A 61 year old man with metastatic tonsillar squamous cell carcinoma and chronic kidney disease presents with flank pain. He is found to have a new left retroperitoneal fluid collection and associated moderate left hydronephrosis.
Differential diagnosis includes retroperitoneal hematoma and urinoma. Although other anatomic imaging tests may further characterize the collection and hydronephrosis, an functional test can prove whether this collection is related to a urine leak.
Here are posterior planar images from a Tc99m MAG3 renogram:
Note the gradual excretion of urine below the left kidney, in an abnormal morphology not conforming to the left ureter.
This was followed with an abdominal SPECT/CT acquisition:
SPECT/CT images confirm that this represents a urinoma, which tracks into the left retroperitoneum and external iliac region. This is believed secondary to be secondary to left ureteral obstruction, complicated by forniceal rupture and leak of urine into the retroperitoneum. Several prominent periaortic lymph nodes were noted adjacent to the proximal left ureter, presumed to be the cause of obstruction.
Enlarged left periaortic lymph node (arrowhead)
This case is part the series Problem Solving with SPECT/CT (coming soon).
