Cystic fibrosis (CF) is a multisystem disorder that arises as a consequence of a qualitative or quantitative defect in the gene product of ABCC7—the cystic fibrosis transmembrane regulator (CFTR) protein (1,2). More than 1500 disease-associated mutations have been described to date (3). Cystic fibrosis transmembrane regulator protein is a chloride and bicarbonate channel, which also regulates or influences other facets of cell function in epithelial and nonepithelial tissues (4). Recent evidence suggests that CF-associated mutations are inherently proinflammatory (5–8) and that gastrointestinal inflammation may be an intrinsic feature of CF (9).
Meconium ileus (MI) and distal ileal obstruction syndrome (DIOS) are forms of subacute intestinal obstruction encountered either at birth (MI) or in later childhood (DIOS) in individuals with CF (10,11). Meconium ileus affects approximately 15% of infants with CF. Forty percent of affected infants have complicated MI in which the disease is accompanied by neonatal volvolus, perforation, or atresia (12,13), and overall 78% require neonatal surgical intervention. The cause of MI/DIOS has often been attributed to suboptimal intralumenal digestion/hydration leading to inspissation of luminal contents. Meconium ileus occurs in the absence of pancreatic insufficiency (14), although such individuals will have impaired bicarbonate secretion (15). Fibrosis and inflammation of the small and large intestine is described in CF (16,17). Leiomyositis and myenteric ganglionitis are the established causes of intestinal dysmotility (18–20), which, if present in CF, may exacerbate any tendency to subacute intestinal obstruction. We demonstrate here an association between transmural ileal inflammation and severe DIOS, which is histopathologically distinct from fibrosing colonopathy. We further document the presence of mild forms of such changes at birth in neonates with MI. These findings support the notion that transmural gastrointestinal inflammation is an intrinsic feature of CF, which is independent of pancreatic enzyme replacement therapy (PERT). The findings provide a rationale for anti-inflammatory treatment in children with refractory DIOS.
METHODS AND PATIENTS
We conducted a retrospective review of children with CF treated at Great Ormond Street Hospital between November 1995 and December 2001 who had either presented with MI requiring laparotomy and stoma formation or who had experienced severe or recurrent DIOS responding poorly to standard medical treatments (21). Six patients with DIOS were identified in whom full-thickness terminal ileal tissue had been obtained surgically and was available for further study. Seven patients with complicated MI who had undergone laparotomy at birth were identified, of which histological material was available in 6. Six infants with non-CF intestinal atresia were identified as controls.
Four micrometer-thick histological sections were re-cut and stained with haematoxylin and eosin (H&E). The inflammatory process was assessed and graded 0 (normal) to 4 (severe) in the mucosa, submucosa, muscularis propria, myenteric plexus, and serosa. The prominent inflammatory cell types were noted, and the presence of submucosal and subserosal fibrosis were recorded. Inflammatory infiltrates were characterized by immunohistochemistry using monoclonal antibodies against CD45ro (UCHL1, 1:200; Dako, Glostrup, Denmark) that react with primed or memory T cells, the anti-pan T cell marker CD3 (1:50; Novocastra, Newcastle, UK), the anti-helper/inducer T cell marker CD4 (1:50; Novocastra), and CD8, a marker for suppressor/cytotoxic T cells (1:100; Dako). The integrity of the muscularis and characterization of mesenchymal cell phenotype were assessed by immunostaining using monoclonal antibodies against α-smooth muscle actin (1:2000; Dako) (SMA), desmin (1:100; Dako) (D), and vimentin (1:40; Dako) (V). Fibroblasts were considered to be SMA− D− V+ and myofibroblasts SMA+ D+ V−. Immunostaining using a monoclonal anti-neurofilament antibody (1:120; Eurodiagnostics, Apeldoorn, the Netherlands) was used to assess the integrity of neural elements. In addition, a monoclonal HLA-DR antibody (1:2000; Dako) was used to look for upregulation of antigen presentation. Antigen retrieval was achieved by pressure cooking for 4 minutes in citrate buffer for all antigens except smooth muscle actin and vimentin. Visualization was achieved using extravidin-biotin peroxidase detection system. Negative controls were performed for each specimen by omitting the primary antibody and positive controls using tonsillar tissue and, wherever appropriate, normal gut tissues.
