Spleen and Retroperitoneum - SD

Introduction

Good day.
My name is Drew Free. I'm professor
of Diagnostic Radiology at the University
of Kentucky in Lexington, Kentucky,
and Chief of ultrasound there, which I have been for
nine to 30 years.
This evening's topic is a spleen
and retroperitoneum not a particularly glamorous one,
but one that's frequently overlooked, but always necessary.
We'll talk about the things that
get left by the wayside.
To round out
the discussions
of the abdomen and ultrasound.
Awesome.
The spleen and retroperitoneum are perhaps not the most
glamorous of all the subjects
that we deal with,
but they deserve some attention.
Let us proceed here.

The Normal Spleen

The spleen, the normal spleen,
we hold
to be about 12 centimeters in pole to pole length.
There are volumetric measurements,
which are probably not necessary.
There are some laboratories
that go up to 14 centimeters.
But we're all extremely conservative.
The spleen
has a texture of mid-level echoes,
and it should be uniform
and homogeneous throughout.
It is not uncommon
to see a small area of spleen medial to the hilum,
which is a lenal,
sometimes found at the lower pole.
But often in the hilum
of no particular significance other than
in the event of a splenectomy,
one needs to be
certain that all of the splenic tissue is removed.

Splenomegaly

Splenomegaly is a product of a number of different pathological conditions.
Lymphoproliferative diseases like lymphoma
and leukemia certainly can enlarge the spleen,
and it can do so
either homogeneously
or patchy in a nodular form.
Mononucleosis
and aids are two of the most common infectious causes of enlargement to the spleen,
although they can be abscesses as we'll see shortly.
The infiltrative diseases like Gaucher can also be
either homogeneous,
or heterogeneous in the enlargement to the spleen,
but obviously much less common
and in our practice and likely generalized.
One of the most common causes
of splenic enlargement is increased portal venous pressure
in cirrhosis, which causes enlargement
to the spleen to a quite great extent.
Given this homogeneous
and smooth set of echoes, that is the spleen.
This one measures approximately 18.5
centimeters in pole to pole length,
and by anybody's criteria would be enlarged.
This one happened to be from cirrhosis
and ous hypertension,
but there is no specificity, in fact,
on what has caused it.

Splenic Trauma

Ultrasound is perhaps not the most sensitive method
of approaching splenic trauma,
but is often the first imaging modality to be used in the traumatized patient.
It sensitivity of ultrasound with respect
to injury to the solid organs has been reported as low
as 30%, but it's certainly
a perfectly respectable starting point.
It should be noted here that that free fluid
by virtue of splenic trauma can often be seen
in the right upper quadrant.
And this is a product of both the peristalsis
and the pulsation of the intestines
and the mesenteric vessels, which propel
free intraperitoneal fluid in a clockwise pattern.
So that sub hepatic fluid is often seen
even with splenic trauma.
Hematomas can of course, be of any echogenicity,
ranging from hyper coic to almost anti coic,
depending upon the state of dissolution of the clot.
Let's look at a couple of those.
Here, in fact, is the right upper quadrant,
the right upper quadrant here is a normal looking liver.
Here is the kidney in here in Morrison space.
The sub hepatic
or hepa renal space is a very small amount of fluid,
which is the product actually of splenic trauma.
So it's not uncommon for this to be the only manifestation
of splenic rupture.
That said, one can occasionally see hematomas
or fractures within the spleen.
Here's one through the equatorial region of the spleen,
which clearly disrupts the normal pattern of splenic genicity.
Here's one to show the wide variety
that is markedly echogenic right through the middle
of the longitudinal axis of the spleen,
which is also an acute hematoma in this setting of trauma.
That said, it's probably more common
to see things like a subcapsular hematoma.
And this is one here,
a small hypoechoic capsular subcapsular hematoma,
and a much larger one several days later when the clot is resolving and leaving only the fibrin stranding
here as the solid components
and other complex subcapsular hematoma of the spleen.
All of these are documented in instances of trauma.
And here's one I call to your attention
that looks just about like its fellows
in the other panels.
But I've put a question mark on that for a very good reason.
And that is that that one is actually just a small segment
of the left lobe of the liver wrapping
around the spleen in the left upper quadrant
and stimulating a hematoma of the subcapsular region of the spleen.
This is another patient with that same phenomenon.
One traces the parenchyma back
and connects it with the left lobe of the liver.
To ensure that that is not hematoma.
You can put color flow doppler on it
and prove that there is profusion, which of course,
the hematoma would not have.
It is also important to think about color flow
and doppler to prove that areas
of hypo echogenicity within the spleen are not vessels.
Here in this instant is
a fracture of the spleen.
Here, the vessels are clearly visible
and there is no flow in the hematoma.
On the other hand, here is a patient severely traumatized with a very large hematoma in the subcapsular region,
and something that is hypoechoic here,
which could either be clot or a vessel.
And if it's vessel, it's clearly abnormal
because no vessel would be that large.
And it is, in fact, a pseudo aneurysm on the basis
of trauma, which must be either followed or intended to because that has a potential
of distant rupture, old injuries.
Then, of course, will then go on
to fibrosis and scarring.
Here is a fibrotic scar through the mid portion
of the spleen on the basis of old trauma.
In fact, in markedly distant trauma,
a hematoma can calcify in its rim.
And that's what this is, is a very remote very large hematoma in the spleen.
There's normal splenic parenchyma visualized here,
but the hematoma is stable.

