3. small Anim. Pract. (1973) 14, 61-82

The radiological diagnosis of gastrointestinal obstruction in the dog

C H R I S T I N E GIBBS A N D H. P E A R S O N

University of Bristol, Department of Veterinary Surgery, Langford House, Langford, Bristol, BS18 7DU

A B S T R A C T

The use of contrast medium in the examination of the gastrointestinal tract is described and some aspects of the normal radiographic anatomy are discussed. The radiological features of certain conditions causing gastro- intestinal obstruction are illustrated by a series of radiographs.

I N T R O D U C T I O N

Gastrointestinal obstruction is one of the commonest indications for laparotomy in the dog, and accurate clinical appraisal of such cases is essential if the most expedient treatment is to be carried out. Radiological examination is an important aid to the diagnosis and assessment of the various conditions involved.

Radiographic techniques and the normal radiological anatomy of the abdominal cavity have been described in some detail by several authors (Dyce, Merlen & Wadsworth, 1954; Rhodes, 1961 ; Morgan, 1964; Johnson, 1965; Carlson, 1967; Douglas & Williamson, 1970).

Although gross abnormalities and opaque lesions are visible on plain radio- graphs, examination with contrast medium is often required. Because many depressant drugs impair motility of the gastrointestinal tract and delay the passage of ingesta, animals undergoing such investigation must be conscious and unsedated. At present, barium sulphate is the most satisfactory contrast medium available.

A wide range of dose rates has been suggested, but 2 cc per kg. body weight has been found suitable. Root & Morgan (1969) compared the properties of a commercial micropulverized suspension (e.g. Micropaque-Damancy) with hand mixed barium sulphate USP and found that the former had significant advantages. I t has been commonly believed that the administration of barium sulphate is

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contra-indicated in cases of acute obstruction because of a tendency to produce impaction proximal to the lesion, but the same authors report studies which demonstrate that this is not an appreciable hazard, and no such complications have been encountered in this clinic.

Animals which are severely ill and presented as emergencies are radiographed without preparation, but premeditated investigations should be preceded by 12 hours’ starvation, and evacuation of the large bowel. A micro-enema containing sodium citrate (Micralax-Smith Kline & French) is useful for this purpose.

Fluoroscopy with image intensification has certain advantages over conventional radiography, particularly in functional studies of the alimentary tract. However, the availability of equipment for this technique is limited and its use is therefore not discussed in this paper.

Clinical and radiological signs are related to the degree, site and duration of obstruction. Complete obstruction causes accumulation of ingesta, secretions and gas in the tract proximal to the lesion, producing acute and characteristic signs. Partial, intermittent, or slowly developing occlusions may only cause delay in the passage of gastrointestinal contents, and therefore produce a variable range of indefinite symptoms.

Anatomical differences make it convenient to consider the radiological changes affecting the stomach, small bowel and large bowel separately, although it may not be possible accurately to locate the site of obstruction from clinical examina- tion alone. It is important to locate the obstruction because, for example, gastro- tomy requires a different laparotomy approach to enterotomy, and a foreign body in the large intestine has already passed the narrowest part of the tract and does not require surgical removal. For this reason, a short account of the normal position and radiological appearance of each part of the tract precedes each section.

The stomach The stomach is relatively inaccessible to palpation unless it is enlarged or

displaced. Radiography is therefore indicated for the investigation of the majority of gastric lesions. I n the normal animal the fundus and body lie on the left side of the abdomen, just behind the diaphragm under the last few ribs. The pyloric antrum crosses the midline and the pyloric canal is situated on the right, well cranial to the greater curvature. The empty stomach is related cranially and laterally to the liver from which it cannot be distinguished, but it almost always contains some gas which outlines the mucosal folds. If the animal has recently eaten, thc stomach is greatly increased in size and contains mottled shadows of variable density.

The distribution of gastric contents depends on the position of the animal during radiography because heavy materials gravitate. In contrast medium examinations, dorsoventral and right lateral projections are best for outlining the pylorus, and ventrodorsal and left lateral positions produce filling of the body and

G A S T R O I N T E S T I N A L O B S T R U C T I O N 63

fundus. Erect views using a horizontal X-ray beam, show gas, fluid and contrast medium levels as horizontal interfaces. Radiological features of gastric obstruction are alterations in the size, shape and position of the stomach, abnormal gastric contents, delayed emptying time, filling defects and persistent irregularities in mucosal outline.

