Adaptive changes in ileal mucosal nutrient transport following colectomy and endorectal ileal pull-through with ileal reservoir

Iron-deficiency anemia as presentation of pouchitis

GOALS

This study sought to describe the percentage and cause of anemia in patients who underwent ileal pouch with anal anastomosis (IPAA) for ulcerative colitis (UC), and to compare the distribution of complications in patients with and without anemia, especially pouchitis, after IPAA.

BACKGROUND

IPAA is the surgical procedure of choice for UC. Complications include pouchitis (40%), strictures (30%), small bowel obstruction (10%), pelvic sepsis (<5%), and urinary and sexual dysfunctions (<5%). Few studies have described the prevalence of anemia after IPAA, but no conclusive findings have been reported.

STUDY

Patients who had undergone IPAA for UC were recruited from the UPR Inflammatory Bowel Disease Clinic and the Gastroenterology Research Unit. Demographic and medical data were obtained. Anemia was diagnosed using standard hematologic criteria. Serum iron, ferritin, transferrin, folate, vitamin B12, erythropoietin, total iron-binding capacity, reticulocyte count, peripheral smear, and bone marrow aspirate were evaluated in patients with anemia. Data analysis was performed with EPI Info version 6.4d.

RESULTS

Iron-deficiency anemia was identified in 55.5% (10/18) of patients and pouchitis was found in 77% (14/18). All 10 patients with anemia had pouchitis, whereas only 4 of the 8 without anemia had pouchitis. In half of the anemic patients, pouchitis was asymptomatic.

CONCLUSIONS

Iron-deficiency anemia may be a clinical presenting sign of pouchitis. Hemoglobin levels may be considered as surveillance tools for pouchitis in patients with IPAA.

Orthotopic transplantation of intestinal mucosal organoids in rodents

BACKGROUND

Orthotopic transplantation of intestinal mucosal organoids that contain putative mucosal stem cells serves as an important step toward implementing intestinal gene therapy and treatment for malabsorption syndromes in animals and humans. We hypothesized that intestinal mucosal organoids can be transplanted along the axis of the small bowel giving rise to a neomucosa expressing proteins of its donor origin.

METHODS

Epithelial organoids were harvested from neonatal mice or rat small intestine with the use of a combination of enzymatic digestion with dispase and collagenase, and gravity sedimentation. In adult syngeneic recipients, a 7-cm segment of midjejunum was isolated, leaving its vascular pedicle intact. The remaining proximal and distal segments were anastomosed to restore intestinal continuity. The isolated segments were randomly subjected to surgical or chemical mucosectomy with a chelator solution for 30, 45, or 60 minutes and then compared. Histologic examination was used to confirm the presence of enterocytes, goblet cells, enteroendocrine cells, and Paneth cells in the neomucosal segments. To confirm the presence of ileal bile acid transporter (IBAT) gene message and function, we measured sodium-dependent bile acid uptake and IBAT-messenger RNA. Immunohistochemical examination using anti-IBAT antibodies was performed to demonstrate the expression of IBAT in the neomucosal segments. Experiments were repeated in a murine model transgenic for the green fluorescent protein to verify donor origin of the engrafted mucosa expressing IBAT.

RESULTS

The area of peak IBAT function was found to be located in the terminal ileum. Organoid units harvested from this region were capable of generating a small-bowel neoileal mucosa after being seeded into the jejunum. This mucosa was histologically confirmed to differentiate into all 4 intestinal lineages and to express IBAT signal, confirming its donor-derived origin. Optimal engraftment of mucosa expressing the IBAT protein was found in isolated jejunal segments debrided for 45 minutes. Sodium-dependent bile acid uptake was 5-fold higher in the neoileum, compared with the jejunum. IBAT-mRNA levels in the neoileum were 18-100-fold higher than those in the jejunum. Areas of green fluorescent protein-positive mucosa stained positively with anti-IBAT antibody in adjacent sections, suggesting that the regenerated mucosa is from transplanted ileal stem cells.

CONCLUSIONS

Orthotopic transplantation of epithelial organoids containing ileal stem cells was used to generate a neoileal mucosa that expressed all 4 intestinal lineages along with a new zone of active bile acid uptake and IBAT expression in a recipient jejunal segment.

Treatment of bile acid malabsorption using ileal stem cell transplantation

BACKGROUND

We hypothesized that ileal stem cell clusters transplanted into a segment of jejunum can be used to treat bile acid malabsorption.

