anatomists have observed that the length of the esophagus , i.e. the distance from the incisors to the esophagogastric junction , varies in different individuals from 32 to 50 cm . by endoscopy , the usual length of on adult essphagus is measured as 40 cm from the incisor to the point where mucosal change occurs , but the esophageal length varies from one person to another according to physical status . this variability is often experienced when trying to insert a ph meter , manometer or even nasogastric tube , or when placing the prosthesis for benign or malignant stenosis . we measured various lengths of esophagi in korean adults using a flexible fibercope and measured the external body intervals . then , we analyzed these data and extrapolated the various esophageal lengths with measurable external body intervals to obtain the correlations . the study was conducted for the measurement of esophageal length in 196 persons , 97 males and 99 females , with normal esophagogastric endoscopic findings . the distances from the upper incisors to 5 anatomical levels of esophagus ( cricopharyngeus narrowing , aortic narrowing , left main bronchus narrowing , hiatus and gastroesophageal junction ) were measured by an endoscope with 1 cm markings ( olympus co. q20 foreward view ) ( fig . 1 ) . each length was the mean value of double measurements during full inspiration and expiration respectively . the external body interval lengths studied were standing height , sitting height , the distance from the 7th vertebra to the coccyx and the distance from the upper incisors to the external occipital protuberance . the standing height and sitting height the distance from the 7th cervical vertebra to the coccyx was measured with a tape measure . a specially designed measure was used for the distance from the incisors to the external occipital protuberance ( fig . data analysis and correlation of esophageal lengths to external body intervals were done using spss / pc ( statistical package for social science / pc ) . observations have shown great variation in the length of the esophagus in adults but good correlation between esophageal lengths and external parameters . the measured lengths of external body intervals and various anatomical esophageal levels are depicted in table 1 . the mean standing - height and sitting - height of 196 persons studied were 160.808.64 cm and 86.605.91 cm , respectively . the interval from the upper incisors to each anatomical landmark of the esophagus ( cricopharyngeal narrowing , aortic arch compression , left main bronchus compression , hiatus , and esophagogastric junction ) were 15.70 cm , respectively . the true esophageal length , which is the distance from the cricopharyngeal narrowing to the esophagogastric junction , was 24.932.76 cm . the correlation of each esophageal anatomical level with external body intervals using the multiple stepwise reggression method is shown in table 2 . each of these 4 external variables was statistically significant , but better correlations were demonstrated by the h1 and h3 . although we employed the measurable distance ( h4 ) instead of the unmeasurable distance ( l1 ) , the equations using h4 and h2 did not express the esophageal lengths more accurately than the equation using h1 and h3 only . for example , the distance from the incisors to the esophagogastric junction ( l5 ) could be neatly expressed in simple equations as the following : 
 l5a=0.178  h1 + 0.176  h3 + 2.219  ( r2=0.58 ,  p<0.01)l5b=0.242  h1 + 2.076  ( r2=0.55 ,  p<0.01 )   likewise , all other esophageal lengths could be approximated with the equations using h1 and h3 or with the equation using h1 only . the development of improved capability in medical and surgical managment of esophageal disease processes has been significant . to understand and appropriately use current technologic advancements , the anatomic properties of the esophagus available information about esophageal length , however , has been based on cadaveric measurements , because it is not feasible to measure esophageal length in vivo . in adults , the distances from the incisor teeth to the esophagogastric junction have been described to be in the range of 3250 cm by various studies , and the described distance from the cricopharyngeus narrowing to the esophagogastric junction usually varies from 20 to 30 cm . on the other hand , jackson described esophageal lengths according to various age groups . but such wide ranges of esophageal values and different physical status even in the same age group hamper the application of these data to individual patients in esophageal procedures . the best approximation of esophageal length would be useful for various clinical procedures , such as placement of a ph meter , manometer and nasogastric tubes , insertion of an endoprosthesis and colonic interpostition for both benign and malignant stenotic segments . we conducted this study to determine the mean esophageal length of various anatomical levels and to derive a method approximating true esophageal lengths . the mean esophageal lengths from the upper incisors to the esophagogastric junction were 42.612.42 cm in men and 39.472.24 cm in women . these values are not smaller than western data despite the fact that koreans are shorter . this is possible because previous data were based on cadaveric examination and koreans have a different racial stature . we correlated several external body intervals with esophageal lengths by the multiple stepwise regression method : standing height , sitting height , the distance from the 7th cervical vertebra to the coccyx and the distance from the upper incisors to the occiput . all external parameters significantly correlated with the true esophageal lengths . based on our results , the distance from the upper incisors to the esophagogastric junction ( l5 ) can be best approximated by employing following equations : 
 l5=0.178  h1 + 0.176  h3 + 2.219  ( r2=0.58 ,  p<0.001)l5=0.242  h1 + 2.078  ( r2=0.55 ,  p<0.01 ) but accuracy determined by the other equations using more variables other than height did not increase remarkably despite their complexities . likewise , other anatomical levels of the esophagus can be predicted accurately as shown in the previous results . in conclusion , we consider that an accurate appraisal of the true length of an adult esophagus can be made by measuring the height and the other external measurable parameters .
previous data for esophageal lengths are based on age related groups or cadaveric examination , both of which are improper for application to various individualized procedures . because of the variability in height for any given age and longer length in vivo , lindividualized approximation is needed . 
 thus , we measured various anatomical levels of the esophagus using a flexible endoscope and correlated these data with measurable external body intervals.the mean esophageal length was 40.922.79 , which is longer than the length derived from cadaveric examinations . also , esophageal lengths which correlated better with height than any other body intervals , could be calculated from the following equation . esophageal length from the upper incisors to the esophagogastric junction ( l ) 
 can be expressed : l = 0.242  height ( ht ) + 2.078 cm ( p = 0.000 , r2 = 0525).the data from our study indicate that esophageal length can be reliably predicted using external body parameters before employing various procedures .