What ultrasound findings are typical in a third‑trimester pregnant woman with acute fatty liver of pregnancy?

Ultrasound Findings in Acute Fatty Liver of Pregnancy

Ultrasound examination in acute fatty liver of pregnancy (AFLP) is frequently normal or shows only nonspecific findings, and cannot be relied upon to confirm or exclude the diagnosis.

Imaging Sensitivity and Limitations

The diagnostic yield of ultrasound in AFLP is disappointingly low:

• Only 27% of patients (3 of 11) with confirmed AFLP showed findings consistent with fatty infiltration on ultrasound in the largest imaging review. 1
• In another series, ultrasound appeared completely normal in 4 of 5 patients with biopsy-proven AFLP. 2
• When fatty liver changes are detected, ultrasound shows enhanced echo or fatty liver infiltration in approximately 73% of cases (11 of 15 patients in one series). 3

Typical Ultrasound Findings When Present

When abnormalities are detected, the following patterns may be seen:

• Increased echogenicity of the liver parenchyma 4
• Increasingly coarsened echo-pattern 5
• Enhanced echo texture consistent with fatty infiltration 3
• Mild to moderate fatty liver infiltration 5

Critical Clinical Pitfall

Normal ultrasound findings do not exclude AFLP and should never delay delivery. 1, 2 In fact, three patients with initially normal ultrasound examinations subsequently showed fatty infiltration on CT scanning, demonstrating ultrasound's inferior sensitivity. 1

Comparative Imaging Modalities

• CT scanning has superior sensitivity, detecting fatty infiltration in 50% of AFLP cases (5 of 10 patients), compared to ultrasound's 27%. 1
• MRI showed no evidence of fatty infiltration in any of 5 patients studied, though newer MRI spectroscopy techniques may improve detection. 1

Clinical Implications for Diagnosis

The diagnosis of AFLP must be made clinically using the Swansea criteria, not radiologically. 6 Ultrasound findings should be considered supportive when positive but never used to rule out the diagnosis when negative. The key diagnostic features remain:

• Third-trimester presentation with nausea, vomiting, and abdominal pain 6, 3
• Coagulopathy (present in >75% of cases) 6
• Elevated transaminases and bilirubin 3
• Hypoglycemia (present in approximately 53% of cases) 3

Imaging did not contribute meaningfully to patient management in the largest published series, and liver biopsy should be reserved only for situations where the result would change therapeutic approach. 1, 6