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Keywords:

  • Intestinal transplantation;
  • intestinal failure;
  • intestine;
  • rehabilitation;
  • small bowel length

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and Methods
  5. Results
  6. Discussion
  7. Disclosure
  8. References

Normal small bowel length (SBL) has been reported within a wide range, but never studied in a cohort of either pediatric or adult deceased donors. Between 5/2006 and 2/2011, SBL was measured in all grafts procured for intestinal transplantation at a single center and used for either isolated intestinal transplant (15) or multiorgan transplants (5) employing a standardized method. SBL was the only not significantly different variable among pediatric and adult donors divided by age 16. Furthermore, donors were classified in 3 groups: group 1: Height < 70 cm, group 2: 71–150 cm and group 3: ≥ 151 cm. Mean age was: 0.58, 5.6, 22.01 years, respectively. Mean height and weight were 65.8, 123.2, 166.1 cm (p = 0.001) and 6.9, 23.8, 65.2 kg (p = 0.001), for each group. The SBL by group was: 283.0, 324.7, 356.0 cm, remaining as the only nonsignificant variable (p = 0.06), in contrast to BMI, BSA (p = 0.001). The SBL/height ratio: 4.24, 2.7, 2.12 (p = 0.001; rho: –0.623) or SBL/BSA ratio was 8.36, 3.7, and 2.03, respectively (p : 0.0001; rho: –0.9). SBL does not increase with growth like other anthropometric variables. The SBL/height ratio significantly decreases with growth; however, bowel diameter increases, which needs further evaluation.


Abbreviations: 
BMI

body mass index

BSA

body surface area

SBL

small bowel length

Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and Methods
  5. Results
  6. Discussion
  7. Disclosure
  8. References

In spite of the interest shown by anatomists, radiologists, pathologists, and surgeons to determine the normal small bowel length (SBL) and its impact on the functional status of the digestive system, more comprehensive studies on the intestinal length in both children and adults are still required.

Most investigations performed to date have resulted in variable data and arbitrary statements because in most cases the study design and the method used for the intestinal measurement were either not clear or omitted. Some studies are the result of assessing formalized deceased donors, others were performed during necropsies (1–3). Other investigators measured the intestinal length using x-rays from gastrointestinal series and follow-through. Some authors have assessed bowel length using the pylorus as the starting point, and the rectum as the ending point; others started at the ligament of Treitz, ended at the ileo-cecal valve (1–8). The most comprehensive postmortem study published to date assessing the intestinal length in neonates reports a mean length of 270 cm; the SBL reaches an average of 350 cm in deceased infants and children with a mean height of 100 cm (crown-heel length), showing that SBL plateaus in taller bodies. This study was also the first one to express SBL as a bowel length to body height ratio (8).

In spite of the absence of a uniform definition, or standardized measurement methods to assess SBL, we have learnt that the length of the small intestine is one of the main predictive factors for intestinal rehabilitation after major intestinal resections, and that short bowel syndrome is still the main indication for intestinal transplantation (9).

At present, 11 years after intestinal transplant was accepted as a clinical practice in the surgical field, no study has yet analyzed the length of the transplanted intestine (10). As shown in Figure 1, the intestine from a donor provides the most appropriate setting to assess the normal small intestinal length, starting at the ligament of Treitz and ending at the ileo-cecal valve, in pediatric and adult population under a fasting baseline condition. Therefore, our aim is, to the best of our knowledge, to disclose the first report on the small intestinal length based on a cohort of brain dead donors used for intestinal transplantation.

image

Figure 1. Picture of the intestinal grafts by age/height groups at the end of the procurement.

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Material and Methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and Methods
  5. Results
  6. Discussion
  7. Disclosure
  8. References

Between May 2006 and February 2011, the length of the small intestine was measured in every intestinal procurement procedure performed by our team, using a technique previously described (11,12). The measurement of the intestine was obtained at the end of the engraftment, starting at the ligament of Treitz for the multiorgan grafts, or at the proximal transection, (usually performed 2–3 cm distal to the ligament of Treitz) in the isolated intestinal transplants, and ending at the ileo-cecal valve or in the distal transection, usually performed 1 cm proximal to the valve. SBL was expressed in centimeters. The measurement was performed using a sterile 80 cm “umbilical tape” applied to the antimesenteric border in the natural position without stretching, and carefully following all the natural intestinal curves. Height was measured during donor evaluation), and weight (the close relatives were asked about weight at the time of consenting for donation) was the baseline weight considered. Weight is the most variable anthropometric value, not all donor hospital have beds with scales available. Furthermore, it has been reported that the estimation performed by physicians and nurses is usually unreliable, while patients or family members often make more accurate baseline weight estimations (13–15). Donor's age was included. Other anthropometric variables were calculated, including: Body surface area (BSA; the Mostellers formula) (16), BMI (17), SBL/height (8) and SBL/BSA (18). Donor variables and intestinal length were analyzed using SPSS v17® (SPSS Inc., Chicago, IL, USA).

