Intestinal Obstruction

Intestinal Obstruction

Definition

“

Inability of the intestinal contents to pass distally in the lumen of intestine either from a mechanical barrier or absence of peristalsis without any mechanical barrier is known as Intestinal obstruction

.”

Mortality and Morbidity depend upon the early recognition and correct diagnoses of obstruction.

If untreated death occur in 100% of patients with

strangulated obstruction.

Classification

Intestinal obstruction can be classified in many ways.

Depending upon the nature of obstruction

Dynamic obstruction

Adynamic

obstruction

.

Dependind upon the Cause of obstruction

Intraluminal

causes

Gall stones

ileus

Food bolus obstruction

Roundworm mass

Foreign body

In the wall of the Gut

Strictures

Crohn’s

disease

Carcinomas

Adhesions

Outside the wall of the Gut

Volvulus

Intussusception

Obstructed Hernia

Congenital Bands

Classification

Depending upon Severity

Acute Obstruction

Chronic Obstruction

Acute on Chronic Obstruction

Depending upon Blood Supply

Simple Obstruction

Strangulated Obstruction

Depending upon the site

Small bowel obstruction

Large bowel obstruction

Pathophysiology

Irrespective of the etiology and acuteness of onset, in Dynamic obstruction the proximal Bowel dilates and develops an Altered motility.

Dilation

Obstruction leads to proximal dilation due to accumulation of intestinal secretions and swallowed air. this bowel dilation stimulates cell

secretory

activity resulting in more fluid accumulation and progressive dilatation.

Altered motility

accumulation of secretion in the intestine lumen stimulates increased peristalsis both above and below the obstruction . below the obstruction increased peristalsis leads to frequent loose stools and flatus early in the course of disease.

Above the obstruction increased peristalsis try to overcome the

obstruction,if

the obstruction is not relieved the bowel begins to dilate causing a reduction in the peristaltic strength ultimately resulting in flaccidity and paralysis.

Pathophysiology

The distention Proximal to obstruction is caused by two factors

Gas

: obstruction leads to significant proliferation of both aerobic and anaerobic organisms resulting in considerable gas production , Nitrogen being the predominant(90%) Gas along with Hydrogen Sulfide.

Fluid

: Fluid is made up of various digestive juices

e.g

1500ml

of saliva\d

,

2L

of gastric juice\d,

3L

of intestinal secretion\d,

1L

of pancreatic juice and bile\d

. Following obstruction fluids accumulates in the bowel wall and any excess fluid is secreted in the lumen. Because absorption is retarded ,dehydration and electrolytes disturbance is inevitable. Causes include

Reduced oral intake

defective intestinal absorption

result of vomiting

sequestration in bowel lumen

Pathophysiology

Interference with blood supply

: as the tension within the bowel loops become more and more , venous congestion takes place resulting in edema of bowel wall. If the obstruction is not relieved capillary rupture and hemorrhage takes place. In case of

volvulus

and

intussusception

arterial compromise takes place fast which causes gangrene of bowel wall very early.

Transmigration of Organisms

: both aerobic and anaerobic organisms transmigrate through the gangrenous bowel and results in peritonitis. The organism release powerful

endotoxins

which are absorbed from

peritonial

surface and cause gram negative shock or septic shock which caries high mortality.

Clinical Features

There are Four Cardinal features of Dynamic Obstruction.

Colicky pain

Distention

Vomiting

Absolute constipation

The clinical features are also influenced by the

site of

obstruction

whether

small bowel

large bowel

and on the

onset of obstruction

whether

Acute or

Chronic or

Acute on Chronic

Clinical Features

In High Small Bowel Obstruction

Vomiting

occurs early and is profuse with

rapid dehydration

.

Distention

is minimal with little evidence of fluid levels on abdominal radiograph.

In Low Small Bowel Obstruction

Pain

is predominant with

central Distention

.

Vomiting

is delayed. Multiple central fluid levels are seen in abdominal radiograph.

In Large Bowel Obstruction

Distention

is early and pronounced.

Pain

is mild and

Vomiting

and

Dehydration

is late. The proximal colon and

caecum

are distended on abdominal radiograph.

Other Features

Dehydration

: Most common in small bowel obstruction because of repeated vomiting and fluid sequestration. Signs of dehydration appears early

( ? )

Hypokalemia

: not a common feature in simple mechanical obstruction. An increase in serum potassium, amylase and LDH may be associated with presence of Strangulation along with

leucocytosis

or leucopenia.

Pyrexia

: In the presence of obstruction indicates

Onset of Ischemia

Intestinal perforation

Inflammation associated with obstructing disease.

Hypothermia

: Indicates Septic shock.

Abdominal tenderness

: localized tenderness indicates pending and established ischemia.

Signs of

peritonism

: indicates overt infarction or perforation.

Feature of Strangulation

It is important to distinguish strangulating from non-strangulating obstruction because the Former is a surgical emergency. The diagnoses is entirely clinical. Features include

Constant Pain

Tenderness with Rigidity

Guarding and absent bowel sound

Features of Septic Shock

In case of External hernia the lump is tense, tender, irreducible with no

expansile

cough impulse

Pain

is never completely absent in strangulation.

Symptoms Usually commence suddenly and recur regularly.

Any

tenderness

present is of great significance and need frequent reassessment.

Investigations

Complete Blood Picture

: Low

Hb

% indicates underlying malignancy. Increased total WBC count indicates infection or sepsis.

Electrolytes

: most of the electrolytes are low in cases of intestinal obstruction.

Plain X-ray Abdomen

: in erect position is an important investigation in cases of intestinal obstruction.

Multiple gas fluid levels are

pathognomic

of IO. Gas level appears earlier than fluid levels.

Plain X-ray may demonstrate Gall stone

ileus

or foreign body.

Sigmoid

volvulus

appear as a large dilated loop.

Jejunum is characterized by Regularly placed mucosal folds called

volvulae

conniventes

placed opposite to each other. They are produced by valves of

kirkring

.

Large bowel is characterized by

Haustrations

: Incomplete mucosal folds, not placed opposite to each other. They are large.

Caecum

has no

haustrations

. However it appears as a round gas shadow in RIF.

Multiple air-fluid levels

Air-fluid levels

Haustrations

Small bowel obstruction

Treatment of Acute IO

There are Three main measures used to treat acute IO.

Gastro-intestinal drainage

Fluid and electrolyte replacement

Relief of Obstruction

Surgical treatment is necessary for most cases of IO but should be delayed until resuscitation is complete, provided there is no signs of Strangulation or evidence of closed-loop obstruction.

Indications of early surgical intervention

Obstructed or strangulated external hernia

Internal intestinal strangulation

Acute obstruction