Horseshoe Kidney

Renal function is usually normal - The fusion itself doesn't impair function. What does is what it causes: ureteropelvic junction obstruction, nephrolithiasis (about 36% lifetime), vesicoureteral reflux, and recurrent infection. Check creatinine and eGFR, and read the CT urogram for hydronephrosis or obstruction, before assuming a normal kidney.

Bleeding in renal surgery - Multiple aberrant arteries with no collateral supply make surgery on these kidneys bloodier and longer than the same operation on normal anatomy, which is also why symphysiotomy was abandoned (bleeding, leaks, fistulas). Type and screen, second IV, and plan for a longer case.

Look for the syndrome behind it - Horseshoe kidney is present in roughly 67% of Edwards syndrome, 14 to 20% of Turner syndrome, and about 1% of Down syndrome. Turner brings coarctation of the aorta, bicuspid aortic valve, and an elongated transverse arch with real dissection risk, so get a baseline echo and check pressures in both arms; the webbed neck and high-arched palate also make the airway harder.

Positioning and radiation - Stone work here means percutaneous or mini-percutaneous access, often prone and fluoroscopy-heavy, because shockwave lithotripsy clears fragments poorly in a kidney that doesn't drain. Secure the airway and lines for prone, pad deliberately, and wear lead.

Bowel injury - A segment of colon sits posterior to a horseshoe kidney, so percutaneous access carries a real risk of incidental bowel injury. Be ready for a conversion to open.

Blunt abdominal trauma - The low midline position lets these kidneys be compressed or fractured against the lumbar vertebrae. In abdominal trauma with a known horseshoe kidney, expect renal injury and set up access and blood accordingly.

Contrast decisions - CT urogram with and without IV contrast is the diagnostic standard; MRI is the substitute when radiation or standard contrast has to be avoided. If function is already reduced from obstruction, that choice belongs in your perioperative plan.

Not just stone cases - These kidneys carry three to four times the rate of transitional cell tumors and twice the rate of Wilms tumor, so oncologic resections are part of the caseload, and laparoscopic or robotic approaches here are more complex than the standard anatomy version.

Horseshoe kidney is the most common renal fusion defect, occurring in roughly 1 in 500 people with a 2:1 male predominance. The lower poles fuse across the midline in more than 90% of cases, joined by an isthmus that is renal parenchyma in about 80% and a fibrous band in the rest. Ascent arrests around L3, so the kidneys sit low and malrotated, with ureters passing over the isthmus or down the anterior surface. That drainage problem, not the fusion itself, produces the stasis, obstruction, and infection that drive the pathology. Vascular supply is highly variable: one series found 387 arteries across 90 horseshoe kidneys, venous anomalies in 23%, and no useful collateral flow, so dividing any artery infarcts its segment. An isolated horseshoe kidney is otherwise benign.