Understanding GP

Diagnostic Tools for Gastroparesis

Intro / Digestion / Who gets GP / What happens / Symptoms / Dx / Mild forms / Tx

 

Diagnosis: a brief historic overview:

The bad news is that, historically, there has not been a good approach to document, with diagnostic tools, what the problems were in gastrointestinal motility disorders (dysmotilities).

 

The good news is that professional organizations like the American Neurogastroenterology & Motility Society are working to provide leadership in standardizing and advancing diagnostic tests.

 

Motility disorders such as gastroparesis are disorders of physiology, or gut function, not a structural problem of the gut. The problem won't be found unless it is properly searched for, with the appropriate diagnostic tools.

 

Looking back through medical research related to gastroparesis,

Gastric Emptying studies as they are done today, using radioisotope markers and a gamma camera, started to show up in the scientific literature around 1975. Diabetic Gastroparesis had been well documented and studied for a couple of decades prior to 1982, but Idiopathic Gastroparesis was not yet in general use as a diagnosis by this time. From the literature, it is evident that medical science was struggling with attempts to articulate what this illness was (Idiopathic Gastroparesis), and searching for diagnostic tools to understand it.

In 1982, researchers (Nagler et al) were interested in a group of patients who had "chronic postprandial (after eating) idiopathic upper gastrointestinal distress"¹. (Note the term Idiopathic Gastroparesis was not used). This research article talks about renewed interest in the use of Gastric Emptying Studies in attempting to understand this particular group of dyspeptic patients (symptoms of nausea, reflux, abdominal discomfort, feeling full after a couple of bites of food, etc.)^{1 2}.

EGG (ElectroGastroGraphy) was first used in 1922³. This tool is still not in wide use in a clinical setting, even today.

Motility studies (referred to in the literature as manometry techniques) have been around for some time, but only in the past 15 years have these techniques been used to help understand the physiology of the stomach.

 

 

DIAGNOSTIC/ASSESSMENT TOOLS

Tests NOT covered here include many tests important to rule out other diseases. Often, when a patient has a motility disorder, these tests are all normal. They include:

• upper GI study with a barium drink

• endoscopy with tissue biopsies

• taking of stool samples

• blood work,

• breath tests

 

 

Gastric Emptying Test—Solid Phase (carried out after consuming solid food).

GET can be done for solids (solid phase study) and/or liquids (liquid phase). Liquid phase studies are usually reserved for patients who cannot tolerate the solid meal study, that is, they vomit up the solid test material. Most individuals with gastroparesis have an emptying delay for solids only—the stomach is able to empty liquids.
 

Some facts on the GET:

• The Gastric Emptying Test (GET) is the "gold standard" method of diagnosing delayed gastric emptying⁴.

• The test has not been standardized.

• Every centre may do the test differently and use a different test meal. This prevents any meaningful comparison from one institution to another. Therefore, each new GI doctor you are referred to may want to run the test at his or her own institution.

• The GET is carried out in a lab (nuclear medicine department).

• The individual fasts the night prior to exam. Some centres instruct their patients, two to four days prior to the GET study, to discontinue any medications, which may have an impact on the emptying power of the stomach. Talk to your doctor because withdrawing your medication could put you into a severe symptom flare-up, taking you months to re-stabilize your symptoms.

• Radioisotope marker (low-energy radioactivity) is mixed into a test meal, which you eat.

• Gamma camera takes pictures of the stomach area at designated times. Some institutions have you lie down for the pictures; other institutions have you stand. Some institutions make the patient stay motionless in a bed for the hours during collection of the stomach images. The factors related to body position and freedom to move between images also has an impact upon the rate of stomach emptying, again, making comparison of test results from one institution to the next meaningless.

 

The data collected from the GET study is interpreted to understand how your tummy handled the meal and how long it took for the meal to leave your stomach.

 

Some institutions report this data as a T50, or the time it took for half of the test meal to leave your stomach, while other institutions report on a percentage of the meal remaining after 2 hours or 4 hours.

