Intestinal Obstruction

Gastroenterology (12%) Core Clinical Conditions

1B The Physician Associate is able to identify the condition as a possible diagnosis: may not have the knowledge/resources to confirm the diagnosis or to manage the condition safely, but can take measures to avoid immediate deterioration and refer appropriately.

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Definition Aetiology Pathophysiology Risk factor Sign and Symptoms Investigations Management

Intestinal obstruction refers to a medical condition in which there is a partial or complete blockage within the intestines, hindering the normal flow of digested food, fluids, and gases. This potentially serious condition can occur at any age and may require prompt medical intervention to prevent complications.

The two main types of intestinal obstruction are:

1. Small Bowel Obstruction: This type occurs when there is a blockage in the small intestine, impeding the normal transit of digested food. Causes can include adhesions (scar tissue), hernias, tumours, impacted faeces, or even gallstones that have migrated into the intestines.

2. Large Bowel Obstruction: This type occurs when the blockage affects the large intestine, also known as the colon. Common causes include tumours, diverticulitis, impacted stool, or strictures due to inflammatory bowel disease or previous surgeries.

Mechanical Obstruction

The most common cause of intestinal obstruction is mechanical obstruction, which can occur at various levels within the gastrointestinal tract. It can be caused by factors such as adhesions, hernias, tumours, strictures, or impacted faeces.

When a mechanical obstruction occurs, the normal passage of intestinal contents is disrupted. This leads to an accumulation of intestinal contents proximal to the site of obstruction, resulting in increased intraluminal pressure. The increased pressure can cause distention of the affected bowel segment, leading to compromised blood flow and impaired intestinal function.

Functional Obstruction

Functional obstruction, also known as paralytic ileus, is another type of intestinal obstruction that occurs due to the disruption of normal intestinal motility. Unlike mechanical obstruction, functional obstruction does not involve a physical blockage but rather a disturbance in the coordinated movement of the intestines.

Functional obstruction can be caused by a variety of factors, including medications, electrolyte imbalances, postoperative complications, or underlying medical conditions such as diabetes or inflammatory bowel disease. These factors disrupt the normal functioning of the intestinal smooth muscles, resulting in slowed or absent peristalsis.

Pathophysiological Changes

Regardless of the type of obstruction, several pathophysiological changes occur in intestinal obstruction:

1. Distention and Increased Pressure: As intestinal contents accumulate proximal to the site of obstruction, the affected bowel segment becomes distended. The increased luminal pressure contributes to further impairment of blood flow, leading to tissue ischemia and edema.

2. Fluid and Electrolyte Imbalance: The prolonged stasis of intestinal contents can cause significant fluid and electrolyte imbalances. There is a loss of fluid and electrolytes into the lumen of the obstructed bowel, leading to dehydration, electrolyte abnormalities, and metabolic acidosis.

3. Impaired Blood Flow: The distention and increased pressure within the obstructed bowel can compromise blood flow to the affected area. Reduced blood flow can lead to ischemia, tissue necrosis, and potential perforation. Additionally, the compromised blood flow can also result in bacterial overgrowth and translocation, leading to infection.

4. Intestinal Dysfunction: The obstruction disrupts the normal functioning of the intestinal wall, impairing the absorption and secretion of fluids and electrolytes. This can lead to malabsorption, further exacerbating the fluid and electrolyte imbalances, and resulting in diarrhoea or constipation.

1. Previous abdominal surgeries: Individuals who have undergone previous abdominal surgeries, such as bowel resections, are at an increased risk of developing intestinal obstruction. Adhesions, which are bands of scar tissue that form after surgery, can cause obstructions by sticking together and trapping the intestines.

2. Hernias: People with hernias, particularly those with incarcerated or strangulated hernias, have a higher risk of intestinal obstruction. A hernia occurs when an organ or fatty tissue pushes through a weak spot in the abdominal wall, potentially leading to blockages if the hernia becomes trapped or twisted.

3. Tumours: Both benign and malignant tumours in the gastrointestinal tract can cause intestinal obstruction. Cancerous growths can obstruct the intestines by narrowing the passage and hindering the normal flow of contents.

4. Inflammatory bowel disease (IBD): Conditions like Crohn's disease and ulcerative colitis, which are categorised as inflammatory bowel diseases, increase the risk of developing intestinal obstruction. Chronic inflammation in the intestines can lead to the formation of strictures or scar tissue, narrowing the intestinal passage and causing blockages.

