INTESTINAL OBSTRUCTION
Intestinal obstruction is a partial or complete blockage of the bowel that results in the failure of the intestinal contents to pass through. This interferes with the propulsion of contents in the intestines.
Causes
1) Dynamic – peristalsis is working against mechanical obstruction
a. Luminal
i. Gall stones
ii. Foreign bodies
iii. Faecoliths
iv. Round worms
v. Tumours
vi. Bezoars
vii. Impaction
viii. Imperforate anus
b. Intramural
i. Stricture e.g. Chron’s disease
ii. Congenital stenosis
iii. Malignancy
c. Extramural
i. Adhesions and bands
ii. Strangulated hernia
iii. Intussusception
iv. Volvulus
v. Intra-abdominal tumour
2) Adynamic causes – peristalsis is absent or may be present in a non-propulsive form (pseudo obstruction)
a. Neurogenic obstruction – paralytic ileus (paralysis of the muscularis of the intestine)
b. Vascular obstruction
i. Thrombosis
ii. Embolism
iii. Accidental ligation
c. Myopathies and neuropathies e.g. Hirchsprung’s disease
Mechanisms of Obstruction
1) Volvulus
2) Incarceration
3) Obstruction
4) Intussusception
Pathophysiology of Intestinal Obstruction
In dynamic obstruction the proximal dilates and develops an altered motility Below the obstruction the bowel has normal peristalsis and absorption until it becomes empty, contracts and becomes immobile.
Initially the proximal peristalsis is increased in order to overcome the obstruction
If the obstruction is not relieved the bowel distends resulting in reduced peristaltic force and eventually flaccidity and paralysis causes of proximal distention include gas (overgrowth of aerobic and unaerobic organisms which produce gas) and fluid (accumulation of digestive juices with reduced absorption).
Presentation
Pain – sudden onset, severe colicky central abdominal pain
Vomiting
Constipation – Absolute
Dehydration
Hypokalaemia
Pyrexia
Abdominal distension
Abdominal Tenderness
Diagnosis
Quartet of pain, distension, vomiting and absolute constipation
Investigations
1) Abdominal ultrasound
2) Plain abdominal x-ray – supine, erect
Fluid levels
Gas shadows
Impacted foreign
3) Barium enema
4) CT scan