Small bowel obstruction: Clinical sciences

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Introduction0:00–0:34

Small bowel obstruction, or SBO, occurs when intraluminal contents like chyme and gas are unable to pass through the small intestine due to a blockage.
Blockages can be mechanical, which is a physical obstruction, such as adhesion, hernia, or tumor; or functional, which is caused by reduced or absent peristalsis, also called an ileus.
Some SBOs resolve with conservative management, but others may require surgical intervention.When approaching a patient with signs and symptoms suggestive of small bowel obstruction, first perform an ABCDE assessment to determine if the patient is stable or unstable.

Unstable patient0:34–3:55

Let’s start with what to do if the patient is unstable. Start acute management immediately to stabilize their airway, breathing, and circulation.
This means that you might need to intubate the patient, obtain IV access, administer fluids, and monitor their vitals before continuing with your assessment.
Your next step is to obtain a focused history and physical exam, as well as labs. Labs will include CBC, CMP, and lactate.
Now, history might reveal bloating, abdominal pain, obstipation, and nausea and vomiting. Here’s a high-yield fact!
You can suspect some causes of SBO based on history. For example, ask your patients about any prior abdominal surgeries or known hernias.
Both are common causes of mechanical SBO. Okay, let’s move on to the physical examination.
The exam may reveal tachycardia and hypotension, as well as abdominal distension and signs of peritonitis, like diffuse tenderness to palpation, rebound pain, and guarding.
Remember to look for surgical scars and hernias during your exam! An incarcerated ventral or inguinal hernia often presents as a tender palpable mass, sometimes with overlying inflammatory skin changes.
Finally, labs may show leukocytosis, as well as lactic acidosis from bowel ischemia. If you see these signs and symptoms, suspect SBO.The next step is to start supportive care.
You should initiate IV fluid resuscitation, electrolyte replacement, broad-spectrum antibiotics, and bowel rest, as well as nasogastric tube placement for bowel decompression if the patient has nausea and vomiting.
Once you initiate supportive care, order an abdominal x-ray. Alright, let’s discuss abdominal X-ray findings that indicate SBO.
Findings may include small bowel dilatation with distended loops and air-fluid levels; as well as pneumoperitoneum, meaning that perforation has already occurred.
When you encounter any of these signs, you should quickly think of complicated small bowel obstruction and obtain surgical consultation for emergent laparotomy.Here’s a clinical pearl!
The surgical team may order a CT scan to confirm the diagnosis. If there’s complicated SBO, CT may typically show signs of bowel ischemia, such as pneumatosis and portal venous gas.
Additionally, CT helps reveal a transition point, where the small bowel is distended to the point of obstruction but collapsed beyond it; and absence of gas in the colon and rectum.
Having two or more transition points is called a closed-loop obstruction, and this can quickly progress to bowel ischemia and perforation.
Common causes of closed-loop obstruction include small bowel volvulus, adhesions, and hernias. Okay, now that the unstable patients are taken care of, let’s talk about stable patients.

Stable patient3:55–4:54

Keep in mind that patients who present as stable might develop complicated SBO and become unstable if not promptly treated.
So again, start with your ABCDE assessment. Your next step is to obtain a focused history and physical exam, as well as labs like CBC, CMP, and lactate.
Stable patients typically report bloating, abdominal pain, and obstipation, often with nausea and vomiting. Again, remember to ask about prior abdominal surgeries and hernias.
On the other hand, the physical exam often reveals abdominal distension, tenderness to palpation, and sometimes high-pitched hyperactive bowel sounds on auscultation.
Note any surgical scars or hernias. Finally, labs might show leukocytosis or lactic acidosis.
At this point, you can suspect SBO, so start supportive care. As before, supportive care includes IV fluid resuscitation, electrolyte replacement, bowel rest, broad-spectrum antibiotics, and nasogastric tube placement for bowel decompression if the patient is having nausea and vomiting.Once the supportive care is initiated, order an abdominal and pelvic CT with oral and IV contrast to diagnose the condition and identify the underlying cause.

Supportive care4:54–5:14

Imaging5:14–5:34

Alright, let’s consider possible CT findings of mechanical SBO. Once again, you might encounter small bowel dilatation with distended loops and air-fluid levels, as well as evidence of one or more transition points, and an absence of gas in the colon and rectum.

