A Horseshoe Kidney Detected Incidentally by Tc-99m DISIDA Hepatobiliary Scintigraphy

Abstract

Horseshoe kidney is a common renal fusion anomaly that is usually asymptomatic in adults. A horseshoe kidney was detected incidentally on Tc-99m DISIDA hepatobiliary scintigraphy performed to evaluate acute cholecystitis. The diagnosis was first suggested on hepatobiliary scintigraphy and confirmed by computed tomography.

FIGURE 1

Fig. 1: A 74-year-old man underwent Tc-99m DISIDA scintigraphy for the evaluation of dilatation of the gallbladder and intrahepatic and extrahepatic biliary trees. Horseshoe-shaped accumulation (arrowheads) extending to both sides from midline was visualized in the midabdomen at 1 minute. After that, rapid accumulation of the radiotracer within the renal pelvis (arrows) was visualized and decreased with time. A computed tomograph (CT) confirmed the diagnosis. Accumulation in the gallbladder and the intestine was not apparent, and hepatic uptake persisted at 60 minutes and 6 hours. Intestinal activity was not visualized until 24 hours. Complete obstruction of the distal common bile duct was suggested. The patient underwent percutaneous transhepatic needle biopsy of the distal common bile duct, which confirmed adenocarcinoma. Because horseshoe kidney is a common renal fusion anomaly (occurring in approximately 0.25% of the general population) and is usually asymptomatic, it may be diagnosed incidentally through various imaging methods (^1–5). These scintigraphic findings might be mistaken for other pathologic conditions. However, its shape and position extending across the midline are indicative of horseshoe kidney.

FIGURE 2

Fig. 2: (A, B) Contrast-enhanced CT show the lower poles of the kidneys joined by the isthmus (arrow) across the midline. These findings are compatible with a diagnosis of horseshoe kidney.