An Investigational Scan (89Zr-DFO-GmAb PET/CT) Compared to Contrast-Enhanced CT for the Detection of Recurrent Clear Cell Renal Cell Cancer After Surgery Comparing Carbonic Anhydrase IX (CAIX) PET CT to Conventional PET CT for Post-Op Staging in Kidney Cancer

Inclusion Criteria: * Age ≥ 18 * Histologically confirmed clear cell renal cell carcinoma (RCC) (ccRCC) (based on partial/radical nephrectomy/metastasectomy) * For tumors with extensive sarcomatoid features, if there is evidence of areas of clear cell and high CAIX expression throughout the tumor on immunohistochemistry, they will be allowed on study * Subjects must have undergone definitive treatment of their primary tumor (partial/radical nephrectomy) +/- resection of metastatic disease to no evidence of disease (NED) with a prior nephrectomy \< 2 years) * Surgery must have been performed between 4-16 weeks at the time of planned imaging * Subjects are considered to have a high risk of recurrence based on the following criteria: * Intermediate-high risk ccRCC: * pathologic tumor stage 2 (pT2), grade 4, or sarcomatoid, N0, M0 * pathologic tumor stage 3 (pT3), any grade, N0, M0 * High risk ccRCC: * pathologic tumor stage 4 (pT4), any grade, N0, M0 * pT any stage, any grade, number of positive nodes (pN+), M0 * M1 now NED: pathologically-confirmed ccRCC, undergoing a resection of a solitary, isolated soft tissue metastasis within two years from initial nephrectomy * Negative serum pregnancy tests in female patients of childbearing potential. (Women of child bearing potential \[WOCBP\] require a negative pregnancy test within 24 hours (urine) prior to receiving investigational product) * Consent to practice double-barrier contraception until a minimum of 42 days after 89Zr-DFO-GmAb administration * Individual must be able to remain still and lie flat for duration of the diagnostic imaging procedure (less than 1 hour) Exclusion Criteria: * Inability to provide written informed consent * Any evidence of residual disease or known metastasis at the time of planned 89Zr-DFO-GmAb administration * Prior post-operative imaging for confirmation of disease status * An untreated non-renal malignancy with the following exceptions: * Low risk prostate cancer on active surveillance (National Comprehensive Cancer Network \[NCCN\] very low/low risk) * Non-melanoma skin cancer * Any prior treated malignancy meeting the following characteristics: * Treated stage I or II cancer from which the patient is currently in complete remission * A stage III cancer from which the patient is progressing or has been disease-free for and has required active treatment (e.g. adjuvant or maintenance therapy) within the past 3 years prior to enrollment * A hematologic malignancy from which the patient is currently in complete remission * Contraindication to the use of iodinated contrast-enhanced CT agents, based on: * Severe allergy (for which pre-medication cannot limit adverse reactions) or * Estimated glomerular filtration rate (GFR) ≤ 30 ml/min/1.73m\^2 * Prior use of systemic therapy treatment for kidney cancer (PD-1, PD-L1, tyrosine kinase or TOR inhibitor) or radiotherapy within 4 weeks of enrollment * Exposure to experimental diagnostic or therapeutic drug within 14 days from date of planned administration * Women who are pregnant or breastfeeding * Known hypersensitivity to girentuximab * Known inability to remain still and lie flat imaging procedure (about 30 minutes)