Adaptation to jejunoileal bypass promotes experimental colorectal carcinogenesis

Case report: Case series featuring anastomotic colonic adenocarcinoma following jejunoileal bypass requiring oncologic resection and jejunoileal bypass reversal

Like all surgical fields, bariatric surgery has evolved immensely, so much so that previous procedures are now obsolete. For instance, the jejunoileal bypass has fallen out of favor after severe metabolic consequences resulted in prolonged morbidity and even mortality. Despite this, several patients persevered long enough to develop other pathology, such as cancer. This progression has been validated in animal models but not human patients. Nonetheless, contemporary surgeons may encounter situations where they must resect and re-establish intestinal continuity in patients with this antiquated anatomy. When faced with this scenario, the question of whether or not the previously bypassed small bowel can be safely reunited plagues the surgeon remains unanswered. Unfortunately, the literature does not effectively answer this question, even anecdotally through case reports or series. Therefore, we share our experience with three patients who developed colon cancer following jejunoileal bypass and subsequently underwent oncologic resection with simultaneous reversal of their jejunoileal bypasses.

The impact of bariatric surgery on colorectal cancer risk

Obesity is considered a risk factor for different types of cancer, including colorectal cancer (CRC). Bariatric surgery has been associated with improvements in obesity-related co-morbidities and reductions in overall cancer risk. However, given the contradictory outcomes of several cohort studies, the impact of bariatric surgery on CRC risk appears controversial. Furthermore, measurement of CRC biomarkers following Roux-en-Y gastric bypass (RYGB) has revealed hyperproliferation and increased pro-inflammatory gene expression in the rectal mucosa. The proposed mechanisms leading to increased CRC risk are alterations of the gut microbiota and exposure of the colorectum to high concentrations of bile acids, both of which are caused by RYGB-induced anatomical rearrangements. Studies in animals and humans have highlighted the similarities between RYGB-induced microbial profiles and the gut microbiota documented in CRC. Microbial alterations common to post-RYGB cases and CRC include the enrichment of pro-inflammatory microbes and reduction in butyrate-producing bacteria. Lower concentrations of butyrate following RYGB may also contribute to an increased risk of CRC, given the anti-inflammatory and anticarcinogenic properties of this molecule. Laparoscopic sleeve gastrectomy appears to have a more moderate impact than RYGB; however, relatively few animal and human studies have investigated its effects on CRC risk. Moreover, evidence regarding the impact of anastomosis gastric bypass on one is even more limited. Therefore, further studies are required to establish whether the potential increase in CRC risk is restricted to RYGB or may also be associated with other bariatric procedures.

COULD THE INTESTINAL EPITHELIAL ALTERATIONS PROMOTED BY ROUX-EN-Y GASTRIC BYPASS EXPLAIN HIGHER TENDENCY FOR COLONIC DISEASES IN BARIATRIC PATIENTS?

BACKGROUND

Ki-67 in ascending colon: A) experiment and B) control. Intestinal diversions have revolutionized the treatment of morbid obesity due to its viability and sustained response. However, experimental studies suggest, after these derivations, a higher risk of colon cancer.

AIM

To analyze the histological and immunohistological changes that the jejunojejunal shunt can produce in the jejunum, ileum and ascending colon.

METHOD

Twenty-four male Wistar rats were randomly divided into two groups, control (n=12) and experiment (n=12) and subdivided into groups of four. Nine weeks after the jejunojejunal shunt, segmental resection of the excluded jejunum, terminal ileum and ascending colon was performed. Histological analysis focused on the thickness of the mucosa, height of the villi, depth of the crypts and immunohistochemistry in the expression of Ki-67 and p53.

RESULTS

Significant differences were found between the experiment and control groups in relation to the thickness of the mucosa in the jejunum (p=0.011), in the ileum (p<0.001) and in the colon (p=0.027). There was also a significant difference in relation to the height of the villus in the ileum (p<0.001) and the depth of the crypts in the jejunum (p0.001). The results indicated that there is a significant difference between the groups regarding the expression of Ki-67 in the colon (p<0.001). No significant differences were found between the groups regarding the expression of Ki-67 in the jejunum and ileum. In the P53 evaluation, negative nuclear staining was found in all cases.

