INTESTINAL OBSTRUCTION

BY OSMAN SALAH ALTOHAMY – A MEDICAL STUDENT

UNIVERSITY OF GEZIRA – WAD MEDANI - SUDAN

DEFINITION

Arrest of downward

propulsion of

intestinal contents.

CLASSIFICATION

There are different types of classification of

intestinal obstruction.

According to the pathological nature.

According to the level of the obstruction.

According to the onset and the course of

the obstruction.

According to the pathological nature.

1. Mechanical obstruction: is

caused by an organic block.

2. Paralytic ileus (Adynamic): is

due to loss of propulsive peristalsis

leading to functional obstruction.

According to the level of the obstruction.

1. High small bowel obstruction.

2. Low small bowel obstruction.

3. Large bowel obstruction.

ACCORDING TO THE ONSET

1. Acute .

2. Chronic: e.g., colon cancer, the symptoms are

insidious and slowly progressive. The patient has

constipation and distension.

3. Acute on chronic: A chronic obstruction may

develop acute symptoms as the obstruction suddenly

becomes complete when a narrowed lumen becomes

totally occluded.

ACUTE MECHANICAL INTESTINAL OBSTRUCTION

AETIOLOGY

1. In the lumen, e.g., faecal impaction, gallstone and

parasitic infestation.

2. In the wall, e.g., congenital atresia, tumours, Crohn's

disease, chronic diverticulitis and mesenteric vascular

occlusion.

3. Outside the wall, e.g., adhesions (commonly post-

operative), strangulated hernia, and volvulus.

PATHOLOGY

Distal to the obstruction the intestine empties and becomes

collapsed.

Proximally the intestine becomes distended by gas and fluids.

Gaseous distension is due to swallowed air, diffusion from

congested vessels and bacterial fermentation.

GI secretions (8 litres per day) accumulate above the site of

obstruction.

As intraluminal pressure rises, absorption ceases.

The stretched smooth muscles undergo hyperperistalsis

in an attempt to overcome the obstruction.

Distension impairs blood supply, and may end in

ulceration and perforation.

This is evident in cases of colon obstruction with a

competent ileocaecal valve (closed loop obstruction).

The rising pressure in the closed proximal colon causes

perforation of the caecum.

SYMPTOMS

1. Pain is usually the first symptom. It is colicky and is caused by the

hyperperistalsis.

2. Distension: is marked in large bowel obstruction (mainly in the

flanks). It is less marked and is central in small bowel obstruction.

3. Constipation: is an early symptom in large bowel obstruction but

late in small bowel obstruction.

4. Vomiting occurs early in small bowel obstruction but it is late or

even absent when the large bowel is obstructed.

SIGNS

On General examination: Evidence of dehydration as tachycardia,

oliguria, dry tongue, or even hypotension may be present.

On Abdominal inspection: Distension, visible peristalsis.

Scars of previous abdominal surgery may denote intraabdominal adhesions.

On Abdominal palpation: A mass may be felt (tumour or intussusception).

On Auscultation: Accentuated intestinal sounds.

Rectal examination reveals an empty rectum, or the finding of a hard

faecal mass, especially in elderly bed-ridden patient causing faecal

impaction.

Strangulation is suspected with:

Fever.

Evidence of blood loss as pallor, tachycardia,

and hypotension.

Pain that is not relieved by naso-gastric suction.

Marked tenderness, rebound tenderness, and

rigidity.

INVESTIGATIONS

Aimed to :-

Confirm the diagnosis

Define its level.

Define the aetiology.

Estimate the severity of water and electrolyte

imbalance.

Plain abdominal X-Ray: Multiple gas-fluid levels on an erect film

confirm the case as intestinal obstruction.

On a supine film the level of obstruction is known by the gas pattern of

the distended proximal intestine.

Distended jejunal loops show the characteristic circular mucosal folds

crossing from one side of the lumen to the other.

Distended ileal loops appear as featureless tubes with no mucosal

pattern.

A colon full of gas shows haustrations that do not appear to reach the other side of the lumen.

CBC

Blood urea and electrolytes.

Ultrasound examination can reveal distended

bowel loops. A mass of intussusception can also

be demonstrated.

CT scan with contrast has a sensitivity of 80-90%

for the diagnosis of bowel obstruction.

MANAGEMENT

urgent relief of obstruction,

usually by surgery, after

adequate preoperative

preparation.

PREOPERATIVE PREPERATION

Intravenous replacement of fluid and electrolytes

together with blood and plasma if the patient is

shocked. Ringer's lactate solution is needed.

Gastric aspiration by a nasogastric tube to decompress

the bowel and to reduce the risk of aspiration during

induction of anaesthesia.

Antibiotics are given if there is a possibility of

strangulation.

A Foley catheter is inserted to check the urine output.

THE OPERATION

A longitudinal exploratory incision. In the the case of strangulated

hernia the incision is placed directly over it.

Look at the caecum.

If it is collapsed, this denotes small gut obstruction. If it is distended,

this means large bowel obstruction.

Determine the level of obstruction which is the junction of dilated

and collapsed bowe loops.

Relief of obstruction is attained by division of adhesive bands,

reduction and repair ofa hernia, or untwisting of volvulus.

Assess bowel viability.

Non-viable bowel is known by

Loss of peristalsis,

Loss of normal lustre.

Colour change to greenish or black bowel.

Loss of pulsations in the mesentery.

Resect the Non-viable intestine.

Anastomosis.

CONSERVATIVE

may be successful in certains situations provided thatthere is no clinical

evidence of ischaemia.

Adhesive intestinal obstruction may be relieved by IV drip and nasogastric

suction.

lleocaecal intussusception may be reduced by the hydrostatic effect of a

barium enema.

Sigmoid volvulus. Untwisting may be attempted using a rectal tube passed

through a sigmoidoscope.

Faecal impaction is treated by enema to dissolve the obstructing hard

faecal mass.

* Failure of conservative treatment and the suspicion of strangulation are

indications for surgery.

PARALYTIC ILEUS

is a form of adynamic obstruction in

which there is failure of the peristaltic

waves of the intestine due to failure of the

neuromuscular mechanism.

Paralytic ileus is most common after major

abdominal surgery.

AETIOLOGY

Reflex inhibition of intestinal motility following abdominal

operations retroperitoneal haemorrhage.

Metabolic abnormalities as hypokalaemia, uraemia,

and diabetic ketoacidosis.

Peritonitis induces paralytic ileus due the direct toxic

effect on the nerve plexuses of the intestine.

Drugs as anticholenergics, and tricyclic antidepressants

may produce paralytic ileus if taken in large doses.

CLINICAL FEATURES

Symptoms: Abdominal distension, absolute

constipation, and projectile vomiting . no colicky

abdominal pain but there is only a sense of fullness and

discomfort.

Signs: Abdominal distension and inaudible intestinal

sounds (silent abdomen) .

There may be evidence of localized or generalized

peritonitis.

PREVENTION

Prevention and correction of electrolyte

disturbances guided by serum level estimation.

Gentle handling of the intestine during surgery.

For major abdominal surgery, a naso-gastric

tube is used to decompress the bowel

postoperatively.

MANAGEMENT

Intravenous replacement of the lost fluids and

electrolytes.

Naso-gastric suction.

Correct underlying metabolic abnormalities

Occasionally in resistant cases a

parasympathomimetic, e.g., prostgimine, may

be useful.