the desire to improve surgical 
 outcomes has resulted in significant interest in volume - outcome relationships . 
 as insurance companies continue developing policies that may use hospital 
 volume to influence patient choice of treatment center , the importance of the issue 
 increases . for pancreatic resections 
 specifically , many studies have found that higher annual volume predicts lower 
 mortality rates [ 110 ] . such findings have led some 
 to advocate regionalization of pancreatic resections [ 3 , 711 ] . despite this call in addition , the validity of 
 studies that typically rely on administrative databases for information has 
 been questioned . a recent study from our 
 institution suggested that the observed benefits at high - volume hospitals may 
 be  exported  to low - volume hospitals , suggesting that factors other than 
 volume alone may contribute to outcomes . few studies have 
 focused on the effects of annual fluctuations in hospital volume on outcome for pancreatic resections . additionally , most studies group different 
 types of pancreatic resections together instead of distinguishing between 
 pancreatic head resections and non - head resections . furthermore , many studies have examined the relationship 
 between annual volume and mortality but have not addressed whether volume affects postoperative 
 complication rates . we sought to 
 determine whether the reported volume - outcome relationships would be observed 
 over time at a single institution for both mortality and postoperative 
 complications , and whether those relationships would hold true for specific 
 types of pancreatic resections . we also 
 looked at trends in pancreatic resections performed at our institution over 16 
 years to determine which factors were associated with postoperative 
 complications . the paper and electronic 
 charts of 511 patients who underwent pancreatic resection at ucsf 's moffitt hospital 
 between january 1990 and 
 october 2005 were retrospectively reviewed . patients were identified through a computerized search for procedural 
 codes from the international 
 classification of diseases , 9th revision , clinical modification ( icd-9-cm ) corresponding to the following diagnoses : partial pancreatectomy , proximal 
 pancreatectomy , distal pancreatectomy , radical subtotal pancreatectomy , other 
 partial pancreatectomy , and pancreaticoduodenectomy ( pd ) . we excluded patients who were identified by 
 the computerized search but did not in fact undergo actual pancreatic resection 
 ( e.g. , those who had pancreaticojejunostomy , pancreatic debridement , or 
 pancreas transplant ) . we also excluded 
 patients who were younger than 16 years of age at the time of resection . the university of california , san francisco committee on 
 human research approved this study prior to the review of patient records . the following 
 data were recorded for each patient : age , gender , ethnicity , asa score , 
 indication for operation , operation type , pathologic diagnosis , postoperative 
 complications , length of stay , and in - hospital mortality . operation types 
 included pd , pylorus - preserving pd , distal pancreatectomy , spleen - sparing 
 distal pancreatectomy , subtotal pancreatectomy , total pancreatectomy , and total 
 pancreatectomy with islet autotransplantation . pathologic 
 diagnoses were grouped into pancreatic adenocarcinoma , periampullary tumor , 
 cystic tumor , neuroendocrine tumor , chronic pancreatitis , gastrointestinal 
 stromal tumor , metastatic tumors , or periampullary tumors included neoplasms of the common bile duct , ampulla 
 of vater , and duodenum . cystic tumors 
 included intraductal papillary mucinous tumors , mucinous cystadenoma , mucinous 
 cystadenocarcinoma , microcystic adenoma , serous cystadenoma , and solid and 
 papillary neoplasms . postoperative 
 complications were assessed by clinical diagnosis noted in the medical record , 
 and included wound infection , pancreatic fistula / leak , gastroparesis , bile 
 leak , reoperation , bleeding , pneumonia , and urinary tract infection ( uti ) . other ,  a category that included pleural effusion , pulmonary 
 edema , pulmonary embolus , arrhythmia , myocardial infarction , wound dehiscence , clostridium difficile colitis , acute 
 renal failure , incisional hernia , and bacteremia . to evaluate the effect of annual volume on outcomes , each study year to maximize differences between the low 
 volume and high volume groups , the years were then divided by volume into three 
 roughly equally sized groups : high , medium , and low . to further 
 determine whether the volume of a specific type of pancreatic resection could 
 predict outcomes , years were categorized in two ways : based on volume of pancreatic head resections 
