The acute abdomen

Pathology

 

Calcification

Calcified stones are radio-opaque, bright grey (on the radiograph), welldefined and round. Multiple, facetted and multilayered stones may be found in the gallbladder and the urinary bladder in patients with longterm catheters. Single or multiple stones may be seen in the renal pelvis and ureters and occasionally in the biliary tree and pancreatic duct.

Benign lesions such as myomata ofthe uterus, adenornata of the adrenals, organized haematomas, leiomyomas, renal cyst walls and dermoid may all calcify.

Malignant calcification is a rare entity, usually located in the periphery of a hepatoma or centrally in the necrotic parts of a malignancy.
The areas of calcification associated with inflammatory lesions are usually multiple and small and found in the pancreatic gland as a sign of chronic pancreatitis (Fig. 3). Shell-like calcification may be seen in patients with echinococcosis of the liver.
Vascular calcification occurs in phleboliths, atherosclerotic plaques and in aneurysms where it commonly has a shell-like appearance (e.g. splenic artery aneurysms).

a

Figure 7. a) Large volume of ascites obliterating the fat planes around the kidneys and iliopsoas muscles and pushing air-containing bowel loops towards the middle of the abdomen, allowing only barium-filled loops to sink laterally. b) Abdominal ultrasound of the same patient revealing free fluid ventral to the liver seen as a dark, hypoechoic zone between the liver and the ventral abdominal wall. The white hyperechoic curvilinear line in the lower part of the image is the diaphragm.

b

Ascites

When the fat planes around the urinary bladder and the rectum are obliterated this is often due to the presence of an increased amount of fluid in the abdominal cavity, seen as a crescentic density in the pelvis (Fig. 7). Larger volumes of ascites separate the bowel loops and obliterate the fat lines in the paracolic gutters, and volumes in excess of l litre displace the air-containing bowel loops centrally in the abdomen while obliterating

Figure 8. Abdominal CT in a patient with a perforated peptic ulcer. Free gas is seen in the midline (1) close to the contrast-filled stomach (2). A minimal amount of ascites is seen around the liver and spleen (4). Fat is shown as dark grey areas surrounding the kidneys, large abdominal vessels and the pancreas behind the stomach. The gallbladder (3) is also seen.

the fat contours of the kidneys and psoas muscles (Fig. 7 a).

Nowadays, ascites is ruled out by abdominal ultrasound (Fig. 7 b) or CT (Fig. 8) as these modalities can detect very small quantities of free fluid.

Pneumoperitoneum

Perforation of a bowel loop allows gas to pass into the abdominal cavity. It collects in non-dependent sites, and is best detected on a horizontal beam film centred at sites such as the subphrenic space in an erect patient or the uppermost part of the abdominal cavity in a recumbent one. In order to improve the image quality coned views are recommended (Fig. 6). If only a tiny volume of gas has leaked through a perforation this may only be disclosed on CT (Fig. 8).

Large volumes of gas may be found after open abdominal surgery or following perforation of the large bowel. In these circumstances the free gas may be demonstrated even on vertical beam images as it delineates the gallbladder and the outer, serosal border of the bowel wall, which will be seen as thin, curved lines (Fig. 9). Postoperatively gas disappears within two weeks if no complication occurs.

Intra-peritoneal gas may also be seen in patients on peritoneal dialysis and following hysterosalpingography and percutaneous endoscopic or interventional procedures.

 

Figure 9. Large amount of free abdominal air in a young patient with caecal perforation due to a sigmoid carcinoma. Widened loops of small bowel are recognized by their spiral folds. The bowel wall is outlined as a white line by the gas on either side.

Localized gas collections

Although an abscess is a space occupying lesion it is not usually diagnosed on plain films until it contains gas, either as a collection of small bubbles or, when these have merged into a large bubble, as an extended air-fluid level. The latter is commonly seen in the subphrenic space or the lesser sac (Fig. 10). CT and ultrasound are helpful in distinguishing a gas-containing abscess from entities having a similar appearance such as the large bowel contents and retroperitoneal or subcutaneous emphysema. Abscess drainage procedures are readily conducted under US or CT guidance.

Necrosis of the bowel may be revealed by numerous small collections in the gut wall. This gas may enter the draining mesenteric veins and collect intrahepatically in the portal system, a radiographic feature of sinister portent (see below Fig. 32). The presence of intramural gas does not invariably indicate serious pathology, however, the idiopathic occurrence of pneumatasis coli seen in the elderly is a reversible condition (Fig. 11).

