Ileus: Clinical sciences

Ileus is a functional obstruction of the intestines caused by reduced or absent peristalsis without evidence of mechanical blockage.

Both functional and mechanical obstructions present with similar signs and symptoms. So, before you diagnose ileus, you must first rule out a mechanical obstruction such as small bowel obstruction. Ileus most commonly occurs after abdominal operations, which is referred to as postoperative ileus. However, it can also be caused by a wide variety of underlying medical conditions like heart failure, systemic infection, or medications such as opiates. This is called a non-postoperative ileus.

Alright, when assessing a patient with signs and symptoms suggestive of ileus, you must first perform an ABCDE assessment to determine if the patient is unstable or stable. 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, administer supplemental oxygen, obtain IV access, administer fluids, and monitor their vitals before continuing with your assessment. Also, if your patient is postoperative, don’t forget to examine their surgical wounds!

Now that we’re done with acute management of unstable patients, let’s get back to the ABCDE assessment and talk about stable patients. The first step here is to obtain a focused history and physical exam, as well as order labs like CBC, CMP, and lactate. In stable patients, the history typically reveals inability to tolerate oral intake, bloating, abdominal pain, and obstipation, with or without nausea and vomiting.

Here is a high-yield fact! You can suspect some causes of ileus based on history. For example, remember to ask your patients about any recent abdominal operations or opioid usage. Both are common causes of reduced intestinal motility on their own; together they can lead to a prolonged state of intestinal paralysis.

Ok, let’s get back to the physical examination. The physical exam will often reveal abdominal distention, and sometimes abdominal tenderness on palpation. On auscultation, bowel sounds might be reduced or absent. Finally, lab results might show electrolyte abnormalities such as hyponatremia or hypokalemia.

At this point, you can suspect ileus, but the differential diagnosis still includes mechanical obstruction, so let’s move on to imaging to differentiate the two. To start, obtain an abdominal x-ray series. First, let’s consider possible abdominal x-ray findings that indicate a mechanical obstruction. These may include small bowel dilatation with air-fluid levels; and absence of any gas in the colon and rectum. These findings are highly suggestive of mechanical obstruction, so you should call the surgical team for a consultation.

Here’s a clinical pearl! The surgical team may order an abdominal and pelvic CT with contrast to confirm the diagnosis. If there’s mechanical obstruction, CT may show evidence of a transition point, where the small bowel is distended to the place of obstruction but collapsed beyond.

Alright, now that mechanical obstruction is diagnosed, let’s go back to x-ray and talk about ileus. The x-ray might reveal small bowel dilatation without evidence of a transition point or mechanical obstruction. Additionally, there could be gas present in the colon and rectum. Once you have confirmed on imaging that the patient has an ileus, it is important to return to the patient's history and identify whether they recently had a prior abdominal operation. If the answer is no, then your diagnosis is a non-postoperative ileus.