Not all black colons on [¹⁸F]FDG PET are due to metformin

Excerpt

Antidiabetic treatment with metformin is known to induce changes in glucose uptake in normal organs [1]. Metformin treatment increases [¹⁸F]FDG-uptake in the bowel with typically intense and diffuse uptake along the bowel, strongly predominant in the colon [2]. We here report a case with a similar pattern of intense and diffuse [¹⁸F]FDG-uptake along the colon of a 58-year-old patient experiencing rectal bleeding and diarrhea with a medical history of lung transplantation due to end-stage interstitial lung disease. Simultaneously acquired CT images of the [¹⁸F]FDG PET/CT demonstrate wall thickening of the entire colon with mild infiltration of the paracolic fat tissue and some prominent mesenterial lymph nodes. [¹⁸F]FDG PET/CT also demonstrates a liver lesion cranially in the liver and multiple lymph nodes with high [¹⁸F]FDG-uptake. Given the highly elevated EBV PCR titers (6758 IU/ml) the lesions were strongly suspicious of posttransplant lymphoproliferative disease (PTLD). A colonoscopy was performed to exclude PTLD in the colon and showed severe colitis with ulcerations of which anatomopathological analysis confirmed PTLD. Diffuse and intense [¹⁸F]FDG-uptake in the bowel is also observed in other cases of graft-versus-host disease and inflammatory bowel disease [3, 4]. Intense [¹⁸F]FDG-uptake in the bowel is not always induced by metformin treatment and further examination can be required, especially when gastrointestinal symptoms are present. …