There has been a revolution in investigative procedure during recent years with the availability of ultrasound imaging, computed tomography, radioisotope scanning, percutaneous transhepatic cholangiography (PTC), upper gastrointestinal endoscopy using flexible fiber optic endoscopes, colonoscopy and retrograde endoscopic pancreatic cholangiography (ERPC).
Majority of these procedures are atraumatic. Most of them are, however, expensive and demand sophisticated technology and are not freely available. These tests can only be carried out at specialized centres. In a developing country like India, it will probably take a long time for these tests to be freely available but it is considered important that all medical students and practitioners should know about them and their value in diagnosing difficult cases.
1. Ultrasound Imaging or Scanning USS:
Once the equipment is available, it is one of the most painless, relatively inexpensive and atraumatic investigations. It can be done as an out-patient and takes a very short time. The results depend, of course, on the quality of the machine and expertise of the person using it. It is easy to make wrong interpretation due to inexperience.
The procedure has got no contraindications, although excessive gas in the abdomen may not allow proper imaging. It is especially in the diagnosis of gastrointestinal diseases related to liver, gall bladder and pancreas.
Some of the indications for ultrasonography have been summarized as below:
(1) Delineation of abdominal masses and their relationship to different abdominal viscera. It also helps to detect cystic or solid S.O.L.
(2) Confirmation of hepatomegaly and splenomegaly.
(3) Demonstration of space occupying lesions in the liver and their nature whether solid or cystic. It is particularly useful in diagnosing metastases in the liver, liver abscesses and hepatic cysts.
(4) Aspiration of liver abscesses and liver biopsy from a particular site under ultrasonographic guidance.
(5) Study the effects of treatment by watching the size of the lesion and its regression during frequent follow-up examinations.
(6) Guided aspiration biopsy from different abdominal organs or masses.
(7) Diagnosis of portal hypertension and confirmation of patency of portal vein. One can also confirm whether a Porto-systemic shunt is patent or not.
(8) Demonstrate even small cysts, SOL’S and abscesses.
(9) Supports the presence of congestive heart failure by demonstrating dilated hepatic veins and inferior vena cava.
(10) Demonstration of gall bladder and biliary duct diseases. The availability of latest real-time gray-scale ultrasonographic equipment has made ultrasonography as the primary investigation for demonstration of gallstones. It is as accurate as oral cholecystography, can be performed rapidly and is cost-effective.
It can be used in acutely ill and jaundiced patients and the patient is not exposed to ionic radiations. Accuracy of this procedure in demonstrating gallstones is 95-99 per cent.
(11) It is a very safe and most direct method to detect biliary tract obstruction and differentiates extra hepatic from intra hepatic jaundice. It may also indicate the site of obstruction and helps in aetiological diagnosis. However, it is not always possible to diagnose the precise aetiology by ultrasonography.
(12) Study of pancreatic disorders – Ultrasonographic examination of the pancreas is performed to help in diagnosis of pancreatitis and its complications like pseudo-pancreatic cyst and detection of pancreatic carcinoma. It is not, however, always possible to examine pancreas ultrasonographically and computed tomography and ERCP should be done in such doubtful cases.
(13) Study of alimentary tract – Ultrasound has still not been found to be of much use in study of alimentary tract because luminal gas is a physical barrier. Contrast barium studies will continue to be the main diagnostic tool in these cases. However, modern flexible endoscope is an additional and very effective tool.
2. Computed Tomographic (CT) Scanning:
Availability of whole body computed tomography (CT Scan) has generated an interest in investigation of gastrointestinal diseases. Its main advantages are superb density and spatial resolution of images. It is non-invasive, exposes the body to less radiation than a barium enema and is fairly rapid.
The major limitation, however, is the cost and its limited availability.
The major uses of CT scan in gastrointestinal diseases are in:
(i) Diagnosis of liver, pancreatic, splenic and gastrointestinal diseases
(ii) Staging of malignant disorders
(iii) Planning of treatment
(iv) Assessing response to therapy
(v) Guiding biopsies and drainage.
The greatest advantage of CT Scan is that it can image the entire abdomen at one sitting and hence too many investigations for different organs are not required.
3. Radionuclide Imaging or Scanning:
Large variety of radiopharmaceuticals are used. There has been tremendous improvement in radio isotopic imaging technology in recent years, particularly in the field of gastroenterology. These studies are very safe, non-invasive and exposure to radiation is more or less the same as in case of any standard radiological examination.
The radionuclide is given in a tracer dose orally or intravenously and quantitation is done by external monitoring with a scintillation camera. Availability of computer system to help in analysis of results has further simplified and improved the technique.
The different radiopharmaceuticals used are – I-131 rose bengal, Au 198 gold colloid, Tc99m sulphur colloid (most commonly used at present technetium 99m and Gallium 677).
The main clinical conditions where radionuclide scanning may be of help are:
(a) Evaluation of liver-splenic size, contour, location, uniformity of colloid distribution and presence of ‘Cold’ lesions.
