most of these loci are shared between UC and CD.16 GWAS studies in PSC have identified a total of 16 PSC susceptibility loci.18 In the most recent genetic analysis there was surprisingly limited overlap between PSC and IBD loci.19 Half of the PSC loci failed to show a robust association with IBD, suggesting overlapping yet distinct genetic mechanisms.19 Genetic predisposition to autoimmune bile duct injury triggered by toxic or infectious agents that may gain access through the diseased colon is potentially a major mechanism leading to PSC in IBD patients.
Two hypotheses that link PSC and IBD include the “gut lymphocyte homing” hypothesis and the “leaky gut” hypothesis.20 Activated lymphocytes from the inflamed and permeable gut may enter the enterohepatic circulation and persist as memory cells that cause hepatic inflammation.21,22 Some molecular features, such as chemokines and adhesion molecules, are shared by the liver and intestine and could contribute to lymphocyte binding at both sites.21 T cells activated in the gut during active IBD could differentiate into effector cells with the ability to bind to both hepatic and mucosal endothelium. The activation and expansion of these memory cells in the liver could eventually lead to the induction of MAdCAM-1 and CCL25 in the liver, promoting the recruitment of CCR9+ α4β7+ mucosal T cells and the development of inflammation.23 Findings such as PSC development after colectomy for IBD, or the development of IBD after OLT for PSC, have led some investigators to suggest that aberrant homing of lymphocytes between the intestine and liver could be involved in the pathogenesis of the PSC-IBD phenotype.21
The “leaky gut” hypothesis refers to the association between progressive hepatic and biliary injury and increased intestinal permeability and translocation of bacterial metabolites from the gut.24 The liver receives approximately 75% of its blood supply from the splanchnic circulation and is constantly exposed to both beneficial and noxious molecules from the intestinal microbiome.25 This so-called “gut-liver axis” is essential for the maintenance of health but may also play an important role in pathogenesis of liver and intestinal diseases.25,26 In IBD there is a known intestinal microbiome dysbiosis, characterized by lower biodiversity and decreased bacteria of the
The interaction between microbiota and bile acid (BA) metabolism may also play an important role in the PSC-IBD phenotype. Recent evidence supports the existence of BA dysmetabolism in IBD patients due to impaired microbiota enzymatic activity.27 One of the contributing factors for the difference in phenotype between PSC-IBD patients and IBD controls may be altered concentration and/or composition of colonic BA impacting on gut microbiota and stool BA metabolism.
In summary, PSC-IBD pathogenesis is still unclear but this phenotype is likely to have an underlying multifactorial etiology, influenced by genetic predisposition, immune-mediated processes and altered gut microbiota (Fig. 1).
Patients with the PSC-IBD phenotype have demographic features resembling PSC cases, although the PSC diagnosis tends to occur at a younger age, when compared with PSC-only controls (mean age, 33.6±17.2 years vs 58.9±18.2 years; p<0.001).9 The incidence is higher in males and is more prevalent in young and middle-aged patients.13–15 The age at clinical onset of IBD is controversial. Some reports indicate that the mean age for IBD diagnosis is higher among PSC-IBD patients compared with IBD controls,15 but a recent study reported that PSC-UC patients had a UC diagnosis at a significantly earlier age compared with UC controls (mean age, 24.5 years vs 33.8 years).31
As stated above, the co-occurrence of PSC with IBD is associated with a distinct IBD phenotype (Fig. 2). PSC-IBD patients typically have mild intestinal disease activity and an increased incidence of extensive colitis and pancolitis, rectal sparing and backwash ileitis (Table 1).9,10,12,13,15,31–38 Extensive colonic involvement, irrespective of the IBD subtype (i.e., CD vs UC), is the primary IBD phenotype associated with PSC. From a population-based cohort of 579 PSC patients in the Netherlands, pancolitis was observed in 94% of PSC-UC patients and in 96% of PSC-CD patients.37 Though rare, some patients with ulcerative proctitis and Crohn’s ileitis have concomitant PSC.37,39 Although pancolitis is a characteristic finding of PSC-IBD patients, it occurs at variable rates (35% to 95% of patients).6 Some cases are endoscopically diagnosed as right-sided IBD.11 In a recent systematic review, the majority of studies addressing disease activity found that the prevalence of inflammation was highest in the right colon and lowest toward the distal colon.6,9,12 This pattern of inflammation was significantly different from matched non-PSC IBD-controls.6,9,12
The frequency of rectal sparing and backwash ileitis in PSC-UC patients differs among reports. A recent systematic review reported an incidence of rectal sparing from 6% to 66% (versus 2% to 25% in IBD without PSC) and of backwash ileitis between 5% and 46% (compared to 3% to 24% in UC without PSC).6 It is worth noting that since PSC-IBD patients typically have quiescent disease, microscopic inflammation may still be present in spite of an endoscopically normal-appearing rectum.12 The frequency of rectal sparing and backwash ileitis should be investigated in future studies using a consensus definition.
