Laboratory Studies
The following laboratory studies can be evaluated to help make the diagnosis of acute fatty liver of pregnancy (AFLP).
-
Aspartate transaminase (AST) and alanine transaminase (ALT) are not elevated in normal pregnancies. These can become elevated in many different conditions during pregnancy. Some are unique to pregnancy, such as preeclampsia/eclampsia, HELLP, and AFLP. High levels of ALT can be seen in patients with viral hepatitis; however, the highest levels are seen in patients with acute toxic liver injury, as can be seen in acetaminophen overdose. [15] Both AST and ALT can be elevated due to the hepatic injury.
-
Hepatic injury results in decreased gluconeogenesis and, therefore, decreased blood glucose levels.
-
Liver detoxification is also affected, resulting in elevated levels of blood ammonia, especially late in the disease course.
-
In addition, laboratory findings may be consistent with disseminated intravascular coagulation (DIC), specifically, prolongation of prothrombin time, low fibrinogen, and low antithrombin levels. This results in a clinical picture similar to DIC; however, in AFLP, the values are abnormal, not due to consumption of the clotting factors but rather to decreased production by the damaged liver. [16]
-
Bilirubin levels are elevated. This elevation is primarily the conjugated form, with levels exceeding 5 mg/dL. This can result in jaundice, which is rarely seen in patients with other forms of pregnancy-related hepatic injury, including preeclampsia.
-
Some patients may develop pancreatitis, which can result in elevated amylase, lipase, and increased blood sugars.
-
As the maternal kidneys become affected, blood creatine and uric acid can become elevated, leading to metabolic acidosis.
-
A study by Meng et al that looked to identify prenatal predictors of AFLP in 43 patients reported that prenatal serum bilirubin, prothrombin time, plasma fibrinogen levels and platelet counts are all predictors of postpartum recovery. [17]
Imaging Studies
Imaging studies have a low sensitivity for diagnosing AFLP and should not be used to exclude the diagnosis. Liver ultrasonographic examination may reveal increased echogenicity in severe cases. A computed tomography (CT) scan may show decreased or diffuse attenuation in the liver. [18]
Histologic Findings
Although the criterion standard for diagnosis of AFLP is liver biopsy, this is rarely performed in clinical practice due to the risk of hemorrhage. In addition, AFLP can easily be differentiated from viral or drug-induced hepatitis by obtaining viral serologies and measuring acetaminophen levels in serum.
If a biopsy is performed, the histological findings demonstrate pericentral microvesicular fat infiltration with minimal inflammation or necrosis. [15]
