Investigations
1st investigations to order
FBC
Test
Lymphocytosis may be seen with viral infections, which can occasionally result in gastroparesis.
Result
typically normal; occasionally lymphocytosis
serum glucose
Test
If elevated, diabetes mellitus is screened for. Levels >16 mmol/L (>288 mg/dL) can cause delayed gastric emptying.
Result
elevated
serum creatinine
Test
Indication of abnormal renal function, due to dehydration from prolonged vomiting or possibly a cause of gastroparesis.
Result
elevated
serum potassium
Test
May be low as a result of prolonged vomiting.
Result
<3.5 mmol/L (<3.5 mEq/L)
liver function tests
Test
To check for hepatobiliary causes of symptoms.
Result
normal
serum total protein
Test
Indication of malnutrition.
Result
<60 g/L (<6 g/dL)
serum albumin
Test
Indication of malnutrition.
Result
<35 g/L (<3.5 g/dL)
serum amylase and lipase
Test
Recommended to exclude acute pancreatitis. Lipase is more specific than amylase for the diagnosis of acute pancreatitis. Levels of these enzymes are typically normal in patients with gastroparesis.
Result
normal
thyroid-stimulating hormone
Test
If hypothyroidism is suspected as a cause of gastroparesis, thyroid-stimulating hormone levels should be checked.
Result
raised in hypothyroidism; otherwise normal
HbA1c
Test
To check for diabetes, a common cause of gastroparesis. In people with known diabetes, an up-to-date HbA1c is useful to assess glycaemic control.
Result
raised in newly diagnosed or uncontrolled diabetes (≥6.5%)
pregnancy test
Test
Pregnancy is an important cause of nausea and vomiting to exclude in a female patient of child-bearing age.
Result
negative
Investigations to consider
gastric emptying scintigraphy
Test
Considered the definitive test for the diagnosis of gastroparesis. The test is non-invasive and can assess for solid and liquid emptying.[47][61]
It is highly recommended that a 4-hour test be performed: retention of >10% of the test meal at the end of 4 hours, or >60% retention after 2 hours, supports a diagnosis of gastroparesis.[1][62]
Result
gastric retention >10% of the test meal at the end of 4 hours or >60% after 2 hours is considered diagnostic of delayed gastric emptying[62]
upper gastrointestinal endoscopy
Test
Recommended to exclude causes of mechanical outlet obstruction (e.g., pyloric stenosis, neoplasia, and active ulcer disease in the duodenum, pyloric channel, or pre-pyloric antrum).
Result
if no cause of obstruction is found and retained food is present in the stomach after an overnight fast, this is supportive, but not confirmatory, of a diagnosis of gastroparesis
abdominal x-ray
Test
No specific abnormality is associated with gastroparesis. Multiple air fluid levels in patients with nausea and vomiting should raise suspicion for small bowel obstruction, which should be excluded.
Result
normal
contrast radiography
Test
Recommended to exclude small bowel pathology that can cause similar symptoms. Computed tomography (CT) enterography or magnetic resonance (MR) enterography are first-line. A barium follow-through examination can be performed if CT/MR enterography are unavailable.
Result
no small bowel pathology identified
wireless motility capsule (WMC)
Test
A non-invasive ambulatory test that measures transit times and pressure parameters throughout the gastrointestinal tract. It is a one-time use, non-digestible, portable, small capsule that, when swallowed, records and transmits data to a receiver as it travels through the gut. The capsule can measure pH, pressure, and temperature to track location, gastric contents, and expulsion time from the different regions of the bowel. It has been approved by the US Food and Drug Administration (FDA) for measuring gastric transit.[1] The patient takes the capsule after eating a standardised meal and wears a small monitor that allows the telemetry recordings to be made. Gastric emptying time is assessed from ingestion of the capsule, a point at which there is a low pH reading, to the moment where there is an abrupt rise in pH after it moves into the small bowel.[64] A gastric emptying time of >5 hours compares favourably with gastric emptying scintigraphy for the diagnosis of gastroparesis.[65] WMC can also identify delays in small bowel and colonic transit, thus providing an opportunity to evaluate motor function throughout the entire gastrointestinal tract, which may be indicated in patients with gastrointestinal symptoms.[1][66]
Result
gastric emptying time >5 hours is consistent with gastroparesis
gastric emptying breath test (GEBT)
Test
A standardised meal is given containing carbon-13 (C-13)-labelled spirulina. A minimum of five samples are collected at baseline and over a 4-hour period and sent for analysis. Nine samples are recommended for diagnosis of rapid gastric emptying or for characterising early gastric emptying.[63]
Result
half-life value of 79 minutes or more is considered abnormal
Emerging tests
electrogastrography
Test
Electrogastrography (EGG) is a non-invasive technique for recording gastric myoelectrical activity using cutaneous electrodes placed on the abdominal skin over the stomach. Studies suggest a complementary role of spatial mapping EGG for identification of the pathophysiological mechanism of gastric function.[67] However, at this time, it is unclear if the information is clinically meaningful. Ongoing research of high-resolution EGG is needed to help clarify its clinical role.[1]
Result
may show slow-wave dysrhythmia
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