Chronic intestinal obstruction
The symptoms of chronic intestinal obstruction
may arise from two sources — the cause and the subsequent obstruction.
The
causes of obstruction may be organic:
•
intramural — faecal impaction;
•
mural — colorectal cancer, diverticulitis, strictures (Crohn’s
disease, ischaemia), anastomotic stenosis;
•
extramural — adhesion (small bowel only), metastatic deposits,
endometriosis;
•
functional — Hirschsprung’s disease, idiopathic megacolon,
pseudo-obstruction.
The symptoms of chronic obstruction differ in
their predominance, timing and degree from acute obstruction. Constipation
appears first. It is initially relative and then absolute, associated with
distension. In the presence of large bowel disease, the point of greatest
distension is in the caecum and this is heralded by the onset of pain. Vomiting
is a late feature and therefore dehydration is exceptional. Examination is
unremarkable, save for confirmation of distension and the onset of peritonism in
late cases. Rectal examination may confirm the presence of faecal impaction or a
tumour.
Investigation
Plain abdominal radiography may confirm the
presence of large bowel obstruction. All such cases should be confirmed by a
subsequent single contrast water-soluble enema study to rule out functional
disease. Organic disease requires a laparotomy, whilst functional disease
requires colonoscopic decompression and conservative management.
In
the presence of organic obstruction, after resuscitation surgical management
depends on the underlying cause and the relevant chapters in this book should be
consulted.
Hirschsprung’s
disease
This is due to failure of complete migration
of the ganglion cells of the large bowel to the anus. This results in an
aganglionic segment producing physiological obstruction. Eighty per cent present
in the neonatal period with acute large bowel obstruction, whilst 20 per cent
present with failure to thrive or severe constipation.
Barium
enema reveals a characteristic narrow segment, whilst a full-thickness rectal
strip biopsy will show absence of ganglion cells. The rectoanal inhibitory
reflex is absent on physiological testing.
Treatment
consists of an initial loop colostomy followed by a definitive pull-through
procedure.