Biology of Disease

cells and the increase in hydrogen carbonate production by mucus secreting
epithelial cells have cytoprotective effects.

Zollinger-Ellison syndrome is a rare disorder that causes massive, multiple
and recurrent peptic ulcers due to the excessive secretion of gastric juice
from tumors affecting the pancreas or duodenum. Approximately 60% of the
tumors are malignant. They are called gastrinomas because they secrete large
amounts of gastrin, hence patients have an increased plasma gastrin concen-
tration and rates of gastric acid secretion greater than 100 compared with nor-
mal rates of less than 5 mmol h–1.

A diagnosis of Zollinger-Ellison syndrome usually requires demonstrating an
increase in the concentration of gastrin in the patient’s serum, combined with
an increased release of acid in the stomach. However, in about 30% of cases
the plasma gastrin concentration is normal or only slightly above normal. The
pentagastrin test is used to assess the acid output of the stomach. Pentagastrin
is an analog of gastrin that stimulates the release of stomach acid. Acid output
is assessed before and after intramuscular injection of pentagastrin. Patients
with Zollinger-Ellison syndrome have a high basal acid output and pentagas-
trin causes little further increase. Treatment of Zollinger-Ellison syndrome is
by surgical removal of the gastrinoma.

Ahernia is the protrusion of an organ or tissue out of the body cavity in which
it is normally found. A hiatus hernia occurs when the upper part of the stom-
ach is dislocated through the hole, called a hiatus, in the diaphragm, into the
chest. Sliding hiatus hernias occur when the esophagus and stomach both
move upwards so that the top end of the stomach protrudes through the gap
in the diaphragm normally occupied by the esophagus (Figure 11.30 (A)) and
these constitute 90% of cases. The remaining 10% are rolling hiatus hernias
where a portion of the stomach curls upwards adjacent to the esophagus
so that both it and an upper part of the stomach protrude through the gap
(Figure 11.30 (B)). The causes of hiatus hernias are unknown but they may be
due to intra-abdominal pressure or weakening of the gastroesophageal junc-
tion caused by trauma or loss of muscle tone. Over 50% of individuals with
hiatus hernia are asymptomatic, but when symptoms do occur, they include
heartburn, which is aggravated by reclining, chest pain, dysphagia, belching,
pain on swallowing hot fluids and a feeling of food sticking in the esophagus.
Although hiatus hernia is not usually serious, it can cause inflammation of
the lower end of the esophagus leading to a back flow of gastric juices; this
is called reflux esophagitis, and it may cause bleeding (perhaps anemia) or a
stricture. Cancer in a hiatus hernia is very rare, but there is a slight increased
risk of it developing in the inflamed area.

DISORDERS OF THE GIT AND ACCESSORY ORGANS

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Rolling

hiatus hernia

Sliding hiatus

hernia

A) B)

Diaphragm

Stomach Figure 11.30Schematic showing (A) sliding and

(B) rolling hiatus hernias.