lynch syndrome ( ls ) , formerly referred to as hereditary nonpolyposis colorectal cancer ( hnpcc ) accounts for 2    4  % of all colorectal cancers ( crcs ) 1 .
affected family members have a germline mutation in one of the dna mismatch repair genes mlh1 , pms2 , msh2 , or msh6 , and a lifetime risk for development of crc of 25   
centralized organizations of surveillance for lynch syndrome families have been established in finland , netherlands , germany , and canada , and follow - up results have been published since 1995 , with essential information on the efficiency of prevention of crc incidence and mortality 3 
 4 
 5 
 6 .
colonoscopy has been shown to decrease both by 63  % 7 
 8 . in spite of colonoscopic surveillance , interval cancers ( defined as crc found within 2 years after a negative colonoscopy or leaving a colon  clear  of polyps )
these 29 cases , with a median age of 52 years , and a median time since previous colonoscopy of 17 months to the diagnosis of interval cancer , were mlh1 and msh2 mutation carriers . of these , 39  % had previous crc , and those who had never undergone colonic resection developed proximal lesions in 84  % of cases ; 77  % were stage t1    3 , n0m0 .  in 9  % , an incomplete previous colonoscopy was reported , and the tumor was located in the unexamined colon . in six cases ,
the authors concluded that mlh1 and msh2 mutation carriers , previous crc , incomplete colonoscopy , and incomplete polypectomy were risk factors for diagnosis of interval cancer in ls 9 .
several factors may predict failure to prevent interval cancer in ls : more lesions in the right colon ; more flat (  nonpolypoid  ) and lateral growing polyps ; small adenomas may already harbor high grade dysplasia or a high percentage of villous components and become advanced adenomas .
overall , there is an acceleration of the adenoma    carcinoma sequence , synchronous lesions have a high prevalence and , importantly , patients with ls are younger and less tolerant to colonoscopy ( need more sedation ) ; and repeated colonoscopies are needed for lifelong surveillance ( patient experience is important for compliance ) 12 .
thus , a very meticulous and precise procedure is required with removal of all of the polyps .
nonpolypoid lesions , defined as a lesion with height less than half the diameter , is a characteristic of ls 13 .
studied 59 ls patients in comparison with 590 controls , and found that 43.3  % and 58.1  % of adenomas and serrated adenomas were nonpolypoid , in comparison with 16.9  % and 20.4  % in controls , respectively ( p  <  0.001 ) 13 .
regular colonoscopy should be performed repeatedly and at short intervals when ls is suspected according to amsterdam ii criteria , or when a mutation in one of the dna mismatch repair genes ( mmr ) is found .
the procedure should be performed in an endoscopic unit experienced with ls , to minimize the potential for missing polyps and thus exposing patients to interval cancer .
four endoscopic methods have been tested in order to improve the diagnostic yield of colonoscopy and the polyp / adenoma detection rate : high resolution white light endoscopy ( hr ) , chromoendoscopy , narrow band imaging ( nbi ) and autofluorescence endoscopy ( afe ) ( table  1 ) .
four prospective trials have compared chromoendoscopy to hr and nbi in  back - to - back  studies 14 
 15 
 16 
 17 .
lecomte et al . examined 33 patients with ls and found an additional 45 lesions ( 11 adenomas ) with chromoendoscopy performed after hr colonoscopy 14 .
similar findings have been described by hurlstone and colleagues who found an additional 52 lesions ( 32 adenomas ) in 25 patients 15 .
huneburg et al . performed colonoscopy in 109 patients in two investigational arms : chromoendoscopy was found to be better than hr colonoscopy in 47 patients , with 1.5 and 0.5 lesions per patient , respectively ( p  <  0.01 ) , and also better than nbi , with 1.8 and 0.7 lesions per patient , respectively ( p  =  0.032 ) . comparing nbi with hr colonoscopy in 62 patients with ls according to amsterdam ii criteria , nbi added 21 polyps ( 6 flat adenomas ) ( p  <  0.001 ) 17 .
chromo , chromoendoscopy ; hrc , high resolution colonoscopy ; wle , white light endoscopy ; nbi , narrow band imaging ; hdwl , high definition white light endoscopy ; afe , autofluorescence endoscopy . the first method listed is the better method .
the method of  back - to - back  endoscopy has a methodological bias , since additional lesions can be found in the second procedure .
stoffel et al . performed conventional colonoscopy in 54 patients with ls ( 46 with mmr gene mutation ) 18 .
then patients were randomized into one of two arms : chromoendoscopy or  intensive  inspection .
chromoendoscopy detected more polyps than  intensive  inspection ( p  =  0.04 ) , but adenoma detection was not significantly different ( p  =  0.27 ) .
however , the second colonoscopy ( chromoendoscopy or  intensive  ) doubled the diagnostic yield for adenoma .
the only procedure that demonstrated a higher diagnostic yield for adenoma than hd colonoscopy , without the methodological bias of back - to - back colonoscopy , was autofluorescence endoscopy ( afe ) 19 , but this observation has not yet been confirmed in other studies .
seventy - five ls or familial crc patients were examined with either white light colonoscopy ( wle ) followed by afe , or with afe followed by wle , by two blinded endoscopists .
all lesions were removed on the 2nd endoscopy ( or the 3  rd if missed ) .
white light endoscopy identified 65 adenomas in 28  /41 patients with adenomas , less than afe which identified 87 adenomas in 37/41 patients , an increase of 32  % .
