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Methods of Examination 3 ñòðàíèöà






A spectrum of certain isoenzymes is typical for affection of separate organs. For example, of the five isoenzymes of lactic dehydrogenase, the fifth fraction (LDG5) is regularly increased in chronic hepatitis and cir­rhosis of the liver, while the increase in the LDG! is characteristic of myocardial infarction. Determination of isoenzymes of aldolase, aspartate aminotransferase, leucine aminopeptidase, and of some other enzymes is also important.

Changes in the activity of organospecific enzymes, i.e. the enzymes characteristic only of liver cells, are even more informative: their activity changes only in pathology of the liver. These enzymes are ornithine car-bamoyl transferase and arginase taking part in the synthesis of urea, sor-bitol dehydrogenase catalysing oxidation of sorbitol to fructose, guanine deaminase catalysing conversion of guanine to xanthine, quinine oxidase oxidizing quinine, etc.

Transaminases are the enzymes catalysing the transfer of the amino group from amino acids to keto acids. Among them diagnostically impor­tant are aspartate aminotransferases (AsAT, glutamino-oxalo-acetic acid transaminase) and alanine aminotransferase (A1AT, glutaminopyruvic transaminase). Although their increasing activity is a non-specific sign because it is observed in liver diseases and generally in their diffusion from injured tissues (e.g. myocardium, kidneys, pancreas), their activity may nevertheless be very high in myocardial infarction and hepatitis. A1AT dominates in hepatitis, and AsAT in myocardial infarction. The main im­portance of the test is that activity of both transaminases increases significantly during non-icteric period of acute hepatitis (Botkin's disease). This facilitates its early diagnosis and also identification of non-icteric forms of hepatitis.

The content of aldolase (fructose 1, 6-phosphate aldolase) increases markedly in the blood serum of patients with liver diseases. Hyperaldolasaemia regularly attends epidemic hepatitis and the test for aldolase is therefore obligatory for diagnosis of the disease.

Alkaline phosphatase is the enzyme hydrolysing esters of phosphoric acid. It is mostly formed outside the liver but is excreted by this organ. The increase in the activity of the blood alkaline phosphatase is especially pro­nounced in obstructive jaundice, due to malignant tumour, and also in in-trahepatic cholestasis, and biliary cirrhosis. In patients with the affected liver parenchyma, the activity of this enzyme increases moderately.

Serum cholinesterase (pseudocholinesterase) splits acetylcholine and other choline esters. It is formed in the cells of the liver parenchyma. Its



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determination is of great prognostic importance: the lower the activity of pseudocholinesterase in hepatitis, the more severe is the course of the disease.

Detoxicating function of the liver. Blood of the portal vein supplied from the gastro-intestinal tract contains various toxic substances for which the liver imposes a barrier. These substances are retained by the liver and almost completely detoxicated by the enzymes responsible for oxidation, reduction, deamination, hydrolysis, methylation, combination with sulphuric acid, glucuronic acid, and with glycine. These reactions give less toxic or more readily soluble substances that can be excreted in the bile or urine. Ammonia, for example, is converted into less toxic urea, free bilirubin combines with glucuronic acid to turn into a less toxic and water-soluble compound that can be excreted in the bile and urine. Phenols, in-doles, ketones, alcohols, sulpha preparations, amidopyrine, camphor, and morphine are detoxicated mainly by combining with glucuronic or sulphuric acid; sodium benzoate combines with glycine; santonin oxidizes to oxysantonin; metals react with nucleoproteins. Stellar reticuloen-dotheliocytes retain and phagocytise microbes.

Sodium benzoate test. Sodium benzoate is given per os or intravenous­ly. It combines with glycine in the liver to give hippuric acid which is ex­creted in the urine. The detoxicating function of the liver is assessed by the percentage of urine-excreted sodium benzoate in the form of hippuric acid. If the liver parenchyma is affected, synthesis of hippuric acid is disturbed and its excretion is slowed. The test has some disadvantages: it precipitates in obstructive jaundice, tumours, fevers (positive test), and requires nor­mal renal function.

