A technique to increase jejunal mucosa surface area

New approaches to increase intestinal length: Methods used for intestinal regeneration and bioengineering

Inadequate absorptive surface area poses a great challenge to the patients suffering a variety of intestinal diseases causing short bowel syndrome. To date, these patients are managed with total parenteral nutrition or intestinal transplantation. However, these carry significant morbidity and mortality. Currently, by emergence of tissue engineering, anticipations to utilize an alternative method to increase the intestinal absorptive surface area are increasing. In this paper, we will review the improvements made over time in attempting elongating the intestine with surgical techniques as well as using intestinal bioengineering. Performing sequential intestinal lengthening was the preliminary method applied in humans. However, these methods did not reach widespread use and has limited outcome. Subsequent experimental methods were developed utilizing scaffolds to regenerate intestinal tissue and organoids unit from the intestinal epithelium. Stem cells also have been studied and applied in all types of tissue engineering. Biomaterials were utilized as a structural support for naive cells to produce bio-engineered tissue that can achieve a near-normal anatomical structure. A promising novel approach is the elongation of the intestine with an acellular biologic scaffold to generate a neo-formed intestinal tissue that showed, for the first time, evidence of absorption in vivo. In the large intestine, studies are more focused on regeneration and engineering of sphincters and will be briefly reviewed. From the review of the existing literature, it can be concluded that significant progress has been achieved in these experimental methods but that these now need to be fully translated into a pre-clinical and clinical experimentation to become a future viable therapeutic option.

Engineering of three-dimensional microenvironments to promote contractile behavior in primary intestinal organoids

Multiple culture techniques now exist for the long-term maintenance of neonatal primary murine intestinal organoids in vitro; however, the achievement of contractile behavior within cultured organoids has thus far been infrequent and unpredictable. Here we combine finite element simulation of oxygen transport and quantitative comparative analysis of cellular microenvironments to elucidate the critical variables that promote reproducible intestinal organoid contraction. Experimentally, oxygen distribution was manipulated by adjusting the ambient oxygen concentration along with the use of semi-permeable membranes to enhance transport. The culture microenvironment was further tailored through variation of collagen type-I matrix density, addition of exogenous R-spondin1, and specification of culture geometry. "Air-liquid interface" cultures resulted in significantly higher numbers of contractile cultures relative to traditional submerged cultures. These interface cultures were confirmed to have enhanced and more symmetric oxygen transport relative to traditional submerged cultures. While oxygen availability was found to impact in vitro contraction rate and the orientation of contractile movement, it was not a key factor in enabling contractility. For all conditions tested, reproducible contractile behavior only occurred within a consistent and narrow range of collagen type-I matrix densities with porosities of approximately 20% and storage moduli near 30 Pa. This suggests that matrix density acts as a "permissive switch" that enables contractions to occur. Similarly, contractions were only observed in cultures with diameters less than 15.5 mm that had relatively large interfacial surface area between the compliant matrix and the rigid culture dish. Taken together, these data suggest that spatial geometry and mechanics of the microenvironment, which includes both the encapsulating matrix as well as the surrounding culture device, may be key determinants of intestinal organoid functionality. As peristaltic contractility is a crucial requirement for normal digestive tract function, this achievement of reproducible organoid contraction marks a pivotal advancement towards engineering physiologically functional replacement tissue constructs.

Tissue engineering: a promising therapeutic approach to necrotizing enterocolitis

Tissue engineering is a promising potential candidate for treating intestinal failure resulting from necrotizing enterocolitis. This requires the acquisition, preparation and implantation of autologous organoid units. This may be affected by the complexities of periods of storage of viable donor tissue and delayed implantation. This chapter addresses the development, methodology, and application of tissue-engineered intestine in the experimental and clinical setting. Tissue engineering has the potential of avoiding the inherent toxicities of intestinal transplantation and prolonged immunosuppression.