Figure 10. Abscess following a Billroth-1 resection located in the lesser sae and beneath the diaphragm (arrows). Secondary pleuritis with obliteration of the aortodiaphragmatic (1) and lateral (2) pleural recesses. (When Gastrografin is given, the anastomotic leak is demonstrated. The air-fluid levels in the abscesses are clearly seen.)

	Figure 11. Pneumatosis cystoides coli in an elderly patient with multiple air-filled cysts seen as black filling defects in the barium-filled lumen
	Figure 12. Necrotic appendicitis in a 16-year-old boy. A large soft-tissue mass is seen in the right lower quadrant representing fluid-containing bowel loops. The proximal small bowel is slightly dilated with short air-fluid levels (arrows) and the large bowel is dilated with long levels indicating a dynamic (paralytic) ileus.
	Figure 13. Ultrasonography of the left lower abdominal quadrant in a 65-year-old patient with fever and clinical signs of sigmoiditis, disclosing marked thickening of the bowel wall (calipers). Diverticula can just be discerned to the left of the image.

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Inflammatory conditions

Localized inflammation causes limited peritonitis with secondary paralysis of neighbouring bowel loops in which fluid and gas collect. Adjacent fat planes are obliterated owing to oedema. Lateralised peritonitis in young adults causes sometimes a decompressing contraction of the ipsilateral psoas muscle and a secondary scoliosis. In patients with localized signs and symptoms, whether due to possible cholecystitis, pancreatitis, appendicitis (Fig. 12), salpingitis or sigmoiditis, CT and ultrasound (Fig. 13)

Figure 14. Acute cholecystitis with wall oedema (arrow) and multiple large stones in the gallbladder (1) creating a broad acoustic shadow (2). The common bile duct is widened (d) indicating a peripheral obstruction.

should be considered as the imaging methods of first choice.

Cholecystitis

Nowadays patients with suspected cholecystitis undergo ultrasonography of the gallbladder and the bile ducts as the primary imaging investigation. In acute cases the bladder is dilated and globular and a rim of fluid is occasionally seen (Fig. 14). The gallbladder is usually tender to pressure of the probe, a modem manifestation of Murphy's sign. Stones reflect and absorb all the ultrasound energy so creating an acoustic shadow beyond the stones. In chronic cases a thick gallbladder wall is also seen.

Gangrenaus cholecystitis is caused by gas-producing bacteria; it is seen as free gas in the gallbladder or as a rim of emphysema in the wall (Fig. 15).

Pancreatitis

Pancreatitis causes the gland to become swollen (Fig. 16) and its surrounding fat planes are obliterated. In severe cases the oedema will spread into the transverse mesocolon toward the stomach and left kidney. Secondary peritonitis paralyses the duodenum and the overlying transverse colon. The disease may be complicated by the formation of cysts and abscesses in the lesser sac and sub-phrenic spaces, left sided pleuritis, lung atelectasis and pneumonia. Although ultrasound may be used, CT is a better choice of imaging modality as these patients are frequently

	Figure 15. Abdominal survey revealing gas in the gallbladder (star) with wall emphysema (arrows).
	Figure 16. Acute pancreatitis with a swollen pancreatic gland (1) and partially obliterated retroperitoneal fat planes. The fascia around the left kidney is markedly engorged (arrows) and fluid can be seen in the lesser sac (2).

in severe pain resulting in the accumulation of bowel gas which interferes with the ultrasound study.

Chronic pancreatitis may give rise to multiple areas of calcification (Fig. 3), which are easily detected on CT and ultrasound.

 

Figure 17. Ultrasound image in a patient with an inflamed appendix (arrows) and a small abscess (a).

Peritonitis

Generalized peritonitis is accompanied by a purulent exudate which causes the obliteration of fat planes and a secondary ileus with long air-fluid levels (Fig. 12).

Appendicitis

Ultrasonography is often helpful in confirming the diagnosis of appendicitis in patients in whom the history or clinical presentation is atypical. A normal appendix cannot be seen, whereas a swollen organ may be identified together with its surrounding oedema (Fig. 17).

Enteritis

Patients with gastro-enteritis and sigmoiditis are not usually examined radiologically. If studies are undertaken in the former condition, however, they reveal a number of small to medium-sized air fluid levels in both the small and large bowel; patients with sigmoiditis normally undergo investigation only if the disease is complicated by perforation or obstruction.

