Unfortunately, you likely do not have an actionable medical negligence case based on the colonoscopy injury. Perforating the colon during a scope can happen even when the doctor does everything correctly. Certainly the injury can be caused by a careless or inexperienced doctor. But you have the burden of proof to distinguish your case from all the others where the physician did everything right. The medical report from the colonoscopy will likely say everything went normally. So it boils down to a "proof problem" for your attorney. Remember that just proving that a bad result happened is not sufficient to qualify for compensation. Bad outcomes routinely happen with medical procedures. Your task is to prove that this particular scope operator deviated from the minimum standard of reasonable medical care under the circumstances.
Typically, a risk incident to the procedure, but call a local malpractice lawyer in the morning nonetheless.
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