Infections of the Spleen

As you see, infections produce a variety of appearances in the spleen.
Bacterial abscesses look in the spleen very much like they
look in the liver, and we treat them the same way.
Once upon a time, it was considered improper
to approach the spleen with a sharp instrument.
But we now have left that behind,
and we will drain abscesses in the spleen
as we would anywhere in the abdomen.
A peculiar sort of instances is the fungal abscess of the spleen,
which you will see almost exclusively in the
immunocompromised patient, the transplant
or the patient with HIV infection.
These are small hypoechoic regions within the splenic
parenchyma, often with a small
echogenic focus in the center.
They tend to be less than a centimeter.
They tend to be diffuse,
and they are the strongly
suggestive of fungal infection.
Most often,
this will be candida granulomas disease in the spleen will produce small punctate calcifications, which are the result of a basically subclinical infection by histoplasmosis.
And we consider those, at least in the Ohio River Valley.
We consider those sort of incidental findings.
Here is the typical bacterial abscess
with some internal echoes here in the spleen.
It is subcapsular and in intraparenchymal,
and here is our guide wire as we are putting a pigtail catheter in this to drain.
And it did just fine. These are the two limbs of the pigtail catheter,
and it's as routine as any other bacterial abscess
in the abdomen.
On the other hand here, instead
of the homogeneous splenic parenchyma,
one sees these very small hypoechoic areas scattered throughout the parenchyma here.
Another view here,
and if you use your imagination, here's one
with small tiny in the center of it.
I've circled that one here.
What that is, is a very small abscess from Candida.
We are told that the small echogenic in the middle is
supposed to be a thrombo vessel.
And when one sees these target
or wheel within wheel patterns in the spleen
or parenthetically in the liver, one thinks of fungal abscesses.
It is true that a target shaped lesion can be produced by metastatic disease,
melanoma being the primary offender there.
But those tend to be much larger
than the less than one centimeter fungal abscesses.
So that's one of the things that we differentiate them.
And here, of course, are the multiple small calcific granuloma that we speak a former infection with histoplasmosis.
This patient is asymptomatic
and was, in fact, at the time of acquisition
of the infection asymptomatic as well.

