Colorectal inflammation and increased cell proliferation associated with oral sodium phosphate bowel preparation solution

Colorectal Inflammation and Increased Cell Proliferation Associated With Oral Sodium Phosphate Bowel Preparation Solution DAVID K, DRIMAN, MBCHB, FRCPC AND HAROLD G, PREIKSAITIS, MD, FRCPC Evidence is emerging that sodium phosphate (NaP), a commonly used oral cathartic agent, causes aphthoid ulcers or focal active colitis (FAC) in the colon and rectum. The alms of this study were (1) to assess the incidence of such ulcers diagnosed endoscopically ("aphthoid ulcers"), (2) to assess the incidence of histologically detected FAC and neutrophilic infiltration overlying lymphoid follicles ("aphthoid lesions"), and (3) to determine whether this effect of NaP is associated with epithelial cell proliferation. Aphthoid ulcers, unexplained by other diagnoses, were found in 18 of 687 consecutive patients (2.6%) who underwent colonoscopic examination after oral NaP preparation during a 12-month period; biopsy specimens showed FAC or aphthoid lesions. FAC was present in 11 of 316 patients (3.5%) who had biopsies but were endoscopically normal. Eight patients with aphthoid ulcers in the rectosigmoid showed no abnormalities when reexamined by flexible sigmoidoscopy after an interval as short as 7 days (range, 7 to 56 days). Mucosal biopsy specimens from these patients were assessed for apoptosis and epithelial proliferation by determining the MIB-1 labeling index (LI). The LI was increased by 136% after NaP preparation (55 -+ 6) compared with biopsy specimens obtained from the same patients during reexamination without NaP preparation (23 ± 6, P = .01). This correlated with the number

of apoptotic bodies per 10 colonic crypts (1.2 ± 0.3 v 0.5 + 0.2, respectively). To determine whether these proliferative changes represent a response to mucosal ulceration, rectosigmoid biopsy specimens were compared in two additional patient groups: an NaP group in whom no gross lesions were evident and a no-NaP group who were not exposed to NaP. Although more modest, similar changes in the LI (42 +- 4 and 30 ± 3, respectively, P = .03) and in the occurrence of apoptotic bodies per 10 colonic crypts (!.3-+ 0.4 and 0.4 ± 0.1, respectively) were observed. We conclude that use of NaP is associated with increased colorectal crypt epithelial cell proliferation. This proliferative response to NaP exposure is evident in the absence of colonoscopicaily or other histologically recognizable abnormalities. In a proportion of patients, aphthoid ulcers, FAC, or aphthoid lesions serve as markers of mucosal damage by NaP. HUM PAWHOL29:972-978. Copyright © 1998 byW.B. Saunders Company Key words:focal active colitis, aphthoid tdcer, cell proliferation, sodium phosphate, cathartics. Abbreviations: FAC, focal active colitis; NaP, oral sodium phosphate; PEG, polyethylene glycol; IBS, irritable bowel syndrome; H&E, hematoxylin and eosin; LI, labeling index.

As stated in a review published in 1975, "few organs or systems of organs are as vulnerable to the ravages of the physician's diagnostic and theraPeutic armamentarium as are the colon and rectum. Attack may be by land, air or sea: namely, through direct manipulation, by irradiation or by the bloodstream. ''1 This study has evaluated a form of land attack on the large intestine-namely, the adverse effects of oral sodium phosphate (NAP) used as a lavage solution. NaP is an effective cathartic agent used to prepare the colon before colonoscopy. Use of NaP is becoming increasingly common, c o m p a r e d with alternative preparatory agents, notably, polyethylene glycol-electrolyte lavage solution (PEG). NaP is cheaper, and patients are required to ingest a smaller volume of solution. A recent survey of Canadian gastroenterologists showed that almost half use NaP in preparing their patients for colonoscopy. 2 As use of NaP has increased, adverse effects have b e c o m e evident. A recent study reported that aphthoid