STUDY DESIGN

In adult Lewis rats, a 15-cm segment of jejunum was isolated with its blood circulation left intact and partially stripped of enterocytes using luminal high-velocity perfusions with 3mmol/L ethylenediamine tetra-acetic acid solutions. Continuity was restored by anastomosing the proximal and distal gut. Ileal stem cell clusters were harvested from neonatal Lewis rats and transplanted into the stripped segments to generate a "neoileum." After 4weeks, recipients underwent resection of the native ileum, and the isolated neoileum was anastomosed in its place. After an additional 4weeks, a 48-hour stool collection was performed. The engrafted segment was harvested for taurocholate uptake studies, ileal bile acid transporter (IBAT) protein by immunohistomorphometry, and IBAT mRNA quantitation by reverse transcription polymerease chain reaction. Data were analyzed by ANOVA/t-test. Rats undergoing ileectomy, jejunectomy, or sham operations served as controls.

RESULTS

Total bile acid loss in the stool was markedly lower in rats with a neoileum compared with rats with an ileectomy (p < 0.001). Total taurocholate uptake was notably increased in the neoileum compared with the jejunum (p < 0.001). IBAT protein signal intensity was considerably higher in the neoileum compared with jejunum (p < 0.001). IBAT mRNA amounts in the neoileal group were comparable with those in normal rat ileum and were considerably higher (p = 0.003) than in the jejunum.

CONCLUSIONS

Ileal stem cell clusters were used to establish a new zone of bile acid uptake and IBAT expression in a jejunal segment. This neoileum eliminated loss of bile acids in the stool after ileectomy. This is the first time that transplantation of intestinal stem cell clusters has been shown to correct a clinical malabsorption syndrome.

Identification of optimal harvest sites of ileal stem cells for treatment of bile acid malabsorption in a dog model

Ileal mucosal stem cells expressing the sodium-dependent ileal bile acid transporter (IBAT) have been successfully transplanted into the jejunum of rodents in projects aimed at creating a "neoileum" to treat bile acid malabsorption. To find optimal harvest sites for a dog model of stem cell transplantation, the exact location of peak IBAT expression in the donor ileum needs to be known. We therefore mapped IBAT function, IBAT mRNA, and IBAT protein in the ileum of Beagle dogs (N=3). Mucosal samples were taken every 5 cm in the ileum and every 20 cm in the jejunum of each dog. Sodium-dependent (active) and sodium-independent (passive) taurocholate uptake rates were measured using a standardized everted sleeve technique. IBAT mRNA concentrations were determined by semiquantitative reverse transcriptase-polymerase chain reaction and IBAT protein concentrations by fluorometric immunohistochemical analysis. The small bowel measured 208+/-17 cm (mean+/-standard error of the mean). Active and passive uptake rates were found to follow distinct distribution curves. Significant active uptake was seen only at the terminal 50 cm and peaked at 479+/-176 pM/mm(2). Depending on location, active uptake accounted for approximately half of the total uptake. IBAT mRNA and protein distributions corroborated uptake curves. The terminal 10 to 50 cm of ileum has the highest bile acid uptake capacity. This short segment appears to be the most promising donor site for ileal stem cell transplants to create a "neoileum" in dogs.

Electrolyte profiles within the ileoanal pouch: measurement by an in vivo equilibrium dialysis technique

BACKGROUND

Patients with an ileoanal pouch have high rates of fluid and electrolyte loss. These improve with pouch adaptation. There is limited information concerning secretion and absorption in the stable ileoanal pouch. A new method to measure and characterize electrolytes in the ileoanal pouch is described.

METHODS

Following an in vitro study, nine patients with a stable ileoanal pouch had consecutive placement of dialysis bags consisting of a semi-permeable membrane containing 5 ml of 10% dextran in normal saline into the ileoanal pouch. These were left in place for 15, 30, 60, and 120 min. After determining that 60 min was the optimal timing for measurement of electrolyte concentrations, 12 normal volunteers underwent a similar in vivo dialysis study with dialysis bags withdrawn at 60 min. Sodium, chloride, potassium, phosphorus, calcium and magnesium concentrations in the dialysis bags were compared between the two groups.

