Ultrasound of Hernias

Introduction

Dr. Michael Williamson, University of New Mexico.
I do musculoskeletal and ultrasound imaging at the University of New Mexico.
And I'm gonna talk about the ultrasound of hernias.

We're going to talk about hernias today and how to do an ultrasound of hernia.

If you listen to this lecture and you wanna read more about hernias, I'm gonna give you two references, one by Tom Styro and Cindy Rapp in Ultrasound Quarterly in September, 2010.
And the other is a recent publication by myself and Jared Burleson called Ultrasound of Hernias.
It's in Ultrasound Clinics of North America in July, 2014.

Anatomy Relevant to Hernias

We're gonna start out by talking about the anatomy relevant to our hernia.
This is a diagram of the right inguinal region and the important structures are labeled the rectus abdominis muscle.
In the midline.
The inguinal ligament and the spermatic cord are all indicated.
The deep ring of the inguinal canal is an important structure because that is the spot where an indirect hernia occurs.
The superficial ring is less important, but it is demarcated by my arrow here.
And the femoral artery and femoral vein are the other two important structures.
The inferior epigastric artery comes off of the femoral artery and that is a key point that we have to find.

In Utero Development and Hernia Pathways

This is an example of what happens in utero to your average male.
His testicle comes down the inguinal canal, so the testicle wants to get out of the abdominal cavity and get into the scrotum, goes down the inguinal canal.
The importance of that is that canal, which I'm going to trace out once again, that canal becomes a pathway now for hernias.
And this canal should close in utero shortly after the testicle descends.
But in some males it doesn't.
Usually the left inguinal canal closes first, left testicle descends first.
The right testicle descends last.
So most hernias, most indirect hernias occur on the right.

Methodology for Inguinal Hernia Search

This is the short methodology of how you do a search for an inguinal hernia position.
Number one, you start at the femoral artery and vein with attention to the vein.
At about the spot where the saphenous vein comes in, you take your transducer go transversely on the vein and ask the patient to Valsalva.
If a femoral hernia is present, it will protrude inferiorly at the location of mark number one on the slide, you slide your transducer superiorly until you find the inferior epigastric artery.
And mark number two is where an indirect hernia will occur.
And indirect hernia goes from lateral to medial.
It will come in the direction of my pointer and slide down the inguinal canal.
It may not go all the way down the inguinal canal, but it will be in this location always going lateral to medial.
You then move your transducer medially into Hesselbach's triangle where number three is demarcated and have the patient Valsalva.
That would be a direct hernia.
A direct hernia will protrude from posterior to anterior come toward your transducer and could be anywhere in that region.
The majority of them are close to the rectus abdominis muscle, but some of them are over behind the inguinal canal and can actually distort the inguinal canal.
And then you slide your transducer one more superiorly along where the inferior epigastric artery is delineated, semilunaris is the anatomical name for this position and look for what is called a Spigelian hernia.
This would be a hernia that protrudes between the rectus abdominis muscle and the external oblique.
And it will protrude toward the transducer.

Usually the quick version of a hernia exam then is search for a femoral hernia look medial to the femoral vein.
The femoral hernia goes from superior to inferior.
The femoral hernia occurs in females almost exclusively, and it has a propensity to strangulate.
At its worst, the hernia will protrude into the medial thigh and the patient will complain of a mass in the medial thigh.
An indirect hernia goes from the anterior inferior iliac spine to the symphysis pubis.
It's congenital, it occurs in males, it's anterior to the spermatic cord, which you can find.
Sometimes the cord runs along the posterior portion of the inguinal canal, and a direct hernia protrudes from medial to anteriorly and is behind the cord.
It's in older males, sometimes it's called an old man's hernia.
Direct hernia does not strangulate the Spigelian hernia moves posterior to anterior at the linea semilunaris and occurs anywhere along that line.
There's no strangulation or rare strangulation with a Spigelian hernia.
An umbilical hernia occurs in females may strangulate and may not be exactly in umbilicus.
And those are the basic facts for the major types of hernias.