 performed , and by the volume of non - head resections performed . we used multiple logistic 
 regression to examine all relationships between annual volume and outcome , 
 adjusting for patient gender , presence of underlying malignancy on pathological 
 diagnosis , race ( white or nonwhite ) , and age . additionally , t - tests and chi - square tests were used where appropriate , 
 with statistical significance set at p < .05 . data are presented as mean  standard deviation ( sd ) unless otherwise 
 indicated . data were analyzed using statistical analysis software ( sas ) ( cary , nc , usa ) and stata ( college station , tex , usa ) . of the 511 
 patients who underwent pancreatic resections during the 16-year study period , 
 52% were females.the average age was 58.6  14.7 years . the 
 majority ( 60% ) of resections performed were pancreatic head resections ( pd ) ; 
 non - head resections ( 40% ) comprised distal , subtotal , or total 
 pancreatectomies . among the pancreatic 
 head resections , more than ( 60% ) were pylorus - preserving pd as opposed 
 to classical pd . among the non - head resections , the most common pathologic diagnosis was 
 adenocarcinoma of the pancreas ( 25% ) , followed by periampullary tumors 
 and cystic tumors . three of the 33 patients with a preoperative diagnosis of 
 chronic pancreatitis had final pathologic results that indicated malignancy . conversely , 15 ( 24% ) of the 62 patients with a final diagnosis of chronic 
 pancreatitis were erroneously believed to have a malignancy 
 preoperatively . rates of wound 
 infections , intraabdominal abscesses , pancreatic fistulas , gastroparesis , 
 reoperations , and  other  complications were significantly higher in patients 
 who underwent pancreatic head resections than in those who underwent non - head 
 resections . not surprisingly , patients who underwent pancreatic head 
 resections also had significantly longer hospital stays ( mean of 14.9 
 days versus 10.7 days ) . length of stay 
 ranged from 2373 days with a 
 median of 11 days for pancreatic head resections , and 156 days with a 
 median of 8 days for non - head resections . 
 additionally , slightly more surgical complications occurred in patients 
 with an underlying malignancy ( 34.4% ) than in patients with benign disease 
 ( 25.3% ) . an average of 32  17 pancreatic resections were done annually during the 
 years included in this study . a higher 
 than average number of resections ( n = 262 ) was performed between 19982002 , but the numbers 
 declined beginning in 2003 , possibly related to the departure of one particular 
 surgeon . with some exceptions , trends in 
 the volume of non - however , because 
 the volume of head resections did not necessarily increase or decrease 
 concordantly with the volume of non - head resections , we first used the rates of 
 pancreatic head resections to define 
 high , medium , and low volume years , and then used the rates of non - head resections to do so ( table 1 ) . we found that among patients who 
 underwent any pancreatic resection in low volume years as defined by number of head resections performed , 
 there were no in - hospital deaths . when 
 medium and low volume years were 
 combined for purposes of 
 statistical analysis , there was no difference in death rates for either 
 pancreatic head resections ( odds ratio = 1.62 , p = .64 ) or non - head 
 resections ( odds ratio = 1.09 , p = .9 ) between high volume years and low / medium volume years . in 
 addition , there were no significant differences in postoperative complication 
 rates among patients undergoing non - head resection in high versus low volume 
 years . the incidence of gastroparesis 
 ( odds ratio = 0.57 , p = .7 ) and bleeding ( odds ratio = 0.344 , p = .398 ) was lower in high volume years , but not significantly so , and the 
 incidence of utis was higher , but again , not significantly so 
 ( odds ratio = 4.26 , pq = 0.199 ) ( table 2 ) . the only 
 difference was that there were significantly fewer bile leaks in patients who 
 underwent pancreatic head resection in a high - volume head resection year ( odds 
 ratio = 0.09 , p < when the rates of pancreatic non - head 
 resections were used to define high , medium , and low volume years , there was no 
 significant difference in death rates for either pancreatic head resections 
 ( odds ratio = 1.13 , p = .923 ) or non - head resections ( odds ratio = 
 0.652 , p = .611 ) performed in high volume years versus low volume 
 years . the same was true for 
 complication rates ( odds ratios = 0.734 for non - head resections , and 0.798 for 
 head resections ) . although for patients 
 undergoing non - head resections , the incidence of gastroparesis in high volume 
