Chapter 23 OCCULT GASTROINTESTINAL BLEEDING AND IRON DEFICIENCY ANAEMIA

KEY POINTS

• The source of gastrointestinal bleeding is undetected in up to 30% of patients in whom adequate and timely gastroscopy and colonoscopy have been performed.

• Gastrointestinal bleeding may present obviously with melaena, haematemesis or haematochezia, but may also present more subtly, with iron deficiency anaemia, with or without blood in the stools.

• Occult gastrointestinal bleeding may be intermittent or continuous and range from oozing to massive bleeding.

• Most causes of occult gastrointestinal bleeding derive from the small intestine.

• In patients aged 40 years or younger, small intestine tumours, Meckel’s diverticulum, polyposis syndromes and Crohn’s disease are more common causes of occult gastrointestinal bleeding. In patients over 40 years of age, arteriovenous malformation, neoplasia and Dieulafoy’s malformation are more common causes.

• The most common cause of occult small intestinal bleeding, accounting for 80% of cases, is arteriovenous malformation or angiodysplasia.

• Coeliac disease is the most common cause of malabsorption in the Western world and frequently presents with iron deficiency anaemia.

• Non-steroidal antiinflammatory drugs may cause small intestinal inflammation, which may, in turn, result in blood loss.

This chapter concentrates on unexplained or occult gastrointestinal bleeding from the upper gastrointestinal tract and small intestine.

CLINICAL PRESENTATION

If bleeding is overt, patients may present with melaena or haematochezia. Most patients do not have overt bleeding and are observed to have iron deficiency anaemia of varying severity. Some patients are profoundly anaemic, but others may have a more subtle persistent anaemia. Depending on the severity and the rapidity of onset of anaemia, some patients complain of significant lethargy. If the gastrointestinal bleeding is more acute, patients may present with signs and symptoms of hypovolaemia and shock.

AETIOLOGY

Most causes of occult gastrointestinal bleeding derive from the small intestine. In patients aged 40 years or younger, small intestine tumours, Meckel’s diverticulum, polyposis syndromes and Crohn’s disease are more common. In patients over 40 years of age, arteriovenous malformation (the most common cause overall), neoplasia and Dieulafoy’s malformation are more prevalent. Some of the specific causes of gastrointestinal bleeding are listed below.

Arteriovenous malformations

Arteriovenous malformations (AVMs) or angiodysplasias are idiopathic, discrete vascular lesions. AVMs are classically described as occurring in the right colon, but they also occur in the stomach and small intestine. They are the most common cause of small intestinal bleeding, accounting for 80% of cases. The cause of angiodysplasias is not known but they occur with increased frequency in the elderly and in association with other chronic medical conditions such as chronic renal failure, valvular heart disease (particularly aortic stenosis, although this is controversial), scleroderma, von Willebrand’s disease and chronic pulmonary disease.

Bleeding may be occult or severe. The most common presentation is with haematemesis or melaena. The diagnosis of gastric AVMs is made with upper endoscopy and in the small intestine using capsule endoscopy. The lesions are bright red and well circumscribed and they may be flat or raised. It is frequently difficult to determine whether a visualised AVM is the actual bleeding site. Generally, evidence for bleeding is required, as indicated by active bleeding from the lesion or an affixed clot.

Treatment of AVMs focuses on controlling bleeding. Therapeutic endoscopy with a thermal probe or laser therapy is the accepted first-line therapy. Angiographic therapy with Gelfoam embolisation is also appropriate when bleeding is severe and cannot be controlled endoscopically.

Cameron erosions

Linear gastric erosions located at or near the level of the neck of a large diaphragmatic hernia are referred to as Cameron erosions. The diagnosis is made endoscopically following a thorough examination of the hiatal hernia sac. Patients with Cameron ulcers present with acute upper gastrointestinal bleeding (haematemesis or melaena) or chronic blood loss (faecal-occult-blood-test-positive stools or iron deficiency anaemia). The pathogenesis of these lesions is postulated to involve mechanical trauma; with respiratory excursions, the gastric mucosa at the level of the

TABLE 23.1 Aetiology of occult gastrointestinal bleeding

Hiatal hernia Cameron erosions	Small intestine • Portal hypertensive intestinal vasculopathy • Neoplasias (leiomyoma, leiomyosarcoma, carcinoma) • Crohn’s disease • Arteriovenous malformation (angiodysplasia) • Aorto-enteric fistulas • Radiation ileitis • Meckel’s diverticulum • Polyposis and Peutz-Jeghers syndrome • Medication-induced mucosal lesions (non-steroidal antiinflammatory drugs) • Jejunal diverticula • Adenocarcinoma • Carcinoid tumours
Stomach • Portal hypertensive gastropathy • Dieulafoy’s disease • Gastric antral vascular ectasia (GAVE; watermelon stomach) • Arteriovenous malformation (AVM; angiodysplasia)
Biliary tree Haemobilia (trauma or stone)
Pancreas Aneurysm (haemosuccus pancreaticus)	Colon Arteriovenous malformation (angiodysplasia)

neck of the hernia rub against adjacent mucosa. The mainstay of medical treatment is acid suppressive therapy. If blood loss is severe or persistent, or if the ulceration of hernia is complicated, surgical repair of the hernia should be considered.

Gastric antral vascular ectasia

Gastric antral vascular ectasia (GAVE), or watermelon stomach, results from ectatic mucosal and submucosal capillaries. Typically, patients present in their 70s (age range 50–90 y) with occult or slow gastrointestinal bleeding. Endoscopically, GAVE appears most commonly as raised, convoluted, red antral folds radiating in a spoke-like pattern towards the pylorus. This appearance of GAVE has been likened to the stripes on a watermelon rind. A more diffuse involvement of the stomach is also recognised in which many ectasias coalesce to form a large red lesion resembling honeycomb.

Endoscopic thermal ablation therapy using heater probes or Argon plasma coagulator is accepted first-line therapy for control of gastrointestinal bleeding due to GAVE. Treatment coagulates the lesion, with success rates of 90% achievable.

Portal hypertensive gastropathy

Portal hypertensive gastropathy (PHG) is a vascular disorder, which is recognised to be a complication of advanced liver disease. Although its pathogenesis is directly related to portal hypertension, the exact mechanisms involved in the development of this condition remain unclear. On endoscopy, the characteristic lesion is a mosaic pattern of small, raised erythematous areas outlined by a white or yellowish reticular pattern resembling that of snakeskin. PHG is more commonly localised to the proximal stomach.

Mild PHG is generally of no clinical significance and can be considered an incidental endoscopic finding in patients with portal hypertension. In contrast, severe PHG is associated with a high risk of gastrointestinal bleeding. Bleeding characteristically presents as chronic mucosal oozing with the development of iron deficiency anaemia, but may occasionally be acute.

The treatment of PHG consists of addressing the underlying portal hypertension. Unlike variceal bleeding, this condition cannot be treated with band ligation. Effective treatment requires a reduction in portal pressure. This can be accomplished with β-blockers, such as propranolol, portal decompression using radiological placement of a transjugular, portosystemic intrahepatic shunt, or surgical shunting. Somatostatin infusion is routine first-line treatment for actively bleeding cirrhotic patients with PHG.

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