sensitivities of afe and wle were 92  % and 68  % , respectively ( p  =  0.001 ) .
the adenomas additionally detected with afe were smaller than those detected with wle , with means of 3  mm versus 4.9  mm , respectively ( p  <  0.01 ) .
quality indicators for colonoscopy are constantly published and are all directed towards complete examination and removal of all polyps .
a correlation is suspected between the incidence of interval cancer and the quality of colonoscopy in screening average - risk as well as high risk populations 20 . validated quality indicators are even more important to follow in ls , since the adenoma   
fifty - four patients with a known pathogenic mutation in mlh1 or msh2 underwent colonoscopy every 1    2 years , with a mean follow - up period of 9.3 years .
the polyp dwell time was 35.2    22.3 months , and shorter for the right than the left colon , 28.7 vs. 43.6 months , respectively .
thus , a withdrawal time of more than 6 minutes , an excellent preparation , complete examination ( photographic evidence showing the ileocecal valve and appendix orifice ) , u - turn in the rectum , adequate adenoma detection rate ( adr ) and polyp detection rate ( pdr ) , and complete polypectomy by experienced endoscopists are cornerstones for surveillance endoscopy in ls .
guidelines recommend colonoscopy every 1    2 years , starting at age 20    25 years , or 10 years younger than the age of first diagnosis in the family ( whichever is first ) , and yearly after the age of 40 years 4 
 22 
 23 
 24 
 25 
 26 . in four us cancer genetics clinics , 181 patients with ls ( according to amsterdam criteria or with a proven mutation ) were screened . only 132 ( 73  % )
had appropriate surveillance according to the guidelines 27 . personal history ( or 2.81 ) , first degree relative with crc ( or 2.61 ) , and genetic evaluation ( or 4.62 ) were associated with appropriate surveillance .
stuckless and co - investigators looked at the impact of colonoscopic screening in male and female ls carriers with the msh2 mutation 28 .
they compared 54 male and 98 female ls mutation carriers who had been surveyed ( screened carriers ) with 94 male and 76 female carriers ( unscreened carriers ) . in men ,
the median age to develop crc was 58 years versus 47 years in screened and unscreened patients , respectively ( p  <  0.0001 ) , and the median survival was 66 years versus 62 years , respectively ( p  =  0.034 ) . in women ,
the median age to develop crc was 79 years versus 57 years in screened and unscreened patients , respectively ( p  <  0.0001 ) , and the median survival was 80 years versus 63 years , respectively ( p  =  0.001 ) . twenty percent of men and 7  % of women developed crc within 2 years of previous colonoscopy .
crc development may be further reduced by decreasing the screening interval to 1 year and improving the quality of colonoscopy  .
the risk factors for adenoma or cancer in ls patients , on top of genetic propensity , are male gender , mlh1 and msh2 mutations , cigarette smoking , not participating in colonoscopic surveillance , previous crc , incomplete colonoscopy , and residual adenomatous tissue after polypectomy 7 
 8 
 29 
 30 
 31 
 32 .
in ls patients and individuals fulfilling the amsterdam ii criteria , surveillance colonoscopy should be performed using modern high resolution technology by experienced endoscopists every 1    2 years , starting at age 20   
25 years , or 10 years younger than the age of first diagnosis in the family ( whichever is first ) , and annually after the age of 40 years .
colonoscopy in ls patients should include meticulous inspection and precise removal of all polyps , with special attention to the right colon and alertness to flat lesions . at the moment
, none of the new endoscopic techniques have shown convincing superiority over high resolution white light colonoscopy in ls patients .
 lynch syndrome ( ls ) accounts for 2    4  % of all colorectal cancers . 
 affected family members have a germline mutation in one of the dna mismatch repair genes mlh1 , pms2 , msh2 , or msh6 , and a lifetime risk for development of colorectal cancer of 25  
   75  % . 
 current guidelines recommend annual to biannual surveillance colonoscopy in mutation carriers . 
 several factors may predict failure to prevent interval cancer in ls : more lesions in the right colon ; more flat (  non polypoid  ) and lateral growing polyps ; small adenomas may already harbor high grade dysplasia or a high percentage of villous component and become advanced adenomas ; there is a short duration of the adenoma    carcinoma sequence ; 
 synchronous lesions have high prevalence ; patients are younger and less tolerant to colonoscopy ( need more sedation ) ; and repeated colonoscopies are needed for lifelong surveillance ( patient experience is important for compliance ) . in order to prevent cancer in ls patients , surveillance colonoscopy should be performed in an endoscopic unit experienced with ls , every 1    2 years , starting at age 20    
 25 years , or 10 years younger than the age of first diagnosis in the family ( whichever is first ) , and yearly after the age of 40 years . 
 colonoscopy in ls patients should be a very meticulous and precise procedure ( i.  e. taking sufficient withdrawal time , documentation of such warranted ) , with removal of all of the polyps , special attention to the right colon and alertness to flat lesions . 
 following quality indicators such as successful cleansing of the colon and removal of every polyp will probably improve prevention of interval cancers . at this moment 
 , none of the new endoscopic techniques have shown convincing superiority over conventional high resolution white light colonoscopy . 
Introduction
When, where, and how to perform colonoscopy in Lynch syndrome patients
Quality indicators for colonoscopy
How often to perform colonoscopy in Lynch syndrome
Conclusion