Determining Situs in Fetal Echo: Finding Your Bearings in the Dark

Determining Situs in Fetal Echo: Finding Your Bearings in the Dark

Ever had one of those moments mid-fetal echo when you’re squinting at the screen, heart racing, wondering, “Wait… which side am I on again?” Yeah, we’ve all been there. Welcome to the world of situs determination — the essential first step that sets the stage for everything else in fetal echocardiography.

Why Situs Matters

Think of situs like the compass rose on your fetal echo map. If you don’t know where north, south, east, and west are, you’ll get lost before you even start. Situs tells us whether the heart, stomach, and great vessels are hanging out in the right spots (literally). Get this wrong, and every other interpretation risks being upside-down or inside-out.


The Usual Suspects: Solitus, Inversus, and Ambiguous

  • Situs solitus – The “normal” setup: stomach and spleen on the left, liver on the right, heart pointing left. Smooth sailing.
  • Situs inversus – A mirror image. Stomach and spleen are chilling on the right, liver on the left, and the heart points right. Not necessarily pathologic, but it will definitely test your spatial awareness.
  • Situs ambiguous (aka heterotaxy) – The wildcard. Nothing is where you’d expect it, and you’re suddenly playing anatomical detective with venous return, atrial appendages, and systemic/pulmonary connections.


Pro Tips for Getting Oriented

  1. Start with the stomach. Find the transverse abdominal view. If the stomach’s on the left and the aorta is just behind it, you’re in familiar solitus territory.




  1. Check the portal sinus/umbilical vein connection. This one’s a golden landmark to anchor your orientation.

  1. Look at the cardiac axis. About 45° leftward is your “normal.” Anything veering off dramatically should make your radar ping.




After Dark Truth

Let’s be honest — determining situs in fetal echo is like trying to figure out which way you parked your car in a dark parking lot. You think you know, until you don’t. That’s why every sonographer should master situs first, because once you’re lost, the rest of the exam becomes a maze of “wait… what’s that vessel again?”

So next time you’re deep in a fetal echo, tired, running on caffeine, and someone says, “Where’s the stomach?” — smile, take a breath, and remember: situs is your compass. Nail that, and you’ll never lose your way in the dark.



👉 Your turn: Do you have a go-to trick for nailing situs every time? Or maybe a funny story of when you got hilariously disoriented mid-scan? Drop it in the comments — because if there’s one thing we know, sonographers after dark always find their way back.


✨Want to learn more about determining fetal situs? Check out our free Determining Situs learning course over on All About Ultrasound!


-Lara Williams, BS, ACS, RCCS, RDCS, RVT, RDMS, FASE


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