Why Stomach Ultrasound Screening Is Essential

We ultrasound the liver.

We ultrasound the gallbladder.

We ultrasound the kidneys, pancreas, spleen, aorta, bladder, uterus, ovaries, prostate and blood vessels.

But what about the stomach?

The stomach is right there. It is one of the largest organs in the abdomen, and yet it is often treated almost like an obstacle during abdominal ultrasound rather than an organ we should actually examine.

One of the reasons is gas.

Gas is difficult for ultrasound. Sound waves do not travel well through gas, and a gas-filled stomach can obscure both the stomach itself and structures behind it.

But what happens when we change the acoustic environment?

We add water.

That is the basic idea behind gastric hydrosonography: using water to distend the stomach and create a fluid-filled acoustic window through which we can examine the stomach with ultrasound.

And this isn't a brand-new concept. Fluid-filled gastric ultrasound has been investigated for decades. Water displaces some of the gas, distends the gastric lumen and improves transmission of the ultrasound beam, allowing the wall and luminal contents to become much more visible.

What deserves renewed attention is how much modern ultrasound technology may allow us to see when we stop treating the stomach as an obstacle and start examining it systematically.

It Starts With an Empty Stomach.

The examination begins with fasting.

I prefer the patient to fast for at least eight hours so that we can first evaluate the stomach in its baseline state. Then, before introducing the water, we scan.

That baseline examination matters.

Is the stomach actually empty?

Is there retained food or fluid?

Can we identify the wall?

Is the stomach collapsed or distended?

Are there abnormalities that are already visible?

Fasting doesn't necessarily guarantee that the stomach will be completely empty, so retained contents can themselves become an observation rather than something we simply dismiss as a poor examination.

Then the patient begins drinking still water while I am scanning.

That part matters.

I don't simply want a stomach that has already been filled with water.

I want to watch it fill.

The research protocol proposes approximately 300–500 mL of water, adjusted for the individual patient's tolerance and the amount necessary to obtain adequate distention. The water can be consumed gradually while the examination is underway.

I can watch the water enter the stomach. I can watch the lumen distend. I can watch the gastric walls separate. I can observe movement and contractions. I can watch fluid move toward the pylorus and, when visible, into the duodenum.

Now we aren't just looking at a picture.

We are watching an organ work.

An Anatomy Lesson: What Are We Actually Looking At?

The stomach isn't just a bag that holds food.

It is a muscular, dynamic organ with distinct anatomical regions.

At the proximal stomach is the cardia, where material entering through the esophagus reaches the stomach. Superiorly is the fundus. The large central portion is the body. Moving distally, the stomach narrows into the antrum and then the pylorus, which controls passage into the duodenum.

When we perform stomach ultrasound, we can attempt to follow that anatomy systematically rather than simply finding one convenient image.

The antrum is often one of the easiest portions to identify sonographically. Other areas can be considerably more challenging because of depth, ribs, body habitus and, of course, gas.

This is also why patient positioning matters.

Water and gas move.

By scanning in different positions, including supine and decubitus positions, we can redistribute the fluid and improve our acoustic window into different portions of the stomach.

The proposed protocol uses systematic views of the antrum, body, fundus and pylorus rather than relying on a single image or scanning plane.

And then there is the stomach wall.

This is where it gets really interesting.

We Can See the Layers of the Stomach Wall.

With adequate distention and resolution, the stomach wall isn't simply one white line.

It has a beautiful layered sonographic appearance.

The normal fluid-distended gastric wall has traditionally been described as five alternating sonographic layers: an echogenic mucosal interface, a hypoechoic mucosa, an echogenic submucosa, a hypoechoic muscularis and an echogenic outer or serosal interface.

Those sonographic layers are important because we aren't only looking at how thick the stomach wall is.

We are looking at its architecture.

Are the layers preserved?

Are they smooth?

Is the wall uniformly thick?

Is there focal thickening?

Is the contour irregular?

Are the normal layers distorted or lost?

And is what we are seeing truly abnormal, or did we just capture the stomach while it was contracting?

That last question matters.

The stomach is moving.