CONCLUSION

The jejunojejunal deviation performed in the Roux-in-Y gastrojejunal bypass, predispose epithelial proliferative effects, causing an increase in the thickness of the mucosa, height of the villi and depth of the crypts of the jejunum, ileum and ascending colon.

Gastro-Intestinal Tract Cancers Following Bariatric Surgery: a Narrative Review

The association between obesity and malignancies has been identified epidemiologically. Meanwhile, the increasing global number of bariatric surgeries is reported annually; bariatric surgery's effect on different types of cancers is not well understood. Unfortunately, nonspecific presentations and difficulties regarding investigations make diagnosis challenging. The aim of this study is to compile available data about gastro-intestinal (GI) cancers, occurring after different bariatric surgeries. Although GI cancers are considered a rare complication of obesity surgery, they do exist, and diagnosis needs a high index of suspicion.

Biomarkers of Colorectal Cancer Risk Decrease 6 months After Roux-en-Y Gastric Bypass Surgery

PURPOSE

The impact of weight loss on obesity-related colorectal cancer (CRC) risk is not well defined. Previous studies have suggested that Roux-en-Y gastric bypass (RYGB) surgery may have an unexpected adverse impact on CRC risk. This study aimed to investigate the impact of RYGB on biomarkers of CRC risk.

MATERIALS AND METHODS

Rectal mucosal biopsies and blood were obtained from patients undergoing RYGB (n = 22) and non-obese control participants (n = 20) at baseline and at a median of 6.5 months after surgery. Markers of systemic inflammation and glucose homeostasis were measured. Expression of pro-inflammatory genes and proto-oncogenes in the rectal mucosa was quantified using qPCR. Crypt cell proliferation state of the rectal mucosa was assessed by counting mitotic figures in whole micro-dissected crypts.

RESULTS

At 6.5 months post-surgery, participants had lost 29 kg body mass and showed improvements in markers of glucose homeostasis and in systemic inflammation. Expression of pro-inflammatory genes in the rectal mucosa did not increase and COX-1 expression fell significantly (P = 0.019). The mean number of mitoses per crypt decreased from 6.5 to 4.3 (P = 0.028) after RYGB.

CONCLUSION

RYGB in obese adults led to lower rectal crypt cell proliferation, reduced systemic and mucosal markers of inflammation and improvements in glucose regulation. These consistent findings of reduced markers of tumourigenic potential suggest that surgically induced weight loss may lower CRC risk.

Colon adenocarcinoma after jejunoileal bypass for morbid obesity

Jejunoileal bypass (JIB) was developed as a surgical treatment for morbid obesity in the early 1950s. However, this procedure is now known to be associated with multiple metabolic complications and has subsequently been abandoned as a viable bariatric procedure. Some of these known complications include renal stone formation, liver failure, migratory arthritis, fat-soluble deficiencies, blind-loop syndrome and severe diarrhea. Additionally, there have been animal models suggesting colon dysplasia after JIB. To our knowledge however, in humans, no colon cancers have been attributed to JIB in the literature. Here we report a 63-year-old morbidly obese female who had a JIB surgery in 1973 and subsequently was found to have numerous sessile colonic polyps throughout her colon and adenocarcinoma of the ascending colon without any family history of colonic polyposis syndromes or colon cancer.

The jejunoileal bypass provokes morphological changes in the large intestine? An experimental study in rats

PURPOSE

To analyse histopathological alterations characterized by the mitotic index in the mucosa of the large intestine in Wistar rats submitted to jejunoileal bypass operation after continued administration of sodium nitrite and vitamin C to different groups.

METHODS

Eighty male Wistar rats were employed and separated into 12 groups. In the control group (20 rats): five animals ingested only water; five animals received vitamin C; five animals received sodium nitrite and five received sodium nitrite + vitamin C. In the sham group (20 rats), the animals were anesthetized and underwent midline laparotomy and only intestinal manipulation was performed: five animals ingested only water; five animals received vitamin C; five animals received sodium nitrite and five received sodium nitrite + vitamin C. In the operated group 40 rats underwent a jejunoileal bypass surgery: ten animals ingested only water; ten animals received vitamin C; ten animals received sodium nitrite and ten received sodium nitrite + vitamin C. The mean weight of the animals was measured weekly. The large intestine was subdivided into cecum (S1), ascending colon (S(2)), transverse colon (S(3)), descending colon (S(4)) and rectum (S(5)) for histopathological analysis and mitotic counts. The statistical analysis was used to compare the mitotic indices. The level of significance was 5%.