RESULTS

In the in vitro and in vivo studies, the measured electrolytes reached equilibrium within 60 min. Statistically significant differences between sodium concentrations (160.9 +/- 30.2 vs. 116.8 +/- 13.8 mmol/l, respectively) and phosphorus concentrations (6.8 +/- 5.2 vs. 1.8 +/- 0.7 mg/dl, respectively) at 60 min in ileoanal pouch patients and volunteers were found (p<0.001). There were no statistical differences in the other measured electrolytes between the two groups.

CONCLUSION

An in vivo dialysis technique is described for measuring electrolyte concentrations within the ileoanal pouch. Differences in sodium and phosphate concentrations may reflect incomplete adaptation of the ileoanal pouch, and are a potential explanation for increased stool frequency in these patients.

Systemic effects of acute terminal ileitis on uninflamed gut aggravate bile acid malabsorption

BACKGROUND

Some patients with terminal ileitis suffer from significant bile acid malabsorption even if the inflammation is locally limited. We hypothesized that inflammation in the terminal ileum may lead to changes in mucosal absorption in more proximal intestinal segments and aggravate bile acid malabsorption.

METHODS

Five hamsters underwent laparotomy and localized instillation of 2,4,6-trinitrobenzenesulfonic acid (TNBS) in 10% ethanol into the last 4 cm of ileum to create terminal ileitis. A control group (n = 5) underwent instillation of saline. Animals were sacrificed after 24 h. Active and passive transport of radiolabeled bile acids was measured in the proximal and terminal ileum and glucose absorption in the jejunum using an everted sleeve technique. Myeloperoxidase (MPO) activity and histomorphology were examined by standard methods.

RESULTS

In animals with ileitis, active bile acid uptake decreased by 84% in the terminal ileum (t test, P <0.001) and by 58% in the proximal ileum (P < 0.05) compared with saline-treated controls. Jejunal glucose absorption decreased by 59% (P < 0.01). Passive bile acid and glucose absorption rates were not significantly changed in any segments of treated animals versus controls. Histological examination of the treated group revealed signs of acute terminal ileitis without changes in the proximal ileum and jejunum. All control tissues were uninflamed. MPO activity was 13-fold increased in the inflamed ileal samples compared with controls (P <0.001). No significant changes were seen in the proximal ileum and jejunum. There was no evidence of reflux of TNBS into proximal ileum. Nominal mucosal surface area values showed no significant changes between groups. Pretreatment of an additional group of hamsters (n = 5) with acetylsalicylic acid before TNBS instillation ameliorated the inflammatory response in the terminal ileum and largely abrogated the negative effects on ileal bile acid absorption.

CONCLUSION

These data suggest that limited acute ileitis impairs active bile acid uptake in the terminal ileum. It also diminishes active bile acid and glucose absorption in more proximal segments of the small intestine, likely by a systemic effect. This systemic effect may aggravate bile acid malabsorption in patients with limited ileitis.

Functional and morphologic changes of the ileal mucosa after ileoanal pouch procedure

BACKGROUND

Restorative proctocolectomy is used widely for treatment of ulcerative colitis and familial polyposis coli. Limited information is available regarding the morphologic and functional adaptation of the mucosa in a functioning ileoanal pouch.

STUDY DESIGN

Ileal pouch specimens from patients who underwent pouch reconstruction (mean 7.5 years postcolectomy, n = 12) were compared with normal ileum (n = 15) and normal colon (n = 5). Amino-oligopeptidase (AOP) and maltase activity were measured as parameters of normal ileal function. Histologic samples were examined for the presence of neutrophils and plasma cells, the villus to crypt height ratio, and the degree of crypt hyperplasia, villus blunting, and goblet cell mass. Data were analyzed by analysis of variance.

RESULTS

The AOP activity in the normal ileum was 73 +/- 32 units of enzymatic activity per gram of mucosal protein; the AOP activities of the pouch and colon were 21 +/- 22 and 16 +/- 10, respectively. The maltase activity of the normal ileum measured 254 +/- 116 units of enzymatic activity per gram of mucosal protein, and the maltase activities of the pouch and colon were 57 +/- 71 units and 29 +/- 25 units, respectively. The ileal pouch mucosa demonstrated little acute inflammation and varying degrees of chronic inflammation. Morphologically, the ileal pouch mucosa demonstrated a range of adaptations, including villus blunting and crypt hyperplasia. Several specimens contained immature epithelial cells.