(a) Foreign Bodies. Many gastric foreign bodies are asymptomatic or cause only occasional vomiting, and their presence is often revealed during radiographic examination of other structures. Radiopaque objects are easily recognized on

FIG. 1 . Border Collie, 8 years. Ventrodorsal radiograph of the pyloric region showing contrast medium outlining a radiolucent rubber ball in the pyloric antrum.

plain radiographs, provided the position of the stomach can be identified. Con- trast radiography is of particular value in detecting the presence of radiolucent articles which may either retain contrast medium or prevent its even dispersion throughout the organ. Fig. 1 demonstrates pyloric obstruction by a rubber ball which was responsible for intermittent vomiting over a period of 8, months.

The ingestion of large quantities of fabric, string or hair may ldad to filling of the gastric lumen and pylorus, and somewhat variable symptoms of vomiting or anorexia. Such materials cause filling defects on contrast radiography and then become readily visible as in Fig. 2. This stomach filled with string could not be identified on plain films.

(b) Pyloric Lesions. Pearson ( 1970) described the radiological features of pyloric stenosis, congenital or acquired. Rhodes and Brodey (1965) recognize three

64 C H R I S T I N E GIBBS AND H. PEARSON

separate entities producing pyloric obstruction, namely congenital hypertrophic stenosis, acquired hypertrophy and pylorospasm. They describe and illustrate each condition.

Obstruction of the pyloric outlet for whatever reason causes distension of the stomach with fluid or food dCbris long after ingesta would normally have entered the small intestine. Horizontal beam radiography in such cases. will reveal inter- faces between solid, fluid and gaseous contents.

FIG. 2. Labrador, 5 years. Lateral radiograph one hour after the administration of barium showing multiple small filling defects in the stomach caused by string which extends into the colon, producing plication of the small intestine which is ‘bunched-up’ and contains

linear filling defects.

Contrast radiography is helpful in determining gastric emptying time which is markedly delayed in pyloric obstructions. In the normal conscious animal, contrast medium usually begins to enter the duodenum within a few minutes and total retention within the stomach for 30 minutes, or longer, generally indicates some degree of pyloric occlusion (Fig. 3) . Provided gastric emptying time is normal, the presence of a contrast filled pyloric antrum is of no significance as this is frequently observed in normal animals; its appearance on consecutive films however, over a period of an hour or more, is compatible with obstruction of the pylorus. Of more significance are the rate and volume of contrast material passing into the duodenum.

Radiography can only indicate prolonged emptying time and exploratory

G A S T R O I N T E S T I N A L O B S T R U C T I O N 65

surgery is necessary to differentiate pylorospasm, neoplastic occlusion, and congenital or acquired hypertrophy.

(c) Congenital Diaphragmatic Defects. Pearson (1970) illustrated a case of hiatus hernia as a rare congenital anomaly in which part of the stomach herniates through a defect in the oesophageal hiatus. Baker & Williams (1966) recorded a case of diaphragmatic pericardial hernia in which part of the stomach was found in the pericardial sac. The diagnosis of these conditions is confirmed by radiological examination using contrast medium which outlines the displaced stomach within the thoracic cavity.

FIG. 3. Dachshund, 7 years. Pyloric hypertrophy. Lateral radiograph of the pyloric region one hour after barium. The pyloric antrum is dilated and only a small quantity of

contrast medium has reached the small intestine.

(d) Dilation and Torsion. This syndrome is well recognized in some of the larger breeds and has been reported in some detail (Funkquist & Garmer, 1967; Funk- quist, 1969). Radiographs should not be required for diagnosis of acute cases but after conservative treatment, a barium meal may be indicated to assess gastric emptying time to determine the need for pyloromyotomy. In cases of sub-acute dilation extending over several days or weeks, the diagnosis on symptoms alone may not be immediately obvious. Radiographs of such cases in two planes will reveal marked gastric dilation and a gas/fluid interface (Fig. 4) simulating primary pyloric occlusion, but the degree of gastric distension with fluid par- ticularly, is greater in cases of idiopathic dilation.

