18F-FDG PET/CT Five Days Post First Administration of Semaglutide

We present the case of a 60-year-old woman with metastatic breast cancer who underwent 18 F-FDG PET/CT for treatment response assessment. Beyond oncologic findings, the scan revealed abnormal gastric retention, gallbladder, colonic, and renal uptake patterns suggestive of Semaglutide-induced gastroparesis, cholecystitis, colitis, and possible acute kidney injury secondary to dehydration. Suspicions were confirmed by clinical evaluation. Symptoms resolved after supportive therapy and withholding of semaglutide. To our knowledge, this is the first report of multi-organ side effects seen on 18 F-FDG PET/CT following a single semaglutide dose administration, emphasizing the need for nuclear medicine physicians to recognize glucagon-like peptide-1 receptor agonist medication-related side effects and their imaging manifestations.