Excretory function of the liver. Among substances to be excreted from the body are water-soluble compounds that are excreted mainly by the kidneys, and water-insoluble or protein-bound compounds that are ex­creted by the liver. The normal hepatic excretory capacity is restricted. In significantly intensified haemolysis, a healthy liver cannot excrete all bilirubin from the blood where it thus accumulates. Parenchymal affec­tions decrease the excretory capacity of the liver to cause, for example, bilirubinaemia, which however is not an obligatory symptom. In order to reveal the disordered excretory function of the liver, especially in non-icteric affections, tests are used with administration into the blood of substances that should be excreted with bile.

Bilirubin test is most informative: after an intravenous injection of 50 mg of bilirubin, its content in the blood is determined in 5 minutes and in 4 hours. If excretory function of the liver is normal the pigment concentration decreases in 4 hours to 15 per cent of its concentra­tion as determined in 5 minutes after the injection. The test is not however used universally because of expensiveness of the preparation and uselessness of the test in the presence of jaun­dice.


The bromsulphthalein test is one of the most specific. Brom-sulphthalein is given intravenously (5 mg/kg body weight) and the first specimen of blood is taken in 3 minutes (when the concentration of the preparation in the blood attains its maximum). Another specimen is taken in 45 minutes after the injection. Concentration of bromsulphthalein is determined colorimetrically: it turns red-violet when alkali is added. If the liver function is adequate, the preparation concentration in the blood in 45 minutes does not exceed 5 per cent of its initial concentration, which is assumed to be 100 per cent. The stain can be detected in the bile in 15 minutes after the injection. The test is very sensitive: even insignificant hepatic dysfunction that cannot be detected by other methods is revealed by the bromsulphthalein test.

Indocyanine green test is based on the same principle. The preparation is given intravenously in a dose of 0.5 mg/kg. Normally, not more than 4 per cent of the injected stain remains in the blood in 20 minutes. The test is more sensitive than that with bromsulphthalein.

The number of tests for the liver function is great. But clinicists are not satisfied by merely stating this or that type of metabolic disorder without relating them to the provoking changes occurring in the liver. There is therefore a tendency to unite groups of pathologically altered test results into syndromes characteristic of various pathologies. For example, when bile drainage is disordered, the concentration of cholesterol, bile acids, bound bilirubin, alkaline phosphatase, and copper in the blood increases. The combination of these positive tests gives the syndrome of cholestasis. The syndrome of hepatocyte insufficiency is characterized by decreased concentration in the blood of substances synthesized by hepatocytes: serum albumins, cholesterol, prothrombin, etc. Inflammatory changes in the liver are characterized by an increased content of various globulin fractions pro­duced by reticulohistiocytary elements of the liver. This is revealed by a number of positive protein sedimentation tests (the inflammatory syn­drome). These syndromes can bring the physician closer to understanding of prevailing pathological processes occurring in the liver.

STUDY OF DUODENAL CONTENTS

Duodenal contents are studied for determining the bile composition, which in turn is necessary to diagnose affections of the gall bladder and bile ducts, and also to estimate the function of the pancreas.

Technique. Duodenal contents are obtained by probing the duodenum by an elastic rubber tube 3—5 mm in diameter. The oval bulb at the end of the tube opens into its lumen. The overall length of the tube is about 150

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cm. The tube bears a mark at a distance of 45 cm from its distal end (the distance to the stomach); next marks follow at 70 and 80 cm lengths.

