2226 Hot Spot Sign on Tc-99m DISIDA Nuclear Hepatobiliary Scan

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INTRODUCTION: Hepatic Focal Nodular Hyperplasia (FNH) can be an unusual cause of abdominal pain. Prior to the advent of readily accessible diagnostic imaging techniques, patients with FNH primarily presented with vague symptoms of abdominal pain, then proceeded to imaging, which led to diagnosis. Today, most cases are found incidentally on imaging, in often asymptomatic patients. Here, we present a patient with significant symptoms in whom an identified FNH was considered inconsequential, but is eventually proven otherwise. CASE DESCRIPTION/METHODS: A previously healthy 31-year-old male presented with a one-month history of persistent postprandial right upper quadrant abdominal pain. Ultrasound showed cholelithiasis. MRI revealed FNH of the anteroinferior subsegment of the liver. Tc-99m DISIDA Cholescintigraphy showed a normal functioning gallbladder, but an abnormal delayed clearance of tracer from a focal area in inferior tip of the liver, corresponding to the FNH seen on MRI, consistent with a “hot spot sign”. Due to suspicion for symptomatic cholelithiasis, he underwent elective cholecystectomy. Symptoms persisted post-op, thus, his pain was thought to be from symptomatic FNH. After subsequent elective FNH resection, symptoms subsided. DISCUSSION: While cholescintigraphy typically evaluates for biliary tree dysfunction, it can also reveal abnormality in hepatic parenchymal tissue. Previously, Tc-99m Sulfur Colloid Liver-Spleen scans were used for diagnosis of FNH. However, the “hot spot sign” on cholescintigraphy has also been described as diagnostic for FNH. This case illustrates that a focal area of delayed tracer washout, or “hot spot”, can also be seen with Tc-99m DISIDA. Although the significance of delayed tracer washout is unclear, this finding suggests liver parenchyma’s inability to effectively clear bile from an FNH. This inability to adequately clear bile, may result in pain. The severity of impaired clearance may even correlate with the severity of symptoms. Although further investigation is necessary, cholescintigraphy may prove a useful tool in functional imaging for differentiating between symptomatic and asymptomatic FNH.