Sections were examined by light microscopy independently and blinded by an experienced paediatric histopathologist and a paediatric gastroenterologist. The morphological change and the degree of inflammation were assessed systematically as described above.
Histological scoring of CF and control tissues were compared using Fisher exact test.
Archival antroduodenal manometry data were available from an infant who had experienced neonatal MI studied using water-perfused catheters and a previously validated data acquisition and analysis system (18).
Six patients, 3 males and 3 females, ages 2 months to 15 years, were included in the study. Patients were either homozygotes (patients 1 and 6) or compound heterozygotes for the ΔF508 mutation (patients 2, 3, 4, and 5) (Table 1). Pancreatic exocrine insufficiency was present in all and PERT was prescribed for all (lipase dose equivalent to 1000–20,000 IU · kg−1 · day). All had presented with symptoms/signs compatible with intestinal obstruction including abdominal pain and bilious vomiting. Plain abdominal radiograph demonstrated dilated proximal intestinal loops in 6 of 6. None had improved with conservative medical management (22).
Three patients had an ill-defined ileal mass with a degree of ileal stricturing and underwent hemicolectomy (patients 1, 4, and 6); 3 had an ileostomy fashioned without intestinal resection. Full-thickness terminal ileal tissue was taken at the time of surgery in all cases. None had radiological or pathological evidence of colonic stricture.
Mucosal inflammation of differing intensity was present in all 6 cases (grades 1–3). Lymphocytes were the most prominent component, although neutrophils and eosinophils were also seen. Ulceration of the surface epithelium was present in 4 of 6 patients. An increase in intraepithelial lymphocytes (3/6) and intraepithelial neutrophils/eosinophils (5/6) was apparent. Cryptitis of varying degrees was present in all patients, and crypt abscesses were seen in 2 of 6. Cellularity of the submucosa, muscularis propria, myenteric plexus, and serosa was increased (Fig. 1A–D, Table 2).
The scores “0 or 1” in Table 2 reflect the patchy nature of these increases. Overt lymphocytic ganglionitis was present in 4 of 6 specimens (Fig. 2A and B). Mild submucosal fibrosis was present in 5 of 6.
No data are available on patient 3 because of insufficient tissue within the tissue archive. Lymphocytes were seen in the myenteric plexus in 3 of 5. Numbers of myenteric neurons were not decreased in any of the samples and neurofilament staining was unremarkable in all sections. Chronic myositis of the muscularis propria, which was particularly obvious on immunostaining with UCLH1 was present in 5 of 5 (Fig. 2C).
HLA-DR staining was possible in 4 of 5 patients for whom adequate tissue was available. HLA-DR positivity was exhibited by surface epithelial cells and immunocytes in 4 of 4, by blood vessels within the submucosa and serosa in 3 of 4 and the muscularis propria in 4 of 4 (Fig. 2D). HLA-DR positive immunocytes were detected in the myenteric plexus in 3 of 4.
No abnormality was detected in smooth muscle actin and desmin immunostaining of the myocytes of the muscularis propria. Four out of five patients had evidence of myofibroblastic transformation of fibroblasts (positivity for both smooth muscle actin and desmin and negativity for vimentin) in the submucosa and serosa (Fig. 3A and B). In the submucosa, these cells appeared to be located luminal to the circular muscle. In patient 2, these were particularly prominent in the vicinity of the submucosal blood vessels. Data are summarized in Table 2.
Antroduodenal manomerty was not performed routinely in any member of the cohort of children described in the present study. However, such data were available to us from our archive of motility studies performed in children investigated at Great Ormond Street Hospital (performed by W.M.B.). One such tracing (Fig. 4) of a 13-month-old child who had experienced MI and had recurrent episodes of subacute intestinal obstruction has been shown. The tracing demonstrates contractile activity of normal frequency but reduced amplitude phase III activity of shortened duration and abnormal patterns of propagation/failure of propagation consistent with a neuropathic disturbance (18). Specific abnormalities included bursts of propagated 12 cycles per minute activity with amplitude approximately 20 cmH2O but duration of typically approximately 30 seconds. At times the frequency of contractile activity during phase III suddenly halved raising the possibility of a deficiency in myoelectrical coupling in this individual as has been described in adults with myenteric ganglionitis.