The degree of distention affects apparent wall thickness, and contraction can make the wall temporarily appear thicker. Measurements therefore need to be obtained thoughtfully, ideally when the stomach is adequately distended and the segment being measured is relaxed.

Published measurements vary with technique and distention, but the literature summarized in our research describes a fluid-distended gastric wall in the range of only a few millimeters, with approximately 3–6 mm reported in experimental work and increasing wall thickness becoming more suspicious depending on the clinical situation and technique.

That is why I don't believe stomach ultrasound should ever be reduced to one measurement.

Look at the wall. Look at the layers. Look at the lumen. And watch what the stomach does.

And Yes, We Can Actually See Lunch.

I love this part because it makes the anatomy real.

Ultrasound can show gastric contents.

Water appears predominantly anechoic, giving us that wonderful dark acoustic window. Solid or particulate material produces internal echoes.

So if someone hasn't eaten for many hours and we still see solid material sitting in the stomach, that is an observation.

We aren't going to tell you whether the patient had pizza or a turkey sandwich.

But yes.

We can actually see lunch.

And once the water is introduced, we can watch what happens to those contents.

Do they move?

Do they mix?

Does the stomach contract?

Does fluid progress toward the pylorus?

Does the stomach remain markedly distended?

The new protocol also points out that pills, food particles, debris and other intraluminal material may be visible within the fluid-filled lumen.

That's information a still image cannot give us.

What Can We See With Stomach Ultrasound?

A water-distended stomach potentially allows us to evaluate much more than whether the stomach is simply "there."

We can evaluate its shape and degree of distention.

We can look at the wall thickness and wall layering.

We can evaluate the lumen and its contents.

We can watch contractions and peristalsis.

We can observe gross movement of water toward the gastric outlet.

We can look for focal or diffuse wall abnormalities, masses, retained contents and findings that may suggest impaired gastric emptying or obstruction.

We can use Doppler when appropriate to evaluate vascularity within an abnormal portion of the wall.

And occasionally, we may even see something moving in that water that definitely isn't supposed to be there.

What About Tumors?

This is one of the most important places to be precise.

Gastric tumors have been visualized with water-filled ultrasound, and published research

has demonstrated that gastric cancers can produce recognizable sonographic abnormalities.

But don't think only in terms of finding a big round mass.

The wall itself may tell us something is wrong.

A gastric malignancy may produce focal or diffuse wall thickening, an irregular luminal contour and disruption or obliteration of the normal layered architecture.

That is an important concept.

A normal stomach wall is organized.

Disease can disrupt that organization.

The research summarized in the Executive Summary includes studies in which hydrogastric sonography detected and staged gastric tumors, with performance varying according to tumor stage and location. It also notes that advanced gastric cancers may demonstrate substantially greater wall thickness than benign conditions and loss of normal stratification.

But larger and more advanced abnormalities are generally much easier to identify than tiny or superficial mucosal lesions.

And that is exactly why a normal stomach ultrasound cannot rule out gastric cancer.

Early mucosal abnormalities may be far too subtle for transabdominal ultrasound.

Endoscopy provides direct visualization of the mucosal surface and, critically, allows tissue to be sampled for biopsy.

So this isn't about replacing endoscopy.

It is about recognizing that ultrasound can provide meaningful structural information about the stomach that we have largely stopped asking it to provide.

What About Inflammation?

Yes. Inflammation can be seen with ultrasound.

When the stomach becomes inflamed, the gastric wall can change.

We may see thickening of the wall, particularly involving the mucosal and submucosal layers.

The normal layered appearance may become more prominent or altered, and Doppler may demonstrate increased vascularity associated with an inflammatory response. 

This is another reason water distention is so useful.

Once the stomach is distended, we can separate the walls and examine them rather than trying to evaluate a collapsed stomach. We can compare one region with another and determine whether the wall appears smooth and uniform or whether an area looks thickened, irregular or otherwise abnormal.

And we can add color or power Doppler.

Is there increased blood flow within the area of concern?

Is the thickening diffuse or focal?

Which layers appear involved?

Are the normal layers preserved?

These are all pieces of sonographic information.

