BOWEL OBSTRUCTION Flashcards
What is bowel obstruction?
complete or partial disruption of the normal flow of gastrointestinal content.
What is a complete bowel obstruction?
no fluid or gas is able to pass beyond the site of obstruction.
What is incomplete bowel obstruction?
some fluid or gas is able to pass beyond the site of obstruction.
What is mechanical bowel obstruction?
physical blockage to the flow of gastrointestinal content.
What is non-mechanical bowel obstruction?
obstruction to flow secondary dilatation of the bowel in the abscence of mechanical blockage through failure of normal peristalsis
Aka ileus
What is a closed loop bowel obstruction?
the bowel is obstructed at two points, this prevents proximal or distal decompression of contents.
High-risk of rapid necrosis and perforation - surgical emergency!
What proportion of acute abdomen cases are found to have a bowel obstruction?
Around 15%
Outline the pathology after a bowel obstruction occurs?
Bowel segment has become occluded -> gross dilatation of the proximal limb of the bowel -> increased peristalsis -> secretion of large volumes of electrolyte-rich fluid into the bowel (third spacing)
What is a pseudo-obstruction in the bowel?
When the bowel is not mechanically blocked but is adynamic and not working properly
What are the most common causes of small bowel obstruction?
Post-operative adhesions or hernias
Others - IBD, malignancy, radiation enteritis, intussusception, gallstone ileus
What are the most common causes of large bowel obstruction?
Malignancy, diverticular disease or volvulus
What are post-operative adhesions?
strands of fibrous tissue that form following surgery due to the bowel being handled. It can lead to the abnormal adhesion between intra-abdominal tissue ans can trap the bowel which may leas to obstructions.
How do hernias cause small bowel obstructions?
Loops of bowel can become trapped within the hernial sac leading to obstruction and potentially strangulation and infarction if not managed urgently.
What proportion of pt with mechanical large bowel obstruction occur secondary to colorectal malignancy?
60%
20% diverticular stricture and 5% volvulus
What is paralytic ileus?
the general slow-down of the intestines and affects the entire intestinal tract (small and large bowel).
What causes paralytic ileus?
Poorly understood but commonly seen post-operatively
Other triggers - abnormal electrolytes and systemic upset
What is acute colonic pseudo-obstruction?
acute dilatation of the colon in the absence of an anatomic lesion that obstructs the flow of intestinal contents.
Aka Ogilvies syndrome
What causes acute colonic pseudo-obstruction?
Its aetiology is poorly understood and likely multifactorial. A combination of systemic illness, medications and biochemical abnormalities are implicated.
The condition is also often seen in the post-partum setting, particularly following caesarian section.
What are the symptoms+signs of bowel obstruction?
Abdominal pain (colicky/crampy)
Nausea
Absolute constipation (early in distal obstruction and late in proximal obstruction)
Vomiting (early on if proximal but late if distal obstruction)
Anorexia
Small volume diarrhoea
Obstipation
Systemic upset if significant dehydration or complication
Abdominal tenderness/peritoneum
Rebound
Abdominal distension
Abdominal mass - hernia?
Dehydration
Scars
Tympanic sound on percussion
Tinkling bowel sounds on auscultation
What does it suggest if a pt with bowel obstruction has features of guarding or rebound tenderness?w
Ischaemia is developing
What investigations should be done for a bowel obstruction?
Obs
ECG
Fluid balance
PR exam
Pregnancy test
VBG/ABG, FBC, U&E, bone profile, Magnesium, LFTs, amylase, CRP, group and saves
CT abdo/pelvis with contrast is imaging of choice but sometimes plain AXR is done
What does high lactate in bowel obstruction suggest?
Small bowel ischaemia may be present
What is seen on plain abdominal X-ray for small bowel obstruction?
Dilated bowel >3cm
Valvulae conniventes visible (lines completely crossing the bowel) creating a coiled spring appearance
What is seen on plain abdominal X-ray for large bowel obstruction?
Dilated bowel >6cm or >9cm if caecum
Haustral lines visible (indents that go Halfway are Haustra!!)
May see volvulus
What is Rigler’s sign?
Double-wall sign - gas outlining both sides of the bowel wall
Sign of pneumoperitoneum
What does a sigmoid volvulus look like on abdominal X-ray?
typical ‘coffee bean’ sign is described - sigmoid colon twisted at the root of its mesentery in LIF = dilation
Arises from left lower quadrant, haustra cannot be identified.
Multiple air-fluid levels may be seen.
Classical appearances often not present and a simple x-ray may not be diagnostic.