Regenerative medicine as applied to solid organ transplantation: current status and future challenges

In the last two decades, regenerative medicine has shown the potential for "bench-to-bedside" translational research in specific clinical settings. Progress made in cell and stem cell biology, material sciences and tissue engineering enabled researchers to develop cutting-edge technology which has lead to the creation of nonmodular tissue constructs such as skin, bladders, vessels and upper airways. In all cases, autologous cells were seeded on either artificial or natural supporting scaffolds. However, such constructs were implanted without the reconstruction of the vascular supply, and the nutrients and oxygen were supplied by diffusion from adjacent tissues. Engineering of modular organs (namely, organs organized in functioning units referred to as modules and requiring the reconstruction of the vascular supply) is more complex and challenging. Models of functioning hearts and livers have been engineered using "natural tissue" scaffolds and efforts are underway to produce kidneys, pancreata and small intestine. Creation of custom-made bioengineered organs, where the cellular component is exquisitely autologous and have an internal vascular network, will theoretically overcome the two major hurdles in transplantation, namely the shortage of organs and the toxicity deriving from lifelong immunosuppression. This review describes recent advances in the engineering of several key tissues and organs.

Repairing large duodenal injuries in dogs by expanded polytetrafluoroethylene patch

BACKGROUND

One of the most challenging problems in clinical surgery is management of injured duodenum. In this experimental study, we treated large duodenal defects by an expanded polytetrafluoroethylene (ePTFE, Gore-Tex; W.L. Gore, Elkton, MD) soft-tissue patch and compared it with the jejunal serosal patch.

MATERIALS AND METHODS

A duodenal defect (about 50% of the total circumference) was created in the second portion of the duodenum in 20 dogs. The effectiveness and gross and histological examinations of the ePTFE patch technique was compared with the jejunal serosal patch.

RESULTS

No significant difference was found in early survival rates (90.9% versus 88.9%; P = 0.711). The whole grafted area was covered by neomucosa at the end of the sixth week in all animals with the ePTFE patch. The scar was small; no significant narrowing of lumen was noted and serosal healing was uniformly complete. In histological examination, complete coverage of the ePTFE grafts by neomucosa consisting of columnar epithelium with short villous formations was observed.

CONCLUSION

Use of the ePTFE patch method is easy, reliable, and comparable to the jejunal serosal patch. It can be used in the treatment of large duodenal defects, which cannot be repaired by duodenorraphy.

Animal models for intestinal tissue engineering

Although total parenteral nutrition prevents patients with short bowel syndrome from dying of starvation, having short bowel remains a severely debilitating condition. The best current treatment for inadequate absorptive surface area is through intestinal transplantation. However, this therapy is associated with significant morbidity and patients suffer from consequences of long-term immunosuppression. Additionally, the numbers of organs are limited. A new frontier in medicine is the field of tissue engineering. We will review the progress of intestinal bioengineering with a focus on the use of animal models. Investigators initially used autologous tissue as a patch to study intestinal regeneration. Subsequent studies focused on the use of absorbable biomaterials as a patch for tissue ingrowth. The most novel methodology consists of seeding a resorbable scaffold and implanting this construct to observe the regeneration of neointestine. Successful creation of esophagus, stomach, small bowel and colon has been demonstrated. Although these studies are preliminary, the results suggest that tissue-engineered intestine will become a real therapeutic option in the not too distant future for patients with inadequate intestinal tissue.

Comparison of different surgical repairs in the treatment of experimental duodenal injuries

BACKGROUND

In this experimental study, we aimed to investigate the results of different surgical repair methods for delayed reconstruction of severe experimental duodenal defects.

METHODS

A large duodenal defect with irregular and tagged margins covering about 50% of the circumference was created in the second part of duodenum of male Wistar rats. The effectiveness of primary repair, jejunal serosal patch, Roux-en-Y duodenojejunostomy, or expanded polytetrafluoroethylene patch repair techniques were investigated on the basis of survival and histologic assessment.