Splenic Tumors

Tumors can be seen in the spleen.
We tend not to remember that metastases go to the spleen,
perhaps not as often as the liver, but they do happen.
Lung, breast and melanoma are three of the most common offenders.
And as I said, when they produce a target shaped lesion, they tend
to be larger than the fungal abscesses.
Lymphoma. Leukemia are probably the most common causes
of focal enlargement
or focal tumors in the spleen.
They tend to be hypoechoic as is lymphatic tissue almost everywhere.
They could cause homogeneous enlargement,
but they tend to want to cause focal abnormalities
as you see here with these several areas
of hypoechoic lymphatic infiltration in Hodgkin's disease,
and know there is no specificity to suggest
that this is Hodgkin's as opposed to non-Hodgkin's lymphoma.
But lymphoma would be high on the list of potential causes.
We tend to forget that the spleen, like the liver,
is subject to having cavernous hemangiomas.
And the echogenic well circumscribed, slightly lobular lesion here in the patient with no known primary tumor is a cavernous hemangioma just
as it would be in the liver.
And under five centimeters, they tend to be homogeneous.
If there is any question about them
or a concern, they obviously can be confirmed
by either a ct or mr
or even nuclear medicine if they're larger than two and a half centimeters.
But generally if it looks characteristic in the patient,
otherwise without problems, we can follow them or
or just declare them to be hemangiomas.

Splenic Cysts and Vascular Abnormalities

The true splenic cyst is an unusual sort of animal, but it's hard to tell the true splenic cyst, one
that has an epithelial lining from the old hematoma
that is now resolved into a cystic region.
This is histologically proven,
a true splenic cyst,
but could just as well have been a
an old resolved hematoma.
When we see serpentine tubular structures in the region of the spleen, as in here,
color flow Doppler will confirm
that they are tortuous vessels.
And this is in a patient with spleen shunts in portal venous hypertension.
Whenever flow is reversed in the splenic vein,
it is imperative to look in the region
between spleen and kidney to find these collaterals as
there has to be some sort of outflow for pressurized blood from the port venous system.

The Retroperitoneum

The retroperitoneum, again, is one of those less than glamorous areas,
but divided into three spaces, the anterior with the most interesting structures, the per peroneal
and posterior perineal spaces.
Let's look at what is contained in each
of those in the anterior pararenal space, the ascending
and descending colon, as well as three portions
of the duodenum, the pancreas is there,
and despite some controversy in the literature, the anatomic literature,
there is an investiture of fascia
around the great vessels and the takeoffs of the mesenteric vessels that actually do lie in the retroperitoneum.
So that there's a great deal going on there, and we need to look at it.
The pararenal space, of course, has kidney, adrenal
and proximal ureter.
And if we have time, we'll get to the adrenal gland,
but we may not make it in this session in the posterior peren space,
it actually has nothing in it, or should have nothing in it.
But winds up with adenopathy on occasion,
the retro fascial spaces, of course,
taken up by all of the muscles.
And occasionally we will see abnormalities involving those.

Solid Retroperitoneal Masses

So solid retroperitoneal masses are vast majority are involved by lymphadenopathy,
either primary or secondary.
It's not possible to tell morphologically by ultrasound whether they are metastatic nodes from a distant tumor or primary involvement by a proliferative disease.
But it's fairly well agreed
that anything greater than a centimeter
and a half for a lymph node is abnormal,
with the exception of the retro curl region in which anything greater than six millimeters is considered abnormal and must be accounted for.
Let's look at some of those primary lymphoma, secondary lymphatic involvement and lymph adenopathy would be often testicular in origin.
But pelvic neoplasms as well as lung, gi,
even breast and melanoma can cause retroperitoneal adenopathy.
The one thing about abnormal nodes is
that they tend, instead of being elliptical, they tend
to become more spherical as they enlarge,
and of course, have no internal architecture,
the hilum of the node being destroyed.
We'll see a bunch of those.
Here in the retroperitoneum,
they're generally hypoechoic.
Here is the spine here, it actually is the neural canal.
So this is actually the intervertebral disc space.
All of this is a mantle of nodes surrounding the retroperitoneal grade vessels.
And it's almost impossible to tell which of the lobular things is the vessel.
But actually, it turns out that's the aorta.
Here one more clearly.
Here's the anterior spinal margin, the aorta here
and lobular nodes in the retroperitoneum silhouetting the great vessels.
And they're almost always hypoechoic,
sometimes almost impossible to tell which the vessel is.
And here we've put spectral doppler on this on this aorta to prove that it's the aorta here completely surrounded by all of this lobular adenopathy and sometimes useful for just for orientation.
Here again is the aorta.
We know this because we put color flow doppler on it.
This is seminoma metastatic to the retroperitoneum.
And all of this echogenic material is adenopathy.