A more unusual form of dilation and torsion may occur as a complication of rupture of the left diaphragm. Such cases are presented with extreme dyspnoea,

66 C H R I S T I N E G I B B S A N D H . P E A R S O N

cyanosis and circulatory failure of sudden onset a variable time after trauma. The tympanitic stomach occupies the left side of the thoracic cavity and its presence is demonstrated by radiographs of the thorax (Fig. 5).

(e) Gastric Neoplasia. Tumours of the stomach are reported to be rare and difficult to diagnose. They cause persistent vomiting, increasing in severity, often with haematemesis and melaena. The animal rapidly loses weight and is

FIG. 4. Dachshund, 5 years. Chronic gastric dilation. The erect lateral view (above) shows a horizontal gasifluid interface in the grossly dilated stomach which fills the abdominal cavity. The ventrodorsal film (below) shows that the distension involves mainly the body of the stomach which is in its normal position on the left side of the ab-

domen.

usually depressed. In a. review of fourteen cases, Berg, Rhodes & O’Brien (1964) identified abnormalities in only half the cases examined radiographically. Douglas, Hall and Walker (1970) recommend the use of fluoroscopy for the diagnosis of gastric neoplasia. The radiological signs are variable and depend on the site and extent of the lesion. If the pylorus is involved the only sign may be dilation of the stomach and delay in the passage of contrast medium through the pyloric canal.

G A S T R O I N T E S T I N A L O B S T R U C T I O N 67

In other cases, filling defects in the pyloric antrum are visible on consecutive films (Fig. 6). With invasion of the mucosa there may be noticeable disruption of the normal pattern of rugal folds on serial radiographs and, if the neoplasm is sufficiently large, the outline of the gastric lumen is consistently irregular.

FIG. 5. Whippet, 3 years. Gastric dilation within the thoracic cavity. The lateral recumbent radiograph (above) shows the outline of a gas-filled structure in the posterior thorax. The heart shadow is displaced cranially and the lungs are collapsed and displaced craniodorsally. The outline of the distended pyloric antrum containing fluid can be seen through the gas shadow. The dorsoventral view (below) shows dis- tended stomach on the left. Normal vascular lung markings are absent in this area. The heart shadow is displaced to the right and the left intercostal spaces are increased. This

case had a history of a road accident 9 months previously.

A tentative radiological diagnosis should always be confirmed by exploratory laparotomy and possibly gastrotomy to eliminate the possibility of acquired pyloric hypertrophy which may develop even in old dogs, of breeds not usually associated with the condition.

(f) Exlrinsic .Neo+.ria. Large tumour masses in the anterior abdomen may com-

68 C H R I S T I N E GIBBS A N D H. P E A R S O N

press or displace the stomach and thus cause symptoms of obstruction. Such lesions may be demonstrated by the administration of contrast medium (Fig. 7).

Conversely, the pyloric shadow on plain radiographs may simulate an anterior abdominal mass, and barium administration in such cases may help to identify solid tissue shadows.

Small intestine The duodenum has a short mesenteric attachment and its position is therefore

relatively constant. At its proximal end it forms a loop just cranial to the pylorus and then passes caudally on the right side of the abdomen. I t doubles back in the mid-lumbar region and becomes indistinguishable from the remainder of the small

FIG. 6. Labrador, 8 years. Adenocarcinoma of the pylorus. One hour after barium the lateral radiograph shows filling defects in the pyloric antrum and a sharp ‘cut off’ appearance at the gastro-duodenal junction. There is no retention of contrast medium.

bowel. O n plain radiographs the duodenum is visible only if it contains gas, but it is clearly outlined by contrast medium. Saucer-shaped filling defects resembling ulcer craters are often seen. O’Brien, Morgan & Lebel(l969) found this appearance in over 50% of a series of normal Beagles and attributed it to aggregates of submucosal lymphoid tissue unlikely to be of clinical significance.

