State of the Art David W. Gelfand, MD •¿ Michael Y. M. Chen, MD •¿ David J. Ott, MD
Preparing the Colon for the Barium Enema Examination' ADIOLOGISTS
attending
meetings
of the Society of Gastrointesti nal Radiologists often saw the late Dr Roscoe E. Miller with a button in his lapel that read “¿Happinessis a Clean Colon―(1). One was never certain whether Dr Miller intended this as a general statement or in reference to the barium enema examination. The radiologic examination of the colon has been performed for ap proximately 90 years. Almost from the beginning, there has been con troversy over the methods used to prepare the colon for the examina tion. Herein, we present a review of the subject of cleansing the colon in preparation for the barium enema and discuss (a) dietary restrictions, (b) common cathartics and their methods of action, (c) the use of the cleansing enema, (d) observations on commonly used preparations, (e) our own regimen for colonic cleansing, and (f) quality controls for ensuring adequate preparation. DIETARY RESTRICTION Most colon cleansing regimens use dietary restriction to reduce the amount of the fecal material that must be removed by cathartics. The majority of these require a low-resi due or liquid diet be consumed for at least 24 hours. This requirement is appropriate and helpful, particularly
Index terms: Barium enema examination. Colon, radiography, 75.128 •¿ State-of-art re views Radiology
@
1991; 178:609-613
‘¿Fromthe Department of Radiology, Bow man Gray School of Medicine, Winston-Salem, NC 27103. Received October 2, 1990; accepted October 29. Address reprint requests to D.W.G. RSNA, 1991
in an outpatient setting. However, because of the necessity to minimize the length of hospitalizations, 24 hours may not be available between the request for a barium enema ex amination and its performance. Al though 24 hours of dietary restriction is indeed helpful, the colon cleansing regimen in use at Bowman Gray School of Medicine, which is de scribed herein, has proved highly ef fective in patients in whom only a few hours of dietary restriction is possible (1). CATHARTICS Cathartics are drugs that promote defecation, although in common ter minology they are more often re ferred to as laxatives. Also, textbooks of pharmacology may use the terms laxative, cathartic, and purgative to describe this class of drugs according to the intensity of their action, in in creasing order of potency. Colon cleansing regimens very often com bine use of a saline cathartic with an irritant cathartic administered sever al hours later. Saline cathartics share a common mechanism of action in that they contain inorganic ions that are slow ly absorbed from the intestines. These ions include the cation magne sium and the anions citrate, sulfate, and phosphate. They are retained in the small intestine for a considerable time after being ingested. During this period, the intestinal mucosa acts as a semipermeable membrane divid ing the patient's circulation from the intestinal contents (2). Since the in testinal mucosa is permeable to wa ter, water tends to pass from the cir culation into the intestinal tract until the cathartic salt solution becomes isotonic with the extracellular fluid. The resulting large volume of fluid retained in the intestines stimulates peristalsis. After reaching the colon, the abnormally expanded colonic
contents are expelled. Magnesium citrate is the most com monly used of the saline cathartics. Magnesium citrate solution is widely available as a flavored water solution of the salt in 300-mL bottles. Addi tion of sodium bicarbonate and citric acid provides effervescence. Magnesium oxide acts as a cathartic after conversion into water-soluble salts within the gastrointestinal tract. In the oxide form, it is almost insolu ble in water. The usual cathartic dose for cleansing of the colon is 3—4g. supplied as tablets. Sodium phosphate (phosphosoda) also is an effective saline cathartic. In its most common form, it is supplied as a proprietary combination of sodi urn phosphate and sodium biphos phate in 100 mL of aqueous solution. Certain precautions must be main tained when using saline cathartics. The magnesium ion is partially ab sorbed after oral administration. Nor mally, the kidneys so rapidly excrete the magnesium ion that changes in its level in the blood cannot be de tected. However, if magnesium ion is administered to a patient with im paired renal function, levels of mag nesium ion in the extracellular fluid may become sufficiently elevated to produce magnesium poisoning. The use of magnesium citrate or magne sium oxide is therefore inadvisable in patients with poor renal function. Sodium phosphate cathartics con tain sufficient sodium and phosphate ions to produce both hypernatremia and hyperphosphatemia in patients with decreased renal function. These products also are contraindicated in patients with congestive heart failure or who are on a low-salt diet, since the sodium ion is readily absorbed. In patients with decreased renal function, hypocalcemia also may occur. Intestinal lavage is a variant use of saline cathartics in which a very large volume of an isotonic, nonab 609
sorbable solution is administered for the purpose of flushing the contents of the colon from above. The most commonly used of several commer cially available proprietary solutions contains polyethylene glycol, sodium sulfate, sodium bicarbonate, sodium chloride, and potassium chloride dis solved in water to a final volume of 4 L. After the patient has fasted for 4 hours, the solution is ingested at a rate of 240 mL (8 oz) every 10 mm utes until the rectal effluent is clear or the entire 4 L has been consumed. Despite the massive volume of fluid ingested, there is little systemic ab sorption of water or salts. This meth od of colonic cleansing finds its greatest use as a preparation for co lonoscopy. Its major disadvantage as a preparation for the barium enema examination is the significant amount of fluid usually found in the colon after its use. Its use is also asso ciated with abdominal discomfort in a significant minority of patients. Irritant cathartics are often used for cleansing the colon for a barium enema examination either alone or, more commonly, in combination with a saline cathartic. The irritant cathartics most frequently employed in preparation for the barium enema study are castor oil, senna extract, and bisacodyl. Castor oil is obtained from the cas tor bean, the seed of Ricinus communis. The various uses of castor oil appar ently have been known for thou sands of years, since the castor bean is depicted in ancient Egyptian wall paintings (3). As extracted from the bean, castor oil is in the form of the triglyceride of ricinoleic acid, an un saturated fatty acid. Within the small intestine, castor oil is hydrolyzed to glycerol and ricinoleic acid, the latter substance being the active cathartic agent (2). Ricinoleic acid greatly stimulates motor activity of the small intestine by means of a local irritant action. This increases peristalsis and causes a rapid propulsion of the small-intesti nal contents into the colon. The ca thartic action of castor oil is not caused by diffusion of additional flu id into the small intestine, but results from the rapid passage of the normal intestinal contents into the colon be fore they can be absorbed. Because al most all of the ricinoleic acid is ab sorbed in the small intestine, there is only mild stimulation of the colon. As a result, contrary to common per ception, there is relatively little intes tinal griping associated with the ca thartic action of castor oil. 610 •¿ Radiology
