Overview
Small bowel obstruction is a frequent medical emergency caused by a blockage in the digestive tract. Many different diseases can lead to small bowel obstruction, but the most common cause in developed countries is adhesions or scar tissue inside the abdomen. The obstruction in the small bowel can be partial or complete, and sometimes, it may cut off the blood supply, a condition referred to as “strangulated”.
Causes
When the small bowel becomes blocked, it’s often due to adhesions or scar tissue that form after surgery. The next most common cause of this type of blockage is incarcerated hernias. Different reasons for this can include cancer, inflammatory bowel disease (specifically Crohn’s disease), blocked stool, foreign objects, or a condition known as volvulus where the bowel twists on itself.
For children, this can happen as a result of congenital atresia (a condition where a part of the bowel doesn’t form properly), pyloric stenosis (a narrowing of the stomach outlet), other birth defects, or intussusception (a condition where one part of the bowel slides into another).
Risk Factors and Frequency
Every year in the United States, more than 300,000 surgical procedures called laparotomies are performed to treat a condition called small bowel obstruction. The small bowel is responsible for about 80% of such obstructions. Both males and females have a similar chance of developing this condition. However, the likelihood increases with age and with the number of previous procedures performed within the abdomen.
Signs and Symptoms
Medical history plays an important role when analyzing a patient’s situation. In some cases, a history of abdominal surgeries, bowel inflammation, cancer, or hernias may be relevant. Typical early signs of intestinal obstruction encompass abdominal pain, bloating, nausea, and vomiting. The pain can be steadily increasing or it can come in waves. It might come along with either constipation or diarrhea. Tuning into the sounds of your belly can also be a telling sign; voices coming from the gut can be subdued and sound high pitched.
Upon physical examination, a doctor may detect abdominal tenderness and bloating. The tenderness might be generalized or present only in a certain area. Peritonitis, which is a serious infection of the abdomen’s lining, may have markers such as rebound tenderness, muscle guarding, and a hard abdomen, especially in more advanced stages. Checking for hernias, scars from surgeries, lumps, and hard fecal matter blocking the rectum (rectal impaction) can often reveal the underlying cause of the symptoms. Don’t ignore signs like dehydration and sepsis either – they are severe conditions that can accompany an intestinal obstruction.
- Abdominal pain – steady or intermittent
- Bloating
- Nausea
- Vomiting
- Change in bowel habits – constipation or diarrhea
- Subdued and high-pitched gut sounds
- Abdominal tenderness
- Signs of infection in your abdomen
- Signs of dehydration
- Symptoms of sepsis
Testing
To diagnose a small bowel obstruction, doctors usually begin with a physical examination, but they often need more in-depth tests for assessing the need for and planning surgery. In the past, a small bowel obstruction diagnosis was purely based on a physical examination, but today, the accuracy of diagnosis has significantly improved with the use of computerized tomography (CT).
Doctors might also use X-rays as extra imaging techniques, but an ultrasound is usually more accurate. Plus, ultrasound does not involve exposure to radiation and allows for quick and repeated examinations. X-rays, while sometimes used as an initial screening test, are not as reliable as they only have a 50% to 80% detection rate. The X-ray might show air-fluid levels and free air inside the abdomen, but it’s not reliable for ruling out a small bowel obstruction.
The best method for imaging is a CT scan of the abdomen. If the patient’s kidneys are healthy and no other issues would make it risky, doctors usually use intravenous (IV) contrast to clear up the images. If the person has kidney issues, doctors might order a non-contrast study. In every case, deciding which type of CT scan to order should involve consultation with a radiology specialist. Drinking a contrast liquid before the scan is generally not necessary for evaluating a small bowel obstruction as it can delay diagnosis and lead to complications. Magnetic resonance imaging (MRI) might be a better choice for young patients who have already had multiple CT scans.
Doctors can also carry out a point-of-care ultrasound by following these steps:
1. Lay the patient flat, then choose the transducer that provides the needed depth for the particular patient. For children, this is typically a linear high frequency transducer of 5 MHz to 10 MHz, while for adults, a curvilinear transducer of 3 MHz to 5 MHz is usually used.
2. Start from the right lower part of the abdomen, work in a crosswise direction, and gently press down every 3 cm across all four areas of the abdomen, finishing in the left lower part.
3. Next, turn the transducer lengthways or lengthwise and press down in all abdomin areas, ending in the right lower quadrant.
The ultrasound can suggest a small bowel obstruction or ileus if it shows a small bowel that is wider than normal (more than 3 cm). It can also point to an obstruction or some other inflammatory bowel issue if it reveals a swollen bowel wall thicker than 3 mm. A bowel that can’t be compressed and free fluid implies an obstruction. Specific signs of an obstruction can come from the peristalsis (the wave-like motion that moves food through the intestines) moving both forwards and backwards, and from what’s called a transition point, where the bowel is shown as wider, thicker and unable to be compressed next to a small, decompressed section of the bowel.
While an ultrasound can provide helpful diagnostic information, it shouldn’t replace a CT scan or delay consultation with the surgery team. It’s particularly useful where it can speed up a diagnosis and help to rule out other possible causes.
Additionally, doctors should order routine lab tests to check for bowel tissue death (ischemia), inflammation, how dehydrated the patient is, and to rule out other possible conditions. These tests would typically include a complete blood count, lactic acid levels, a complete metabolic profile, urine tests, and clotting tests.
Treatment
If a patient is suffering from a small bowel obstruction, it’s important to consult a surgeon quickly, as surgery is often needed to treat this condition. The first steps in treatment usually involve rehydrating the patient, managing their pain, providing antibiotics, and often using a nasogastric tube (a tube from the nose to the stomach) to relieve pressure in the stomach. The chosen antibiotics should be effective against the types of bacteria commonly found in the gut, which includes both gram-negative and anaerobic bacteria.
For patients with ileus (a lack of movement in the intestines that can cause a blockage) or a partial small bowel obstruction, less invasive treatment options may be possible. This could include using a nasogastric tube to ease the obstruction. However, these patients should still consult a surgeon, even though they may not need surgical intervention.
Related Conditions
The symptoms of appendicitis can be similar to those of other conditions, making it difficult to diagnose at times. Here are some of the conditions which can be mistaken for appendicitis:
- Constipation
- Viral or bacterial stomach infection (known as gastroenteritis)
- Paralytic ileus (a type of bowel obstruction)
- Mesenteric ischemia (reduced blood supply to the intestines)
- Acute pancreatitis (inflammation of the pancreas)
- Intussusception (a condition where the intestine folds into itself)
Precise diagnosis is crucial to make sure the right treatment is provided. That’s why doctors have to carefully consider these possibilities when dealing with a suspected case of appendicitis.
Possible Complications
- Bowel tissue death and rupture
- Surgical wound separation
- Internal abdominal pus pockets
- Aspiration
- Short bowel syndrome
Pearls and Other Issues
If, during an ultrasound, the small bowel appears enlarged and can’t be compressed, it typically indicates a small bowel obstruction. A width of more than three centimeters is generally considered as enlarged. If the wall of the small bowel is more than 3 mm thick, it is deemed thick. Specific signs on the ultrasound that could indicate this condition include back and forth bowel movements and identifying a point where the obstruction starts. A CT scan, however, is the most accurate way to diagnose and describe a small bowel obstruction.
