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Original Research

High-Fiber Diet for Treatment of Constipation in Women With Pelvic Floor Disorders

Shariati, Amir MD1; Maceda, Jose S. MD1; Hale, Douglass S. MD1

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doi: 10.1097/01.AOG.0000308660.48204.7f
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Chronic constipation has a reported nongender-specific prevalence of 2% to 27% in North America.1 The true prevalence is difficult to determine because the definitions for constipation, demographic factors, and sampling vary widely across studies. There is however, general agreement that the prevalence of constipation increases with age older than 65 years.2–4 The prevalence has been reported as high as 50–80% among long-term care facility residents.5–7 Most patients define constipation by hard stools, infrequent stools, extensive straining with bowel movements, a sense of incomplete emptying, and excessive time on the toilet.8 Therefore, asking about constipation without defining the specific symptom makes the term very nonspecific. The Rome II criteria were developed to assist the clinician in diagnosing functional constipation.9

Many different causes can contribute to constipation, including but not limited to systemic diseases, functional disorders, and mechanical obstruction. Systemic diseases can impair the bowel’s motor and sensory activity due to metabolic, endocrine, and neurologic disorders. Functional disorders such as bowel dysmotility syndromes, dementia, limited physical mobility, poor nutrition and hydration, and certain medications may also add to constipation. Some controversy still remains on whether pelvic organ prolapse (POP) contributes to constipation and its associated symptoms or whether constipation leads to POP. Outlet obstruction caused by POP, rectal prolapse, or neoplasm may furthermore contribute to constipation. Women with POP are at higher risk of constipation than those without POP.10 Straining and bowel frequency less than twice per week as a young adult has been reported as a risk factor for the onset of POP later in life.11 Prolonged defecatory straining efforts have also been shown to contribute to progressive neuropathy and dysfunction.12 This chronic straining may detract from a woman’s quality of life and is a dominant symptom in women with POP. In fact some patients report manually splinting a rectocele to achieve a bowel movement. This may be secondary to the rectocele or lack of relaxation of the pelvic floor muscles.

Dietary fiber has been advocated for improved bowel function since the early 1970s. There are two basic types of dietary fiber – soluble and insoluble. Soluble fiber (pectin, gums, and mucilages) is believed to be beneficial in lowering blood cholesterol and reducing plaque-forming low-density lipoprotein. Dietary fiber is generally 65% insoluble from cellulose, hemicellulose, and lignin. Insoluble fiber increases fecal volume and density by resisting digestion which leads to colonic distention and increases in intraluminal pressures triggering peristalsis, and increased water absorption which leads to more fecal bulk.13 The National Academy of Sciences Institute of Medicine recommends that female adults over 50 years have 20–25 g of fiber daily, however, most Western diets contain only 5–10 g per day.

Several different bowel assessment and rating scales exist; however, these are not specific to constipation. In this trial, we chose the Patient Assessment of Constipation Symptoms questionnaire. The primary objective of this study was to demonstrate the effect of optimal dietary fiber intake on symptoms of constipation as assessed by improvement in Rome II criteria scores in women who met Rome II criteria for constipation. A coprimary objective was to evaluate the treatment-related quality of life effect in this patient population as measured by the Patient Assessment of Constipation Symptoms questionnaire. Secondary objectives included changes in weekly stool frequency, laxative use, and vaginal and/or perineal splinting to facilitate defecation after maximizing dietary fiber.


A prospective cohort of consecutive women presenting between March 2005 and September 2005 to a tertiary care facility for pelvic floor disorders were eligible for study participation once Rome II criteria for constipation were met. Patients were considered constipated if they experienced two or more of the following symptoms for at least 12 weeks, which need not be consecutive, in the preceding 12 months9:

  1. Straining in more than 25% of defecations
  2. Lumpy or hard stools in more than 25% of defecations
  3. Sensation of incomplete evacuation in more than 25% of defecations
  4. Sensation of anorectal obstruction or blockade in more than 25% of defecations
  5. Manual maneuvers to facilitate more than 25% of defecations (eg, digital evacuation, support of the pelvic floor)
  6. Fewer than three defecations per week

Loose stools are not present, and there are insufficient criteria for irritable bowel syndrome.

Participants were excluded if they were not proficient enough in English to understand instructions and keep records for study purposes. They were also excluded if they had an allergy to fiber supplements, had undergone previous surgery on the small or large bowel, had an identifiable cause for constipation (metabolic, hypothyroid, etc), were unable to provide informed consent, or had a predicted geographic relocation in 3 months. Institutional review board approval was obtained, and each participant signed an informed consent form during her initial office visit.