The procedure is carried out on a fasting stomach. The patient sits with the mouth slightly open. The tube is placed in the mouth so that the bulb is at the root of the tongue and the patient is asked to make swallowing movements. The operator should only slightly promote the independent movement of the tube. If the patient attempts to vomit, he is recommended to breathe deeply through the nose. In rare cases the throat and the upper oesophagus are anaesthetized. When, according to the marks, the tube reaches the stomach, its position is verified by aspiring the stomach con­tents with a syringe which is inserted into the outer end of the tube: extrac­tion of a slightly turbid acid fluid shows that the tube is inside the stomach. The fluid may be coloured yellow by the duodenal contents, but the reac­tion remains acid. The patient is now placed on his right side so that the tube bulb would be directed (by gravity) toward the pylorus. A soft pad is placed under the patient's pelvis. The patient continues swallowing the tube to the mark of 70 cm. Breathing should be through the mouth. The tube end passes the pylorus and enters the duodenum in about 60—90 minutes (sometimes even later). The outer end of the tube is lowered into a test tube in the stand placed on a low stool at the head-end of the bed. Sometimes the tube passes the pylorus in a shorter time if the patient walks slowly about for 15-20 minutes and continues the swallowing movements. When the tube is swallowed to the mark of 70 cm, the patient lies on his right side. If the bulb has reached the duodenum, yellow alkaline fluid is gathered in the test tube. If the common bile duct is obstructed (pronounc­ed jaundice) the duodenal contents are colourless and the reaction is alkaline. In order to check the position of the tube end (if no juice is discharged from the probe) air can be forced into the tube by a syringe. If the probe is inside the stomach, the patient feels the stream of the injected air, and bubbling can be heard. If the tube is in the duodenum, the patient does not feel anything and no sounds are heard. The position of the tube can most accurately be established by X-rays. The correct position of the tube bulb is between the descending and the lower horizontal portions of the duodenum. If the tube is stopped before the pylorus, the patient is given to drink a warm solution (2—3 g) of sodium hydrocarbonate in 10 ml of water.

The normal duodenal contents discharged from the tube (the first phase of examination) is golden-yellow, slightly viscous, clear, and opalescing. If it contains gastric juice, it becomes turbid from precipitating bile acids and cholesterol. This portion is designated by the letter A. This is a mixture of bile, pancreatic and intestinal secretion. Their proportion in the mixture is unknown and the diagnostic value of this fluid is therefore low. Bile A is


collected for 10-20 minutes. An agent stimulating contraction of the gall bladder is then given through the tube. This is usually a warm solution of magnesium sulphate (25-50 ml of 25-33 per cent solution). Less frequent­ly this is vegetable oil, egg yellow, 10 per cent sodium chloride solution, 30-40 ml of a 40 per cent glucose solution or 40 per cent sorbitol solution, and also hormones (cholecystokinin or pituitrin) which are given sub-cutaneously.

Following the administration of the stimulant into the duodenum, the Oddi sphincter contracts and excretion of bile is discontinued. This is the second phase. Normally it continues 4—6 minutes following the ad­ministration of magnesium sulphate and about 10 minutes after ad­ministration of olive oil. The phase is elongated if the tone of the Oddi sphincter is increased and shortened in its hypotonia. Next follows the third phase, the excretion of golden-yellow contents of the bile duct and the neck of the gall bladder (portion At). The fourth phase is evacuation of the gall bladder, which is attended by discharge of thicker dark-yellow, brown or olive bile. It is greenish when congested or if the gall bladder is inflamed. Portion B is the bile of the gall bladder, whose secretion is associated with positive Meltzer-Lyon reflex: contraction of the gall bladder concurrent with relaxation of the bladder sphincter and Oddi sphincter. Bladder bile (B bile) is a kind of concentrated liver bile. The wall of the gall bladder has selective absorbability: the sodium ion and water are absorbed especially actively. Ions of potassium, calcium, and chlorine are absorbed much slower. As a result, the content of bile acids and their salts increases 5—8 times, and that of bilirubin and cholesterol 10 times compared with their content in the hepatic bile (C bile). Epithelium of the gall bladder secretes mucin whose concentration in B bile is from 1 to 4 per cent. In accordance with the capacity of the gall bladder, the amount of secreted B bile is 30-60 ml during 20—30 minutes. The bladder reflex may sometimes be absent in healthy subjects after administration of magnesium sulphate, but it usually appears in repeated examinations, or after giving vegetable oil, pituitrin, or atropine (subcutaneously). The appearance of the reflex after giving pro-caine or atropine indicates spasm of the sphincter and the absence of organic obstacles. Persistent absence of the bladder reflex is observed in cholelithiasis, cirrhosis of the gall bladder, obstruction of the bile duct with a stone or an inflammatory process in its mucosa, in contractile dysfunc­tion of the gall bladder, etc. Excretion of very thick dark bile or ample amounts of bile indicates its congestion in dyskinesia of the bile ducts. In­tensification of colour alone indicates haemolysis (excess secretion of bilirubin).