lesions occurred in as many as one in four patients who received NaP before colonoscopy, a rate 10 times greater than with use of PEG. 3 An anecdotal r e p o r t has also described the presence of unexplained aphthoid lesions in patients p r e p a r e d with NaP, 4 and we too have noted the u n e x p e c t e d occurrence of colonoscopical!y visible aphth0id lesions or histologically identifiable focal active colitis (FAC) in patients prepared with NaP. The aims of this study were to assess, in a group of patients undergoing colonoscopy and sigmoidoscopy, whether aphthoid lesions or FAC could be attributed to NaP, and to assess the frequency of these changes. In addition, because other cathartic agents are reported to cause colorectal mucosal proliferation, 5,6 the effect of Nap on epithelial proliferation was investigated. Note that, in the remainder of this report, the term aphthoid lesion is used to denote a histological abnormality, whereas aphthoid ulcer denotes an endoscopic abnormality.

METHODS From the Departments of Pathology and Medicine (Division of Gastroenterology), St Joseph's Health Centre and the University of Western Ontario, London, Ontario, Canada. Accepted for publica~ tion February 9, 1998. H.G.P. is a recipient of an Ontario Ministry of Health Career Scientist Award. Address correspondence to David K. Driman, MBChB, FRCPC, Department of Pathology, St Joseph's Health Centre, 268 Grosvenor St, London, Ontario, N6A 4V2, Canada. Copyright © 1998 by W.B. Saunders Company

0046-8177/98/2909-001358.00/0

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Patients Group A. T h e o c c u r r e n c e o f colonic a p h t h o i d ulcers in all patients who h a d c o l o n o s c o p i c e x a m i n a t i o n s after p r e p a r a tion with NaP were r e c o r d e d for a 12-month p e r i o d . Endoscopy was d o n e by any o f five gastroenterologist-endoscopists, all o f w h o m were familiar with the p o t e n t i a l o c c u r r e n c e o f a p h t h o i d ulcers after the use o f NaP, a n d t h e i r typical e n d o s c o p i c a p p e a r a n c e . T h e o b s e r v a t i o n o f at least o n e

COLONIC EFFECTSOF SODIUM PHOSPHATE (Driman & Preiksaitis) aphthoid ulcer anvwhere in the colon, which was otherwise unexplained by the clinical history or subsequent diagnosis. was considered to be a positive example of an NaP-induced abnormality. In other words, patients with known or subsequently proved diagnoses of inflammatory bowel disease, ischemic colitis, or infectious colitis were excluded. Patients with lymphocytic and collagenous colitis were also excluded, as well as patients taking nonsteroidal antiinflammatory drugs regularly or who had taken these drugs for more than 3 days in the 2-week period preceding endoscopy. In some patients, mucosal biopsies were performed if the gross appearance was normal (to rule out lymphocytic or collagenous colitis), or if presumed NaP-induced ulcers were identified. Group B. Eight patients with NaP-induced abnormalities identified from group A ("Pre" group) were subsequently reexamined by flexible sigmoidoscopy, without exposure to NaP preparation ("Post" group). Groups C and D. Two additional groups of patients were identified so that the proliferative effects of NaP on mucosa that was endoscopicaUy and histologically normal could be studied. These patients had colonoscopic examination after preparation with NaP, and mucosal biopsies of the sigmoid colon or rectum performed as part of their investigation for a functional bowel disorder (group C. or "NAP" group). Patients with known intestinal disorders as detailed previously were excluded. These patients had no identifiable abnormality on endoscopy or routine histological examination of the mucosa. The biopsy specimens of these patients were compared with a separate group of patients, applying the same exclusion criteria as described for group A, but who were investigated via sigmoidoscopy and who received no bowel preparation before sigmoidoscopy and biopsy (group D or "no-NaP" group). Patients who received NaP took one dose (44 mL, Fleet's Phosphosoda) at approximately 3:00 p m on the day before the procedure, and again at approximately 6:00 AMon the day of the procedure. Patients were allowed as much clear fluid as desired until their arrival at the hospital. All patients were examined 3 to 9 hours after their last dose of NaR