RESULTS

No significant survival benefit was observed between jejunal serosal patch, Roux-en-Y duodenojejunostomy, or expanded polytetrafluoroethylene patch repair techniques. But these repair modalities were associated with better survival rates than no-treatment or primary repair techniques. Complete coverage of the expanded polytetrafluoroethylene grafts by neomucosa consisting of columnar epithelium with villus formation was observed in surviving rats about 16 weeks after surgery.

CONCLUSIONS

Expanded polytetrafluoroethylene patch can be used in the repair of experimental large duodenal defects, which can not be repaired primarily.

The ileo neorectal anastomosis: an experimental study on development of the surgical technique and theoretical background

OBJECTIVE

The keystones of surgical treatment of ulcerative colitis and familial adenomatous polyposis are resection of the diseased colon with either an ileostomy or restoration of oro-anal continuity with an ileo-anal pouch. The ileo pouch anal anastomosis however, has a 15-35% pouch-related complication rate, 10% failure rate and is accompanied by an unpredictable functional outcome. In order to reduce these unfavourable rates and to improve functional results an alternative surgical technique, the ileo neorectal anastomosis (INRA), was developed experimentally.

MATERIALS AND METHODS

In an experimental study 12 Yorkshire-Dutch landpigs had a subtotal colectomy and rectal mucosectomy. Subsequently a vascularized ileal mucosa sling was created and transposed on to the denuded rectal muscular cuff in eight. In another four animals a non-vascularized mucosa sling was transposed. The covering ileostomy was closed after 3 weeks. Repeated endoscopies, histological examinations of mucosal biopsies and rectal compliance measurements were carried out to evaluate the functional result of the neorectum.

RESULTS

The surgical procedure of the INRA was technically successful in this animal study. Repeated endoscopy and histology showed complete ileal mucosa ingrowth in the neorectum without severe fibrosis in the group of animals with a vascularized sling. At follow up after 1 year no colonic metaplasia had occurred. Measurements of the neorectal reservoirs in the group of animals with a vascularized INRA procedure showed a median 'maximum tolerated volume' of 338 ml (range 300-410 ml).

CONCLUSION

The INRA is technically feasible and reproducible. The histologically proven survival of the vascularized ileal mucosa and development of a compliant neorectal reservoir make the INRA an interesting alternative restorative procedure. Avoidance of the pouch-related complications of the ileo pouch anal anastomosis by this procedure might herald a new era of restorative surgery.

Successful anastomosis between tissue-engineered intestine and native small bowel

BACKGROUND

Previous work from this laboratory has shown that isolated intestinal epithelial organoid units on porous biodegradable polymer scaffolds formed vascularized cysts lined by a neomucosa. The purpose of this study was to demonstrate anastomosis between tissue-engineered intestine and the native small bowel and to observe the effect of this anastomosis on cyst growth.

METHODS

Intestinal epithelial organoid units from neonatal Lewis rats were seeded onto porous biodegradable polymer tubes made of polyglycolic acid, and they were implanted into the omentum of adult male Lewis rats. Three weeks after implantation, the unit-polymer constructs were anastomosed in a side-to-side fashion to the native jejunum in 20 rats (group 1). The other 18 rats were closed without anastomosis (group 2). All 38 tissue-engineered constructs were harvested 10 weeks after implantation. Four rats underwent upper gastrointestinal (GI) study before they were killed.

RESULTS

The rats in group 1 increased their body weights equal to those in group 2, and there was no statistically significant difference between the two groups. Upper GI examinations revealed no evidence of either bowel stenosis or obstruction at the anastomotic site. Grossly, the patency of the anastomosis was 90% and the lumen of the cyst was visualized by the upper GI study. At the second operation, there was no significant difference in the size of the cysts in either group: however, at the time the rats were killed, the length of the cysts in group 1 was significantly longer than that in group 2 (P<0.05 using Mann-Whitney U test). Histological examination showed that cysts after anastomosis were lined by a neomucosa in continuity to native small bowel across the anastomotic site and also demonstrated crypt-villus structures. Morphometric study demonstrated that cysts in group 1 had significantly greater villus number, height, and surface length than did those in group 2.