In PSC-CD patients, the anatomic location of the disease differs from patients with isolated CD. Colonic involvement is the most often reported (37% to 82%), followed by ileocolic involvement (22% to 58%), and rarely isolated ileal involvement (2% to 5%).6 In PSC-CD patients there is a lower frequency of stricturing and penetrating disease compared to patients with isolated CD.6,39
Despite the higher prevalence of pancolitis, the intestinal inflammation in PSC-IBD patients is usually quiescent leading to mild symptoms, reduced use of steroids and decreased rates of hospitalization.9,10 On histological grounds, the colonic inflammation is also very mild, with only focal basal plasmacytosis and occasional mild cryptitis.10 Schaeffer
There is conflicting evidence regarding the course of IBD after OLT for PSC. Several reports demonstrated worsening colitis activity following OLT in approximately 30% of PSC-IBD patients.3 Furthermore, de-novo IBD after OLT has also been reported and it may develop in 14% to 30% of PSC patients up to 10 years after transplantation.40 Retrospective studies comparing IBD activity before and after liver transplantation found that endoscopic colonic inflammation was more frequent after OLT, as was the rate of relapse and overall clinical IBD activity.41,42 A retrospective study of 31 patients with PSC-UC who received OLT, showed that the Mayo score was higher after transplantation compared with the pre-transplant score (mean score, 2.91±0.9 vs 6.64±3.7; p=0.009).38 The above findings have led to the speculation that the diseased PSC liver somehow keeps colonic inflammation in check. Several factors may be associated with a worse course of IBD after OLT such as a new balance in the immune system favoring an immune-mediated attack against the colonic mucosa, the presence of active IBD at the time of transplantation, discontinuation of 5-aminosalicylates, infrequent use of azathioprine and the use of tacrolimus.35,42 Haagsma
Of note, the worsening of IBD after OLT has not been universally confirmed. Jorgensen
PSC-IBD patients who undergo proctocolectomy with ileal pouch anal anastomosis (IPAA) have a higher risk of developing pouchitis, which affects 13.8% to 90% of cases (versus 33% in patients with conventional IBD).6,13,15 Nonetheless, the long-term outcomes are often satisfactory,45 with the incidence of pouch failure in PSC-IBD patients subjected to IPAA being similar to IBD-only patients.6 Mathis
While PSC is often associated with a distinctive IBD phenotype,35 the effect of IBD on the natural history and disease behavior of PSC is less well defined. In PSC patients with concomitant IBD, the PSC phenotype may differ when compared to PSC patients without IBD. Combined intrahepatic and extrahepatic biliary involvement has been described to be more common in PSC-IBD patients compared to PSC patients alone (81.5% vs 46.2%, p<0.05),46 but has not always been described in the literature. At least two other retrospective reviews have refuted the finding of a higher prevalence of intra- and extra-hepatic biliary involvement in patients with coexisting IBD.47,48
Long-term PSC outcomes also do not seem to be associated with the presence or disease severity of IBD. In a natural history study of 305 Swedish PSC patients, associated IBD had no prognostic significance on the need for OLT or liver-related deaths.49 Similarly, transplant-free survival rates, cirrhosis rates, and mortality of PSC patients were found to be independent of concomitant IBD in a retrospective Israeli study of 141 PSC patients.48 Navaneethan