Retroperitoneal Fluid Collections

Retroperitoneal fluid collections are either infectious or traumatic.
It is not uncommon for us to see a hematoma along the sous muscle from cardiac catheterization.
Those folks use fairly large catheters,
and it's not uncommon for blood
to dissect from the groin back up along the sos muscle.
They're, they range in echogenicity from highly
echogenic to hypo coic depending upon their stage of dissolution, trauma and coagulopathy are certainly possible.
Abscesses can happen,
sometimes from contiguous disease like inflammatory bowel disease,
but sometimes from distant infections,
particularly in children that decide to seed the retroperitoneum there.
And lymphic seals usually on the basis
of retroperitoneal lymph node dissection can happen in the retroperitoneum and produce fluid collections.
Here, in fact, is a an abscess tracking along the sos muscle.
This one happened to be from inflammatory bowel disease, but could be from any either contiguous
or distant focus.
We drained that one much
as we would drain any other.
Here is our wire,
and here is the tube placed within the abscess.
Not a problem as long
as you can see it with ultrasound.
And there are no intervening structures.
There's no reason why you can't drain it With ultrasound, despite the propensity in modern radiology to go to CT
for everything, it's not necessary.
And here's another one in the paracolic gutter, noticed
that there's a great deal of debris.
This is not artifactual a great deal
of debris within this abscess.
I confessed to having forgotten what the source
of it was, but it's another paracolic right lower quadrant abscess,
could be a ruptured appendicitis that we can drain without great difficulties, hematomas happen.
And again, they are a product often.
This is a cardiac cath patient who had a large hematoma tracking up from the groin.
And notice how echogenic this one is, they resolve,
and the clot retracts leaving serum
around in this other patient.
So that abscesses run the entire gamut of appearances.
And here we've put a pigtail catheter in this one to drain it before it got infected occasionally.
And we now see this with less and less frequency
because more of the vascular work is being done in an endovascular basis.
But unless here's a limb of an af bypass, you can see
by its corrugated appearance.
This one's surrounded by a leak,
a very large hematoma,
although certainly it is possible
to see he hematomas like this, even
with endovascular repairs.
And gauge the problem here is a lymphic seals like in fact, to be septated like this, this is an 11-year-old
with an idiopathic lymphic seal
that actually turned out to be that characteristic milky fashion.
And here's one secondary
to retroperitoneal lymph node dissection.
That too had the milky quality.
And it is here that we must caution that often the lymphic seals, for example, the ones we see with renal transplants produce clear straw colored fluid
because the fluid has not been through the mesentery
and has not picked up yl Micra.
And so it doesn't really look like lymph,
it looks like urine.
And the only way to tell the two apart actually is
to send a sample for creatinine.
A caution here, trauma
to the kidney will occasionally produce a hematoma.
And this one, one can walk past very, very easily
because it's echogenic like the rest
of the surrounding structures.
But notice it produces this straight line compression
of the renal parenchyma
and is markedly echogenic acutely.
But this is a biopsy
induced hematoma of the kidney.
We do all of the renal biopsies in the ultrasound lab,
and this is a small collection of perinephric fluid,
which certainly could be seen in trauma to the kidney.
And this one's not. It is a small collection
seen in patients in chronic renal
failure from whatever cause.
And I must confess that our nephrologists have not been able
to explain this to me on any cogent basis,
but they say that we see that, and of course, we do.
So not to be convinced that that is trauma,
that is not chronic renal failure, patients will manifest that.

