Diet and Drugs in Colorectal Surgery ( Part 2 )

Saturday, July 7, 2012

Am 5

Editors: Corman, Marvin L.

Title: Colon and Rectal Surgery, 5th Edition

Copyright ©2005 Lippincott Williams & Wilkins

Diarrhea

Diarrhea is a common complaint in numerous disorders, most of which are not attributable to colonic sources. A host of etiologic factors may produce an increase in stool water or stool frequency, including medications, infection, the consequences of radiation, hepatic or biliary disease, pancreatic insufficiency, intolerance to ingested food components, infiltration of the mucosa or submucosa with lymphocytes or eosinophils, neoplasm, inflammatory bowel disease, and IBS. It is beyond the scope of this chapter to offer a comprehensive discussion on the etiology and treatment of all the possible conditions that can lead to the symptom of diarrhea.

The most common presentation is that of increased stool water. This leads to loose stools, watery stools, and increased stool volume and/or frequency. The maximum number of bowel movements that is still considered within normal range is three per day, assuming that this does not represent a change in the individual's normal bowel habits. By definition, diarrhea is classified as acute until symptoms have been present for more than 6 weeks. After this time, it is considered chronic.

Acute Diarrhea

Acute diarrhea is often caused by medication or an infectious process, including bacterial enteritis, toxin ingestion, and infestation by the common intestinal parasites (e.g., Giardia, Cryptosporidium, Isospora). A discussion of the infectious and noninfectious colitidies can be found in Chapter 33. The use of broad-spectrum antibiotics with resultant infection by Clostridium difficile is a frequent source of acute diarrheal illness (see also Chapter 33).

Principles of Management

Treatment for acute diarrhea involves identification of the offending agent and initiation of whatever specific measures are necessary to eliminate the source or eradicate the organism. The use of medications that decrease gastrointestinal motility in acute, febrile diarrheal illnesses should be avoided, because prolonged contact time can enhance the likelihood of transmucosal migration of the organism and systemic infection. A better alternative is the use of pectin or bismuth compounds, such as kaolin-pectin or bismuth subcitrate. These products bind shiga toxins and other cyclic guanosine monophosphate–stimulatory toxins associated with bacterial infection and decrease the net water and chloride secretion by the small bowel. If systemic signs and symptoms of infection are not present, the use of opiates to increase transit time and slow stool frequency offers symptomatic relief. By prolonging contact time with the intestinal tract, fluid and electrolyte absorption will be enhanced.

Chronic Diarrhea

Chronic diarrheal illnesses may be caused by a wide variety of disorders that affect the hepatobiliary system, pancreas, and small or large bowel. Individuals with chronic diarrhea present a challenge in differential diagnosis. This inevitably may lead to an extensive and expensive workup. Assuming that such an evaluation fails to establish a specific cause for the patient's symptoms, the most likely disorder is the so-called IBS. Treatment for this complaint is to reduce the volume and frequency of bowel movements, so that the patient's lifestyle can be improved.

Treatment

The approach to the management of patients with chronic diarrhea without a definable cause begins with a carefully taken dietary history. An offending food or substance may be found in the patient's intake that increases the frequency of bowel action. For example, lactose-containing diary products may induce symptoms of cramping or diarrhea in up to 65% of the adult population. Furthermore, caffeine-containing beverages may increase bowel activity and stool output. Additionally, sugarless candies, sodas, and fruits high in fructose or sorbitol may lead to symptoms of diarrhea. Therefore, removing the offending agent will usually improve symptoms.

Medical therapy encompasses a wide number of options. The following discussion focuses on those agents used specifically to treat diarrhea.

The fiber-containing bulk agents previously alluded to decrease stool water when they are given with less than the recommended volume of liquid. Any of the bulk agents taken under these circumstances decreases the absorption of water through the gastrointestinal tract. However, there are the side effects of bloating, gas, and cramping. Another means for binding stool water is through the use of bile salt resins, such as cholestyramine. Bile salt resins are the preferred drugs for the management of diarrhea associates with ileal resection.