5. Intestinal adhesions: In addition to previous surgeries, conditions such as pelvic inflammatory disease, endometriosis, and peritonitis can cause intestinal adhesions. Adhesions are bands of fibrous tissue that form between abdominal organs, disrupting the normal movement of the intestines and leading to obstruction.

6. Intussusception: Intussusception occurs when one segment of the intestine telescopes into another segment, causing bowel obstruction. While it predominantly affects children, it can also occur in adults due to certain medical conditions such as polyps or tumours.

7. Gastrointestinal strictures: Strictures are narrowings of the intestines that can be caused by various factors, including previous surgeries, chronic inflammation (such as in Crohn's disease), or scarring from ulcers. These strictures can gradually progress and eventually lead to bowel obstruction.

8. Foreign bodies: Swallowing objects that are difficult to digest, such as bones, sharp objects, or non-food items, can become lodged in the intestines, resulting in obstruction.

9. Volvulus: Volvulus refers to the twisting of the intestines, which can impair the blood supply and lead to intestinal obstruction. Certain conditions like malrotation (abnormal rotation of the intestines during foetal development) or abdominal adhesions can increase the risk of volvulus.

10. Strangulated hernias: When a hernia becomes strangulated, it means that its blood supply has been cut off, often leading to intestinal obstruction. This can occur if the hernia becomes trapped or twisted, causing pressure on the intestines.

• Abdominal Pain: Often characterised as cramp-like, sharp, or colicky, abdominal pain is a hallmark symptom of intestinal obstruction. The intensity of the pain can fluctuate, and it may worsen as the blockage persists.

• Bloated abdomen: As the blockage inhibits the natural movement of air and liquid through the intestines, the affected individual may experience abdominal distention, giving rise to a visibly swollen or bloated abdomen.

• Nausea and Vomiting: Intestinal obstruction can lead to a build-up of gastric contents, resulting in feelings of nausea and subsequent episodes of vomiting. Vomitus may appear bile-stained if the obstruction is closer to the stomach.

• Constipation or Diarrhoea: Depending on the location and severity of the obstruction, an individual may experience either a complete absence of bowel movements (constipation) or frequent liquid stools (diarrhoea).

• Inability to Pass Gas: The blockage can prevent the passage of gas through the rectum, leading to bloating and a distinct inability to release flatulence.

History taking and physical examinations:

Check for symptoms which include severe abdominal pain, bloating, vomiting, constipation, and the inability to pass gas. Also look for signs of dehydration, abdominal distension, and tenderness.

Laboratory Tests:

Blood tests, such as a full blood count (FBC) and renal profile, hba1c, CRP/ESR. These can provide information about electrolyte imbalances, dehydration, and signs of infection. An elevated white blood cell count may suggest the presence of infection which can accompany intestinal obstruction.

Imaging Studies:

1. X-ray: Plain abdominal X-rays can provide initial insights into the location and severity of the obstruction. Abnormal air-fluid levels, dilated loops of bowel, and the presence of gas in the rectum are suggestive findings on X-ray.

2. CT Scan: Computed tomography (CT) scans are highly effective in diagnosing and evaluating the extent of intestinal obstruction. This imaging technique can identify the precise location of the obstruction, its cause, and any complications that may have resulted from it.

3. Barium Swallow or Enema: Barium contrast studies involve swallowing or enema administration of a liquid containing barium. X-rays are then taken to visualise the barium's flow through the intestines. This assists in identifying the site and nature of the obstruction.

4. Ultrasound: Although less commonly used, ultrasound can be helpful, especially in diagnosing intestinal obstruction in infants. It can detect bowel distension, fluid buildup, or abnormal masses in the abdomen.

Endoscopy:

Endoscopy may be used to investigate intestinal obstruction. This technique involves inserting a flexible tube with a camera through the mouth or rectum to visualise the inside of the digestive tract. Endoscopy can help identify strictures, tumours, or other abnormalities that are causing the obstruction.

Pain Management

Intestinal obstruction often presents with severe abdominal pain. Adequate pain management is crucial to provide relief and ensure patient comfort. Non-steroidal anti-inflammatory drugs (NSAIDs) or opioids may be administered as appropriate, based on the severity of pain.

Surgical Intervention

Surgical intervention is often necessary for complete intestinal obstructions or when conservative measures fail. The type of surgical procedure depends on the underlying cause and location of the obstruction.

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