Primary Retroperitoneal Neoplasms

Primary retroperitoneal neoplasms
are of course not very common.
And most of those are sarcomas
because most of the tissues in the retroperitoneum are mosaical in origin.
A caution here when one says lipo sarcoma, one is given to think of fat and echogenic fat,
but often the lipos sarcoma has enough connective tissue
or supporting stroma such that it's not exactly as echogenic as one might expect.
It can mimic a hematoma very easily.
I recall one patient anecdotally, who came in
with what we thought was a large retro al hematoma,
a soccer player who had been kicked by one of his opponents.
Two months later, the thing looked exactly the same,
and finally, they operated on it.
It was a lipos sarcoma that was really much more hypoechoic than we would
have thought.
So that is a caution.
Don't be lulled into complacency.
It could do that.
Here is a sarcoma in the retroperitoneum,
right over the iliac vessels.
I've forgotten what the origin of
that one was, but we biopsied that,
and it was, in fact a sarcoma.
It looks like muscle tissue
because it is closely akin to muscle tissue.
But any solid mass in the retroperitoneum that is
it is more than hypo aic must raise that question.
And here's a another sarcoma right
behind the liver and above the kidney.
That one is a very unusual bird
because that one turns out to be a non osseous or extra osseous osteosarcoma.
But there is nothing on the ultrasound scan to say
that merely that it is a solid tumor in the retroperitoneum that does not look like adenopathy, and
therefore would raise the question of a sarcoma, which
of course is what this was.

The Adrenal Gland

Normal Adrenal Gland

The adrenal gland we normally don't see much past the toddler age group in newborns and little kids, you can see this quite easily.
It's either y shaped or a thin crescent.
It has an echogenic medulla
and the hypo coic cortex which makes it look like a mini kidney.
The caution here is that in the face
of renal agenesis where the kidney is not there
to shape the adrenal gland, it can plump up, look ovoid.
It actually look like a small kidney.
They can be up to about a third the size
of a kidney in a newborn.
So even in re renal agenesis that can be a problem.
Here in the child is a normal kidney
with a normal two-phase adrenal gland.
This one happens to be chevron shaped,
and you can see the medulla
and the cortex quite nicely.
And here's a series of small kids in whom visualization of the adrenal gland is really not a problem.
You can see the cortex and the medulla,
and here, here are the both limbs
of it, as well as the body.
Not a problem to see the adrenal gland in kids.

Adrenal Hemorrhage

But once in a while it enlarges it can do that fo
or diffusely with hemorrhage into the adrenal gland in a child.
And so here's a kidney and
a focal enlargement of this adrenal gland produced
by birth trauma, neonatal hemorrhage.
And here's one that's diffusely enlarged
and sort of heterogeneous.
That one also is hemorrhage.
And it can be as you say, either focal or diffuse.
An old calcified hematoma then shrinks down
to be nothing more than a focus or nubbin of calcification.
You can't really see the adrenal gland,
but you know that this is a senal calcification without an
associated mass.
And of course, calcification
with a mass would make you think of neuroblastoma.
But this one's just calcification without
the soft tissue component.
We can be comfortable that that is a resolved distant adrenal hemorrhage.
All the adrenal hemorrhage can produce the cyst.

Adrenal Cysts

The cystic thing that looks like a congenital cyst.
This one is a hematoma with some particulate matter.
This one is a true cyst
and morphologically, they really look about identical.
No way to tell, except if you have
to bet, bet on old hemorrhage.
The prevalence is much more common than true cysts.

