Visceral Handedness--A Question for MDs

I recently picked up a copy of Gray’s Anatomy and it has me wondering about something. In the section on abdominal anatomy, it gives specific locations for internal organs: structures such as the liver, appendix, and head of the pancreas are shown on the right side of the body; and others such as the fundus of the stomach and the spleen are on the left.

My question: how universal is this arrangement? I (of course) realize that the lungs will not be found below the colon, but I’m thinking in terms of left/right arrangement. I seem to recall hearing that the appendix can be on either side, depending on the person; and it seems that at least in the case of mirror twins (if not identical twins in general) that each person would have their organs on the opposite side from the other.

So am I wrong, or is Gray’s somewhat incomplete (I’m betting on me, but you never know)? Further, is there any way short of getting scanned to determine what side everything is on?


There is a condition called “situs inversus” in which the internal organs are reversed left-for-right from the normal position. Some previous threads:

complete situs inversus occurs in something like 1 in 200,000 people with no ill effects.

it is more likely to have one organ (spleen, or heart say) on the “wrong” side. quite often this causes problems, and is likely to be detected.

so yep, when learning anatomy we palpate the gall bladder on the right side, listen for heart valve sounds on the centre left chest, and poke you on your right side for and suspected appendicitis.

the base of the appendix is almost always on the right side, the tip can be in the pelvis, abdomen, twisted under the colon, etc etc.

but if pain is felt in the equivalent of mcburney’s point on the left side, appendicitis should never be ruled out.

the human body is not perfectly symmetrical, and there are differences in shape and size of eg right and left lungs. and differences in position of right and left kidneys.
the diaphragm is not symetrical, and everything is in the position it is in (heart left, liver right, kidneys either side, spleen left, gallbladder right etc) to optimise space and prevent organs becoming squashed.

Thanks, folks.

An episode of “Quincy” stated that this inversion occurs in idential twins: one is left handed (viscerally), the other right. One twin had been raised in an orphanage and murdered the other, taking her place (and wealth, of which she was jealous). I thought it was bullshit.

That is, BS because the plot-writer had it as common in identical twins. If it was, they wouldn’t be identical.

Read an interesting article that stated this effect could actually be engineered by conditions in the womb. Basically, if you reverse the womb’s ‘plumbing’, putting some bit or another opposite the side that it’s usually on, the fetus’s organs will reverse as well.