RESULTS

The mean of all the segments indicates that the sodium nitrite+vitamin C group obtained the lowest mitotic index compared to the other treatments in the control group. The segments S(1) and S(2) showed a statistical difference with the vitamin C treatment: a higher mitotic index and better preservation of the mucosa in the operated group. In the sham group the main statistical difference occurred only in the sodium nitrite+vitamin C group between the means of the segments.

CONCLUSIONS

The comparison of all the colonic segments of the various groups revealed a lower mitotic index in the animals treated with sodium nitrite+vitamin C. In addition, it was found that vitamin C did not present a statistically significant inhibiting effect on the preservation of the mucosa and the mitotic index.

Novel goblet cell gene related to IgGFcgammaBP is regulated in adapting gut after small bowel resection

The loss of functional small bowel surface area leads to a well-described adaptive response in the remnant intestine. To elucidate its molecular regulation, a cohort of cDNAs were cloned using a rat gut resection model and subtractive/differential hybridization cloning techniques. This study reports a novel cDNA termed "ileal remnant repressed" (IRR)-219, which shares 80% nucleotide identity with the 3'end of a human intestinal IgG Fc binding protein (IgGFcgammaBP) and is homologous to human and rat mucins. IRR-219 mRNA is expressed in intestine and colon only. At 48 h after 70% intestinal resection, mRNA levels decreased two- to fivefold in the adaptive small bowel but increased two- to threefold in the colon. Expression of IRR-219 was suppressed in adaptive small bowel as late as 1 wk after resection. IRR-219 expression is also regulated during gut ontogeny. In situ hybridization revealed IRR-219 expression in small intestinal and colonic goblet cells only. Its unique patterns of expression during ontogeny and after small bowel resection suggest distinctive roles in small bowel and colonic adaptation.

Experimental models of colorectal cancer

PURPOSE

A review of in vivo and in vitro models of colorectal cancer is presented.

METHODS

A retrospective literature review was performed with reference to CD-ROM Medline and Index Medicus.

RESULTS

A comparison of the advantages and disadvantages of the models is presented in addition to a summary of individual model methodology and applications.

CONCLUSIONS

Such models are a useful adjunct for surgical research in colorectal oncology.

Does the colon adopt small bowel features in a small bowel environment?

BACKGROUND

Isoperistaltic colon interposition is one of several surgical options available in the treatment of short bowel syndrome. It functions primarily by slowing the rapid intestinal transit that follows small bowel resection (SBR). Previous studies have interposed distal colonic segments and although there is evidence of adaptation by the interposed colon it is not known whether these segments develop histologic or functional small bowel characteristics.

METHODS

In this study evidence was sought of metaplasia in the interposed segments after 80% SBR and, because proximal colon is a midgut derivative, the differences between proximal and distal colonic segments were examined.

RESULTS

There was no qualitative histological evidence of metaplasia by the interposed segments. There was a significant increase in crypt depth, mucosal thickness and maltase concentration of the interposed segments compared with the nontransposed colon of the controls. The maltase concentations were increased to the extent that they were not significantly different from the concentration present in normal ileum.

CONCLUSIONS

Although there was no gross evidence of small bowel intestinalization by the interposed segments, there was evidence of adaptation which was not merely an extension of the adaptive process seen after SBR alone. These changes resulted in the colon taking on some small bowel features. There was no significant difference between proximal vs distal interposed segments.

Effect of calcium supplementation on rectal epithelial hyperproliferation in intestinal bypass subjects

BACKGROUND/AIMS

Fatty acids and bile acids are tumor promoters of experimental colon cancer in rats. Calcium can inhibit their effects. After intestinal bypass (IB), fecal bile acid and lipid levels increase markedly. In rats, IB increases colonic cell proliferation and carcinogen-induced colon tumor incidence. Whether fecal bile acids and lipids influence rectal epithelial proliferation in humans is uncertain. This study compared rectal epithelial proliferation in IB subjects and in controls matched for age, sex, and body mass index and investigated the effects of calcium carbonate supplementation (2400 or 3600 mg Ca2+/day for 12 weeks) on proliferation indices in IB subjects.

