GI Emergencies: GI Emergencies: Ogilvie Syndrome

0:00Welcome to Board Pearls. This is episode four of four, the last episode of the GI Emergencies chapter, in the Special Populations and Acute or Supportive Care module. This episode is acute colonic pseudo-obstruction, also called Ogilvie syndrome, followed in one man after hip surgery. His case shows why the colon dilates with nothing blocking it, what has to be excluded before treatment, what supportive care involves and how often it works, why the cecum is the measurement that decides escalation, how neostigmine is given safely and who can't have it, and what follows if it fails.

0:34Here's the patient. A seventy-six-year-old man is on day three after a right hip replacement, on scheduled oxycodone and in bed since surgery. Over two days his abdomen has become hugely distended and tympanitic but only mildly tender. He's passing a little gas and no stool. His potassium is three point one and his magnesium is low. His heart rate is eighty-eight, and he has no fever.

0:59He most likely has acute colonic pseudo-obstruction, Ogilvie syndrome: acute massive dilation of the colon without a mechanical obstruction, in a hospitalized patient. The findings that point to it are a hugely distended, tympanitic abdomen with little tenderness, developing over two days after surgery, in a man on opioids with low potassium and magnesium. The cause is autonomic imbalance at the colon, with relative sympathetic overdrive and parasympathetic underdrive. That imbalance is often unmasked by electrolyte disturbances, opioids, antipsychotics, anticholinergics, retroperitoneal inflammation, surgery, severe medical illness, or spinal cord injury, and he has three of them: surgery, oxycodone, and low electrolytes. The proximal colon dilates most, because it's physically larger and because the right colon depends particularly on vagal parasympathetic input, which the imbalance disrupts. The incidence is roughly one hundred per hundred thousand admissions, and eighty-six to ninety percent of patients have several comorbid illnesses, such as orthopedic, cardiac, or abdominal surgery, sepsis, intensive care unit, ICU, admission, severe burns, or retroperitoneal hemorrhage. That's why the typical patient, like him, is hospitalized, on opioids, and distends over forty-eight to seventy-two hours. The chronic form of pseudo-obstruction is a separate motility disorder, covered in chapter eight.

2:30His management follows four steps in order: exclude mechanical obstruction, give supportive care, escalate to neostigmine, and then decompress colonoscopically, with his cecal diameter and the duration of his distension deciding when to move up. The first step comes first because a mechanical cause that looks like pseudo-obstruction won't respond to neostigmine and may perforate during conservative care. Computed tomography, CT, of the abdomen and pelvis with intravenous and oral or rectal contrast is the imaging of choice. In pseudo-obstruction it shows a dilated colon without a transition point, with the cecum and right colon dilated out of proportion to the distal colon. The alternatives it has to exclude are mechanical obstruction, which has a transition point; sigmoid or cecal volvulus, with a coffee-bean or whirl sign; and toxic megacolon, with mucosal abnormalities and a clinical picture of severe colitis. A water-soluble contrast enema is used when CT is equivocal or retroperitoneal disease hides the colonic anatomy. His CT shows diffuse colonic dilation with no transition point and no whirl, and a cecal diameter of ten and a half centimeters, the baseline every later film is compared with.

3:46With obstruction excluded, he starts supportive care, because it treats the precipitants that unmasked the imbalance. For the first forty-eight to seventy-two hours, in a stable patient whose cecum is below the escalation threshold, the bundle is nothing by mouth; a nasogastric tube to suction, for proximal decompression; a rectal tube, for distal decompression; walking when feasible; correction of electrolytes, especially potassium, magnesium, calcium, and phosphate; stopping opioids and anticholinergics where possible; and treating any underlying illness, such as sepsis or retroperitoneal inflammation. Alternating prone and knee-chest positions also helps, using gravity to move gas through the dilated colon. This bundle resolves about eighty percent of cases without anything more. His potassium and magnesium are corrected, his oxycodone is switched to non-opioid analgesia as far as his surgeon allows, nasogastric and rectal tubes are placed, and physiotherapy gets him sitting out of bed and changing position.

4:43His opioids raise one more option, though it isn't where his treatment starts. Methylnaltrexone, twelve milligrams under the skin, can be considered in opioid-induced cases, because it blocks peripheral mu-opioid receptors and reverses the opioid effect on gut motility without crossing the blood-brain barrier. The evidence in pseudo-obstruction specifically is limited, and it isn't first line.

5:06While supportive care runs, his cecum is measured daily, because its diameter is what triggers escalation. The triggers are a cecal diameter over twelve centimeters, distension that persists beyond forty-eight to seventy-two hours despite supportive care, or signs of impending perforation. The cecum is the segment that perforates because of Laplace's law: at a given pressure, wall tension rises with diameter, so the widest segment fails first. The risk of spontaneous perforation is about three to twenty-five percent, with up to fifty percent mortality once it happens, and the risk climbs once the cecum passes ten to twelve centimeters and once distension lasts more than six days. Two days later his films show no improvement, and his cecum now measures twelve point eight centimeters. He's over twelve centimeters after more than forty-eight hours of supportive care, so he escalates today.