CONCLUSIONS

Anastomosis between tissue-engineered intestine and native small bowel resulted in no complications after the operation, kept a high patency rate, and maintained mucosal continuity between the tissue-engineered intestine and native small bowel. Furthermore, anastomosis had a positive effect on cyst size and development of the mucosa in the tissue-engineered intestine.

[NO TITLE AVAILABLE]

Trinta e dois cães foram submetidos ao tamponamento seroso da junção esofagogástrica, com o objetivo de investigar experimentalmente o processo de reparação mucosa. A operação constou de cardiotomia, interessando um centímetro do esôfago e dois centímetros do estômago. Esta secção foi obliterada pelo fundo gástrico, originando uma superfície serosa elíptica, voltada para o lúmen, com três centímetros de comprimento por um centímetro de maior largura. Os animais foram divididos em quatro grupos de oito cães cada (Grupos: 1, 2, 3 e 4), sacrificados após uma, duas, quatro e oito semanas respectivamente. Os resultados foram avaliados quanto aos aspectos clínicos, pós-operatórios, e da análise macro e microscopicas dos espécimes obtidos. A evolução pós-operatória mostrou pequena morbidade, sem sinais de obstrução do trato digestivo. Ficou demonstrado à macroscopia, que a área do tamponamento exibe, na primeira semana, aspecto de lesão ulcerada, com fundo necrótico; na segunda e quarta semanas houve redução da área cruenta, até a completa cicatrização, melhor observada na oitava semana. À microscopia, a membrana serosa desapareceu precocemente, dando lugar a infiltrado inflamatório com intensa neoformação vascular, que serviu de leito para a proliferação epitelial.A neoepitelização fez-se das bordas para o centro da lesão. No esôfago, em camadas pluricelulares, completou-se em duas semanas, e no estômago, com epitélio unicelular estava completa na quarta semana.

Autologous gastro-intestinal reconstruction: the composite ileo-colic loop

A reproducible technique was developed experimentally in pigs for construction of a 'composite bowel tube' (CBT) made up of ileal mucosa that was grafted to a mucosally denuded colonic muscle surface vascularised by the colonic mesentery. Macroscopic and microscopic studies at terminal laparotomy revealed a viable, mucosally lined, patent peristaltic loop of bowel in six of the eight animals. Two animals died after sloughing the grafted mucosa. In vivo absorption studies, using l-alanine as an index of amino acid absorption, showed a transport pattern through the grafted mucosa of the composite ileo-colic loop appropriate to ileum when compared with controls. The CBT constitutes another autologous gastro-intestinal reconstructive technique for redistribution of available absorptive mucosa over a longer intestinal length, and may therefore be of benefit in the management of the short-bowel syndrome.

Short bowel syndrome: metabolic and surgical management

The management of short bowel syndrome requires long-term nutritional support and monitoring, medication, and occasionally additional surgical procedures. Constant attention is required to ensure adequate adaptation of the gut. This article reviews the normal function of the small bowel, adaptation following resection, total parenteral and enteral nutrition, and the role of adjunctive surgical procedures in the management of short bowel syndrome.

Human amniotic membrane as an intestinal patch for neomucosal growth in the rabbit model

This experiment was carried out as a preliminary study, an attempt to grow new intestinal mucosa on human amniotic membrane in the terminal ileum in 37 rabbits. After ketamin sulfate anesthesia at laparatomy, 5-cm ileal defects were patched with human amniotic membrane (5 x 2 cm). These patched intestines were investigated on the first postoperative day and the 2nd, 5th, 10th, and 20th weeks corresponding to 4, 5, 5, 10, and 10 rabbits, respectively. Only three rabbits died in the early postoperative period. There was no evidence of intestinal obstruction or dilatation with barium meal. Microscopically, the neomucosa consisted of a thin layer of columnar epithelial cells at 2 weeks with more maturity of the villi and less irregularity and branching by 20 weeks. All patches were covered with neomucosa commencing at 2 weeks and covering the whole patch area by 20 weeks. This technique's advantages are the large size and the ease of the availability of the human amniotic membrane for neonates at risk without jeopardizing the neonates tissues. It is hoped that this method might be considered when neonatal material is scarce.