In contrast to the majority of findings reported in the aforementioned studies, some of the PSC-IBD literature suggests that the rapidity of PSC disease progression may be contingent upon the specific IBD phenotype. A retrospective case-controlled study utilizing the Oxford PSC and IBD databases revealed that major event-free survival (cancer, OLT or death) was prolonged in the PSC-CD group compared to the PSC-UC group (Cox regression, p=0.04).39 The authors postulate that this may be explained by the increased prevalence of small-duct PSC in PSC-CD patients compared to PSC-UC patients, which was also suggested by Rasmussen
PSC recurrence (rPSC) after OLT occurs in 30% to 50% of patients, usually 10 years posttransplantation.54 Akin to the data available regarding the relationship between IBD and PSC disease progression, the presence of concomitant IBD in PSC patients has not been unanimously identified as a risk factor for rPSC. In a systematic review of autoimmune liver diseases after transplantation, there was no statistically significant difference in the rate of rPSC in patients with and without IBD.55 In another retrospective analysis of 31 PSC patients who underwent OLT, 5-year survival rates, infectious complications, frequency of rejection and need for re-transplantation did not differ based on whether patients had coexisting IBD.56 Moreover, a retrospective analysis of 105 PSC patients who underwent OLT revealed no correlation between rPSC and IBD activity.57 On the contrary however, in another study PSC patients with UC had significantly more rPSC compared to PSC patients without UC.58 Several publications have described that an intact colon is a strong predictor of rPSC and that colectomy potentially has a protective effect against rPSC. In a cohort of 230 PSC patients who underwent OLT, colectomy pre- and peri-OLT conferred a protective effect against rPSC in the transplanted graft.59 Moreover, an intact colon prior to OLT was the strongest predictor of rPSC. Joshi
Despite opposing evidence on the association of IBD with rPSC, data supports that PSC-IBD patients are at risk for a greater number of acute cellular rejection (ACR) episodes post-OLT.62,63 In a retrospective chart review of 55 PSC patients who underwent OLT, the incidence of acute rejection was higher in PSC-IBD patients compared to PSC patients (27/31 vs 10/24, p=0.0006).64 Moreover, PSC-IBD patients who were diagnosed with IBD at a younger age were more likely to develop severe acute rejection. In spite of the increased incidence of ACR in this study, 5-year survival rates and rPSC post-OLT did not vary based on the presence of concomitant IBD.
Since its initial description by Broome
The mechanisms underlying the increased risk of CRN in PSC-IBD patients remain unknown. Different authors proposed a variety of mechanisms that may be partially responsible for this outcome (summarized in Table 3), though these are still not conclusive. In rat models, BA have been found to have a carcinogenic potential94,95 (specifically secondary BA, like deoxycholic acid).96 A different stool BA abundance and/or composition could potentially be involved in the right-sided CRN risk observed in PSC-IBD,97,98 although this has never been demonstrated. Whether the specific dysbiosis that has been described in PSC-IBD could be involved in this risk remains unknown.99–102 Other mechanisms described include inactivation of the Farnesoid X receptor pathway,87,103,104 shown to be involved in hepatic and colonic inflammation and CRC, and polymorphisms in two genes in the chromosome 6p21. A more comprehensive understanding of the PSC pathogenesis and the involved BA dysmetabolism and microbiota dysbiosis will probably help to clarify the mechanisms involved in the increased CRN risk in these patients.
