Calyceal Diverticula on FDG PET

Calyceal diverticula are potential pitfalls in interpreting FDG-PET studies. They can appear as foci of increased uptake on PET and mimic hypermetabolic renal lesions. The increased FDG activity, however, is just due to renal excretion into the calyceal diverticulum. This can be confirmed with contrast-enhanced CT during the renal excretory phase.

The patient above presented for staging of lung carcinoma and was found to have a focus of increased activity in the right kidney. Correlation with portal venous and delayed CT imaging, however, reveals the typical appearance of a calyceal diverticulum: fluid-attenuation structure that fills in with contrast on excretory phase images.

References

Kavanagh JJ, Gordon L, Curry NS, Ravenel JG. Calyceal diverticulum mimicking a renal tumor on FDG PET imaging. Clin Nucl Med. 2006 May;31(5):301-2.