Of the neonates with complicated MI, 4 of 6 had a volvolus and 4 of 6 had antenatal intestinal perforation. Five of six carried the ΔF508 mutation on 1 or more alleles (Table 4). A 7-year-old patient (patient 5) had undergone a further intestinal resection following an intestinal volvolus. In this individual, ileum was studied from the second resection and the initial (MI) resection. Only “healthy” tissues most distant from the perforation/volvolus were scored histologically.
Mucosal inflammation extending into submucosal tissues was present universally in all CF resection specimens. Mucosal inflammation was present in 2 of 6 non-CF atresia specimens, extending mildly (grade 1/4) into the submucosa in 1 of 6. Transmural inflammation was present in 3 of 6, myenteric ganglionitis in 2 of 6 and submucosal fibrosis in 6 of 6 (Table 5). Submucosal inflammation and fibrosis, as seen in DIOS ilea, was a characteristic of MI tissues not seen in non-CF atresias.
Myofibroblastic transformation of fibroblasts (positivity for both smooth muscle actin and desmin and negativity for vimentin) was again prominent in the submucosa of CF tissues (5/6 patients) and uncommon in non-CF tissues (1/6) (Fig. 3C and D). CD45ro positivity (UCHL1 antibody) within the submucosa was a feature of CF tissues (6/6 CF tissues vs weakly in 1/6 non-CF atresias) (Table 6). The combined finding of submucosal myofibroblast proliferation and submucosal DC45ro positivity was highly predictive of CF. These findings are similar to those seen in DIOS tissues.
The features apparent in patient 5m at birth were still present at the age of 7 years when a second ileal resection was performed (Table 7). By this age, the transmural lymphocyte predominant imflammatory process apparent in individuals with DIOS and in 1 of 6 patients with MI at birth (patient 2m) was obviously apparent.
DIOS is probably a multifactorial syndrome, which is the end result of a number of processes to which children with CF are predisposed. Although there has been a reduction in incidence since the introduction of more efficacious microsphere enzyme replacement therapies (23), it seems unlikely that it is simply due to inspissation of incompletely digested and hydrated intestinal luminal contents. In keeping with this is the observation that it occurs in both pancreatic-sufficient and pancreatic-insufficient individuals (14,24). MI is positively associated with the ΔF508 genotype and negatively associated with G551D (25). Both ΔF508 and G551D have similar net deleterious effects on CFTR-mediated chloride currents and in this respect are severe phenotypes. This discordance for MI suggests that factors other than chloride currents are important in the genesis of MI. Individuals with MI are at increased risk of developing DIOS in later life. The ΔF508 mutation activates NFκB, a proinflammatory nuclear transcription factor, to a greater extent than G551D, raising the possibility that DIOS is an inflammatory dysmotility syndrome (8).
Transmural ileal inflammation in individuals with CF has been recognized for a number of years (16,26). Myenteric ganglionitis and myositis are well-recognized causes of intestinal dysmotility and delayed intestinal transit in the absence of intestinal luminal stricture or distortion (18–20,27,28). We have demonstrated a lymphocyte predominant inflammatory process extending the full thickness of the bowel wall in 6 of 6 individuals with DIOS with evidence of lymphocytes myenteric ganglionitis in 4 of 6 patients. In contrast to lymphocytic ganglionitis with anti-neuronal antibodies (20), numbers of myenteric neurons are preserved in CF. Where ganglionitis is present in CF, it is part of a transmural CD45ro lymphocyte predominant inflammatory infiltrate. Similar, although less pronounced, findings are apparent at birth in infants with complicated MI, but not in non-CF atresias. GI motility is known to be altered adversely in individuals with CF (29), and it is not unreasonable to suppose that the transmural inflammatory process present from birth in individuals with CF may contribute to this and constitute an additional risk factor for the development of DIOS in later life.
