Intestinal Obstruction Flashcards
What is intestinal obstruction?
Restriction in the normla passage of intestinal contents along the intestines
What are the 2 main types of intestinal obstruction?
=> Mechanical obstruction
Luminal contents cannot pass through as the lumen is physically blocked, either completely or partially
=> Paralytic obstruction (ileus)
Luminal contents cannot pass through because of cessation of normal gut peristalsis. Also referred to as functional obstruction
What are the different ways mechanical obstruction is characterised?
=> Speed of onset
- Acute
- Chronic
- Acute on chronic
=> Anatomical site
- Small bowel obstruction
- Large bowel obstruction
=> Simple or strangulating
- Obstruction without compromise to the blood supply is known as simple obstruction
- Obstruction where the blood supply to the area is compromised is known as strangulating
- Strangulating obstructions are usually complete but may be partial
=> Open loop or closed loop
- Open loop obstruction occurs when intestinal blow is blocked but proximal decompression is possible through vomiting
- Closed loop obstruction occurs when inflow and outflow are both block, leading to obstruction without the possibility of decompression
- Closed loop obstruction see bowel dilatation
- Increased pressure on the blood supply surrounding the wall
- Blood supply is compromised, leading to strangulation
What are some examples of a closed loop obstruction?
- Torsion of a loop of small intestine around an adhesion
- Incarceration of a bowel in a hernia
- Volvulus
- Large bowel obstruction with a competent ileo-caecal valve
What are the common causes of small bowel obstruction?
=> Adhesions
- Most common cause in the UK
- Adhesion is a band of fibrous tissue binding together two anatomical structures which are usually separate
- They kink, twist or pull the intestine out of place, resulting in the obstruction
=> Abdominal hernias
- Second most common cause in the UK
- If segment of bowel protrudes into the sac and becomes trapped, it can lead to closed loop strangulating bowel obstruction
=> Intussusception
- Occurs when a segment of the small bowel prolapses into the immediately adjoining bowel
- Commonest form is ileocolic
- Blood supple is cut off by the direct pressure of the outer layer, resulting in strangulation
=> Volvulus
- It is the abnormal twisting of the bowel
- Most commonly occurs in the sigmoid colon
=> Crohn’s disease
What are the precipitating factors of Volvulus?
- Abnormally mobile loop
- Abnormally loaded loop
- A loop fixed at its apex by adhesions but can rotate around it
- Loop with a narrow mesenteric attachment
What is the management of Volvulus?
- Treated by passing a long soft rectal tube through a sigmoidoscope and advancing it into the sigmoid colon
- If this fails, the volvulus is untwisted at laparotomy and the bowel is decompressed via a rectal tube threaded up from the anus
- If infarction or gangrene has occurs, the affected area is resected and the 2 open ends are bought together
What are the common causes of large bowel obstruction?
- Colorectal cancer (tumours)
- Diverticular strictures
- Sigmoid volvulus
Where is Colorectal cancer most likely to cause an obstruction?
Left sided of colon as luminal contents is more solid when it gets to this point
Where is Crohn’s Disease more likely to cause an obstruction?
- Small bowel, most commonly affecting the terminal ileum
What are the most common causes of bowel obstruction in neonates?
- Congenital aterisia and stenosis
- Volvulus
- Hirschsuprung’s disease
- Meconium ileus (strong association with cystic fibrosis)
What are the most common causes of bowel obstruction in infants?
- Intussusception
- Hirschsuprung’s disease
- Strangulated hernia
- Meckel’s diverticulum
What is the pathophysiology of bowel obstruction?
- In simple bowel obstruction, the distal end of the bowel exhibits normal peristalsis, so any residual content is passed out
- The proximal end of the bowel exhibits increased peristalsis to overcome the obstruction, causing colicky pain
- The proximal end gradually dilates due to increased pressure - abdominal distention
- The ejection of the accumulated intestinal secretions and contents - vomiting
- Abdominal distension leads to a compromise of blood supply, causing strangulation
- Untreated strangulation progresses to irreversible ischaemia
- Ischaemia eventually causes bowel infarction and perforation as the wall loses its structural integrity
- Intestinal contents released into the peritoneum incites peritonitis
- Peritonitis can lead to death
What are the clinical features of bowel obstruction?
- Dehydration
- Hypotension, tachycardia
- Empty rectum on PR exam
- Vomiting
- Colicky abdominal pain (comes and goes)
- Abdominal distension
- Absolute constipation
What are the specific clinical features of a strangulating bowel obstruction?
- Tachycardia
- Fever
- Colicky pain becomes continuos
- Tenderness, guarding and rebound tenderness
- Absent bowel sounds
