The Diagnostic Benefit Of Abdominal Ultrasound Scans In Incidentally Abnormal Liver Function Tests

Introduction An abdominal ultrasound scan (AUSS) is widely recommended in national and international guidelines for the investigation of abnormal liver function tests (LFTs). Abnormal LFTs exist in around 20% of cases in primary care, placing significant demand on radiology services. However, the evidence for performing AUSS in patients with incidentally abnormal LFTs is weak. Non-invasive scoring systems such as the NAFLD fibrosis score (NFS) and Fibrosis-4 index (FIB4) are used in the assessment of liver fibrosis. Abnormal results prompt referral to secondary care for further review. It is unclear whether AUSS provides additional diagnostic information in such cases. Intelligent liver function testing (iLFT) was launched in NHS Tayside in 2018. General Practitioners (GPs) provide relevant clinical details and those with abnormal LFTs have reflex tests without further venepuncture. Non-invasive fibrosis scores are calculated automatically. Management plans with recommended outcomes are then provided: secondary care referral; primary care follow-up; or further investigations and referral criteria. Methods A retrospective analysis was performed of all patients who had iLFT performed between August 2018 and August 2019, and who had abnormal NFS (≥-1.455 for patients aged under 65; ≥0.12 in patients aged 65 or over) and/or FIB4 (≥1.45). The result of their ultrasound was documented and its impact on their diagnostic journey recorded. Results 497 patients had an iLFT outcome with abnormal NFS and/or FIB4. 311 (62.6%) had AUSS either prior or parallel to referral. 81 patients had a normal AUSS. 179 (57.6%) patients had simple fatty infiltration of the liver. 22 (7%) had confirmatory radiological features of cirrhosis. Overall, AUSS did not add any diagnostic information or alter the clinical pathway in 306 of the 311 patients (98.4%). 4 patients (1.3%) were diagnosed with metastatic disease and 1 patient had a primary liver tumour (neuroendocrine aetiology on subsequent biopsy). All 5 of these patients had co-existent symptoms which would have separately prompted investigations other than AUSS (iron deficiency anaemia in 4 patients, unexplained abdominal pain in 1 patient). The diagnoses are shown in figure 1. Conclusions AUSS can play an important role in the diagnosis of biliary disease or malignancy in the setting of symptomatic abnormal LFTs or abdominal pain, but provides little diagnostic benefit in the diagnosis of asymptomatic or incidentally abnormal LFTs. Removing routine AUSS from diagnostic pathways could save significant time and money for radiology departments and GPs, while safely ensuring malignancy is not missed.