Hernia Terminology

We'll talk about terminology here for just a second.
The neck of a hernia is the part, the narrow part, the part where the defect is located in the fascial plane through which the hernia protrudes.
You need in your report to give the size of the neck, the sac, our body of the hernia is the main part of the hernia.
You need to give the size of the sac and describe the contents.
Are the contents fat or the contents bowel Tell what's in the hernia 'cause that helps the surgeon know how urgent it is to repair this hernia.
A strangulated hernia is a hernia where there is ischemia of the parts of the body in the hernia sac.
You actually can't tell this well at ultrasound.
And so I don't use the term strangulated in my reports.
An incarcerated hernia cannot be reduced.
So incarceration is bad and may lead to ischemia, but you need to tell whether or not this hernia can be reduced.
So the next line you need to say, is it reducible or non-reducible in terms of the hernia sac.

Abdominal Wall Layers

Let's talk a minute about the sagittal layers of the abdominal wall.
Of course, the outer layer is skin and a surgeon would tell you there are several layers of fascia called Camper's fascia and Scarpa's fascia.
But we're gonna talk about the muscle layers, the external oblique, internal oblique, transversus abdominis.
And then deep to that is the transversalis fascia.
And finally, peritoneum.
These are the layers that are violated by these groin hernias.

Causes and Associations of Hernias

Let's talk about causes and associations of hernias.
Indirect hernias have a congenital component that's by bad collagen or we'll say less than ideal collagen.
All hernias are associated with a collagen abnormality.
There is an abnormal ratio of type three immature collagen to type one mature collagen hernias are associated with aortic aneurysms, so I'm always questioning as to whether or not I should look for an aneurysm.
At the same time I do a hernia exam At the current time, I do not extend my exam to look for an aortic aneurysm, but one could argue that perhaps I should an important association with hernias is cigarette smoking.
I almost always ask the patient as to whether or not they're cigarette smokers.
I'd say 70 or 80% of the patients I see with hernias are cigarette smokers, Ehlers-Danlos syndrome, mucopolysaccharidoses, obesity, poor conditioning, ascites, peritoneal dialysis, COPD.
And just about anything that makes you sick may lead to a hernia.
Femoral hernias in the thigh are associated with pregnancy.
The more pregnancies, the greater the chance of the hernia.
So the femoral hernia goes through a femoral ring, which is the entrance to the femoral canal.
And as I more or less indicated earlier, that is medial to the femoral vein.
This amounts to about 20% of the hernias in females, but only 5% in males.
I start my exam off looking for a femoral hernia because I am amazed at how often I find them, how often they're non-symptomatic.
And because they have a tendency to strangulate look just around the saphenous merger with the femoral vein look medial to the femoral vein and the hernia will be there.
As indicated earlier, there is a risk of strangulation.
These may extend into the medial thigh and they can contain fat and bowel.

Femoral Hernias

So this is an example of where you would see a femoral hernia.
This is the hernia medial to the femoral vein.
Just about the place where the saphenous vein comes in.
Look, a centimeter above a centimeter below where the saphenous vein is entering into the femoral vein.
This is an example of a small femoral hernia, just an incidentally found femoral hernia.
Would the surgeon repair this?
I doubt it, but they need to know about it because these hernias tend to enlarge over time.
These arrows mark where the femoral hernia is, there is fat protruding down alongside the femoral vein.
This is another larger femoral hernia.
It's the femoral vein is where I'm marking where I'm denoting with the arrow.
And this is the femoral hernia here, just a big glob of fat sticking down into the thigh.