After B bile excretion discontinues, C bile (hepatic bile) is delivered from the tube. This is the fifth phase of the examination. The golden-


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1 J


yellow C bile is considered to be hepatic though it also contains admixtures of duodenal juice. Five-minute portions are collected separately during the entire examination. This fractional duodenal probing is used to determine the properties of the contents, volumes of separate portions of the bile system, and the tone of its sphincters. All the three portions of bile are studied by microscopic, chemical and sometimes bacteriological methods.

Microscopy of duodenal contents should be carried out immediately after collection of each portion. Leucocytes are decomposed more slowly but their breakdown is still very rapid. If the sample of bile cannot be ex­amined immediately corrosive sublimate or a 10 per cent formaldehyde should be added (with warming up). But these reagents distort the cells and kill lamblia. Flakes of mucus are pipetted from the bile and transferred on­to an object glass. The remaining liquid is centrifuged and the precipitate (as well as the flakes) is examined in native preparations.

Untill recently, the presence of leucocytes in bile was given great diagnostic importance. Their presence in B bile was considered as a diagnostic sign of cholecystitis, and in C bile of cholangitis. If the leucocytes were impregnated with bile (coloured by bilirubin), this was con­sidered a proof of their genesis from the gall bladder. At present, many in­vestigators believe that accumulations of round cells in bile are actually altered and rounded nuclei of intestinal epithelium. Their combination with bilirubin depends probably not on the place of their origin but on the thickness of mucous coat that protects them. Diagnostic importance can therefore only be given to the presence of leucocytes in bile after their iden­tification (by peroxidase staining). Epithelium can be quite informative provided it is well preserved and its properties can be indicative of the site of its origin: fine prisms originate from the bile ducts, elongated columnar cells with oblong nuclei originate from bile passages; large cells with a large round nucleus and vacuolized cytoplasm are attributed to the mucosa of the gall bladder; large epithelial cells with a round nucleus, accounting for the expanded lower third of the cell, and with a thickened cuticle, belong to the duodenum. The cells can easily be identified in the native preparation by phase-contrast microscopy.

The presence of tumour cells in bile is of great diagnostic importance. Microscopy of native preparations only in rare cases can reveal them. Histological study of consolidated duodenal precipitate is more infor­mative.

Discovery of cholesterol crystals and brown grains of calcium bilirubinate are of importance. They can be found in small quantities in healthy subjects but large amounts suggest cholelithiasis.

Discovery of parasites in bile is of great significance. Lamblia in-testinalis occur frequently; the eggs of liver fluke or Chinese fluke, eggs of


duodenal wryhead and also larvae of intestinal Strongyloides stercoralis are found less frequently.

Some chemical constituents of bile are determined. These are bilirubin, cholesterol, bile acids, and protein. It is not the total bilirubin of bile that is important, but rather bilirubin proportion in C and B bile, which characterizes the concentration capacity of the gall bladder. The normal bilirubin content in B bile is 3.4-6.8 mmol/1 (200-400 mg/100 ml) and of C bile, 0.17-0.34 mmol/1 (10-20 mg/100 ml). Decreasing concentration of bilirubin in the gall bladder can depend on bile dilution with inflam­matory exudation. Concentration of bilirubin is determined by the icterus index: bile is diluted to match its colour with that of a standard solution of potassium dichrornate. The degree of dilution indicates " units of bilirubin". Cholesterol is determined as in the blood. A bile contains about 0.5 mmol/1 (20 mg/100 ml), B bile about 2.6-23.4 mmol/1 (100-900 mg/100 ml), and C bile 2-2.6 mmol/1 (80-100 mg/100 ml) of cholesterol. Protein is absent from the normal bile. Its presence (proteincholia) in­dicates inflammation.