Colitis

Both pseudo-membranous colitis and toxic ulcerative colitis may cause an acute abdomen. The former is drug-induced and caused by toxins and Clostridium difficile; the latter may give rise to peritonitis. The colon in both entities is paralysed and the wall is thickened by oedema, seen as polypoid "thumbprint" indentations into the air column of the lumen (Fig. 18).

Figure 18. Abdominal survey in a patient with toxic colitis. The transverse colon (1) is string-like and "fingerprinted" with numerous polypoid identations. Gas is seen in widened ileal loop (2) and stomach (3).

Patients with toxic colitis, toxic dilatation or megacolon have to be monitored by repeated examinations until gut motility returns, the frequency of the studies being determined by the patient's clinical state. If the colon dilates or emphysema of the colonic wall appears, there is a high risk of perforation and immediate colectomy should be considered.

Ulceration

Ulcers in the stomach, pylorus and duodenal bulb may heal with scar formation, secondary stenosis, gastric retention and dilatation. In the erect view, this is seen as a long air-fluid level in the fundus, close to the left hemi-diaphragm. An ulcer may also be complicated by perforation into the abdominal cavity and lesser sac. A perforated ulcer is, in fact, the underlying pathology in four out of five patients presenting with free abdominal gas. If the perforation is rapidly sealed by omentum, only a small volume of gas may escape, which is hard to detect radiographically unless CT is used or the perforation itself is outlined by a suitable water-soluble contrast material such as Gastrografin (Fig. 19).

A dorsal-wall perforation may fill the lesser sac with gastric contents and induce secondary pancreatitis with its associated complications; the condition is usually readily demonstrated on CT. A non-perforated ulcer is nowadays diagnosed and treated endoscopically.

Figure 19. A patient treated with steroids for psoriatic artritis who suddenly developed severe epigastric pain. Plain abdominal films were within normal limits. A lateral film of the stomach shows leakage of GastrografinR (arrow) through a perforated duodenal ulcer (1 = gastric body, 2 = gastric antrum, 3 = duodenal bulb)

Mechanical bowel obstruction

General considerations

Bowel obstruction leads to a mechanical or dynamic ileus which may be intermittent in cases where the obstruction is incomplete. There are a variety of causes, including postoperative adhesions and peritoneal bands, an obstructing bowel tumour, infiltration from a malignancy adjacent to the bowel, invagination, strangulation, internal or external herniation, and obstruction from ingested material, inflammatory lesions and bleeding into the bowel wall.

The contents of the bowel distal to the obstructive lesion are usually evacuated with gas and fluid accumulate proximally. Peristaltic activity in the proximal bowel is increased in order to overcome the obstruction and this is manifested on auscultation as a change of pitch in the bowel sounds. On abdominal survey films the proximal air-filled bowel loops appear as dark, radiolucent arches. On horizontal-beam films the air-fluid levels in the respective limbs of these arches may reach different heights as a sign of peristaltic activity in the bowel (Fig. 20).

Special considerations
A high mechanical obstruction is a serious condition that can easily be overlooked. An abdominal survey shows an absence of bowel gas, just as in the newborn with oesophageal atresia. Vomiting is the dominant clinical feature.

	Figure 20. Patient with small bowel ileus. Air-fluid levels are seen at different levels in the limbs of dilated small bowel loops. Multiple air-fluid levels are seen as a sign of low small bowel obstruction. The colon is collapsed. There is a gallstone in the gallbladder (arrow). The examination is performed with the patient erect. There is an air-fluid level in the stomach (*) which is normal. Note the spiral arrangement of bowel folds.
a	Figure 21. a) A patient with severe vomiting who had recently undergone an axillofemoral bypass. The plain abdominal film shows a stomach distended with gas in an otherwise gas void abdomen (apart from small amounts in the descending colon). b) The same patient examined in the left lateral decubitus position with an horizontal beam. There are air fluid levels seen in the gastric fundus, duodenal bulb, and descending duodenum (arrow), respectively. (A barium examination of the stomach showed jejunal obstruction due to bleeding as a result of anticoagulant therapy)
b
	Figure 22. CT of the abdomen in a patient with carcinoma of the pancreas and a Roux-en-Y anastomosis. There is obstruction of the Y-loop which is markedly distended (*). Widened intrahepatic biliary ducts are demonstrated and the wall of the abdominal aorta is calcified

Gastric retention is usually caused by a stenosis secondary to peptic ulcer disease. Other less common causes are duodenal obstruction due to intramural bleeding secondary to trauma or anticoagulant therapy. In patients with duodenal obstruction, however, gas is present in both the stomach and duodenal bulb (Fig. 21). Another cause of high mechanical obstruction is invagination of the afferent loop after a Billroth Il stomach resection (Fig. 22).