Pelvic organ prolapse quantification stage was determined for each patient. The amounts of daily caffeine and water intake from their self-completed paper diary at baseline to the completion of the trial were recorded. The Patient Assessment of Constipation Symptoms questionnaire and Rome II criteria questions were administered by telephone interview by nursing staff on day 1 and on days 14, 28, and 42 after enrollment. The Patient Assessment of Constipation was developed to provide a brief, easily administered measurement tool for symptoms and quality of life aspects of constipation based on the patient’s experience of the disorder. It was developed as an outcomes instrument to evaluative research and assessment and designed to be valid and reliable for detecting change in clinical condition. Validation studies on younger adults showed that Patient Assessment of Constipation score change is related to changes in clinical condition.14 The Patient Assessment of Constipation was also shown to be easily administered and well understood by older adult residents in long-term care facilities and provides a valid and reliable method for obtaining constipation-specific symptom and quality of life data from this population.15 It consists of two separate scales, the Patient Assessment of Constipation Symptoms, a 12-item measure of symptom severity, and the Patient Assessment of Constipation Quality of Life, a 28 item measure of the health-related quality of life associated with constipation. The Patient Assessment of Constipation Symptoms evaluates the patient’s symptoms by answering “How severe have each of these symptoms been in the last week?” with a five-point Likert scale, 0 for absent, 1 for mild, 2 for moderate, 3 for severe, and 4 for very severe. The first four statements evaluate the abdominal symptoms by asking the above question as it relates to the following statements: discomfort in your abdomen; pain in your abdomen; bloating in your abdomen; and stomach cramps. The next four statements evaluate the bowel symptoms: painful bowel movements; rectal burning during or after a bowel movement; rectal bleeding or tearing during or after a bowel movement; and incomplete bowel movement, like you didn’t “finish.” The last four statements evaluate the stool symptoms: bowel movements are too hard; bowel movements are too soft; straining or squeezing to try to pass bowel movements; and feeling like you had to pass a bowel movement.

Each patient was given a box of high fiber cereal (14 g of fiber per one-half cup) and was instructed to supplement her diet with the cereal. Study participants ate one-quarter cup (7 g) of cereal daily for the first week and gradually increased this to one cup per day over 4 weeks, for a target optimal fiber intake of 28 g per day. Baseline fiber intake was unknown but it was assumed to be similar to fiber intake in most western diets (5–10 g per day). Participants recorded daily stool frequency, defecation requiring vaginal and/or perineal splinting, weekly laxative use, and daily caffeine and water intake on their paper diaries. Participants were encouraged to decrease caffeine intake and increase water intake to 60 ounces per day. Participants’ compliance was solely based on their report on telephone interviews. Daily caffeinated and noncaffeinated fluid intake and the number of weekly bowel movements, laxative use, and vaginal and/or perineal splinting were evaluated 42 days after the initiation of the high-fiber diet from daily diaries kept by the patients. Participants with adverse reactions, abdominal bloating or pain, and surgery during the study period were withdrawn from the trial. We assigned a score of zero if the patients had the aforementioned Rome II symptoms 0% of the time, 1 for 10% of the time, 2 for 25%, 3 for 50%, 4 for 75%, 5 for 90%, and 6 for 100% of the time to facilitate statistical analysis. Friedman’s test was used for all outcome measures including Rome II and Patient Assessment of Constipation Symptoms scores. Likewise, changes in outcome measures from baseline to 42 days follow-up were recorded and summarized by stage of prolapse. Changes within groups (patients with and without rectocele) were assessed using the Wilcoxon signed rank test, and comparisons between groups were performed using the Wilcoxon rank sum test.


Demographic data are shown in Table 1. Eighteen patients presented with a chief complaint of pelvic pressure or POP, 13 with urinary incontinence and frequency, eight with constipation, and two with fecal incontinence (streaking in undergarments). Twenty-five patients had previous surgery for prolapse, and two were using pessary for POP. Five had undergone suburethral slings for stress urinary incontinence.