Castor oil is a particularly safe ca thartic in that hydrolysis of only a portion of the ingested castor oil pro duces sufficient ricinoleic acid to irri tate the small intestine. The resulting increased peristalsis sweeps the re mainder of the unhydrolyzed castor oil out of the bowel while the ricin oleic acid is still chemically com bined with glycerin. The customary dose of castor oil for cleansing the co lon for barium enema is 60 mL (2 oz). Bisacodyl acts on the colonic muco sa as a contact laxative by stimulating colonic peristalsis. The laxative effect is due to sensory nerve stimulation producing parasympathetic reflexes that increase colonic peristalsis. The parasympathetic effect of bisacodyl is due to local and segmental axon re flexes that are initiated in the region of contact. This action of bisacodyl is independent of intestinal absorption. The recommended dose of bisaco dyl for cleansing of the colon is 20 mg taken as four 5-mg tablets. Be cause the sensitivity of the colon to stimulation by bisacodyl may vary considerably, the effectiveness of the average dose of 20 mg may vary con siderably, and the response is fre quently less among the elderly. Fur thermore, since bisacodyl directly stimulates vigorous colonic contrac tions, abdominal cramps are an ex pected side effect in many individ uals. Senna extract is a cathartic ob tained from the botanicals Cassia acu tifolia and Cassia augustifolia
(2). Its use
as a laxative was introduced more than 1,100 years ago by Janus Damas cenus (777-857), court physician to the Caliph Haroun al-Raschid (3). Senna extract has gained consider able popularity as a preparation for the barium enema study in the form of a standardized extract of senna marketed under a specifically sugges tive brand name. As a preparation for the barium enema examination, the senna extract is provided in a fla vored aqueous solution. It is our opinion that effective cleansing of the colon can be achieved without the use of strong colonic irritants and their attendant abdominal discomfort. Indeed, it is necessary only to fill the colon with a considerable volume of fluid, wheth er from above or below, and the co lon will soon contract and evacuate without any further stimulation. At tempts have been made by radiolo gists to quantify the amount of dis comfort caused by various colon cleansing regimens. However, the best description of the discomfort of
a severe diarrhea almost certainly is to be found in the Scriptures: “¿I am poured out like water, and all my bones are out of joint: my heart is like wax; it is melted in the midst of my bowels―(4). THE CLEANSING
ENEMA
The primary reason for routinely administering a cleansing enema be fore the barium enema examination is to ensure that any fecal material re maining after the action of the ca thartics is removed from the colon (5). We believe that the cleansing en ema is the crucial element in prepar ing the colon for the barium enema study. The enema should consist of nothing more than 1,500 mL of warm tap water without addition of soaps or colonic irritants. Addition of soap like materials increases the likeli hood of bubbles and may seriously degrade the coating of the barium suspension during double-contrast examinations. Tannic acid, a potent colonic irritant, was used for many years in the cleansing enema, but it has fallen from use because of its po tential for causing liver damage. Af ter use of tannic acid was discredited, many radiologists began to add an ir ritant preparation containing bisaco dyl. We adopted and then dropped the use of bisacodyl in the cleansing enema when we found that it made no apparent difference in the amount of fluid retention following the cleansing enema, and similarly made no difference in the quality of the barium coating during subsequent double-contrast examinations. The cleansing enema should be ad ministered in three stages. The first 500 mL is administered with the pa tient on his or her left side, the sec ond 500 mL with the patient lying prone, and the third 500 mL with the patient on his or her right side. This routine usually ensures distribution of the cleansing enema throughout the colon. If the effluent of the en ema contains any solid fecal material, the enema should be repeated. The effectiveness of the cleansing enema is entirely a function of the care with which it is administered and a willingness to repeat the en ema if necessary. In our experience, the cleansing enema is best per formed in the radiology department by personnel who understand its im portance. Nursing personnel or busy hospital orderlies usually cannot be depended on to perform this task with the necessary diligence. After the cleansing enema is per March 1991
Recent Results of Regimens Used to Prepare the Colon for Barium Enema Study %SourceNo.
of et al, 1977 (7)
Slanger, 1979 (9) Brouwers et al, 1980 (10) Casal et at, 1980 (11)94 90Allen et al, 1980 (12) Lee et al, 1981 (13) Kendrick et al, 1981 (14)50 48Present et at, 1982 (15) Fork et at, 1982 (16) Benson and Harper, 1983(17) Shaw and Tait, 1983(18) Foord et al, 1983 (19) Virkki and MãkelS,1983 (20) Girard et at, 1984(21) Hawes et at, 1984 (22) Lee, 1984 (23)147 44Lee and Ferrando,
1984(24)
Chan eta!, 1985(25)20 61Van der Jagt et at, 1986 (26)46 49Hellström and Brolin, 1987 (27) Gelfand et al, 1988 (29)45
* Hoechst-Roussel,
otherwise
oil, 60-mL phosphate enema Castor oil, 60-mL phosphate enema, Surfak' Magnesium citrate, bisacodyl tablets, and suppository Magnesium citrate, bisacodyl tablets, and suppository, Surfak* Castor oil, senna extract, preparatory enema Bisacodyl tablets, preparatory enema Senna extract, no dietary restriction, single dose Senna extract, no dietary restriction, divided dose Senna extract, no dietary restriction Magnesium citrate, senna extract Magnesium citrate, castor oil Castor oil, senna extract57 oil 20 Senna extract, preparatory enema Senna extract, no dietary restriction 131 100Castor Senna extract96 extract, preparatory enema, no dietary restriction 125 Senna extract, preparatory enema 1435 Bisacodyl tablets, preparatory enema, no dietary restriction 94 Bisacodyl tablets, bisacodyl enema, no dietary restriction 128 Magnesium oxide, bisacodyl tablets, no dietary restriction 54 Magnesium oxide, bisacodyl tablets, preparatory enema, no dietary restriction 99 Magnesium citrate, bisacodyl tablets, and suppository 52 Magnesium citrate, bisacodyl tablets, and suppository 46 10% mannitol 48 Sodium picosulfate 39 Magnesium citrate, bisacodyl tablets 268 Bisacodyl tablets, preparatory enema 101 Magnesium citrate, bisacodyl tablets 17 Castor oil, senna extract, preparatory enema 20 Senna extract, no dietary restriction 20Senna Senna extract33 extract, preparatory enema, no dietary restriction 20 Senna extract, preparatory enema 20 Magnesium citrate 20 Magnesium citrate, bisacodyl tablets 20 Magnesium citrate, bisacodyl suppository 20 Magnesium citrate, bisacodyl tablets, and suppository Oral phosphosoda, bisacodyl tablets 25 41Senna Castor oil, senna extract30 oil, senna extract 47Castor Senna extract59 tablets, preparatory enema 500Bisacodyl Magnesium citrate, castor oil, preparatory enema56
noted, all regimens
Somerville,
included
54 83 84 42 60 100 86 67 93 85 55 15 77 90 91 91 96 32 90 79 96 95 96 80 76 28 49 63 50 58 46 30
97
dietary restriction.