Motor and absorptive function of the canine intestine following serosal patching: the effects of a lateral enterotomy on small intestinal myoelectrical activity

We studied the effects of serosal patching of a 4 x 15-cm, full-thickness, jejunal defect on absorptive function and fasting and postprandial myoelectrical activity in 5 patched and 5 control animals over a 3-month period. While fat and D-xylose absorption were similar in both groups, serum albumin was significantly depressed (2.96 +/- 0.24 g/dL preop vs 2.29 +/- 0.23 g/dL postop, p less than .05) and stool moisture content was elevated following patching (54 +/- 4% vs 67 +/- 9%, p less than .05). Neither the generation of the various phases of the interdigestive myoelectrical complex (IDMEC), the development of postprandial myoelectrical activity, or colonic myoelectrical patterns were impaired in the patched animals. The normal gradients of slow wave frequency, phase III propagation velocity, and onset of the fed pattern were similar in control and patched animals. However, jejunal slow wave frequency (cpm, control vs patch: 18.6 +/- 0.6 vs 19.5 +/- 0.6, p less than .05) and IDMEC frequency (0.36 +/- 0.25 vs 0.56 +/- 0.32, p less than .05) were greater and the IDMEC period shorter (109.6 +/- 27.8 vs 88 +/- 35.7, p less than .05) in the patch animals. In vitro studies demonstrated similar absorptive function in intact mucosa and neomucosa. We conclude that the technique of serosal patching is associated with impaired absorption in vivo. While this may be related, in part, to the minor motility changes observed, other factors such as hormonal changes may also be important.

Adaptation of jejunal to colonic mucosal autografts in experimentally induced short bowel syndrome

The behavior of jejunal to colonic mucosal autografts was studied in an experimental animal model of short bowel syndrome (SBS). Histological appearances, enterocyte enzyme activities, and in vitro glucose transport were studied at the donor and recipient graft sites in control, short-bowel syndrome, and gastrocolic fistula 5-week-old Sprague-Dawley rats. Small intestinal function was maintained in the jejunocolonic graft after 80% small bowel resection; animals in which small bowel was not resected showed loss of graft function and enzyme activity. This effect is dependent on the presence of jejunal chyme: after gastrocolic fistulae, the jejunum to colon grafts lost jejunal functional activities. Total parenteral nutrition did not alter graft behavior but improved the postoperative mortality of the procedures. The results provide additional information on intestinal adaptation in SBS.

Strategies for preserving intestinal length in the short-bowel syndrome

Total parenteral nutrition now permits long-term survival in patients after massive intestinal resection. Surgical therapy for the short-bowel syndrome is still largely experimental and cannot be recommended routinely. Thus, prevention of intestinal resection and conservation of intestinal length, when resection is necessary, should be emphasized. Strategies are presented that can be employed to preserve intestinal length when surgery is required in patients with a shortened bowel. These include strictureplasty, minimal resection, serosal patching, and intestinal tapering. In suitable candidates strictureplasty can relieve obstruction from strictures while avoiding resection. Minimal resection of involved intestine can be performed safely in selected patients with radiation injury or Crohn's disease. Serosal patching is an alternative to resection for the treatment of perforation or strictures of the intestine. Intestinal tapering can improve the function of dilated intestinal segments and eliminate the need for resection in intestinal atresia. The judicious use of these procedures can preserve intestinal length and obviate the need for long-term parenteral nutrition in patients after massive intestinal resection.