METHODS

Epithelial proliferation was studied by in vitro incubation of rectal biopsy specimens with [3H] thymidine. Twenty-four-hour stool collections were assayed for bile acids, lipids, and calcium.

RESULTS

Whole crypt labeling index (LI) and upper crypt LI were increased in IB subjects compared with controls (P < 0.005). Calcium reduced whole crypt LI by 38% (P < 0.001) and upper crypt LI by 56% (P < 0.05). Levels of fecal bile acids (4.5 mmol/day) and lipids (131.9 g/day) were markedly elevated in IB subjects (P < 0.005).

CONCLUSIONS

IB induces rectal hyperproliferation and expansion of the proliferative zone in association with excessive output of fecal bile acids and lipids. Oral calcium reverses the proliferative changes.

Problems with intestinal lengthening

The surgical problems encountered in treating three infants with short-bowel syndrome are reported. The two survivors demonstrate many of the problems associated with the very short-bowel syndrome and both are dependent on parenteral nutrition despite undergoing intestinal lengthening.

Inhibitory effect of a cholecystokinin antagonist on pancreatic carcinogenesis after pancreatobiliary diversion

The role of cholecystokinin (CCK) has been explored in pancreatic carcinogenesis following pancreatobiliary diversion (PBD), using the specific CCK receptor antagonist CR-1409. Male Wistar rats (n = 80) weighing 70-100 g were given weekly i.p. injections of azaserine (30 mg kg-1 week-1) for 3 consecutive weeks. One week later animals were randomised to receive either PBD or sham PBD and thereafter to receive s.c. injections of either saline or CR-1409 (10 mg kg-1 day-1, 5 days a week). Six months after operation surviving rats were killed as follows: sham + saline 20, PBD + saline 19, sham + CR-1409 14, PBD + CR-1409 11. Cardiac blood was taken for CCK assay and the pancreas was excised for wet weight measurement and quantitative estimation of atypical acinar cell foci (AACF), the precursor of carcinoma. PBD reduced median body weight (3-20% less than shams) but trebled the absolute and relative pancreatic weights (P < 0.001). CR-1409 blunted this adaptive response to PBD, reducing absolute pancreatic weight by 35% (P < 0.005). PBD quadrupled circulating CCK concentrations, regardless of the antagonist treatment. Acidophilic AACF occurred only in rats with PBD. CR-1409 markedly reduced the number of observed acidophilic AACF by 90% (P < 0.001) and the number of foci per pancreas by 93% (P < 0.001). Moreover, CR-1409 reduced the mean focal diameter of each lesion by 18% (P < 0.005), the mean focal volume by 58% (P < 0.05) and the percentage of pancreas occupied by acidophilic foci by 95% (P < 0.001). PBD enhances pancreatic carcinogenesis by causing hypercholecystokininaemia, and CR-1409 largely inhibits this enhancement.

Dietary calcium does not reduce experimental colorectal carcinogenesis after small bowel resection despite reducing cellular proliferation

It has been proposed that colorectal carcinogenesis is accompanied by increased mucosal cell proliferation and that the converse may also apply. To examine this thesis, the crypt cell production rate (CCPR) was measured in eight groups of rats (n = 187) that had received 1,2 dimethylhydrazine, 70% small bowel resection, supplemental dietary calcium, or a combination of these. Analysis of variance showed the following: (1) the CCPR decreased between the ileum and distal colon; (2) the CCPR decreased between 16 and 32 weeks; (3) 1,2 dimethylhydrazine and small bowel resection increased the CCPR and calcium decreased the CCPR independently of one another; (4) the CCPR interacted with 1,2 dimethylhydrazine x small bowel resection, calcium x 1,2 dimethylhydrazine and interacted between the site of bowel and calcium, 1,2 dimethylhydrazine, small bowel resection, and 1,2 dimethylhydrazine x small bowel resection (p = 0.014 to p < 0.001). The tumour yield was reduced by calcium in 1,2 dimethylhydrazine treated animals (chi 2 = 14.1, df = 3, p < 0.01) but was unaffected by calcium in 1,2 dimethylhydrazine and small bowel resection treated animals despite significant differences in the CCPR. An increase of the CCPR both preceded and accompanied colorectal carcinogenesis but reduction of the CCPR was not invariably accompanied by reduced carcinogenes.