Ultrasound research into gastritis is still developing, but inflammatory changes of the stomach can be sonographically visible. That makes inflammation another important part of a systematic hydrosonographic examination of the stomach.

What About Obstruction?

This is where the dynamic nature of hydrosonography becomes particularly valuable.

If the stomach is obstructed at or near its outlet, we may see a markedly distended stomach containing retained fluid or food.

But then we can add water and watch.

Does the water move toward the pylorus?

Does it pass through?

Can we see it entering the duodenum?

Does it remain in a progressively distending stomach?

What is the stomach doing in response?

Is there peristaltic activity?

Can we identify an obstructing abnormality?

The proposed protocol specifically describes the potential for hydrosonography to demonstrate delayed passage of ingested water and findings associated with gastric outlet obstruction.

That is one of the things I love about ultrasound.

Movement is information.

And Yes — Worms.

This one surprises people.

Parasites can sometimes be visualized with ultrasound.

Ascaris, for example, can have a very recognizable appearance.

Within fluid, an Ascaris worm may appear as a long echogenic tubular structure with a hypoechoic center—the classic inner-tube appearance. When seen in cross-section, it may have a target-like appearance.

And it may move.

Imagine watching that in real time.

The literature includes sonographic visualization of Ascaris within fluid-filled gastrointestinal structures, although that certainly doesn't mean every worm or every parasite will be detected by stomach ultrasound.

But it means that when we're looking into a fluid-filled stomach, we should understand what we might encounter.

Why Does the Lack of Radiation Matter So Much?

Ultrasound does not use ionizing radiation.

CT does.

That difference matters.

And it matters even more when we are talking about gastrointestinal patients, because abdominal symptoms and chronic GI conditions can lead to repeated CT examinations over years.

One CT.

Then another.

Then another.

The radiation doesn't become irrelevant simply because each examination happened on a different day.

The exposure accumulates.

Research summarized in this report documents cumulative diagnostic radiation exposure exceeding 20–30 mSv in some GI patients, with much of that exposure coming from CT. The report specifically identifies repeated CT imaging as a source of cumulative radiation exposure and cumulative cancer risk. 

And look at the dose from the examinations themselves.

An abdominal/pelvic CT can expose a patient to approximately 10–30 mSv, depending upon the examination and protocol. 

Put those numbers into perspective.

If we use 0.001 mSv as an example of a very-low-dose dental X-ray, a 10 mSv abdominal CT is numerically equivalent in radiation dose to 10,000 of those dental X-rays.

At 20 mSv, it is 20,000.

At 30 mSv, it is 30,000.

For one CT examination.

Now think about the patient with recurrent abdominal pain, inflammatory bowel disease, chronic gastrointestinal symptoms, cancer surveillance or another condition that results in abdominal CT after abdominal CT over a period of years.

We need to talk about that.

We need to count that exposure.

And we need to stop treating radiation as though it doesn't matter simply because it is being used diagnostically.

Ionizing radiation is capable of damaging living tissue. At much higher therapeutic exposures, radiation to the abdomen and pelvis can produce direct gastrointestinal injury, including radiation enteritis and enteropathy. 

So when we have an imaging modality that can examine the stomach without adding any ionizing radiation exposure, that isn't a footnote.

It is a major advantage.

With ultrasound, we can examine the gastric wall.

We can evaluate its layers.

We can look for thickening and masses.

We can see retained contents.

We can watch peristalsis.

We can watch water move through the stomach toward the pylorus.

We can repeat the examination when necessary.

And every time we do it, the patient's ionizing radiation dose from that ultrasound examination is:

Zero.

What About Endoscopy?

Endoscopy is commonly used to evaluate the stomach, but it is invasive.

A scope is passed through the mouth, down the esophagus and into the stomach. Sedation may be used. There are risks associated with the procedure, including bleeding, perforation and complications related to sedation. Your research specifically identifies those disadvantages when comparing endoscopy with noninvasive ultrasound. 

And then there is biopsy.

A biopsy means removing tissue from the body.

I don't believe we should treat taking a piece of someone's tissue as though it is an insignificant step in the diagnostic process.

