Change in bladder SUV mean will be assessed using a paired t-test, or using a non-parametric equivalent such as a Wilcoxon signed rank test. Descriptively, change in bladder SUV mean will be reported for those administered 20 mg furosemide intravenously (IV) at the time of radiotracer injection first (group A), and those administered 20mg furosemide IV at the time of radiotracer injection second (group B).

Kidney SUV - Change in bladder and renal activity will be assessed using paired t-tests, or using non-parametric equivalents such as a Wilcoxon signed rank tests. Descriptively, bladder and renal activity will be reported for those administered 20 mg furosemide IV at the time of radiotracer injection first (group A), and those administered 20 mg furosemide IV at the time of radiotracer injection second (group B).

(Bladder Volume, ML) - Change in bladder and renal activity will be assessed using paired t-tests, or using non-parametric equivalents such as a Wilcoxon signed rank tests. Descriptively, bladder and renal activity will be reported for those administered 20 mg furosemide IV at the time of radiotracer injection first (group A), and those administered 20 mg furosemide IV at the time of radiotracer injection second (group B).

Defined as presence of unequivocal soft tissue radiotracer uptake that is characteristic of malignancy in the prostate bed and/or surrounding soft tissues and within pelvic lymph nodes. Recurrent disease rates will be compared (furosemide versus non-furosemide flotufolastat F-18 radiohybrid prostate-specific membrane antigen (18F-rhPSMA)-7.3 positron emission tomography (PET) scans using McNemar's tests. Rates will be reported, along with 95% exact confidence intervals using the Clopper-Pearson method. Descriptively, recurrent disease rate will be reported for those administered 20 mg furosemide IV at the time of radiotracer injection first (group A), and those administered 20 mg furosemide IV at the time of radiotracer injection second (group B).

The readers' confidence in identifying prostate bed, pelvic and retroperitoneal nodal disease and other recurrence on 18F-rhPSMA-7.3 PET/computed tomography (CT) with furosemide compared with the 18F-rhPSMA-7.3 PET/CT without furosemide will be scored using a 5-point Likert scale ( 1 - Definitely benign, 2- probably benign, 3 - equivocal, 4 - probably malignant, 5 - definitely malignant). This analysis will be descriptive, with summary statistics reported with and without furosemide. Variables will be summarized using frequencies and percentages. In our analysis, 1,2 (no) will be considered benign while 3,4,5 malignant (yes). A high Likert score indicates that the reader is confident that the finding on the imaging is cancer (worse outcome), while a low score indicates no cancer (better outcome). All tests will be two-sided with an alpha level of 0.05, unless otherwise noted. Statistical analysis will be conducted using SAS 9.4.