One would hypothesize that once indefinite or low-grade dysplasia (LGD) is diagnosed in PSC-IBD, the rate of progression to high-grade dysplasia or CRC would be faster than in IBD patients. However, while some studies have described the rate of progression of indefinite and LGD in IBD-only patients, the rate of progression of CRN in patients with PSC-IBD has not been thoroughly studied. In a small study with 10 patients, one-third of the patients progressed from LGD to advanced neoplasia over a mean follow-up of 13±11 months, suggesting a faster rate of progression as compared to what has been described in IBD alone.105
Since many patients with PSC require OLT,106 some uncertainty exists regarding the effect of the strong immunosuppressive agents in the post-OLT setting, leading to an increased risk for CRN versus the “protective” effect of curing the PSC on the risk of CRN. Some of the initial studies107,108 showed that there was no difference in the rate of CRN in the post-OLT PSC-IBD group compared to post-OLT non-IBD/PSC and nontransplanted PSC-IBD patients. More recent studies have suggested that there may be even a 4-fold greater risk of CRN, though there was no evidence of any relevant impact on mortality.109,110 Particularly, one study suggested that patients who developed LGD after OLT had a slower rate of progression and were less likely to have progressive neoplasia or persistent LGD.111
Another subset of the PSC-IBD population who are at risk for neoplasia are the patients who have undergone an IPAA, given that their increased incidence of pouchitis theoretically leads to severe mucosal atrophy and subsequent pouch malignancy.112 Although a small study showed an increased risk of ileal pouch dysplasia in PSC-IBD compared to non-IBD and non-PSC populations separately,113 a larger study that included 65 patients suggested a low risk of 5.6% in 5-year for pouch or cuff dysplasia (95% CI, 1.8% to 16.1%).114 Particularly, CRC has been documented but is extremely uncommon after IPAA.115 There are no specific surveillance guidelines for post-IPAA PSC-IBD patients, so most experts prefer annual pouchoscopies as standard care for PSC patients, even though the risk seems to be low.
Given that the risks of CRN have been widely described in the PSC-IBD population, the different gastroenterology societies have commented on recommendations for surveillance in this group. Current recommendations support the use of annual colonoscopy and biopsies in PSC-IBD patients from the time of PSC diagnosis, without taking into account the duration of IBD since it is often not known.116,117 No specific recommendations on the management and follow-up of indefinite or LGD exist for this high-risk population that may be more prone to be referred for colectomy, given the elevated risk of CRC. Hence, further studies are needed to better determine the outcomes regarding low-grade and indefinite dysplasia in PSC-IBD patients.
UDCA118 has been in the past considered an option in the prevention of CRN in PSC-IBD patients. However, studies have shown mixed results: some of them with decreased risk of CRN,119,120 others not showing any effect in the incidence of neoplasia,89,121,122 and others even showing an increased risk with high-dose UDCA, usually in the first 6 years after the medication was started.123 A meta-analysis in 2013, evaluating eight studies with 763 PSC-IBD patients, concluded that there is a preventive effect for the development of advanced CRN when taking UDCA (OR, 0.35; 95% CI, 0.17 to 0.73), with a more pronounced effect with the 8 to 15 mg/kg/day dose (OR, 0.19; 95% CI, 0.08 to 0.49).124 Therefore, while there might be a protective effect, more studies are needed to draw more definitive conclusions.
In a recent large retrospective review of 399 PSC-IBD patients from the Mayo Clinic, a prolonged duration of IBD was associated with an increased risk of cholangiocarcinoma (CCA) in PSC patients.125 This increased risk equated to a 33% increased risk per 10 years of IBD and the risk was not modified by colectomy. Furthermore, in the subset of PSC-IBD patients requiring colectomy, patients who underwent surgery due to colonic neoplasia or dysplasia as opposed to refractory disease were also at a significantly higher risk of CCA. From an earlier published study conducted at Mayo Clinic, although IBD was not associated with CCA risk, proctocolectomy was a significant risk factor on univariate analysis for the development of CCA in PSC patients (relative risk, 4.43).126 It is unclear if the observed elevated cancer risk may be secondary to the effect of immunosuppression or the severity of intestinal inflammation.
