Intestinal obstruction and ileus Flashcards
What is a bowel obstruction?
when the passage of food, fluids and gas through the intestine becomes blocked
Describe the pathophysiology of bowel obstruction:
obstruction results in a build up of gas and faecal matter proximal to the obstruction, causing a back pressure that results in vomiting and the dilatation of the intestines
What is more common, small or large bowel obstruction?
Small bowel obstruction
How severe is a bowel obstruction?
It is a surgical emergency
What are the two main types of bowel obstruction?
- Mechanical
- Functional
What is mechanical obstruction?
obstruction due to a physical blockage within the intestine
What is a functional obstruction?
: due to impaired peristalsis (the normal coordinated movement of the bowel) with no physical blockage
What is a closed-loop obstruction?
Closed-loop obstruction occurs when there is an obstruction at two different points along the same loop of bowel, effectively isolating a section of the bowel.
Closed-loop obstruction is a surgical emergency as the closed-loop will continue to distend and is at high risk of ischaemia and perforation.
Large bowel obstruction with a competent ileocaecal valve also creates a closed-loop picture.
Describe the pathophysiology of third-spacing:
1) the GI tract secretes fluid that is later reabsorbed into the colon
2) where there is an obstruction and this fluid cannot reach the colon, it cannot be reabsorbed
3) as a result there is fluid loss which can lead to hypovolaemia and shock
the higher up the intestine an obstruction is found, the greater the fluid losses
What are the big 3 causes of mechanical bowel obstruction (account for over (90% of cases)?
1) adhesions
2) hernias
3) malignancy
What are the 3 categories of mechanical bowel obstruction?
- Extrinsic (Outside of bowel wall)
- Mural (affecting the layers of the bowel wall)
- Intraluminal (within the bowel lumen)
What are 3 causes of extrinsic mechanical bowel obstruction?
- Adhesions (most common)
- Hernias
- Volvulus
What are 4 mural mechanical obstruction?
- Tumours - most common cause of large bowel obstruction
- Inflammatory strictures (IBD, diverticulitis)
- Intussusception
- Radiation enteropathy
What are 3 causes of intraluminal mechanical bowel obstruction?
- Foreign bodies
- Gallstone ileus
- Faecal impaction
What is a volvulus?
Twisting of the bowel
What is instusscpetion?
where a part of the intestine folds into a section next to it (mostly seen in infants)
What are adhesions?
pieces of scar tissue that can bind abdominal contents together, causing kinking or squeezing of the bowel
Give 4 causes of abdominal adhesions:
1) abdominal or pelvic surgery
2) peritonitis
3) abdominal or pelvic infections
4) endometriosis
Give 4 causes of closed-loop obstruction:
1) two hernias isolate a section of the bowel
2) adhesions compress two areas of the bowel
3) a volvulus twist isolates a section of the intestine
4) a single point of obstruction with a competent ileocaecal valve
Describe how a competent ileocaecal valve with a single obstruction can result in a closed-loop obstruction: (2)
1) a competent ileocaecal valve does not allow any movement back into the ileum from the caeum
2) therefore, there there is a large bowel obstruction, a section of the bowel is cut off and contents cannot flow in either direction
What are risk factors for functional/pseudo-obstruction?
Infection and sepsis
Injury or physical trauma
Postoperative
Cardiovascular disease: myocardial infarction, heart failure, stroke
Metabolic disturbance: electrolyte imbalance, diabetic ketoacidosis
Neurological disease: Parkinson’s disease, Alzheimer’s, multiple sclerosis
Medications: opiates, anti-depressants
What is acute pseudo-obstruction also referred to as?
Ogilvie’s syndrome.