If you suspect ICP in a patient who is also jaundiced, you’ll also need to rule out several other conditions. These include:
- acute liver disease of pregnancy
- preeclampsia complicated by increased liver enzymes
- hyperemesis gravidarum
- viral hepatitis
- drug reaction
- obstructive biliary disease, such as a gallstone lodged in the common bile duct.
Order a blood chemistry or liver profile
If you suspect that your patient has ICP, start by ordering a blood chemistry or liver profile. If any of the liver tests are elevated, order a total bile acid level (which is the most sensitive indicator of ICP) and a hepatitis panel (or specific hepatitis tests based on the patient’s history of exposures and vaccinations). If there is laboratory evidence of cholestasis, a right upper quadrant ultrasound will help you to spot gallstones and evidence of obstruction.
In ICP, there will be mild abnormalities of the liver function tests, including transaminases, alkaline phosphatase, and bilirubin. Bilirubin may be mildly to moderately elevated (2–5 mg/dL). (Jaundice is seen only at the higher levels of bilirubin.) Our patient’s tests, for instance, revealed that her ALT and AST were both over 300; her total bilirubin was elevated at 2.1.
Serum levels of bile acid correlate with the severity of pruritus. Our patient’s bile acids were elevated and her hepatitis panel was negative. Her ultrasound showed gallstones, but we saw no obstruction. An ICP patient’s lipid profile may show mild elevations in total cholesterol and triglycerides, as was the case for our patient.
Malabsorption of fat may cause vitamin K deficiency resulting in a prolonged prothrombin time. Liver biopsy is unnecessary in suspected cases of ICP, but would show cholestatic changes such as dilated bile canaliculi, bile pigment in the parenchyma, and minimal inflammation.
Skin biopsy is not helpful in ICP
In suspected cases of ICP, skin biopsy will only reveal a spectrum of non-specific findings. It is, however, helpful if you suspect pemphigoid gestationis, since it will reveal subepidermal blisters. Similarly, biopsy for direct immunofluorescence is nonspecific in ICP, but helpful in pemphigoid gestationis.