Primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a long-term progressive disease of the

The bile duct scarring that occurs in PSC narrows the ducts of the biliary tree and impedes the flow of bile to the intestines. Eventually, it can lead to

No effective medical treatment for primary sclerosing cholangitis is known. Its most definitive treatment is a liver transplant,^[1] but disease recurrence can occur in 25-30% of cases.^[6]

PSC is a rare disease and most commonly affects people with IBD.^[2] About 3.0 to 7.5% of people with ulcerative colitis have PSC, and 80% of people with PSC have some form of IBD.^[3] Diagnosis usually occurs in people in their 30s or 40s.^[3] Individuals of Northern European ancestry are affected more often than people of Southern European or Asian descent.^[2] Men are affected more often than women.^[7] The disease was initially described in the mid-1800s, but was not fully characterized until the 1970s with the advent of improved medical-imaging techniques such as endoscopic retrograde cholangiopancreatography.^[7]

Signs and symptoms

Nearly half of people with PSC do not have symptoms, and are often incidentally discovered to have PSC due to abnormal

• Dark urine due to excess
  conjugated bilirubin
  , which is water-soluble and excreted by the kidneys (i.e. choluria)
• Malabsorption, especially of fat, and steatorrhea (fatty stool), due to an inadequate amount of bile reaching the small intestine, leading to decreased levels of the fat-soluble vitamins, A, D, E, and K.
• Portal hypertension, a complication of cirrhosis, which can manifest with esophageal and parastomal varices^[10] as well as hepatic encephalopathy (mental status alteration/disturbance caused by liver dysfunction and shunting of blood away from the scarred liver; such that ammonia detoxification is reduced with concomitant encephalopathy) or ascites.

Cause

The exact cause of primary sclerosing cholangitis is unknown, and its pathogenesis is improperly understood.^[1] Although PSC is thought to be caused by autoimmune disease, it does not demonstrate a clear response to immunosuppressants. Thus, many experts believe it to be a complex, multifactorial (including immune-mediated) disorder and perhaps one that encompasses several different hepatobiliary diseases.^[11][12]

Data have provided novel insights suggesting:

1. an important association between the intestinal microbiota and PSC^[13][14][15] and
2. a process referred to as cellular senescence and the senescence-associated secretory phenotype in the pathogenesis of PSC.^[16][17]

In addition, longstanding, well-recognized associations are seen between PSC and human leukocyte antigen alleles (A1, B8, and DR3).^[4]

Pathophysiology

PSC is characterized by inflammation of the bile ducts (cholangitis) with consequent stricturing (i.e., narrowing) and hardening (sclerosis) of these ducts due to scar formation, be it inside and/or outside the liver.^[18] The resulting scarring of the bile ducts obstructs the flow of bile, which further perpetuates bile duct and liver injury. Chronic impairment of bile flow due to blockage and dysfunctional bile transport (cholestasis) causes progressive biliary fibrosis and ultimately biliary cirrhosis and liver failure.^[19]

The primary physiological function of bile is to assist in the breakdown and absorption of fat in the intestinal tract; a relative deficiency of bile can lead to fat malabsorption and deficiencies of

Liver enlargement is seen due to portal hypertension caused by compression of portal veins by the proximate sclerosed intrahepatic bile ducts, and leads to right upper quadrant abdominal pain.^{[citation needed]}

Diagnosis

PSC is generally diagnosed on the basis of having at least two of three clinical criteria after secondary causes of sclerosing cholangitis have been ruled out:^{[citation needed]}

• serum alkaline phosphatase (ALP) > 1.5x the upper limit of normal for longer than 6 months
• cholangiography demonstrating biliary strictures or irregularity consistent with PSC
• liver biopsy consistent with PSC (if available)

Historically, a cholangiogram would be obtained via endoscopic retrograde cholangiopancreatography (ERCP), which typically reveals "beading" (alternating strictures and dilation) of the bile ducts inside and/or outside the liver. Currently, the preferred option for diagnostic cholangiography, given its noninvasive yet highly accurate nature, is magnetic resonance cholangiopancreatography (MRCP), a magnetic resonance imaging technique. MRCP has unique strengths, including high spatial resolution, and can even be used to visualize the biliary tract of small animal models of PSC.^[21]

Most people with PSC have evidence of

Primary sclerosing cholangitis is typically classified into three subgroups based on whether the small and/or large bile ducts are affected. The subgroups of PSC include:[1]

• Classic PSC
• Small-duct PSC
• PSC associated with autoimmune hepatitis

Management

No pharmacologic treatment has been approved by the U.S. Food and Drug Administration for PSC. Some experts recommend a trial of ursodeoxycholic acid (UDCA), a bile acid occurring naturally in small quantities in humans, as it has been shown to lower elevated liver enzyme numbers in patients with PSC and has proven effective in other cholestatic liver diseases. However, UDCA has yet to be shown to clearly lead to improved liver histology and survival.^[8][26] Guidelines from the American Association for the Study of Liver Diseases and the American College of Gastroenterology do not support the use of UDCA but guidelines from the European Association for the Study of the Liver do endorse the use of moderate doses (13-15 milligrams per kilogram) of UDCA for PSC.^{[1][27][28][29]}