NJ.
formed, sufficient time must elapse before the radiologic examination is performed to allow the patient to evacuate and/or absorb the fluid re maining in the colon. It is our policy that patients wait 30 minutes before a single-contrast examination and 60 minutes before a double-contrast ex amination. A recent investigation of this subject at St Marks Hospital of London found that the minimal in terval between the cleansing enema and the double-contrast examination should be 45 minutes (6), which somewhat confirms our own observa tions. The cleansing enema also provides two subsidiary functions. First, if the effluent from the enema contains a substantial amount of solid fecal ma terial, it is likely that the cathartics were not sufficiently effective. Un der this circumstance, the patient should be prepared for a 2nd day be fore undergoing examination. Sec ond, the cleansing enema also indi cates whether the patient has normal Volume 178 •¿ Number 3
Enemaswith
78 97 80 50 50 51 49 97 29 26 31Castor
Cargill and Hately, 1978 (8)
Note.—Unless
Clean
PatientsCathartics,
ColonDodds
sphincter control and will be able to retain the barium enema. If the pa tient has poor sphincter control or is infirm, we perform the more rapid and more easily performed single contrast barium enema study rather than a double-contrast examination. Most radiologists currently do not use cleansing enemas because of a fear of procedural difficulties within the department. Ideally, a small room for administering cleansing enemas and the help of a nursing aid should be available for this purpose. These facilities are available in our outpa tient fluoroscopy suite but are not, however, available in our inpatient fluoroscopy area. Our inpatients are given their cleansing enemas on the x-ray tables by the fluoroscopy tech nologists. The patients are then held in a waiting area for 30-60 minutes while other fluoroscopic examina tions are performed. This routine can be instituted in virtually any hospital radiology department. The cleansing enema is particularly necessary for
the preparation of chronically bed ridden, hospitalized patients in whom colonic cleansing is often very difficult. Once the technologists are aware of the importance of the colon being thoroughly cleansed, and once their initial period of complaint is past, the cleansing enemas are a mi nor burden. COMMON PREPARATION REGIMENS The following are opinions based on many years of experience in vari ous medical centers and on use of a wide variety of preparations to cleanse the colon for barium enema examinations. Unfortunately, pub lished reports on the effectiveness of various regimens for cleansing of the colon are inconclusive (Table) (6—27). This is due mainly to variability in the criteria used to define what con stitutes a clean colon. Indeed, in most of the articles noted, the criteria for a clean colon are not mentioned be Radiology •¿ 611
yond stating that the participating ra diologists believed a preparation was satisfactory or unsatisfactory. The wide variety of preparations current ly in use is reflected in a 1987 survey of the members of the Society of Gas trointestinal Radiologists on their techniques for examining the colon (28). Confronted with this inconclu sive literature, we can only offer the following opinions, which were formed on the basis of our experience with most of the colon-cleansing reg imens noted in the literature. Use of a single cathartic—such as castor oil, senna extract, or bisacodyl tablets—without addition of a cleans ing enema can be expected to result in a large percentage of poorly pre pared patients. Castor oil, senna ex tract, or bisacodyl as a single cathartic can be supplemented by cleansing enemas and will then provide a more satisfactory regimen, but this will not provide a universally effective prepa ration. Most recommended regimens now employ two cathartics, usually a sa line cathartic followed by an irritant cathartic. The theory behind this method is that the saline cathartic fills the small intestine and colon with fluid. The irritant cathartic then causes contractions of the colon that expel its contents. The most popular and most heavily promoted of these combinations is magnesium citrate followed by bisacodyl tablets. This regimen is efficacious in most pa tients without the addition of cleans ing enemas. However, a very signifi cant minority of patients prepared in this manner, particularly hospital ized patients, will have an unsatisfac tory amount of feces in the colon un less they also receive cleansing en emas. The number of patients with feces in the colon following this preparation is, in our experience and in published reports (6,16,20,23,24), sufficient to render the barium en ema study unreliable for detection of polypoid neoplasms unless a cleans ing enema is also employed. STANDARD BOWMAN PREPARATION
GRAY
The preparation used in our own department is based on a combina tion of laxatives originally suggested to us by Dr H. Ichikawa of Tokyo, supplemented by a cleansing enema. If possible, a clear liquid diet should be instituted 24 hours prior to the ex amination. During the day before the examination, patients are asked to drink 240 mL (8 oz) of water or other 612 •¿ Radiology
clear liquid each hour to facilitate the preparation and prevent dehydra tion. At 4 PM on the day preceding the examination, the patient receives 300 mL (10 oz) of magnesium citrate solution; at 8 PM, 60 mL (2 oz) of cas tor oil is administered. The saline ca thartic, magnesium citrate, draws flu id into the small bowel, which then enters the colon from above. Castor oil then causes a further volume of fluid to enter the colon due to its irri tant effect on the small intestine. The castor oil also acts as a mild colonic irritant and stimulates evacuation. This combination of laxatives is rela tively free of severe intestinal grip ing, since it does not contain a strong colonic irritant. During the morning of the examination, the patient re ceives a 1,500-mL cleansing enema in the radiology department, which is repeated as necessary to ensure a to tally clean colon. The patient then waits either 30 or 60 minutes, de pending on whether the examination is to be a single-contrast or double contrast examination, respectively. A recent review of 500 patients receiv ing this preparation in our depart ment indicated that 97% were virtual ly free of feces during the barium en ema study (29). Only 2% of patients retained sufficient fecal material to make the diagnosis of polypoid le sions unreliable in any segment of the colon.
al on single-contrast examinations is equally troublesome. One cannot de pend on the ability to sort filling de fects that move (feces) from fixed fill ing defects (polypoid lesions) when considerable fecal material is present. CONCLUSION Dr Miller was correct. For the radi ologist performing a barium enema study, happiness is indeed a clean co lon. With the colon totally clean, the radiologic detection of colorectal car cinoma becomes an almost foolproof exercise if adequate care is taken with the barium enema examination (30). Almost as important, detection of polypoid lesions, including those smaller than 1 cm, becomes very reli able (31,32). Regardless of the type of barium enema study performed, ef fective preparation of the colon is the key to an accurate examination. •¿ References 1. 2.
