Gastroenterology and Hepatology Board Review: Pearls of Wisdom, Third Edition
Section V LARGE INTESTINE
CHAPTER 26. Large Intestinal Motility Disorders
Edy E. Soffer, MD and Claudia P. Sanmiguel, MD
What segments of the colon are usually involved in volvulus?
Sigmoid volvulus accounts for up to 70% of all cases of colonic volvulus followed by the cecum.
How helpful are abdominal x-rays in making the diagnosis of colonic volvulus?
Classic radiological features of sigmoid or cecal volvulus are observed in approximately 50% of patients. Water-soluble enemas and computed tomography scans are indicated when the diagnosis is unclear.
How effective is endoscopic decompression in the management of colonic volvulus?
Flexible sigmoidoscopy and rectal decompression tube placement for sigmoid volvulus is effective in 60%–80% of cases. In the case of cecal volvulus, nonoperative decompression is usually not successful.
What is the recurrence rate of colonic volvulus after endoscopic decompression?
Sigmoid volvulus recurs in approximately 50%. Therefore, surgical correction is often subsequently performed on an elective basis. Primary surgical correction of cecal volvulus is the treatment of choice.
True/False: Hirschprung’s disease may occur in adults.
True. Hirschprung’s disease may be diagnosed in young adults. Diagnosis should be suspected in patients who have history of constipation dating back to early childhood.
True/False: Anorectal manometry can exclude Hirschprung’s disease.
True. The presence of a rectoanal inhibitory reflex (RAIR)—reflex relaxation of the anal sphincter with distention of the rectum—excludes Hirschprung’s disease. In contrast, the absence of the RAIR does not necessarily prove the diagnosis of Hirschsprung’s disease.
True/False: A full thickness colon biopsy is always needed to confirm the diagnosis of Hirschsprung’s disease.
False. Rectal mucosal biopsy using either a large forceps or suction biopsy technique is the first step. If taken from the appropriate segment of the rectum and ganglion cells are present in the submucosa, Hirschprung’s disease is excluded. The absence of ganglion cells using these techniques, on the other hand, requires a full thickness biopsy to establish a diagnosis.
What are the predisposing factors for acute colonic pseudo-obstruction?
This condition is typically seen in the elderly following trauma or recovery from surgery, particularly, orthopedic, obstetric, or abdominal surgery. It can also occur in the setting of any severe medical illness.
What is the most effective drug therapy for acute colonic pseudo-obstruction?
Neostigmine, 2 mg given intravenously by slow push, achieves rapid decompression in most patients.
What are potential complications of intravenous neostigmine use in acute colonic pseudo-obstruction?
The most common adverse effect is mild to moderate crampy abdominal pain. Excessive salivation and vomiting may also occur. Symptomatic bradycardia requiring atropine is possible and cardiac monitoring should be in place. Bronchospasm and hypotension have also been reported.
When should colonoscopic decompression be attempted in the management of acute colonic pseudo-obstruction?
In a patient without evidence of compromised bowel (eg, peritonitis, pneumoperitoneum), if initial measures such as nasogastric decompression, discontinuation of narcotics/anticholinergic medications, correction of electrolytes and hypoxemia, and pharmacological therapy are unsuccessful, colonoscopic decompression should be attempted. Standard recommendations suggest colonoscopy when the diameter of the cecum is greater than 11 or 12 cm. A colonic decompression tube may be left in place, although its utility remains debatable.
True/False: A gender difference exists in the irritable bowel syndrome (IBS).
True. IBS is twice as common in females.
What pharmacologic therapy has recently been shown to induce a sustained effect in IBS?
Antibiotics. A recent study has shown that a short course of treatment with an antibiotic (rifaximin) resulted in sustained improvement (over 12 weeks) in patients with diarrhea-predominant IBS. This differs from other therapies for IBS which tend to lose their effectiveness shortly after their discontinuation.
True/False: IBS is associated with other gastrointestinal symptoms and nongastrointestinal conditions.