Duodenogastric reflux enhances growth and carcinogenesis in the rat pancreas

Surgery for peptic ulcer disease may increase the risk of pancreatic cancer. The effect of duodenogastric reflux on pancreatic carcinogenesis was tested, and changes in the circulating levels of cholecystokinin (CCK) and gastrin were measured. Male Wistar rats (n = 40) weighing 250-300 g were randomized to undergo gastrotomy (control) or split gastrojejunostomy (to produce complete duodenogastric reflux) and then to receive azaserine (30 mg/kg/week intraperitoneally) or saline injections for 3 weeks. At 6 months, blood CCK was assayed and the pancreas was excised for quantitative estimation of atypical acinar cell foci (AACF), the precursor lesions of carcinoma. Rats that had undergone split gastrojejunostomy weighed 15-19 per cent less than controls (P < 0.05), but their relative pancreatic weight (mg pancreas per 100 g body-weight) was 52-60 per cent greater (P < 0.001). Acidophilic AACF occurred only in azaserine-treated rats with duodenogastric reflux. Although plasma CCK concentrations were unchanged, split gastrojejunostomy increased basal and postprandial gastrin levels by 98-175 per cent (P < 0.05). Duodenogastric reflux produces sustained hypergastrinaemia and promotes experimental pancreatic carcinogenesis.

Colorectal cancer risk after jejunoileal bypass: dysplasia and DNA content in longtime follow-up of patients operated on for morbid obesity

Jejunoileal bypass (JIB) has been a widespread operation for treatment of morbid obesity. Bile acids are regarded as cofactors in the carcinogenesis of the colon, and, since intestinal bypass involves increased exposure of bile acids to the large intestinal mucosa, JIB has been postulated to increase the risk for colorectal carcinoma. In experimental studies on animals, the results have indicated an increased frequency of induced carcinomas, but in clinical series only one patient with colon carcinoma has been reported. Thirty women, operated on with JIB 11 to 17 years earlier, were examined by colonoscopy with multiple biopsies, systematically taken for histologic evaluation and flow cytometric DNA analysis. In only one patient, low-grade dysplasia was detected in an initial adenomatous lesion but was not visible macroscopically. No DNA aneuploidy was found. In a control group of 11 patients examined for non-neoplastic disease, neither dysplasia nor aneuploidy was diagnosed. Within 17 years postoperatively, we have, by these methods, not been able to verify any colorectal malignant transformation in patients operated on with JIB. However, since carcinogenesis is a long process, further surveillance will be demanded before an increased risk for colorectal carcinoma can be excluded.

Paediatric emergencies

During the last decade neonatal surgical results have improved considerably. Except for infants born with serious congenital heart disease, diaphragmatic hernia or exomphalos, postoperative mortality rates for infants with single anomalies have fallen to the region of 10%. This dramatic success story has been marred by a corresponding increase in the number of individuals with several anomalies entering late childhood with severe chronic handicaps. During the remainder of this century much effort will be expended in devising programmes of investigation which will attempt to predict which individuals will have a poor long-term prognosis. Such programmes will necessitate very close liaison between obstetricians, radiologists, neonatologists, local paediatricians, paediatric surgeons, general practitioners and parents. Very urgent surgery is necessary for the best results in infants with gastroschisis, intestinal volvulus and irreducible inguinal hernia, but for most other conditions there have been recent trends away from very urgent surgery to operation during daylight hours within the ensuing 24 h. Surgery within a few hours of presentation is necessary for intussusception and for early acute appendicitis, but perforated appendicitis should be treated by aggressive fluid replacement and intravenous antibiotics and surgery should be contemplated only in the rare cases of continued deterioration.

Neonatal small bowel atresia, stenosis and segmental dilatation

In 8 years, 44 neonates were treated for small bowel atresia, stenosis or segmental dilatation by one surgical team. There was a single lesion in 30 infants and 14 had two or more sites of intestinal obstruction. Associated gastrointestinal abnormalities were found in 23 (52 per cent) patients. Resection of the atresia(s) and primary anastomosis were performed in 34 infants and staged procedures were carried out in ten patients with complicated lesions. Patients undergoing staged procedures had a higher complication rate than those having primary repair (six out of ten and 11 out of 34 respectively). The overall initial survival rate was 93 per cent, rising to 100 per cent in those without associated anomalies or prenatal complications, but more than a quarter (27 per cent) of survivors have long-term disabilities.