Prominent myofibroblastic transformation in the submucosa seen in individuals with both DIOS and MI supports an inflammatory origin of the fibrotic reaction that is seen more prominently in children with DIOS. Precise definition of an activated or fibrogenic phenotype of intestinal mesenchymal cell may be difficult. We have used dual positivity for desmin (D) and α-smooth muscle actin (SMA) together with negativity for vimentin (V) as a marker for myofibroblasts (MF) (30–32). In normal intestine MF and fibroblasts in submucosa, serosa, and intermuscular connective tissue are the primary sites of collagen synthesis (31,33). V+/SMA−/D+ fibroblasts and V−/SMA+/D+ myofibroblasts are the major sites of collagen type 1 synthesis in Crohn disease (31). The myofibroblastic transformation and proliferation of mesenchymal cells in the submucosa of patients with CF is in keeping with the contemporary view that some types of chronic intestinal inflammation are able to cause muscularis overgrowth and a change in enteric smooth muscle phenotype towards a collagen-producing myofibroblast phenotype (31,32). Procollagen genes can be induced by fibrogenic cytokines such as transforming growth factor-β (TGF-β) (32). Abnormalities in the innate immune response, which are a consistent characteristic of CF epithelia (34,35), may also provide an inherently profibrogenic influence (36,37). Interstitial cells of Cajal (ICC), a myofibroblast related intestinal cell subtype which is important in the regulation of gastrointestinal motor activity, are capable of dedifferentiation into a collagen-producing fibroblast or myofibroblast phenotype in chronic transmural intestinal inflammatory conditions (30,38). In addition to promoting fibrosis, the fibroblastic transformation of ICC would be expected to adversely affect gastrointestinal motility.
That fibrosis may be an intrinsic feature of CF rather than a secondary event is illustrated by the observation that ileal fibrosis can be present at birth in infants with severe CF genotypes (39). Colonic fibrosis is recognized in CF within the context of the so-called fibrosing colonopathy (40). Pathological descriptions of fibrosing colonopathy allude to the finding (in the colon) of severe fibrosis of the submucosa, muscularis propria, and lamina propria, which is out of proportion to the mild degree of mucosal inflammation (41). Ileal involvement was either inconspicuous or absent in earlier descriptions of fibrosing colonopathy (40,42–45), although a more contemporary publication alludes to ileal involvement with fibrosis of the mucosa, submucosa, and muscularis propria, and infiltration of the mucosa with eosinophils, although not with lymphocytes (41). Our ileal histopathological findings are different from those described in association with fibrosing colonopathy. Theories concerning the genesis of fibrosing colonopathy, in particular whether it is related to the formulation or dose of pancreatic exocrine supplement, have been the subject of substantial, sometimes acrimonious, debate (17,46–52). Although the numbers of case reports of fibrosing colonopathy (53) have fallen since the introduction of guidelines that total daily dose of lipase should equate to <10,000 IU lipase per kilogram of body weight per day (54), our data and that of others (55) support the notion that intestinal fibrosis in CF need not necessarily be iatrogenic. The thickened bowel visible on abdominal ultrasound in individuals with CF (56,57) is also independent of both dose and formulation of enzyme replacement administered (58) and seems likely to represent a further manifestation of a chronic transmural inflammatory process. The observation of echogenic bowel in infants with CF in utero (57,59) and our findings of myofibroblastic proliferation in infants with CF at birth support the notion that this is an inherent feature of CF.
These observations support the hypothesis that intestinal fibrosis in CF is unrelated to PERT. They also provide an as yet unproven rationale for anti-inflammatory treatment(s) in individuals with early-onset CF-associated motility disturbances and anti-fibrotic therapies to alter the natural history of DIOS. We believe that our observations make a strong case for routine and early ileal mucosal and laparoscopic seromuscular ileal biopsy (60) in individuals with severe and recurrent DIOS. Specific anti-inflammatory treatments and/or antifibrotic therapies may become justifiable when further data become available about both the prevalence of these changes and also the efficacy of early anti-inflammatory therapies. This approach seems more appropriate than what is essentially symptomatic treatment with bowel cleansing agents, mucolytics, and increased doses of pancreatic enzymes (21,24,61,62). It seems likely that the potential association of intestinal colonic fibrosis with dose, duration, and brand of pancreatic enzyme administered has detracted the physician's focus of attention from an underlying gastrointestinal inflammatory process that is inherent to CF (17).
