RESEARCH ARTICLE

Bowel Habits after Gastric Bypass Versus the DuodenalSwitch Operation

Nir Wasserberg & Nahid Hamoui & Patrizio Petrone &

Peter F. Crookes & Howard S. Kaufman

Received: 15 April 2008 /Accepted: 4 August 2008# Springer Science + Business Media, LLC 2008

AbstractBackground One of the perceived disadvantages of thebiliopancreatic diversion with duodenal switch operation isdiarrhea. The aim of this study was to compare the bowelhabits of patients after duodenal switch operation or Roux-en-Y gastric bypass.Methods A prospective comparative case series design wasused. Forty-six patients who underwent duodenal switch(n=28) or gastric bypass (n=18) were asked to complete adaily diary for 14 days after losing least 50% of their excessbody weight. Data were collected on number of bowelepisodes, incontinence, urgency, stool consistency, andawakening from sleep to defecate. Background variableswere recorded from the medical files.Results The duodenal switch group was heavier (body massindex 53.5 vs 47.0 kg/m2, p=0.03) and older (47.5 vs41.0 years, p = NS) than the gastric bypass group. Mediantime to 50% excess body weight loss was 22 months in theduodenal switch group compared to 10.0 months in thegastric bypass group (p=0.001). Patients after duodenalswitch surgery reported a median of 23.5 bowel episodesover the 14-day study period compared to 16.5 in the gastricbypass group (p = NS). There was no between-groupdifferences in any of the other bowel parameters studied.

Conclusions Although duodenal switch is associated withmore bowel episodes than gastric bypass, the difference isnot statistically significant. Bowel habits are similar inpatients who achieve 50% estimated body weight loss withduodenal switch surgery or gastric bypass.

Keywords Bowel habits . Duodenal switch . Gastric bypass

Introduction

With the rise in the national and global incidence of morbidobesity, surgical treatment has become an increasinglypopular option. It is advocated by the National Institutesof Health for individuals with a body mass index (BMI) of35–40 kg/m2 and severe comorbidities or a BMI of >40 kg/m2

[1]. Bariatric surgical procedures may be roughly categorizedas restrictive, malabsorptive, and combined. All types haveproven satisfactory for weight loss [2]. While broad guidelinesexist for selection of patients for bariatric surgery [3], littleinformation exists to guide the choice of procedure forindividual patients. In practice, the choice of procedure isguided by the patient’s BMI, body habitus, age, gender, othercomorbid conditions, the cost of the operation, the patient’sown desires, and the surgeon’s previous training andexperience [4, 5].

Obesity is associated with numerous comorbid condi-tions, impairing the patient’s health and quality of life [6].Among other well-described comorbidities, the associationbetween excessive weight and fecal incontinence is becomingwell recognized [7]. In fact, more than 40% of obese femalesdescribed some degree of fecal incontinence [8], and morbidobesity is acknowledged as a major risk factor for fecalincontinence along with age and obstetric injury [9]. Fecalincontinence in the obese patient may be related to increased

OBES SURGDOI 10.1007/s11695-008-9658-9

N. Wasserberg :N. Hamoui : P. Petrone : P. F. Crookes :H. S. KaufmanDivision of Colorectal and Pelvic Floor Surgery (NW, PP, HSK)and the Bariatric Surgery Program (NH, PFC),Department of Surgery, University of Southern California,Los Angeles, CA, USA

N. Wasserberg (*)Department of Surgery B, Rabin Medical Center,Beilinson Campus,Petah, Tiqwa 49100, Israele-mail: nwasserberg@gmail.com

intraabdominal pressure with chronic compression andstretch on the pelvic floor muscles and nerves, on the analsphincter complex, and on the supporting endopelvic fascia[10].