Experimental colonic carcinogenesis after gastric surgery

Peptic ulcer surgery may predispose to the subsequent development of colorectal cancer. This experimental study has investigated the effects of gastric operations on colonic cell proliferation, bile acid excretion and carcinogenesis. Male Sprague-Dawley rats (n = 105) underwent sham operation, Pólya partial gastrectomy or vagotomy and pyloroplasty. The carcinogen azoxymethane was administered weekly for 6 weeks thereafter (total dose 60 mg kg-1). When the animals were killed 24 weeks after operation, colons were examined for mucosal mass, crypt cell production rate (CCPR) and tumour yield; faeces were assayed for contents of neutral steroids and bile acids (both total and individual). Morphometric indices and mucosal DNA content were similar in all three groups. Pólya gastrectomy reduced: (1) CCPR throughout the colon (by 42-65 per cent, P less than 0.002); (2) the number of rats with colorectal tumours (26 per cent versus 63 per cent, P less than 0.05); (3) faecal levels of neutral steroids and bile acids, notably hyodeoxycholic acid (P less than 0.01). Although vagotomy and pyloroplasty increased caecal CCPR, there were no consistent differences in faecal steroids and no alteration in tumour yield after the operation. These results fail to support clinical studies suggesting that gastric surgery predisposes to colonic carcinogenesis. Indeed, Pólya partial gastrectomy exerts a protective effect, probably by inhibiting colonic cell proliferation.

Effect of defunction on cytokinetics and cancer at colonic suture lines

An intestinal suture line potentiates experimental carcinogenesis in its vicinity, probably due to adaptive hyperplasia. By contrast, a defunctioning colostomy causes distal hypoplasia, and fewer tumours develop. Male Sprague-Dawley rats (n = 160) were used to study adaptation (assessed by a stathmokinetic technique) and carcinogenesis (induced by azoxymethane) at an end-to-end anastomosis that was raised in either functioning or defunctioned left colon. Controls had no procedure and other rats had proximal colostomy alone. Defunction had a profound antitropic effect on the colon, reducing bowel length and weight and crypt cell production rate (CCPR) by 22-56 per cent. Anastomotic CCPR was increased by a factor of 2.6 over controls: mean(s.e.m.) values of 12.71(2.85) versus 4.87(0.41) cells/crypt/h (P less than 0.01), but defunction reduced this by 76 per cent to a mean(s.e.m.) value of 3.00(0.52) cells/crypt/h below that in the intact colon. In the left colon, 39-50 per cent of tumours were sited at the anastomosis. Compared with controls there were 77 per cent fewer tumours in defunctioned colon, but they still favoured the site of anastomosis. Neoplasms at the colostomy site accounted for 74-77 per cent of all right-sided tumours. Anastomosis and defunction have powerful but contrasting effects on colonic adaptation and carcinogenesis; when combined they tend to cancel each other out.

Rectal hyperplasia after jejunoileal bypass for morbid obesity

Jejunoileal bypass (JIB) has been widely used to treat patients with morbid obesity for the past 20 years. In rats JIB causes adaptive colonic hyperplasia and enhances colorectal neoplasia. In this study crypt cell production rate (CCPR) was measured stathmokinetically in cultured rectal biopsies from nine patients with JIB and seven controls without intestinal operations or disease. Crypt cell production rate in the group with JIB was more than double that of controls (12.80 (2.67) v 6.23 (1.49) cells/crypt/h: p less than 0.001). There were no significant differences in crypt morphometry and histological examination of rectal biopsies was normal. Patients with JIB have a marked and persistent increase in cell proliferation in the large intestine and may be at increased risk of developing colonic cancer.