The increased predisposition to malignant transformation may not only apply to the biliary system in PSC-IBD patients. From a population-based study in New Zealand, 14 of 60 PSC-IBD patients developed a malignant complication including CRC, hepatocellular carcinoma or CCA whereas none of the 19 PSC patients without IBD did.51 Nevertheless, in another study of 66 PSC patients, the prevalence of malignant complications was not dependent on the presence or absence of IBD,46 nor did it play a role in a natural history study of 305 Swedish PSC patients49 or a long-term single-center study of 200 PSC patients.127
IBD affects about 70% of patients with PSC. Although there is likely an underlying shared predisposition for PSC and IBD, the pathogenesis of these interrelated conditions is still unknown. These diseases are likely to be influenced by genetic predisposition, immune-mediated processes and altered gut microbiota. Clinically, PSC-IBD patients demonstrate a right-to-left gradient of colonic inflammation as well as an increased incidence of extensive colitis, rectal sparing and backwash ileitis. Despite the higher prevalence of pancolitis, the intestinal inflammation is usually quiescent leading to mild symptoms, reduced use of steroids and decreased rates of hospitalization. Nevertheless, post-IPAA, the rates of pouchitis in PSC-UC patients are higher compared to non-PSC UC patients. While PSC is associated with a distinct IBD phenotype, the effect of IBD on the natural history and disease behavior of PSC, including recurrent PSC post-OLT, is less well defined. Overall, the PSC-IBD population has an increased risk of developing CRN and CRC compared to the IBD-only population. Moreover, IBD may also be also associated with an increased risk of CCA in PSC patients.
In summary, PSC-IBD is a puzzling disease with a very special phenotype (Fig. 2); a better understanding of the mechanisms underlying the cross talk between the liver and the gut is needed and could lead to the development of new strategies.
S.H.I. was funded in part by a grant from The Chemotherapy Foundation. F.P. would like to acknowledge the Canadian Institutes of Health Research and the Canadian Association of Gastroenterology for supporting his advanced inflammatory bowel disease fellowship and research.
GWAS, genome-wide association studies.
Table 1 Studies Evaluating IBD Extension, Backwash Ileitis, and Spared Rectum in PSC-IBD Patients Compared to IBD-Only Controls
Study | Year | No. of patients | IBD extension (proctitis/left-sided/pancolitis) % | Backwash ileitis % | Rectal sparing % | ||||
---|---|---|---|---|---|---|---|---|---|
PSC-IBD | IBD | PSC-IBD | IBD | PSC-IBD | IBD | PSC-IBD | IBD | ||
Olsson | 1991 | 55 | 1,445 | 5.5/NA/94.5 | 38.2/NA/61.8 | NA | NA | NA | NA |
Loftus | 2005 | 71 | 142 | NA/NA/87 | NA/NA/54 | 51 | 7 | 52 | 6 |
Sokol | 2008 | 75 | 150 | NA | NA | 18.7 | 24 | 20 | 13.3 |
Joo | 2009 | 40 | 40 | 0/7.5/85 | 0/35/45 | 10 | 7.5 | 27.5 | 25 |
Sano | 2011 | 20 | 60 | 5/5/35 | 30/31.7/35 | NA | NA | NA | NA |
Ye | 2011 | 21 | 63 | NA/NA/95.2 | NA/NA/55.6 | 42.9 | 3.2 | 38.1 | 1.6 |
Marelli | 2011 | 96 | 0 | 0/10/90 | NA | NA | NA | NA | NA |
Jorgensen | 2012 | 110 | 0 | NA/3/55 | NA | 20 | NA | 65 | NA |
O’Toole | 2012 | 103 | 2,649 | 1/22.3/54.4 | 7.9/24.5/25 | NA | NA | NA | NA |
Boonstra | 2012 | 80 | 80 | 2.5/2.5/65 | 5/20/43.8 | 5 | 2.5 | 10 | 1.3 |
Gelley | 2012 | 20 | 0 | 15/15/55 | NA | NA | NA | NA | NA |
Schaeffer | 2013 | 97 | 0 | 0/17.5/43.4 | NA | NA | NA | NA | NA |
Sinakos | 2013 | 129 | 0 | NA/12.4/58.9 | NA | 11.6 | NA | 24 | NA |
IBD, inflammatory bowel disease; PSC, primary sclerosing cholangitis; NA, not available.
