The doctor was supposed to tell you during his pre-operative consult that there are risks to the surgery he was proposing. Among the risks of abdominal surgery is the risk of injuring an adjacent organ.
If you had prior surgery, there's a good chance you have surgical adhesions, also known as scar tissue that forms inside of you. Having lots of scar tissue can make surgery very challenging since the surgeon must take down all the adhesions before getting to the place where he needs to be operating. This is often referred to as 'lysis of adhesions'.
Sometimes those adhesions are stuck to the organs he needs to work on. He must then peel away layer after layer of scar tissue. Sometimes an injury to an adjacent organ happens during the remove of adhesions.
If the physician recognizes the injury while he is operating, he then has an opportunity to fix the injury while you are still under anesthesia. If needed, he can call for surgical specialists to assist with the newly-formed injury to an adjacent organ.
An injury to an adjacent organ during surgery, also known as an 'iatrogenic injury', will usually rise to the level of medical malpractice when the surgeon fails to recognize the injury during the course of surgery.
In the legal community we say that an injury to an adjacent organ during surgery may not be malpractice. However, it is usually the failure to recongize that injury that may lead us to conclude there was medical negligence leading to injury.