Intestinal Obstruction Flashcards
What is intestinal obstruction?
A blockage to the transit of intestinal contents through the gut
What are the 3 categories of obstruction?
- Intra-luminal
- Intramural
- Extra-luminal
What are some causes of intra-luminal obstruction?
Tumours
Gallstones
Meconium disease: first stool of neonate can cause blockage
What are some causes of intramural obstruction?
Inflammation can lead to fibrosis and therefore obstruction: Crohn’s or diverticulitis
Tumours within bowel wall
Neural: Hirschprung’s disease
What is Hirschprung’s disease?
Neonates can be born without innervation all the way through the bowel.
They have an aganglionic segment of bowel
The faeces just doesn’t move down
What are some extra-luminal causes of obstruction?
Adhesions
Volvulus: twist in bowel
Tumour in peritoneum can press on bowel obstructing it
What are adhesions? Why do they occur?
They are when scar tissue forms between the wall of one segment of the bowel and the wall of another segment.
Two segments become attached when they shouldn’t be
Due to surgery usually
How do adhesions cause obstruction?
They cause bits of the bowel to become twisted and trapped so faeces can’t travel through easily
What type of cancer usually causes peritoneal tumours?
Ovarian
What is a volvulus? And which part of the bowel are they common in?
A twist in the bowel
Parts of the colon that have a mesentery: sigmoid or caecum
What’s the difference between mechanical and functional obstruction?
Mechanical: an actual obstruction, something is physically blocking bowel
Functional: paralysis or problem with nerves supplying bowel means no peristalsis so no movement of faeces
What is a pseudo-obstruction?
Obstruction caused by something unknown
What are the complications that can arise from untreated intestinal obstruction?
Ischaemia
Necrosis
Perforation
What are the clinical features of intestinal obstruction?
Vomiting (different types depending on site of obstruction)
Colicky pain
Constipation or no faeces or flatus passed at all
Distention
Tenderness on pressure
Anorexia
Hypovolaemia
Tinkling bowel sounds
What type of vomiting would you see with obstruction:
- high up near stomach
- in the colon?
Near stomach = projectile vomiting
It would occur sooner
In colon = faeculent vomiting
It would occur later
What is meant by ‘proximal dilatation’?
The section of bowel just above the obstruction becomes dilated.
Why does proximal dilation occur in the:
- small bowel
- large bowel?
Small bowel:
there’s a build up of secretions and swallowed air that can’t pass through
Large bowel:
bacterial fermentation releases gases that can’t escape
Why does intestinal obstruction cause decreased blood volume?
The blockage causes fluid and electrolyte imbalance, leading to hypovolaemia
What are the causes of small bowel obstruction (SBO) in adults?
Adhesions (due to past surgery)
Hernia (often incisional)
Crohn’s
Malignancy
What are the causes of small bowel obstruction (SBO) in children?
Appendicitis
Developmental defects
What types of surgery carry a risk of adhesions developing?
Pelvic
Gynaecological
Colorectal
How can hernias cause damage to small bowel?
They can cause strangulation of the bowel as it is forced through a small space it shouldn’t go
What are some risk factors for getting an incisional hernia?
Smoking
Obesity
Cutting across natural lines of muscle
What is intesussception?
The telescoping (invagination) of one bit of intestine into another
Which medical conditions is intesussception associated with?
Cystic fibrosis
Henoch-Schonlein purpura (inflammation of small blood vessels)
What causes intesussception?
An imbalance of the longitudinal forces along the intestinal wall
A disorganised pattern of peristalsis
What is the intussusceptum?
The invaginating portion of bowel in an intesussception
What is the intussuscipiens?
The receiving portion of bowel in an intesussception
While examining the abdomen of a patient with intestinal obstruction, you hear dull sounds? What does this mean?
There is fluid filling the bowel in the area you are examining
While examining the abdomen of a patient with intestinal obstruction, you hear tympanic sounds? What does this mean?
There is gas filling the bowel in the area you’re examining
What sort of bowel sounds do you hear in intestinal obstruction?
Tinkling
These disappear at late stages
What investigations should you do in a suspected SBO?
Blood tests:
FBC, U+E, lactate (increased in some cases of obstruction)
X-ray: look for build up of gas, faeces and ischaemia
CT: use contrast to show up blockage
Ultrasound + MRI
Which people is intesussception most commonly seen in?
Infants + toddlers
What would you find by palpation in a patient with intesussception?
Sausage shaped mass in right upper quadrant
Management of SBO?
Fluid resuscitation
Insert NG tube to decompress bowel (removal of contents by suction)
Analgesia + anti-emetic
Consider surgery
Antibiotics
When should you immediately operate in SBO?
Signs of strangulation
Perforation + peritonitis
What can you to surgically to treat SBO?
Remove the cause of obstruction
Bypass the segment
Resection
Exteriorisation (stoma bag)
What are the causes of large bowel obstruction?
Malignancy
Volvulus
Strictures (narrowing)
Congenital fault
Describe the progression of obstruction to peritonitis.
Obstruction
Proximal dilatation
Increased colonic pressure = decreased mesenteric blood flow
Mucosal oedema caused by fluids + electrolytes in the lumen
Arterial blood supply is compromised
Mucosa becomes ischaemia
Ulceration
Necrosis
Perforation
Bacteria escape to peritoneum
What happens if the ileocaecal valve is incompetent?
It won’t open and you’ll get faeculent vomiting
Why would a volvulus occur?
Sometimes the bowel just twists on itself spontaneously!
What is a closed loop obstruction?
A 360 degree twist/volvulus
Why do loop obstructions perforate?
Increase in pressure in section Impaired blood flow Ischaemia Necrosis Perforation
In colorectal tumours, where does perforation occur?
At the site, rather than proximally
Because perforation is caused by local invasion of the tumour and inflammation of area
Volvuli present suddenly. True or false?
True
What would you find on examination of someone with LBO?
Distension
Resonance
Palpable mass
Digital rectal examination:
- empty rectum
- hard stools
- blood
Investigation of LBO?
Bloods: FBC, U+E, lactate
X-ray + CT
Contrast enema
Endoscopy: look at mucosa, risk of perforation, can be therapeutic
What is the significance of lactate in intestinal obstruction?
High levels indicate some types of bowel obstruction
What signs are seen on AXR in large bowel obstruction?
Where would obstruction be and what would it be if you saw these signs?
Coffee bean
Bird of prey
Sigmoid volvulus
How would you manage a non-perforated LBO?
Drip and suck: IV fluids, NG tube
Use a rigid or flexible sigmoidoscopy to straighten out
How would you manage a perforated LBO?
Emergency surgery
Resect
Wash out peritoneum + bowel
What is non-mechanical obstruction?
Failure of peristalsis
Adynamic bowel
No mechanical cause
What are the clinical features of non-mechanical obstruction?
Pain free
Distention
Vomiting not projectile
Absent or tinkling bowel sounds
How do you treat non-mechanical obstruction?
Nil by mouth IV fluids Nasogastric aspiration Treat the underlying cause Supportive nutrition
