PSC damages the bile ducts slowly and persistently, so its complications are the consequences of chronic biliary obstruction and chronic cholestasis — and, unusually for a cholestatic disease, a striking excess of cancer.
Dominant strictures and recurrent cholangitis
A dominant stricture is a narrowed segment of a major bile duct that obstructs the flow of bile. Dominant strictures explain the intermittent pattern PSC is known for: episodes of jaundice, pruritus, right upper quadrant pain, fever and chills, separated by intervals when the patient feels well. These episodes are attacks of bacterial cholangitis — infection arising behind obstructed bile — and they can be severe. A stricture that becomes malignant can look the same, so a dominant stricture has to be assessed rather than assumed to be benign.
Cirrhosis and portal hypertension
Repeated inflammation and fibrosis eventually replace the normal architecture of the liver with the nodules of biliary cirrhosis. Once cirrhosis and portal hypertension — raised pressure in the portal venous system — are established, the usual consequences follow: ascites, oesophageal varices and variceal bleeding, enlargement of the spleen, hepatic encephalopathy and muscle wasting. These are the features of decompensated liver disease, and together with cancer they determine prognosis.
Cancer
The most feared complication of PSC is cholangiocarcinoma, cancer of the bile ducts. About 10% of patients with PSC develop a biliary cancer, and it can appear at any stage of the disease, including in a patient whose liver disease still looks mild. Cholangiocarcinoma is difficult to detect because its imaging features overlap with those of a benign dominant stricture, which is why surveillance is part of management.
The gallbladder is also involved in PSC. Gallstones occur in about a quarter of patients, and gallbladder masses or polyps in 4–6.5%; more than half of these mass lesions are malignant. A gallbladder polyp larger than 8 mm is an indication for cholecystectomy in a patient with PSC.
PSC also raises the risk of colorectal cancer. In patients who have both PSC and ulcerative colitis the risk of colorectal adenocarcinoma is about five times higher than in ulcerative colitis alone, so the large bowel is examined as part of the follow-up of these patients.