Bile acids are determined colorimetrically using the Pettenkofer test (and its modifications) based on the interaction between bile acids and sucrose in the presence of sulphuric acid and subsequent development of cherry-red colour. There are more accurate, though more complicated methods for determining bile acids. These are chromatographic, luminescence and other methods. Decreasing the cholate to cholesterol ratio below 10 in bile (the cholatocholesterol coefficient) indicates predisposition to formation of bile stones.

The ability of the liver to excrete foreign substances together with bile (stains, medicines, iodine compounds, salts of heavy metals) is used for diagnostic purposes. Patency of bile ducts is determined by the speed of ex­cretion with bile of bromsulphthalein given intravenously. If the concen­trating capacity of the gall bladder is impaired, it is difficult to differentiate between A, B and C biles by colour. A methylene blue test (chromodiagnostic probing) is then used. The reagent is reduced in the liver to a colourless leucobase, but it again oxidizes in the gall bladder and its colour reappears. The patient is given 0.15 g of methylene blue in a cap­sule in the evening and common probing is performed in the morning. If blue bile is discharged after giving magnesium sulphate, this indicates that it is B bile.

Bacteriological study of bile is only of relative importance because it is difficult to establish the origin of the cultured flora (it may originate in the mouth, the intestine, or the bile ducts). But if the same flora is found in repeated studies of the same portion of bile, it can be suggested that the found microbes may originate in the bile ducts.



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X-RAY STUDY

Survey roentgenoscopy and roentgenography of the liver and gall blad­der are not diagnostically important because the increased density due to consolidated liver tissue can hardly be differentiated from shadows of the other abdominal organs. Therefore only in rare cases (usually in thin and asthenic patients) it is possible to determine the lower border of the liver, its position, configuration, and the size of the liver and the spleen. In some cases X-ray examination can reveal inclusions in the liver tissue (calcified echinococcal cysts, tuberculous foci), in the gall bladder and bile passages (stones containing much calcium salts).

Various X-ray techniques have been proposed during the past decade to study the liver vessels with contrast substances. Splenoportography is most widely used now. This is the method by which the splenic vein and portal vein with its intrahepatic ramifications can be determined with contrast substances and with serial radiography. The patient is given local anaesthesia and the spleen is punctured in the 8th and 9th intercostal spaces in the left midaxillary line to administer 40—50 ml of a contrast substance (70 per cent solution of cardiotrast or triombrin). Series of X-ray pictures are then taken in 2, 5, 10, 20, 35, and 45 seconds, which are used for com­bined examination of the portal circulation and the condition of the bile-secretion system. A splenoportogram gives a distinct picture of branching veins. Their section and the pattern of branching can be used to judge about intra- and extrahepatic causes of portal hypertension, the develop­ment of collateral circulation, the character of extension and the degree of pathology of the liver (cirrhosis, primary and metastatic tumours, cysts). Splenoportography is especially indicated in cases of portal cirrhosis of the liver with ascites, when the patient is offered an operation for placing a portocaval anastomosis to bypass a part of blood outflow from the portal vein into the inferior vena cava and to decrease the degree of portal hypertension. The presence of portal hypertension can be established in­directly by contrast X-ray study of the oesophagus (using barium meal). It reveals varicosity of the oesophageal veins.

The arterial system of the liver is examined by coeliacography, the method based on the administration of a contrast substance into the coeliac artery through a catheter, which is usually passed into the coeliac artery through the femoral and then abdominal artery, and then the abdominal aorta. This method reveals foci of liver affection (primary and metastatic tumours, cysts, and abscesses).

All X-ray studies should be carried out only for special indications with proper consideration of all possible contraindications (acute diseases of the liver, haemorrhagic diathesis, hypersensitivity to iodine preparations, etc.).


 


Fig. 95. Cholecystogram with gall stones.