3.
4. 5. 6.
QUALITY CONTROL The ultimate quality control is use of the cleansing enema, since if the effluent of a 1,500-mL enema is clear, it can be safely assumed that the co lon is clean. If a cleansing enema is not used, then a quality-control pro gram should be instituted to ensure that fecal material in the colon dur ing examination is not, in fact, a problem. The program can consist of sequential recording of the quality of colonic cleansing in 20 serial barium enema examinations. If more than one or two examinations show any fecal material at all, the regimen should be changed, probably by in stituting use of cleansing enemas. We do not agree with those who claim that fecal material does not interfere with diagnosis of lesions on double contrast examinations, in that the fe cal material will probably fall into the barium pool when the decubitus images are taken. In fact, small bits of feces may cling to the walls of the co lon, mimicking small polyps and de creasing the accuracy of diagnosis of such lesions. Significant fecal materi
7.
8.
9.
10.
11.
12.
13.
14.
15.
Miller RE. The clean colon. Gastroenter ology 1976; 70:289-290. Goodman LS, Gilman A. The pharmaco logical basis of therapeutics. New York: MacMillan; 1956, 1043—1058. LaWall CH. The curious lore of drugs and medicines. Garden City, NJ: Garden City Publishing, 1927; 103, 427. Psalms 22:14. Miller RE. The cleansing enema. Radiolo gy 1975; 117:483-485. Lee SH, Bartram CI. Determining the minimal interval between cleansing water enema and double-contrast barium enema examination. Clin Radiol 1990; 41:331332.
Dodds WJ, Scanlon CT, Shaw DK, et al. An evaluation of colon cleansing regi mens. AJR 1977; 128:57-59. Cargill A, Hately W. Preparation of the colon prior to radiology—a comparison of the effectiveness of castor oil, Dulcodos and X-Prep liquid. Br J Radiol 1978; 51:910-912. Slanger A. Comparative study of a stan dardized senna liquid and castor oil in preparing patients for radiographic exam ination of the colon. Dis Colon Rectum 1979; 22:356—359. Brouwers JRBJ, van Ouwerkerk WPL, de Boer SM, et al. A controlled trial of senna preparations and other laxatives used for bowel cleansing prior to radiological ex amination. Pharmacology 1980; 20:58-64. Casal CL, Martinez LO, Silberman MR. Preparation of the colon for barium en ema. Gastrointest Endosc 1980; 26(suppl):55—65. Allen C, Allen EP, Harding WR, et at. Preparation of the colon prior to radiolo gy. Br J Radiol 1980; 53:737. Lee JR. Hares MM, Keighley MRB. A ran domized trial to investigate X-Prep, oral mannitol and colonic washout for double contrast barium enema. Clin Radiol 1981; 32:591-594. Kendrick RCM, MacKenzie S, Beckly DE. A comparison of four methods of bowel preparation for barium enema. Clin Ra diol 1981; 32:95-97. Present AJ, Jansson B, Burhenne HJ, et at.
March 1991
16.
17.
18.
19.
20.
21.
Evaluation of 12 co!on-c!eansing regimens with single-contrast barium enema. AJR 1982; 139:855-860. Fork FT, Ekberg 0, Nilsson C, eta!. Co lon cleansing regimens: a clinical study in 1200 patients. Gastrointest Radio! 1982; 7:383—389. Benson M, Harper J. A comparative dou ble-blind trial of mannito! and magne sium citrate/bisacody! (MCB) in the prep aration of barium enema patients. Austra las Radio! 1983; 27:25—26. Shaw MRP, Tait KB. A clinical compari son of bowel preparations prior to double contrast barium enema. Australas Radio! 1983; 27:254—257. Foord KD, Morcos SK, Ward P. A com parison of mannitol and magnesium cit rate preparations for double-contrast bari um enema. C!in Radiol 1983; 34:309-312. Virkki R, Mãkelã P. Low residual diet and hydration improving double contrast examination of the colon. Eur J Radio! 1983; 3:212-214. Girard CM, Rugh KS, DiPa!ma JA, et al. Comparison of Golyte!y lavage with stan
22.
23.
24.
25.
26.
27.
dard diet/cathartic preparation for dou b!e-contrast barium enema. AJR 1984; 142:1147-1149. Hawes RH, Lehman GA, Brunel!e RL, et a!. Comparative efficacy of colon-cleans ing methods: standard preparation vs. co limmac lavage. AIR 1984; 142:309-310. Lee JR. Combinations of laxatives for bowel preparation: are they necessary? Clin Radio! 1984; 35:461-462. Lee JR. Ferrando JR. Variables in the preparation of the large intestine for dou ble contrast barium enema examination. Gut 1984; 25:69-72. Chan CH, Diner WC, Fontenot E, eta!. Randomized sing!e-blind clinical trial of a rapid co!onic lavage solution (Cotyte!y) vs. standard preparation for barium en ema and co!onoscopy. Gastrointest Radiol 1985; 10:378—382. Van Der Jagt EJ, Thijn CJ, Taverne PP. Colon cleansing prior to roentgenologic examination: a double blind comparative study. JBR-BTR 1986; 69:167-170. HellstrOm M, Bro!in I. Dietary fibers in the preparation of the bowel for diagnos
28.
29.
30.
31.
32.
tic barium enema. Gastrointest Radiol 1987; 12:76-78. Thoeni RF, Marqulis AR. The state of ra diographic technique in the examination of the co!on: a survey in 1987. Radiology 1988; 167:7—12. Ge!fand DW, Chen YM, Ott DJ. Colonic cleansing for radiographic detection of neoplasia: efficacy of the magnesium cit rate-castor oil-cleansing enema regimen. AJR 1988; 151:705-708. Gelfand DW, Chen YM, Ott DJ. Radio logic detection of colonic neoplasms: benefits of a system analysis approach. AJR (in press). Ott DJ, Chen YM, Ge!fand DW, Wu WC, Munitz HA. Single-contrast vs. double contrast barium enema in the detection of co!onic po!yps. AJR 1986; 146:993-996. Ce!fand DW, Chen YM, Ott DJ. Detec tion of co!onic polyps on single-contrast barium enema study: emphasis on the el derly. Radiology 1987; 164:333—337.