The jejunum and ileum occupy the ventrocaudal part of the abdomen. They are freely moveable and therefore easily displaced. O n a normal radiograph segments of small intestine are seen in many planes and contain variable amounts of fluid and gas. As the position of bowel loops and the diameter of the lumen

G A S T R O I N T E S T I N A L O B S T R U C T I O N 69

change constantly with peristaltic movements, i t is not possible even with contrast medium, accurately to identify any particular segment.

The diagnostic radiological signs of obstruction of the small intestine are: (a) dilation of the proximal intestine, often with excessive gas accumulation. (b) multiple horizontal interfaces indicating gas-capped fluid levels on lateral erect films. (c) partial or total obstruction to the flow of ingesta (and contrast medium) down the intestine. (d) with some lesions, persistent displacement of intestinal loops.

FIG. 7. Corgi, 8 years. Lateral radiograph with barium showing compression and caudal displacement of the stomach by a liver tumour.

(a) Foreign Bodies. These constitute the commonest cause of bowel obstruction in the'dog. Clark (1968) reviewed a series of one hundred cases in only thirty-nine of which was the foreign body palpable in the conscious animal. Seventy-six cases were radiographed and in almost one-third, the foreign body was not visible; distension of the bowel was seen in only nineteen cases. In contrast, 75% of the cases radiographed by the authors showed evidence of bowel dilation on plain films.

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FIG. 8. Basset Hound, 1 year. The lateral radiograph 24 hours after barium shows a pebble in the small intestine midway between the dorsal and ventral abdominal walls at the level of the 3rd and 4th lumbar vertebrae. The foreign body had been masked by con- trast medium on earlier films. Some barium has passed the obstruction and is incorporated in faecal boluses in large bowel. Loops of proximal jejunum and ileum are dilated and

contain gas and diluted contrast medium.

FIG. 9. Boxer, 4 years. Erect lateral radiograph. Dilated loops of bowel containing contrast medium and gas show characteristic gas-capped fluid levels. The obstruction, a rubber

grommet, was radiolucent.

G A S T R O l N T E S T I N A L O B S T R U C T I O N 71

The value of preliminary plain films in detecting either the foreign body or bowel dilation cannot be over-emphasized. Figure 8 demonstrates masking of a highly radiopaque object by the premature administration of barium contrast.

Of equal value as an indication of bowel obstruction is the presence of gas/fluid interfaces on lateral erect films. Such levels are visible on plain radiographs but are intensified by contrast medium administration (Fig. 9).

Obstruction of the proximal bowel, especially the duodenum, may produce severe clinical illness with dilation of only a relatively short segment of intestine which may not be clearly visible on plain radiographs (Fig. 10). Contrast radio- graphy in such cases of obstruction by a radiolucent object will outline the dilated bowel and demonstrate the position of the foreign body (Fig. 11).

FIG. 10. Labrador, 14 months. Obstruction with fabric. Recumbent lateral plain radio- graph. A short ‘C’ shaped segment of proximal bowel in the craniodorsal abdomen is dilated and contains gas. The lumen diameter of the remaining small intestine is increased.

As in the stomach, obstruction of the intestine with fabric is not always easy to diagnose. The degree of proximal dilation may be considerably reduced because fluid is absorbed by the foreign body. There is nevertheless some gaseous dilation of the’obstructed gut (Fig. 10). With foreign bodies of this type, peristalsis tends to ‘bunch’ the intestinal loops and this characteristic feature can be demonstrated by the administration of barium which also either reveals filling defects: or adheres to the fabric and thus produces typical linear shadows on the mesenteric border of the affected segment of bowel (Fig. 2) .

The presence of ingested bone in the stomach is of no significance and the

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authors have not encountered obstruction of the small intestine due to bone. Macerated bone particles leaving the stomach may produce diffuse opacities in the small intestine which are not significant. The impaction of such fragments, however, into an apparent columnar obstruction of small bowel is more serious (Fig. 12). Two such cases have been observed and both died, not because of bowel obstruction but from an acute haemorrhagic enteritis caused, presumably, by the traumatic effect of the bone spicules on the bowel mucosa.

FIG. 1 1 . Crossbred, 1 year. Ventrodorsal radiograph with barium showing dilation of the duodenum and the outline of a rubber teat occluding the proximal jejunum. The

stomach is almost empty, but no contrast medium has passed the obstruction.

