What is the probability of vp shunt getting clogged after the first shunt revision surgery in adults?

Hydrocephalus : The rate of shunt revisions is approximately 25% in the first year. Thereafter the rate drops to 1%/year. The shunt can last up to 25 years. New advances such as programmable valves, placement of the catheter under stereotactic guidance, endoscopic positioning, and laparoscopic assisted placement of the peritoneal tubing over the dome of the liver can dramatically reduce the shunt revision rate.