Forced diuresis improves the diagnostic accuracy of 18F-FDG PET in abdominopelvic malignancies.

UNLABELLED: Our aim was to evaluate the role of forced diuresis in improving the diagnostic accuracy of abdominopelvic (18)F-FDG PET. METHODS: Thirty-two patients were enrolled. Besides the presence of known intravesical tumors or undefined renal lesions on the initial PET scan, the inclusion criterion was the appearance of indeterminate or equivocal (18)F-FDG foci that extended along the course of the urinary tract and could not confidently be separated from urinary activity. For each patient, a second abdominopelvic PET study was performed after intravenous injection of 0.5 mg of furosemide per kilogram of body weight (maximum, 40 mg) coupled with parenteral infusion of physiologic saline. RESULTS: Forced diuresis coupled with parenteral hydration eliminated any significant (18)F-FDG activity from the lower urinary tract in 31 (97%) of 32 patients after the bladder had been voided 3 successive times. Twelve intravesical lesions were visualized with outstanding clarity, whereas radiologic suspicion of locally recurrent bladder tumors was ruled out in 3 patients. Among 14 indeterminate or equivocal extravesical foci, 7 were deemed of no clinical value because they disappeared after furosemide challenge, whereas 7 persisting foci were proven to be true-positive PET findings. The performance of (18)F-FDG PET in characterizing 3 renal-space-occupying lesions could not be improved by our protocol. CONCLUSION: Furosemide challenge has the potential to noninvasively resolve the inherent (18)F-FDG contrast handicap in the lower urinary tract.

Occult lung infarction may induce false interpretation of 18F-FDG PET in primary staging of pulmonary malignancies.

PURPOSE: The aim of the present report is to describe abnormal (18)F-fluorodeoxyglucose (FDG) accumulation patterns in the pleura and lung parenchyma in a group of lung cancer patients in whom lung infarction was present at the time of positron emission tomography (PET). METHODS: Between November 2002 and December 2003, a total of 145 patients (102 males, 43 females; age range 38-85 years) were subjected to whole-body FDG PET for initial staging (n=117) or restaging (n=11) of lung cancer or for evaluation of solitary pulmonary nodules (n=17). Of these patients, 24 displayed abnormal FDG accumulation in the lung parenchyma that was not consistent with the primary lesion under investigation (ipsilateral n=12, contralateral n=9 or bilateral n=3). Without correlative imaging, this additional FDG uptake would have been considered indeterminate in differential diagnosis. RESULTS: Of the 24 patients who were identified as having such lesions, six harboured secondary tumour nodules diagnosed as metastases, while in three the diagnosis of a synchronous second primary lung tumour was established. Additionally, nine patients were identified as having post-stenotic pneumonia and/or atelectasis (n=6) or granulomatous lung disease (n=3). In the remaining six (4% of all patients), a diagnosis of recent pulmonary embolism that topographically matched the additional FDG accumulation (SUV(max) range 1.4-8.6, mean 3.9) was made. Four of these six patients were known to have pulmonary embolism, and hence false positive interpretation was avoided by correlating the PET findings with those of the pre-existing diagnostic work-up. The remaining two patients were harbouring small occult infarctions that mimicked satellite nodules in the lung periphery. Based on histopathological results, the abnormal FDG accumulation in these two patients was attributed to the inflammatory reaction and tissue repair associated with the pathological cascade of pulmonary embolism. CONCLUSION: In patients with pulmonary malignancies, synchronous lung infarction may induce pathological FDG accumulation that can mimic active tumour manifestations. Identifying this potential pitfall may allow avoidance of false positive FDG PET interpretation.