Indirect Hernias

So now we're gonna talk about indirect hernias and let's just clear up some terminology here.
An indirect hernia is named because when the surgeon makes an incision in the inguinal region, an indirect hernia would come into the surgical field from above and from lateral and comes into the field indirectly.
So thus the name indirect hernia.
The indirect hernia enters the deep portion of the inguinal ring, which is marked by the inferior epigastric artery.
So that's why when you find the inferior epigastric artery, you'll have the deep ring.
This extends from the peritoneal cavity into the deep ring down the inguinal canal.
And by the way, the name of the inguinal canal in a female is the canal of Nuck.
These are often congenital because of a patent canal related to the descent of the testicle.
These are usually on the right more than the left.
They contain fat and or bowel.
The neck is at the deep ring and these are anterior to the spermatic cord.
So noted here in purple is the hernia protruding down to the upper part of the inguinal canal.
These may not go all the way to the scrotum.
They may extend just barely into this inguinal canal.
And this is an example of an indirect hernia.
Notice that there's fluid associated with the indirect hernia.
That is very common.
It's common for there to be fluid associated with all of these hernias.
But the fluid actually helps you.
So as the patient Valsalva, this clump of fat extends down the inguinal canal, then extends partially up.
This is, this hernia does not completely reduce.
This is a very small hernia, indirect hernia coming into the canal here.
Here are the inferior epigastric artery and vein right here, marked as hypogastric vessels, the other name for them.
But this is a very small indirect hernia.
If this were in me, I probably would not have it repaired, but it may get bigger over time.
And then this is a static image of another indirect hernia.
The neck is marked by the cursors.
This indirect hernia did not go up and down.
It did not move hardly at all.
You have to be aware that hernias may not be mobile.
It may be fixed in position.
And so now to identify this one, I had to identify the inferior epigastric artery and then locate where the inguinal canal is.

Direct Hernias

So what about direct hernias?
They're called direct hernias because when a surgeon would open the field and make an incision, the direct hernia would protrude directly from posteriorly into his field, also known as an old man's hernia.
It's poor coverage of the conjoined tendon.
Watch the conjoined tendon.
It's a combination of the internal oblique muscle, the transversus abdominis muscle and the transversus abdominis.
A neuroaponeurosis is just a flat broad tendon.
This is probably more often a tear that transversalis fascia than anything else.
It's usually wide, has a broad neck and is reducible.
These are not as important because they tend not to strangulate.
They're very, very common.
And these are almost always in smokers.
So this is in purple noting where direct hernias tend to occur.
This is Hesselbach's triangle.
Hesselbach's triangle to remind you, is marked by the lateral edge of the rectus abdominis muscle.
The inferior epigastric artery and the inguinal ligament.
So this can occur anywhere in this triangle.
It's more often closer to the rectus abdominis muscle than we have depicted here.
This is a transverse shot across the inguinal canal showing the spermatic cord and just reminding you that indirect hernias are coming up anterior to the cord as they come down the inguinal canal.
Direct hernia has come from posteriorly.
So if you can identify the striations of the spermatic cord, which you often can, then you may be able to figure out which type of hernia it is.
Does the surgeon care which type of hernia it is?
No.
They can fix either type and they actually don't care if it's an indirect or a direct.
This is showing you that a direct hernia is a protrusion through the transversalis fascia.
Most of the time it's breaking through this muscular wall.
It may break through other layers also.
And it is not unusual to have a direct hernia protrude posterior to anterior and then make some type of oblique course in between muscle layers.
So this is an example of a direct hernia protruding directly toward the transducer.
And here's another one.
Notice the broad neck.
This is not likely to strangulate.
This contains fat only and often these are very easy to see.
One thing I would mention is that we use a wide linear transducer.
The importance of that is that often you will be scanning and you'll scan in the region of the patient's symptoms and you will see motion often a corner of the image.
And that the wide field of view allows you to pick up hernias easier than you could if you were using a narrow field of view.
And this is a third direct hernia.

Spigelian Hernias

A Spigelian hernia is a defect in the aponeurosis of the internal oblique and the transversus abdominis.
It can be anywhere along the linea semilunaris.
The linea semilunaris is the line that separates the rectus abdominis from the oblique musculature.
So Spigelian hernia can occur all the way up in the upper abdomen, but it's usually in the lower abdomen where the inferior epigastric artery penetrates.
And the rectus abdominis is not as broad.
This projects posterior anterior, but may move obliquely just like a direct hernia.
And so this shows you where a Spigelian hernia may occur.
So this is the linea semilunaris running along this line all the way up and down.
But as I said, usually they're in the lower abdomen.