 years was lower , the difference was not significant ( odds ratio = 0.338 , p = .453 ) , nor was the higher incidence of intraabdominal abscesses ( odds ratio = 
 1.92 , p = .554 ) . similarly , 
 patients undergoing head resections had fewer wound infections , bile leaks , 
 cases of pneumonia , and less bleeding in high volume years , but again , the 
 differences were not significant ( table 3 ) . our 
 findings show that at a single institution variation in annual pancreatic 
 resection volume does not affect mortality . in fact , there were no in - hospital deaths following pancreatic head 
 resection during the six low volume years included in the study . although our 
 hospital 's volumes may be considered high by some criteria , during four of the 
 six low volume years , we did not meet the leapfrog consortium 's cutoff for 
 being an index center ( 11 pancreatic head resections per year ) , suggesting that our low 
 volume group is truly reflective of low volumes based on nationally accepted 
 standards . the results presented here 
 are discordant with the previously demonstrated inverse relationship between 
 pancreatic resection volume and mortality [ 210 ] . in fact , the findings seem to suggest that  once a high - volume hospital , 
 always a high - volume hospital ,  even if fluctuations in volume actually give 
 that hospital low - volume status for a given period of time . if this is the case , there must be some 
 factor that affords the hospital the ability to maintain excellent mortality 
 rates independent of volume . the 
 existence of such a factor supports the notion that the systems in place 
 at a particular institution [ 4 , 16 ] may be the effectors of 
 outcome , and suggests that a higher volume may be a proxy for the presence of 
 these systems . this may explain why some 
 low - volume hospitals have been able to achieve low mortality rates , and why it may be possible 
 to  export  good outcomes to low - volume hospitals . many 
 studies support the idea that volume is only one part of a complex system of 
 factors that affect outcomes , with findings such as race , the proportion of minorities treated at a 
 given hospital , surgeon volume , and even surgeon age   playing roles in surgical mortality . an advantage of the grouping method used in 
 our study is that each group contains a diverse range of years ( e.g. , the low volume 
 group contains years 1990 and 2005 ) , possibly reducing the contribution from 
 any one surgeon . although some 
 trends toward fewer complications in high volume years were observed , only the 
 incidence of bile leaks following pancreatic head resection was significantly 
 lower in the high volume years . we have 
 not seen this specific finding in published reports , but a recent study did 
 show decreased complication rates following pancreatic resection as volume 
 increased in an already high - volume hospital . some have suggested that 
 differences in the quality of managing postoperative complications may account 
 for differences in - hospital outcomes ; however , in the prior study , 
 and the one reported here , 
 mortality rates remained unchanged despite changing trends in complication 
 rates . additionally , during the period 
 of time included in the study , there was no system - wide initiation of a 
 preoperative or postoperative pathway for patients undergoing pancreatic 
 resection . it is possible 
 that although we had high and low volume years , we failed to find a difference 
 in mortality rates because we divided pancreatic resections into head and 
 non - head resections when creating our volume groups . had we instead used all pancreatic resections 
 to define the groups , our low volume years may have exceeded the volume 
 designated as  low  in other studies . however , because many studies have grouped different types of pancreatic 
 resections together , and to be consistent with a 
 large study which showed a volume - outcome relationship for pancreatic head 
 resections , we chose to split them up in 
 order to see whether there was any specific predictive value for a given 
 resection type . additionally , we still 
 had a clear difference in the average number of resections performed in high 
 versus low volume years . in 
 our analysis of other factors that may contribute to morbidity and mortality , 
 our results were mostly consistent with previously reported data , with patients 
 undergoing pancreatic head resection experiencing more complications than those 
 undergoing non - head resection . in our series , 31.4% of patients had one or 
 more surgical complications following pancreatic head resection , consistent 
 with the reported overall morbidity of 3055% . in our study , the incidence of pancreatic 
 fistula after pancreatic head resection was 10.5% and consistent with prior 
