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Newsletters: Despicable Diarrhea
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Courtesy of National Institute of Diabetes and Digestive and Kidney Diseases, NIH.

Darlene Kelly, MD, PhD


Just as Gru is one of the most despicable movie characters of 2010, diarrhea is one of the most despicable problems faced by consumers of home parenteral and enteral nutrition (HPEN). This was found in a quality of life study done by Marion Winkler, PhD, a member of the Oley Foundation Board of Trustees. Dr. Winkler conducted extensive interviews with HPEN consumers, who described diarrhea as "disastrous,” "degrading,” "restrictive,” and "immobilizing.”1


It is important to know that the causes of diarrhea are variable and depend largely on the structure and function of an individual’s intestine. In order for the person who has this despicable problem to overcome it, it is critical that he or she knows and understands what may be the underlying cause of it. Anyone who has undergone surgery to remove a segment(s) of intestine should be aware of what has been removed and how much of the intestine remains in place. Each part of the intestine (the duodenum, jejunum, ileum, and colon) has a specialized role. For those who have dysfunction of the intestine, an understanding of the type of problem is helpful in understanding what can be done to effectively treat resulting diarrhea. 


Short Bowel Syndrome

Short bowel, as defined by Medicare, is a residual small bowel length of 5 feet or less. However, the traditional dogma is that a small bowel length of less than 100 centimeters (39.37 inches—remember that meter stick in your classroom?) requires parenteral nutrition (PN). This assumes that the structure and function of the remaining intestine is normal. When the large intestine is preserved, an even shorter segment of small bowel may be sufficient to avoid PN or to taper off PN. If the large intestine is not preserved, and/or the remaining small bowel is not healthy, more than 100 centimeters may be necessary to avoid PN. 


Within a few months after a large segment of small intestine is removed, the remaining intestine begins to undergo "intestinal adaptation.” This means that the intestine increases in diameter and length, and the cells of the intestine get much more efficient at absorbing nutrients and fluid. Adaptation occurs over the first year or two after surgery. Consequently, as long as a good oral diet is consumed, the degree of diarrhea that is observed immediately post-operatively will decrease. This fact can hold promise to you, as you may initially feel you can never stray far from a bathroom. 


But you can do something besides just waiting for adaptation to be complete. The principle involved is osmosis. We all studied osmosis, sometime between fourth grade and eighth grade. Osmosis means water will travel from a low-density solution across a semi-permeable membrane—such as the wall of the intestine—to a higher-density solution, in order to equalize the density of the two. 

Basically, in food terms this means if you eat lots of sugars or extremely high-salt foods, water will move from the bloodstream into the small intestine in order to dilute out the effect of the sugar and salt. If you have an intact small and large intestine, the effect is very minimal, but for those with short bowel the diarrheal effect is huge. Consequently, those who drink sweet beverages (not the diet type) will lose more fluid from the blood (risking dehydration) and have very fluidy stools. By contrast, other carbohydrates (starch in the form of pastas, potatoes, rice, and breads) are digested more slowly and will cause less diarrhea and much thicker consistency stools. 


 Drinking large amounts of water can also cause excessive losses of fluids from the short bowel, especially when the colon (a major fluid absorber) has been removed. In fact, the volume that is lost can exceed the amount of water that was drunk. The absence of sodium (part of salt) in water causes sodium to move from the blood into the intestine, and where sodium goes, water follows. For this reason, people with short bowel who drink gallons of water will rapidly become dehydrated while spending huge amounts of time in the bathroom. Diet beverages have the same effect as water. If you have a short small intestine and a colon in place, the effect of "free water” is less severe.


The Fat Story 

In order to appreciate the effects of the presence of colon and distal ileum with short bowel syndrome, some understanding of normal fat absorption is necessary. Fat has different characteristics than water-soluble nutrients. If you look at a bottle of oil and water-based salad dressing, this difference can be seen: fat floats on top of the water-based solution. The same would be true in your intestine if special mechanisms for digestion and absorption were not involved.


When fat leaves the stomach and enters the small intestine, the pancreas releases fat-digesting enzymes (lipase and co-lipase) and the liver provides bile (which has multiple components, the most important of which are the bile salts). The bile salts are critical in making the fats in the oral diet soluble so they can be digested by the enzymes. The fats are absorbed in the jejunum and the bile salts are absorbed in the last part of the ileum. Mother Nature was the original recycler, as these bile salts are used again. The total amount of bile salts is critical, as it determines whether fats are absorbed normally. Consequently, the amount of ileum that has been removed is very important.


In the case where a large segment of ileum is removed, bile salts are absorbed poorly. This causes the body’s pool of bile to become depleted, making it difficult for the intestine to absorb fats. The malabsorbed fats enter the colon, where they are acted upon by the bacteria in the colon to form a product analogous to castor oil. The result is a very oily diarrhea. For those with colon in place, a low-fat diet will decrease this tendency. 