In cases of suspected obstruction in which barium passes normally down the intestine, ‘follow-up’ films at 24 hours or when all contrast medium is in the large bowel, may be diagnostic in revealing an incomplete obstruction caused by a radiolucent foreign body which has absorbed and retained contrast material (Fig. 13).

(b) Intussusception. As this condition does not cause complete obstruction of‘ the

FIG. 12. Chihuahua, 5 years. Lateral plain radiograph showing a column of impacted bone fragments in the jejunum.

FIG. 13. Crossbred, 8 years. 24 hour ventrodorsal radiograph showing contrast medium retained by a small radiolucent object in small intestine on the right side of the ab- domen at the level of L6. The remaining barium has reached the descending colon. At laparotomy this foreign body was retained in a segment of small intestine involved in

adhesions probably resulting from ovarohysterectomy.

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bowel, the degree of dilation and gas accumulation may not be excessive. On plain radiographs the lesion may be apparent because of its increased density and this is particularly noticeable if the intussusception passes into the colon in which gas acts as a negative contrast agent (Fig. 14). Intussusceptions extending down the colon may also be demonstrated by the use of barium contrast enemata. Lesions not apparent on plain films are demonstrable by serial radiography after barium administration. The characteristic features are a sharply demarcated

FIG. 14. Basset Hound, 6 months. Plain ventrodorsal radiograph showing an intussuscep- tion, outlined by gas, in the transverse colon.

segmental narrowing of the bowel calibre and thread-like shadows of contrast medium along the lumen of the intussuscepted gut (Fig. 15). Long-standing cases show massive proximal bowel distension which occurs in all chronic obstructions (Fig. 16).

(c) Strangulation. Such obstructions result from herniation of intestine through a congenital or acquired defect in the mesentery, omentum or abdominal wall. Small bowel may become incarcerated in cases of congenital diaphragmatic- pericardial hernia (Baker & Williams, 1966).

G A S T R O I N T E S T I N A L O B S T R U C T I O N

FIG. 15. West Highland White Terrier, 4 months. One hour lateral radiograph showing abrupt thread-like narrowing of the intestinal lumen caused by an intussusception.

FIG. 16. Labrador, 1 year. 2 hours after barium the ventrodorsal radiograph shows massive dilation of small intestine proximal to a long-standing intussusception.

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76 C H R I S T I N E G I B B S A N D H . P E A R S O N

Radiological signs of bowel strangulation are dilation of the proximal gut and either fixation, or displacement, of bowel on consecutive films. With abdominal wall lesions, as for example inguinal herniae, the proximal bowel may be dilated and is consistently apposed to the hernial ring (Fig. 17) . Diffuse dilation and ‘bunching’ of small intestine strangulated through the omentum is illustrated in Fig. 18. Extreme displacement of bowel through a mesenteric tear (Fig. 19) may be clearly demonstrable only by barium administration, which is also invaluable in diagnosing inter-muscular migration of intestine following rupture of the abdominal wall.

FIG. 17. Yorkshire Terrier, 7 years. Strangulated inguinal enterocoele. Plain ventro- dorsal radiograph showing dilated segments of small bowel extending to the inguinal

region on the left side.

(d) Stenosis. Stenosis may result from previous intra-abdominal surgery, either of the intestine, or other abdominal viscera. Adhesions following ovario-hysterec- tomy, hysterotomy, cystotomy or local and generalized peritonitis may involve intestine and so constrict the lumen. In occasional cases sloughing of an intussus- ception may have the same effect. Stenosis is usually gradual in onset and leads to

G A S T R O I N T E S T I N A L O B S T R U C T I O N

FIG. 18. Samoyed, 8 months. Intestinal strangulation through an omental defect. Plain lateral recumbent radiograph. The entire small intestine is ‘bunched up’ and contains gas.

FIG. 19. Pekingese, 3 years. Strangulation through torn mesentery. Lateral recumbent radiograph with barium in the stomach which is pushed caudally by grossly displaced small intestine. The transverse colon (containing gas) also shows caudal displacement. Contrast medium in the oesophagus indicates some degree of obstruction at the cardia.