There are certainly circumstances in which physicians determine that tissue sampling is necessary. But my question comes earlier:

What can we learn before we do something invasive?

With gastric hydrosonography, we can examine the stomach from the outside.

We can evaluate the gastric wall and its layers.

We can look for focal or diffuse thickening.

We can look for masses and changes in normal wall architecture.

We can examine the lumen and its contents.

We can observe peristalsis.

We can watch the stomach distend.

We can watch fluid move toward and through the pylorus.

We can evaluate surrounding anatomy.

And we can do all of that without putting an instrument inside the patient and without removing tissue from the patient's body.

That distinction matters to me.

The question shouldn't always begin with:

What invasive test can we perform?

Sometimes it should begin with:

What can we learn without invading the body at all?

That is where I believe ultrasound deserves a much larger role.

What About MRI?

MRI doesn't use ionizing radiation either, and that is an important advantage.

But MRI is considerably more expensive and time-consuming and is not routinely used as an immediate dynamic examination of the stomach in the way ultrasound potentially can be.

The research summary identifies those practical differences among gastric imaging modalities.

Ultrasound is immediate.

It is dynamic.

It is repeatable.

And I can put the transducer on the patient, introduce water and watch the physiology unfold in front of me.

That is something ultrasound does extraordinarily well.

How Would We Actually Perform This Examination?

This is a systematic examination of the stomach, beginning with the fasting stomach and continuing during and after water ingestion.

The patient fasts for at least eight hours before the examination. Before introducing water, the stomach is evaluated in its baseline state.

First, we determine whether the fasting stomach is actually empty.

We look for retained food, fluid, debris or other luminal contents. If solid gastric contents remain despite appropriate fasting, that finding is documented. The appearance and amount of retained material can then be compared with what happens after water is introduced.

The patient then drinks approximately 300–500 mL of still water gradually while the stomach is continuously scanned. The amount can be adjusted according to patient tolerance and the degree of gastric distention obtained. 

Scanning during ingestion is important because the filling process itself can be observed.

We can see the water enter and distend the stomach, watch the walls separate, observe movement of the gastric contents and evaluate contractions as they occur.

Following the Entire Stomach.

The stomach should be examined systematically from the proximal stomach through the gastric outlet:

Cardia → Fundus → Body → Antrum → Pylorus

The examination is performed in multiple scanning planes, including longitudinal, transverse and oblique views.

Patient position is changed as necessary. Supine and decubitus positions allow the water and gas to redistribute within the stomach, creating different acoustic windows. Upright or semi-upright imaging may also be useful. The fundus, body, antrum and pyloric region should each be evaluated rather than relying on a single view of the stomach. 

A lower-frequency curvilinear transducer provides the penetration necessary to survey the stomach and surrounding anatomy. A higher-frequency linear transducer can then be used, when depth permits, for detailed evaluation of the gastric wall. 

Measuring the Gastric Wall and Its Layers.

Once the stomach is adequately distended, the wall can be evaluated in much greater detail.

The normal fluid-distended gastric wall demonstrates five alternating sonographic layers: an echogenic mucosal interface, hypoechoic mucosa, echogenic submucosa, hypoechoic muscularis and echogenic outer or serosal interface. 

We evaluate the thickness and appearance of these layers throughout the visualized stomach.

Are all five layers visible?

Are they uniform?

Is there focal or diffuse thickening?

Is one layer disproportionately thickened?

Is the normal stratification preserved, distorted or lost?

Is the inner gastric contour smooth or irregular?

Wall measurements should be obtained when the stomach is adequately distended and the segment being measured is relaxed. This is important because a normal contraction can temporarily thicken the gastric wall. The protocol calls for measuring the wall in a fluid-distended, relaxed segment and documenting whether normal wall stratification is preserved or disrupted. 

Evaluating What Is Inside the Stomach.

The lumen is evaluated just as carefully as the wall.

Water provides an anechoic background against which food, debris, pills, foreign material, masses and other intraluminal contents may become visible. 

When something is identified, we can observe its behavior in real time.

Does it move freely with the gastric contents?

Does water move around it?

Does it change position when the patient changes position?

Is it attached to the gastric wall?

