Huge solid perirenal masses enveloping the kidneys, causing a deformation of the renal contours as well as their displacement and malrotation, and infiltrating the renal sinuses and around the proximal ureters. The masses are hypointense on T2WI and hypointense on T1WI, with mild progressive enhancement only. There are radiating bands/septations in the masses, most likely due to internal fibrotic changes. Small simple cortical renal cysts in both kidneys. Symmetric renal excretion. No hydronephrosis except for mildly dilated superior calyx in the right kidney. The renal arteries convoluted due to the kidneys' position, the renal veins are flattened at the renal hila.
Two hepatic lesions undergo arterial enhancement, one in segment 2 measuring 12 mm across, the other in segment 4a measuring 26 mm across. Another focal lesion segment 5 measures 11 mm across and has the characteristics of a hemangioma. Simple cyst 6 mm across in segment 3.
Nodules displaying signal drop in both adrenal glands - adenomas. Tiny fatty focus in the left adrenal - myelolipoma.
Circular perivascular thickening around the inferior part of the descending thoracic aorta (partly included in some of the sequences). Short segment of perivascular thickening in the distal abdominal aorta that displays an abnormal signal in the DWI sequence.
Degenerative changes along the thoracolumbar spine. Hemangioma in vertebral body of L2.
Small amount of free fluid seen in the pelvis which is only partly included in some sequences.
In summary:
Huge perirenal masses involving the renal sinuses and enveloping the proximal ureters. Periaortic soft tissue in the thoracic and abdominal aorta. The imaging findings are in keeping with Erdheim-Chester disease, with renal, perirenal and vascular involvement.