Morbidly obese patients with fecal incontinence presenta management dilemma for surgeons in selecting theoptimal weight reduction procedure. While some patientsmay enjoy a decrease in symptoms of incontinencefollowing significant weight loss, others may face anincrease in bowel leakage after surgery due to poor analsphincter function. Malabsorptive procedures like thebiliopancreatic diversion with a duodenal switch (BPD-DS) are perceived to induce looser and more frequent stools[2]. While it may appear intuitive to offer a restrictiveprocedure rather than malabsorptive procedure to a patientwho presents with preoperative bowel leakage, there arefew data in the literature to support that assumption sincethere are no studies comparing bowel habits after malab-sorptive or restrictive procedures. The purpose of this studyis to determine whether there is a difference in bowel habitsafter restrictive (Roux-en-Y gastric bypass [RYGBP]) andmalabsorptive (BPD-DS) surgeries for morbid obesity.

Materials and Methods

A prospective case series design was used. The study wasconducted as part of the Bariatric Surgery Program at USCUniversity Hospital, Los Angeles, CA, USA between June2005 and July 2006. The study sample consisted of patientswho had undergone either BPD-DS or RYGBP andsubsequently lost at least 50% of their excess body weight(EBW).

The BPD-DS was performed by an open technique witha common channel of 100 cm. RYGBP was performed byeither open or laparoscopic techniques. The lengths of theroux limb were 100 cm in all. The biliopancreatic limb wasmeasured 50 cm in the open cases and approximated for thesame length in the laparoscopic cases.

Study candidates were recruited during follow-up at theoutpatient clinic. Those who agreed to participate andsigned an informed consent form were asked to completedemographic and bowel function questionnaires. The bowelfunction questionnaire included a 14-day diary that was

completed in a prospective fashion. Questions includednumber of bowel episodes (BE), episodes of incontinenceor urgency, stool consistency, and whether they awoke fromsleep to defecate. Stool consistency was graded by usingthe Bristol stool form scale [11], which is sensitive tointestinal transit time and type of feces ranging from lumpystools (1) to watery diarrhea (7).

Patients with a history of previous colon resection, adiagnosis of chronic ulcerative colitis or Crohn’s disease,and diarrhea-predominant irritable bowel syndrome wereexcluded from the study. The study was approved by theInstitutional Review Board.

Statistical Analysis

Variables are present as mean ± standard deviation. Resultswere compared using the Mann–Whitney and chi squaretests. p≤0.05 was considered statistically significant.

Results

The study sample included 46 patients, of whom 28 (61%)were treated with biliopancreatic diversion with duodenalswitch and 18 (39%) with Roux-en-Y gastric bypass. Forty-one (89%) were female; the male-to-female ratio was 2:26in the duodenal switch group and 3:15 in the gastric bypassgroup (p=0.9). Median age was 45 years (range 25 to 67),and it was higher in the duodenal switch group than in thegastric bypass group (47.5 vs 41.0 years, p=0.1, NS).Median preoperative BMI for the whole sample was 51 kg/m2

(range 37 to 65 kg/m2): 53.5 kg/m2 in the duodenal switchgroup and 47.0 kg/m2, in the gastric bypass group; thisdifference was statistically significant (p=0.03). Median timefrom surgery to 50% excess body weight loss was 22 months(range 18–27 months) in the duodenal switch group and10 months (range 8 to 17 months) in the gastric bypassgroup (p=0.001; Table 1).

Patients in the BPD-DS group reported a median 23.5BE over the 14-day period compared to 16.5 in the RYGBPgroup (p=0.07). At lease one episode of incontinence wasreported by 42.9% of the gastric bypass group and 17.9%

Table 1 Patient characteristics

DS GB P value

Median age (years) 47.5 41.0 0.1Gender (Male:Female) 2:26 3:15 0.9Median BMI(kg/m2) 53.5 47.0 0.03Survey (median months after surgery) 22 10 0.001

DS Duodenal switch, GB gastric bypass

Table 2 Bowel habits comparison

DS GB P value

Incontinence (%)a 17.9 42.9 0.30Urgency (%)a 67.9 88.9 0.16Episodes of waking from sleep (%)a 39.3 50.0 0.55Stool consistency (median grade) 3.8 3.0 0.09Bowel episodes (n, 14-day period) 23.5 16.5 0.07

DS Duodenal switch, GB gastric bypassa At least one episode

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of the duodenal switch group (p=0.30). More patients inthe RYGBP group reported at least one episode of stoolurgency and at least one episode of being wakened fromsleep by the need to defecate, than in the BPD-DS group.Neither of these differences was statistically significant.There were also no differences in stool consistency betweenthe groups (Table 2).

