# Variation in Annual Volume at a University Hospital Does Not Predict Mortality for Pancreatic Resections

Authors: Rita A. Mukhtar; Omar M. Kattan; Hobart W. Harris
Journal: HPB Surgery
 (2008)

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## Abstract

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.


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## Body

## 1. Introduction

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 [1], the importance of the issue
increases. For pancreatic resections
specifically, many studies have found that higher annual volume predicts lower
mortality rates [1–10]. Such findings have led some
to advocate regionalization of pancreatic resections [3, 7–11]. Despite this call, however,
there have been practical limitations to such centralization [12]. In addition, the validity of
studies that typically rely on administrative databases for information has
been questioned [13]. 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 [14].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 [10]. 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.


## 2. Materials and Methods

### 2.1. Patient Selection

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 theInternational
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. Race/ethnicity was collected as recorded on
the patients’ records. The University of California, San Francisco Committee on
Human Research approved this study prior to the review of patient records.


### 2.2. Demographic and Clinical Characteristics

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 “other.”
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. All other findings
were categorized as “other.”


### 2.3. Outcomes

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). Less frequent complications were grouped
together as “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 was listed by number of resections performed. 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.


### 2.4. Statistical Analysis

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).


## 2.1. Patient Selection

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 theInternational
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. Race/ethnicity was collected as recorded on
the patients’ records. The University of California, San Francisco Committee on
Human Research approved this study prior to the review of patient records.


## 2.2. Demographic and Clinical Characteristics

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 “other.”
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. All other findings
were categorized as “other.”


## 2.3. Outcomes

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). Less frequent complications were grouped
together as “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 was listed by number of resections performed. 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.


## 2.4. Statistical Analysis

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).


## 3. Results

### 3.1. Patient Characteristics

Of the 511
patients who underwent pancreatic resections during the 16-year study period,
52% were females.The average age was58.6±14.7 years.
Most patients (61%) are
self-identified as White.


### 3.2. Procedures

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, 85%
were distal pancreatectomies.


### 3.3. Pathologic Diagnoses

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.


### 3.4. Comparison of Complication Rates for Head and Non-Head Pancreatic Resections

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 2–373 days with a
median of 11 days for pancreatic head resections, and 1–56 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%).


### 3.5. Effect of Annual Volume on Resection Outcome

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 1998–2002, 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-head pancreatic resections generally followed those of head
resections (Figure 1). 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).Table 1
High, medium, and low volume groups based
on either pancreatic head resection volume, or non-head resection volume.
Head resection volume groups*Number of head resections performedNon-head resection volume groupsNumber of non-head resections performedHigh volume yearsHigh volume years200242200028200038200222199833199920200131200119199928200416Medium volume yearsMedium volume years199723200514199519199114200317199410199314199510199413200311Low volume yearsLow volume years19961219969200411199282005819906199271993619915199761990519986*Each study year
was listed by number of resections performed.
The years were then divided by volume into three roughly equally sized
groups: high, medium, and low.Figure 1
Annual pancreatic
resection volume broken down by head resections and non-head resections. Trends in the volume of non-head pancreatic
resections generally followed those of head resections, with some exceptions.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
combinedfor 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 andlow/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  <  .05) (Table 2).Table 2
Postoperative complication and mortality
rates by low, medium, and high
volume years as defined by the number ofpancreatic head resections performed.*
Low volume years*Medium volume yearsHigh volume yearsNon-head resections (n  =  66)Head resections (n  =  49)Non-head resections (n  =  43)Head resections (n  =  86)Non-head resections (n  =  96)Head resections (n  =  172)Total (n  =  511)Death0 (0%)0 (0%)2 (4.7%)3 (3.5%)2 (2.1%)4 (2.3%)11 (2.2%)Wound infection1 (1.5%)4 (8.2%)2 (4.7%)16 (18.6%)6 (6.3%)17 (9.9%)46 (9%)Pancreatic fistula3 (4.5%)4 (8.2%)0 (0%)14 (16.3%)5 (5.2%)14 (8.2%)40 (7.8%)Gastroparesis1 (1.5%)5 (10.2%)1 (2.3%)10 (11.6%)1 (1%)16 (9.4%)34 (6.7%)Intraabdominal abscess3 (4.5%)6 (12.2%)3 (7%)16 (18.6%)5 (5.2%)20 (11.7%)53 (10.4%)Bile leak0 (0%)3 (6.1%)0 (0%)1 (1.2%)0 (0%)1 (0.6%)5 (1%)Pneumonia0 (0%)2 (4.1%)2 (4.7%)6 (7%)2 (2.1%)7 (4.1%)19 (3.7%)Urinary tract infection1 (1.5%)1 (2%)2 (4.7%)2 (2.3%)5 (5.2%)14 (8.2%)25 (4.9%)Postoperative bleeding2 (3%)1 (2%)0 (0%)4 (4.7%)1 (1%)4 (2.3%)12 (2.3%)Reoperation3 (4.5%)3 (6.1%)4 (9.3%)7 (8.1%)1 (1%)13 (7.6%)31 (6.1%)Other9 (13.6%)18 (36.7%)8 (18.6)30 (34.9%)14 (14.6%)65 (38%)144 (28.2%)*Each study year was listed by
number of resections performed. The
years were then divided by volume into three roughly equally sized groups:
high, medium, and low.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).Table 3
Postoperative complication and mortality rates by low, medium, and
low volume years as defined by the number ofnon-head resections performed.*
Low volume yearsMedium volume yearsHigh volume yearsNon-head resections (n  =  42)Head resections (n  =  93)Non-head resections (n  =  57)Head resections (n  =  64)Non-head resections (n  =  106)Head resections (n  =  149)Total (n  =  511)Death1 (2.1%)3 (3.2%)1 (1.8%)1 (1.6%)2 (1.9%)3 (2%)11 (2.2%)Wound infection2 (4.8%)14 (15.1%)1 (1.8%)10 (15.6%)6 (5.7%)13 (8.7%)46 (9%)Pancreatic fistula1 (2.4%)9 (9.7%)1 (1.8%)9 (14.1%)6 (5.7%)14 (9.4%)40 (7.8%)Gastroparesis1 (2.4%)6 (6.5%)1 (1.8%)9 (14.1%)1 (0.9%)16 (10.7%)34 (6.7%)Intraabdominal abscess1 (2.4%)14 (15.1%)4 (7%)10 (15.6%)6 (5.7%)18 (12.1%)53 (10.4%)Bile leak0 (0%)2 (2.2%)0 (0%)1 (1.6%)0 (0%)2 (1.3%)5 (1%)Pneumonia1 (2.4%)7 (7.5%)1 (1.8%)3 (4.7%)2 (1.9%)5 (3.4%)19 (3.7%)Urinary tract infection0 (0%)6 (6.5%)3 (5.3%)2 (3.1%)5 (4.7%)9 (6%)25 (4.9%)Postoperative bleeding0 (0%)6 (96.5%)1 (1.8%)0 (0%)2 (1.9%)3 (2%)12 (2.3%)Reoperation3 (7.1%)7 (97.5%)3 (5.3%)6 (9.4%)2 (1.9%)10 (6.7%)31 (6.1%)Other7 (16.7%)38 (40.9%)9 (15.8%)22 (34.4%)15 (14.2%)53 (35.6%)144 (28.2%)*Each study year was listed by
number of resections performed. The years
were then divided by volume into three roughly equally sized groups: high,
medium, and low.