CONCLUSIONS

The AOP and maltase activities in mucosa from ileoanal pouches and colon were significantly lower than those in normal ileal mucosa. Ileoanal pouch mucosa from humans undergoes adaptive changes to resemble colonic mucosa both morphologically and functionally.

Metabolic consequences of total colectomy

Colectomy is performed for inflammatory bowel disease, familial polyposis syndrome and colorectal carcinoma. Surgical procedures are ileostomy with or without pouch, ileorectal anastomosis or ileal pouch-anal anastomosis. One of the major functions of the intact large intestine is to absorb water and electrolytes. After colectomy, as much as 400-1000 ml of nearly isotonic ileostomy fluid may be excreted, resulting in a chronic salt and water depletion. This is compensated for by an activation of the renin-angiotensin-aldosterone system. Reduced urine volumes may cause kidney stones. Both dehydration and renal sodium retention are probably less frequent in patients with ileal pouch-anal anastomosis. Absorption of nutrients in general is not impaired by colectomy. The large intestine salvages energy from malabsorbed organic matter through absorption of the short-chain fatty acids produced in bacterial fermentation. In ileostomy patients, fermentation is negligible, which leads to a significant loss of energy in the ileostomy fluid. Pouches are colonized by a bacterial flora similar to colonic bacteria. In these patients conservation of energy from malabsorbed substrate may be similar to healthy subjects. Resection of ileum and bacterial colonization may lead to malabsorption of vitamin B12 and bile acids. The latter may cause increased incidence of biliary cholesterol stones. Pouchitis is a frequent problem which may be caused by a deficiency of short-chain fatty acids and glutamine in the pouch contents. It is concluded that although the colon is not essential as a digestive organ in man, colectomy results in a number of metabolic changes. The ileal pouch-anal anastomosis may in part substitute for the functions of the large intestine.

Bile acid absorption from ileoanal pouches using enema scintigraphy

It is unclear whether bile acid absorption is affected by ileoanal pouch construction. Bile acid absorption was measured in the abdomen of 16 patients with pouches (nine with good and seven with poor pouch function based on a clinical score) and in six patients with an end ileostomy using a radiolabelled synthetic bile acid (75SeHCAT) enema and dynamic scintigraphy. The median (interquartile range) 75SeHCAT absorption was 81 (79-87) per cent in patients with ileostomy, 46 (43-53) per cent in patients having well functioning pouches, and 24 (18-38) per cent in the group with poor pouch function (P < 0.01). Log transformation of the absorption curves revealed a two-component uptake (fast component t1/2 = 1.4-7.2 min; slow component t1/2 = 16-144 min) in all patients with ileostomy, in eight of nine patients with pouches with good function, and in one of seven patients with a poorly functioning pouch (P < 0.05); in the other six patients with poorly functioning pouches, only the slow component of absorption was present. This test showed significantly reduced bile acid absorption in patients with an ileoanal pouch and gave an objective discrimination between well and poorly functioning pouches.

Clinical and physiological aspects of ileal pouch-anal anastomosis

Proctocolectomy with ileal pouch-anal anastomosis is the surgical treatment of choice for severe chronic ulcerative colitis and familial polyposis coli because the entire colonic mucosa is removed while anal function can be preserved and the necessity for permanent ileostomy is eliminated. Long-term functional results are generally gratifying, as defecation frequency and degree of incontinence are acceptable in most patients. Pouchitis, however, a non-specific inflammation of the ileal reservoir, is a major long-term complication occurring in a considerable number of patients. The etiology of pouchitis is unknown. Since pouchitis occurs more frequently or even exclusively in ulcerative colitis patients it is assumed that pouchitis is a novel manifestation of inflammatory bowel disease. However, bacterial overgrowth in the ileal pouch may also play a pathogenetic role. Chronic inflammation and villous atrophy of varying severity is found in virtually all pouches. Acute inflammatory changes and ulceration are associated with pouchitis.

Early and long-term effects of colectomy and endorectal pullthrough on bile acid profile

OBJECTIVE

Although total colectomy with mucosal proctectomy and endorectal pullthrough affects two sites critical to the enterohepatic circulation of bile acids, little information is available regarding the manner in which normal digestive physiology is altered by these procedures. This study defines the early and long-term effects of colectomy and endorectal pullthrough on bile acid profile and the long-term effects on biliary lipid metabolism.

