Diagnosis of Acute Fatty Liver of Pregnancy
Diagnose AFLP using the Swansea criteria, which requires 6 or more specific clinical and laboratory findings in a third-trimester pregnant woman, in the absence of another cause. 1, 2
Clinical Context and Timing
- AFLP occurs almost exclusively in the third trimester (week 29 and beyond) or rarely postpartum, which helps distinguish it from other pregnancy-related liver diseases. 1, 2
- While traditionally considered a late third-trimester condition, rare cases have been reported as early as the second trimester, so maintain clinical suspicion even before 29 weeks if the presentation is compelling. 3
The Swansea Criteria (≥6 Required for Diagnosis)
The American Association for the Study of Liver Diseases endorses the Swansea criteria as the standardized diagnostic approach. 1 The following 14 findings constitute the criteria:
Clinical Features
- Vomiting 1
- Abdominal pain (right upper quadrant or epigastric) 1
- Polydipsia/polyuria 1
- Encephalopathy (if present, this is highly suspicious for AFLP over HELLP syndrome) 1
Laboratory Findings
- Elevated transaminases: AST or ALT >42 IU/L 1
- Elevated bilirubin: >0.8 mg/dL 1
- Hypoglycemia: <72 mg/dL 1
- Leukocytosis: >11 × 10⁶/L 1
- Elevated uric acid: >5.7 mg/dL 1
- Elevated ammonia: >42 IU/L 1
- Renal impairment: creatinine >1.7 mg/dL 1
- Coagulopathy: PT >14 seconds or PTT >34 seconds 1
Imaging Findings
Key Distinguishing Features from HELLP Syndrome
AFLP can be differentiated from HELLP syndrome by specific laboratory abnormalities that are characteristic of AFLP:
- Prolonged PT and low fibrinogen (indicating consumptive coagulopathy rather than just thrombocytopenia) 1, 4
- Hypoglycemia (a hallmark of AFLP, uncommon in HELLP) 1, 4
- Elevated lactate dehydrogenase 1
- Hepatic encephalopathy (strongly favors AFLP) 1
- DIC occurs in 10% of AFLP cases 1
Note that approximately 50% of AFLP patients have concurrent features of preeclampsia (hypertension, proteinuria), which can complicate the clinical picture. 1, 4
Diagnostic Workup Algorithm
Initial Assessment
- Any elevation in aminotransferases, bilirubin, or bile acids in pregnancy is abnormal and requires investigation. 1, 2
- Obtain comprehensive metabolic panel, complete blood count, coagulation studies (PT, PTT, fibrinogen), ammonia level, uric acid, and lactate dehydrogenase. 1, 5
Imaging
- Abdominal ultrasound without Doppler is the preferred initial imaging modality to assess for hepatic steatosis ("bright liver"), ascites, and to exclude hepatic hemorrhage or rupture. 1
- MRI without gadolinium can be used if ultrasound is inconclusive, but gadolinium should be avoided throughout pregnancy. 1
Liver Biopsy
- Liver biopsy is NOT indicated unless the diagnosis is in doubt AND the results would change management. 1
- The histologic hallmark is microvesicular hepatic steatosis, requiring special stains (Oil Red O) or electron microscopy. 1
- In practice, biopsy is rarely performed during pregnancy due to coagulopathy and the urgency of delivery. 6, 7
Severity Assessment and Red Flags
Certain findings indicate severe disease requiring ICU-level care and potential transplant center evaluation:
- Encephalopathy development 2, 4
- Elevated serum lactate >2.8 mmol/L 2, 4
- MELD score >30 2, 4
- Swansea criteria score >7 2, 4
Important Caveats
- The Swansea criteria have high sensitivity but low specificity in women with severe AFLP and features of acute liver failure, so clinical judgment remains essential. 1
- The most common misdiagnosis is HELLP syndrome, which occurred in the majority of medicolegal cases reviewed. 8
- A useful clinical mnemonic for rapid recognition is AFLP: Altered mental status, Fast resting pulse >100/min (without fever), Liver-related GI complaints, Pain as myalgias—often with fetal compromise. 8
- Maternal tachycardia >100/min in the absence of fever or cardiac disease is present in 91-100% of cases and should prompt immediate evaluation. 8