True. Upper gastrointestinal symptoms such as heartburn, nausea, and vomiting are reported in up to 50% of patients with IBS. Urinary symptoms, dyspareunia, headaches, and fibromylagia are also more common in patients with IBS compared to patients with organic gastrointestinal diseases.
True/False: IBS is associated with an identifiable gut motor abnormality.
False. While a number of motor changes have been described in patients with IBS, no pathognomonic gastrointestinal motor abnormality has been defined thus far.
Which laxatives are associated with melanosis coli?
Anthranoid laxatives such as senna, cascara, and aloe. However, up to 30% of patients found to have melanosis coli during colonoscopy do not have history of laxative use—many of these are using herbal supplements that contain anthranoid derivatives.
Where in the gut is melanosis seen?
Melanosis can be seen throughout the colon; however, the proximal colon is usually more affected.
True/False: Melanosis coli is a risk factor for colon cancer.
False. Although melanosis coli has been associated with increased cellular apoptosis, no studies have shown an association between colon cancer and melanosis coli.
What is the most common reason for fecal incontinence in children and institutionalized elderly?
Fecal retention resulting in overflow soiling.
What is the most common etiology of constipation?
What subtypes are included in idiopathic constipation?
IBS, dyssynergic defecation, and slow transit constipation.
What is dyssynergic defecation?
In this condition, also referred to as anismus, pelvic floor dysfunction, or obstructed defecation, there is a paradoxical contraction rather than relaxation of the external anal sphincter and puborectalis in response to defecation.
How is dyssynergic defecation diagnosed?
Several tests are available. The more of these tests that are abnormal, the stronger the diagnosis. Digital exam of the anal canal may show contraction of the sphincter apparatus rather than relaxation when the patient is asked to bear down. Anorectal manometry and electromyography may show contraction rather than relaxation of the muscles during attempted defecation. Balloon expulsion test may demonstrate difficulty expelling the balloon from the rectum (ie, prolonged time or inability to expel the balloon). Finally, evacuation proctography (defecography) may demonstrate anorectal angle narrowing rather than widening during attempted defecation.
What is the most appropriate treatment for this condition?
Recent controlled trials have shown that pelvic floor retraining (biofeedback) is superior to laxatives and achieves up to 80% improvement (at least over the short term).
What medications can cause or aggravate constipation?
Opiate derivatives, anticholinergics, calcium- or aluminum-containing antacids, calcium channel antagonists, and clonidine are a few.
True/False: Surgery is indicated if both a rectocele and difficult evacuation are present.
False. Rectoceles are common, even in nonconstipated women. A history of applying digital pressure on the posterior wall of the vagina to help evacuation and a defecogram showing a large rectocele with residual barium at the end of defecation suggest that surgical repair may be helpful.
True/False: Surgery is often helpful in the management of dyssynergic defecation.
False. Operations such as division of the internal anal sphincter and puborectalis are usually not successful and may result in fecal incontinence.
True/False: Botulinum toxin injection into the puborectalis is of proven benefit in the management of dyssynergic defecation.
False. Although ultrasound-guided injection of botulinum toxin into the puborectalis has been reported to improve defecatory complaints in a small, open-label study, experience is limited and repeated injections may be needed.
How is colonic transit measured in clinical practice?
Transit study by radio-opaque markers is the most common method used. Radionuclide scintigraphic colon transit testing is also available but mainly in referral centers. A wireless motility capsule has also recently been approved for clinical use for this purpose but is not widely available at present.
When should the use of a colon transit study be considered?
In patients with severe intractable constipation. A normal colonic transit in such patients is associated with a higher prevalence of psychological distress when compared to patients with slow transit.
True/False: Exercise is helpful in the treatment of constipation.
False. While constipation is associated with inactivity, there are no convincing data to suggest that, in active subjects, bowel habits are affected by exercise.
What is the recommended daily dose of fiber per day?
Between 20 and 30 grams.
True/False: Fiber is effective in patients with severe constipation.
False. Fiber comes from different sources and its effect on colonic transit is variable. All patients with constipation should have an appropriate amount of fiber in their diet; however, while patients with mild constipation may improve with additional fiber, those with significant slow transit constipation can experience bloating and distension.