 

While the American Neurogastroenterology & Motility Society is working to standardize the GET tests, as has been mentioned, currently the duration at which Gastric Emptying Studies are carried out, as well as the test meals used, can vary significantly from institution to institution.

 

Research has shown that the diagnosis of gastroparesis can be missed in some individuals if the GET is carried out for only two hours—and yet, some centres still use a two-hour study. (Please see footnote #4a below for statistical details of McCallum et al. study.)

A multi-centre study established normal ranges for gastric emptying in healthy subjects at time intervals of 60, 120, and 240 minutes after completion of a consistent, radio-tagged, low-fat meal. Average gastric retention (healthy subjects) at 1 hour, 2 hours, and 4 hours was 90%, 60% and 10% respectively. These values are for adults only.⁴

The 4-hour Gastric Emptying Test is now becoming the standard test, using a low-fat egg-substitute meal to minimize the effect of fat on gastric emptying.⁴

It should be noted that besides the actual studies, gastroenterologists interpreting the gastric emptying values must utilize their clinical experience to take into account a variety of other factors.

ELECTROGASTROGRAPHY (EGG).

As an electrocardiogram (ECG) measures the electrical rhythms of the heart, so too can an electrogastrography (EGG) measure the electrical rhythms of the stomach. Please see Footnote #5a for statistics on correlation of EGGs and gastroparesis. The EGG remains controversial since some research studies have shown a high correlation between dysrhythms of the stomach and delayed gastric emptying, and other studies have failed to confirm this relationship.

Electrogastrography (EGG) studies can detect abnormal rhythms (dysrythms) in the stomach. The technical name for these is TACHYGASTRIAS (“tachy” meaning “rapid”, “gastric” meaning “stomach”, “dysrhythms” meaning “abnormal rhythms”). The discovery of abnormal rhythms in the stomach is just now bringing them into focus as an underlying factor in creating symptoms of nausea⁵. Some motility specialists commonly use EGGs in their clinical settings and are leading the research into shedding light on this abnormal muscular/electrical activity of the stomach

Part of the normal electrical activity of the stomach is to generate a gastric rhythm that can be detected and measured by EGG. It is believed that specialized cells (the interstitial cells of Cajal) help produce this effect in an area of the stomach known as the gastric pacemaker region. These gastric slow waves are produced about 3 cycles per minute. Some specialists believe that the EGG recording provides reliable information on slow- wave frequency and can provide clinically relevant information on abnormal electrical rhythms, termed gastric dysrhythmias⁶.

 

It is possible to have a normal emptying stomach, but abnormal EGG. Individuals who suffer from non-delayed, motility-like dyspepsia fall into this category.

MOTILITY STUDIES (known medically as Antroduodenal Manometry)

Motility studies are performed on selected patients with suspected or confirmed gastrointestinal motility disorders. Patients who may benefit are those with unexplained nausea and vomiting, abdominal pain, or suspected intestinal dysmotility as well as patients with suspected generalized dysmotility⁶. Very few centres have the capability to do these specialized motility studies. They are performed mainly to determine the nature of the motility disorder. The nature can be either:
   (i) myopathy in which the underlying motility disorder is primarily one of the muscle tissue not functioning properly; or
   (ii) neuropathy in which the underlying motility disorder is primarily one of the nervous tissue not functioning properly.
An antroduodenal manometry uses a catheter that must be placed via the nose and passed down to the duodenum. In one approach, the catheter is passed while the patient is awake. The patient participates in passing the catheter by swallowing sips of water. Esophageal peristalsis helps to pull the catheter into the stomach. The individual must then stay in a reclining position for many hours while water is run through the catheter. Continuous recording of antral stomach and intestinal (duodenum) contractions are monitored, first during a fasting state, then during a test meal.

Another method used to place the catheter is via endoscopy, which involves a flexible tube the doctor looks through. The patient is put to sleep and the doctor places the catheter, using endoscopy. The catheter can be placed down to the level of the jejunum (next segment of the small intestine beyond the duodenum).

