Rectosigmoidoscopy and colonoscopy

Rectosigmoidoscopy is a direct visualization of the mucosa in the rec­tum and the sigmoid colon. A sigmoidoscope is a 35 cm-long metal tube, with a diameter of 2 cm. A metal mandrin (obturator) passes the lumen of the tube. The outer end of the tube is closed by a tightly screwed disc with, a glass window through which the physician observes the intestine. The outer surface of the instrument is graduated in centimetres so that the depth of penetration of the instrument could be read off. Air is used to inflate the collapsed intestine. The lower end of the large intestine is preliminarily emptied by giving a cleansing enema 1—2 hours before rec­tosigmoidoscopy. The patient assumes either a knee-chest position or lies on his left side with the legs flexed on the abdomen. The instrument is first introduced at a right angle to the plane of the rectal entrance and then the direction is slightly changed posteriorly, toward the sacrum, along the course of the large intestine. When the tube is passed to the depth of 6—8 cm, the obturator is removed and an electric lamp introduced instead. The outer end of the tube is then closed tightly with the " window" disc and an air cylinder is connected. Further progress of the tube is controlled visual­ly.

The instrument can be used to inspect the mucosa of the rectum and sigmoid colon to the depth of 35 cm. Normal mucosa is smooth, moist, and moderately red. In acute inflammation the mucosa is oedematous, opaque, and covered with mucus. Haemorrhage, erosions, ulcers, haemorrhoids, and fissures of the anus can also be seen. Rectosigmoidoscopy helps early diagnosis of cancer tumours in the rectum and the lower portion of the sigmoid colon. The instrument is provided with a special device for sighting biopsy for morphological studies. Finger examination of the rectum is only possible at depths of 6 to 8 cm.

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Chapter 7. Digestive System

A more complete endoscopy of the large intestine can be done with a colonoscope (endofibroscope), whose length is 86—186 cm. Because of high flexibility, it can be introduced through the anus to reach any portion of the large intestine. In addition to visual examination, the instrument can be used to take specimens of the intestinal mucosa for establishing a diagnosis.

COPROLOGICAL STUDIES

Analysis of faeces is an important item in the study of patients with diseases of the alimentary system.

Faeces of a healthy subject consist of about equal volumes of un­digested food remains, secretions of the alimentary organs and microbes (mainly dead ones). Faeces are studied to detect blood, ova of helminths, etc. General clinical analysis helps assess assimilation of food, discover disorders in the biliary secretion, latent haemorrhage, inflammation, the presence of parasites, etc. Coprology includes macroscopy, microscopy, and simple chemical analysis. Microbiological studies of faeces are necessary in cases suspected for infectious diseases of the intestine.

Faeces are collected in a dry clean container and studied as soon as possible (not later than 8-12 hours after defaecation, provided the specimen is kept in the cold). Faeces should be examined for the presence of protozoa immediately after defaecation. When faeces are examined for the degree of food assimilation, the patient is given a common diet (or a special diet for more detailed studies) several days before the study.

Macroscopy of faeces includes assessment of the amount of daily excre­tion, the colour of faeces, their consistency, shape, odour, presence of un­digested food remains, mucus, blood, pus, and parasites.

The normal daily excretion (with varied nutrition) is 100-200 g. The amount of faeces increases in ample vegetable diet, poor assimilation of food (in diseases of the pancreas), and intensified peristalsis. Faeces are meagre in proteinous diet, in constipations and hunger. Shapes of faeces depend mainly on their consistency. Normal faeces resemble sausage and are usually soft. In constipation faeces are hard, while in spastic colitis they resemble faeces of sheep (small nuts). The consistency of faeces depends largely on absorption of water in the intestine. Faeces are pasty when rich in fat.

Normal faeces are brown due to the presence of bilirubin derivatives (stercobilin and mesobilifuscin). In constipation, and also during antibiotic therapy, bilirubin is not reduced and faeces are golden-yellow. In cases with upset bile excretory function, faeces are greyish-white, clayish, or san­dy (acholic faeces). In the absence of acholia, fatty faeces are grey as well

(amyloidosis of the intestine, or sprue), but they darken on exposure to light and give a positive reaction to stercobilin. Black colour of faeces can be due to haemorrhage in the upper portions of the gastro-intestinal tract (formation of sulphur compounds of iron), due to ingested black currants, coffee, carbolen, preparations of bismuth, iron, etc. Other medicinal preparations and plant pigments are also important for the colour of faeces. The odour of faeces changes with intensification of fermentation (acid odour of organic acids) or putrefaction (putrid dyspepsia), especially in degradation of tumour of the large intestine.

Remains of undigested food are easier detectable in faecal emulsion in a Petri dish placed against a dark background. Remains of vegetable foods are usually found. In the insufficiency of gastric and pancreatic digestion, or in the absence of teeth, faeces usually contain otherwise readily digested food (lientery). Connective tissue remains undigested (in the form of whitish fibrous structures) in gastric achylia. Ample fat in stools (steator-rhoea) is characterized by the appearance of a solidified fat coat on the faecal surface.