5:59His escalation is neostigmine, because it reverses the imbalance that caused his dilation. Neostigmine, two milligrams intravenously over three to five minutes, is the drug of choice when the supportive bundle fails or escalation is needed urgently. It's a short-acting anticholinesterase that raises acetylcholine at the colonic ganglia, restoring parasympathetic drive to the dilated colon and producing rapid evacuation of gas and stool. That same parasympathetic effect causes its side effects: bradycardia, occasionally severe, hypotension, bronchospasm, and salivation. So cardiac monitoring during and after the dose is mandatory, with atropine, one milligram, drawn up at the bedside for rescue. Glycopyrrolate, a peripheral anticholinergic that doesn't cross the blood-brain barrier, can be given alongside to blunt bradycardia and other peripheral muscarinic effects without reversing the drug's effect on the colon.

6:56Because those side effects can be dangerous, he's checked for every contraindication before the dose. The contraindications are mechanical bowel or urinary obstruction, recent myocardial infarction, severe bradyarrhythmia or conduction disease, active reactive airway disease, because of bronchospasm, a seizure history, peritoneal signs, suspected ischemia, perforation, and known hypersensitivity. His CT excluded obstruction, he has no recent infarction, his heart rate is eighty-eight without conduction disease, and he has no asthma, seizures, or peritoneal signs. He gets neostigmine on a monitor with atropine at the bedside, and within twenty minutes he passes a large volume of gas and stool and his abdomen softens. Had he had an infarction last month, or a heart rate of forty-eight on a beta-blocker, neostigmine would have been contraindicated and he'd have gone straight to colonoscopic decompression.

7:51If he hadn't responded or couldn't have neostigmine, other drugs exist but don't change the sequence. Oral pyridostigmine and peripheral mu-opioid receptor antagonists such as methylnaltrexone are reported in case series for non-responders and for patients who can't have neostigmine, but neither has high-quality evidence in pseudo-obstruction. So neither replaces the next step or justifies days of delay while his cecum widens. If his distension returned after neostigmine, he'd be judged again by his cecal diameter and his contraindications, with repeat neostigmine if it's still safe, or colonoscopic decompression if it isn't.

8:32Colonoscopic decompression is the next step when neostigmine fails, is contraindicated, or can't be repeated, and its technique differs from routine colonoscopy because the goal is different. The colon isn't prepped, and the aim is decompression rather than diagnosis. Insufflation is kept minimal, with carbon dioxide preferred because it's absorbed faster and worsens distension less than air. Narcotic sedation is avoided, because it worsens the dysmotility. The mucosa is examined carefully for ischemia, because about ten percent of patients have some right-sided colonic ischemia at colonoscopy, which itself raises the risk of perforation during decompression. And a decompression tube is placed into the right colon over a guidewire, so gas keeps evacuating after the procedure ends. Randomized trials haven't established its efficacy, but observational data suggest immediate decompression in seventy to eighty percent of patients, with recurrence in thirty to forty percent that often responds to repeat decompression.

9:30Surgery is the last step, reserved for clinical deterioration, peritoneal signs, a cecum that stays above twelve centimeters after medical and endoscopic options are exhausted, perforation, or failure of every other therapy. The operations are cecostomy, colectomy, or ileostomy. Surgical mortality is high, because the patients who reach this point are usually critically ill from the illness that drove the pseudo-obstruction in the first place. If he'd developed fever, rebound tenderness, and free air under the diaphragm on day five, that would be perforation with peritonitis, which contraindicates neostigmine and sends him to the operating room.

10:09Here are the traps the boards set in these patients. Pseudo-obstruction isn't treated until CT has excluded mechanical obstruction and volvulus. The supportive bundle comes first in a stable patient whose cecum is below twelve centimeters. Potassium, magnesium, calcium, and phosphate all need correcting. Opioids and anticholinergics are stopped where possible. A cecum over twelve centimeters, or distension persisting beyond forty-eight to seventy-two hours, means escalation, not more waiting. Neostigmine is given only with cardiac monitoring and atropine at hand, and never with bradycardia, recent infarction, active bronchospasm, obstruction, or peritoneal signs. During colonoscopic decompression, insufflation is minimal, narcotic sedation is avoided, and a decompression tube is left in. And perforation or peritonitis goes to surgery without delay.

11:08So, start to finish. Exclude mechanical obstruction and volvulus with CT first. Then give forty-eight to seventy-two hours of supportive care: stop opioids and anticholinergics, correct electrolytes, decompress with nasogastric and rectal tubes, mobilize, and change position, which resolves about eighty percent of cases.

11:29Escalate for a cecum over twelve centimeters, failure to improve, or impending perforation, with neostigmine two milligrams intravenously over three to five minutes, on a monitor with atropine at hand, and never with bradycardia, recent infarction, bronchospasm, or obstruction. If neostigmine fails or can't be given, decompress colonoscopically with minimal carbon dioxide and a decompression tube, which succeeds immediately in seventy to eighty percent. Surgery is for perforation, peritonitis, or failure of everything else.

12:05That completes chapter thirty-one. Chapter thirty-two is gastrointestinal nutrition: refeeding, enteral and parenteral feeding, short bowel, vitamins, and minerals.

12:16For the full chapter, the practice vignettes, and the topic-tagged question bank, head to board pearls dot com. You'll find the rest of the series on Apple Podcasts, Spotify, or wherever you listen to podcasts. That brings us to the end of episode four of four of chapter thirty-one, and I'll see you in the next one.