Growth of intestinal neomucosa on prosthetic materials

The short bowel syndrome is a potential complication of the surgical management of diseases of the large and small intestine. Recently methods have been examined for expanding the small bowel absorptive area using prosthetic materials. We investigated the feasibility of growing intestinal mucosa on prosthetic patches and tubes. Ileal defects were patched with a 2 X 5-cm patch of either Dacron (n = 15), polyglycolic acid mesh (PGA) (n = 9), or polytetrafluroethylene (PTFE) (n = 5) prosthesis in New Zealand white male rabbits. Gross and microscopic analysis at 2, 4, and 8 weeks revealed that the serosal surface was covered with neomucosa by 4 weeks. Dacron and PTFE grafts were either minimally attached or extruded and PGA grafts had dissolved. At 8 weeks, none of the patches were present but with all three materials the resultant area of neomucosa was only 15% of the original defect. The neomucosa was functional as determined by glucose uptake and disaccharidase activity. Three centimeter Dacron tubes were interposed in the distal ileum of 10 rabbits and in a bypassed ileal segment in 11 rabbits. There was an 80% mortality within 2 weeks, and no evidence of neomucosal growth. Although prosthetic patches support the growth of functional neomucosa, there is a minimal increase in the final surface area. The type of prosthesis did not influence the outcome. The use of Dacron tubes is associated with high mortality and no neomucosal growth. The use of prosthetic materials is not likely to be useful in the clinical management of the short bowel syndrome.

The importance of luminal factors in neomucosal growth

Growing neomucosa on patched intestinal defects has been investigated as a method of expanding the intestinal absorptive area. The purpose of this study was to determine the effect of luminal factors on the rate of growth and function of neomucosa in rabbit ileum. A 2 X 5-cm distal ileal defect was patched with adjacent colon serosa in 10 New Zealand white male rabbits. A similar defect was patched in a bypassed ileal segment in an additional 10 rabbits. Five animals in each group were sacrificed at 4 and 8 weeks for determination of the gross and microscopic growth of neomucosa, glucose uptake, and disaccharidase activity. In addition, tritiated thymidine uptake was measured in neomucosa and incontinuity ileum at the 4-week sacrifice. Grossly, the patched defects were covered in nearly all animals by 4 weeks and coverage was complete at 8 weeks. Microscopically, the mucosa was less well developed in the bypassed group with a mean villous height significantly less than the incontinuity group (139.9 +/- 13.9 microns vs 212.33 +/- 30.3 microns, P less than 0.0005). In vitro uptake of [3H]thymidine was significantly higher in neomucosa in bypassed segments when compared with neomucosa in incontinuity segments (692.5 +/- 347.8 vs 278.0 +/- 134.8, P less than .05, expressed as percentage of normal incontinuity ileum). Glucose uptake was similar in both groups but disaccharidase activity was significantly less in the bypassed group. The increased uptake of [3H]thymidine in neomucosa in the bypassed segment may reflect the histologic immaturity of this tissue with a greater proportion of DNA synthesizing cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Short bowel syndrome in infancy and childhood. Analysis of survival in 60 patients

This report concerns 60 infants and children with short bowel syndrome, most commonly caused by necrotizing enterocolitis in this study. Resection of atretic or gangrenous bowel was performed in 53 patients, tapering enteroplasty and primary anastomosis was performed in 13 patients, and temporary enterostomies were performed in 40 patients. Second-look laparotomy was useful in two of four cases of questionable bowel viability. The ileocecal valve was resected in 33 patients and remained intact in 27. The mean length of remaining bowel was 58.4 cm (range 13 to 150 cm). Seven patients with total aganglionosis and mid to proximal small bowel extension were managed with an initial enterostomy, whereas three had a pull-through procedure with an aganglionic patch enteroplasty. All patients received total parenteral nutrition and early enteral feedings. Home hyperalimentation was attempted when 50 percent of the calorie intake was enteral. Intestinal adaptation required from 3 to 14 months. Frequent setbacks were related to catheter sepsis, rotavirus infection, carbohydrate intolerance, and liver dysfunction. The overall survival rate was 85 percent, with mortality due to liver failure and sepsis associated with total parenteral nutrition.

