sodium phosphate ( nap ) is a key component of the standard bowel preparation regimen for colon capsule endoscopy ( cce , pillcom colon2 capsule endoscopy : medtronic , minneapolis , mn , usa ) , particularly to cause excretion of the capsule endoscope while the battery is still functioning . previous reports have demonstrated that other laxatives including polyethylene glycol and magnesium citrate were not effective for excreting the capsule endoscope 1 
 2 
 3 . however , the use of nap is limited due to the possibility of causing severe adverse events , e.  g. acute phosphate nephropathy , acute renal failure , hypertension , or mineral imbalance 4 
 5 . the u.s . food and drug administration issued a warning to restrict its purchase without a prescription in 2008 .  in japan , administration of nap for hypertensive patients therefore , an alternative to nap is needed to perform cce safely with a high completion rate . according to the latest report investigating the performance of cce compared with ct colonography 6 , gastrografin ( the water - soluble iodinated radiopaque oral contrast medium ) was first used for the cce regimen , because gastrografin is generally used as part of the ct colonography regimen for  fecal tagging  7 . in our experience , a cce regimen using gastrografin without nap , achieved a very high capsule excretion rate . the gastrointestinal transit time as well as the colon transit time with this bowel preparation regimen were comparable to that of cce regimens using a nap booster . in this paper , we report the results of a pilot study using gastrografin as a booster in the bowel preparation regimen for cce . from june 2014 to november 2014 , 29 patients in two tertiary care hospitals ( aizu medical center and otaru ekiseikai general hospital ) underwent cce , covered by the national health insurance system of japan . to be eligible for insurance payment for colon capsule endoscopy , the patient must meet standardized indications for colon screening as well as one of the following conditions including : a previously incomplete colonoscopy , a previous laparotomy , or being unable to undergo colonoscopy due to some organic abnormality . sixteen patients ( 55  % ) underwent the procedure to evaluate a positive fecal immunochemical test . patients had low residue meals at breakfast and lunch , and drank 1  l of polyethylene glycol ( peg ) plus ascorbic acid with 0.5  l of water in the evening , and 10  ml of sodium picosulfate hydrate at bedtime . on the morning of the examination , patients again drank 1  l of peg plus ascorbic acid with 0.5  l of water . after capsule ingestion , 50  ml of gastrografin diluted with 0.9  l of magnesium citrate was administered to facilitate capsule excretion . if the capsule was not expelled within 4 hours of ingestion , 50  ml of gastrografin with water ( by mouth ) and/or a bisacodyl suppository were added . the capsule excretion rate within the duration of battery life , gastrointestinal transit time , colon transit time , bowel cleansing , and yield of colon polyp identification were measured . bowel cleansing was rated on a four - point scale ( poor , fair , good , excellent ) to describe the preparation of the colon at the time of the capsule endoscopy 8 
 9 . moviprep : polyethylene glycol  +  ascorbic acid ; laxoberon : sodium picosulfate hydrate ; magcorol p : magnesium citrate ; gastrografin : diatrizoate meglumine and diatrizoate sodium . the one patient who did not expel the capsule within the duration of battery life was a 51-year - old man with severe diverticular disease of the sigmoid colon . gastrointestinal transit time , colon transit time , bowel cleansing , and yield of colon polyps are shown in table  3 . median colon transit time was 165 minutes and rapid transit (  <  40 minutes ) through the colon occurred in one patient ( 3.4  % , 1/29 ) . bowel cleansing was adequate ( excellent / good ) in 90  % of patients . the polyp (   6  mm ) detection rate was 52  % . all patients followed our regimen and diluted gastrografin was well tolerated by all of them . in our cce regimen without nap , but using gastrografin instead , the capsule excretion rate , gastrointestinal transit time , colon transit time , and bowel cleansing were equivalent to previous reports using nap as a booster 6 
 10 
 11 . gastrografin , known generically as diatrizoate meglumine and diatrizoate sodium , was developed as a water - soluble iodinated radiopaque oral contrast medium in 1960 , and is still used in radiographic examinations because of its unique characteristics . according to the manufacturer s information [ http://www.bayerhealthcare.at/de/produkte/g-l/gastrografin/index.php ] , the osmolality of gastrografin is nine times as high as that of blood plasma although the osmolality of nap could be more than 30 times higher in preliminary calculations . while nap is likely to increase the serum level of inorganic phosphate due to high phosphate level , most of the gastrografin is not absorbed from the intestinal tract into the circulation . overall ,   2  % of gastrografin is excreted into the urine without being metabolized . these characteristics suggest that an electrolyte imbalance is less frequently caused by oral / anal administration of gastrografin . gastrografin is a safe hyperosmotic laxative , and is a booster suitable for patients at increased risk . in this pilot study , the latest clinical trial 12 conducted in the united states used a sulfate solution ( suprep ; braintree laboratories ) as a booster for colon capsule endoscopy . in this large clinical trial , the median colon transit time was 75 minutes and occasionally the capsule passed through the colon within 40 minutes . subsequently , approximately 10  % ( 77/772 ) of subjects were excluded from the final analysis , based on the combination of poor preparation and rapid transit after enrollment . because the sulfate solution is poorly absorbed , the osmotic effect of unabsorbed sulfate anions and associated cations causes water to be retained within the intestine , thus expelling the capsule in a short time . in the present study using gastrografin as a booster , the median colon transit time ( 165 minutes ) was longer than that in the clinical trial using a sulfate solution . indeed , the polyp (   6  mm ) detection rate was comparably high ( 52  % ) in the present study . there are acknowledged limitations to this study . this is a pilot study before a clinical trial , which limits the generalizability of the results . in addition , the present study was conducted in highly selected patients with a history of laparotomy and/or previously incomplete colonoscopy , possibly limiting the ability to generalize these results to other patient groups . we acknowledge that the polyp detection with cce has not been verified by follow - up colonoscopy , which could alter the results of the yield of colon polyps . despite these limitations , we believe that consideration of gastrografin as an alternative booster is of interest . in conclusion ,
background and study aims : sodium phosphate is a key component of bowel preparation regimen for colon capsule endoscopy ( cce ) , but may cause serious complications . 
 the aim of this study is to evaluate the use of gastrografin , substituted for sodium phosphate , in cce bowel preparation . 
 patients and methods : in total , 29 patients ( median age 64 years ; 23 females ) underwent cce , covered by the national health insurance system of japan . 
 all had a history of laparotomy and/or previously incomplete colonoscopy . on the day before examination 
 , patients ingested 1  l of polyethylene glycol  +  ascorbic acid with 0.5  l of water in the evening , and again the same laxative on the morning of examination . 
 after capsule ingestion , 50  ml of gastrografin diluted with 0.9  l of magnesium citrate was administered , and then repeated after 1 hour . 
 results : the capsule excretion rate was 97  % ( 28/29 ) . 
 the median colon transit time was 2 hours 45 minutes and rapid transit ( <  40 minutes ) through the colon occurred in one patient ( 3.4  % ) . 
 bowel cleansing level was adequate in 90  % of patients . 
 the polyp (   6  mm ) detection rate was 52  % . 
 diluted gastrografin was well tolerated by patients . 
 no adverse events occurred . 
 conclusion : gastrografin can be an alternative to sodium phosphate in cce bowel preparation regimen .