What your BELLY BUTTON reveals about your health, according to experts

Most of us probably don't give our belly button a second thought. 

However, this small fold of skin could be a host for infections, cysts, and even hernias, experts suggest. 

Dr Dan Baumgardt, a neuroscientist and physiologist at the University of Bristol in the UK, wrote for The Conversation that the belly button - known medically as the navel - 'has more depth to it than just a few millimeters.' 

The belly button is a remnant of the umbilical cord, which connects a fetus to its mother during pregnancy. There are many variations, but the two main groups are 'outies' and 'innies.' 

Roughly 10 percent of people around the world have an outie, meaning their belly button is protruding, while the remainder have an innie. 

Most people have an 'innie,' belly button, meaning that the flap of skin folds in rather than protrouding out

While the belly button has no function after birth, subtle changes to the way it appears could be an indicator that something is wrong with our health.

One of these, Dr Baumgardt notes, is an umbilical hernia, which occurs when part of the intestine bulges through the belly button. This causes swelling or a bulge coming out of the navel. 

These are usually harmless and mainly affect infants, though they are also the second most common hernia in adults. Being overweight or having multiple pregnancies can increase the risk of adults developing an umbilical hernia. 

Most of the time, no treatment is needed, though the hernia may need to be surgically removed if it causes pain or blocks the intestine.

Dr Baumgardt also pointed to a rare complication called Sister Mary Joseph's nodule, which is named after a nun who discovered that many patients with late-stage cancer had swelling or a nodule near their belly button. 

This can be a sign that patient's cancer has spread or become more advanced. 

'It’s not seen as commonly these days, since more cancers are now diagnosed earlier before extensive spreading occurs,' Dr Baumgardt writes. 

Another unusual condition of caput medusae, or Medusa's head. 

Also called a palm tree sign, this is a network of painless, swollen veins around the belly button. From a distance, it also looks like a black or blue bruise. 

This is caused by portal hypertension, which is high pressure in the portal vein. The portal vein carried blood to the liver from the intestines, gall bladder, pancreas, and spleen. The liver then processes nutrients in the blood and sends it to the heart.  

Medusa's head (left) and Sister Mary Joseph nodule (right) are two rare conditions that form in or around the belly button

Medusa's head on its own is not a disease, though it is usually a sign of liver scarring, also called cirrhosis. 

The scarring makes it harder for blood to flow through the liver's veins, causing it to build up in the portal vein and flow to nearby veins near the belly button. 

This enlarges those blood vessels into a Medusa-like pattern. 

The belly button can also harbor infections, especially if you have an innie. 

This fold can trap moisture and debris, and warm environments like this are prime environments for bacteria to grow. 

Signs of an infection in the belly button include redness, pain, swelling, foul smell, and pus or other fluids leaking out.