Short bowel syndrome in infants and children

This article defines short bowel syndrome and reviews the pathophysiology, medical management, and surgical manipulations proposed to improve intestinal absorption. Emphasis is also placed on possible future methods of management.

Surgical therapy for the short bowel syndrome

The introduction of total parenteral nutrition has resulted in more patients surviving massive intestinal resection. Long-term parenteral nutrition is expensive, has potential complications, and causes inconvenience for the patient. Therefore, interest persists in surgical therapy for the short bowel syndrome. The goals of surgical therapy in the short bowel syndrome are to slow intestinal transit, increase the area of absorption, and reduce gastric hyperacidity. Patients with sufficient absorptive area, but rapid intestinal transit, benefit from antiperistaltic segments or colon interposition. Intestinal valves yield inconsistent results. Recirculating loops are associated with prohibitive morbidity and mortality. Experience with intestinal pacing is limited. Patients with dilated bowel segments may benefit from intestinal tapering or lengthening. Growing neomucosa holds promise but has not been evaluated clinically. Recent improvement in the results of intestinal transplantation in animals may warrant clinical trials. The efficacy of H2 receptor antagonists makes procedures for reducing gastric hyperacidity less necessary. None of the operations to treat the short bowel syndrome are sufficiently safe and effective to recommend their routine use. Operations should be performed only on selected patients to achieve specific goals. Although investigation continues, our emphasis should continue to be conservation of as much of the intestine as possible when massive resection is necessary.

Comparison of techniques for growing small bowel neomucosa

Small bowel neomucosa has been grown on a variety of surfaces. The purpose of this study was to compare the rate of growth and function of neomucosa on colon serosa (CS) and abdominal wall muscle (AM) in New Zealand white rabbits. The terminal ileum was incised for 5 cm and patched with either adjacent CS (23 animals) or AM (19 animals) to create a 2 X 5-cm defect. Gross and histologic examinations of the specimens at 1, 2, 4, and 8 weeks revealed that the rate of growth was similar in both groups. There was minimal lateral ingrowth at 2 weeks, nearly complete coverage of the defects at 4 weeks, and complete coverage of the defect at 8 weeks in more than 85% of animals with mature villi and muscularis mucosae. The ileal diameter at the site of patching increased in both groups from 11.9 +/- 2.6 to 16.3 +/- 3.2 mm in the CS group and 11.3 +/- 2.5 to 15.1 +/- 1.8 mm in the AM group (P less than 0.01). Glucose uptake was similar in both groups being 65.4 +/- 24.1% of control in the CS group and 73.9 +/- 29.8% in the AM group. Brush border enzyme activity of sucrase, maltase, and lactase was similar to controls in the AM group but in the CS group activity of sucrase and maltase were significantly less than controls (P less than 0.01). Average body weight was increased postoperatively in both groups. There was one anastomotic leak in each group and two cases of partial intestinal obstruction in the abdominal wall group.(ABSTRACT TRUNCATED AT 250 WORDS)

Intestinal loop lengthening--a technique for increasing small intestinal length

A reproducible technique is described for doubling the length of a loop of small intestine, while simultaneously reducing its luminal diameter, and preserving the maximum amount of small bowel mucosa for intestinal adaptation. In pig experiments, 7 loops have been increased in length by the "intestinal loop lengthening" procedure, with survival of 5 of the 7 animals for a period of 16-26 wk. Leakage from the lengthened intestinal segment led to the death of one animal. At a second operation, or at termination of the experiment, all seven lengthened loops had a good blood supply and were patent along their full length. Histologic examination of 3 of the 4 specimens from the first phase of the study confirmed their viability. The potential application of intestinal loop lengthening in the management of the short gut syndrome is discussed.