Hospital Medicine

Obstipation/Constipation

Constipation

I. Problem/Condition.

Constipation is a common problem for people of all ages, however, the incidence increases with age. One-third of adults over the age of 60 years old are constipated and laxatives are the highest selling over the counter medication amounting to several hundred million dollars a year.

Constipation alone is responsible for 92,000 hospitalizations per year. However, even in patients not prone toward constipation, the hospital environment can result in disordered bowel function secondary to decreased mobility, decreased oral intake and access to food, surgery, severe medical disorders and new medications.

In hospitalized patients, constipation presents as decreased stool frequency and sometimes as illeus or pseudo-obstruction. The problem is frequently brought to the attention of physicians by nurses, although the patient may also complain of abdominal distention, abdominal pain, decreased stool or painful defecation.

Although the ROME III criteria have been used in research, a more colloquial definition of constipation includes the following: infrequent bowel movements (typically three times or fewer per week), difficulty during defecation (straining during more than 25% of bowel movements or a subjective sensation of hard stools), or the sensation of incomplete bowel evacuation.

II. Diagnostic Approach.

A. What is the differential diagnosis for this problem?

Mechanical abnormalities: Colorectal cancer, bowel obstruction, hemorrhoids (can mimic/contribute to the pain), rectocele, colonic stricture, external compression from other source

Medication related: Opiates, Tricyclic antidepressants, Iron supplements, Anticholinergics, Calcium channel blockers, Clonidine, Anti-Parkinson’s drugs, Antipsychotics, Antacids containing Calcium and Aluminum, Calcium supplements, Antihistamines, Diuretics (furosemide and hydrochlorothiazide), Anticonvulsants, Bile acid resins, Laxative abuse

Endocrine: hypothyroidism, diabetes mellitus, hyperparathyroidism

Metabolic: Hypercalcemia, hypokalemia, uremia, heavy metal poisoning

Neurologic:

  • Peripheral: autonomic neuropathy, Hirschprung disease

  • Central: Spinal cord compression, Parkinson’s disease, dementia, Multiple Sclerosis, stroke

Myopathic disorders: Scleroderma, amyloidosis, sarcoidosis

Lifestyle factors: Inactivity, decreased food and fluid intake, low fiber diet, inaccessible toilet facilities, positioning (harder to defecate in supine position in bed)

Psychological conditions: Depression, anxiety, confusion

Functional constipation: Absence of identifiable secondary causes

B. Describe a diagnostic approach/method to the patient with this problem.

If the presentation of an acute abdomen is associated with constipation, imaging should be completed urgently. Otherwise, start with a thorough history including evaluation of red flags for malignancy, time course, stool consistency, dietary history, past medical history, laxative use, as well as personal and family history of inflammatory bowel disease (IBD) or malignancy. Next, a physical exam with special attention paid to the abdominal exam, rectal exam, vaginal exam should be included if indicated.

1. Historical information important in the diagnosis of this problem.

Screen for warning signs of malignancy or IBD: bleeding, weight loss, change in stool caliber, new constipation, fevers, anorexia, family history of colon cancer or IBD.

Stool history: frequency, consistency, size, complete emptying

Defecation assessment: degree of straining, history of ignoring a call to go (leads to fecal impaction), need to hold perineum up to have bowel movement

Dietary history: amount of fiber and water

Past medical history: specific attention to diseases above especially endocrine and metabolic disorders

Medication list: Full medication history including any over the counter medications including laxatives, anti-spasmodics, antihistamines.

Social history: emphasis on living situation, ability to perform activity of daily living

2. Physical Examination maneuvers that are likely to be useful in diagnosing the cause of this problem.

Rectal exam (should be performed in all patients with constipation as presenting complaint unless other obvious source found in history):

  • Visual exam (for scars, fissures, fistulas, hemorrhoids)

  • Observe patient straining for possible rectal prolapse or prolapsed hemorrhoid.

  • Neurologic exam: check for anal wink, loss of reflex can point to neuropathy. Check for sensation.

  • Digital exam (for fecal impaction, anal stricture or masses palpable, rectal tone, masses, stool in vault, blood in stool). While finger in vault can also assess for sphincter relaxation by asking the patient to bear down.

