How does a Bowel Obstruction Occurs

Anything that causes blockage to the intestines, causing dysfunction and dysmotility to the intestines is known as an intestinal obstruction. Having said, the cause of obstruction is many and variable. It can be divided into mechanical or non-mechanical causes, simple or strangulating, complete or partial, and it can occur in any parts of the intestines. The normal human intestine length is about 7.5 meters long, of which 6 meters is the length of the small intestines and the remaining 1.5 meter is the length of the colon, i.e. the large intestines. Hence, the location of the obstruction is an important finding that will affect the final diagnosis and hence the management.

Types of bowel obstruction


  • Mechanical obstruction occurs when the blockage physically interrupts the movement of the intestinal content. The blockade can arise from

    • within the passage of the intestine – commonly the impacted hard stools
    • within the wall of the intestine itself – such as tumors, inflammation in the intestine, or organic causes that results in narrowing of the intestinal diameter
    • outside the wall of intestine – for instance, if there has been a previous abdominal surgery done, the scarred tissue can cause adhesion of the intestine resulting in blockage or immobility. Tumors that arise from outside the intestinal wall can cause compression of the bowel resulting in obstruction. Not forgetting hernia, which is another common disease that can manifest as bowel obstruction.


  • Non-mechanical obstruction arises from certain intestinal condition that involves the muscles of the intestinal wall. These muscles contribute to the propelling motion of the intestines known as “peristalsis”. This action is important in the digestive system as it aids in absorption of nutrients from the food that we eat into our body and eventually moves the intestinal content in the form of faeces to the end of the digestive tract, in which we pass out as stools. Thus, when this action of the intestinal muscle is disrupted bowel obstruction results.

So much for the physics of bowel obstruction. Now we shall talk about the simple and strangulating type of bowel obstruction. Remember, these subtypes of condition can overlap, meaning a mechanical bowel obstruction can occur as simple complete mechanical or strangulating complete mechanical bowel obstruction and vice versa with the non-mechanical and partial type.

  • Simple Bowel ObstructionIn simple bowel obstruction, the blood supply to the intestine is not compromised. Hence the integrity of the intestine is still present.The analogy will be like a water tube being blocked by a pebble. Whatever incoming content will accumulate before the blockade and cause distention due to the trapping of content. The portion after the blockade will then collapse as there is no continuous flow of content. 
  • Strangulating Bowel Obstruction However, if the intestine is strangulating – imagine what happens if you have a tight rubber band placed around your wrist – blood flow is compromised (ischemia). This can progress to lack of oxygen being delivered to the tissue (infarction) and eventually cause death to the tissue (necrosis). Strangulating bowel obstruction can progress into the latter conditions within as fast as six hours if it is not medically intervened.This type of ischemic bowel condition usually occurs in the small intestines because of its smaller diameter and the extensive blood supply that is shared amongst the different parts of the crowded small intestine; unlike the large intestines where blood is efficiently supplied to each specific region of the large intestines. Having said, in hernias that occur in the large intestine, such as inguinal or femoral hernia, strangulating bowel obstruction must be identified early as it is a surgical emergency.Generally, strangulating bowel obstruction is commonly associated with conditions such as –
    • hernia – in both small and large intestines
    • volvulus – a condition that results due to twisting of the intestine which usually occur in the elderly
    • intussusceptions – telescoping of a portion of the bowel into the adjacent bowel segment – commonly a pediatric condition. The word “telescoping” is referred as a simile to the sliding action of a collapsible telescope.

Signs and Symptom

The signs and symptoms manifest by patients correlate with the clinical diagnosis of the location of bowel obstruction.

If the blockage occurs in the small intestines

  • onset of symptoms is acute, within minutes to hours
  • nausea
  • vomiting consisting of yellow-greenish bile aside from gastric content
  • pain
  • abdominal cramps will be localized around or above the umbilicus


If the obstruction is in the large intestines –

  • onset of symptoms is gradual, within days to weeks
  • sense of fullness indicating abdominal distension
  • gross abdominal distension
  • increasing constipation
  • unable to pass flatus
  • vomiting can occur but is rare and a very late sign of large bowel obstruction.

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