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Small Bowel Obstruction (SBO): Examination & Diagnosis

by Sharon Bord, MD
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    00:01 What do patients present with and what do you see on your physical examinations? So patients can have crampy abdominal pain, nausea and vomiting, and you can imagine that if you have blockage of your intestinal cavity that you’re not able to have the fluids and the products from the stomach adequately go through the intestines, patients can have a lot of nausea and vomiting.

    00:24 Patients may experience distention of their abdomen.

    00:28 Their abdomen may be more swollen and they may or may not be passing gas, be having flatus, and bowel movement.

    00:34 There are certain situations where patients may still have some flatus and be passing some bowel movements.

    00:41 The most classic thing is that there won’t be any of that but there are some patients due to different physiologic processes that can still have a little bit.

    00:50 One key thing that you don’t wanna forget to ask about are prior surgeries or prior obstruction.

    00:56 The prior surgery thing can be very tricky.

    00:58 Patients aren’t always totally forthcoming and they might not necessarily realize that something counted as an abdominal surgery.

    01:05 It’s very important that you ask clearly if they’ve ever had any kind of procedure.

    01:10 Procedures if they had them even 20 or 30 years ago can still predispose to development of adhesions.

    01:17 So sometimes you have to ask people to really think back in their medical history.

    01:21 Patients sometimes come in there 70 years old and they had a hysterectomy when they were 25, that’s still an abdominal surgery that you need to know about.

    01:30 Same thing with tubal ligation.

    01:31 That’s an abdominal surgery that can put people at risk for adhesions and again, it might have happened very remotely from the time that they’re presenting with their symptoms.

    01:40 This is a situation also where it’s helpful to look at the patient’s belly.

    01:44 If a patient’s not able to tell you or doesn’t tell you that they’ve had any surgeries, sometimes you lift up their gown and you see this big midline surgical scar and you have to sort of prompt them and ask them what exactly happened there.

    01:56 That happens all the time.

    01:58 I know that it seems like it potentially may not happen but all the time, patients are not forthcoming or don’t remember, so figuring out this information is very helpful.

    02:06 So what do we wanna do to help make this diagnosis? So we would definitely wanna make sure we’re asking the right historical questions, that we’re doing an appropriate physical exam, you wanna make sure also that you’re listening to the patient’s abdomen and hearing if you hear any bowel sounds or don’t hear any bowel sounds.

    02:24 You wanna check some labs.

    02:27 Now, labs here are nonspecific.

    02:29 This isn’t gonna be the thing that’s gonna slam dunk make you your diagnosis.

    02:33 You do wanna consider sending a lactic acid because one thing that can happen when you have a small bowel obstruction is you can then get dead bowel.

    02:42 You can get ischemia of some of the bowel that’s present.

    02:45 An elevated lactate supports the diagnosis of strangulation or obstruction, or ischemia of that bowel, piece of bowel.

    02:53 So looking for that elevated lactate and considering that elevated lactate is key.

    02:58 Now, for imaging, again, three options here.

    03:03 So three options are majority of our testing for things related to the abdomen.

    03:08 The first is plain film x-ray, then CT scan, and then ultrasound, and we’re gonna be exploring each of these individually.

    03:16 The first is plain film x-ray.

    03:18 Plain film x-ray used to be the mainstay in diagnosis of bowel obstruction.

    03:22 It used to be the initial first test that everyone would get and for the most part, if it showed bowel obstruction, the patient would get a surgery consult, they would get admitted to the hospital for surgery.

    03:33 Now we know that the plain film of the x-ray while although it can definitely show you evidence of bowel obstruction.

    03:39 So here you could see that there is distended loops and we know that this is a small bowel obstruction because we see things that are called plicae circulares which are basically a portion of the bowel that crosses across the bowel, and that will help you distinguish it from a large bowel obstruction.

    03:56 So in a large bowel obstruction, you won’t see those fine white lines because the large bowel does not have plicae circulares, so that’s a good way to help you distinguish.

    04:05 What we know though about the plain film x-ray to evaluate for obstruction is we know it’s not a great test.