This
@ Volume 178 •¿ Number 3
One
I@ UI@III I0hUll II@ I0hIIIllI@ lID II@lI DRZL-AGF-3Y5F
Radiology
613
Preparing the Colon for the Barium Enema Examination' ADIOLOGISTS
attending
meetings
of the Society of Gastrointesti nal Radiologists often saw the late Dr Roscoe E. Miller with a button in his lapel that read “¿Happinessis a Clean Colon―(1). One was never certain whether Dr Miller intended this as a general statement or in reference to the barium enema examination. The radiologic examination of the colon has been performed for ap proximately 90 years. Almost from the beginning, there has been con troversy over the methods used to prepare the colon for the examina tion. Herein, we present a review of the subject of cleansing the colon in preparation for the barium enema and discuss (a) dietary restrictions, (b) common cathartics and their methods of action, (c) the use of the cleansing enema, (d) observations on commonly used preparations, (e) our own regimen for colonic cleansing, and (f) quality controls for ensuring adequate preparation. DIETARY RESTRICTION Most colon cleansing regimens use dietary restriction to reduce the amount of the fecal material that must be removed by cathartics. The majority of these require a low-resi due or liquid diet be consumed for at least 24 hours. This requirement is appropriate and helpful, particularly
Index terms: Barium enema examination. Colon, radiography, 75.128 •¿ State-of-art re views Radiology
@
1991; 178:609-613
‘¿Fromthe Department of Radiology, Bow man Gray School of Medicine, Winston-Salem, NC 27103. Received October 2, 1990; accepted October 29. Address reprint requests to D.W.G. RSNA, 1991
in an outpatient setting. However, because of the necessity to minimize the length of hospitalizations, 24 hours may not be available between the request for a barium enema ex amination and its performance. Al though 24 hours of dietary restriction is indeed helpful, the colon cleansing regimen in use at Bowman Gray School of Medicine, which is de scribed herein, has proved highly ef fective in patients in whom only a few hours of dietary restriction is possible (1). CATHARTICS Cathartics are drugs that promote defecation, although in common ter minology they are more often re ferred to as laxatives. Also, textbooks of pharmacology may use the terms laxative, cathartic, and purgative to describe this class of drugs according to the intensity of their action, in in creasing order of potency. Colon cleansing regimens very often com bine use of a saline cathartic with an irritant cathartic administered sever al hours later. Saline cathartics share a common mechanism of action in that they contain inorganic ions that are slow ly absorbed from the intestines. These ions include the cation magne sium and the anions citrate, sulfate, and phosphate. They are retained in the small intestine for a considerable time after being ingested. During this period, the intestinal mucosa acts as a semipermeable membrane divid ing the patient's circulation from the intestinal contents (2). Since the in testinal mucosa is permeable to wa ter, water tends to pass from the cir culation into the intestinal tract until the cathartic salt solution becomes isotonic with the extracellular fluid. The resulting large volume of fluid retained in the intestines stimulates peristalsis. After reaching the colon, the abnormally expanded colonic
contents are expelled. Magnesium citrate is the most com monly used of the saline cathartics. Magnesium citrate solution is widely available as a flavored water solution of the salt in 300-mL bottles. Addi tion of sodium bicarbonate and citric acid provides effervescence. Magnesium oxide acts as a cathartic after conversion into water-soluble salts within the gastrointestinal tract. In the oxide form, it is almost insolu ble in water. The usual cathartic dose for cleansing of the colon is 3—4g. supplied as tablets. Sodium phosphate (phosphosoda) also is an effective saline cathartic. In its most common form, it is supplied as a proprietary combination of sodi urn phosphate and sodium biphos phate in 100 mL of aqueous solution. Certain precautions must be main tained when using saline cathartics. The magnesium ion is partially ab sorbed after oral administration. Nor mally, the kidneys so rapidly excrete the magnesium ion that changes in its level in the blood cannot be de tected. However, if magnesium ion is administered to a patient with im paired renal function, levels of mag nesium ion in the extracellular fluid may become sufficiently elevated to produce magnesium poisoning. The use of magnesium citrate or magne sium oxide is therefore inadvisable in patients with poor renal function. Sodium phosphate cathartics con tain sufficient sodium and phosphate ions to produce both hypernatremia and hyperphosphatemia in patients with decreased renal function. These products also are contraindicated in patients with congestive heart failure or who are on a low-salt diet, since the sodium ion is readily absorbed. In patients with decreased renal function, hypocalcemia also may occur. Intestinal lavage is a variant use of saline cathartics in which a very large volume of an isotonic, nonab 609
sorbable solution is administered for the purpose of flushing the contents of the colon from above. The most commonly used of several commer cially available proprietary solutions contains polyethylene glycol, sodium sulfate, sodium bicarbonate, sodium chloride, and potassium chloride dis solved in water to a final volume of 4 L. After the patient has fasted for 4 hours, the solution is ingested at a rate of 240 mL (8 oz) every 10 mm utes until the rectal effluent is clear or the entire 4 L has been consumed. Despite the massive volume of fluid ingested, there is little systemic ab sorption of water or salts. This meth od of colonic cleansing finds its greatest use as a preparation for co lonoscopy. Its major disadvantage as a preparation for the barium enema examination is the significant amount of fluid usually found in the colon after its use. Its use is also asso ciated with abdominal discomfort in a significant minority of patients. Irritant cathartics are often used for cleansing the colon for a barium enema examination either alone or, more commonly, in combination with a saline cathartic. The irritant cathartics most frequently employed in preparation for the barium enema study are castor oil, senna extract, and bisacodyl. Castor oil is obtained from the cas tor bean, the seed of Ricinus communis. The various uses of castor oil appar ently have been known for thou sands of years, since the castor bean is depicted in ancient Egyptian wall paintings (3). As extracted from the bean, castor oil is in the form of the triglyceride of ricinoleic acid, an un saturated fatty acid. Within the small intestine, castor oil is hydrolyzed to glycerol and ricinoleic acid, the latter substance being the active cathartic agent (2). Ricinoleic acid greatly stimulates motor activity of the small intestine by means of a local irritant action. This increases peristalsis and causes a rapid propulsion of the small-intesti nal contents into the colon. The ca thartic action of castor oil is not caused by diffusion of additional flu id into the small intestine, but results from the rapid passage of the normal intestinal contents into the colon be fore they can be absorbed. Because al most all of the ricinoleic acid is ab sorbed in the small intestine, there is only mild stimulation of the colon. As a result, contrary to common per ception, there is relatively little intes tinal griping associated with the ca thartic action of castor oil. 610 •¿ Radiology
