There are two main types of hemorrhoids – internal hemorrhoids and external hemorrhoids – as well as some additional subtypes. Internal hemorrhoids develop above the pectinate line within the rectum, are usually not seen or felt, and generally do not hurt since there are fewer pain-sensing nerves in the area. External hemorrhoids are located beneath the skin in the anal area, are both visible and palpable, and tend to hurt and bleed due to the greater number of pain-sensing nerves in the region. In addition to the common internal and external hemorrhoid, there are prolapsed hemorrhoids, strangulated hemorrhoids, and thrombosed hemorrhoids. Each type of hemorrhoid is identifiable by its location in the recto-anal region, its list of accompanying symptoms, and its possible side effects.
Internal hemorrhoids often show up with no symptoms at all and are therefore only found if bleeding occurs with a bowel movement or if the hemorrhoid prolapses, meaning that it falls through the anal opening. The reason for this bleeding is that the stool scrapes off the thin lining of the hemorrhoid when it passes. Another characteristic of internal hemorrhoids is that they are surrounded by a lining called mucosa, a mucus membrane which is not sensitive to touch, pain, stretching, or temperature.
External hemorrhoids are usually more noticeable than internal hemorrhoids because they have pain fibers attached to them and often trigger symptoms such as itching in the anal area, a slight pink tinge compared to the surrounding skin, and rectal bleeding or the presence of blood clots. While external hemorrhoids typically resolve spontaneously, the residual skin that they leave may make it more difficult to clean after a bowel movement and can trigger secondary skin infections. When external hemorrhoids do not resolve, they cause increased swelling and pain within the hemorrhoidal tissue.
Prolapsed hemorrhoids occur when internal hemorrhoids swell and protrude from the anus. They can appear as a moist pinkish lump on the surface of the skin, pushing through out of the anal canal and into the anal surface. These can be labeled grade one to four, depending on how far the hemorrhoid sticks out of the anus, one being not prolapsed at all and four being prolapsed to a point where you are unable to push it back in without significant pain. In between these two extremes, grade two is assigned to hemorrhoids which are prolapsed but will retract by themselves, and grade three is reserved for prolapsed hemorrhoids which you must push back in yourself.
Strangulated hemorrhoids are classified as a complication of internal hemorrhoids and are a very rare, yet dangerous condition. Essentially, hemorrhoids become strangulated when the blood supply to an internal hemorrhoid is cut off which can cause extreme pain.
Thrombosed hemorrhoids occur when blood clots form in external hemorrhoids, a process known as thrombosis. The vein becomes extremely dilated, the hemorrhoid turns a purple or bluish color, and the pain is often very severe, accompanied by swelling, itching, and inflammation. These types of hemorrhoids usually appear as hard and painful lumps in the anus and are most common among pregnant women and young adults.
Resources:
1) https://www.mayoclinic.org/diseases-conditions/hemorrhoids/symptoms-causes/syc-20360268
2)https://www.emedicinehealth.com/hemorrhoids/article_em.htm#what_are_the_signs_and_symptoms_of_an_external_or_thrombosed_hemorrhoid
3) https://articles.mercola.com/hemorrhoids/types.aspx