    04:11 It doesn’t have a great sensitivity, it doesn’t have a great specificity while although you can get it easily, it’s a relatively cheap film, you can get it at the bedsides, so for more critically ill patients, it’s good, but it’s not a great test.

    04:26 If this test is negative for bowel obstruction, that doesn’t necessarily mean you’re done.

    04:31 It means that you need to move on and get additional imaging.

    04:35 That you need to move on and get a CAT scan.

    04:37 The other thing that does sometimes happen now is even if this reveals a clear bowel obstruction, oftentimes, surgery will request that we get a CT scan as well because the CT scan can give us lots of additional information.

    04:52 It can show where the lead point is, it can show if it’s a closed loop obstruction, it can see if there’s any thickening of the bowel wall, so CT scan’s gonna give us a lot more information.

    05:01 So while plain film x-ray could potentially be a good starting point, it’s oftentimes not an end point, so it’s oftentimes not the thing that’s gonna be your last imaging study of choice.

    05:12 The one thing that plain film x-ray can do is it can show you if there’s any kind of bowel perforation, so it can show you if there’s any free air under the diaphragm.

    05:21 Again, not the most sensitive test for that diagnosis but it’s a good starting point especially for the sicker patient.

    05:29 Moving on, we can think about CAT scan.

    05:32 CAT scan again has benefits in the sense that it can give you lots of information.

    05:37 It can show you a lot of different diagnosis in addition to showing you a small bowel obstruction.

    05:41 It can show if there’s a lead point there.

    05:43 It can show if there’s bowel wall thickening.

    05:45 Here on the CT scan, you could see that there is lots of dilated loops of bowel and there are some air fluid levels, so on the bowel loops that are closest to the anterior portion of the abdomen, you could see that there’s air fluid levels, that there’s fluid at the base and then air up at the top.

    06:00 This is kind of classic for small bowel obstruction and a classic picture of what you would potentially see.

    06:08 So CT scan is definitely the imaging modality of choice for a majority of patients.

    06:13 Know there are definitely risks associated with CT, the primary one being ionizing radiation exposure.

    06:21 So for pregnant patients or patients in whom we don’t wanna expose them to ionizing radiation, you definitely wanna think critically about getting your CAT scan but this is really your test of choice here.

    06:32 This is your test that’s gonna give you the most information and it’s gonna be the most helpful in making the diagnosis of bowel obstruction.

    06:39 The other imaging modality is ultrasound.

    06:43 Ultrasound is a great test in the sense that it can be done quickly, it can be done rapidly, it can be performed at the bedside, and it’s relatively cheap, so it has a lot of advantages.

    06:54 Ultrasound what it can show you is it can show you that the loop of bowel is potentially dilated and also that there’s no peristalsis.

    07:02 So what peristalsis is, is it’s the moving of the fluid through the intestines and what you’re gonna see on the ultrasound is you’re gonna see that the bowel is not peristalsing, the bowel is not moving.

    07:14 It’s dilated and things were kind of just sitting there.

    07:17 So ultrasound may be a good test.

    07:19 There might be more to come on this in the future when ultrasound maybe utilized for this diagnosis more in the Emergency Department.


    About the Lecture

    The lecture Small Bowel Obstruction (SBO): Examination & Diagnosis by Sharon Bord, MD is from the course Abdominal and Genitourinary Emergencies.


    Included Quiz Questions

    1. Lactate
    2. AST
    3. BUN
    4. Creatinine
    5. Amylase
    1. Presence of plicae circulares
    2. Presence of haustra
    3. Presence of bowel distention
    4. Presence of bowel gas
    5. Presence of calcification
    1. CT scan
    2. Plain x-ray radiograph
    3. Ultrasound
    4. MRI
    5. Colonoscopy
    1. Peristalsis
    2. Colic
    3. Reverse peristalsis
    4. Segmentation
    5. Retropulsion

    Author of lecture Small Bowel Obstruction (SBO): Examination & Diagnosis

     Sharon Bord, MD

    Sharon Bord, MD


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