Castor oil is a particularly safe ca thartic in that hydrolysis of only a portion of the ingested castor oil pro duces sufficient ricinoleic acid to irri tate the small intestine. The resulting increased peristalsis sweeps the re mainder of the unhydrolyzed castor oil out of the bowel while the ricin oleic acid is still chemically com bined with glycerin. The customary dose of castor oil for cleansing the co lon for barium enema is 60 mL (2 oz). Bisacodyl acts on the colonic muco sa as a contact laxative by stimulating colonic peristalsis. The laxative effect is due to sensory nerve stimulation producing parasympathetic reflexes that increase colonic peristalsis. The parasympathetic effect of bisacodyl is due to local and segmental axon re flexes that are initiated in the region of contact. This action of bisacodyl is independent of intestinal absorption. The recommended dose of bisaco dyl for cleansing of the colon is 20 mg taken as four 5-mg tablets. Be cause the sensitivity of the colon to stimulation by bisacodyl may vary considerably, the effectiveness of the average dose of 20 mg may vary con siderably, and the response is fre quently less among the elderly. Fur thermore, since bisacodyl directly stimulates vigorous colonic contrac tions, abdominal cramps are an ex pected side effect in many individ uals. Senna extract is a cathartic ob tained from the botanicals Cassia acu tifolia and Cassia augustifolia
(2). Its use
as a laxative was introduced more than 1,100 years ago by Janus Damas cenus (777-857), court physician to the Caliph Haroun al-Raschid (3). Senna extract has gained consider able popularity as a preparation for the barium enema study in the form of a standardized extract of senna marketed under a specifically sugges tive brand name. As a preparation for the barium enema examination, the senna extract is provided in a fla vored aqueous solution. It is our opinion that effective cleansing of the colon can be achieved without the use of strong colonic irritants and their attendant abdominal discomfort. Indeed, it is necessary only to fill the colon with a considerable volume of fluid, wheth er from above or below, and the co lon will soon contract and evacuate without any further stimulation. At tempts have been made by radiolo gists to quantify the amount of dis comfort caused by various colon cleansing regimens. However, the best description of the discomfort of
a severe diarrhea almost certainly is to be found in the Scriptures: “¿I am poured out like water, and all my bones are out of joint: my heart is like wax; it is melted in the midst of my bowels―(4). THE CLEANSING
ENEMA
The primary reason for routinely administering a cleansing enema be fore the barium enema examination is to ensure that any fecal material re maining after the action of the ca thartics is removed from the colon (5). We believe that the cleansing en ema is the crucial element in prepar ing the colon for the barium enema study. The enema should consist of nothing more than 1,500 mL of warm tap water without addition of soaps or colonic irritants. Addition of soap like materials increases the likeli hood of bubbles and may seriously degrade the coating of the barium suspension during double-contrast examinations. Tannic acid, a potent colonic irritant, was used for many years in the cleansing enema, but it has fallen from use because of its po tential for causing liver damage. Af ter use of tannic acid was discredited, many radiologists began to add an ir ritant preparation containing bisaco dyl. We adopted and then dropped the use of bisacodyl in the cleansing enema when we found that it made no apparent difference in the amount of fluid retention following the cleansing enema, and similarly made no difference in the quality of the barium coating during subsequent double-contrast examinations. The cleansing enema should be ad ministered in three stages. The first 500 mL is administered with the pa tient on his or her left side, the sec ond 500 mL with the patient lying prone, and the third 500 mL with the patient on his or her right side. This routine usually ensures distribution of the cleansing enema throughout the colon. If the effluent of the en ema contains any solid fecal material, the enema should be repeated. The effectiveness of the cleansing enema is entirely a function of the care with which it is administered and a willingness to repeat the en ema if necessary. In our experience, the cleansing enema is best per formed in the radiology department by personnel who understand its im portance. Nursing personnel or busy hospital orderlies usually cannot be depended on to perform this task with the necessary diligence. After the cleansing enema is per March 1991
Recent Results of Regimens Used to Prepare the Colon for Barium Enema Study %SourceNo.
of et al, 1977 (7)
Slanger, 1979 (9) Brouwers et al, 1980 (10) Casal et at, 1980 (11)94 90Allen et al, 1980 (12) Lee et al, 1981 (13) Kendrick et al, 1981 (14)50 48Present et at, 1982 (15) Fork et at, 1982 (16) Benson and Harper, 1983(17) Shaw and Tait, 1983(18) Foord et al, 1983 (19) Virkki and MãkelS,1983 (20) Girard et at, 1984(21) Hawes et at, 1984 (22) Lee, 1984 (23)147 44Lee and Ferrando,
1984(24)
Chan eta!, 1985(25)20 61Van der Jagt et at, 1986 (26)46 49Hellström and Brolin, 1987 (27) Gelfand et al, 1988 (29)45
* Hoechst-Roussel,
otherwise
oil, 60-mL phosphate enema Castor oil, 60-mL phosphate enema, Surfak' Magnesium citrate, bisacodyl tablets, and suppository Magnesium citrate, bisacodyl tablets, and suppository, Surfak* Castor oil, senna extract, preparatory enema Bisacodyl tablets, preparatory enema Senna extract, no dietary restriction, single dose Senna extract, no dietary restriction, divided dose Senna extract, no dietary restriction Magnesium citrate, senna extract Magnesium citrate, castor oil Castor oil, senna extract57 oil 20 Senna extract, preparatory enema Senna extract, no dietary restriction 131 100Castor Senna extract96 extract, preparatory enema, no dietary restriction 125 Senna extract, preparatory enema 1435 Bisacodyl tablets, preparatory enema, no dietary restriction 94 Bisacodyl tablets, bisacodyl enema, no dietary restriction 128 Magnesium oxide, bisacodyl tablets, no dietary restriction 54 Magnesium oxide, bisacodyl tablets, preparatory enema, no dietary restriction 99 Magnesium citrate, bisacodyl tablets, and suppository 52 Magnesium citrate, bisacodyl tablets, and suppository 46 10% mannitol 48 Sodium picosulfate 39 Magnesium citrate, bisacodyl tablets 268 Bisacodyl tablets, preparatory enema 101 Magnesium citrate, bisacodyl tablets 17 Castor oil, senna extract, preparatory enema 20 Senna extract, no dietary restriction 20Senna Senna extract33 extract, preparatory enema, no dietary restriction 20 Senna extract, preparatory enema 20 Magnesium citrate 20 Magnesium citrate, bisacodyl tablets 20 Magnesium citrate, bisacodyl suppository 20 Magnesium citrate, bisacodyl tablets, and suppository Oral phosphosoda, bisacodyl tablets 25 41Senna Castor oil, senna extract30 oil, senna extract 47Castor Senna extract59 tablets, preparatory enema 500Bisacodyl Magnesium citrate, castor oil, preparatory enema56
noted, all regimens
Somerville,
included
54 83 84 42 60 100 86 67 93 85 55 15 77 90 91 91 96 32 90 79 96 95 96 80 76 28 49 63 50 58 46 30
97
dietary restriction.