Adrenal Tumors

I've listed as benign
and malignant adenomas are by far the most common.
They tend to be hypoechoic as they are hypodense at ct.
And even in the patient with a known malignancy.
Half of the enlarged adrenal glands will be on the basis
of an adenoma rather than a metastasis.
Mylo lipoma is fairly characteristic
because it is markedly echogenic,
and we can prove that without sharp instruments.
I've put pheochromocytoma on the benign side
with a question mark since they're 10%.
Arm malignant, ganglio neuroma
and ganglio neuroblastoma are the benign forms
of neuroblastomas.
We will occasionally see those
and adrenal cysts although the pure cysts can happen, tend more to be old hematoma hematomas.
Malignant enlargement of the adrenal gland metastases probably are
by far the most common lymphoma can do this metastases from a variety of primary neoplasms,
and the very enlarged
and often heterogeneous adrenal gland.
Anything greater than five centimeters is considered
adrenal carcinoma until proven otherwise.
And I'll show you some of those.
Neuroblastomas tend
to be markedly echogenic much more so than Wilms,
and they will displace the kidney where rather than take up a portion of it they will often flatten the superior margin of the kidney.
Calcification is much more common in neuroblastoma,
happening somewhere between five and 10% in Wilms,
but well over 50 to 70% in neuroblastomas.
The other thing that is fairly characteristic
of neuroblastomas, it tends to cross the midline
and produce a mantle of adenopathy over the great vessels, which is not something
that Wilms has a tendency to do.
And so we'll look at one of those.
Here is the echogenic mass in the senal region flattening the proportion of the kidney separable from it and separable from the liver.
One can watch it real time
and see clearly that the liver moves over this mass
and is separable from it.
That's fairly characteristic of neuroblastoma.
Here is one in which again, here's the neuro canal
and the intervertebral disc space.
Here with the arrows, you can see that
that neuroblastoma has crossed the midline
and produced a mantle of a fairly epigenic tumor
that is enveloping the great vessels here.
That is characteristic of neuroblastoma
and distinctly unusual for a wilms tumor to do that.
Ganglio neuroblastoma tends
to be a little bit more hypo coic than the
regular neuroblastoma.
This is supposed to be the red differentiation of a neuroblastoma into a benign form here.
That's what this is.
It is d difficult to distinguish sonographic,
but if it tends to be more hypo coic than the neuroblastoma itself, adrenal adenomas are usually less than three centimeters.
They're hypo coic again, as they are hypodense at ct.
The ultrasound appearances rather non-specific,
and when can prove by CT criteria that they are adenomas and leave them alone.
This is what they look like by ultrasound.
And as I said, ultrasound is not the ideal method for imaging small adrenal masses.
This one, we happen to be lucky
'cause our patient was a normal size,
which a great number of our patients are not.
That's an adrenal adenoma. Here is another one.
This is biopsy proven.
That one's a little bit more disturbing, which is
what led us to biopsy it because it's more epigenic.
Here's our biopsy needle,
and this was actually trans hepatic that we did that to prove that that's an adenoma
that we can leave it alone.
Myelo lipomas fairly characteristic.
It has myeloid elements,
but it has enough fat to make it markedly epigenic.
As long as you see this kind
of uniformly echogenic mass in the SRE region it is perfectly acceptable to do a non contrasted ct,
prove that it has fat elements in it and leave it alone.
That's not a problem.
Adrenal carcinoma tends to be large.
They're well circumscribed,
but they tend to be heterogeneous.
Often they undergo hemorrhage
or necrosis in the center.
Anything
that's greater than five centimeters in
the adrenal gland is abnormal.
This is an adrenal carcinoma.
Metastasis don't tend to get this large,
although there's nothing that says that they can't.
But this one's well circumscribed, as you see.
That's just a rib shadow.
But there are areas of inner homogeneity in this necrotic adrenal carcinoma.
Metastases can be from virtually anything.
Lung, breast and melanoma, again, are the primary offenders.
Again, an adrenal mass in a patient, even
with a known primary malignancy in some other site is still 50 50 possible to be a an adrenal adenoma.
And so here are adrenal metastases from a
variety of causes.
Here's one that causes epigenic enlargement.
And this one we biopsied, unfortunately in the ICU
because we couldn't move that patient to ct.
We biopsied that one
that was a metastatic lung carcinoma in a patient on a respirator actually.

Conclusion

That in fact is a running look through
the retroperitoneum
and its associated structures.
Hope that's been helpful. Thanks so much.