Crossed dystopia (syn.unilateral fusion cross fused renal ectopia) is a rare form of

renal ectopia Ectopic kidney describes a kidney that is not located in its usual position. It results from the kidney failing to ascend from its origin in the true pelvis or from a superiorly ascended kidney located in the thorax The thorax or chest is a pa ...

where both

kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blo ...

s are on the same side of the spine. In many cases, the two kidneys are fused together, yet retain their own vessels and ureters. The

ureter The ureters are tubes made of smooth muscle that propel urine from the kidneys to the urinary bladder. In a human adult, the ureters are usually long and around in diameter. The ureter is lined by urothelial cells, a type of transitional epit ...

of the lower kidney crosses the midline to enter the

bladder The urinary bladder, or simply bladder, is a hollow organ in humans and other vertebrates that stores urine from the kidneys before disposal by urination. In humans the bladder is a distensible organ that sits on the pelvic floor. Urine enters ...

on the contralateral side. Both renal pelves can lie one above each other medial to the

renal parenchyma Parenchyma () is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology it is the name for the tissue that fills the interior of flatworms. Etymology The term ''parenchyma'' is New Latin from the word π ...

(unilateral long kidney) or the pelvis of the crossed kidney faces laterally (unilateral "S" shaped kidney). Urogram is diagnostic. The anomaly can be diagnosed through ultrasound or

urography Pyelogram (or pyelography or urography) is a form of imaging of the renal pelvis and ureter. Types include: * Intravenous pyelogram – In which a contrast solution is introduced through a vein into the circulatory system. * Retrograde pyelogram ...

, but surgical intervention is only necessary if there are other complications, such as tumors or

pyelonephritis Pyelonephritis is inflammation of the kidney, typically due to a bacterial infection. Symptoms most often include fever and flank tenderness. Other symptoms may include nausea, burning with urination, and frequent urination. Complications may ...

References

Kidney anatomy {{genitourinary-stub