What does a caecal volvulus look like on abdominal X-ray?
arises from the right lower quadrant
haustral pattern tends to be maintained
One air-fluid level seen
Classical appearances often not present and a simple x-ray may not be diagnostic.
What is NELA?
National Emergency Laparotomy Audit
What is the NELA risk calculator?
can be used to give an estimate of a patient’s 30-day mortality after emergency abdominal surgery
When do we use conservative management of bowel obstruction?
In absence of signs of ischaemia or perforation
80% success rate
Often referred to as a ‘drip and suck’ management
Whats the conservative management of bowel obstruction?
Pt must be nil-by-mouth and insert an NG tube to decompress the bowel - “suck”
Start IV fluids and correct any electrolyte disturbances - “drip”
Urinary catheter and fluid balance
Analgesia
Antiemetics
Cardiac monitoring in pt with multiple co-morbidities due to fluctuations in intravascular status
What can be done if cases of bowel obstruction do not resolve initially with conservative management?
A water soluble contrast study and AXR 6 hours after to check for ongoing obstruction vs resolution
As well as checking to see for resolution, what is an added benefit of doing a water soluble contrast study in bowel obstruction cases?
The gastrograffin (contrast medium) used may have therapeutic properties in resolving obstruction due to its osmotic effect on bowel wall oedema
When is surgical intervention indicated in bowel obstructions?
Suspicion of intestinal ischaemia or closed loop bowel obstruction
A cause that requires surgical correction (such as a strangulated hernia or obstructing tumour)
If patients fail to improve with conservative measures (typically after ≥48 hours)
What surgery can be done for bowel obstructions caused by physical obstructions e.g. tumour?
Defunctioning stoma and resection with primary anastomosis via laparotomy
What are the complications of bowel obstructions?
Bowel ischaemia
Bowel perforation leading to faecal peritonitis - HIGH MORTALITY
AKI if severely fluid depleted
End-organ injury
What is a volvulus?
Intestinal twisting/looping
What are the types of volvulus and what’s most common?
Sigmoid volvulus - most common
Caecal volvulus
Midgut volvulus
Who do sigmoid volvulus often occur in?
Older pt
Those with chronic constipation
Chagas’ disease
Neurological conditions e.g. DMD or parkinsons
Psychiatric conditions
Who do cecal volvulus occur in?
All ages
Those with adhesions or are pregnant
Who does might volvulus often occur in? Why?
Infants/young children
It’s caused by anomalous intestinal development
What are the complications of a volvulus?
Mesenteric artery compression causing intestinal wall ischaemia and infarction
Intestinal wall perforation or infection
What are the signs and symptoms of a volvulus?
Abdominal tenderness or pain
Abdo distension
Bilious vomiting
Constipation
Fever
Abnormal bowel sounds that are often decreased
Tympanic on percussion
Hematochezia - may indicate bowel ischaemia/necrosis
How are volvulus diagnosed?
X-Ray
Barium enema
CT scan
What is small bowel ischaemic?
Reduced blood flow to the small bowel that will subsequently cause infarction
What is intussuspection?
the movement or ‘telescoping’ of one part of the bowel into another. The proximal bowel segment is referred to as the intussuceptum whilst the distal segment as intussucipiens
When is the peak incidence of intussusception?
Between 5-7 months of age
Rare to occur after 2
Boys are twice as likely than girls to be affected
Where does intussusception tend to occur in the GIT?
Up to 90% of cases are of the ileo-colic type whereby the distal ileum passes into the caecum through the ileocaecal valve
What are the risk factors for intussusception?
Meckels diverticulum’
Polyps
Henoch-schonlein purpura
Lymphoma and other tumours
Post-operative
Viruses e.g. rotavirus
What proportion of intussusception cases is an underlying pathological cause identified?
25%
More likely if child is older or there is a high recurrence rate
How does intussusception present?
Sudden onset of inconsolable crying episodes
Pallor
Child may have knees drawn up to chest in attempt to alleviate pain
Normal self i between episodes
Recurrent consistency in stool due to pressence of mucus and blood
Vomiting and abdominal pain if intestinal obstruction
Distension
Palpable sausage-shaped abdominal mass often in RUQ
Signs of peritoneum
Bowel sounds present
How do we investigate intussusception?
Abdominal ultrasound
Can use AXR but low sensitivity
Contrast enema (not if peritonitis or perforation)
How is interssusception managed?
Fluid resuscitation
NG tube to decompress obstructed bowel
No operative reduction - using air or contrast enema
Surgical reduction
What are the complications of interssusception?
Obstruction - surgical emergency
Perforation
Dehydration and shock
Whats the prognosis of interssusception?
Mortality rates are <1%