Inhibition of intestinal carcinogenesis by dietary supplementation with calcium

Dietary supplementation with calcium reduces colonic crypt cell production rates in both normal and hyperplastic mucosa. Calcium can bind intraluminally with bile salts and fatty acids thus reducing their mitogenic effect. The protective role of oral calcium on intestinal carcinogenesis (induced by azoxymethane) was tested in 60 male Sprague-Dawley rats submitted to either 80 per cent mid jejuno-ileal resection (n = 30) or jejunal transection (n = 30). Half the rats in each group received calcium lactate 24 g/l added to their drinking water. Rats were killed 25-27 weeks postoperatively. Enterectomy increased colonic tumour yield by 60-106 per cent (P = 0.002-0.005) and duodenal tumour yield by 70-86 per cent. Calcium abolished this effect at both sites, halving intestinal tumour yields in rats with both transection and resection (P less than 0.05). Doubling the dietary intake of calcium inhibits experimental carcinogenesis.

Elevated plasma enteroglucagon alone fails to alter distal colonic carcinogenesis in rats

The effect of physiologic increases of plasma enteroglucagon, induced by massive bypass or resection of small bowel, on large bowel cell turnover and carcinogenesis was studied in rats in which the distal colon was isolated as a mucous fistula. After injections of azoxymethane, either 85% end-to-side jejunoileal bypass, 85% jejunoileal resection, or sham bypass was performed. Controls underwent colonic transection and resuture, azoxymethane treatment, and then sham bypass. Thirty weeks later the plasma enteroglucagon level had almost trebled after jejunoileal bypass (p less than 0.001) and almost doubled after jejunoileal resection (p less than 0.002) when compared with sham bypass; sham values did not differ from controls. The median number of tumors per rat in the distal (defunctioned) colon fell from 2 to 0 (p less than 0.05). Segmental weight fell by 45% (p less than 0.001) and crypt cell production rate by 75% (p less than 0.001). Neither tumor yield nor adaptation was affected by jejunoileal bypass or jejunoileal resection. Plasma enteroglucagon has no effect on colonic cell turnover or carcinogenesis in the absence of luminal content.

Augmentation of chemically induced pancreatic and bronchial cancers by epidermal growth factor

The incidence of Syrian golden hamsters with pancreatic cancer induced by subcutaneous injections of N-nitroso-bis(2-oxopropyl)amine for 19 weeks (each 10 mg/kg) increased from 44% to 75% (p=0.016) when epidermal growth factor was also administered from week 5 through week 8 (5 mug energy three days for injections). Epidermal growth factor increased pancreatic weight and body weight. The incidence of animals with bronchial cancer doubled. Epidermal growth factor could be a cocarcinogen as a result of its mitogenic activity.

Dysplasia of the colon after jejuno-ileal bypass

Colonoscopic biopsies were performed on 38 patients, 10-13 years after jejuno-ileal bypass. No significant dysplasia or premalignant change was seen in 371 biopsies. In one patient two tubulovillous adenomata were found in an otherwise normal colon, which is likely to be a chance finding. Although it will take another 10-20 years to establish whether jejuno-ileal bypass is associated with an increased risk of large bowel cancer in humans, there is at present no indication for regular colonoscopic surveillance.

Increase of the mitotic index of colonic mucosa after cholecystectomy

This study was undertaken to assess possible modifications of the proliferative activity of colonic mucosa, which could be related to a suggested cancer-promoting role of cholecystectomy. The mitotic index (number of mitoses per 1000 gland cells) was evaluated in the colonic mucosa of 14 healthy subjects, 11 patients with cholelithiasis, before and 6 months after surgery, and 10 patients who had undergone cholecystectomy 2 or more years previously. The mitotic index of cholecystectomized patients was significantly higher than controls. It rose significantly within 6 months of cholecystectomy. The mitotic index of patients with cholelithiasis before surgery was similar to controls. These data suggest that cholecystectomy is followed by an enhancement in the proliferative activity of the colonic mucosa, which could play a cancer-promoting role.