 reports [ 23 , 24 ] , while the incidence 
 following other pancreatic resections was 3.9% . our findings suggest that the creation of the pancreatic anastomosis 
 carries a higher risk of pancreatic leak than transection of the pancreas . interestingly , others have reported a higher 
 incidence of pancreatic fistulas with left - sided pancreatic resections . for 
 patients with malignant disease , the overall surgical complication rate was 
 34.4% compared to 25.3% for patients with benign disease . although patients with 
 malignant disease tended to have more complications , only the incidence of 
 gastroparesis came close to differing significantly . this is fairly consistent with other studies 
 which have shown no differences in surgical complications between these two 
 patient groups . the higher observed incidence of gastroparesis 
 may be due to the higher incidence of gastroparesis reported with malignancy 
 itself [ 2629 ] . . a prospective study would have allowed 
 more accurate assessment of postoperative complications , since we had relied on physician 
 diagnosis and notation of complications in the medical record . as such , definitions of particular diagnoses 
 were likely inconsistent across physicians and the time course of the study . additionally , review of inpatient charts indicated in - hospital mortality , but 
 we were not able to accurately assess deaths that may have occurred after 
 discharge , limiting the inclusion of potential deaths due to late 
 complications . moreover , although we 
 included over 500 patients in this study , the study is still limited to a 
 single hospital 's experience . clearly , 
 many studies have observed lower mortality rates for pancreatic resections performed at high - volume hospitals . understanding the precise mechanism behind 
 this association may allow us to improve outcomes for patients facing diseases 
 that require pancreatic resection . the 
 fact that this relationship is not borne out at a single hospital that had fluctuations in volume over 
 time , that race has been shown to affect outcome for some procedures irrespective 
 of hospital volume , that clinical studies are 
 less likely to find volume - outcome relationships than administrative studies , and that patient 
 characteristics at high and low volume hospitals differ significantly [ 9 , 12 ] , all points to a much more complex explanation than volume alone . of course , these data give no insight into 
 how hospitals acquire the ability to provide good outcomes after pancreatic 
 resections . surgical volume may indeed 
 play a role ; however , annual volume alone does not appear to be an adequate 
 predictor of postoperative mortality at our institution . even if the answer were simply volume , we saw that implementing 
 regionalization faces considerable obstacles [ 10 , 12 ] . the goal then is to determine how to improve 
 outcomes for patients who will continue to be treated at low - volume hospitals . our findings suggest that excellent outcomes 
 for pancreatic resections are possible despite changes in volume . annual 
 volume of pancreatic resections does not predict postoperative mortality at a 
 major academic medical center . with the 
 exception of a lower incidence of bile leaks following pancreatic head 
 resections performed in high volume years , there are no differences in 
 postoperative complications following pancreatic resections in high versus low 
 volume years . these findings contradict 
 previously published studies and suggest the need for further investigation 
 into the predictors of outcomes following pancreatic resections .
annual volume of pancreatic resections has been shown to affect mortality rates , prompting recommendations to regionalize these procedures to high - volume hospitals . 
 implementation has been difficult , given the paucity of high - volume centers and the logistical hardships facing patients . 
 some studies have shown that low - volume hospitals achieve good outcomes as well , suggesting that other factors are involved . 
 we sought to determine whether variations in annual volume affected patient outcomes in 511 patients who underwent pancreatic resections at the university of california , san francisco between 1990 and 2005 . 
 we compared postoperative mortality and complication rates between low , medium , or high volume years , designated by the number of resections performed , adjusting for patient characteristics . 
 postoperative mortality rates did not differ between high volume years and medium / low volume years . as annual hospital volume of pancreatic resections may not predict outcome , identification of actual predictive factors may allow low - volume centers to achieve excellent outcomes .