ethanol rehydration , sections were counterstained with Carazzi's hematoxylin and then pretreated using a microwavable pressure cooker (Nordicware Microwave Tender Cooker, Minneapolis, MN) containing 10 m m o l / L citrate buffer, in a microwave oven (Panasonic NN-6553C, Mississauga, ON). The slides were microwaved on "high" (900W) for 15 minutes, removed from the oven, and cooled for 30 minutes--15 minutes with the cooker lid on, and 15 minutes with the lid removed. Two percent normal horse serum was applied for 30 minutes to block nonspecific binding. The sections were then incubated overnight ( - 1 6 hours) at 4°C with prediluted MIB-1 mouse antibody further diluted 1:3 in 2% normal horse serum in phosphate-buffered saline. A biotinylated horse antimouse immunoglobulin G antibody at 1:900 dilution (Vector Laboratories, Burlingame, CA) was applied for 40 minutes at room temperature. The Vector stain ABC kit reagent (Vector Laboratories) was then applied and incubated for 40 minutes at room temperature. The immunologic reaction was visualized using 3.3.'-diaminobenzidine tetrahydrochloride as a chromogen. For negative controls, the primary antibody was substituted with another antibody of the same IgG class but with different specificity. To assess cell proliferation, MIB-1 "labeling indices" (LI) were calculated in each of six different compartments per crypt, in each of 10 well-oriented crypts per biopsy (Fig 1). Each crypt was divided longitudinally into left and right "columns," and each column divided into "upper, .... middle," and "lower" compartments. In each compartment, the LI was calculated by dividing the number of labelled cells by the total number of cells, and a mean LI was calculated per crypt for each biopsy. A "total" LI was calculated by dividing the number of labeled cells in the entire crypt by the total number of cells in the crypt.

Pathological Examination

RESULTS

Biopsy specimens were fixed overnight in 10% formaldehyde solution and e m b e d d e d in paraffin. Sections were cut at 4 to 6 pm and stained with hematoxylin and eosin (H&E). FAC was defined as focal collections (<10% of crypts present) of neutrophils within crypt epithelium, with or without neutrophils in the surrounding lamina propria, but in the absence of other abnormal findings. Aphthoid lesions were defined as neutrophilic infiltration of surface epithelium overlying lymphoid follicles. For counting apoptosis and for the assessment of the immunohistochemistry, biopsy specimens that were suboptimally oriented or contained fewer than 10 well-oriented crypts were excluded from the study groups. Apoptosis. H&E-stained sections were evaluated by counting the total number of apoptotic bodies in 10 well-oriented crypts. Apoptotic bodies were defined as round to oval membrane-bound fragments of basophilic pyknotic material; these were differentiated from n o n - m e m b r a n e - b o u n d pyknotic fragments and from isolated inflammatory ceils. Immunohistochemistry. Crypt cell proliferation was evaluated in biopsy specimens with and without use of NaP (groups B, C, and D). Immunohistochemistry was performed using the MIB-1 antibody (lmmunotech, Marseille, France). Sections of paraffin-embedded formalin-fixed tissue cut at 3 p m were deparaffinized in xylene, rehydrated in graded ethanol solutions, and treated with 3% aqueous hydrogen peroxide for 10 minutes to block endogenous peroxidase activity. After

Group A

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Statistical Analysis The data were analyzed using Mann-Whitney u-tests and Student's t-tests. Results are shown as mean _+ standard error of the mean. P < 0.05 is considered significant.

A total o f 741 p a t i e n t s u n d e r w e n t c o l o n o s c o p i c e x a m i n a t i o n a f t e r p r e p a r a t i o n with N a P in t h e 12Le~ column

,..,

Upper compartment

Right column

(

i

Labelling Index = no. of labelled Cells / compadment total no. of cells / compal~ent

L i Middle ¢omparkmsnt

i

LO,MSr compartment

CRYPT

FIGURE 1. Schematic representation of method used for calculating MIB-1 labeling indices. Each well-oriented crypt is dMded into two cell '!columns" and each column into three equal "compartments" based on the number of cells in each column.