  • Consider vaginal exam to evaluate for rectocele.

3. Laboratory, radiographic and other tests that are likely to be useful in diagnosing the cause of this problem.

Lab evaluation should depend on the history and physical exam as above. Labs are not necessary if obvious cause found previously. Otherwise consider serum chemistry for electrolyte abnormalities (potassium and calcium) and renal function, and thyroid stimulating hormone.

Radiography: Abdominal X-ray should be the initial imaging study ordered if no clear source found from work-up above or any red-flag symptoms or signs. It can reveal ileus, small bowel obstruction, volvulus, foreign bodies and assess for stool volume.

Consider Gastroenterology consult for diagnostic endoscopy if any concerns for Inflammatory Bowel Disease or malignancy.

C. Criteria for Diagnosing Each Diagnosis in the Method Above.

Mechanical: Patients with a history of vomiting, rebound or guarding on abdominal exam, markedly distended abdomen, or decreased bowel sounds may have a bowel obstruction.Patients with an abnormal rectal exam (hemorrhoids, rectal prolapse, etc) suggests a source but may still need evaluation for other primary sources of constipation. Patients with structural causes of obstructions (stricture, etc) will often have an abnormal Abdominal X-ray.

Medication related constipation is a diagnosis of exclusion. It can be made by history and chart review, and any offending medications will likely be contributing even if other causes are identified. If a patient has an eating disorder, laxative abuse should be asked about specifically.

Metabolic abnormalities will be evident on lab testing and possibly on history and physical exam (hypercalcemia).

Endocrine abnormalities may be found on history, physical exam, or laboratory testing.

Central Nervous causes of constipation will likely be found on physical exam through decreased sensation in the perineal area or abnormal rectal tone. Depending on the situation it should be evaluated by magnetic resonance imaging or other imaging studies and would likely warrant a Neurosurgical or Neurological consult.

Peripheral nervous system causes of constipation may be more difficult to diagnose and may be diagnosed by careful history and/or through diagnosis of exclusion. Hirschprung disease most often presents in infants or young children as chronic constipation and is diagnosed by rectal biopsy.

Myopathic disorders: Scleroderma requires consistent clinical features, including skin thickening either limited or diffuse; in the setting of limited disease, the patient will typically have Raynaud’s phenomenon, telangectasias, esophageal disease, positive antinuclear antibody (ANA) and anti-centromere or anti-scl-70 depending on limited versus diffuse disease. Constipation in the absence of other features will not be scleroderma. Amyloidosis requires biopsy for final diagnosis. If it is causing constipation, the patient is likely to have a known diagnosis, along with other manifestations of amyloidosis.

Lifestyle factors, including inactivity, poor food and fluid intake, low fiber diet, inaccessibility to toilet facilities, positioning (harder to defecate in supine position in bed), will all be identified by history taken either from the patient, or caregivers, as environmental factors disproportionately will affect the elderly and ill.

Psychological conditions can be difficult to assess. Depression, anxiety and delirium can make it difficult for patients to get themselves out of bed, and these patients are also often on medications that contribute to constipation. History and chart review will reveal these patients.

Functional constipation is a diagnosis of exclusion and requires thorough evaluation.

D. Over-utilized or “wasted” diagnostic tests associated with the evaluation of this problem.

Use X-ray and computed tomography (CT) judiciously.

III. Management while the Diagnostic Process is Proceeding.

A. Management of Clinical Problem Constipation.

Before initiating medications it is important to ensure there are no structural abnormalities or life-threatening conditions that require surgical treatment such as ischemic colitis and toxic megacolon.

If patient has hard stool on digital rectal exam, physical measures to remove the stool is indicated. This includes manual disimpaction and use of tap water enemas. If no fecal impaction is present, medication therapy is safe to start.

Increased fluid intake and mobility are often helpful but may not be possible for some patients. For patients on fiber-poor diets, the addition of fiber to their diet is a helpful long-term measure but in the short term, additional fiber can worsen the situation, causing a ’soft impaction.’ Fiber should be increased in the diet only after the acute crisis is over and patient is asymptomatic. Fiber can be added through increasing intake of fiber-rich foods or by using bulk agents. Fiber can be given through soluble fiber (fruit, vegetables, psyllium) which are better tolerated or insoluble fiber (wheat bran or whole grains) which can cause cramping in some people. Stool softeners such as Docusate (Colace®) are best used in patients with painful defecation from anal fissure and hemorrhoids but are not very effective alone for acute or chronic constipation. Other stool softeners include glycerin suppositories which can draw water into the rectum.