What are the potential complications of mineral oil?
Lipoid pneumonia, if aspirated. It can also cause anal seepage and there is a potential risk of malabsorption of fat soluble vitamins when used long term.
How do stimulant laxatives work?
Both anthranoid laxatives, such as senna and aloe, and the diphenylmethanes, such as phenolphthalein and bisacodyl, act by increasing colonic motility and by inducing secretion. Phenolphthalein compounds have been withdrawn from the market.
How do osmotic laxatives work?
Osmotic laxatives contain poorly absorbable ions, such as magnesium, and increase water content in the colon.
True/False: Hypermagnesemia is a potential side effect of osmotic laxative use.
True. This is mainly of concern only in those with renal insufficiency.
True/False: Polyethylene glycol solution is useful in the management of chronic constipation.
True. Polyethylene glycol is a nonabsorbable electrolyte solution. While normally given for bowel cleansing prior to colonoscopy, when taken in smaller amounts (250–750 ml per day), it can be extremely helpful in the treatment of chronic constipation in both children and adults.
True/False: Lubiprostone, approved for the treatment of both chronic constipation and constipation-predominant IBS, selectively activates type 2 chloride channels in the apical membrane of intestinal epithelial cells, thereby stimulating chloride secretion along with passive secretion of sodium and water, and inducing peristalsis and laxation.
True, although the exact mechanism of action of this drug remains unclear.
What is the most common operation for patients with severe constipation and slow colonic transit?
Subtotal colectomy with ileorectal anastomosis. Segmental colon resections in patients with severe slow transit constipation should be avoided.
True/False: Prior to consideration of surgery for refractory slow transit constipation, an evaluation to exclude a more diffuse gut dysmotility syndrome (intestinal pseudo-obstruction) should be performed.
True. The presence of diffuse gut dysmotilty predicts a less than optimal response to surgical removal of the colon. Gastric emptying test and intestinal manometry should be considered prior to surgery.
How does narcotic use induce constipation?
Constipation is frequently seen in patients using narcotics. There are several mechanisms involved in the development of constipation including increased anal sphincter tone, decreased peristalsis, increased water and electrolyte absorption, and impaired defecation response.
True/False: Polyethylene glycol is more effective than lactulose for the treatment of narcotic associated constipation.
False. A randomized, double-blind, crossover study showed no significant difference in effectiveness between these two medications.
True/False: Methylnaltrexone, used for treating severe narcotic-induced constipation in the palliative care setting, is safe and effective and does not interfere with pain control.
True. Several studies have shown that up to half of the patients who received methylnaltrexone experienced laxation within 4 hours of the initial dose. There were no significant side effects and there were no signs of opioid withdrawal or changes in pain scores during treatment.
What is narcotic bowel syndrome?
Narcotic bowel syndrome (NBS) is an opioid-induced bowel dysfunction that is characterized by chronic or frequently recurring abdominal pain that worsens with continued or escalating dosages of narcotics. This syndrome is frequently under-recognized. Narcotic bowel syndrome can occur in patients with no prior gastrointestinal disorder, patients with functional GI disorders, or patients with other chronic gastrointestinal diseases who receive narcotics for pain control.
True/False: Amyloidosis affects the colon more frequently than other gastrointestinal segments.
False. The small bowel is most frequently affected by amyloidosis. Macroglosia is almost pathognomonic but is seen only in 10%–23% of the patients with systemic immunoglobulin light chain (AL) amyloidosis.
• • • SUGGESTED READINGS • • •
Rao SS. Constipation: evaluation and treatment of colonic and anorectal motility disorders. Gastrointest Endosc Clin N Am. 2009 Jan;19(1):117-139.
Bharucha AE. Treatment of severe and intractable constipation. Curr Treat Options Gastroenterol. 2004 Aug;7(4):291-298.
Lembo A, Camilleri M. Chronic constipation. N Engl J Med. 2003 Oct 2;349(14):1360-1368.