Speculum - University of Melbourne

22 SPECULUM
called ileus, in which there is no peristalsis
to carry on the contents: or direct physical
blocking of the tube by an extimsic or intrinsic
factor.
The aetiology of ileus may be classified
A. Paralytic
reflex
anoxic
toxic
chemical
post operative
renal colic
torsion cyst
plaster to trunk
fractured pelvis
bruised abdominal wall
retro-peritoneal haemorrhage
effect of toxims on
Auerbach's plexus.
B. SpastiC
localised contractile phase
site of impaction of gall stone
post-operative from excess handling
acute appendicitis
renal colic
In contrast to this, with physical block
the bowel may go into hyper-peristalsis in
an attempt to overcome the obstruction.
This feature helps to explain some of the
clinical aspects, such as the silent abdomen
of ileus compared with the turbulent noises
in an abdomen with simple obstruction; the
lack of symptoms early in an ileus whilst the
severe colic of some obstructions is too real.
The clinical pictures which present from
obstruction vary considerably with the
level of the obstruction. It is probably
easiest to present the features in the form of
a geometric equation: the height of the obstruction
is proportional to the symptoms
and inversely proportionate to the signs.
That is, a high obstruction near the duodenum
will present with gross symptoms early
with almost no clinical signs, whereas one
distally will cause minor symptoms till the
condition is well established, but the clinical
signs will show early, including rising
pulse rate.
Among the many side effects of the obstruction
is that of distension, which is due
to the accumulation of the contents which
cannot pass on, increased by the normal
secretion of the intestine, and grossly aggravated
by gases which are the effects of the
condition—a form of "fermentation". Distension
causes sympathetic and parasympathetic
disturbances, as well as interfering
with the blood supply of the intestine, thus
causing anoxia.
Indirect effects such as vomiting and increased
peritoneal fluid, add to the disturbances
of body fluid and electrolytes, as
well as generally exhausting the patient.
AETIOLOGY
A simple obstruction of this tube in
which there is no damage of the wall can
result from congenital failures such as
septum of oesophagus, duodenum, or anus,
of ileus, tumours of small bowel, or adhesions.
Where' the cause of the obstruction results
in pressure upon the bowel, avascular
necrosis will occur if the condition is not
relieved, resulting in perforation of the
bowel. Such conditions include bands,
foreign bodies including masses of parasites
or more particularly because of its bad
clinical record: gall stone.
Another new feature added to the simple
hold-up of onward flow of contents can be
the interference with the blood supply of
the intestine. The outstanding example of
this is mesenteric thrombosis; other causes
include strangulated internal or external
hernia, volvulus, and intussusception. This
added phenomenon produces clinical features
further to those of fluid loss and electrolyte
disturbances: those of sympathetic
shock, toxic shock and secondary toxaemia.
This simple tube is functionally, embryologically,
and structurally of two distinct
parts—small intestine and large intestine.
Previous discussion has applied mainly
to the small intestine.
The difference in presentation of the large
intestine can be attributed to such as its
protected position extraperitoneally, its
much reduced activity, and by its structure
a capacity to adjust to increase of contents.
Thus there is a long warning latent period
of obstruction before it becomes dangerous,
and the clinical title of "acute-on-chronic"
is given. The only really acute obstruction