 Hello and welcome to emergency medicine video. In this segment we will discuss the presentation, diagnosis and treatment of small bowel obstruction. Small bowel obstruction happens when the normal flow in the bowel lumen is blocked. As a result, the bowel proximal to the obstruction then dilate. It causes three main problems. One, there is no passage distal through the lumen anymore, that leads to vomiting, and patient is now unable to tolerate oral intake. Second, the bowel wall now swells more and starts to ooze fluid into the peritoneum. In severe cases of edema, the edema compromises blood flow to the bowel. It now becomes ischemic, and that can lead to perforation. What causes small bowel obstruction? It can be something on the outside of the bowel, or something inside the bowel. On the outside, anything that causes scar tissues or adhesions in the peritoneum can cause bowel obstruction. It happens when the bowel is being caught up in the adhesions. Adhesions are caused by previous surgery. This is the main cause of small bowel obstruction. Less commonly, the small bowel can also be caught if there is a hernia. In the bowel itself, inside causes of small bowel obstruction include masses, narrowing or strictures, interception where one part of the bowel is telescoping into another part of the bowel. Also, inflammatory bowel disease such as Crohn's disease can also lead to obstruction. Bow obstruction can be complete where no content is passing through the lumen, or partial where there is still some passage of content through. Partial obstruction is further defined as high-grade or low-grade obstruction depending on how narrow the lumen that's left behind is. Now that we know a little bit about the risk factor for bowel obstruction, let's see how a patient would present. In terms of history, patients with small bowel obstruction typically present with abdominal pain. This pain is usually intermittent as the content is trying to go through the lumen. As you might remember, patients often have vomiting. Since the distal lumen is blocked, patients will find it difficult to pass gas. As a result, the patients often can describe that the abdomen is distended. Sometimes early on in the course of the obstruction, occasionally there is diarrhea. That usually stops. On statistical examination on the vital signs, since the patient can lose quite a bit of fluids by vomiting and decreased oral intake, they can be hypotensive and tachycardic. On examination, the abdomen is often distended. Bowel sounds are hyperactive early on and hypoactive late. If the bowel is perforated, there will be peritoneal signs. The patient can also look septic due to the perforation. Remember that adhesions are the main cause of bowel obstructions and therefore on physical examination, we will want to look for scars that suggest prior surgeries. We also want to look for hernias. In male patients, that includes the testicular exam. Let's move on to diagnosis. The diagnosis of small bowel obstruction starts with plain radiographs. We would order an upright chest x-ray and upright and supine abdominal x-ray. There are a few things we look for specifically in each film. On the upright chest x-ray, we will look for any air under the diaphragm that suggests a perforation. So in this schematic, these two curved structures are diaphragms and you want to look for free air underneath that on the upright chest x-ray. It might look something like this. Here is the diaphragm and here is the diaphragm somewhere over here, which you can't really see very well. And the free air, as you can see very well on top of the liver between the diaphragm, especially on the right side. It's hard to see free air on the left side. It's also important to note that if there is only a small amount of air, that may not be easily seen on the upright chest x-ray. On the supine abdominal film, we will be looking for distended loops of bowel. That's more than 3 cm. Also, in complete obstruction, there is no air in the colon or rectum. As seen in this x-ray, you can see that the small bowel loops are quite distended. They are more than 3 cm if there is a marker available. And this is quite typical of the patterns seen in small bowel obstruction. The second thing you'll notice is that this would be where the rectum would be. And normally you see this black gas pattern around in here as well. But in a small bowel obstruction, sometimes you will not see any air in the rectum. The last x-ray we do is an upright abdominal film. In the upright abdominal film, we're looking for air fluid levels. Air fluid levels occur when there is nothing going south in the lumen. And so the fluid that's in the lumen itself sits in a pattern that looks like ladders. And they're perfectly horizontal lines. On a film, they look like this. So these would be air fluid levels that you can see in multiple levels all across the lumen of the small bowel. Air fluid levels can also be seen in patient with gastroenteritis as well or ileus post-abdominal surgery. It doesn't necessarily have to mean obstruction. And so air fluid levels need to be taken in contact with the patient who is presenting. Sometimes if the patient is unable to sit upright because they're very uncomfortable, you can also do a lateral decubitus view, having a patient lie on one side. And that can also see air fluid levels as shown in here. In patient with a large perforation, even on the decubitus film, you can still see the free air that's between the chest wall and the liver edge. The sensitivity of x-ray and bowel obstruction is about 75% and the specificity is about 50% only. In cases where the plane films are not helpful, we move on to CT. CT will give more information than plane films. It will tell you what's causing the obstruction, where their transition point is for the obstruction, and how narrow the lumen is. It is also way more sensitive in picking up perforation. Lab studies are an adjunct for small bowel obstruction. Usually for baseline, we order CBC lights, creatinine as baseline study and to assess hydration status. If the patient is going to the operating room, we often will do type in screen and coagulation studies as well. Let's put it all together and decide how we should treat a patient with potential small bowel obstruction. As with all things, we assess ABC. We ensure that the airway and breathing are adequate in the patient. For circulation, if the patient is hypotensive or tachycardic, we need to give them IV fluids to bring up their blood pressure and normalize the heart rate. Paying medication should also be given. This should occur in parallel with our investigations. If the patient has signs of peritonitis, we should give them antibiotics. After a small bowel obstruction is being diagnosed and confirmed on either X-ray or CT, we would discuss with the surgery team to determine the whether an operation is needed. Patients with peritonitis and perforation will need to go to the operating room. If the patients do not need to go to the operating room for repair, that's most of the time. We often will put in a nasogastric tube to decompress the stomach. We need to reassess the patient to ensure that their vital signs are normal. We will also give them medication to treat pain and nausea. They will usually be admitted for observation. In summary, we discuss small bowel obstructions. Here are the key points. One, that adhesions are the main cause of small bowel obstruction. Do not forget that hernia is also a cause as well. If we suspect a small bowel obstruction, we should obtain an upright chest X-ray, an upright and supine abdominal X-ray, and look for free air on the diaphragm for the upright chest X-ray, dilated bowel loops for the supine abdominal X-ray, and airflow level for upright abdominal X-ray. If the diagnosis is unclear on the X-ray, CT will be the imaging of choice. Patients with peritoneal signs should be given antibiotics and referred to surgery early on. Thank you for watching.