Impact of 18F-FDG PET/CT with Retrograde Filling of the Urinary Bladder in Patients with Suspected Pelvic Malignancies

Abstract

The purpose of this study was to assess the feasibility of selective pelvic PET/CT with retrograde bladder irrigation in evaluating pelvic pathologies. Methods: Thirty-eight patients (22 women and 16 men), with a mean age of 61 y (range, 41-81 y) and a neoplastic background (most of them of pelvic pathology), were assessed with PET/CT. The most prevalent findings were urothelial (14 cases), gynecologic (12 cases), and rectal (7 cases) cancers. All but 3 patients had undergone previous surgical procedures or radio-or chemotherapy. Twenty-two patients had suspected pelvic pathology on a previous diagnostic CT scan. All the patients underwent a standard PET/CT protocol (from head to upper thighs) 60 min after the intravenous injection of 370 MBq of 18 F-FDG. Additional delayed pelvic PET/CT images were acquired with a filled-bladder technique. Both series of images were assessed by 2 experienced observers. A lesion was classified as malignant if it showed a standardized uptake value greater than 2.5 or, in the case of subcentimetric lesions, any uptake greater than background activity that persisted or increased on delayed pelvic imaging. All lesions were evaluated histologically or by clinical follow-up. Results: Twenty-seven of 43 studies were categorized as pathologic using PET/CT. Nineteen studies showed abnormalities in the pelvis; the findings of 5 of these studies were false-positive. Ten studies showed pathologic 18 F-FDG uptake in the bladder wall; in 7 of these studies the uptake was found to be true-positive on histopathologic examination. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of PET/CT in the pelvic assessment were 100%, 83%, 74%, 100%, and 76%, respectively. The retrograde filling reduced the interference with physiologic urinary accumulation of 18 F-FDG in patients with possible pelvic lesions; no false-negative results were documented. Conclusion: In 18 F-FDG PET studies, retrograde filling of the urinary bladder is recommended to assess bladder wall lesions and malignancies in other pelvic locations. Several investigators have considered 18 F-FDG PET of no utility in the detection of kidney, ureter, bladder, and prostate tumors (1-7). Because 18 F-FDG is not reabsorbed as glucose, the limitation of 18 F-FDG PET has been attributed to glomerular filtration and urinary excretion (8). Furthermore, high 18 F-FDG activity in the urinary bladder is especially a problem in the evaluation of gynecologic tumors.On the other hand, previous treatments or diagnostic procedures such as biopsy, radiotherapy, systemic chemotherapy, and intravesical agents (e.g., bacille CalmetteGuérin) can cause circumferential bladder wall thickening, mimicking bladder cancer (9). The pooled activity in the urinary bladder makes the evaluation of these bladder wall lesions difficult or even impossible.Several methods have been used in an attempt to palliate this situation, with controversial results. Some approaches based on the continuous or not continuous irrigation of ...

A prospective investigation into the clinical impact of 4D-PET/CT in the characterisation of solitary pulmonary nodules

“…The results of this prospective cohort is also similar to that presented by Vicente et al [ 12 ] who showed that in lesions with low FDG avidity (N = 42) the addition of 4D-PET/CT decreased specificity (100% to 72%) due to additional false positive findings. However, there was an increase in the overall accuracy (from 45% to 62%), due improved sensitivity.…”

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Current Staging Procedures in Urinary Bladder Cancer

“…However, apart from previous transurethral resections and postoperative reactive changes, especially renal excretion of 18 F-FDG and subsequent accumulation of the tracer in urine and in the bladder render detection and assessment of local bladder tumors difficult. Some modifications have been introduced in order to bypass these problems, such as flushing the bladder [ 20 , 21 ], application of diuretics or early scanning 2–4 min after tracer injection. Unfortunately, still false-positive findings can be observed [ 21 ].…”

Detecting primary bladder cancer using delayed 18 F-2-fluoro-2-deoxy-D-glucose-positron emission tomography/computed tomography imaging after forced diuresis

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