Distal transposition of rat caecum does not render it susceptible to carcinogenesis

As the relative resistance of rat caecum to chemical carcinogens could reflect its luminal environment, caecal mucosa was exposed to the distal faecal stream in male Sprague-Dawley rats (n = 50) previously treated with azoxymethane (total dose 90 mg/kg sc). After colonic transection at the pelvic brim, the caecum was inserted isoperistaltically between colocaecal and caecorectal anastomoses (n = 30); an ileocolic anastomosis restored intestinal continuity. Controls (n = 20) had transection and reanastomosis at equivalent points of the bowel, plus caecotomy and resuture. Caecal crypt cell production rate, as determined stathmokinetically at 28 weeks, was not consistently affected by transposition. No tumors developed in either transposed or orthotopic caecum, apart from three suture-line tumours found at the caecotomy site in controls. The colonic tumour yield in controls (1.4 +/- 0.3 per rat : mean +/- SEM) matched that after transposition (1.5 +/- 0.2), but anastomotic tumours were twice as common after transposition (p less than 0.05) and rectal tumours were increased four-fold (p less than 0.05). The caecum remains resistant to carcinogenesis despite transposition to a distal colonic environment. Local epithelial defence mechanisms are more important than luminal contents in maintaining this resistance.

Transplantation of a segment of ileum to the external abdominal wall: an animal model of intestinal mucosal hyperplasia

When a segment of small intestine is transplanted to the external abdominal wall in rats adaptive changes occur in the exposed mucosa. These probably represent an extreme example of a physiological response to one type of trophic influence--the effect of mechanical trauma. The nature of the changes has been studied at 7 weeks after externalization using simple morphometry and a number of cytokinetic techniques (thymidine labelling, vincristine-induced metaphase arrest and the fraction-of-labelled-mitoses method), and comparisons drawn with the normal ileum. The exteriorized mucosa showed marked villus atrophy and hyperplasia of the crypts to three times normal size as a result of increases both in crypt length and crypt circumference. Neither metaplastic nor dysplastic epithelial abnormalities were observed. Crypt-cell production rate doubled in the hyperplastic crypts due to an increase in the size of the proliferation zone within the crypt, and the distribution of proliferating cells within the crypt changed. But cell cycle times were prolonged and more maturing cells were retained in the hyperplastic crypts. The potential usefulness of this model, particularly in carcinogenicity studies is considered.

Goblet cell changes during intestinal adaptation to azoxymethane and enteric bypass in the rat

Numbers of intestinal goblet cells containing specific acid mucins were determined in male Sprague-Dawley rats receiving azoxymethane (total dose 90 mg kg-1) with or without jejunoileal bypass (JIB). Controls had injections of vehicle and sham bypass. Thirty weeks postoperatively colorectal length and crypt depth were increased by azoxymethane and further increased by JIB. JIB doubled the yield of intestinal tumours (P less than 0.01). Goblet cells containing sulphomucins normally predominated throughout the intestinal tract. Contents of sulphomucins and especially sialomucins were consistently higher in the small bowel and colon of rats receiving azoxymethane alone, but again the highest values were observed in animals with azoxymethane plus JIB. Both small-bowel bypass and azoxymethane stimulate adaptive growth of the colon and small bowel remaining in circuit. Goblet-cell hyperplasia is a feature of this response, and sialomucins are preferentially secreted by the adapting epithelium.

Relative effects of ileal resection and bypass on intestinal adaptation and carcinogenesis

Since ileal resection and ileal bypass are commonly performed in man and might stimulate colonic hyperplasia, their co-carcinogenic potential was explored in male Sprague-Dawley rats (n = 135). One week after 33 per cent distal small-bowel resection, 33 per cent distal small-bowel bypass or distal ileal transection (control), animals started a 6-week course of azoxymethane injections (total dose 90 mg/kg ip). Findings in rats killed at 20 and 25 weeks were similar: bypass produced a higher yield of colorectal tumours (4.0 +/- 0.6 per rat: mean +/- s.e.) than controls (2.4 +/- 0.4; P less than 0.05), but resection caused maximal enhancement (5.2 +/- 0.5: P less than 0.01). In rats killed at 30 weeks, however, tumour yields were almost identical. Overall, resection increased colonic tumour yield by 55 per cent (P less than 0.02) and bypass by 32 per cent. Stathmokinetic measurements of crypt cell production rate (CCPR) at 20 weeks showed similar increases after resection and bypass both in residual functioning small bowel (109-200 per cent: P less than 0.01) and in colorectum (63-100 per cent: P less than 0.05). At 30 weeks these adaptive effects persisted, despite an overall increase in CCPR with age. Loss of functioning ileum enhances experimental colorectal carcinogenesis principally by reducing the latent period for tumour development. Resection has a greater effect than bypass probably by producing earlier hyperplasia, though later adaptive effects are similar.