Table 2 Studies Evaluating the Risk of Colorectal Neoplasia in PSC-IBD Patients
Study | Year | Type of study | No. of patients | Outcome |
---|---|---|---|---|
Broome | 1992 | Prospective | 72 UC patients followed to see presence of CRN | 28% of patients with CRN and/or DNA aneuploidy had IBD and PSC, which was statistically significant (p=0.0004). |
Broome | 1995 | Prospective | 40 Patients with PSC-UC vs 2 groups of 40 UC-only patients | Risk of CRN in PSC-UC was 9%, 31%, and 50% after 10, 20, and 25 years of disease, compared to 2%, 5%, and 10% in UC-only patients (p<0.001). |
Brentnall | 1996 | Prospective | 20 Patients with PSC-UC vs 25 UC-only patients | Colonic neoplasia was present in 45% of PSC-UC patients, vs 16% in UC-only (p=0.002). |
Leidenius | 1997 | Retrospective | 48 Patients with PSC-UC vs 45 UC-only patients | CRN presented in 29% of PSC-UC patients, vs 9% in UC-only (p<0.05). |
Marchesa | 1997 | Retrospective | 27 Patients with PSC-UC vs 1,185 UC-only patients | Colonic neoplasia was present in 59.5% of PSC-UC patients vs 11.5% in UC-only patients (RR, 6.9; 95% CI, 3.0–16.0). |
Shetty | 1999 | Prospective | 132 Patients with PSC-UC vs 196 UC-only patients | CRN presented in 25% of PSC-UC patients, vs 5.6% in UC-only (adjusted RR, 3.15; 95% CI, 1.37–7.27; p<0.001). |
Jess | 2007 | Retrospective | 43 Patients with CRN, vs 102 control patients | PSC was associated with a higher risk of developing CRN (OR, 6.9; 95% CI, 1.2–40). |
Terg | 2008 | Prospective | 1,333 Patients with UC-39 had PSC, which were matched to two control patients | CRC presented in 18% of PSC-UC patients, vs 2.6% in matched UC-only patients (p=0.006). Risk of CRC in PSC-UC was 11% and 18% after 10 and 20 years vs 2% and 7% in UC-only, respectively (p=0.002). |
Sokol | 2008 | Prospective | 75 Patients with PSC-IBD vs 152 IBD-only patients | 25 Years cumulative risk of CRN was 23.4% in PSC-IBD vs 0% in IBD-only (p=0.002). PSC was a risk factor for CRC (OR, 10.8; 95% CI, 3.7–31.3). |
Lindstrom | 2011 | Prospective | 28 Patients with PSC-CD vs 46 CD-only patients | CRN presented in 32% of PSC-CD patients, vs 7% in CD-only (OR, 6.78; 95% CI, 1.65–27.9; p=0.016). |
Ananthakrishnan | 2014 | Retrospective | 224 Patients with PSC-IBD, from a pool of 5,506 CD and 5,522 UC patients | PSC-IBD had a higher risk of CRC (OR, 5.00; 95% CI, 2.80–8.95) and digestive tract cancer (OR, 10.4; 95% CI, 6.86–15.76), compared to IBD-only patients. |
Navaneethan | 2016 | Retrospective | 223 Patients with PSC-UC vs 50 with PSC-CD | PSC-UC patients had higher risk for colonic neoplasia compared to PSC-CD (35.9% vs 18%, p=0.009). |
PSC, primary sclerosing cholangitis; IBD, inflammatory bowel disease; UC, ulcerative colitis; CRN, colorectal neoplasia; RR, relative risk; CI, confidence interval; OR, odds ratio; CD, Crohn’s disease.
Table 3 Proposed Mechanisms for the Increased Risk of Colorectal Neoplasia in PSC-IBD Patients
Mechanism | Explanation |
---|---|
Genetic | Polymorphisms present in TNFα promoter and specific genome associations in proximity to HLA complex on chromosome 6p21 have been associated with a higher likelihood of developing CRN. |
Bile acid | Cholestasis favors decreased intestinal BA reabsorption. Microbiota convert primary BA to secondary BA, which have a carcinogenic potential. |
FXR pathway | FX secretion by the intestine is induced by the presence of BA. Normally, FX leads to a decrease in the production of BA by the liver. |
Microbiome | Gut bacteria are presumed to act on altered BA composition resulting in proinflammatory and procarcinogenic compounds. |
PSC, primary sclerosing cholangitis; IBD, inflammatory bowel disease; TNF, tumor necrosis factor; HLA, human leukocyte antigen; CRN, colorectal neoplasia; BA, bile acid; FXR, farnesoid X receptor; FX, farnesoid X.