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Volume29, No. 9 (September 1998)

m o n t h period studied. Fifty-four were excluded from further analysis for reasons outlined in Methods or because the examination was incomplete. Of the remaining 687 patients, 18 (2.6%) were f o u n d to have otherwise unexplained aphthoid ulcers, presumed to be due to NaP, and similar to those described by othersfi4 The appearance was that of small 2- to 3-mm shallow ulcers usually s u r r o u n d e d by an erythematous halo, and occurring either singly or in clusters of approximately 3 to 18 lesions (Fig 2). Location of the ulcers was not recorded in sufficient detail to allow quantitative assessment, but there was agreement amongst the endoscopists that the lesions occurred most frequently, if not exclusively, in the rectosigmoid region of the colon. Aphthoid ulcers were examined by biopsy (all or up to one third of lesions present in the patient with 18 ulcers) as well as surrounding mucosa in some cases. O f tile remaining patients, 316 had biopsies. A mean of 2.9 -2_ 1.6 biopsies were p e r f o r m e d per patient (range, 1 to 6). Biopsy specimens from patients with aphthoid ulcers showed either FAC (three patients) (Fig 3) or aphthoid lesions (!5 patients) (Fig 4). A further 11 patients (3.5%) had FAC in the absence of endoscopically evident aphthoid ulcers. Therefore, 6.1% of patients who received NaP showed either aphthoid ulcers endoscopically or FAC or aphthoid lesions on biopsy. In biopsy specimens showing FAC, the abnormalities were seen in up to three foci, usually a single focus in a single biopsy fragment. These 29 patients (10 m e n and 19 women) ranged in age from 16 to 75 years (mean, 43.7 + 2.4) and had the following clinical diagnoses: functional bowel disorder with abdominal pain (n = 6), constipation (n = 1), diarrhea (n = 2) or classic irritable bowel syndrome (IBS) (n = 12)7; polyps or a family history of cancer (n = 6); diverticu!osis (n = 1); and diarrhea secondary to autonomic dysfunction (n = 1). This group did not differ significantly from the entire colonoscopy population in terms of clinical diagnoses, male:female ratio (0.6), or age distribution (range, 16 to 94 years, mean, 47.2 +_ 3.1). Group B Eight patients from group A who had aphthoid ulcers on colonoscopy were re-endoscoped without use of NaP (post group) and showed complete resolution of aphthoid ulcers. The median time between examinations was 22 days (range, 7 to 56 days). In six Of these patients, mucosal biopsies were p e r f o r m e d at colonoscopy, when aphthoid ulceration was seen in the sigmoid colon or rectum, and at sigmoidoscopy, after resolution of these lesions. All biopsie s p e r f o r m e d at colonoscopy showed FAC or aphthoid lesions; biopsies p e r f o r m e d at sigmoidoscopy showed no histological abnormalities. T h e mean n u m b e r of biopsies p e r f o r m e d was 2.5 + 0.4 in the pre group and 2.8 + 0.5 i n the post group. The mean n u m b e r of apoptotic bodies was 1.2 + 0.3 in the pre group and 0.5 + 0.2 in the post group. An example of apoptosis is shown in Figure 5. An example of the immunohistochemistry is shown in Figure 6, and the results are summarized in Figure 7. In the entire crypt cell column, the mean n u m b e r o f

