Biology of Disease

BOX 11.1 Peritonitis

Peritonitis is an inflammation of the peritoneum that lines the

abdominal cavity and covers the surfaces of abdominal organs.

The condition is marked by exudations into the peritoneum of

serum, fibrin, cells and pus. Primary peritonitis is caused by the

spread of an infection from the blood and lymph nodes to the

peritoneum and accounts for less than 1% of all cases. Secondary

peritonitis is the commonest type and occurs when bacteria

enter the peritoneum from the GIT or biliary tract. The symptoms

of peritonitis may include vomiting, swelling of the abdomen,

severe abdominal pain and tenderness, weight loss, constipation

and moderate fever. Its major causes are perforations of GIT wall,

which allows seepage of the luminal contents into the abdomi-

nal cavity. These can arise from a ruptured appendix or from per-

forations of the stomach, including damage from ulcers, and gall

bladder. Pelvic inflammatory disease in sexually active women is

also a common cause. Peritonitis can also develop after surgery

when bacteria have been allowed to enter the abdomen during

an operation.

Peritonitis must be rapidly diagnosed and treated because com-

plications can occur rapidly. Diagnosis relies on taking a medi-

cal history and a physical examination, particularly to investigate

any abdominal swelling and tenderness. Diagnostic tests include

using X-rays or a CT scan (Chapter 18) of the abdomen to confirm

the presence of fluid, accumulation of pus or infected organs

in the abdomen. Microbiological tests on samples of blood

or abdominal fluid can identify the causative microorganism.

Peritonitis is frequently life-threatening and acute peritonitis is a

medical emergency. The outlook for untreated patients is poor.

Specific treatments for peritonitis depend on the age, health,

medical history and the severity of the condition. Treatment is

generally aimed at treating the underlying condition. Antibiotics

are given immediately once peritonitis has been diagnosed. A

nasal tube may be inserted into the stomach or intestine to drain

fluid and gas. Peritoneal lavage, where large amounts of fluid are

injected into the peritoneum to wash out the infective microor-

ganisms causing the condition, may be desirable. Intravenous

fluids are also given to replace lost body fluids. Morphine may

be prescribed in hospitalized patients to reduce pain. Emergency

exploratory surgery may be necessary, especially in cases that

involve appendicitis, a perforated peptic ulcer or diverticulitis.

X]VeiZg&&/ DISORDERS OF THE GASTROINTESTINAL TRACT, PANCREAS, LIVER AND GALL BLADDER

'-% W^dad\nd[Y^hZVhZ

Abdominal

cavity

Abdominal

wall

Peritoneum

Mesentery

or

mesocolon

carrying blood

vessels and nerves

Intestine Liver

Figure 11.4Schematic showing a transverse of

the mesentery and mesocolon.

day. Within the tissues of the pancreas are groups of cells called the islets of

Langerhans. The cells in the islets have endocrine functions and produce and

secrete the peptide hormones glucagon and insulin that regulate the concen-

tration of glucose in the blood (Chapter 7).

The liver is the largest organ in the body (Figure 11.1(A) and (B)), weighing

about 1.5 kg. It has two major lobes, each divided into functional units called

lobules. Lobules consist of cuboidal cells arranged around a central vein into

which the blood drains. Between the plates of hepatic cells are sinusoids that

are supplied by the portal vein and hepatic artery (Figure 12.2andChapter

12 ). The sinusoids are lined with phagocytic Kupffer cells that belong to the