Kaolin, a dehydrated aluminum silicate, and pectin, a carbohydrate (polygalacturonic acid), can also be used as adsorbents to treat diarrhea. Bismuth subcitrate may also be employed to bind stool water and ameliorate diarrheal symptoms, but these agents are less effective than are the opiates. The most efficacious use of these products may be to prevent or to treat traveler's diarrhea.

The opiates are the most effective form of therapy in the management of diarrheal illnesses. These are usually given in the form of diphenoxylate or loperamide, but they are available in many other substances, including codeine phosphate and tincture of opium (paregoric). Opiates are habit-forming, but this risk is much less when they are taken orally. Still, loperamide, which fails to cross the blood-brain barrier, should be the initial choice. Studies have shown it to be comparable to diphenoxylate (Lomotil), which can cause euphoria in high doses. A patient whose diarrhea fails to resolve with the foregoing measures requires further evaluation.

Irritable Bowel Syndrome

IBS is defined as abdominal pain with or without alterations in bowel habits and with no evidence of abnormality on diagnostic testing. Patients may present with a wide variety of complaints, but more than 90% will have two or more of the following: visible abdominal distension, increased frequency of bowel movements with the onset of pain, looser stools with the onset of pain, and relief of pain with defecation.24 Most individuals typically complain of crampy, diffuse abdominal pains that are associated with alternating constipation and diarrhea. A consensus conference led to the publishing of the “Rome II” criteria for establishing the diagnosis of IBS.11 These include 12 weeks or more of abdominal discomfort within the preceding 12 months or pain that consists of two out of three features:

  • Discomfort relieved by defecation

  • Onset associated with a change in frequency of stools

  • Onset associated with a change in stool form (appearance)

The 12 weeks do not need to be consecutive. One assumes that evaluation for other disorders is negative.

Etiology and Pathogenesis

The etiology of IBS is unknown. However, there is considerable evidence to implicate the roles of stress and psychiatric illness in the pathogenesis of this condition. Various psychiatric abnormalities can be seen in the majority of individuals with IBS. In 85% of these, psychiatric symptoms either preceded or occurred coincidentally with the onset of the abdominal complaints.8,19,41 The condition is clearly associated with stress and emotional disturbances. Individuals frequently report exacerbation of their symptoms under these conditions. It has been shown that persons with IBS have a higher incidence of psychiatric illness when compared with those who do not or with those harboring other gastrointestinal disorders.43 Finally, there is emerging evidence to suggest that a history of physical or sexual abuse may be associated with IBS.12,42

Numerous abnormalities have been implicated in the pathogenesis of IBS. Patients with this condition have been demonstrated to exhibit altered colonic motility in response to meals when compared with subjects without IBS. Balloon distension studies suggest that these individuals have an increased rectal sensitivity to pressure.27 Further studies of the myoelectrical activity of the bowel suggest that approximately 40% of patients have abnormalities or alterations. For example, a decrease is observed in the normal six cycles per minute of basic electrical rhythm to three cycles per minute. This decrease may persist despite treatment that effectively controls IBS symptoms.37 Discomfort following distension of the ileum and the rectum is also increased in patients with IBS when compared with controls.21,44 It is interesting that the perception of pain does not appear to be increased elsewhere in the body.

Treatment

The lack of a definable abnormality in patients with IBS contributes to our inability to correct the patients' symptoms in a uniformly effective manner. For the most part, IBS is a lifelong illness, with periods of health punctuated by episodes of symptoms. The approach to management begins with evaluation of the potential contributing factors, primarily emotional and dietary. If the patient's emotional or psychological history is probed in a careful and sensitive manner, the physician can often identify a source for the discomfort for which the patient has been unaware.

The use of psychiatric therapy in this condition has been the subject of numerous studies. Hypnotherapy, stress reduction psychotherapy, dynamic psychotherapy, and relaxation techniques have all been successfully employed. Unfortunately, when one reviews these approaches, there is a consensus that the trials are plagued with poor methodology. As a consequence, there is no general acceptance of any specific technique.39 Still, these studies do suggest a role for psychotherapy for those who are willing to consider this approach to treatment.

