<prompt> Referred pain in external hemorrhoids is due toCommon pudendal nerveInferior rectal nerveSplanchnic nerveSympathetic nerve  <response>: Internal hemorrhoids are located on the inside lining of the rectum and cannot be felt unless they prolapse and push through the anus opening causing pain and itching. A thrombosed external hemorrhoid occurs when blood within the blood vessel clots, and may cause significant pain and swelling. 