The pathological components of stools, such as mucus, blood, and pus can be seen by an unaided eye if they originate in the large intestine. If these components join faeces in the small intestine, mucus is mixed with faeces, while leucocytes and erythrocytes are decomposed. Clots or bands of mucus found on the surface of faeces indicate inflammatory changes in the large intestine. In membranous colitis, mucus is excreted in the form of dense bands which are sometimes mistaken by the patients for helminths. Dysentery and ulcerative colitis are characterized by secretion of blood­stained mucus. In haemorrhoidal bleeding, unaltered blood is seen on the surface of stools. Pus is liberated with faeces in ulcerative affections of the large intestine (dysentery, tuberculosis, degrading tumour), or in rupture of a paraproctal abscess. Faeces may contain stones (gallstones, coproliths, pancreatic calculus).

Ascarides, acanthocephala, and members of platyhelminths can be found in stools.

Microscopy of faeces is done to reveal remains of food cells, mucus, eggs of helminths, and protozoa. Most components of faeces can be found in a native preparation which is prepared from faecal emulsion in a small quantity of water. The preparation is then covered with a glass and viewed in the dark field with small and great magnification. Detritus is the main component of faeces. This is material whose particles (minutest particles of food, decomposed cells and microbes) are difficult to differentiate. Among food remains, only muscle fibres and connective tissue can be identified. Muscle fibres (Plate 13) are yellow cylinders with a transverse striated pat­tern which remains unchanged after cooking of meat but which disappears

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Chapter 7. Digestive System

under the action of digestive enzymes. Faeces of a healthy individual on a meat diet contain separate fibres which have lost their striated pattern. Many muscular fibres can be found in faeces (creatorrhoea) if the transport speed of the intestinal contents through the bowels is accelerated. The presence of fibres with preserved striated pattern indicates enzymatic insuf­ficiency of digestive glands.

Connective tissue in faeces indicates inadequate gastric digestion. It ap­pears as semitranslucent fibres with indistinct contours.

Starch and vegetable cellular tissue can be identified among remains of carbohydrate food. Plant cells are easily identifiable by thick coats, and vegetable tissue by thick intercellular partitions (Plate 14). The amount of cellular tissue depends on the character of food and the time of its passage through the large intestine, where it is partly destroyed by microbes. In order to reveal starch, a drop of Lugol's solution is added to the faecal emulsion. Starch grains are stained blue or violet (Plate 15). Starch is a readily assimilable product and normal faeces contain it in very small quantity or do not contain at all. Increased starch content of the faeces (amylorrhoea) is usually associated with diseases of the small intestine: starch remains unsplit due to accelerated peristalsis.

Neutral fat and products of its decomposition are found both in native preparations and preparations stained with Sudan III. From 90 to 98 per cent of neutral fat is assimilated by normal digestion. The remaining fat is excreted mainly as soaps. A great amount of fat is found in faeces (steator-rhoea) in the absence of sufficient lipase. If bile is present in deficient quantity, fatty acids are found in faeces. Sudan III stains neutral fat bright-orange (Plate 16). Crystals of fatty acids occur either as colourless needles with pointed ends (Plate 17) or drops and grains stained with Sudan III. Soaps form fine rhomboids and grains that are not stained with Sudan.

In addition to mucus, the intestinal wall supplies the following elements: leucocytes, erythrocytes, macrophages, cells of intestinal epithelium and of malignant tumours.

Leucocytes occur in normal faeces only as single cells, and their large accumulations (mainly with mucus and erythrocytes) are found in ulcerative affections of the large intestine (dysentery, tuberculosis, ulcerative colitis, cancer). Neutrophils prevail among leucocytes. Eosinophils are found in amoebic dysentery and some helminthiases. Erythrocytes occur in faeces of patients with ulcerative affections of the large intestine, fissures of the anus, and haemorrhoids. If the lesion stands higher in the intestine, erythrocytes decompose before they reach the rec­tum and the presence of blood in faeces should be determined by chemical analysis. Macrophages occur in faeces in the presence of inflammation, especially in bacterial dysentery. Macrophages are larger than leucocytes.

The cytoplasm contains many inclusions, products of phagocytosis. Single cells of intestinal columnar epithelium can occur in normal faeces. Their large accumulations, which are usually found in mucus, suggest colitis. They are often disfigured by digestion and impregnation with soaps. Cells of malignant tumours can be found only in the presence of newgrowths at the distal end of the large intestine.

Oxalates, cholesterol, triple phosphates, and Charcot-Leyden crystals occur in faeces.

An important object of microscopic studies is the detection of protozoa and helminths. If ova are numerous they are found in native preparations. If their quantity is scarce, their concentration should be increased as follows. Faeces are triturated with a heavy liquid (saturated solution of sodium chloride or sodium sulphate): lighter ova float to the surface of the emulsion and are collected together with the surface film by a metal loop and are transferred to an object glass.