NJ.
formed, sufficient time must elapse before the radiologic examination is performed to allow the patient to evacuate and/or absorb the fluid re maining in the colon. It is our policy that patients wait 30 minutes before a single-contrast examination and 60 minutes before a double-contrast ex amination. A recent investigation of this subject at St Marks Hospital of London found that the minimal in terval between the cleansing enema and the double-contrast examination should be 45 minutes (6), which somewhat confirms our own observa tions. The cleansing enema also provides two subsidiary functions. First, if the effluent from the enema contains a substantial amount of solid fecal ma terial, it is likely that the cathartics were not sufficiently effective. Un der this circumstance, the patient should be prepared for a 2nd day be fore undergoing examination. Sec ond, the cleansing enema also indi cates whether the patient has normal Volume 178 •¿ Number 3
Enemaswith
78 97 80 50 50 51 49 97 29 26 31Castor
Cargill and Hately, 1978 (8)
Note.—Unless
Clean
PatientsCathartics,
ColonDodds
sphincter control and will be able to retain the barium enema. If the pa tient has poor sphincter control or is infirm, we perform the more rapid and more easily performed single contrast barium enema study rather than a double-contrast examination. Most radiologists currently do not use cleansing enemas because of a fear of procedural difficulties within the department. Ideally, a small room for administering cleansing enemas and the help of a nursing aid should be available for this purpose. These facilities are available in our outpa tient fluoroscopy suite but are not, however, available in our inpatient fluoroscopy area. Our inpatients are given their cleansing enemas on the x-ray tables by the fluoroscopy tech nologists. The patients are then held in a waiting area for 30-60 minutes while other fluoroscopic examina tions are performed. This routine can be instituted in virtually any hospital radiology department. The cleansing enema is particularly necessary for
the preparation of chronically bed ridden, hospitalized patients in whom colonic cleansing is often very difficult. Once the technologists are aware of the importance of the colon being thoroughly cleansed, and once their initial period of complaint is past, the cleansing enemas are a mi nor burden. COMMON PREPARATION REGIMENS The following are opinions based on many years of experience in vari ous medical centers and on use of a wide variety of preparations to cleanse the colon for barium enema examinations. Unfortunately, pub lished reports on the effectiveness of various regimens for cleansing of the colon are inconclusive (Table) (6—27). This is due mainly to variability in the criteria used to define what con stitutes a clean colon. Indeed, in most of the articles noted, the criteria for a clean colon are not mentioned be Radiology •¿ 611
yond stating that the participating ra diologists believed a preparation was satisfactory or unsatisfactory. The wide variety of preparations current ly in use is reflected in a 1987 survey of the members of the Society of Gas trointestinal Radiologists on their techniques for examining the colon (28). Confronted with this inconclu sive literature, we can only offer the following opinions, which were formed on the basis of our experience with most of the colon-cleansing reg imens noted in the literature. Use of a single cathartic—such as castor oil, senna extract, or bisacodyl tablets—without addition of a cleans ing enema can be expected to result in a large percentage of poorly pre pared patients. Castor oil, senna ex tract, or bisacodyl as a single cathartic can be supplemented by cleansing enemas and will then provide a more satisfactory regimen, but this will not provide a universally effective prepa ration. Most recommended regimens now employ two cathartics, usually a sa line cathartic followed by an irritant cathartic. The theory behind this method is that the saline cathartic fills the small intestine and colon with fluid. The irritant cathartic then causes contractions of the colon that expel its contents. The most popular and most heavily promoted of these combinations is magnesium citrate followed by bisacodyl tablets. This regimen is efficacious in most pa tients without the addition of cleans ing enemas. However, a very signifi cant minority of patients prepared in this manner, particularly hospital ized patients, will have an unsatisfac tory amount of feces in the colon un less they also receive cleansing en emas. The number of patients with feces in the colon following this preparation is, in our experience and in published reports (6,16,20,23,24), sufficient to render the barium en ema study unreliable for detection of polypoid neoplasms unless a cleans ing enema is also employed. STANDARD BOWMAN PREPARATION
GRAY
The preparation used in our own department is based on a combina tion of laxatives originally suggested to us by Dr H. Ichikawa of Tokyo, supplemented by a cleansing enema. If possible, a clear liquid diet should be instituted 24 hours prior to the ex amination. During the day before the examination, patients are asked to drink 240 mL (8 oz) of water or other 612 •¿ Radiology
clear liquid each hour to facilitate the preparation and prevent dehydra tion. At 4 PM on the day preceding the examination, the patient receives 300 mL (10 oz) of magnesium citrate solution; at 8 PM, 60 mL (2 oz) of cas tor oil is administered. The saline ca thartic, magnesium citrate, draws flu id into the small bowel, which then enters the colon from above. Castor oil then causes a further volume of fluid to enter the colon due to its irri tant effect on the small intestine. The castor oil also acts as a mild colonic irritant and stimulates evacuation. This combination of laxatives is rela tively free of severe intestinal grip ing, since it does not contain a strong colonic irritant. During the morning of the examination, the patient re ceives a 1,500-mL cleansing enema in the radiology department, which is repeated as necessary to ensure a to tally clean colon. The patient then waits either 30 or 60 minutes, de pending on whether the examination is to be a single-contrast or double contrast examination, respectively. A recent review of 500 patients receiv ing this preparation in our depart ment indicated that 97% were virtual ly free of feces during the barium en ema study (29). Only 2% of patients retained sufficient fecal material to make the diagnosis of polypoid le sions unreliable in any segment of the colon.
al on single-contrast examinations is equally troublesome. One cannot de pend on the ability to sort filling de fects that move (feces) from fixed fill ing defects (polypoid lesions) when considerable fecal material is present. CONCLUSION Dr Miller was correct. For the radi ologist performing a barium enema study, happiness is indeed a clean co lon. With the colon totally clean, the radiologic detection of colorectal car cinoma becomes an almost foolproof exercise if adequate care is taken with the barium enema examination (30). Almost as important, detection of polypoid lesions, including those smaller than 1 cm, becomes very reli able (31,32). Regardless of the type of barium enema study performed, ef fective preparation of the colon is the key to an accurate examination. •¿ References 1. 2.