Laxatives can be broken into 4 groups:

  • Bulk agents as discussed above can increase the bulk of the stool and therefore increase stool water content. They are generally safe and well-tolerated but may not be very helpful in patients with acute constipation.

  • Osmotic nonabsorbed substances such as Polyethylene Glycol 3350 (Miralax®) increase stool water content by osmotic shifts thereby stimulating a bowel movement. Miralax® is flavorless and has been found to be the safest and easiest to tolerate of the osmotic laxatives. Magnesium containing osmotic laxatives such as Milk of Magnesium can be effective but alsocan be associated with electrolyte imbalance with derangement of magnesium and phosphate making them contraindicated in renal failure. Lactulose can be very effective but can be difficult to tolerate due to taste and often increased gas in the intestinal lumen.

  • Stimulant laxatives such as bisacodyl and senna increase intestinal motility decreasing time for reabsorption of luminal water. Before increasing motility, it is best to evacuate existing constipated stool with an enema or cramping can result. Initiate doses at one tab before bed and uptitrate to 4 tablets twice a day if needed. Bisacodyl can also be given as a suppository.

  • Secretory laxatives such as lubiprostone and linaclotide work by causing ions and water to move into the intestinal lumen. This results in accelerated transit and softening of the stool. They are prescription drugs that are most commonly used in patients with chronic idiopathic constipation related to irritable bowel syndrome.

Enemas may be the only way to break up hardened fecal matter and wash it out in the setting of fecal impaction. They should be avoided on a routine basis as they can wash out normal mucous and damage intestinal mucosa. In general, start with tap water enemas.

If constipation is opioid related and laxative and enema administration is unsuccessful, methylnaltrexone can be considered. Methylnaltrexone does not cross the blood-brain barrier. It is a selective antagonist of peripheral mu-opioid receptors, with resulting inhibition of gastrointestinal hypomotility without central nervous systems effect or reversal of analgesia. Methylnaltrexone is well-tolerated with the most common side effect of abdominal pain. Methylnaltrexone is substantially more expensive than other therapies, approximately $45 per dose compared with pennies for senna or docusate. It also must be given as a subcutaneous injection.

When treating a patient with constipation it is best to start with the best tolerated and least expensive medications first. It is reasonable to start with dietary fiber or a bulking agent and then move on to an osmotic laxative such as Miralax® and/or a stimulant laxative. One should discuss the regimen with the patient and set expectations.

Prevention is the best cure. All patients on narcotics or at high risk for developing constipation should be placed on a bowel regimen consisting of at least a stool softener and possibly scheduled Miralax®. There should also be consistent evaluation of patient bowel movements by asking the nurse and patient about number of bowel movements. It is also important to emphasize and promote healthy bowel habits such as attempting movement on awakening and 30 minutes after eating to take advantage of the gastrocolic reflex.

B. Common Pitfalls and Side-Effects of Management of this Clinical Problem.

Common pitfalls include:

  • Failure to diagnose structural problems, especially in patients unable to provide an adequate history

  • Overtreatment leading to excessive stool frequency and urgency

Pearls:

  • Increase fiber slowly over weeks to a month to decrease side effects such as gas, bloating, and distension, goal 20-25 grams per day.

  • Avoid soapsuds enemas as they can cause rectal mucosal damage.

  • Avoid sodium phosphate enemas and magnesium/phosphorus laxatives in renal failure.

  • Osmotic laxatives can take more time to work, for more immediate results a suppository can be very effective.

  • Prokinetic agents such as metoclopromide are of limited use.

IV. What’s the Evidence?

Shah, BJ, Rughwani, N, Rose, S. "In the clinic: Constipation". Annals of Internal Medicine. vol. 162. 2015. pp. ITC1.

Wald, A. "Constipation: Advances in diagnosis and treatment". JAMA. vol. 315. 2016. pp. 185.

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