The clinical significance of incidental intra-abdominal findings on positron emission tomography performed to investigate pulmonary nodules

Abstract

Background: Lung cancer is a common cause of cancer-related death. Staging typically includes positron emission tomography (PET) scanning, in which (18)F-fluoro-2-dexoy-D-glucose (FDG) is taken up by cells proportional to metabolic activity, thus aiding in differentiating benign and malignant pulmonary nodules. Uptake of FDG can also occur in the abdomen. The clinical significance of incidental intraabdominal FDG uptake in the setting of pulmonary nodules is not well established. Our objective was to report on the clinical significance of incidental intra-abdominal FDG activity in the setting of lung cancer.

Methods: Fifteen hundred FDG-PET reports for studies performed for lung cancer were retrospectively reviewed for the presence of incidental FDG-positive intraabdominal findings. Patient charts with positive findings were then reviewed and information extracted.

Results: Twenty-five patients (25/1500) demonstrated incidental intraabdominal FDG uptake thought to be significant (1.7%) with a mean patient age of 71 years. Colonic uptake was most common (n = 17) with 9 (52%) being investigated further. Of these 9 cases, a diagnosis of malignancy was made in 3 patients, pre-malignant adenomas in 2 patients, a benign lipoma in 1 patient and no abnormal findings in the remaining patients. 8 patients were not investigated further (3 diagnosed with metastatic lung cancer and 2 were of advanced age) secondary to poor prognosis.

Conclusion: Incidental abdominal findings in the colon on FDG-PET scan for work-up of pulmonary nodules need to be further investigated by colonoscopy.

Figure 1

Fused coronal, sagittal and transaxial FDG PET/CT images in an 84 year old male (Patient 11). The cross-hairs localize an FDG-avid lung cancer.

Figure 2

Flow diagram of reviewed FDG-PET scans (Abdo = abdominal; jxn = junction).

Figure 3

Fused coronal, sagittal and transaxial FDG PET/CT images in an 84 year old patient (Patient 11). The cross-hairs localize intense uptake in the left colon.