Small bowel ileus
Organic obstruction of the small bowel leads to proximal dilatation with emptying of the bowel (including the large bowel) distal to the site of the obstruction. The fewer the number of dilated loops seen, the higher the level of the obstruction. The presence, therefore, of multiple air-fluid levels in the small bowel indicates a distally located obstruction (Fig. 20).

In long-standing obstruction the small bowel can dilate enormously and come to resemble the colon. The mucosal pattern, however, i.e. the folds of Kerkring which traverse the bowel in a spiral fashion, may help to distinguish between dilated small bowel and colon (Fig. 9)

Large bowel ileus
The more distal the obstruction the more colon is dilated proximally, while the bowel below the lesion and the rectum are empty (Fig. 23). Even if the obstruction has lasted for only a few hours the small bowel may be dilated.

a	Figure 23. a) Air-fluid levels are shown in the dilated ascending, transverse and descending colon in a patient with large bowel obstruction. b) Barium study showing complete obstruction at the transition between the rectum and sigmoid colon; the proximal colon is distended with gas (arrow). c) Ultrasound examination showing a dilated caecum and the distal ileum distended with fluid.
b
c

Intussusception
Ileocaecal invagination in children does not necessarily produce any radiological abnormality. Clinical suspicion of this condition, therefore, should always lead to a large bowel examination, using either barium or CO2 insufflation (i.e. pneumocolon). With either method the invaginated small bowel will be delineated by the introduced contrast. The condition

	Figure 24. Ultrasound examination of an ileo-ileal invagination (intussusception) in a child showing the typical appearance of a "bowel (t) within a bowel (t) ".
a	Figure 25. a) Gas is seen in the extrahepatic biliary tree (arrow) and in the gallbladder (*) in a patient with gallstone ileus. The small bowel loops are wide (arrowhead) and filled with fluid. The intraluminal gas is outlining the mucosal folds. b) A fistula (1) from the gallbladder to the duodenum was demonstrated during a barium follow-through in a patient with an entrapped gallstone (2) in the mid-small bowel.
b

may also be diagnosed by ultrasound in which its characteristic feature is an onion-like formation (Fig. 24).

The intussusception may be reduced by increasing the intraluminal pressure with either barium or CO2, at a pressure corresponding to 1.5 m of water, and gentle manipulation of the abdomen. If the patient shows any signs of ileus, however, the reduction must be performed with

Figure 26.Strangulation ileus. An ultrasound examination shows fluid in dilated small bowel loops (arrows). extreme caution to avoid rupture of a potentially strangulated bowel loop and many authorities consider this radiological manoeuvre to be contraindicated in such circumstances.

Gallstone ileus
In patients with chronic cholecystitis a gallstone may erode through a fistula from the gallbladder to the bowel. Depending on the size of the stone and the level of the fistulous communication (duodenum, ileum or right colonic flexure) the stone may get stuck at one of a number of different levels, e.g. the bulb, the sigmoid colon, or, as is most often the case, the distal ileum (Fig. 25). Gas passes spontaneously through the fistula into the gallbladder and biliary tree and this combination of biliary gas and mechanical obstruction is pathognomonic for gallstone ileus.

Strangulation
Depletion of the supply of oxygenated blood to the bowel creates alarming clinical symptoms and the affected bowel loop soon fills with haemorrhagic fluid (Fig. 26). On abdominal survey films a rounded mass is seen together with signs of obstruction but the true cause is seldom diagnosed preoperatively.

Small bowel volvulus
Rotation of the small bowel around its mesentery is a rare entity. Dilated bowel loops are seen, orientated like a "spiral nebula" in the mid abdomen (Fig. 27).

Figure 27. Volvulus of small bowel around an adhesion. The appearance looks like a spiral nebula and this is caused by progressive gaseous distension of the small bowel which forces it to rotate around its mesenteric root.

Large bowel volvulus
Colonic volvulus is much commoner than small bowel volvulus. The cause is an incomplete fixation of the bowel which may thereby form slings. The most common form of volvulus occurs in the sigmoid and is seen in debilitated and elderly patients.

