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Figure 4a.  FDG uptake in the large intestine. (a, b) Axial (a) and coronal (b) FDG PET images show extensive uptake in the transverse colon (left image in a, right image in b) and cecum (right image in a, left image in b). The inhomogeneity of the FDG accumulation in the transverse colon results in discrete focal abnormalities on the reconstructed images. When isolated, intense focal FDG uptake in the cecum, as in other segments of the colon, can be misinterpreted as an abnormal FDG-avid mass in the abdomen. (c) Axial FDG PET image shows that when the colon is filled with gas, a region of FDG uptake can resemble peritoneal or mesenteric carcinomatosis. (d) Axial FDG PET image of the chest obtained at the lower extent of the field of view shows how a limited field of view can complicate identification of physiologic FDG uptake in the intestine. There is FDG uptake in the hepatic flexure with colonic interposition (arrow), which could be misdiagnosed as a neoplasm in the hepatic dome or costophrenic sulcus. (e, f) Coronal FDG PET image (e) and correlative CT scan (f) clearly show the colon (arrows). This example emphasizes the importance of anatomic correlation with PET results.