MIB-l-posifive nuclei in the pre group was 136% greater than in the post group (P = .01). This difference was mainly due to a 12!% greater LI in the lower c o m p a r t m e n t (P = .03) and a 115% greater LI in the middle c o m p a r t m e n t (P = .05). Groups C a n d D T h e r e were 16 patients (10 m e n and 6 women) in the NaP group, with an age range of 19 t o 79 years (mean, 38.3 + 5.1). T h e r e were 17 patients (!3 m e n and 4 women) in the no-NaP group, with an age range of 19 to 58 years (mean, 32.8 + 3.8). All patients were being investigated for idiopathic diarrhea. All biopsy specimens showed no histological abnormalities on routine H&E sections. T h e mean n u m b e r of apoptotic bodies was 1.3 + 0.4 in the NaP group and 0.4 _+ 0.1 in the no-NaP group. T h e results of immunohistochemistry are summarized in Figure 8. In the entire crypt cell column, the mean n u m b e r of MIB-l-positive nuclei in the NaP group was 40% greater than in the no-NaP group (P = .03). This difference was mainly due to an 89% greater LI in the middle c o m p a r t m e n t of the crypts, in the NaP group (P = .02). As shown in Figures 7 and 8, the MIB-1 LIs in the two groups of patients not exposed to NaP (groups B and D~ post and no-NaP), are not significantly different. However, the proliferative response to NaP in patients with aphthoid ulcers (group A, pre) is greater t h a n in group C (NAP).

DISCUSSION This study has shown a 6.1% incidence of unexplained mucosal abnormalities in the large intestine of patients p r e p a r e d with NaP. These abnormalities comprised FAC or aphthoid lesions detected on biopsy, or aphthoid ulcers f o u n d at endoscopy. Because patients with other known causes of FAC were excluded, s this study provides additional evidence to support the association of adverse mucosal effects with use of NaP. Prior studies with detailed endoscopic and histological analysis of tile effects of NaP on the colorectal mucosa are few (Table 1). It has been shown that NaP enemas cause endoscopically detectable mucosal hyperemia and obliteration of the normal vascular pattern, with sloughing of surface epithelium seen on biopsy. 9 Several studies have c o m p a r e d NaP with PEG, but most studies have evaluated patient preference and bowel cleansing ability as their primary aims and have not reported endoscopic mucosal abnormalities or pathological findings. 1~18 Better patient acceptance, superior or comparable bowel cleansing effects, and lower cost have all been demonstrated with use of NaP. Two studies have formally evaluated histological f i n d i n g s Y 3 The most recent r e p o r t e d a 24.5% incidence of aphthoid lesions and a 5.6% incidence of FAC in patients who received NaP for colonoscopy preparation, c o m p a r e d with 2.3% for those patients prepared with PEG. ~ A recent anecdotal report has also described the presence

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FIGURE 2. Endoscopic findings at colonoscopy. Several targetaid aphthoid lesions are present; these are discrete with pale centers and erythematous halos.

FIGURE3. (A) Focal active colitis. Focal neutrophilic infiltration of crypts (arrow) in otherwise normal mucosa. (B) Detail of cryptitis; occasional neutrophils are also present in the lamina propria surrounding the inflamed crypt. (H&E stains; original magnification [A] x22, [B] x87.)

FIGURE4. (A) Aphthoid lesioncharacterized by epithelial erosion and neutrophilic infiltration overlying a lymphoid follicle. (B) Detail of epithelial inflammation. (H&E stains; original magnifications [A] x22, [B] x87.)

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FIGURE 5. Apoptotic body--round, membrane-bound fragments of basophilic pyknotic material (arrowhead). (H&E stain; original magnification × 133.)

of aphthoid ulcers in 17 patients, mostly in the distal sigmoid and rectum but on occasion in the cecum. 4 Aphthoid ulcers have b e e n n o t e d to be a suspected complication o f bowel preparation with NaP in a recent survey of Canadian gastroenterologists. 2 NaP has also been implicated as a cause of ischemic colitis, via intravascular volume depletion. 19 T h e clinical significance of FAC has b e e n the subject of a recent study, s This showed that FAC could be attributed to an infectious cause in 45% of patients, antibiotic-associated colitis in 10%, ischemia in 5%, and to IBS in 14%. "Incidental" or asymptomatic FAC was f o u n d in 26%. This latter group may well have had NaP-induced lesions, as may the IBS group; histological abnormalities are not known to occur in IBS unless there is another cause for these, such as use of NaE Laxatives have previously been shown to induce