Radiologically a gas-filled sigmoid loop is seen which may reach up to the right upper quadrant. Proximal parts of the large bowel are filled by air and faeces (Fig. 28). The volvulus may be reduced by the use of a semi-stiff tube with a smoothly rounded tip and drainage holes. The tube is introduced during fluoroscopic control and carefully advanced beyond the torsion into the dilated loop. When gas and foul smelling fluid are suddenly expelled from the tube the bowel collapses and the patient recovers immediately. There is, however, a great tendency for the volvulus to recur.

Volvulus of the caecum is seldom complete and often overlooked. The cause is a mobile caecum in a patient with a distal obstruction. A colonic carcinoma in the left colon may cause volvulus of the right colon up to the right flexure. Abdominal survey films show a distended loop of the bowel, resembling a kidney (Fig. 29), which may be located anywhere in the abdomen. Gas and faecal materials may still be seen in the distal

a	Figure 28. a) Volvulus with marked distension of the sigmoid colon up to the right hemidiaphragm. Moderate dilatation of the rest of the colon. b) A barium enema shows a twist in the bowel at the level of the distal sigmoid.
b

colon indicating that the torsion is incomplete. All types of colonic volvulus are verified by means of a barium enema that reveals a beak-shaped deformity corresponding to the site of torsion (Fig. 29).

Comments
The further evaluation of a patient with an acute abdomen and abnormal survey films should always be a matter for consultation between the radiologist and the referring clinician. If the patient is to undergo further

a	Figure 29. a) There is a long air-fluid level in the pelvis in a patient with distension of the caecum (arrows). b) A barium examination shows a beak-like deformity of the proximal ascending colon signifying a caecal volvulus (arrow).
b

examinations with ultrasound, CT and/or angiography then any barium examinations should be postponed.
Patients with a definite diagnosis of mechanical obstruction are very likely to benefit from CT which often not only confirms the diagnosis but also establishes the underlying cause such as an abscess or a malignant lesion. If no definite actiology is ascertained then an adhesion is likely to be the cause of the obstruction. Transabdominal ultrasound may also be considered, but this technique is much more operator dependent than CT. The large amount of gas present in patients with dynamic ileus also contributes to the difficulties of making an ultrasound diagnosis. Intussusception, however, is usually easy to reveal with ultrasound (Fig. 24).

a	Figure 30. a) Chronic ileus in a woman with advanced ovarian carcinoma that has developed into a paralytic ileus with long air-fluid levels. b) Postoperative paralytic ileus. A left decubitus view shows a long fluid level in the colon.
b

It is normal practice to verify the level and type of any obstruction with either a barium follow-through or enema. If the level of the obstruction is unclear, a barium enema should always be performed first.

In order to speed up the diagnosis when a follow-through examination is being performed, GastrografinR may be added to the bariumsulphate in the proportion l :4. The radiographic examination should start 15 minutes after this is ingested and be repeated at regular intervals. When the

Figure 31. Pseudo-obstruction in a patient with Parkinson 's disease. There is dilatation of both large and small bowel loops.

contrast medium has reached the obstruction, spot films are taken during fluoroscopy for detailed assessment of the situation.

Paralytic ileus

Adynamic ileus is often seen after abdominal surgery and as a secondary complication of peritonitis and circulatory insufficiency, but it can also occur as a sequel to longstanding dynamic ileus (Fig. 30). Intoxication or glucose and electrolyte imbalance may also cause adynamic ileus.

The abdominal survey films show slightly gas-distended small bowel loops with long air-fluid levels, signifying lack of bowel activity, i.e. a "silent abdomen". If there is peritonitis as well, fluid is present in the peritoneal cavity. Pseudo-obstruction without any known aetiology can be seen in the elderly (Fig. 31), a condition that is fatal if the bowel is not decompressed by surgery or colonoscopy.

Ischaemia

Acute bowel ischaemia may be caused by embolism or thrombosis in the mesenteric vessels, but is more often caused by a low arterial blood flow without evidence of obstruction. The circulatory insufficiency causes

a	Figure 32. a) Gas in the portal vein has a tendency to accumulate in the periphery of the liver (arrows) while gas in the biliary tree collects in the hilar region. b) A plain abdominal film shows gangrenous bowel with gas in the rectal wall down to the anus (arrows).
b

oedema and bleeding in the bowel wall. Radiologically localized polypoid swellings of the bowel wall resembling thumbprints are seen. The ischaemic segment becomes paralysed and fills with fluid, resulting in an increase in the intraluminal pressure. This may lead to ulceration and necrosis of the mucosa and gas may pass through the bowel wall into the splanchnic and portal veins (Fig. 32). This is often fatal as a result of extensive bowel necrosis. The thickened bowel wall is often readily demonstrated on CT and ultrasound, both of which can be used to monitor the course of the disease.