Ambulatory methods of recordings (in which the patient is free to move about while recording occurs) can also be done using a solid-state transducer to record the gut contractions. These generally run for 16 to 24 hours. Catheter placement is performed using one of the methods described above.

Motility studies have demonstrated that antral hypomotility (weak contractions in the antrum part of the stomach) is a consistent finding in gastroparesis.

BAROSTAT STUDIES

Barostat studies are used when there is a suspected motility problem in the upper part of the stomach (fundus). An intragastric (inside the stomach) balloon is inserted and the balloon is inflated bit by bit while the patient reports perceptions of fullness and abdominal pressure.

WHAT'S ON THE HORIZON?

Newer methods for studying gastric motility are being developed:

 

The Water/Nutrient Satiety Test, which examines the extent of fullness a patient feels, is a non-invasive test proposed as an alternative to sensory studies performed with an intra-gastric balloon (barostat).

 

The Tensostat can be used as a gastric sensation test because it measures gastric wall tension, which is related to the perception of gastric distention/fullness.

 

The 13C Breath Test can measure the gastric emptying of solids or liquids and can achieve accuracy comparable with present GET. One big advantage of this test is that it does not expose the patient to radioisotopes (low-dose radiation).

 

Other tests suggested to measure gastric accommodation to a meal include:

• fundic motility ultrasound, and

• MRI and Single Photon Emission Computed Tomography (SPECT).

 

These novel, non-invasive approaches (except SPECT, which requires the IV injection of a radioactive marker), can assess different dimensions of gastric motility and sensation.⁷

In general, these new developments are not clinical practice yet, but are on the horizon.

It is exciting to know that new techniques are being advanced that will help increase the understanding of the stomach and gut dynamics. Such knowledge brings hope that better treatment modalities are to follow.

1)   Malmud LS, Fisher RS, Knight LC, Rock E.: Scintigraphic Evaluation of Gastric Emptying. Semin Nucl Med Apr;12(2):116-25 1982

2)   Nagler J, Miskovitz P.: Clinical Evaluation of Domperidone in the Treatment for Chronic Postprandial Idiopathic Upper Gastrointestinal Distress. American Journal of Gastroenterology 1981 Dec;76(6):495-9

3)   Koch K.: Electrogastrography: Methodology from Provocative Meals to Artifact Removal to Analysis. Paper presented at "American Motility Society Course on Motility in Clinical Practice", January 18-20, 2002, Charleston, South Carolina.

4)   McCallum R, Sabu J.G: Gastroparesis. Clinical Perspectives in Gastroenterology May/June 2001 pg. 147-154. McCallum et al reports:

4a)   "In a soon-to-be-published multi-centered study, we compared 2-hour and 4-hour results in patients suspected of having Gastroparesis and showed that limiting the gastric emptying time to 2 hours would have missed 94 patients (44%) who went on to have delayed gastric emptying at 4 hours. Sensitivity of the 2-hour test was 56%, with a specificity of 95%. Thus, an abnormal result at 2 hours is fairly reliable, and the test may be stopped at that point. On the other hand, conclusions should not be drawn from a 2-hour study that gives a normal result, and the study should be continued for a full 4 hours."

5)   Parkman H.P: Electrogastrography. Paper presented at "American Motility Society Course on Motility in Clinical Practice, January 18-20, 2002, Charleston, South Carolina.

5a)   One study revealed that 75% of patients with Gastroparesis have an abnormal EGG. However, other studies using EGG have not demonstrated a correlation with EGGs and Gastroparesis.

6)   Prather C.M: Antroduodenal Manometry: Methodology and Provocative Testing (workshop). Paper presented at "American Motility Society Course on Motility in Clinical Practice", January 18-20, 2002, Charleston, South Carolina.

7)   Kim Dy, Myung SJ, Camilleri M: Novel Testing of Human Gastric Motor and Sensory Functions: Rationale, Methods, and Potential Applications in Clinical Practice. American Journal of Gastroenterology 95(12):3365-73 2000