colonic mucosal abnormalities (see Table 1). Rectal administration of bisacodyl has b e e n r e p o r t e d to cause endoscopic and histological abnormalities in as short a time as 15 to 30 minutes after administration, g T h e r e is also evidence that laxatives can induce colonic epithelial proliferation. Increased proliferation was n o t e d 24 hours after oral administration of anthraquinone glycosides, 5 and sterculia gum enemas have been r e p o r t e d to induce epithelial proliferation. 6 Epithelial proliferation does not appear to be a general effect of bowel preparation on the colonic mucosa, because one other study showed that rectal epithelial proliferation is not affected by tap water enemas, PEG, or oral senna compounds. 2° The current study is the first to formally evaluate the effect of NaP on rectal mucosal proliferation. We showed that, within 15 hours of ingesting NaP, rectal mucosal biopsy specimens from patients who

FIGURE 6. Immunohistochemistry for MIB-1. (A) After preparation with NaP, there is marked expansion of the crypt proliferative zone--characterized by extension of positive nuclei into the middle third of the crypts. (B) MIB-1-positive crypt epithelial nuclei are fewer and confined to the lower third of the crypts in a biopsy specimen from a patient not prepared with NaP. (Original magnification ×22.)

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COLONIC EFFECTSOF SODIUM PHOSPHATE(Driman & Preiksaitis) 110

110 100

Pre (with NaP)

91.0 ~

90

71.5

80*

55.5

54.5

V///~

NaP no-NaP

90-

80

70 5o

E~

100-

Post {without NaP)

70-

T

,'u

.~ 50

eo-

4~.9

47.2

.~ 5 0 -

4o

30

30-

2O

20-

10

'10-

0

0Total

Lower

Middle

Upper

FIGURE 7. Comparison of mean values for MIB-1 labeling indices (LI) in group B after exposure to oral NaP (Pre) and on re-biopsy without NaP preparation (Post). Aphthoid ulcers identified endoscopically after NaP had resolved on reexamination. *Indicates a significant difference between Pre and Post biopsies.

ingested NaP showed increased crypt cell apoptosis and crypt epithelial proliferation. The MIB-1 antibody is a monoclonal antibody that recognizes components of the Ki-67 antigen. 21 This antigen reacts with a nuclear cell proliferation antigen expressed in all active phases of the cell cycle; both MIB-1 and Ki-67 antibodies are established markers of cell proliferation. MIB-1 labeling indices showed expansion of the crypt proliferative zone into the middle and u p p e r thirds of the crypt. U n d e r normal circumstances, proliferation of colorectal crypt epithelial cells occurs in the basal compartm e n t or deep one-third of the crypt. Expansion of this proliferating c o m p a r t m e n t signifies increased turnover of crypt epithelial cells. The mechanism by which NaP stimulates cell proliferation is unknown. Increased cell proliferation could be a direct effect of NaP on the mucosa, or an effect mediated by other pathways. Given the short period between ingesting NaP and the induction of increased cell proliferation, NaP likely exerts a direct toxic effect on the mucosa. Apoptosis could play a role in either pathway; apoptosis was increased with use of NaP, but the low levels of apoptosis detected precludes meaningful interpretation of the results, given the n u m b e r of biopsy specimens studied. Oral calcium has been shown to inhibit mucosal proliferation and to reduce the hyperproliferative effects on colonic epithelial cells of TABLE I . Summary of Previously Reported Effects of Laxatives a n d Enemas on C o l o n i c M u c o s a

Preparation Bisacodyl Anthraquinone glycosides Sterculia gum NaP enema Oral NaP Oral NaP Oral NaP

Effect

References

Sloughing of surface epithelium Epithelialproliferation

Meisel et al9

Epithelial proliferation Sloughing of surface epithelium Aphthoid ulceration Aphthoid ulceration, FAC Ischemic colitis