Discussion

Roux-en-Y gastric bypass is currently the most widelyperformed bariatric operation in the United States [2]. Thisrestrictive procedure surgically alters the stomach’s capacitybut differs from simple restrictive surgeries by rerouting orbypassing parts of the small intestine, causing slightmaldigestion. The BPD-DS procedure combines Scorpinaro’smalabsorptive BPD [12] with the duodenal switch operation,in which the Roux limb is anastomosed not to the stomachbut to the duodenum 3–5 cm beyond the pylorus. Thisprocedure also combines sleeve gastrectomy, which leaves anarrow gastric tube based on the lesser curvature. The BPD-DS combines an element of restriction with a malabsorptivecomponent, thus, avoiding the major side effects of extremerestriction or malabsorption [2].

Obese patients experience increased gastrointestinalsymptoms including abdominal pain, nausea, increasedflatus, loose stools, hard stools, and incomplete evacuation[13]. The proposed etiology for these symptoms has beenrelated to a chronically increased abdominal pressure thatmay produce irritable bowel-like symptoms [14]. Fosteret al. [15] showed a significant improvement in gastroin-testinal symptoms such as decreased flatus, reduced needfor urgent defecation, and increased and decreased passageof stools 6 months after RYGBP in morbidly obesepatients. In contrast, the original BPD procedure is thoughtto induce diarrhea with increased number of bowel episodesper day, causing lifestyle alteration [16]. These symptomsare seen to some extent after BPD-DS and are most likelyrelated to the length of the common channel [17] andalthough a 100-cm common channel is more frequentlyused [17] than the original recommendation of 50 cm [18],BPD-DS is still considered to induce postoperative diarrheaand excessive flatus, whereas it is commonly believed thatRYGBP tends to produce constipation [17].

In the present study, we compared bowel habits afterRYGBP and PBD-DS that induce weight loss in differentmechanisms. The results demonstrate that after achievingequal or greater then 50% of EBW loss, bowel symptoms inthe two groups were similar. Although the number ofoverall bowel episodes was higher in the duodenal switchgroup, the difference did not reach statistical significance. Itis possible that the study lacked sufficient statistical power

owing to the relatively small size of the groups. Additionally,the study diary emphasizes on defecating characteristics andhas no specific consideration to flatulence, an importantrelated aspect of bowel function.

To date, there is no consensus on how to match aparticular operative procedure to an individual patient. Themost common variables entering into the decision includedemographics (age, gender, race) as well as the degree ofobesity and the extent of commonly associated comorbidconditions [19]. Given the high incidence of lowergastrointestinal symptoms in morbidly obese patients [20],we believe that it is important to identify these symptomsand to consider further preoperative investigations, such asanorectal physiology studies, before planning surgery.

Both BPD-DS and RYGBP produce approximately 70%of excess body weight loss [19, 21] and produce similarrates of resolution for diabetes mellitus, hypertension, andsleep apnea [22, 23]. In contrast to previous reports [19],patients undergoing RYGBP in the current study hadreached 50% EBW in a significant shorter period of timethan patients after BPD-DS. This may reflect the greaterpreoperative BMI of BPD-DS patients, since greaterabsolute weight loss must occur to reach the 50% EBWLthreshold. Heavier patients may have undergone the BPD-DS as a consequence of their own personal choice or thesurgeon’s bias that it provides superior weight loss in superobese patients.

The relative similarity in functional outcome betweenBPD-DS and RYGBP was unexpected in view of theprevailing opinions commonly found in standard texts. It ispossible that conducting the study after a sufficiently longtime period to achieve substantial weight loss permittedearly postoperative functional disturbances to stabilize.Further studies are clearly needed to explore this importantaspect of the functional outcome after bariatric surgery.

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