An alternative to surgery is embolization, a minimally invasive treatment for varicocele that is performed by an interventional radiologist. This involves passing a small wire through a peripheral vein and into the abdominal veins that drain the testes. Through a small flexible catheter, the doctor can obstruct the veins so that the increased pressures from the abdomen are no longer transmitted to the testicles. The testicles then drain through smaller collateral veins. The recovery period is significantly less than with surgery and the risk of complications is minimized with overall effectiveness similar to surgery, yet with fewer recurrence rates. However, radiation exposure to the testicles can often not be avoided with this technique. Embolization is also an effective treatment for post-surgical varicoceles. These are varicoceles that reappear after they have been surgically repaired. The main theory is the presence of redundant gonadal veins that provide collateralization cause the reappearance of the varicoceles.