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78 C H R I S T I N E GIBBS A N D H . P E A R S O N

chronic distension of the proximal intestine (Fig. 20), often with multiple gas- capped fluid levels on lateral erect films. The degree of distension and the site of obstruction may be more clearly demonstrated by barium contrast radiography. I n stenosis caused by adhesions following bowel perforation by a sharp foreign body, the dilation may be less severe if the intestines are all tightly bunched in an adherent mass.

FIG. 20. Dachshund, 3 years. Recumbent (above) and erect (below) lateral plain radio- graphs show small bowel dilation and gas-capped fluid levels indicating obstruction. A barium meal showed delayed passage of contrast medium. At laparotomy most of the small intestine was involved in extensive adhesions. There was a history of a previous

enterotomy.

(e) JVeoplusia. Tumours are an infrequent cause of bowel obstruction. I n a study of ninety-five gastrointestinal neoplasms, Brodey & Cohen (1964) found that thirty-four involved small intestine and of these, sixteen were lymphosarcomata which produced generalized lesions and no obstruction. Stenosis was noted in three cases of adenocarcinoma, and Taylor & Kater (1954) described the post-

G A S T R O I N T E S T I N A L OBSTRUCTION 79

mortem findings in a similar case in which the bowel proximal to the obstruction was dilated to 10 cm.

In those cases in which the bowel lumen is narrowed by neoplasia, particularly adenocarcinomata, intestinal foreign bodies are not uncommonly retained proximal to the lesion and thus simulate primary foreign body obstruction (Fig. 21). In other cases of neoplastic stenosis, progressive proximal bowel dilation may be expected. If the lesion is ulcerated, even without stenosis, contrast medium may be retained and thus outline the ulcerated lesion.

FIG. 2 1. Terrier, 10 years. Ventrodorsal plain radiograph showing accumulation of small stones proximal to an adenocarcinoma partly occluding the jejunum.

As the majority of bowel tumours are lymphosarcomata which do not unduly constrict the lumen, radiography is not a reliable means of diagnosing intestinal neoplasia.

(f) Post-operative ileus. I n the authors’ experience, this complication is extremely rare but Douglas, Hall & Walker (1970) emphasized its importance following gastric resection. Carlson (1967) suggested that in such cases, gas-capped fluid levels seen on erect or horizontal beam radiographs lie in the same horizontal plane, whereas numerous different levels are seen in bowel obstruction.

80 CHRISTINE G I B B S AND H. PEARSON

Large intestine The position of the caecum and ileocolic valve on normal radiographs is

variable, but they tend to lie on the right side of the abdomen in the mid-lumbar region about midway between the dorsal and ventral abdominal walls. The caecum can often be located as a rounded gas-filled structure. The colon, which has a relatively short mesentery, is smooth-walled and has a diameter larger than that of small intestine. I t passes forward on the right side of the abdomen to a position under the costal arch where it may overlie the stomach, then crosses the

FIG. 22. Crossbred, 8 years. Ventrodorsal radiograph showing contrast medium from a barium meal outlining a tumour filling the lumen of the colon at the level of the first lum-

bar vertebra. A barium enema had failed to demonstrate this lesion.

midline as transverse colon and returns on the left to the pelvis where it becomes continuous with the rectum. Occasionally, ventrodorsal radiographs of fat dogs show the descending colon displaced to the right. Unless it is completely empty, large intestine can be distinguished from small, either by the presence of faecal material or by gas outlining the wider lumen.

G A S T R O I N T E S T I N A L O B S T R U C T I O N 81

Lesions of the large intestine can be demonstrated by a barium enema under general anaesthesia. Approximately 50-300 ml, according to bodyweight, of a commercial suspension of barium sulphate (Micropaque-Damancy) diluted 50 %, is used. The contrast medium is introduced through a self-retaining catheter with an inflatable bulb placed just inside the rectum. Infusion is by gravity using an open container or a flutter valve. If symptoms suggest the presence of a large bowel lesion which cannot be confirmed by a barium enema, radiographs following oral barium contrast may be more rewarding (Fig. 22).

(a) Foreign Bodies. Objects which have passed down the small intestine are often in the colon at the time of radiography and are usually soon voided. Identification of the colon in such cases will avoid an unnecessary laparotomy. Sharp metallic foreign bodies engaging the rectal or anal mucosa are obvious on plain radiographs which should always precede contrast radiography.