There is no doubt that dietary factors can play a role in IBS and lead to increased abdominal cramping or pain. Patients with diarrhea should be counseled with respect to foods that are likely to increase stool water and frequency. These include fiber, nonabsorbed carbohydrates, caffeine, and lactose. If constipation is the primary symptom, increased fiber and water intake may help reduce the difficulty in passing stools, but the consequences of bloating, cramps, and abdominal pain may make the use of this approach counterproductive.

For the majority of patients, crampy abdominal pain is the major reason for seeking medical care. The pain is often difficult to characterize but is usually diffuse, intermittent, and frequently localized to the left lower quadrant of the abdomen. The pain may be exacerbated by meals and relieved somewhat by defecation or the passage of flatus. Because the regulation of bowel movements may offer some relief from the discomfort, it should be part of the treatment for all patients with IBS. Although elimination of pain may not be successfully accomplished in everyone, a graduated approach provides the best chance of alleviating symptoms.

The current first line of medications is the anticholinergic class of drugs.34 Anticholinergics can reduce the rate of spike activity, thereby decreasing tonic contractions in the colon. This may lead to decreased cramping and bloating. Anticholinergics may be administered alone or in combination with other sedative/hypnotic medications, such as atropine, scopolamine, hyoscyamine, and phenobarbital in combination (Donnatal) and a combination of clinidium and chlordiazepoxide (Librax). The addition of these drugs may also be useful for those patients in whom anxiety contributes to the symptoms. Short-acting anticholinergics can be administered sublingually or orally and can be used to suppress symptoms when they occur. Long-acting preparations may be helpful for the management of chronic symptoms.

Antidepressants have also been shown to provide relief from the pain of IBS, often at doses far lower than those used to achieve an antidepressant effect. Furthermore, this is seen at doses at which the anticholinergic effects are negligible. Imipramine, amitriptyline, or nortriptyline given at a starting dose of 10 mg at bedtime, will often reduce or eliminate the abdominal pain associated with IBS. The dose can be increased, but at higher doses side effects are common. One side effect of the tricyclic class of antidepressants is constipation. Of course, this may help in those individuals who have diarrhea as a major component of their IBS, but it will certainly exacerbate symptoms for those whose primary complaint is constipation. In this latter group of patients, one may address this concern by switching to the selective serotonin reuptake inhibitors (SSRIs): fluoxetine (Prozac), paroxetine (Paxil), or sertraline (Zoloft), again at low doses. Although the SSRIs are less likely to be associated with constipation as a side effect, diarrhea may be aggravated. One must appreciate the importance of titration of the various medication choices in trying to identify the appropriate approach to the management of a given individual.

Various other medications have been used to treat the symptoms of IBS, but the data are preliminary, and the studies have been undertaken with only small groups of selected individuals.23 Fedotozine, a gut κ receptor agonist, appears to decrease visceral sensitivity in animals. One study suggested improvement in the symptoms of bloating and abdominal pain when this drug was given during a 6-week trial.9 Leuprolide, a gonadotropin-releasing hormone agonist, has been demonstrated to improve the symptoms of nausea, vomiting, bloating, abdominal pain, and early satiety in a group of women with functional gastrointestinal symptoms.26 Octreotide has also been shown to improve the visceral perception of pain in patients with IBS without affecting the small intestinal muscle tone.5,17 Cholecystokinin analogues have been demonstrated to offer some relief from the discomfort of IBS, but they are currently unavailable for use in the United States. Cromolyn sulfate has been shown in one study to improve the symptoms of IBS.38 Patients were selected for diarrhea-predominant IBS, and the drug was compared with an elimination diet. Both groups showed similar improvement. In addition, and as mentioned previously, tegaserod, a 5-HT4 agonist, may be useful for patients with constipation-predominant IBS.

NSAIDs appear to have little role in the treatment of the pain of IBS, and there is absolutely no place for stronger pain medications such as opiates or narcotics. Obviously, it is essential to avoid potentially addictive psychotropic medications in those individuals whose disease state often has such a strong emotional component.

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Continue to Part 3…

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