Constipation is a common complaint of people with PD. Not having a daily bowel movement isn’t constipation, though; constipation is defined as two or fewer bowel movements per week. Defecating difficulty is defined as straining at, and incomplete evacuation of, stool. Constipation and defecating difficulty may or may not occur together, and affect up to 50% of PD patients. It is important to distinguish between constipation and defecating difficulty because their treatments differ.
Normally, the muscles of your large bowel (colon) propel stool forward. These muscles are controlled by signals from the vagus nerve through part of the ANS, which is affected in PD and sometimes causes the colon’s muscles not to fully contract. The pas-sage of stool through the colon then slows, causing the stool to remain in the colon longer, where it hardens and becomes difficult to expel by your rectal muscles. Medications prescribed for PD or other problems may also lead to constipation. For instance, drugs prescribed to regulate your bladder, blood pressure or heart rate all affect the ANS and thus may affect your bowels.
PD drugs such as tri-hexiphenidyl (Artane), benztropine (Cogentin), and amantadine (Symmetrel) block a chemical called acetylcholine, used as a messenger by the vagus nerve, and so these anti-acetylcholine (also called anticholinergic) drugs cause constipation. Similarly, drugs used to treat an overactive bladder (such as Detrol or Ditropan) are also anticholinergics and they too cause constipation. Conversely, drugs used to treat Alzheimer’s disease and Lewy body demen-tia (Aricept, Exelon, Razadyne) increase acetylcholine and may cause diarrhea. A common cause of constipation in people with and without PD is a diet low in fiber.
As your colon “transit time” (the time stool stays in your colon) slows, water is absorbed from your stool, making it hard. Fiber, in addition to cleansing your bowel, acts like sawdust, soaking up water, allowing it to remain in your stool and preventing your stool from drying out and becoming hard. Fiber can be soluble (dissolves easily) or insoluble (passes through the bowel largely unchanged). Americans eat an average of only 5–14 grams of fiber daily, which is short of the 20–35 grams recommended by the American Dietetic Association. Increased dietary fiber is an important first step to avoiding constipation. High-fiber foods include beans, bran, whole grains, and most fresh fruits and vegetables including apples, asparagus, bananas, cabbage, carrots and sprouts. Low fiber foods include cheese, ice cream, milk and most processed foods. Such foods should be avoided if you are constipated.
Water and fruit and vegetable juices add fluid to your bowels, bulk-up your stools and make them softer and easier to pass. Drinking at least six 8-ounce glasses of water or fruit/vegetable juice every day can relieve constipation. Caffeinated beverages such as coffee, cola, and tea, and alcoholic beverages, dry and harden your stools, making them more difficult to pass. Constipation is improved by exercise and aggravated by a lack of exercise. Thus, mobile patients are less likely to be constipated than are wheelchair- or bed-bound patients. An hour of exercise per day may do more to lessen constipation than a laxative. Constipation and the resultant straining can result in several complaints, such as hemorrhoids (dilated and enlarged rectal veins), anal fissures (tears in the skin around the anus), or rectal prolapse (a part of your intestines “popping out” of your rectum).
All of these conditions are painful, can bleed, are worrisome, and require prompt medical attention. In a small number of patients (about 5%), a combination of constipation and defecating difficulty results in fecal impaction: an inability to evacuate stool. The pain and discomfort from fecal impaction may be severe and require a visit to the Emergency Department. All of these conditions can be avoided by alleviating constipation. If you have recently become constipated, consult your doctor who may order tests to determine the cause.
In PD, defecating difficulty results from rigidity and/or slowness of contraction of both your abdominal muscles and your gluteal muscles (the muscles with which you sit on the toilet). To expel your stool you must increase the pressure in your abdomen, tightening both your abdominal and gluteal muscles. If you are out of shape, whether you have PD or not, you may be unable to effectively tighten the necessary muscles.
Add the rigidity and bradykinesia of PD to your de-conditioned muscles and you’ll have defecating difficulty despite a proper diet and potent laxatives. Exercising on a daily basis, and thus keeping your abdominal and gluteal muscles in shape, helps a lot. Patients who are taking levodopa/carbidopa or Stalevo should consider taking their first dose an hour before they are ready for a bowel movement, which will allow the effects of the medication to “kick in” and overcome the rigidity of their abdominal and gluteal muscles.
Though rare, in some PD patients the anal sphincter contracts when it should relax. This can be treated by manually relaxing the sphincter, and sometimes by the injection of Botox. If this occurs, avoid excessive straining. If you feel you cannot expel the stool in your rectum, it may help to sit straight up (rather than bend forward), thereby increasing the leverage of your abdominal muscles, allowing them to contract more forcibly. Some patients put a trapeze over their toilet and hold onto it with their hands as they push down with their abdominal muscles, increasing the leverage of those muscles and simultaneously straightening their spine. The following are additional treatments for constipation and defecating difficulty, arranged in order of their simplicity.
Bran: the outer coating or shell on grain which is removed during processing and found commonly in wheat, oats, and brown rice. One tablespoon of raw bran contains two grams of dietary fiber; start with 1–2 tbsp of bran in a glass daily and gradually increase to three times a day. If you have diverticulitis, ask your doctor if you can use bran. Depending on how long you’ve been constipated, improvement may take days to weeks. Psyllium: a naturally occurring dietary fiber made from the ground husks of the psyllium seed. Psyllium holds water and its use results in bulky, easy-to-pass stool. Metamucil is a popular brand of psyllium. Stool softeners: over-the-counter medications that moisten the stool, making it easier to pass. Laxatives: some PD patients need a laxative to help expel their stool. Each of the following laxatives works differently; some may work better for you than others. Before using a laxative or a combination of laxatives, speak to your doctor.
Stimulant laxatives increase the contractions of your colon. Dulcolax and Senokot are brand names for this type of laxative. Dulcolax can be taken as a pill or administered as a suppository. ? Mineral or osmotic laxatives act like “sponges,” drawing water into the colon, making it easier to pass stool. Milk of Magnesia, Miralax, and Lactulose are popular over-the-counter brands, all of which should have an effect within 12 to 24 hours.
These laxatives should be used only with your doc-tor’s knowledge and not for more than two weeks at a time. Over-usage may result in nausea, diarrhea, and possibly, electrolyte imbalances (excessive loss of sodium and/or potassium in the stool). Amitiza (lubiprostone) is a prescription drug that increases the secretion of water into the bowel via the chloride channel, allowing the stool to pass more easily.