Umbilical Hernias

Umbilical hernias, they're quite common.
They're at the umbilical ring.
They may increase in size with age.
The hernia moves posterior to anterior.
Maybe these are caused by the round ligament, not reinforcing the umbilical ring properly.
It's not clear why they occur.
They tend to run in families.
You will find families where the grandfather had one or the grandmother had one, the mother had one and now one of the children has one.
The, perhaps it's secondary to late midgut return to the abdomen.
It's not completely clear.
Most adults actually have paraumbilical hernias that are centimeter or two away from the very central part of the umbilicus.
These tend to be in obese people, very often.
These are very heavy obese women.
You need to repair.
The surgeon needs to repair umbilical hernias 'cause they tend to strangulate.
And we've all seen these on CT and you can see them easily on ultrasound.
This is the neck.
The sac is up here.
This one looks like it has only fat in it, but this will get bigger and bigger if it's not repaired.
And this is another one with a very narrow neck.
And you can see that this is not going to reduce.
This just is not going to come back into the abdominal cavity.

Incisional Hernias

What about incisional hernias?
Ventral hernias, this is due to poor surgical anastomosis.
In the deeper layers following an abdominal procedure, you simply look over the incision.
I scan parallel to the incision and then I scan transverse to the incision.
These are usually pretty easy to see.

Sports Hernias

Sports hernia, groin pain.
In athletes, there are numerous causes of groin pain in the athletes literature is full of numerous explanations.
Many MSK radiologists, I'm gonna cite Don Resnick, think that this is tendinopathy of the rectus abdominis and the adductor longus.
I have found these to be very obvious on MRI, not as obvious on ultrasound.
We heard a talk earlier in this meeting about the ability to find these in ultrasound.
I've not had good luck doing that.
I have had some success occasionally finding these with ultrasound.
I personally prefer an MRI there.
The better name for these is athletic pubalgia.
There is a review paper in Radiographics regarding these, if you desire more information.

Complications of Hernia Repair

So the complications of repair of our hernia, we are often asked to look for a recurrent hernia.
The hernia does not occur where mesh has been placed.
It will not penetrate the mesh, but you must scan along the periphery of the mesh.
It tends to poke through along the edges of the mesh.
So I find myself working around the mesh all the way, top sides and bottom, trying to find a place where a new hernia is poking through infection after mesh has been placed.
You will usually have fluid, but you've got to remember that fluid is normal post-op for a month or so, so early in the post-op period, you're not gonna be very good at figuring out if there's a new infection.
Remember that the spermatic cord is thick postop, and that does not mean infection.
The dreaded complication is testicular ischemia.
The mesh is placed too tightly.
It obliterates the testicular artery usually at the deep ring, and the testicle becomes small with poor flow.
In a traditional repair without mesh, this doesn't tend to happen because the tissues will become looser by themselves.
But with mesh in place, you really have to worry about obliterating the testicular artery.

Steps to Performing a Hernia Exam

So what are the steps to doing a hernia?
Start with your transducer transverse to the femoral artery and vein.
Find the saphenous vein entrance into the femoral vein.
Have the patient Valsalva look for a femoral hernia.
Move the transducer approximately on the femoral artery and vein.
Look for the superficial and deep iliac circumflex arteries.
These are two arteries that go laterally.
Next vessel up is an inferior epigastric artery.
Rotate the transducer into the inguinal canal plane and look for an indirect hernia.
Move the transducer medially.
Look for a direct hernia.
Move the transducer superiorly along inferior epigastric artery.
Look for a Spigelian hernia.
Do it again standing.
Start out going supine with the patient.
And you can find your landmarks easier.
When you have finished this supine, you need to repeat it with the patient standing.

This is the arterial anatomy.
I start out going across the femoral artery.
I find the superficial iliac circumflex.
Most of the time I can see it.
It goes laterally.
I find the deep circumflex.
It goes laterally.
The first and only major vessel that goes medially is your inferior epigastric artery.

Here are the steps once again.
Step one at the femoral artery, looking for a femoral hernia.
Step two at the inferior epigastric, looking for an indirect hernia.
Step three, look for a direct hernia.
Step four, look for a Spigelian hernia.
Stand the patient up.
I cannot emphasize that enough.
You've got to look for them in the standing position.
These patients are not in good shape most of the time.
They don't have, they've not been doing their sit-ups.
They don't have good rectus abdominis muscle tone.
They cannot lie on their back and perform a good Valsalva maneuver to increase intraabdominal pressure.
Do them lying down first to find the landmarks, and then do them standing up.
There are a few patients in whom you will find the hernia lying down but not standing up.
But most of the time it's easier to find the hernia standing up.

Thank you very much.