Intestinal obstruction, Study notes of Pathophysiology

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Intestinal obstruction

Prof. Marek Jackowski

Definition

• Any condition interferes with normal

propulsion and passage of intestinal contents.

• Can involve the small bowel, colon or both

small and colon as in generalized ileus.

Epidemiology  1 % of all hospitalization  3 - 5 % of emergency surgical admissions  More frequent in female patients - gynecological and pelvic surgical operations are important etiologies for postop. adhesions  Adhesion is the most common cause of intestinal obstruction  80 % of bowel obstruction due to small bowel obstruction - the most common causes are:

• Adhesion
• Hernia
• Neoplasm  20 % due to colon obstruction - the most common cause:
  • CR-cancer 60 - 70 %,
  • diverticular disease and volvulus - 30 %  Mortality rate range between 3 % for simple bowel obstruction to 30 % when there is strangulation or perforation  Recurrent rate vary according to method of treatment ;
• conservative 12 %
• surgical treatment 8 - 32 %

Classification

• Cause of obstruction: mechanical or

functional.

• Duration of obstruction: acute or chronic.
• Extent of obstruction: partial or complete
• Type of obstruction: simple or complex

(closed loop and strangulation).

Etiology

Mechanical bowel obstruction:

A. Small bowel obstruction:

1. Adhesion 60 %
2. Hernia 20 %
3. Neoplasm 5 %
4. Volvulus 5 %
5. Others: IBD-GALL STONE-FOREIGN BODY-INTUSSUSCEPTION B. Large bowel obstruction:
6. Cancer 60 %
7. Diverticular disease 15 %
8. Volvulus 15 %
9. Others: hernia – fecal impaction-inflammatory

Etiology

Functional bowel obstruction: 3 types

A. Vascular occlusion ileus.

B. Spastic ileus. (intestine remain contracted and no

propulsive) causes are:

1. Uremia.
2. Porphyria.
3. Heavy metal poison.

C. Adynamic or inhibition ileus:

1. Post operation mostly after abdominal surgery
2. Metabolic causes: hyponateremia-hypokalemia – hypomagnesaemia.
3. Drugs: morphine - antacid-anticonvulsant.
4. Intra-abdominal inflammation – sepsis – occult wound infection.
5. Pneumonia – renal stone – retroperitoneal hematoma – fracture spine and ribs

CAUSES OF I.O (DYNAMIC)

Intraluminal

• Impaction
• Foreign bodies
• Bezoars
• Gallstone Intramural
  • Congenital atresia
  • Stricture
  • Malignancy ( 15 %) Extramural
    • Bands/ adhesion ( 40 %)
    • Hernia ( 12 %)
    • Volvulus
    • Intussusception
    • Tumor- benign/malignant

Pathophysiology: Proximal bowel dilated & develops altered motility  dilate  reduce peristaltic strength  flaccidity & paralysis (prev. vascular damage due to inc. intraluminal pressure) Distal to obs. Bowel exhibits normal peristalsis & absorbtion  become empty  contract & become immobile Distention is by gas & fluid

• Gas: aerobic & anaerobic growth
• Fluid: Digestive juices & retarded absorption Dehydration & electrolytes loss: Reduced oral intake, defective intestinal absorption, loses from vomiting & sequestration in bowel of lumen.

Functional obstruction

 secondary to factors that cause either paralysis or dysmotility of intestinal peristalsis.  Postoperative ileus is the most common form  Postoperative ileus - after intra-abdominal operation  Postoperative ileus correlates with degree of surgical trauma and type of surgery  Different anatomic segments of GIT recover at different rates after manipulation and trauma:

1. Small bowel - hours after operation.
2. Stomach - 24 - 48 hrs.
3. Colon - 3 - 5 days post op.

 should be differentiated from early postoperative mechanical

bowel obstruction:

 Occurs within the first 6 weeks post operation

 Acute adhesions > 90 %

 other causes:

Internal herniation intra-abdominal abscess intramural hematoma anastomatic edema and leak Difficult to differentiate by clinical presentation and X-ray so contrast study and CT scan - helpful

Postoperative ileus

Small Bowel Obstruction

Etiology

• Adhesions
• Malignancy
• External or Internal Hernia
• Volvulus
• Crohn’s Disease
• Intra-abdominal Abscess

Large Bowel Obstruction

Etiology

• Colon Cancer
• Diverticulitis
• Extrinsic Cancer
• Fecal Impaction
• Intussusception
• Volvulus
• Incarcerated Hernias