Colonic uptake is extremely variable in location and intensity. It appears to involve the bowel walls and at times to be intraluminal. Uptake might represent mucosal activity or inflammation, muscular contraction, bowel lymphoid tissue, or possibly colonic bacterial activity. Identification can be made easier with the recognition of a contiguous or segmental, curvilinear, pattern of uptake. PET/CT can help identify uptake in the bowel.

Colonic uptake is generally more intense than in the small bowel, but is still extremely variable. When the pattern of uptake is multifocal, diffuse or segmental, and less intense, it tends to be normal or a non-malignant condition such as inflammatory bowel disease. A single intense focus is more worrisome, with an important fraction of such findings representing a malignant or pre-malignant finding on colonoscopy. Moroever, single intense foci may also represent adjacent metastatic peritoneal implants and/or lymph node metastasis in the abdomen.

Possible limitations:

• Assessment of GI malignancies
• PET/CT images without oral contrast can be difficult to interpret
• Fusion images will not reflect any movement of bowel that can occur during scanning

Preventive measures:
Though not well studied, GI uptake may potentially be reduced with the use of smooth muscle relaxants, and possibly bowel preparation with laxatives.