Crossed renal ectopia presenting with suprapubic swelling and acute renal failure

A 17-year-old male was admitted with a fluctuant suprapubic mass. A bladder scan demonstrated > 999 ml filling so he was catheterised. However, only 75ml of urine was drained. He was in acute renal failure with serum potassium of 6.5mmol/l. Computerised tomography (CT) scan showed a large midline 'cystic mass' separate from the bladder compressing the left ureter, causing left-sided hydronephrosis. Right kidney was not visualised. Percutaneous aspiration of the 'cyst' yielded 2000ml of straw-coloured fluid high in creatinine, urea and electrolytes indicating that it was urine. Having relieved the left ureter, the patient was subsequently diuresed, and renal function returned to normal. A CT urogram showed contrast uptake with renal parenchyma in the "cyst". Consequently, a diagnosis of right-sided crossed renal ectopia was made. Bilateral ureteric stents were inserted, and later a right-sided nephrectomy was performed. The patient made a full recovery. To the best of our knowledge, this is the only reported case of crossed renal ectopia causing obstruction of the normal ureter, resulting in acute renal failure.The role of modern imaging in the management of this condition is also highlighted in this report.