Table 1
Table 1:
Patient Demographics (N=41)

Forty-one women enrolled in the study, and 30 completed all of the telephone interviews and home diaries. Six (15%) withdrew because they were unable to tolerate the fiber diet, three (7%) were withdrawn to have surgery during the study period, and two (5%) failed to respond to follow-up telephone interviews or did not return their diaries. Average Rome II scores for straining with bowel movements, lumpy or hard stool, sensation of incomplete emptying, and vaginal and/or perineal splinting improved during the study period from 3.54, 3.07, 3.2, 2.46, 1.73 to 2.0, 1.53, 1.67, 1.33, 0.6, respectively (P<.05; Fig. 1). Average weekly bowel movements increased from 3.6 to 4.0 (P<.01). The total, abdominal, rectal, and stool symptoms of the Patient Assessment of Constipation Symptoms improved from 1.66, 1.33, 1.22, 2.25 to 1.05, 0.86, 0.59, 1.5, respectively (P<.001; Fig. 2). The score changes were 0.61, 0.47, 0.63, and 0.75, respectively. Score changes of about one half a point correspond to minimal clinical improvement, and changes of about 1 point correspond to moderate clinical improvement.14 Daily average caffeine intake decreased from 30.5 oz to 9.1 oz, and water intake increased from 42 oz to 43 oz. Laxative use and vaginal and/or perineal splinting were decreased from 2.8 and 1.5 times per week to 1.4 and 0.67, respectively (P<.05; Fig. 3). Twenty-two of 30 patients who completed the study had a rectocele by definition, with the leading edge posteriorly more than –3. Statistical analysis between the patients with rectocele and those without a rectocele did not show any statistical significance in symptoms, and patients with a rectocele had more clinical improvement than those without a rectocele according to score changes on the Patient Assessment of Constipation Symptoms questionnaire (Table 2).

Fig. 1.Shariati. High-Fiber Diet for Treatment of Constipation. Obstet Gynecol 2008.
Fig. 2.Shariati. High-Fiber Diet for Treatment of Constipation. Obstet Gynecol 2008.
Fig. 3.Shariati. High-Fiber Diet for Treatment of Constipation. Obstet Gynecol 2008.
Table 2
Table 2:
Within- and Between-Group Evaluation of Patients With and Without Rectocele


Lack of dietary fiber intake is considered to be one of the most common causes of chronic constipation.16 In a case–control study, Arya et al10 showed that women with POP are at higher risk for constipation than controls. The increased risk for constipation was partially attributed to lower intake of dietary insoluble fiber by women with POP than controls. Therefore, for the patients in our study, we gradually increased the amount of dietary fiber intake during the study period to the amount recommended by the National Academy of Sciences Institute of Medicine. The participants gradually increased their fiber intake by 7 g weekly until they reached the dose of 28 g daily after 4 weeks. The gradual increase in fiber is of the utmost importance to improve the tolerability of this change in fiber intake (15% could not tolerate the diet). We encouraged our patients to increase their water intake and decrease their caffeine intake to facilitate fiber tolerability and function. There was no change in the water intake but the caffeine intake was decreased significantly, which may have confounded our findings.

It has been shown that women who strain for long periods of time have shown progressive neuropathy and pelvic floor dysfunction.12 Straining with bowel movements as a young adult has been associated with increased risk of POP later in life. Bowel movements less frequent than twice weekly were also shown to be a risk factor for developing POP later in life.11 The women in our study had a significant decrease in straining with bowel movements. Average Rome II scores of straining with bowel movements and the number of lumpy or hard stools significantly improved during the study period. This decrease in straining and the significant increase in bowel movements may in turn decrease some of the risk factors for POP in the future.

In our trial, we used the validated Patient Assessment of Constipation Symptoms questionnaire to show improvement in constipation symptoms as reported by the patient. The Patient Assessment of Constipation Symptoms scores for abdominal, rectal, and stool symptoms as well as the total Patient Assessment of Constipation Symptoms scores showed significant improvement during the 42-day study period. According to Frank et al14 these findings correspond to a minimal-to-moderate clinical improvement in constipation symptoms during our short study period.

We also showed that there is improvement in patient symptoms as evaluated by the Patient Assessment of Constipation Symptoms and Rome questionnaires in both the patients with and without rectoceles. Participants in both groups improved significantly whether they had a rectocele or not. The patients with rectocele showed more clinical improvement during the study period. This would indicate that patients with a rectocele should first be treated with fiber and if their symptoms do not improve significantly, then consideration should be given to surgical intervention for the correction of the rectocele. Larger series of patients with different stages of rectocele need to be performed to better evaluate these findings.

In conclusion, gradually increasing the dietary fiber intake to the amount recommended by the National Academy of Sciences Institute of Medicine improves abdominal, rectal and stool symptoms of constipation. Reducing the incidence and severity of straining and lumpy, hard stools in constipated women with pelvic floor disorders by increasing fiber intake may diminish a risk factor for the onset, progression, or recurrence of POP. Our study is limited by its small number as well as its lack of a control group. Our high withdrawal rate may have adversely affected our results. Randomized controlled trials with long-term follow-up are needed to better assess the value of dietary fiber in reducing constipation and these risk factors for POP.


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© 2008 by The American College of Obstetricians and Gynecologists.