Does it produce shadowing?

And we can add color or power Doppler.

Food and debris do not contain their own blood supply and therefore should not demonstrate intrinsic vascular flow. Tissue arising from or involving the gastric wall may demonstrate vascularity. Doppler can therefore provide additional information when we are trying to determine whether something represents luminal contents or vascularized tissue.

Doppler can also be used to evaluate increased wall vascularity when inflammation is suspected. 

Doppler is one piece of the examination rather than a single deciding test. A lack of detectable flow alone does not establish that something is food.

Watching the Stomach Function.

Water also gives us the opportunity to assess the stomach dynamically.

We can observe contractions and peristalsis and follow the water as it moves through the stomach toward the antrum and pylorus.

We can watch for passage through the pylorus into the proximal duodenum.

We can record the time from water ingestion to observed passage.

We can document whether passage appears prompt or delayed, whether water remains within a distended stomach and whether the stomach continues contracting without effective emptying.

Failure or delay of ingested water passing through the gastric outlet can provide important information when gastric outlet obstruction is suspected. 

There is not yet a validated normal transit-time cutoff for this specific hydrosonography protocol. Recording the time during examinations, however, provides an objective measurement that can be evaluated as the technique is studied prospectively.

Documenting the Examination.

The examination should include representative still images and cine clips of the gastric regions that can be visualized.

Documentation includes the fasting appearance of the stomach, retained contents if present, volume of water ingested, patient positions, transducers used, gastric regions visualized, wall thickness, appearance of the wall layers, luminal contents, Doppler findings when obtained, peristalsis, pyloric appearance and observed passage of water.

Any focal mass, diffuse or focal wall thickening, disruption of normal wall stratification, retained contents, abnormal vascularity, unusual intraluminal structure or evidence of impaired emptying should also be documented. The proposed protocol specifically includes still images and cine loops because filling, contraction, peristalsis and passage are part of the examination. 

In this way, gastric hydrosonography provides both structural and functional information about the stomach in real time.

Considerations and Limitations.

As with every imaging examination, gastric hydrosonography depends on obtaining adequate visualization.

Residual bowel gas can interfere with portions of the examination, and increased imaging depth may make detailed evaluation of the gastric wall more difficult. Patient positioning, water distention, transducer selection and scanning from multiple acoustic windows can all be used to improve visualization.

The examination also requires the patient to safely drink water. Patients with significant difficulty swallowing, an increased risk of aspiration or suspected gastrointestinal perforation should not undergo routine water ingestion for hydrosonography. 

The quality of the examination is also dependent on technique. Adequate gastric distention, systematic evaluation of the entire visualized stomach, appropriate wall measurements, assessment of the wall layers, Doppler when indicated, observation of gastric movement and careful documentation are all important parts of obtaining a useful study.

Hydrosonography is particularly well suited to evaluating gastric anatomy, wall architecture, luminal contents and dynamic function in real time without ionizing radiation.

So Why Do I Believe Stomach Ultrasound Screening Is Essential?

Because I think we have spent too much time asking:

What test do we normally order for the stomach?

And not enough time asking:

What can we actually see with ultrasound?

Start with the fasting stomach.

Look at what is there.

Add water.

Watch it fill.

Follow the anatomy.

Examine the wall.

Look at the layers.

Look at the lumen.

Look at the contents.

Watch the contractions.

Watch the pylorus.

Watch where the water goes.

Look for what belongs there.

And look for what doesn't.

If we see something concerning, that patient may need endoscopy, CT, MRI, biopsy or another appropriate examination.

Hydrosonography still needs prospective validation. Questions remain about optimal water volume, normal measurements, sensitivity for subtle disease and exactly where this examination should fit into routine clinical practice. The proposed research plan specifically identifies those unanswered questions and recommends prospective comparison with established reference examinations.

I think those are questions worth answering.

Because if we can obtain meaningful structural and functional information from the stomach with a noninvasive examination that uses no ionizing radiation, why wouldn't we investigate how far that ability can take us?

The stomach isn't invisible to ultrasound.

Sometimes we simply need to create the conditions that allow us to see it.

And sometimes, all it takes is water.