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and Methods
  5. Results
  6. Discussion
  7. Disclosure
  8. References

Data from 20/29 intestine procurement procedures conducted at our center were included in this study. Eight donors were older than 16 years, 12 were males; 15 were isolated intestinal grafts, 5 were multiorgan grafts (1 was used for a combined liver–intestine transplant, and 4 as multivisceral grafts).

Table 1 summarizes all the data collected for the study. The results of the first analysis related to the difference between pediatric and adult donors (≥16 years of age) are presented in Figure 2. This analysis showed that the only variable that does not significantly change with age is the length of the intestine. The correlation analysis between SBL and age was: r −0.71, r2: 0.5.; p = NS. Figure 3, represents height and bowel length as continuous variables (r: 0.5, p = 0.05; rho: 0.6, p = 0.01), it also presents the mean value for the whole series (dash line) and after considering the three groups of donors based on height: group 1, with height less than 70 cm; group 2, height between 71 and 150 cm; group 3, donors taller or equal to 151 cm (bold line).

Table 1. Overall study data
HeightSexAgeBMIBSASBLSBL/HSBU/BSAPediatric/Adult
65M0.416.30.342854.48.4P
66F0.916.10.342804.28.2P
64M0.4140.312804.49P
65F0.5180.353104.88.8P
69F0.714.70.352603.47.42P
110F416.50.78285.52.63.6P
120M513.90.843703.14.4P
106M417.80.7532034.2P
130M5160.994143.24.2P
150F1013.61.122341.62.1P
157M1422.31.552901.81.8P
182M1622.61.953601.91.8P
165M1723,91.734692.82.7A
160F2023.41.6332121.9A
175M2324.51.913151.81.6A
171M2023.91.823802.22.1A
157F29.623.51.593602.32.3A
156F39.520.51.472901.81.9A
173M2223.41.834302.52.3A
165M1925.71.793452.11.9A
image

Figure 2. Anthropometrics and SBL differences between pediatric and adult donors.

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image

Figure 3. Individual SBL divided by groups, SBL averages are represented in each of them. Dash line represents overall mean, bold line represents mean by group.

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Table 2 summarizes the analysis by groups. In these analyses all the anthropometric variables have statistically significant difference among the three groups, except for the intestinal length (p = NS). The larger linear difference in bowel length is seen between the groups with a height below 150 cm in height (groups 1 and 2; Table 2/Figure 3), similar setting is observed when the proportions SBL/BSA or SBL/height were assessed comparing the three groups. The difference is significant when group 1 is compared to groups 2 and 3, but no difference was observed between group 2 and group 3 for both ratios (Table 2/Figure 4), supporting the trend to plateau of bowel growth in length compared to the most accurate and measurable anthropometric variable: that is, donor height.

Table 2. Anthropometrics and SBL differences by age/height group
Anthropometric VariablesGroup 1 Height: <70cmGroup 2 >71–150cmGroup 3 ≥151cm
  1.  *p < 0.0001.

  2. p = NS.

  3. 1r = 0.5; rho = 0.6.

  4. 2r = 0.86; rho =− 0.78.

  5. 3r= −0.95; rho =−0.9.

Age (years)0.58 ± 0.215.6 ± 2.51122.01 ± 7.51
Height (cm)65.8 ± 1.92*123.2 ± 17.64*166.1 ± 8.8*
Weight (kg)6.9 ± 0.54*23.8 ± 4.97*65.2 ± 8.75*
BMI (kg/m2)15.82 ± 1.5515.56 ± 1.7823.37 ± 1.38*
BSA (m2)0.34 ± 0.01*0.90 ± 0.15*1.73 ± 0.16*
SBL (cm)283.0 ± 17.88†,1324.7 ± 70.37†,1356.0 ± 58.3†,1
SBL/Height4.24 ± 0.51*,22.7 ± 0.65*,†,22.12 ± 0.33*,†,2
SBL/BSA8.36 ± 0.61*,33.7 ± 0.94*,32.03 ± 0.32*,3
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Figure 4. Box-plots representing the SBL/Height ratio by groups.

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Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and Methods
  5. Results
  6. Discussion
  7. Disclosure
  8. References

Figure 1 reflects the aspect of the intestinal donors (isolated, combined and multivisceral) by age group as observed at the end of the procurement by the transplant surgeons. It seems logical to think that the older the donor, the longer the intestine. That was the hypothesis that brought us to design this study, motivated by the lack of donor based literature.

The interest for SBL and to understand the growth of the human intestine are not new. One of the earliest manuscripts on the growth of the human intestine was drafted by Bryant et al. in 1924; reporting a length of 300 cm in a full term newborn intestine. Many authors (2,3) admit the lack of data on this subject, and also significant variations in length as mentioned earlier. This manuscript reports that the SBL increases during the embryonic stage, preterm infants had an average length of 142 cm at 19th gestational week, while the mean length is about 304 cm at 35 weeks.

