Intestinal obstruction Flashcards
What is the definition of intestinal obstruction?
Failure of downward passage of intestinal contents
What is meant by dynamic intestinal obstruction?
There is increasing peristalsis working against an obstructing agent
What is adynamic intestinal obstruction?
Peristalsis is absent or ineffective and there are no effective propulsive waves
What is a simple obstruction?
Obstruction of the intestinal lumen without interference with its blodd supply
What happens above the site of obstruction in someone with a simple obstruction?
Peristalsis + distention (due to gas, GI content and fluid build up)
What are causes of death in simple bowel obstruction?
- Fluid & electrolyte imbalance
- Peritonitis
What is strangulation?
Intestinal obstruction with persistent interference of the blood supply
What are causes of intestinal strangulation?
- Strangulated hernia
- Intussuception
- Adhesive intestinal obstruciton
- Volvulus
- Vascular occlusions
What are the pathophysiological consequences of strangulation?
- Venous return is impaired - strangulated bowel and its mesentery look congested
- Serosanguinous fluid formation - accumulated inside the peritoneal cavity
- Arterial supply is impaired - colour of the affected segment becomes black
What are causes of death in strangulation?
- Peritonitis due to perforation
- Hypovolaemic shock
- Sepsis
What is a closed loop obstruction?
When some part of the gut is closed at both ends - THIS IS DANGEROUS
What are causes of small bowel obstruction?
- Adhesions
- Hernias
- Malignant tumours
- Crohn’s disease
- Intussusception
- Gallstone ileus
- Paralytic ileus
- Miscellaneous (bezoars)
What is the most common cause of small bowel obstruction?
Adhesions
What are abdominal adhesions?
Adhesions are bands of ‘scar’ tissue in various degrees of development. They are part of a normal intra-abdominal repair process following a variety of insults
What is the pathophysiology behind abdominal adhesion formation?
Peritoneum is ‘injured’ -> reparative process similar to that seen following the formation or in prevention of a thrombus.
What types of internal hernias can occur which can lead to small bowel obstruction?
- Paraduodenal
- Transmesocolic
- Transmesenteric
- Omental
- Retroanastomotic - bowel is trapped behind a surgical anastomosis
What types of benign tumours of the small intestine can cause SBO?
- Hyperplastic polyps
- Lipomas
- Adenomas - including Peutz-Jeghers polyps
- G/I stromal tumors
- Hemangiomas
What secondary malignancies can present as SBO?
- Ovarian
- Stomach
- Pancreas
- Colonic
- Malignant melanoma
- Lung
- Breast
How can crohn’s disease lead to SBO?
Can cause strictures. May also have adhesions from previous surgeries
What are causes of paralytic ileus?
- Post surgery especially for peritoneal sepsis
- Drugs - TCAs
- Spinal injury
- Electrolyte imbalance - hypokalaemia, hyponatraemia, uraemia
- Extensive handling of the bowel at operation
How does paralytic ileus increase the risk of adhesion formation?
- Intestinal segments have more prolonged contact, which allows fibrous adhesions to form
- Intestinal distention causes serosal injury and ischemia
What are the pathophysiological consequences of small bowel obstruction?
- Proximal dilatation of intestine - due to accumulation of GI secretions and swallowed air
- Stimulation of columnar cell secretory activity - increase in intra-lumenal fluid
- Increased peristalsis above and below the obstruction -
- Early frequent loose stools and flatus
- Increased intraluminal pressure
What is the result of small bowel obstruction in terms of fluid balance?
Hypovolaemia - due to:
- Compression of mucosal lymphatics -> lymphoedema of the bowel wall
- High intraluminal hydrostatic pressures -> increased hydrostatic pressure in the capillary beds
- Massive loss into the third space - fluid, electrolytes, and proteins (into lumen)
- Vomiting + loss of normal fluid intake
How does intestinal obstruction affect intestinal flora?
- Proliferation proximal to obstruction
- Microvascular changes in bowel wall -> Translocation of bacteria to mesenteric lymph nodes
- Resultant bacteraemia
What are symptoms of small bowel obstruction?
- Pain
- Vomiting
- Abdominal distention
- Absolute constipation - late symptom
What are signs of SBO?
- Features on inpection - surgical scars, visible peristalsis
- Dehydration/Signs of shock
- Abdominal distention
-
Bowel sounds
- Increased/borborygmus - early dynamic
- Decreased/absent - paralytic and late mechanical
- May have signs of peritonism
- Empty rectum on PR
- May have herniation - non-reducible
What are the characteristic features of abdominal pain in intestinal obstruction?
Generalized abdominal colicky pain - Each attack lasts for few minuets then gradually disappears, with periouds of relief in between
When is distention less prominent in SBO?
When the obstruction is more proximal