Supportive treatment for PSC symptoms is the cornerstone of management. These therapies are aimed at relieving symptoms such as itching with

ERCP and specialized techniques may also be needed to help distinguish between a benign PSC stricture and a bile-duct cancer (cholangiocarcinoma).[31]

Liver transplantation is the only proven long-term treatment of PSC. Indications for transplantation include recurrent bacterial ascending cholangitis, decompensated cirrhosis, hepatocellular carcinoma, hilar cholangiocarcinoma, and complications of portal hypertension. Not all patients are candidates for liver transplantation, and some experience disease recurrence afterward.^[11] The reasons why some patients develop recurrent PSC remains largely obscure, but surprisingly, those without recurrence of disease (hence protected from recurrence) are characterized by an increased presence of the potentially pathogenic Shigella species.^[32]

Prognosis

Estimated median survival from diagnosis until liver transplant or PSC-related death is 21.3 years.^[33] Various models have been developed to help predict survival,^[34] but their use is generally best suited for research and not clinical purposes. A serum alkaline phosphatase less than 1.5 times the upper limit of normal has been associated with better outcomes, but its use in predicting long-term outcomes is unclear.^[1] An IgA isotype autoantibody to the pancreatic GP2 protein (anti-GP2 IgA antibody) is the first verified prognostic biomarker in PSC.^[35] The role of anti-GP2 IgA in PSC was simultaneously investigated and reported by two research groups,^[36][37] and later confirmed by others.^[38][39] Association was demonstrated between anti-GP2 IgA and progressive liver fibrosis, cholangiocarcinoma development and shorter transplantation free survival in PSC patients.^[35]

Other markers which may be measured and monitored are a

The development of any of the cancers associated with PSC predicts a poor prognosis. Complications from PSC-associated cancers account for 40% of deaths from PSC.[2] Primary sclerosing cholangitis is one of the major known risk factors for cholangiocarcinoma,^[40] a cancer of the biliary tree, for which the lifetime risk among patients with PSC is 10-15%.^[3] This represents a 400-fold greater risk of developing cholangiocarcinoma compared to the general population.^[1] Surveillance for cholangiocarcinoma in patients with PSC is encouraged, with some experts recommending annual surveillance with a specialized imaging study and serum markers,^[41] although consensus regarding the modality and interval has yet to be established.^{[citation needed]} Similarly, a screening colonoscopy is recommended in people who receive a new diagnosis of primary sclerosing cholangitis since their risk of colorectal cancer is 10 times higher than that of the general population.^[1]

PSC is strongly associated with IBD, in particular ulcerative colitis (UC) and to a lesser extent Crohn's disease. As many as 5% of patients with IBD are co-diagnosed with PSC,^[42] and approximately 70% of people with PSC have IBD.^[19] Of note, the presence of colitis appears to be associated with a greater risk of liver disease progression and bile duct cancer (cholangiocarcinoma) development, although this relationship remains poorly understood.^[43] Close monitoring of PSC patients is vital.

Various forms of gallbladder disease such as gallstones and gallbladder polyps are also common in those with PSC.^[1] Approximately 25% of people with PSC have gallstones.^[1] Ultrasound surveillance of the gallbladder every year is recommended for people with PSC.^[1] Any person with PSC who is found to have a mass in the gallbladder should undergo surgical removal of the gallbladder due to the high risk of cholangiocarcinoma.^[1] Osteoporosis (hepatic osteodystrophy) and hypothyroidism are also associated with PSC.^{[citation needed]}

A 2–3:1 male-to-female predilection occurs in primary sclerosing cholangitis.

Although no curative treatment is known, several clinical trials are underway that aim to slow progression of this liver disease.[45] Obeticholic acid is being investigated as a possible treatment for PSC due to its antifibrotic effects. Simtuzumab is a monoclonal antibody against the profibrotic enzyme LOXL2 that is being developed as a possible therapy for PSC.^[1]

Notable cases

• Chris Klug – professional snowboarder with PSC who had liver transplant ^[46]
• Chris LeDoux – professional rodeo rider and country musician with PSC who died of cholangiocarcinoma
• Elena Baltacha – British professional tennis player, diagnosed with PSC at age 19 and died five months after being diagnosed with PSC-associated liver cancer (specifically cholangiocarcinoma) at the age of 30
• Walter Payton – died of complications of PSC
• Kieron Dyer – professional footballer
• James Redford – director and son of Robert Redford who underwent two liver transplants due to PSC^[47]
• Lars-Göran Petrov – Swedish death metal vocalist best known for his work with Entombed

References