By contrast, when a small segment of ileum has been removed, the bile salt pool is maintained at normal levels by increased production in the liver. But in this case, some of the bile is poorly absorbed in the remainder of the small intestine, and the bile that enters the colon will have a secretory effect on the colon, causing watery diarrhea. In this case, some binding of bile may be helpful with respect to diarrhea, but this is not without complication since it will also decrease fat absorption. Your physician will need to assess the effects of bile-binding or other medications to determine what treatment is best for you.


The Role of Bacteria 

Normally bacteria are present in small numbers in the duodenum. There are less than 100,000 bacteria per 1/5 teaspoon. As you move into the jejunum and ileum, the numbers increase relative to the numbers in the duodenum. But beyond the ileocecal valve between the small bowel and colon, the numbers of bacteria skyrocket!


The valve keeps the colonic bacteria and contents of the colon from moving upstream. When the valve is removed, there is a tendency for the bacteria from the colon to enter the small bowel. The bacteria of the small bowel increase in number and become more typical of the bacteria that are normally only found in the colon (i.e., bacteroides). When these bacteria are in the small bowel, they impair digestion and unabsorbed carbohydrate produces gas (causing bloating and gas per rectum or ostomy).


These same bacteria use vitamin B12 from the diet, making it unavailable to your body and causing you to be depleted in the vitamin. The bacteria also interrupt the absorption of fats, which itself causes diarrhea (as discussed above). Finally, the bacteria affect the intestinal wall so that secretion of fluids occurs (diarrhea!). When the normal small intestinal bacteria increase in numbers and abnormal bacteria migrate from the colon into the small bowel, it’s called small intestinal bacterial overgrowth.


In intestinal dysmotility, bacterial overgrowth as described above can also occur, but the mechanism causing it is different. In this situation, overgrowth occurs because the flow of the intestinal content is slowed. I often describe this as being like the backwaters of a river, where the stagnant water becomes overgrown with algae. Although algae are not involved in the intestine, certainly bacterial numbers do increase.


Treatment of Bacterial Overgrowth   

Bacterial overgrowth is often treated by providing rotating antibiotics. This can be done with a number of different antibiotics. I prefer to use two to three different antibiotics, asking patients to take one antibiotic for a week, followed by one to three weeks without medication and then a week of a different antibiotic. We repeat this pattern as needed.  


It is quite possible that a specific antibiotic will not be beneficial and may need to be replaced with a different one. In my experience, we cannot predict the effectiveness of a given antibiotic for any individual. The reason for rotating different antibiotics and allowing time off antibiotics is to avoid having bacteria become resistant to an individual antibiotic. The break also allows the body to replace beneficial bacteria. This type of treatment must be monitored by your physician.


Another approach to bacterial overgrowth is to provide "good bacteria” in the form of probiotics or to encourage growth of good bacteria with prebiotics. "Prebiotics” are a type of food that helps to enhance normal intestinal bacteria. "Probiotic” is a dose of these healthy bacteria. This can be accomplished by using a form of good bacteria (especially lactobacillus) that can be found in some medications and in yogurt.


Anti-diarrheal Medications

These medications are helpful when taken in adequate amounts and when the timing is appropriate. Specifically, such medications as loperamide (Imodium) or diphenoxylate sodium/atropine (Lomotil) work by slowing movement of the liquid food (also called chyme) through the intestine. The amounts typically recommended on the label of the over-the-counter product are quite low and are intended for persons with an intact intestine and for use with intermittent diarrhea. The maximal amount for you should be recommended by your physician.  


Another important hint to maximize the effect of anti-diarrheals is to open the capsules or crush the tablets, then add the contents/powder to sugar-free applesauce or similar foods (this may improve absorption of the medication). Also, timing is truly everything! These medications should be taken about thirty minutes before eating in order to maximize their effects.



In summary, controlling despicable diarrhea may require limiting sweets and concentrated (or high osmolality) drinks (or diluting them); avoiding free water, coffee, tea, and diet pop and substituting constant sipping of electrolyte drinks; limiting fats if you have an incontinuity colon; and treating bacterial overgrowth. As you can see, your approach depends on your anatomy and intestinal function. At times everyone, whether they have an intact intestine or not, will experience some diarrhea, but this should not occur continually.


1. Winkler, Hagan, Wetle et al.  JPEN 34:395-407, 2010.
Dr. Kelly addressed this topic at Oley’s annual conference in July 2011. To see her slide presentation, click here.


LifelineLetter, July/August 2011


This website is an educational resource. It is not intended to provide medical advice or recommend a course of treatment. You should discuss all issues, ideas, suggestions, etc. with your clinician prior to use. Clinicians in a relevant field have reviewed the medical information; however, the Oley Foundation does not guarantee the accuracy of the information presented, and is not liable if information is incorrect or incomplete. If you have questions please contact Oley staff.


Updated in 2015 with a generous grant from Shire, Inc. 


This website was updated in 2015 with a generous grant from Shire, Inc. This website is an educational resource. It is not intended to provide medical advice or recommend a course of treatment. You should discuss all issues, ideas, suggestions, etc. with your clinician prior to use. Clinicians in a relevant field have reviewed the medical information; however, the Oley Foundation does not guarantee the accuracy of the information presented, and is not liable if information is incorrect or incomplete. If you have questions please contact Oley staff.
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