FIG. 23. Scottish Terrier, 13 years. Barium enema. Lateral radiograph showing filling defects in the rectum at the pelvic inlet. This is the characteristic appearance of an

annular constricting neoplasm.

(b) Faecal Impaction. This condition is easily recognizable clinically and radio- logically. Radiography may be of value in revealing the presence of underlying causes as, for example, bone spicules, prostatic enlargement, old pelvic fractures or sharp foreign bodies in the lower bowel.

(c) Neoplasia. Tumours of the large intestine are not common but their presence should be suspected in older animals which show fresh blood in the faeces, and tenesmus. Following oral or anal contrast administration, radiological signs of

a2 C H R I S T I N E GIBBS A N D H. P E A R S O N

large bowel neoplasia are consistent filling defects (Figs. 22 and 23)) narrowing of the bowel lumen or retention of contrast medium on ulcerated lesions.

A C K N O W L E D G M E N T S

We are indebted to those veterinary surgeons who referred the cases for investiga- tion and to Mr H. R. Denny for permission to include Fig. 20. The radiographs were taken by Mrs J. Hancock, Mrs R. Price, Miss R. J. Harrison and Miss K. E. Hill and photographed by Mr M. H. C. Parsons and Mr J. Conibear. Finally, we are grateful to Professor A. Messervy for providing the facilities for this work to be carried out.

R E F E R E N C E S

BAKER, G. J. & WILLIAMS, C.S.F. (1966) Vet. Rec. 78, 578. BERG, P., RHODES, W.H. & O’BRIEN, J.B. (1964) 3. Am. vet. Radiol. SOL. 5, 47. BRODEY, R.S. & COHEN, D. (1964) Sci. Proc. lOIst a . Meet. Amer. vet. med. Ass. p. 167. CARLSON, W.D. (1967) Veterinary Radiology. 2nd edn. Balliere, Tindall & Cassell, London. CLARK, W.T. (1968) Vet. Rec. 83, I I. 5. DOUGLAS, S.W., HALL, L.W. & WALKER, R.G. (1970) Vet. Rec. 86, 743. DOUGLAS, S.W. & WILLIAMSON, H.D. (1970) Veterinary Radiological Interpretation. 1st edn. Heine-

DYCE, K.M., MERLEN, R.H.A. & WADSWORTH, F.J. (1954) Br. vet. 3. 110, 83. FUNKQUIST, B. (1969) J . small Anim. Pract. 10, 507. FUNKQUIST, B. & GARMER, L. (1967) 3. small Anim. Pract. 8, 523. JOHNSON, F.L. (1965) Mod. vet. Pract. 46, 81. MORGAN, J.P. (1964) Sci. Proc. IOIst a . Meet. Amer. vet. med. Ass. p. 155. O’BRIEN, J.R., MORGAN, J.P. & LEBEL, J.L. (1969) 3. Am. vet. med. Ass. 155, 713. PEARSON, H. (1970) 3. small Anim. Pract. 11, 403. RHODES, W.H. (1961) Small Anim. Clin. 1, 103. RHODES, W.H. & BRODEY, R.S. (1965) 3. Am. vet. Radiol. SOL. 6 , 65. ROOT, C.R. & MORGAN, J.P. (1969) 3. small Anim. Pract. 10,279. TAYLOR, F. & KATER, J.C. (1954) Aust. vet. 3. 30, 377.

mann, London.

R6sumC. On dkcrit l’usage de substance de contraste dans l’exploration des voies gastro-intes tin- ales, et on discute de certaines aspects de l’anatomie radiographique normale. Les caractkristiques radiologiques de certaines particularit& causant une obstruction gastro-intestinale sont illustrkes au moyen d’une sCrie de radiographies.

Zusammenfassung. Der Gebrauch von Kontrastmitteln in der Untersuchung des Verdauung- skanal ist beschrieben und einige Aspekte von der normalen rontgenologischen Anatomie sind diskutiert. Die radiologischen Merkmale von gewissen Zustanden die gastrointestinale Obstruktion verursachen, sind in einer Serie vom Rontgenaufnahmen illustriert.