Radiological Diagnosis

Crossed Renal Ectopia With Uretrocele Arising From Ureter Of Ectopic Kidney

IVP [Figure - 1] showed a low-lying malrotated crossed ectopic kidney on Rt. side with a lucent filling defect in urinary bladder on Lt. side. Contrast enhanced CT scans of pelvis showed a hypodense lesion in UB and dilated unopacified Lt. ureter [Figure - 2]. Contrast enhanced CT at lower abdomen demonstrated a malrotated hydronephrotic Kidney in ectopic location [Figure - 3]. Rt Kidney and Rt ureter is normal. Radionuclide study revealed poorly functioning hydronephrotic crossed ectopic kidney on Rt. side [Figure - 4].

Crossed ectopia occurs when the kidney migrates to opposite side, the ureteric orifice retaining its normal position in the bladder [3]. The crossed ectopic kidney is low in position and usually malrotated [1][5]. A uretrocele is a congenital cystic dilatation of the lower end of the ureter it is classified as simple when the orifice is within the bladder and ectopic when the urethral orifice lies out side the lumen of ureter [2].

The characteristic and diagnostic findings on urogram is " Cobra - head appearance" this is produced when the uretrocele filed with contrast media the dialated lower end produces a circular or elliptical area of increased density within the bladder which is surrounded by a radio lucent halo produced by the uretrocele wall, when the uretrocele is not filled with the contrast media as in our case it forms the rounded filling defect (4). A similar appearance may also be produced by a bladder tumour arising close to and partially obstructing the uretric orifice or from seminal vesicular cyst.