An 80‐year‐old man presenting with gross hematuria was diagnosed with muscle‐invasive bladder cancer. Ten years prior, based on an ultrasound performed for chronic renal insufficiency, he was told he had a congenitally absent left kidney. Office cystoscopy showed a large bladder tumor. Following cystoscopy, he underwent a CT‐urogram. This study showed that he, in fact, had left‐to‐right unfused crossed renal ectopia. Unfused crossed renal ectopia is an extremely rare abnormality that is usually asymptomatic and typically incidentally diagnosed. Crossed renal ectopia is a result of improper migration of the metanephric blastema and ureteric bud development resulting in a contralateral ectopic kidney with aberrant vascularization. The ureter crosses the midline and inserts into the orthotopic side of the bladder. Special consideration of the vascularization of unfused crossed ectopic kidneys is necessary prior to surgery or radiation therapy.
Ferguson et al. (Thu,) studied this question.