Findings: FDG PET imaging demonstrates an axial image through the pelvis with radiotracer within the posterior aspect of the pelvis. Post void images demonstrate a normal pelvis without abnormal radiopharmaceutical.
Diagnosis: Radiopharmaceutical layering along the posterior aspect of the pelvis.
Discussion: FDG PET imaging commonly gives rise to accumulation of activity within the kidneys, ureters and urinary bladder. Radiotracer within the bladder can sometimes obscure primary lesions. In addition, posterior layering of radiopharmaceutical within the bladder should be differentiated from a bladder diverticulum. This differentiation can be made if post void images are obtained. In addition, retrograde filling of the bladder with saline followed by drainage will dilute whatever urine is present within the bladder and remove focal concentrations of radiopharmaceutical.
Images obtained after voiding can help differentiate bladder diverticulum, accumulation of radioactivity within the posterior aspect of the bladder as well as prevent obscuration of underlying lesions.
References:
Miraldi F, Vesselle H, Faulhaber P, et al. Elimination of artifactual accumulation
of FDG in PET imaging of colorectal cancer. Clinical Nuclear Medicine,
Lippincott-Raven, 1998; 23:3-7.
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