Gen Surg: 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/below the site of obstruction in someone with a simple obstruction?
Peristalsis + distention (due to gas, GI content and fluid build up)
Below the obstruction - collapsed, immobile, pale
@ obstruction = perforation can occur
What are causes of death in simple bowel obstruction?
- Fluid & electrolyte imbalance - from third space loss and dehydration
- Peritonitis - proliferation of bacteria proximal to obstruction leading to bacterial translocation
Causes of simple bowel obstruction
Inside the lumen - gallstones, impaced faeces
In the wall - strictures, tumours, CD, diverticulitis
Outside the wall - ADHESIONS, hernias
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 - venous supply lower pressure than arterial supply, 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
When would you suspect strangulation?
Internal strangulation
- Severe pain thats never completely absent between attacks
- Shock
- Tenderness and rigidity with rebound tenderness
- GI suction fails to releive pain
Strangulated external hernia
- Hernia swelling that is tense, tender, irreducible and no expansable impulse on cough (hernias are painless unless complicated)
What are causes of death in strangulation?
- Peritonitis due to perforation - bacterial translocation and impairment of barrier function of intestinal mucosa
- Hypovolaemic shock - third space loss
- Sepsis
What is a closed loop obstruction?
When some part of the gut is closed at both ends - THIS IS DANGEROUS AND IS A SURGICAL EMERGENCY eg competant ileocaecal valve
What is typically the cause of a closed loop obstruction
Sigmoid volvus
At what diameter would you be concerned of caecal perforation?
10cm
What are the complications of bowel obstruction?
- SEPSIS - venous compression, bowel cells die, decreased peristalsis, bacteria enter circulation
- SHOCK (hypotension) - venous compression, fluid secretion, decreased H2O, decreased electrolytes, hypotension
- SHOCK (hypovolaemia) - bowel distension, decreased vomitting response, decreased H2O, decreased fluids
Bowel ischaemia from venous compression
Perforation due to increased air
Sepsis due to perofation/dissemination
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 - handling of bowel, contact of internal organs with foreign objects, cuts involving internal organs.
Can also result from appendix rupture, infection, radiation, abdo infections
Indications for surgery in adhesive intestinal obstruction
Suspected strangulation
Failure of conservative management
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 is paralytic ileus?
Cessation of peristalsis due to failure of neuromuscular mechanism of the intestine causing accumulation of fluid and gas in the intestine
What are causes of paralytic ileus?
- Post surgery especially for peritoneal sepsis
- Peritonitis
- Drugs - TCAs, anticholinergic, opiod mets
- Spinal injury
- Electrolyte imbalance - hypokalaemia, hyponatraemia, uraemia (esp magnesium and potassium_
- 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
Presentation paralytic ileus
Progressive abdo distension, vominting, absolute constipation, failure to pass flatus.
Mild abdo discomfort.
Management paralytic ileus
TREAT UNDERLYING CAUSE
Gi suction
Restore fluid and electrolyte balance, monitor for AKI
Encourage mobilisation
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
- Peristaltic pain
- Colicky initially, constant suggests strangulation/impending perforation
- Vomiting
-
Abdominal distention
- Jejunal obstruction - minimal
- Ileal obstruction - central
- 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
Focal tenderness, guarding, rebound tenderness when ischaemic
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
When is distention more prominent in SBO?
In distal obstruction
How does the timing of vomiting roughly indicate where a SBO might be?
The more proximal the obstruction, the earlier vomiting will occur:
- Jejunal Obstruction - Vomiting occurs with the first and each attack of pain
- Ileal Obstruction - Vomiting is delayed for few hours; then it occurs with each attack of pain
If vomiting occured early on in someone with suspected SBO, what might this suggest about where the problem is in the small intestine?
High - e.g. jejunal obstruction
If feculent vomiting occured late after someone presented with abdominal pain and marked abdominal distention, where might you suspect the obstruction is occuring?
Low - e.g. ileum
What might you see on AXR in someone with suspected small bowel obstruction?
- Dilated loops proximal to the obstruction - predominantly central dilated loops
- Valvulae conniventes are visible
- Air-fluid levels if the study is erect
-
Gasless bowel
- Partial: gas throughout the abdomen and into the rectum.
- Complete: no distal gas, and staggered air-fluid levels.
What might you see on CXR in someone with an intestinal obstruction?
Free air under the diaphragm - due to perforation
What is a gastrografin follow through study?
Involves administration of contrast material into the stomach. The subsequent assessment of degree of passage of this material, using serial x-rays, can provide information regarding the presence and location of the obstruction within the GI tract:
- Partial SBO - medium passes into rectum.
- Complete SBO - medium does not pass into rectum and is held up at site of obstruction.
Not done in acute presentations.
What are the differences in radiological appearence of the jejunum, ileum and colon?
What are the different types of volvulus that can occur?
- Volvulus neonatorum
- Volvulus of small intestine
- Caecal volvulus
- Sigmoid volvulus
How would you manage a sigmoid volvulus?
-
General management
- + decompression with sigmoidoscopy
-
Surgery (if repeated failed attempts at decompression, necrotic bowel noted, suspected/proven peritonitis)
- Emergency: Untwisting by flexible sigmoidoscopy -> Sigmoid resection in fit patients
-
Failed sigmoidoscopy -> open surgery
- Primary anstomoses OR hartmans
If someone was found to have a large bowel obstruction on AXR, what investigation would you consider doing next?
Gastrografin enema - determine whether carcinoma, ogilives syndrome or diverticular disease
How would you manage Ogilvie syndrome?
- Neostigmine - inhibits cholinesterase
- Colonoscopic decompression
