Figure 16b. Plexiform neurofibroma of the bladder in an 18-year-old man with known NF1 who developed renal insufficiency from chronic bilateral ureteral obstruction. (a) Unenhanced CT scan shows a low-attenuation mass thickening the posterior and left lateral bladder wall. There are high-attenuation septa (arrow) and nodules in the mass from the collagenous septa within the neurofibroma. (b) Photograph of the cut surface of the resected bladder specimen shows innumerable nodules (arrow) from cross sectioning the plexiform neurofibroma.