Ross & Wilson Anatomy and Physiology in Health and Illness (149 page)

Figure 12.47 
Peptic ulceration:
a large duodenal ulcer.

Blood supply

Reduced blood flow and ischaemia may be caused by excessive cigarette smoking and severe stress, either physical or mental. In stressful situations the accompanying sympathetic activity causes constriction of the blood vessels supplying the alimentary tract.

Secretion of mucus

The composition and the amount of mucus may be altered, e.g.:

•
by regular and prolonged use of aspirin and other anti-inflammatory drugs

•
by the reflux of bile acids and salts

•
in chronic gastritis.

Epithelial cell replacement

There is normally a rapid turnover of gastric and intestinal epithelial cells. This may be reduced:

•
by raised levels of steroid hormones, e.g. in response to stress or when they are used as drugs

•
in chronic gastritis

•
by irradiation and the use of cytotoxic drugs.

In peptic ulcer disease, the alimentary tract is commonly colonised by the bacterium
Helicobacter pylori
, a causative agent in this disorder.

Acute peptic ulcers

These lesions involve tissue to the depth of the submucosa and may be single or multiple. They are found in many sites in the stomach and in the first few centimetres of the duodenum. Their development is often associated with acute gastritis, severe stress, e.g. severe illness, shock, burns, severe emotional disturbance and following surgery. Healing without the formation of fibrous tissue usually occurs when the stressor is removed, although haemorrhage, which may be life-threatening, can be a complication.

Chronic peptic ulcers

These ulcers penetrate through the epithelial and muscle layers of the stomach wall and may include the adjacent pancreas or liver. In the majority of cases they occur singly in the pylorus of the stomach and in the duodenum. Occasionally there are two ulcers facing each other in the duodenum, called kissing ulcers.
Helicobacter pylori
is found in 90% of people with duodenal ulcers and 70% of those with gastric ulcers. The remaining gastric ulcers are almost entirely due to non-steroidal anti-inflammatory drugs (NSAIDs). Smoking predisposes to peptic ulceration and delays healing. Healing occurs with the formation of fibrous tissue and subsequent shrinkage may cause:

•
stricture of the lumen of the stomach

•
gastric outflow obstruction or stenosis of the pyloric sphincter

•
adhesions to adjacent structures, e.g. pancreas, liver, transverse colon.

Complications of peptic ulcers

Haemorrhage

When a major artery is eroded a serious and possibly life-threatening haemorrhage may occur, causing shock (
p. 111
), haematemesis and/or melaena.

Anaemia

Chronic persistent low level bleeding from an ulcer may lead to development of iron deficiency anaemia (
p. 66
).

Perforation

When an ulcer erodes through the full thickness of the wall of the stomach or duodenum their contents enter the peritoneal cavity, causing acute peritonitis (
p. 317
).

Infected inflammatory material may collect under the diaphragm, forming a
subphrenic abscess
(
Fig. 12.48
) and the infection may spread through the diaphragm to the pleural cavity.

Gastric outflow obstruction

Also known as
pyloric stenosis
, fibrous tissue formed as an ulcer in the pyloric region heals, causes narrowing of the pylorus that obstructs outflow from the stomach and results in persistent vomiting.

Development of a malignant tumour

This is frequently associated with chronic gastritis caused by
Helicobacter pylori
.

Tumours of the stomach

Benign tumours of the stomach occur rarely.

Malignant tumours

This is a common malignancy that occurs more frequently in men than women. The causes have not been established, but there appears to be a strong link with
Helicobacter pylori
infection, dietary factors and some, as yet unknown, environmental factors. The local growth of the tumour gradually destroys the normal tissue so that achlorhydria (reduced hydrochloric acid secretion) and pernicious anaemia are frequently secondary features. As the tumour grows, the surface may ulcerate and become infected, especially when achlorhydria develops.

This condition carries a poor prognosis because spread has often already occurred prior to diagnosis. Commonly tumour fragments have been spread in the blood through the hepatic portal vein to the liver where they lodge and cause metastases. Local spread is to adjacent organs, e.g. the oesophagus, duodenum and pancreas. Transmission to the peritoneal cavity may occur when the outermost layer, the serosa, is affected. Lymphatic spread is also common, initially to nearby nodes and later to more distant ones.

Congenital pyloric stenosis

In this condition there is spasmodic constriction of the pyloric sphincter, characteristic projectile vomiting and failure to put on weight. In an attempt to overcome the spasms, hypertrophy of the muscle of the pylorus develops, causing obstruction of the pylorus 2 to 3 weeks after birth. The cause is not known but there is a familial tendency and it is more common in boys.

Diseases of the intestines

Learning outcomes

After studying this section, you should be able to:

describe appendicitis and its consequences

discuss the principal infectious disease of the intestines

compare and contrast the features of Crohn’s disease and ulcerative colitis

distinguish between diverticulitis and diverticulosis

describe the main tumours of the intestines

describe the abnormalities present in hernia, volvulus and intussusception

list the main causes of intestinal obstruction