Here is a renal sonogram obtained from an elderly woman demonstrating bilateral hydronephrosis as well as a heterogeneous mass encasing the left kidney.

CT scan of the abdomen included for comparison: shows multilobulated retroperitoneal soft tissue mass (arrow) encasing the left kidney (LK) causing its displacement anteriorly and superiorly. Similar mass involving the right kidney (RK) can be noted, but to a lesser extent (arrow).

Unfortunately, biopsy of the mass revealed aggressive B cell lymphoma.

Learning point: Lymphoma can present as obstructive nephropathy; pay attention to the area surrounding the kidney. In fact, the diagnosis was missed on a prior point of care ultrasound in this patient.