Transmural ileal inflammation, including lymphocytic myositis and ganglionitis, is a consistent finding in individuals with CF and symptomatic small intestinal obstruction and could lead to fibrosis through myofibroblastic transformation of connective tissue cells. These abnormalities appear to be intrinsic to CF because they are present before PERT, but progress with the passage of time. Further prospective studies of the prevalence of these changes and of the efficacy of early intervention appear warranted.
Research at the Institute of Child Health and Great Ormond Street Hospital for Children NHS Trust benefits from R&D funding received from the NHS Executive.
1. Riordan JR, Rommens JM, Kerem B, et al. Identification of the cystic fibrosis gene: cloning and characterization of complementary DNA. Science 1989; 245:1066–1073.
2. Zielenski J, Rozmahel R, Bozon D, et al. Genomic DNA sequence of the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Genomics 1991; 10:214–228.
4. Kunzelmann K. CFTR: interacting with everything? News Physiol Sci 2001; 16:167–170.
5. Kelley TJ, Elmer HL, Corey DA. Reduced Smad3 protein expression and altered transforming growth factor-beta1-mediated signaling in cystic fibrosis epithelial cells. Am J Respir Cell Mol Biol 2001; 25:732–738.
6. Soltys J, Bonfield T, Chmiel J, et al. Functional IL-10 deficiency in the lung of cystic fibrosis (cftr(−/−)) and IL-10 knockout mice causes increased expression and function of B7 costimulatory molecules on alveolar macrophages. J Immunol 2002; 168:1903–1910.
7. Tirouvanziam R, Khazaal I, Peault B. Primary inflammation in human cystic fibrosis small airways. Am J Physiol Lung Cell Mol Physiol 2002; 283:L445–L451.
8. Weber AJ, Soong G, Bryan R, et al. Activation of NF-kappaB in airway epithelial cells is dependent on CFTR trafficking and Cl-channel function. Am J Physiol Lung Cell Mol Physiol 2001; 281:L71–L78.
9. Raia V, Maiuri L, de Ritis G, et al. Evidence of chronic inflammation in morphologically normal small intestine of cystic fibrosis patients. Pediatr Res 2000; 47:344–350.
10. Rosenstein BJ, Langbaum TS. Incidence of distal intestinal obstruction syndrome in cystic fibrosis. J Pediatr Gastroenterol Nutr 1983; 2:299–301.
11. Kerem E, Corey M, Kerem B, et al. Clinical and genetic comparisons of patients with cystic fibrosis, with or without meconium ileus. J Pediatr 1989; 114:767–773.
12. Murshed R, Spitz L, Kiely E, et al. Meconium ileus: a ten-year review of thirty-six patients. Eur J Pediatr Surg 1997; 7:275–277.
13. Mushtaq I, Wright VM, Drake DP, et al. Meconium ileus secondary to cystic fibrosis. The East London experience. Pediatr Surg Int 1998; 13:365–369.
14. Millar-Jones L, Goodchild MC. Cystic fibrosis, pancreatic sufficiency and distal intestinal obstruction syndrome: a report of four cases. Acta Paediatr 1995; 84:577–578.
15. Ahmed N, Corey M, Forstner G, et al. Molecular consequences of cystic fibrosis transmembrane regulator (CFTR) gene mutations in the exocrine pancreas. Gut 2003; 52:1159–1164.
16. Ojeda VJ, Levitt S, Ryan G, et al. Cystic fibrosis, Crohn's colitis, and adult meconium ileus equivalent. Dis Colon Rectum 1986; 29:567–571.
17. Smyth RL, Ashby D, O'Hea U, et al. Fibrosing colonopathy in cystic fibrosis: results of a case-control study. Lancet 1995; 346:1247–1251.
18. Fell JM, Smith VV, Milla PJ. Infantile chronic idiopathic intestinal pseudo-obstruction: the role of small intestinal manometry as a diagnostic tool and prognostic indicator. Gut 1996; 39:306–311.
19. Ruuska TH, Karikoski R, Smith VV, et al. Acquired myopathic intestinal pseudo-obstruction may be due to autoimmune enteric leiomyositis. Gastroenterology 2002; 122:1133–1139.
