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The
isthmus connecting the two renal masses may be positioned in the midline or
laterally resulting in an asymmetric horseshoe kidney, 70% of which are left
dominant.
The
isthmus consists of renal parenchyma in about 80% of cases with the remainder
being composed of a fibrous band.
In
more than 90% of cases, fusion occurs at the lower pole, although fusion may
occur at the upper pole in a small minority of cases.
Higher incidence of UPJ obstructions, nephrolithiasis, and reflux compared to the general population. Increased frequency of some common renal cancers including transitional cell tumors (three to four times more common), Wilms tumor (twice as frequently), and an extremely large increase in very rare tumors such as carcinoid (62 to 82 times).
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