The goal of this study was first to define the limits to measure the small bowel; all the grafts were measured from the ligament of Treitz to the ileo-cecal valve. Second, we suggest using a method that would neither affect nor modify the bowel length by stretching it and that would minimize the over estimation of the intestinal length. Finally, we had to establish the timing for measurement during the transplant procedure, and chosing the end of the reperfusion, once the usual initial hyper-motility observed decreases or stops (14), understanding that the effect of either cold or warm ischemia upon SBL has not been described. We did not measure SBL during the procurement procedure because in spite of using ideal donors, multiorgan procedures are usually shared by several teams and measuring SBL at that point might cause delays.

This method avoids other factors responsible for the variability usually reported when measurements were taken postmortem (1,8) or based on the x-rays obtained at the time of gastrointestinal series and follow through (7). The former measurements were inaccurate, which might lead to under-estimations by contraction of the smooth muscle or by autolysis. Muscle relaxation could also be observed leading in this case to the opposite result, overestimation. Therefore, our aim was to measure the intestine using a normal and functional intestine from a brain dead donor after the reperfusion time during the transplant surgery. The method used for SBL measurement is simple and may be easily employed by independent surgeons in any. Moreover, it is also the method we use not only for transplant but also for autologous reconstructive surgery to assess the final SBL.

Quantification of the normal SBL in neonates and infants has received little attention in the literature in spite of being the most important predictive anatomical factor for intestinal rehabilitation in patients with short bowel syndrome. The study performed by Stiebert (7), a logical continuation of Bryant's manuscript, used a method to assess SBL similar to the one described here, employing a number 00 Silk suture material, laid along the antimesenteric border of the small intestine to avoid stretching artifacts. The study was done at autopsies after abdominal evisceration, and reported observations similar to those described in the present manuscript. The authors described a linear growth in bowel length in deceased donors from 40 to 100 cm of crown-heel length, describing a later plateau for deceased donors up to 140 cm of height (7).

Some studies have attempted to establish rules for intestinal length estimation in children (19). The authors concluded that the following equation: SBL = 6.741–80.409/height, (r2: 0.85), may be used to estimate SBL at the time of surgery (20). Height was chosen for practical reasons: The difference between observation and actual measurement is less as compared to weight (21). Also, length is easier to measure than weight in hospitalized bedridden patients, for example, in donor hospitals. And finally, it is stable and less subject to variations during adult life or during prolonged hospitalizations.

To the best of our knowledge, this study is the first one conducted in intestinal donors. In the era of intestinal transplantation, it shows that intestinal length is increased in donors who are up to 150 cm tall, which then seems to plateau in agreement with the data reported by Siebert (7). That observation also correlates with the physiological modifications observed in body shape associated with growth in height and age. Newborns have a significantly large abdomen, that is disproportional to their limbs (in our cohort the SBL/height and SMB/BSA ratios were 4.3 and 8.4, respectively in group 1). The change in body configuration caused by aging changes the body proportions with a proportional increase in length for the upper and lower limbs affecting the SBL/height (2.7 and 2.1 for groups 2 and 3, respectively) and the SBL/BSA ratios (3.7 and 2.1 for groups 2 and 3, respectively).

From a physiological perspective, the progressive decrease in the SBL/height ratio with age might also correlate with the very well described reduction in daily caloric needs; children need better nutrient assimilation to grow while adults merely need to meet metabolic demands. Healthy newborns require an average of 120 kcal/kg/day in order to meet their caloric needs and sustain growth. An average 2-year-old child requires 100 kcal/kg/day while an adult only needs 25–30 kcal/kg/day (17,22). Therefore, SBL does not seem to continue growing with age, but a change in diameter occurs that might compensate any further need (Figure 5). That observation has never been addressed in the literature. A change in diameter provides an extra gain in the absorptive surface with aging, similarly to the changes observed in short bowel patients able to achieve intestinal rehabilitation after a significant gut resection. This might be a compensatory mechanism, or a physiological need to maintain absorption despite having lower baseline requirements. This might be a new hypothesis for future studies.

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Figure 5. Change in intestinal diameter observed by age/height groups at the end of the reperfusion.

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Some authors have reported an indirect observation in terms of absorptive surface and age/BSA, and analyzed the normal plasma citrulline values after intestinal transplant (23,24).

All our donors were ideal. Fortunately, it was not necessary to reduce bowel length because of postreperfusion ischemia or compromised postreperfusion flow. Therefore, if donor quality impairs function it might be as consequence of affecting absorptive capacity rather than SBL.

In summary, our report of SBL using a standardized assessment method in a group of brain dead intestinal donors shows that SBL does not significantly change after birth. Aging provides a significant difference in height, weight and all the associated anthropometric calculations; however, the SBL/height ratio decreases as observed in the proportional changes in body habits related to growth. The observation that age is associated with further increases in bowel diameter needs deeper evaluation leading to the scientific understanding of the anatomical and physiological patterns of the absorptive intestinal surface associated to human aging.

Disclosure

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and Methods
  5. Results
  6. Discussion
  7. Disclosure
  8. References

The authors of this manuscript have no conflicts of interest to disclose as described by the American Journal of Transplantation.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and Methods
  5. Results
  6. Discussion
  7. Disclosure
  8. References