(b) Evaluation of Hepato-Cellular Disease:
(i) Nonhomogeneous colloid distribution
(iv) Increased uptake of colloid by spleen and bone marrow
(c) Evaluation of Space Occupying Lesions in the Liver:
(i) Hepatic metastases
(ii) Hepatic cysts (ultrasonography is adequate)
(iii) Liver abscesses (ultrasonography is adequate)
(iv) Primary hepatocellular carcinoma
(d) Hepatobiliary Imaging:
It is particularly useful in diagnosis of acute cholecystitis, evaluation of cholestasis and biliary tract abnormalities.
(e) Detection and localization of site of bleeding in gastrointestinal tract.
(f) Evaluation of gastrooesophageal reflux.
4. Upper Gastrointestinal Fiberoptic Endoscopy:
Fiber optic endoscopes are made up of two types of fibre bundles — one carries light down to illuminate the visual field and the other carries the undistorted image back to the examiner’s eye. The shaft also contains wire control for multidirectional movement of the tip. One or more separate channels are available for suction and biopsy. This gives an excellent view of all mucosal surfaces of the oesophagus, stomach and duodenum.
Observations can be made regarding presence of focal benign or malignant lesions diffuse mucosal changes, motility, intraluminal obstruction, or extrinsic compression. Along with providing direct visual impression of the pathology, there is provision for taking directed biopsy for histopathology from suspicious lesions. Material for cytological examination can also obtained.
In addition to being used in diagnosis, recently fiberoptic endoscopes are being used more frequently for therapeutic procedures such as dilatation of benign oesophageal strictures, removal of foreign bodies and treatment of upper gastrointestinal bleeding. The greatest advantages over rigid endoscopy are case of introduction without anaesthesia, greater and hence better diagnostic efficacy and minimal complication rate.
Main complications include rarely perforation, bleeding and medication reactions, cardiopulmonary failure and very rarely. As compared to radiology of upper ‘GT tract’, this technique is more sensitive and specific for diagnosis of upper GI lesions. With single contrast barium studies done in good centres the correct diagnosis is obtained in 60-70% of upper GI lesions as compared to 98-100% with fiberoptic endoscopy.
With double contrast and combination of double contrast mucosal relief views followed by single contrast Ba-examination the success rate in diagnosis goes up to 85-90%. But this technique takes longer time, requires special expertise and there is more radiation danger.
5. Fiber Optic Colonoscopy:
This is an important diagnostic and therapeutic adjunct for the management of colonic diseases. Diagnostic colonoscopy is useful in diagnosis of abnormal or equivocal barium enema findings, unexplained rectal bleeding, to evaluate the complications of inflammatory bowel disease, surveillance for development of carcinoma in inflammatory bowel disease.
A direct biopsy of the lesion as well as cytology-material by brush can be obtained. The most useful therapeutic technique is colonoscopic polypectomy. In some instances haemorrhage from vascular lesions can be controlled by colonoscopic electro or photo-coagulation. A thorough cleaning of the large gut is required prior to performing colonoscopy. In hands of expert, caecum can be reached in 85-95% of cases.
6. Endoscopic Retrograde Cholangiopancreatography (ERCP):
This employs fiber optic endoscopy and techniques of radiography in the study of biliary and pancreatic diseases. Side-viewing endoscope is used. After entering the second part of the duodenum, ampulla of Vater is located and cannulated and desired duct system, either pancreatic or bile ducts can be outlined by injecting contrast media through the endoscopic catheter.
It requires both endoscopic and radiographic skills. It is a fairly safe procedure in expert hands with a success rate of 82 to 93 per cent. But it is a costly procedure and requires plenty of technical expertise. It has made the diagnosis of pancreatic and biliary diseases easier. Evaluation of biliary tree is mostly required in cases of obstructive jaundice whereas evaluation of pancreatic duct is indicated in cases of chronic pancreatitis and carcinoma of pancreas.
Therapeutically ERCP is used for performing sphincterotomy and removal of retained stones from common bile duct. It can also be used for introducing an endoprosthesis across malignant bile duct strictures. Complication rate is about 3%. In addition to medication reaction, complications of endoscopic procedure these include development of acute pancreatitis and cholangitis.
7. Percutaneous Transhepatic Cholangiography (PTC):
This is another important diagnostic aid in visualizing biliary tree in addition to ERCP. In fact details of biliary tree are better delineated with this method. With the advent of Chibas needle which is fine and flexible, the procedure has become very safe. The needle is introduced percutaneously through the intercostal space into the liver.
The stylet is withdrawn, contrast material is injected slowly as the needle is withdrawn until the ductal system is entered. This whole procedure is done under fluroscopic control. After proper positioning of the patient and manipulating in different positions, radiographs of the whole ductal system are taken to delineate the site of obstruction. In obstructed biliary system the success rate is 90 to 100%. In non- -obstructed biliary tracts the success rate has been in the range of 75 to 80%.
Complications of the procedure include bile peritonitis, haemorrhage and septicaemia. Coagulation parameters must be normal before performing PTC as is the case with all invasive, investigations on liver. In suspected biliary obstruction, antibiotics should be started one day prior to procedure. PTC can also be used for external or internal drainage of bile in obstructed biliary duct prior to life in malignant structures.