Acute Colonic Pseudoobstruction (Acute Megacolon, Ogilvie Syndrome) Treatment & Management

Management of acute colonic pseudoobstruction (ACPO) (acute megacolon, Ogilvie syndrome) can be divided into a conservative or interventional approach. Conservative management can be as safe and effective as an interventional approach, with less likely ACPO syndrome-related complications in carefully selected patients. ^[18]  Interventional management has been recommended, especially for critically ill patients, and includes use of acetylcholinesterase inhibitors (neostigmine), gastrostomy tube placement, decompressive sigmoidoscopy/colonoscopy, and colostomy or colectomy.

A unique phenotype, secretory diarrhea and hypokalemia with colonic pseudoobstruction (SD-CPO), requires a distinct approach for management, as this condition  is more difficult to treat and carries a higher mortality as compared to the classic constipation-predominant form. ^[16]

Conservative management is preferred when the patient with acute colonic pseudoobstruction (ACPO) (acute megacolon, Ogilvie syndrome) is clinically stable. It can be continued for 24 to 48 hours in the absence of significant pain, extreme (>12 cm) colonic dilation, or evidence of peritonitis. Consider the following:

• Treat the underlying cause if possible, such as correction of any electrolyte/metabolic abnormalities and removal of medications that may decrease colonic motility (eg, narcotics, anticholinergic agents, calcium channel antagonists).
• Oral feeding should be discontinued, and intravenous fluids should be initiated.
• If nausea and vomiting are present, nasogastric decompression should be initiated.
• Encourage early ambulation when possible.

Decompression

Trans-anal rectal tube placement

Rectal tube can be placed with fluoroscopy guidance or during decompression colonoscopy. It has a 70% technical success and 50% clinical improvement rates. This tube may assist in the treatment only if the sigmoid colon is involved. When such tubes are used, anecdotal experience has demonstrated that frequent position changes for the patient may help improve decompression. Complications with these rectal tubes include tube obstruction and colonic/rectal ulceration.

Colonoscopic decompression

If the dilatation persists or worsens, colonoscopic decompression with or without placement of a tube in the right colon should be considered. Although the placement of a decompression tube per rectum is generally suggested, some experts believe that the tube often becomes obstructed with stool and ceases to work after a short time. Randomized controlled trials of the efficacy of colonoscopic decompression are lacking.  The therapeutic success rate of decompression colonoscopy can be enhanced form less than 50% to 88% by concurrent decompression tube placement. ^[19]  A retrospective study revealed that colonoscopic decompression is more effective as an initial therapy and at avoiding a second treatment modality compared to neostigmine. ^[19]  In patients with secretory diarrhea and hypokalemia with colonic pseudoobstruction (SD-CPO) a trial of concomitant colonic decompression and aldactone is warranted. ^{[14, 20]}  The resolution of ileus, perforation, and mortality rates are similar between endoscopic and conservative management.

Colonic decompression appears to be effective for proximal colonic dilation or ACPO-related symptoms relative to standard medical care alone. ^[21] A 2020 retrospective (2000-2016), propensity-matched study that evaluated the efficacy of colonic decompression with standard medical therapy (supportive care, pharmacotherapy) for treatment of inpatients with first diagnosis of ACPO versus standard medical therapy alone found no significant differences in mid or distal colon diameter reduction between the two groups. However, 47.7% of patients who underwent colonic decompression had complete resolution of ACPO, with a 15.7% 30-day readmission rate, compared to 19.9% of those who received standard care alone (P< 0.001), who had a 26.2% 30-day readmission rate. Moreover, the 30-day all-cause mortality for the colonic decompression group was lower versus the standard medical therapy group (8.4% vs 14.8%, respectively). ^[21]

Neostigmine

Neostigmine is an acetylcholinesterase inhibitor that has been demonstrated in a meta-analysis of randomized-controlled trials to be effective in 90% of treated patients compared to 15% in the control arm, with median time to response of 4 minutes (~3 to 30 minutes) and a number needed to treat (NNT) of 1. ^[22]

The major indication for its use is failure of conservative therapy after 24-48 hours or a cecal diameter of greater than 12 cm.

Contraindications include bradyarrhythmia, recent myocardial infarction, systolic blood pressure of less than 90 mm Hg, active bronchospasm, serum creatinine level of greater than 3 mg/dL, evidence of bowel perforation, or concomitant use of beta-blockers.

Adverse events include abdominal cramping (17%), excessive salivation (13%), transient bradycardia (6%), diaphoresis (4%), and nausea and vomiting (4%). Based on expert opinion, a starting dose of 0.5 -1 mg may reduce the likelihood of developing bradycardia.

Cardiac monitoring of patients during treatment with neostigmine is generally recommended, and atropine should be at the bedside.

A second dose of neostigmine (preferably after 24 hours) should be considered if there is a partial or minimal response to the initial administration. ^{[23, 24, 25]}

Of note, although neostigmine often induces clinical decompression, this decompression has not been shown to reduce perforation and mortality rates, and in patients with SD-CPO neostigmine appears to be relatively ineffective and may aggravate the diarrhea. ^[16]

Urgency

The urgency of management often depends on the size of the colon and the rate of change of the cecal diameter. Some experts believe that regardless of the criteria used for defining acute megacolon, the diameter of the cecum is the most important criterion because the cecum is generally the area that perforates. While the diameter at which the cecum perforates is variable, expert experience indicates that the cecum rarely perforates at a diameter of less than 12 cm.

Once acute megacolon (acute colonic pseudoobstruction [ACPO], Ogilvie syndrome) is relieved, close follow-up care, including physical examination and maintenance of a normal electrolyte balance, is important.

The use of polyethylene glycol electrolyte balanced solution can decrease the risk of recurrence.

Avoid using agents that slow transit time, such as opiates and anticholinergics.

Diet and activity

Most patients are in the hospital when acute pseudoobstruction is diagnosed, and bowel rest should be instituted. Parenteral nutrition may be considered depending on the patient's nutritional status.

Because many of the cases of acute pseudoobstruction occur postoperatively, the patients tend to be already at bed rest. Remembering to continue prophylaxis for deep venous thrombosis, per the individual physician's protocol, is important; however, if the patient is not severely ill, is not in severe pain, and is stable to ambulate, no reason exists for the patient to remain in bed.

In view of the high rate of recurrence of colonic dilation following medical and endoscopic therapies, other therapeutic modalities have been proposed for acute colonic pseudoobstruction (acute megacolon, Ogilvie syndrome).

Percutaneous cecostomy may successfully allow for colonic decompression, but complications with this procedure are high.

Surgical options include cecostomy, colostomy, or colectomy, although surgical therapies are associated with even poorer outcomes. A colectomy is indicated if perforation or colonic ischemia is present. ^{[26, 27, 28, 29]}