Mechanical Small Bowel Obstruction5:34–5:48

Now that you’ve diagnosed mechanical small bowel obstruction, the next step is to decide whether the underlying cause requires surgery.

Operative Cases5:48–7:22

Operative SBO cases include obstructions that are unlikely to resolve with supportive care alone or require further workup.
An example is primary small bowel tumors. They might obstruct the bowel at later stages when their growth is sufficient to cause a blockage.
Another frequent cause involves internal or external hernias. An internal hernia occurs when congenital or post-surgical anatomy allows a segment of the bowel to become trapped within the abdomen itself.
However, external hernias, in which the bowel protrudes through a weakness of the abdominal wall and gets stuck, are more common.
Additionally, an uncommon cause is gallstone ileus, which occurs when a gallstone enters the small intestine through a biliary-enteric fistula and becomes lodged in the ileum.
Similarly, an ingested foreign body can become impacted in the small intestine leading to a blockage. Finally, intussusception happens when the small intestine telescopes into itself or into the cecum around a lead-point, causing an obstruction.
Now, each of these conditions requires surgery to treat the underlying cause. So, go ahead and call the surgery team for an emergent laparotomy.
Okay, let’s go back a step, and talk about patients who may not require surgery. In these patients, the CT reveals a single transition point and no signs of bowel ischemia or perforation.

Conservative cases7:22–10:54

The obstruction can be classified as partial or complete depending on whether bowel function is preserved. The most common cause of simple mechanical SBO are intraperitoneal adhesions.
These bands of scar tissue typically result from the prior abdominal operation and can trap or block off the intestine. On CT scan, adhesions themselves are not usually visualized, so you’d suspect adhesive SBO when you see a transition point without an identifiable cause.
Other causes of SBO include inflammatory bowel disease, as well as malignant bowel obstruction from metastatic tumors, or radiation enteritis.
If the patient is not showing signs of sepsis or a worsening abdominal exam, a course of conservative management is indicated.
However, keep in mind that patients who clinically worsen or don't progress will ultimately need to go to surgery.Ok, now let’s talk about conservative management.
First, continue supportive care, including fluid and electrolyte repletion, bowel decompression, as well as serial abdominal exams and x-rays to monitor the patient.
Additionally, obtain further workup to identify and treat underlying causes if necessary. Now, here’s a high-yield fact!
In patients with adhesive SBO, a bolus of water-soluble enteric contrast, given orally or through a nasogastric tube, followed by serial x-rays, can have a diagnostic and therapeutic effect, in helping to both identify and resolve the obstruction.
Alright, so after giving conservative management, evaluate the patient frequently to assess their response to management.
Look for evidence of a return of bowel function, such as bowel movements and flatus, listen for increased bowel sounds, and assess for decreased abdominal pain and distension on physical exam and X-ray.
If they have an adequate response with return of bowel function, continue supportive care and treat the underlying cause.
Additionally, you can see if the patient tolerates a trial of oral nutrition. However, if they have an inadequate response, meaning no improvement after 3 to 5 days of conservative management, or they show signs of peritonitis, new hemodynamic instability, signs of impending perforation, or imaging signs of bowel ischemia, you should call the surgical team for emergent laparotomy.
Alright, let’s go all the way back to the CT scan to discuss a few more possibilities you should keep in mind. Let’s say the CT scan shows a diffusely dilated small intestine with air-fluid levels, there’s no evidence of a mechanical blockage, and there is gas in the colon or rectum.
This indicates a functional obstruction from a lack of intestinal motility, also called an ileus. Lastly, If there are no radiographic signs of small bowel obstruction on CT, you should consider an alternative diagnosis.Alright, as a quick recap… A patient with small bowel obstruction can present as stable or unstable.

Review10:54–11:40

Unstable patients should be assessed with an abdominal x-ray and treated surgically. On the other hand, stable patients should be assessed using a CT of the abdomen and pelvis with oral and IV contrast.
Patients with mechanical small bowel obstruction might require surgical intervention if the underlying cause is unlikely to resolve with supportive care alone, or if it requires further workup.
Alternatively, some patients, such as those with adhesive small bowel obstructions, can be managed conservatively with supportive care alone.
If the patient improves, you can continue supportive care and treat the underlying cause. However, if they don’t improve, or even worsen, call the surgical team for emergent laparotomy.
supportive care and treat the underlying cause However if they don't improve or even worsen call the surgical team for