Ultrasound images of Horseshoe kidneys

In the horseshoe kidney, the kidneys lie one on each side of the abdomen but their lower poles are fused by a connecting band of renal tissue, or isthmus, which lies anterior to the aorta and IVC (Fig.below). The kidneys tend to be rotated and lie with their lower poles medially. It may be difficult to visualize the isthmus due to bowel gas anterior to it but a horseshoe kidney should always be suspected when the operator is unable to identify the lower poles of the kidneys confidently. When the isthmus can be seen, it is important not to confuse it with other abdominal masses, such as lymphadenopathy. CT is occasionally performed because of this but normally clarifies the findings.