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.
Give 5 presentations associated with bowel obstruction:
1) vomiting (green, bilious)
2) abdominal distention
3) diffuse abdominal pain
4) absolute constipation and lack of flatulence
5) tinkling bowel sounds on auscultation
What may be heard upon auscultation of an obstructed bowel?
tinkling sound
What colour is the vomit associated with bowel obstruction?
Green
What are important areas to cover when taking a history of a potential bowel obstructed patient?
Features suggestive of malignancy: anaemia, altered bowel habit, rectal bleeding, weight loss
History of previous abdominal surgery, inflammatory bowel disease, diverticulitis or appendicitis
How would bowel ischemia present?
pain out of proportion to clinical examination
fever
tachycardia
How would bowel perforation with peritonitis present?
- Severe abdominal pain
- Abdominal guarding
- Rebound and percussion tenderness
How would perforation with intra-abdominal abscess present?
- Abdominal pain
- Fever
- Possible palpable mass
How would electrolyte derangement present?
- Confusion and irritability
- Arrhythmia
- Nausea
- Fatigue
How would aspiration pneumonia present?
- SoB
- Productive cough
- Fever
What are some differential diagnoses in the context of abdominal pain and vomiting include?
- Gastroenteritis
- Bowel ischemia
- Acute pancreatitis
- Bowel perforation
Describe the appearance of an obstructed bowel on X-ray:
distended loops of bowel that appear like giant maggots
What is the name given to the muscosal folds in the small bowel that extend the full width?
valvulae conniventes
What is the name of the muscle pouches in the wall of the large intestine that appear as lines that do not extend the full width of the bowel on X-ray?
haustra
How can you differentiate between the small and large intestine on X-ray (when there is an obstruction)?
1) small intestine has lines that extend the full width of the bowel (valvulae conniventes)
2) large intestine has lines that do not extend the full width of the bowel (haustra)
What is the first step of managing bowel obstruction?
ABCDE approach (patient may be haemodynamically unstable due to third spacing, perforation or ischaemia)
What blood marker will be raised in bowel ischaemia?
lactate
Why is it very important to analyse U+Es in bowel obstruction?
electrolyte imbalances are very common
What investigation can be used to test for metabolic alkalosis in bowel obstruction?
VBG
Why are bowel obstruction patients at a higher risk of metabolic alkalosis?
they vomit high concentrations of stomach acid
What is the main initial management strategy for bowel obstruction?
Drip and suck
Describe the Drip and Suck management for bowel obstruction:
1) DRIP: IV fluids
2) SUCK: remove all stomach contents (nil by mouth, NG tube)
What imaging is the typical diagnostic method of choice for bowel obstruction?
contrast CT scan (can establish the site and cause of obstruction)
What does air under the diaphragm on X-ray indicate?
intra-abdominal perforation
Give 4 types of surgeries that may be used to treat bowel obstruction:
1) exploratory surgery (if underlying cause is unclear)
2) adhesiolysis to treat adhesions
3) hernia repair
4) emergency resection of a tumour
Give a treatment for tumour obstruction that can be implemented during colonoscopy
Stenting
What is ileus?
a condition affecting the small bowel where normal peristalsis temporarily stops
Does ileus affect the small or large intestine?
small intestine
What is the most common cause of ileus?
Abdominal surgery
Give 4 common causes of ileus:
1) abdominal surgery (most common)
2) injury to the bowel
3) inflammation or infection of or near the bowel (e.g. peritonitis, appendicitis, pancreatitis)
4) electrolyte imbalances
Give 2 electrolyte imbalances that can cause ileus:
- Hypokalaemia
- Hyponatraemia
Give 5 signs and symptoms associated with ileus:
1) green, bilious vomiting
2) abdominal distention
3) diffuse abdominal pain
4) absolute constipation and absence of flatulence
5) absent bowel sounds (no tinkling)
What will be heard on auscultation of a patient’s abdomen with ileus?
nothing (not even tinkling!)
Give 5 supportive care managements of ileus:
1) nil by mouth
2) NG tube
3) IV fluids (to prevent dehydration and electrolyte imbalances)
4) mobilisation to stimulate peristalsis
5) total parenteral nutrition (may be required whilst waiting for the bowel to regain function
