Large bowel obstruction: Clinical sciences

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Introduction0:00–0:56

Large bowel obstruction occurs when a blockage interferes with the passage of intraluminal contents like stool and gas for the colon.
When this leads to infrequent or difficulty passing stool or flatus, it's called constipation. While total inability to pass stool and flatus is known as obstipation.
Blockages can be mechanical, which is when there is a physical obstruction such as a tumor or volvulus or pseudo obstructions, also known as Ogilvie syndrome, which means that the obstruction is functional and the bowel isn't working properly.
So normal peristalsis is disrupted because the content of the bowel is unable to pass. Large bowel obstruction can lead to bowel dilatation, ischemia, perforation, and finally sepsis.
When assessing a patient with signs and symptoms, suggestive of large bowel obstruction, first perform an ABCD E assessment to determine if the patient is unstable.

Unstable patient0:56–3:49

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. The next step is to obtain a focused history and physical exam as well as labs like CBC CMP and lactate.
Now, history might reveal abdominal bloating, abdominal pain, ranging from crampy to diffuse in nature, obstipation and sometimes nausea and vomiting.
The onset of symptoms usually ranges from hours to days. Physical exam typically shows abdominal distension and signs of peritonitis such as diffuse tenderness to palpation, rebound pain and guarding.
Finally, labs may show leukocytosis as well as lactic acidosis from bowel ischemia. All right, if you see these signs and symptoms, suspect large bowel obstruction.
The next step is to start supportive care. Supportive care involves IV fluid resuscitation and vasopressor support electrolyte replacement, broad spectrum antibiotics as well as bowel rest and nasogastric tube placement for bowel decompression.
If the patient is having nausea and vomiting, once supportive care is initiated, you can order an abdominal X ray series.
Now, the X rays might show large bowel dilatation and signs of ULV, which is the twisting of the colon along its mesentery.
The first being northern exposure sign which occurs when a single dilated loop of the large bowel extends above the level of the transverse colon.
The second potential sign called coffee bean sign refers to a massively dilated loop of the large bowel twisted around itself that resembles a giant coffee bean.
Additionally, an X ray might show some serious signs like pneumatosis, which means that there might be necrosis, cecal diameter greater than 12 centimeters, which is concerning for impending perforation and finally, pneumoperitoneum, which indicates that perforation has already occurred if you see any of these signs.
You can diagnose complicated large bowel obstruction, lastly immediately obtain abdominal and pelvic CT scan and surgical consultation for emergent laparotomy.

Stable patient3:49–4:59

Ok. Now that the unstable patients are taken care of, let's return to the ABCDE assessment and talk about stable patients.
Your first step here 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 with or without nausea and vomiting.
Here is a high yield fact, some causes of obstruction can be suspected based on history. For example, growing tumors increasingly obstruct the large bowel.
So these patients might report a longer duration of symptoms, progressively narrow stool caliber rectal bleeding and unintentional weight loss on the flip side.
A physical exam often reveals abdominal distension and sometimes abdominal tenderness to palpation. Finally, labs might demonstrate leukocytosis or lactic acidosis.
At this point, you can suspect a large bowel obstruction. So be sure to start supportive care as before supportive care includes IV, fluid resuscitation, electrolyte replacement, and broad spectrum antibiotics as well as bowel rest and nasogastric tube placement for bowel decompression.

Supportive care4:59–5:16

If the patient is having nausea and vomiting. Once the supportive care is initiated, you can move on to imaging order a CT of the abdomen and pelvis with oral and IV contrast to diagnose the condition and possibly find the underlying cause.

Imaging - Mechanical LBO5:16–6:36

Next, let's consider possible ct findings of mechanical large bowel obstruction, over half of the large bowel obstructions are mechanical obstructions caused by colorectal malignancies.
On CT, this may appear as a segment of the colon narrowed by an annular mass which is frequently referred to as an apple core sign because of its similar appearance.
Another cause of mechanical large bowel obstruction is volvulus. In this case, CT might show signs like a whirl sign which looks like a swirling pattern in the mesentery caused by the twisting around its axis.
Now, CT might also show other causes of mechanical obstruction, like intrinsic causes such as masses or strictures from previous colon inflammation or ischemia or extrinsic causes such as hernias or adhesions.
Finally, in some cases, CT might reveal foreign objects in the colon or rectum or even fecal impaction. Ct imaging can be very helpful to differentiate the grade of obstruction.

Mechanical obstruction: complete vs. incomplete6:36–8:25

But the important thing to do here is to assess the bowel function. More specifically, you should see if they are able to pass flatus or not.
Passing stool is less specific as the stool they pass might have been distal to the obstruction. Now, if they are not able to pass flatus, that means there is no bowel function.
So the patient probably has a complete bowel obstruction if this is the case, obtain a surgical consultation for laparotomy.
On the other hand, passing flatus suggests that bowel function is present. So the patient probably has an incomplete obstruction.
This type is typically managed with supportive care, which includes continuing fluids and electrolyte repletion, bowel decompression, as well as serial abdominal exams and x rays.
To monitor the patient. Additionally, be sure to do further work up to identify the underlying cause.
For example, if colon cancer is suspected, additional steps like CT scan of the chest tumor markers and colonoscopy with biopsy should be completed.
Now, if a patient has an adequate response to supportive care, continue this management and treat the underlying cause. However, sometimes a patient might have an inadequate response to treatment.
This can include developing signs of peritonitis, new hemodynamic instability, signs of impending perforation or worsening labs and imaging.
Concerning for ischemia. If this is the case, call the surgical team for an emergent laparotomy.

Colonic pseudo-obstruction8:25–9:36

All right, let's move on and talk about pseudo obstructions which happen without mechanical blockage. Risk factors for pseudo obstructions include advanced age hospitalization, severe illness, recent trauma or surgery, certain medications like opioids and electrolyte imbalances.
In this case, CT might show colon dilatation without signs of mechanical obstruction if you see this suspect pseudo obstruction and continue supportive care with the addition of discontinuing opioids and motility inhibiting medications.
If the patient was taking them. If the obstruction persists, you can attempt a trial of neostigmine once again, if the patient has an adequate response to treatment, continue supportive care and treat the underlying cause.
However, if they have an inadequate response or show signs of peritonitis, new hemodynamic instability, persistent dilatation and signs of impending perforation or labs and imaging.
Concerning for ischemia. You should call the surgical team for emergent laparotomy.
Lastly, let's go back to imaging once more. If there are no signs of large bowel obstruction on CT, you should consider an alternative diagnosis.

No signs of large bowel obstruction9:36–9:49

Review9:49–11:09

All right, as a quick recap, a patient with large bowel obstruction can present as stable or unstable, unstable patients should be assessed with an abdominal X ray and treated surgically.
On the other side, stable patients should be assessed using a ct of the abdomen and pelvis with oral and IV contrast patients with complete mechanical large bowel obstruction also require surgical intervention.
Don't forget to treat the underlying cause of the obstruction. Now, patients with incomplete large bowel obstruction can be initially managed with supportive care, which includes IV fluids and electrolytes, bowel rest and serial abdominal exams and x rays.
You might also need to do an additional work up to identify the underlying cause. 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. Patients with pseudoobstruction are also treated with supportive care as well as discontinuing opioids and a possible trial of neostigmine.
If they improve, you can continue supportive care and treat the underlying cause. However, if they don't improve or worsen, obtain a surgical consultation for an emergent laparotomy
Large bowel obstruction: Video, Causes, Symptoms | Osmosis