'Mirrored' Organs & Tissues

Kevster

Hey,


Is there a condition in humans where the organs and tissues are all the mirror image of what they should be? - i.e. The heart is on the RHS, the appendix on the LHS, etc, etc.


I know that this condition occurs in rats because we stumbled upon one in the lab one day. It is very very rare.


Kevster

John

It's called situs inversus and it does happen in humans. I think the frequency in humans is around one in 10,000. So it's not that rare in humans at least. Here's a story on a baby in China from two years ago with it.

This page also says that just the heart can develop on the opposite side and unlike situs inversus it can cause cardiac problems (and it gives a frequency of one in 7-8000 for the frequency).

Finally, here is a more scientific page compared to the two previous ones. It has some cool images too.

Kevster

That's awesome - Thank you John.

John

And now I wonder how often it occurs in rats

Kevster

As far as I recall the head of the lab informed us that it was around the same probability in rats as the one you have mentioned for humans. So, the same gene might be involved in rats, humans, and (probably) other animals. What do you think?

John

Would look like it, this page covers some of it in mice, dogs and mentions in one strain of rat that it occurs quite frequently (50% of males!). Seems to be some connection with cilia function in the GIT but not always.

Kevster

Hey,


That's a very interesting article - Thank you. I read the Wikipedia one too but it isn't as academically-oriented as that one. It's very interesting the way in which 50% of that rat species have Situs Inversus. It's probably solely by chance that this recessive gene got to become so dominant in the species. It makes you think about all the chance events that lead to the formation of life.

If someone were to work out the probability of life forming on a planet, I'm sure the odds would be astronomically (forgive the pun) high... ...Good enough to put a Euro on though


Kevster

Vorsprung

I saw this on one of my first days on clinical placement, consultant asked someone to listen a lady's heart sounds, nothing there! AFAIK it can involve just the heart in some people. The condition is called dextracardia, looks pretty good on X-ray.

DrIndy

The x-ray at the start of scrubs is one of dextrocardia, but so few people spot it!

Situs inversus is associated with Kartageners syndrome which is the absence of cillia in the respiratory tract. These people get sinus infections and chest infections very frequently and go on to develop bronchiectasis. Remember that in your differential if you meet a never smoker who develops bronchiectasis at a young age.

There was a fella in with appendicitis who had situs inversus - they CT'ed him prior to the operation as the inversus is not always complete and there can be a section of the gut rotation in the middle of the abdomen making the operation difficult.

Not all are complete and these are associated with problems as children and need operations

Capt'n Midnight

Does it affect the left/right nature of the brain or are there too few cases to tell ?
Does it affect handedness ?

Kevster

bigjimthefirst wrote:

I saw this on one of my first days on clinical placement, consultant asked someone to listen a lady's heart sounds, nothing there! AFAIK it can involve just the heart in some people. The condition is called dextracardia, looks pretty good on X-ray.

That could ONLY happen while on your first few days of placement!

---

I read about Kartagener's Syndrome, DrIndy, and was amazed to learn that such a huge alteration of the human anatomy as Situs Inversus is, could have resulted from something such as cilia. However, I'm well aware of the huge importance cilia play in the human body for other functions.


About the guy with only the rotated gut. - I think that is because Kartagener's Syndrome is caused by a single gene that exhibits Incomplete Penetrance, right?

John

Capt'n Midnight wrote:

Does it affect the left/right nature of the brain or are there too few cases to tell ?
Does it affect handedness ?

I'm not sure as my knowledge of developmental biology isn't as extensive as I'd like. I imagine that it does lead to a reversal but bear in mind that in a normal population most people (90%) have dominance on the left side of the brain. 7.5% have dominance on the right side of the brain and 2.5% have co-dominance (Note this is based on language centres, there's no such thing as being "left brained" or whatever). This has no effect on someone's handedness. Brain symmetry is a weird business.