After monolateral dual kidney transplantation, a 69 years old male patient developed symptomatic lymphocele with mild hydroureteronephrosis, impaired renal function, and right inferior limb oedema. A percutaneous ultrasound-guided drainage of the fluid collection was planned, but the complex mutual relations between the collection and the renal hilus did not allow to identify a suitable route for a safe drainage insertion during conventional ultrasound examination. A retrograde cystography using echographic contrast agent was, therefore, performed, and it clarified the position of both ureters and the renal vessels, permitting an harmless ultrasound-guided percutaneous lymphocele drainage. In conclusion contrast-enhanced ultrasound retrograde cystography may be helpful in percutaneous drainage of complex posttransplant lymphocele.