20. Smith VV, Gregson N, Foggensteiner L, et al. Acquired intestinal aganglionosis and circulating autoantibodies without neoplasia or other neural involvement. Gastroenterology 1997; 112:1366–1371.
21. Mascarenhas MR. Treatment of gastrointestinal problems in cystic fibrosis. Curr Treat Options Gastroenterol 2003; 6:427–441.
22. Cleghorn GJ, Stringer DA, Forstner GG, et al. Treatment of distal intestinal obstruction syndrome in cystic fibrosis with a balanced intestinal lavage solution. Lancet 1986; 1:8–11.
23. Rubinstein S, Moss R, Lewiston N. Constipation and meconium ileus equivalent in patients with cystic fibrosis. Pediatrics 1986; 78:473–479.
24. Davidson AC, Harrison K, Steinfort CL, et al. Distal intestinal obstruction syndrome in cystic fibrosis treated by oral intestinal lavage, and a case of recurrent obstruction despite normal pancreatic function. Thorax 1987; 42:538–541.
25. Feingold J, Guilloud-Bataille M. Genetic comparisons of patients with cystic fibrosis with or without meconium ileus. Clinical Centers of the French CF Registry. Ann Genet 1999; 42:147–150.
26. Lloyd-Still JD. Crohn's disease and cystic fibrosis. Dig Dis Sci 1994; 39:880–885.
27. Tornblom H, Lindberg G, Nyberg B, et al. Full-thickness biopsy of the jejunum reveals inflammation and enteric neuropathy in irritable bowel syndrome. Gastroenterology 2002; 123:1972–1979.
28. Schappi MG, Smith VV, Milla PJ, et al. Eosinophilic myenteric ganglionitis is associated with functional intestinal obstruction. Gut 2003; 52:752–755.
29. Schappi MG, Roulet M, Rochat T, et al. Electrogastrography reveals post-prandial gastric dysmotility in children with cystic fibrosis. J Pediatr Gastroenterol Nutr 2004; 39:253–256.
30. Powell DW, Mifflin RC, Valentich JD, et al. Myofibroblasts. II. Intestinal subepithelial myofibroblasts. Am J Physiol 1999; 277(2 Pt 1):C183–C201.
31. Pucilowska JB, McNaughton KK, Mohapatra NK, et al. IGF-I and procollagen alpha1(I) are coexpressed in a subset of mesenchymal cells in active Crohn's disease. Am J Physiol Gastrointest Liver Physiol 2000; 279:G1307–G1322.
32. Pucilowska JB, Williams KL, Lund PK. Fibrogenesis. IV. Fibrosis and inflammatory bowel disease: cellular mediators and animal models. Am J Physiol Gastrointest Liver Physiol 2000; 279:G653–G659.
33. Matthes H, Herbst H, Schuppan D, et al. Cellular localization of procollagen gene transcripts in inflammatory bowel diseases. Gastroenterology 1992; 102:431–442.
34. Schroeder TH, Lee MM, Yacono PW, et al. CFTR is a pattern recognition molecule that extracts Pseudomonas aeruginosa LPS from the outer membrane into epithelial cells and activates NF-kappa B translocation. Proc Natl Acad Sci U S A 2002; 99:6907–6912.
35. Pier GB. Role of the cystic fibrosis transmembrane conductance regulator in innate immunity to Pseudomonas aeruginosa infections. Proc Natl Acad Sci U S A 2000; 97:8822–8828.
36. van Tol EA, Holt L, Li FL, et al. Bacterial cell wall polymers promote intestinal fibrosis by direct stimulation of myofibroblasts. Am J Physiol 1999; 277(1 Pt 1):G245–G255.
37. Di Mari JF, Mifflin RC, Adegboyega PA, et al. IL-1alpha-induced COX-2 expression in human intestinal myofibroblasts is dependent on a PKCzeta-ROS pathway. Gastroenterology 2003; 124:1855–1865.
38. Lu G, Qian X, Berezin I, et al. Inflammation modulates in vitro colonic myoelectric and contractile activity and interstitial cells of Cajal. Am J Physiol 1997; 273(6 Pt 1):G1233–G1245.
