The diagnosis can be made with many different imaging modalities such as ultrasound, intravenous pyelogram, CT, and MRI.Common features that can be found on imaging include:

Midline symmetrical fusion (present in 90% of cases) or lateral asymmetric fusion (present in 10% of cases) of the lower poles
Position of fused kidneys are lower than normal with incomplete medial rotation
Renal pelvis and ureters are positioned more anteriorly and ventrally cross the isthmus
Isthmus that may be positioned below the inferior mesenteric artery
Variant arterial supply that can originate from the abdominal aorta or common illiac arteries
Lower poles of kidney that extend ventromedially and may be poorly defined

Treatment
Symphysiotomy, which involves separating the fused isthmus in order to release the kidneys, used to be a recommended treatment for this condition but has fallen out of favor due to complications and minimal benefit. Furthermore, kidneys can remain in their original abnormal location after the surgery. Instead, management focuses on treating the sequelae should the patient become symptomatic.While treatment typically does not differ from that of patients with normal kidney anatomy, kidney stones can warrant a different approach. Extracorporeal shockwave lithotripsy, a possible treatment for kidney stones, can be less effective in patients with horseshoe kidneys due to the abnormal anatomy causing difficulties with localizing the energy to the stones. Also, due to the kidney obstruction that can commonly occur with this renal fusion, clearance of the resulting stone fragments can also be impaired.
thalidomide, ethanol, ACE inhibitors, cocaine, gentamicin, corticosteroids, NSAIDs, and vitamin A) have been hypothesized. Impairment of a developing embryos nephrogenic cell migration or abnormal migration of the kidneys due to fetal structural abnormalities is another potential factor. However, no definitive genetic cause has been identified. Pathophysiology
Kidneys are normally located in the retroperitoneal space between the T12 and L3 vertebrae after ascending from the pelvis during development to rest underneath the adrenal glands. In patients with this condition, the horseshoe kidney ascent is commonly arrested by the inferior mesenteric artery due to the central fusion of the kidneys. However, this is present in only 40% of cases, and, in 20% of cases, the fused kidney remains in the pelvis. Its ascension may also be restricted by its own renal artery. Additionally, during normal development, the kidneys undergo a 90 degree medial rotation while ascending. However, due to the renal fusion, this rotation is impaired resulting in abnormal placement of the ureters. This in turn can lead to urinary stasis and drainage issues. Furthermore, approximately 70% of kidneys in normal individuals are supplied by a single renal artery with the remaining 30% having embryonic collateral or accessory arteries. With horseshoe kidneys, the majority are supplied by derivatives of the abdominal aorta or common illiac arteries depending on the final position of the kidneys. Diagnosis
Horseshoe kidneys are commonly diagnosed incidentally on abdominal imaging.