Coexistence of Riedel's Lobe and Supernumerary Kidney as Random Imaging Findings

Supernumerary kidney (SNK) is a rare congenital anatomical variation usually detected incidentally via imaging. Although a random finding, it may present with hydronephrosis, calculi or malignancy. Both its vascularization and its drainage vary significantly, depending on its location and shape. Riedel's lobe is a normal, though rare, variant of liver anatomy presenting either as a downward projection of the inferior border of the right liver lobe or as a triangular pyramidoid projection to the right of the gallbladder. We present a case of a 71-year-old man who was initially admitted to the hospital for backache. Computed tomography (CT) imaging revealed the simultaneous occurrence of a left supernumerary kidney and Riedel's lobe. The SNK lay caudally to the normal kidney, it was supplied by a branch of the superior mesenteric artery and its drainage was supported by a bifid ureter. The Riedel's lobe represented the "tongue-like" variant without causing any symptoms to the patient. Both entities should be monitored carefully, as their presence may require surgical management should they raise a sequence of symptoms or, as in this case, modify the surgical plans in the context of other coexisting medical events.