SUMMARY BACKGROUND DATA

Specific changes in bile acid absorption have been reported in patients after ileal resection. Recent studies from our laboratory indicate that in the early postoperative period, colectomy with endorectal pullthrough causes a significant decrease in gallbladder bile concentrations of total bile acids, cholesterol, phospholipids, and calcium. The observation by several authors that the pouch undergoes morphologic and perhaps functional adaptation suggest that these changes may be transient and perhaps reversible.

METHODS

These studies were done in an awake, unanesthetized canine model that allows periodic sampling of gallbladder bile without creation of an external biliary fistula and its associated sequelae. Animals were ultimately randomly assigned to either laparotomy and gallbladder cannulation (N = 6), or gallbladder cannulation with total colectomy and ileorectal anastomosis (N = 7), or biliary cannulation, colectomy, mucosal proctectomy and endorectal pullthrough with ileal reservoir (N = 5).

RESULTS

Six weeks after operation, colectomy and ileorectal anastomosis were associated with a significant alteration in the relative composition of bile acids in gallbladder bile. These early changes were manifested by a significant (p < 0.05) increase in taurocholic acid and a concomitant decrease in taurodeoxycholic acid. These changes became even more pronounced in the ileorectal anastomosis group 12 weeks after colectomy and ileorectostomy. Although similar changes in the relative concentrations of individual bile acids occurred in the 6-week endorectal animals, bile acid profile was restored to normal by 12 weeks.

CONCLUSIONS

Colectomy with ileorectal anastomosis leads to early and significant changes in bile acid profile, which persist and become even more pronounced with time. In contrast, the construction of an ileal reservoir after colectomy facilitates restoration of a normal bile acid profile. We propose that these alterations in bile acid metabolism result from adaptation of the ileal reservoir as its mucosa assumes functional characteristics of normal colon.

Inflammatory bowel disease. Part II: Clinical and therapeutic aspects

Once regarded as medical curiosities, ulcerative colitis and Crohn's disease have achieved a remarkable change in status recently and today are among the more compelling of all human illnesses. The cause(s) of inflammatory bowel disease (IBD) are not known. Genetic, environmental, microbial, and immunologic factors are involved, but the precise mechanisms are obscure. The incidence of ulcerative colitis is relatively stable, while Crohn's disease continues to increase in frequency. In 10% to 15% of patients, it is hard to differentiate between ulcerative colitis and Crohn's colitis, however, problems with diagnosis usually resolve with time and repeated examinations. In part I of his two-part monograph on IBD, Dr. Kirsner addressed the nature and pathogenesis of the disease. Increased study of ulcerative colitis and Crohn's disease in recent years has generated new knowledge regarding their etiology. Part I focused on microbial, immunologic, and genetic mechanisms of, and the inflammatory process involved in the disease. In this part, Dr. Kirsner deals with the clinical features, course, and management of IBD, based on the author's 55 years of experience with these problems and supplemented by critical examination of the recent (1988-1990) literature. Particular attention is directed to the symptoms and physical findings of ulcerative colitis and Crohn's disease. The laboratory, radiologic, endoscopic, and pathologic features, and the many systemic complications. IBDs are mimicked by several enterocolonic infections and other conditions making differential diagnosis necessary. Inflammatory bowel disease in children and the elderly conforms to conventional clinical patterns modified by the health circumstances of the respective age groups. Because the cause of IBD has not been established, current medical therapy is facilitative and supportive rather than curative. The principles of medical treatment are approximately the same for ulcerative colitis and Crohn's disease. Treatment emphasizes a program rather than a drug and also considers the individuality of the therapeutic response. A clearer understanding of dietary and nutritional needs, including hyperalimentation and electrolyte and fluid balance, aids treatment. Antidiarrheal and antispasmodal preparation and sedatives are prescribed for symptom relief. The bowel inflammation is controlled with sulfasalazine or the newer 5-amino-salicylic acid (5-ASA) compounds, antibacterial drugs for complications of Crohn's disease and IBD, adrenocortical steroids, and the immunosuppressive compounds 6-mercaptopurine (6MP), azathioprine, and cyclosporine, as determined in each patient. The surgical procedures available for treatment of ulcerative colitis include total proctocolectomy and ileostomy or ileoanal anastomosis.(ABSTRACT TRUNCATED AT 400 WORDS)