Peroral cholecystography and intravenous cholangiography are widely used to study the gall bladder and bile ducts. Cholecystography is based on a peroral administration of iodine-containing contrast substance, e.g. bilitrast (3—3.5 g) or iopanoic acid (cholevid) in a dose of 3—6 g for one ex­amination. The contrast substance is given after a light early supper. The substance is absorbed in the intestine, trapped by the liver, and secreted with bile to enter the gall bladder, where iodine is gradually accumulated. Next morning, the patient with a fasting stomach is given an X-ray ex­amination of the gall bladder. A distinct shadow of the gall bladder can be seen 10-15 hours following the intake of the contrast substance; this in­dicates normal concentration function of the gall bladder. If this faculty of the gall bladder is impaired, or if patency of the cystic duct is obstructed, the shadow of the gall bladder is absent from the X-ray picture. In the presence of stones the shadow is non-uniform and areas of rarified density



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Chapter 7. Digestive System



 


can be seen, their number and size corresponding to the number and size of the stones (Fig. 95). If the shadow of the bladder is free from stones, the next stage of examination is begun: a cholecystokinetic (usually 10 ml of raw egg yellow) is given to the patient. The preparation provokes contrac­tion and evacuation of the gall bladder. Series of pictures taken at regular intervals are used to assess the motor function of the gall bladder (by the time of its evacuation and the size of the maximum contracted gall bladder).

A contrast substance, bilignost, is given in cholangiography (30-40 ml of a 20 per cent solution, a slow intravenous injection). If the patient's con­dition is normal, radiographs taken 5-10 minutes after the injection show large intra- and extrahepatic bile ducts and the gall bladder (provided the bile duct is patent). Cholangiography reveals not only the shadow of the gall bladder and areas of rarified density in the presence of stones, but also gives information on the position, calibre, and patency of the intra- and ex­trahepatic bile ducts. Cholangiography is used to study the intra- and ex­trahepatic bile ducts (e.g. in patients with removed gall bladder) and also the gall bladder in patients in whom the shadow of the bladder is not deter­mined by cholecystography.

Advances in endoscopic technique have made it possible to work out a method of endoscopic (retrograde) cholangiopancreatography. An iodine-containing contrast substance is administered into the common bile duct and the pancreatic ducts (by catheterization of the major duodenal papilla during duodenofibroscopy) which is followed by radiography. This method is used to determine the presence of stricture of the common bile duct, its compression from outside, and to reveal stones in it.

RADIOISOTOPE METHODS OF STUDY

Radioisotope studies of the function and structure of the liver are based on tracing the distribution and motion of radioactive substances inside the human body. Short-lived isotopes are usually used in clinical practice to label certain mineral and organic substances that are selectively absorbed by various cells of the liver tissue.

The following preparations are mostly used now: rose bengal (dichlortetraiodofluorescein) labelled with 13II, which is captured by the liver hepatocytes, and the colloidal solution of gold 198Au, captured by the reticulohistiocytic cells of the liver, spleen, and bone marrow.

Radioisotope hepatography is performed with rose bengal labelled with 131I. Its sterile solution (from 15 to 20 /xCi) is given intravenously in 0.5-0.9 ml of sterile isotonic solution of sodium chloride. The liver func­tion is then examined by a radiometric apparatus whose scintillation


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transmitters are fixed over the heart region (to determine stain withdrawal from the blood; blood clearance), over the right lobe of the liver (to deter­mine stain accumulation and withdrawal), and the central part of the ab­domen (to control stain discharge via the bile passages to the intestine). Changes in radioactivity over these areas are recorded for 60-90 minutes, and in some cases (in obstructive jaundice, various forms of liver cirrhosis) the time of examination can be prolonged to 24-72 hours. The results are presented graphically as hepatograms (Fig. 96).

In healthy subjects, the half-period clearance (the time of blood clearance from 50 per cent stain absorbed by the liver) is from 10 to 15 minutes. During the first two minutes following injection of the stain, radioactivity of the liver increases sharply to characterize the condition of its blood flow. Further absorption of the stain by the liver is slow. The time of maximum accumulation of the stain in the liver is normally 16-22 minutes. The time during which half of the stain is released from the liver to the gall bladder and the small intestine (period of half-clearance) varies between 75 and 110 minutes. Not more than 2.5 per cent of the initial amount of the preparation remains in the liver in 24 hours. Radiohepatography can thus assess blood circulation in the liver, the absorption-excretion function of the liver, and patency of the bile ducts.


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