Primary sclerosing cholangitis and inflammatory bowel disease comorbidity: an update of the evidence

Abstract

Comorbid primary sclerosing cholangitis (PSC) and inflammatory bowel disease (IBD) represent a unique disease phenotype with a different risk profile than PSC or IBD alone. While the pathogenetic mechanisms behind both diseases remain unclear, recent studies have targeted several immune-mediated pathways in an attempt to find a potential therapeutic target. Patients with PSC-associated IBD typically exhibit pancolitis with a right-to-left intestinal inflammatory gradient associated with a greater incidence of backwash ileitis and rectal sparing. Although there is an increased incidence of pancolitis in this population, bowel symptoms tend to be less significant than in IBD alone. Likewise, the degree of inflammation and symptoms of PSC-associated IBD are characteristically less clinically significant. Despite the relatively quiescent clinical presentation of PSC-associated IBD, there is an increased risk for colorectal and hepatobiliary malignancy making vigilance for malignancy essential.

Keywords: Crohn’s disease; Primary sclerosing cholangitis; inflammatory bowel disease; ulcerative colitis.

Figure 1

PSC-IBD diagnostic algorithm [18,19,58,78-80] *R-factor is defined as the ratio of alanine aminotransferase (ALT) to alkaline phosphatase (ALP) elevation as compared to the upper limit of normal (ULN). The following equation can be used to obtain this value: R-factor= (ALT/ALTULN) ÷ (ALP/ALPULN). If the quotient is less than 2, then it suggests a cholestatic process. A quotient of 2-5 suggests a mixed process and values greater than 5 suggest a hepatocellular injury pattern ‡MRCP is the preferred imaging modality for diagnosis of PSC as it has good diagnostic accuracy and does not carry the potential risks associated with endoscopic retrograde cholangiopancreatography PSC, primary sclerosing cholangitis; IBD, inflammatory bowel disease; MRCP, magnetic resonance cholangiopancreatography; CRC, colorectal cancer; Ab, antibody; RUQ, right upper quadrant; U/S, ultrasound.

Figure 2

PSC-IBD malignancy screening algorithm [58,78-80,85,86] PSC, primary sclerosing cholangitis; IBD, inflammatory bowel disease; MRI, magnetic resonance imaging; MRCP, magnetic resonance cholangiopancreatography; CRC, colorectal cancer; CCA, cholangiocarcinoma; FISH, fluorescence in situ hybridization; US, ultrasound.