Ova of helminths can be isolated by precipitation. To that end an aqueous emulsion of faeces is passed through a gauze to separate it from large particles; the liquid is allowed to stand; then it is decanted and the precipitate is used to prepare the material for microscopy. Telemann's method is more effective. The procedure is essentially the same except that hydrochloric acid and ether are used instead of water: most of the un­digested food is decomposed. Ova are precipitated by centrifuging. Acan-thocephala ova are detected in the material scraped from the perianal folds using a spatula or a cotton wool tampon wetted with glycerin.

Protozoa should be better revealed in freshly defaecated material. The staining techniques are difficult. Cysts of protozoa are well differentiated by staining with Lugol's solution. Amoeba, lamblia, and balantidia are im­portant pathogenic factors.

Only several simple qualitative tests are usually carried out in normal general clinical analysis of faeces. More complicated chemical analysis is used to determine metabolic indices or to study functions of separate parts of the digestive system.

The medium of faeces is determined by litmus paper. If faeces are hard, the paper should be moistened. Normally faeces react weakly alkaline or neutral. This reaction depends on the vital activity of the intestinal flora, which is either fermentative or putrid. If carbohydrate assimilation is in­sufficient the fermentative flora is activated and faeces become acid (fermentative dyspepsia). If proteins are poorly assimilated (gastric or pan­creatic achylia), and also in the presence of inflammation in the large in­testine with exudation of protein, putrid flora becomes more active (putrid dyspepsia): faeces become markedly alkaline due to formation of am­monia.

More detailed information on the relations between fermentative and

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Chapter 7. Digestive System

putrefactive processes in the intestine is obtained by determining organic acids and ammonia in faeces.

If faeces are decoloured, it is important to find out whether secretion of bile into the intestine has stopped or only decreased. This can be determin­ed by carrying out the test for stercobilin. A small specimen of faeces is triturated in a porcelain dish with a 7 per cent solution of mercury dichloride. The result is ready in two days: the mixture becomes crimson in the presence of stercobilin.

The presence of blood in faeces is of great diagnostic importance since it indicates ulcer or newgrowth of the gastro-intestinal tract. The colour of faeces changes only in profuse haemorrhage. Scant blood, or its latent presence can be determined by chemical analysis. In order to identify haemorrhage as a gastro-intestinal one, it is necessary to rule out other possible sources of bleeding, e.g. nose, gums, oesophagus, haemorroids, etc. and also foods containing blood, e.g. meat and fish which should be excluded from the diet three days before the analysis. Tests for iron are im­practicable with determination of blood in faeces because iron can be taken with food or medicine. Methods used for the purpose are based on the pro­perty of haemoglobin to catalyse oxidation-reduction reactions. Pairs of oxidants and reductants are so selected that reactions between them only occur in the presence of haemoglobin (catalyst). Hydrogen peroxide is an oxidant and benzidine a reductant in the Gregersen test. Benzidine changes its colour on oxidation in the presence of blood. There exists a simple modification of this sensitive test. Undiluted faeces are applied in a thin layer to an object glass, which is then placed in a Petri dish on a sheet of white paper. The Gregersen reagent is placed in drops on the smear. (The reagent is prepared extemporarily by mixing equal quantities of a 1 per cent benzidine solution and 50 per cent acetic acid in hydrogen peroxide.) In the presence of blood, a green or blue colour develops, whose brightness and the speed of development depend on the amount of the blood present (the higher the blood content, the brighter the colour and the sooner it appears).

Weber's guaiac test is less sensitive than the benzidine one. It only becomes positive in the presence of profuse haemorrhage. The procedure is as follows: 3 to 5 g of faeces is mixed with strong acetic acid in the quantity sufficient to prepare a semiliquid paste, which is transferred into a test tube. An equal volume of ether is added, the test tube is stoppered and roll­ed on the table to obtain an ether extract. The mixture is allowed to stand for 30 minutes, the ether layer is decanted into another test tube, 1—2 ml of hydrogen peroxide is added, and then an extemporarily prepared alcoholic solution of guaiac resin is added drop by drop (15—20 ml): blue or violet colour appears in the presence of blood.

Food protein is almost completely split by enzymes in the absence of in-

tensified peristalsis. The presence of soluble protein in faeces therefore in­dicates its intense liberation by the intestinal wall during inflammation and ulceration (which are attended by cell decomposition), and haemorrhage. The Triboulet-Vishnyakov test is used to detect soluble protein. Equal por­tions of a 3 per cent aqueous emulsion of faeces are placed in three test tubes: 2 ml of a 20 per cent trichloroacetic acid solution (or 7 per cent hydrochloric acid) is added to one test tube, 2 ml of a 20 per cent acetic acid to the other, and 2 ml of water to the third test tube (control). The result is assessed in 24 hours: soluble protein coagulates in the presence of mercury perchloride or trichloroacetic acid and precipitates to trap microbes and detritus; the liquid is thus clarified. In the presence of excess mucus, the emulsion clarifies in the test tube containing acetic acid.

The study of activity of intestinal enzymes and absorption in the small intestine is also of diagnostic importance.