History A 65-year-old male patient with a history of sarcomatoid renal cell carcinoma and prior right nephrectomy developed recurrent disease adjacent to the inferior vena cava. The patient underwent surveillance imaging 7 months after initiation of treatment with maximum-dose pazopanib and less than 1 month after completing a 2-month regimen of palliative stereotactic body radiation therapy to the right nephrectomy bed and site of recurrence. (Stereotactic body radiation therapy was initiated 5 months after pazopanib treatment was initiated.) One month after initiating treatment with pazopanib and 6 months before the surveillance imaging, the patient developed diarrhea and required ongoing treatment with loperamide to control symptoms. He denied any fatigue, mouth sores, or extremity pain, but described some abdominal pain and discomfort associated with the diarrhea. He was not experiencing any fevers, and vital signs were normal. White blood cell count was normal at 5100/μL (5.1 ×109/L) (normal range, 4200–10 200/μL [4.2–10.2 ×109/L]), with all components of the differential count also being normal. A normal serum albumin level of 3.9 g/dL (39 g/L) (normal range, 3.5–5.0 g/dL [35–50 g/L]) and low serum total protein level of 6.1 g/dL (61 g/L) (normal range, 6.3–7.9 g/dL [63–79 g/L]) were noted. A comprehensive metabolic panel was performed, indicating a serum chloride level of 98 mmol/L (normal, 100–108 mmol/L) and alkaline phosphatase level of 121 U/L (2.02 μkat/L) (normal, 45–115 U/L [0.75–1.92 μkat/L]). The patient underwent surveillance imaging with contrast-enhanced CT of the abdomen and pelvis in the venous phase ( Figure ).