3.
4. 5. 6.
QUALITY CONTROL The ultimate quality control is use of the cleansing enema, since if the effluent of a 1,500-mL enema is clear, it can be safely assumed that the co lon is clean. If a cleansing enema is not used, then a quality-control pro gram should be instituted to ensure that fecal material in the colon dur ing examination is not, in fact, a problem. The program can consist of sequential recording of the quality of colonic cleansing in 20 serial barium enema examinations. If more than one or two examinations show any fecal material at all, the regimen should be changed, probably by in stituting use of cleansing enemas. We do not agree with those who claim that fecal material does not interfere with diagnosis of lesions on double contrast examinations, in that the fe cal material will probably fall into the barium pool when the decubitus images are taken. In fact, small bits of feces may cling to the walls of the co lon, mimicking small polyps and de creasing the accuracy of diagnosis of such lesions. Significant fecal materi
7.
8.
9.
10.
11.
12.
13.
14.
15.
Miller RE. The clean colon. Gastroenter ology 1976; 70:289-290. Goodman LS, Gilman A. The pharmaco logical basis of therapeutics. New York: MacMillan; 1956, 1043—1058. LaWall CH. The curious lore of drugs and medicines. Garden City, NJ: Garden City Publishing, 1927; 103, 427. Psalms 22:14. Miller RE. The cleansing enema. Radiolo gy 1975; 117:483-485. Lee SH, Bartram CI. Determining the minimal interval between cleansing water enema and double-contrast barium enema examination. Clin Radiol 1990; 41:331332.
Dodds WJ, Scanlon CT, Shaw DK, et al. An evaluation of colon cleansing regi mens. AJR 1977; 128:57-59. Cargill A, Hately W. Preparation of the colon prior to radiology—a comparison of the effectiveness of castor oil, Dulcodos and X-Prep liquid. Br J Radiol 1978; 51:910-912. Slanger A. Comparative study of a stan dardized senna liquid and castor oil in preparing patients for radiographic exam ination of the colon. Dis Colon Rectum 1979; 22:356—359. Brouwers JRBJ, van Ouwerkerk WPL, de Boer SM, et al. A controlled trial of senna preparations and other laxatives used for bowel cleansing prior to radiological ex amination. Pharmacology 1980; 20:58-64. Casal CL, Martinez LO, Silberman MR. Preparation of the colon for barium en ema. Gastrointest Endosc 1980; 26(suppl):55—65. Allen C, Allen EP, Harding WR, et at. Preparation of the colon prior to radiolo gy. Br J Radiol 1980; 53:737. Lee JR. Hares MM, Keighley MRB. A ran domized trial to investigate X-Prep, oral mannitol and colonic washout for double contrast barium enema. Clin Radiol 1981; 32:591-594. Kendrick RCM, MacKenzie S, Beckly DE. A comparison of four methods of bowel preparation for barium enema. Clin Ra diol 1981; 32:95-97. Present AJ, Jansson B, Burhenne HJ, et at.
March 1991
16.
17.
18.
19.
20.
21.
Evaluation of 12 co!on-c!eansing regimens with single-contrast barium enema. AJR 1982; 139:855-860. Fork FT, Ekberg 0, Nilsson C, eta!. Co lon cleansing regimens: a clinical study in 1200 patients. Gastrointest Radio! 1982; 7:383—389. Benson M, Harper J. A comparative dou ble-blind trial of mannito! and magne sium citrate/bisacody! (MCB) in the prep aration of barium enema patients. Austra las Radio! 1983; 27:25—26. Shaw MRP, Tait KB. A clinical compari son of bowel preparations prior to double contrast barium enema. Australas Radio! 1983; 27:254—257. Foord KD, Morcos SK, Ward P. A com parison of mannitol and magnesium cit rate preparations for double-contrast bari um enema. C!in Radiol 1983; 34:309-312. Virkki R, Mãkelã P. Low residual diet and hydration improving double contrast examination of the colon. Eur J Radio! 1983; 3:212-214. Girard CM, Rugh KS, DiPa!ma JA, et al. Comparison of Golyte!y lavage with stan
22.
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dard diet/cathartic preparation for dou b!e-contrast barium enema. AJR 1984; 142:1147-1149. Hawes RH, Lehman GA, Brunel!e RL, et a!. Comparative efficacy of colon-cleans ing methods: standard preparation vs. co limmac lavage. AIR 1984; 142:309-310. Lee JR. Combinations of laxatives for bowel preparation: are they necessary? Clin Radio! 1984; 35:461-462. Lee JR. Ferrando JR. Variables in the preparation of the large intestine for dou ble contrast barium enema examination. Gut 1984; 25:69-72. Chan CH, Diner WC, Fontenot E, eta!. Randomized sing!e-blind clinical trial of a rapid co!onic lavage solution (Cotyte!y) vs. standard preparation for barium en ema and co!onoscopy. Gastrointest Radiol 1985; 10:378—382. Van Der Jagt EJ, Thijn CJ, Taverne PP. Colon cleansing prior to roentgenologic examination: a double blind comparative study. JBR-BTR 1986; 69:167-170. HellstrOm M, Bro!in I. Dietary fibers in the preparation of the bowel for diagnos
28.
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tic barium enema. Gastrointest Radiol 1987; 12:76-78. Thoeni RF, Marqulis AR. The state of ra diographic technique in the examination of the co!on: a survey in 1987. Radiology 1988; 167:7—12. Ge!fand DW, Chen YM, Ott DJ. Colonic cleansing for radiographic detection of neoplasia: efficacy of the magnesium cit rate-castor oil-cleansing enema regimen. AJR 1988; 151:705-708. Gelfand DW, Chen YM, Ott DJ. Radio logic detection of colonic neoplasms: benefits of a system analysis approach. AJR (in press). Ott DJ, Chen YM, Ge!fand DW, Wu WC, Munitz HA. Single-contrast vs. double contrast barium enema in the detection of co!onic po!yps. AJR 1986; 146:993-996. Ce!fand DW, Chen YM, Ott DJ. Detec tion of co!onic polyps on single-contrast barium enema study: emphasis on the el derly. Radiology 1987; 164:333—337.
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