39. Serban DE, Florescu P, Miu N. Fibrosing colonopathy revealing cystic fibrosis in a neonate before any pancreatic enzyme supplementation. J Pediatr Gastroenterol Nutr 2002; 35:356–359.
40. Smyth RL, van Velzen D, Smyth AR, et al. Strictures of ascending colon in cystic fibrosis and high-strength pancreatic enzymes. Lancet 1994; 343:85–86.
41. Pawel BR, de Chadarevian JP, Franco ME. The pathology of fibrosing colonopathy of cystic fibrosis: a study of 12 cases and review of the literature. Hum Pathol 1997; 28:395–399.
42. Pettei MJ, Leonidas JC, Levine JJ, et al. Pancolonic disease in cystic fibrosis and high-dose pancreatic enzyme therapy. J Pediatr 1994; 125:587–589.
43. Campbell CA, Forrest J, Musgrove C. High-strength pancreatic enzyme supplements and large-bowel stricture in cystic fibrosis. Lancet 1994; 343:109–110.
44. Prestridge L, Rogers BB, Pritchard M, et al. Diffuse fibrosis of the colon complicating cystic fibrosis. J Pediatr Gastroenterol Nutr 1996; 22:219–224.
45. Jones R, Franklin K, Spicer R, et al. Colonic strictures in children with cystic fibrosis on low-strength pancreatic enzymes. Lancet 1995; 346:499.
46. Dodge JA. Concern about records of fibrosing colonopathy study. Lancet 2001; 357:1526–1527.
47. Dodge JA. Further comments on fibrosing colonopathy study. Lancet 2001; 358:1546.
48. Powell CJ. Colonic toxicity from pancreatins: a contemporary safety issue. Lancet 1999; 353:911–915.
49. Bakowski M. Pancreatic enzymes and fibrosing colonopathy. Lancet 1999; 354:249.
50. FitzSimmons SC, Burkhart GA, Borowitz D, et al. High-dose pancreatic-enzyme supplements and fibrosing colonopathy in children with cystic fibrosis. N Engl J Med 1997; 336:1283–1289.
51. Prescott P. Pancreatic enzymes and fibrosing colonopathy. Lancet 1999; 354:250.
52. Lloyd-Still JD, Beno DW, Uhing MR, et al. Pancreatic enzymes and fibrosing colonopathy. Lancet 1999; 354:251.
53. Freiman JP, FitzSimmons SC. Colonic strictures in patients with cystic fibrosis: results of a survey of 114 cystic fibrosis care centers in the United States. J Pediatr Gastroenterol Nutr 1996; 22:153–156.
54. Littlewood JM, Wolfe SP. Control of malabsorption in cystic fibrosis. Paediatr Drugs 2000; 2:205–222.
55. van Velzen D. Colonic strictures in children with cystic fibrosis on low-strength pancreatic enzymes. Lancet 1995; 346:499–500.
56. Dialer I, Hundt C, Bertele-Harms RM, et al. Sonographic evaluation of bowel wall thickness in patients with cystic fibrosis. J Clin Gastroenterol 2003; 37:55–60.
57. Simon-Bouy B, Satre V, Ferec C, et al. Hyperechogenic fetal bowel: a large French collaborative study of 682 cases. Am J Med Genet 2003; 121A:209–213.
58. Ramsden WH, Moya EF, Littlewood JM. Colonic wall thickness, pancreatic enzyme dose and type of preparation in cystic fibrosis. Arch Dis Child 1998; 79:339–343.
59. Orgad S, Berkenstadt M, Achiron R, et al. Hyperechogenic bowel loops and meconium ileus in a fetus carrying the D1152H and G542X cystic fibrosis CFTR mutations. Prenat Diagn 2002; 22:636–637.
60. Mazziotti MV, Langer JC. Laparoscopic full-thickness intestinal biopsies in children. J Pediatr Gastroenterol Nutr 2001; 33:54–57.
61. Koletzko S, Stringer DA, Cleghorn GJ, et al. Lavage treatment of distal intestinal obstruction syndrome in children with cystic fibrosis. Pediatrics 1989; 83:727–733.
62. Koletzko S, Corey M, Ellis L, et al. Effects of cisapride in patients with cystic fibrosis and distal intestinal obstruction syndrome. J Pediatr 1990; 117:815–822.
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