Lehy et al6 Meisel et al9

Kleibeukeret al5

v /3.5 T / A 0,8

Total

Lower

Middle

Upper

FIGURE 8. MIB-1 labeling indices (LI) compared in colonic mucosal biopsy specimens obtained from patients without prior exposure to oral NaP (Group C, no-NaP) and a separate group after preparation with oral NaP (Group D, NAP). The colonic muoosa in both group C and group D showed no endoscopic or histological abnormality. *Indicates a significant difference between NaP and no-NaP biopsy specimens.

fatty acids and bile acids by binding to these and converting them to insoluble calcium compounds. ~2-26 Phosphate salts could induce colonic epithelial proliferation by interaction with dietary calcium, although this is unlikely given the short time between ingesting NaP and developing increased proliferation. Prostaglandins of the E series can have a weak proliferative effect on the c010n27; sennosides act at least partly through induction of the release of mediators, especially prostaglandins. 28 To our knowledge, no studies have looked at the role of NaP in prostaglandin homeostasis. The findings of the current study implicates NaP as a causative agent in aphthoid ulceration and FAC in the colonic mucosa. Because biopsies were not p e r f o r m e d in all of our patients, and because the FAC lesion is patchy, it is possible that we underestimated the overall incidence of NaP-induced FAC. In addition, group B patients who were reexamined by flexible sigmoidoscopy were not randomly selected and therefore may represent one extreme o f patient sensitivity to these effects. Nonetheless, aphthoid ulcers resolved in all these patients who served as their own controls, negating any potential effects of selection bias. In summary, this study has shown that NaP induces a spectrum of colorectal mucosal damage, ranging from aphthoid lesions through to FAC, and that even in endoscopically and histologically normal mucosa, NaP induces colorectal crypt epithelial proliferation. In addition to the use of NaP, the differential diagnosis of FAC includes Crohn's disease, infection, and possibly ischemia. Pathologists should include the adverse effects of NaP in the differential diagnosis of FAC and aphthoid lesions.

Acknowledgment. The immunohistochemistry for this study was performed by Cathie Crukley, MLT, and Doug Geddes, BSc, MLT.

Hixson4 Zwaset al3

REFERENCES

Oh et a119

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2. Chan A, Vanner S: Trends in the use of colonic lavage solutions prior to colonoscopy: Pitfalls and complications. Can J Gastroentero110:20A, 1996 3. Zwas FR, Cirillo NW, E1-Serag HB, et ah Colonic mucosal abnormalities associated with oral sodium phosphate solution. Gastrointest Endosc 43:463-466, 1996 4. Hixson LJ: Colorectal ulcers associated with sodium phosphate catharsis [letter]. Gastrointest Endosc 42:101-102, 1995 5. Kleibeuker JH, Cats A, Zwart N, et al: Excessively high cell proliferation in sigmoid colon after an oral purge with anthraquinone glycosides [see comments] .J Natl Cancer Inst 87:452-453, 1995 6. Lehy T, Ahitbol J, Mignon M: Influence de la preparation rectale par lavement sur la proliferation cellulalre dans la muqueuse rectale normale de l'homme. Gastroenterol Clin Biol 8:216-221, 1984 7. Drossman DA, Whitehead WE, Camilleri M: Irritable bowel syndrome: A technical review for practice guideline development. Gastroenterology 112:2120-2137, 1997 8. Greenson JK, Stern RA, Carpenter SL, et ah The clinical significance of focal active colitis. HUM PATHOL28:729-733, 1997 9. MeiselJL, Bergman D, Graney D, et ah Human rectal mucosa: Proctoscopic and morphological changes caused by laxatives. Gastroenterology 72:1274-1279, 1977 10. MarshallJB, Barthel JS, King PD: Short report: Prospective, randomized trial comparing a single dose sodium phosphate regimen with PEG-electrolyte lavage for colonoscopy preparation. Aliment Pharmacol Ther 7:679-682, 1993 11. Henderson JM, Barnett JL, Turgeon DK, et al: Single-day, divided-dose oral sodium phosphate laxative versus intestinal lavage as preparation for colouoscopy: Efficacy and patient tolerance. Gastrointest Endosc 42:238-243, 1995 12. Kolts BE, Lyles WE, Achem SR, et al: A comparison of the effectiveness and patient tolerance of oral sodium phosphate, castor oil, and standard electrolyte lavage for colonoscopy or sigmoidoscopy preparation [see comments]. AmJ Gastroenterol 88:1218-1223, 1993 13. Vanner SJ, MacDonald PH, Paterson WG, et al: A randomized prospective trial comparing oral sodium phosphate with standard polyethylene glycol-based lavage solution (Golytely) in the preparation of patients for colonoscopy [see comments]. AmJ Gastroenterol 85:422-427, 1990 14. Golub RW, Kerner BA, Wise WE Jr, et al: Colonoscopic bowel preparations--Which one? A blinded, prospective, randomized trial. Dis Colon Rectum 38:594-599, 1995 15. Afridi SA, BarthelJS, King PD, et ah Prospective, randomized trial comparing a new sodium phosphate-bisacodyl regimen with conventional PEG-ES lavage for outpatient colonoscopy preparation. Gastrointest Endosc 41:485-489, 1995

