Referred pain in external hemorrhoids is due to
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.
Common pudendal nerve
Inferior rectal nerve
Splanchnic nerve
Sympathetic nerve
Abdomen and pelvis