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What are the diagnostic tests for gastrointestinal disorders?

Diagnosing GI disorders is critical to effective treatment and prevention of complications.

The various ailments of the gastrointestinal (GI) tract affect food digestion and absorption. Diagnosing them is critical to effective treatment and prevention of complications. Here are 11 diagnostic tests that help diagnose various GI disorders.

1. Clinical examination

The symptoms present and a physical examination may help diagnose a few GI disorders like diarrhoea, constipation, acidity, etc. For diseases like haemorrhoids, physical rectal examination may be done wherein the doctor inserts a gloved finger into the rectum to feel for abnormalities.

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2. Blood test

Blood tests like blood count, liver function test, lactose tolerance test, antibodies to H. pylori, pancreatic enzyme test, etc. can help diagnose certain GI conditions like bacterial or parasitic infection, celiac disease, lactose intolerance, exact cause of diarrhoea, etc. They may also be recommended to rule out other serious diseases. The laboratory tests to determine liver efficiency include CBC (complete blood count), liver function tests (SGOT, bilirubin, alkaline phosphatise, etc.), blood albumin and prothrombin time.

3. Stool analysis

Stool analysis can help assess the overall health of GIT. It helps analyse digestion, absorption, microbial balance, etc.This gastrointestinal test profile may be advised in conditions like indigestion, constipation, diarrhoea, IBS, malabsorption, infection, etc. For the analysis, a stool sample collected in a clean container is sent to the laboratory for microscopic examination and other tests.

Changes in colour, consistency and pH, and the presence of mucus, blood, white blood cells, bile, fat, sugars, etc. help diagnose GI conditions. A stool culture can help diagnose bacterial infection. Increased fat levels in the stool may be seen in celiac disease, pancreatitis, etc. High pH of the stool could indicate inflammation, cancer, etc. Some enzyme immunoassays are used to detect viral and bacterial antigen in stool sample.

4. Renal function test

Gadolinium containing contrast agents, most commonly used in MRI and CT scans, are avoided in patients with reduced kidney function or kidney failure. Hence, kidney function tests are done prior to MRI or CT scans of GIT.

5. Endoscopy

Long-standing acidity, heartburn, unexplained weight loss and changes in bowel pattern may need a detailed investigation of the intestine. Endoscopy is a non-surgical procedure that involves examination of the stomach or digestive tract with the help of an instrument called endoscope. Biopsies (small tissue sample) may also be taken during endoscopy to be examined under microscope. They can help detect presence of cancerous cells.

  • During colonoscopy, a tube is inserted through the anus to visualise the colon. It aids in detection for areas of inflammation or small ulcers in the colon. Proctoscopy can help visualise the rectum.
  • In case of a tumour in the intestine, an ultrasound followed by endoscopy, imaging, scans, etc. of the upper intestine is done to study the nature of the growth. An endoscopy ultrasound (EUS) can help make an accurate diagnosis without having the need to undergo several tests.
  • In endoscopic retrograde cholangiopancreatography (ERCP), the inside of the stomach and duodenum is seen through an endoscope, and radiographic contrast which can be seen on X-rays is injected into the ducts and pancreas. The test helps confirm gall stones.
  • In video capsule endoscopy, a swallowed capsule containing a tiny video camera travels through the small intestine and sends video images of the lining of the small intestine that are downloaded and studied on a computer. This test is superior in identifying the early stages of Crohn's disease.
  • Narrow band imaging is a novel endoscopic technique which can be incorporated during gastroscopy especially if there is a lesion suspected to be malignant or pre-malignant. It uses special filters and magnifying methods to diagnose early cancerous or pre-cancerous lesions.

6. Abdominal ultrasound, CT scan and MRI

An ultrasound is a diagnostic medical procedure that uses high frequency sound waves to produce dynamic (or real-time) images of internal organs, tissue and blood vessels. Abdominal ultrasound is used to examine organs and their blood vessels in the abdomen like liver, pancreas, gallbladder, etc.

Computerized topography (CT) scan is a computerised X-ray technique that combines a large number of X-ray images taken in succession. These images then result in a cross sectional view of the internal organs which helps analyse the internal structures of the body. It can be used to examine the GIT for diagnosing traumatic injuries, tumours or an infection.

In magnetic resonance imaging (MRI), a beam of radio waves and magnetic fields is sent through the body to detect a defect in the organ of interest. It gives an accurate image of the organ and structures within, thus helping in getting a clear idea of cancerous cells and the extent of the growth.

7. Barium X-ray

In barium X-ray, a chalky liquid called barium is used which is visible on an X-ray. When ingested, the barium can help view the stomach and the small intestines on an X-ray. When administered rectally as enema, the colon and terminal ileum can be viewed on X-ray. This test helps diagnose gut narrowing, fistulae, ulcerations, etc.

8. Manometry

Manometry uses a device called a manometer to measure muscle pressure and movement. Oesophageal manometry measures the symmetrical contraction and relaxation (peristalsis) of oesophagus and relaxation of lower oesophagal sphincter in the evaluation of achalasia. The lack of oesophagal peristalsis and failure of the LES to relax during swallowing is disclosed during this test. Anorectal manometry is used to measure contractility of the anal sphincter to evaluate anal incompetence and faecal incontinence.

9. pH Monitoring

Esophageal pH monitoring measures the amount of stomach acid that enters the oesophagus during a 24-hour period. It is used to diagnose GERD. It also helps determine the effectiveness of the prescribed medications. During the test, a thin tube with a sensor is passed through the nose and positioned in the oesophagus just above the lower oesophageal sphincter that is present at the junction of the oesophagus and stomach. The acid level in the oesophagus is recorded on a monitor. The data gathered in 24 hours is downloaded into a computer and analysed. A wireless capsule that is placed using an endoscope may be used instead of the tube. It sends recordings through wireless transmission.

10. Breath Test

The hydrogen breath test measures hydrogen in the breath to diagnose GI conditions like lactose intolerance, etc. When ingested sugars are not completely absorbed by the small intestine, bacteria within the colon produce hydrogen gas. Bacterial overgrowth in the small intestine can also produce large amounts of hydrogen. Hydrogen gas absorbed into the blood travels to the lungs. The test analyses the breath at regular intervals to detect this hydrogen gas that is breathed out. The patient will be asked to breath before drinking milk and then samples are taken after fixed intervals to determine hydrogen levels in your breath. If you are lactose intolerant, breath levels of hydrogen will be high as compared to normal levels.

Urea breath test helps diagnose peptic ulcer. The test looks for presence of Helicobacter pylori bacteria in the stomach. Normally, the body produces urea from excess nitrogen-containing chemicals and eliminates it in the urine. H. pylori bacteria breaks down urea into ammonia and carbon dioxide. Carbon dioxide thus produced is absorbed from the stomach and exhaled. During the urea breath test a urea tablet containing radioactive carbon is swallowed. Presence of radioactive carbon dioxide in the exhaled air indicates the presence of H. pylori bacteria.

11. Transient Elastography

Diseased livers are stiffer than healthy ones. Transient elastography is a non-invasive test that records the elastic properties of liver and helps quantify liver fibrosis. During the test, a small transducer passes 50-MHz wave into the liver through a probe. The velocity of the shear wave (in meters/second) as it passes through the liver is measured. The measurement is then converted into liver stiffness (in kilopascals).

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