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16. Huynh T, Vanner S, Paterson W: Safety profile of 5-h oral sodium phosphate regimen for colonoscopy cleansing: Lack of clinically significant hypocalcemia or hypovolemia. Am J Gastroentero190:104-107, 1995 17. Clarkston WK, Tsen TN, Dies DF, et ah Oral sodium phosphate versus sulfate-free polyethylene glycol electrolyte lavage solution in outpatient preparation for colonoscopy: A prospective comparison. Gastrointest Endosc 43:4248, 1996 18. MarshallJB, PinedaJJ, BarthelJS, et al: Prospective, randomized trial comparing sodium phosphate solution with polyethylene glycol~electrolyte lavage for colonoscopy preparation. Gastrointest Endosc 39:631-634, 1993 19. Oh JK, Meiselman M, Lataif LE: Ischemic colitis caused by oral hyperosmotic saline laxatives. Gastrointest Endosc 45:319-322, 1997 20. Fireman Z, Rozen P, Fine N, et ah Reproducibility studies and effects of bowel preparations on measurements of rectal epithelial proliferation. Cancer Lett 45:59-64, 1989 21. Cattoretti G, Becker MH, Key G, et ah Monoclonal antibodies against recombinant parts of the Ki-67 antigen (MIB 1 and MIB 3) detect proliferating ceils in microwave-processed formalin-fixed paraffin sections.J Patho1168:357-363, 1992 22. Rozen P, Fireman Z, Fine N, et al: Oral calcium suppresses increased rectal epithelial proliferation of persons at risk of colorectal cancer. Gut 30:650-655, 1989 23. Lipkin M, Newmark H: Effect of added dietary calcium on colonic epithelial-cell proliferation in subjects at high risk for familial colonic cancer. N EnglJ Med 313:1381-1384, 1985 24. Wargovich MJ, Eng VWS, Newmark HL, et al: Calcium ameliorates the toxic effect of deoxycholic acid on colonic epithelium. Carcinogenesis 4:1205-1207, 1983 25. Wargovich MJ, Eng VWS, Newmark HL: Calcium inhibits the damaging and compensatory proliferative effects of fatty acids on mouse colon epithelium. Cancer Lett 23:253-258, 1984 26. Hu PJ, Baer All, Wargovich MJ: Calcium and phosphate: Effect of two dietary confounders on colonic epithelial cellular proliferation. Nutrition Research 9:545-553, 1989 27. Goodlad RA, Mandir N, Levin S, et al: Prostaglandins and the colonic epithelium: Effects of misoprostol on crypt size, cell production, and cell migration in the dog. Gastroenterology 101:1229-1234, 1991 28. Nijs G, de Witte P, Geboes K, et al: Influence of rhein anthrone on peristaltic reflex of guinea-pig isolated ileum: Involvement of prostaglandins. BrJ Pharmaco1108:269-273, 1993