Abdominal aortic aneurysm

Middle-aged and elderly patients who develop acute abdominal pain and in whom a palpable pulsatile mass is found in mid-abdomen should be suspected of having an abdominal aortic aneurysm. The quickest and easiest way to detect an abdominal aortic aneurysm is by ultrasound and this shows not only its size but also whether or not blood has dissected between the intimal and serosal layers of the vessel. CT is, however, the method of choice as it is a superior method for imaging and subsequently monitoring both the aneurysm and its potential complications. The

Figure 33. Rupture of the left renal artery. The left kidney (1) is displaced anteriorly owing to a perirenal

dissection is delineated by an intravenous injection of contrast medium as is the perfusion status and function of the kidneys. The thoracic aorta should also be examined which, again, is best done with CT. A routine examination should, therefore, start at the level of the cervical vessels and end below the aneurysm.

Extrauterine pregnancy (EUP)

In a fertile woman presenting with sudden, severe pain in the lower abdomen the diagnosis of an extrauterine pregnancy should be suspected. After the pregnancy has been confirmed by analysing the urine for the presence of HCG, the patient should undergo an ultrasound examination in order to detect or exclude the presence of an EUP. If an ectopic pregnancy is present it can usually be visualized directly as a localized swelling in the fallopian tube, often accompanied by evidence of bleeding into the peritoneal cavity.

Another cause of pain in the lower abdomen of a fertile woman is a tubo-ovarian abscess, which is easily detected by ultrasound as a fluid filled, low-echogenic mass in the true pelvis.

Abdominal trauma

Blunt abdominal trauma may cause bowel wall bleeding (see above), but can also cause rupture of solid organs and vessels and patients presenting with a history of such trauma should be examined with CT. Abdominal survey films may, however, demonstrate enlargement of organs or loss of normal contours owing to the infiltration of surrounding fat planes by ascites, blood, bile and oedema. The patient may also present with peritonitis. Rupture of a kidney or the urinary bladder can be detected during intravenous urography as leakage of opacified urine.

Patients who have suffered blunt abdominal trauma to the abdomen and have symptoms of intra-abdominal injury should undergo CT (Fig. 33). No special preparation is necessary, but a gastric tube will usually already be in place. Intravenous contrast enhancement is essential but oral contrast medium is not usually employed in these circumstances. A tear or area of bleeding in a parenchymatous organ is seen as a low attenuation area and the diagnosis of such a lesion is often dependent on the demonstration of defective enhancement in that particular area. Bleeding into the general peritoneal cavity can sometimes be seen as a relatively high attenuation fluid collection in the peritoneal cavity. The thoracic cavity should always be included in the CT study.

Patients who have suffered penetrating trauma may have damage to parenchymatous organs and/or perforation of the bowel. Similar lesions can also be caused by blunt abdominal trauma and should be excluded by CT.

Gastrointestinal bleeding

Patients who bleed from the gastrointestinal tract often undergo a substantial array of examinations. In a patients with chronic bleeding the following steps are recommended: fibreoptic-endoscopy of the oesophagus stomach and duodenum; colonoscopy, and scintigraphy. If the se studies are negative, barium examinations of the entire gastrointestinal tract should be performed and angiography may eventually be required. During ongoing bleeding an emergency angiography should be considered. The examination should be performed with selective catheterization of the coeliac trunk:, superior and inferior mesenteric arteries with super-selective studies as appropriate. The examination is often complicated in these severely sick patients. Common bleeding sources in elderly patients are arteriovenous malformations which are usually seen in the ileocoecal area. The source of bleeding can be detected either by the demonstration of leakage of contrast medium into the bowel lumen or by the identification of a vascular lesion likely to be responsible for it. Another cause of bleeding is bowel ischaemia, usually seen in the colon. Bowel ischaemia is frequently caused by a low perfusion pressure that causes secondary bleeding owing to non-occlusive hypoxia which cannot be detected during angiography. Bleeding from the gastrointestinal tract is often intermittent and angiography may be required on several occasions before the correct diagnosis is established. For a more detailed discussion on gastrointestinal bleeding; see chapter 22.

 

David J. Allison, Olle Ekberg and Frans-Thomas Fork