Major venous anomalies are frequently associated with horseshoe kidneys

Several cases of horseshoe kidney with anomalous inferior vena cava (IVC) have been described, but there have been no reports of the incidence and variation of anomalous IVC in patients with horseshoe kidneys detected using multidetector row computed tomography (MDCT).

105 patients with horseshoe kidneys were evaluated with MDCT and a variety of venous anomalies were identified in 30 patients (28.6%). Anatomical variations of the renal vein were identified in 24 patients (22.9%), which was no higher than the reported incidence in the general population. However, variations of the IVC were identified in 6 patients (5.7%), which was a higher incidence than expected to be found in the general population: 1 pre-isthmic IVC with retrocaval ureter, 2 double IVCs posterior to the horseshoe kidney, 2 left IVCs posterior to the horseshoe kidney, and 1 azygos continuation of the IVC.

Horseshoe kidneys are frequently found in patients with other venous, and particularly IVC, anomalies, which should be evaluated using MDCT as part of treatment planning.