## 3.1. Patient Characteristics

Of the 511
patients who underwent pancreatic resections during the 16-year study period,
52% were females.The average age was58.6±14.7 years.
Most patients (61%) are
self-identified as White.


## 3.2. Procedures

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, 85%
were distal pancreatectomies.


## 3.3. Pathologic Diagnoses

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.


## 3.4. Comparison of Complication Rates for Head and Non-Head Pancreatic Resections

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 2–373 days with a
median of 11 days for pancreatic head resections, and 1–56 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%).


## 3.5. Effect of Annual Volume on Resection Outcome

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 1998–2002, 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-head pancreatic resections generally followed those of head
resections (Figure 1). 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).Table 1
High, medium, and low volume groups based
on either pancreatic head resection volume, or non-head resection volume.
Head resection volume groups*Number of head resections performedNon-head resection volume groupsNumber of non-head resections performedHigh volume yearsHigh volume years200242200028200038200222199833199920200131200119199928200416Medium volume yearsMedium volume years199723200514199519199114200317199410199314199510199413200311Low volume yearsLow volume years19961219969200411199282005819906199271993619915199761990519986*Each study year
was listed by number of resections performed.
The years were then divided by volume into three roughly equally sized
groups: high, medium, and low.Figure 1
Annual pancreatic
resection volume broken down by head resections and non-head resections. Trends in the volume of non-head pancreatic
resections generally followed those of head resections, with some exceptions.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
combinedfor 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 andlow/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  <  .05) (Table 2).Table 2
Postoperative complication and mortality
rates by low, medium, and high
volume years as defined by the number ofpancreatic head resections performed.*
Low volume years*Medium volume yearsHigh volume yearsNon-head resections (n  =  66)Head resections (n  =  49)Non-head resections (n  =  43)Head resections (n  =  86)Non-head resections (n  =  96)Head resections (n  =  172)Total (n  =  511)Death0 (0%)0 (0%)2 (4.7%)3 (3.5%)2 (2.1%)4 (2.3%)11 (2.2%)Wound infection1 (1.5%)4 (8.2%)2 (4.7%)16 (18.6%)6 (6.3%)17 (9.9%)46 (9%)Pancreatic fistula3 (4.5%)4 (8.2%)0 (0%)14 (16.3%)5 (5.2%)14 (8.2%)40 (7.8%)Gastroparesis1 (1.5%)5 (10.2%)1 (2.3%)10 (11.6%)1 (1%)16 (9.4%)34 (6.7%)Intraabdominal abscess3 (4.5%)6 (12.2%)3 (7%)16 (18.6%)5 (5.2%)20 (11.7%)53 (10.4%)Bile leak0 (0%)3 (6.1%)0 (0%)1 (1.2%)0 (0%)1 (0.6%)5 (1%)Pneumonia0 (0%)2 (4.1%)2 (4.7%)6 (7%)2 (2.1%)7 (4.1%)19 (3.7%)Urinary tract infection1 (1.5%)1 (2%)2 (4.7%)2 (2.3%)5 (5.2%)14 (8.2%)25 (4.9%)Postoperative bleeding2 (3%)1 (2%)0 (0%)4 (4.7%)1 (1%)4 (2.3%)12 (2.3%)Reoperation3 (4.5%)3 (6.1%)4 (9.3%)7 (8.1%)1 (1%)13 (7.6%)31 (6.1%)Other9 (13.6%)18 (36.7%)8 (18.6)30 (34.9%)14 (14.6%)65 (38%)144 (28.2%)*Each study year was listed by
number of resections performed. The
years were then divided by volume into three roughly equally sized groups:
high, medium, and low.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).Table 3
Postoperative complication and mortality rates by low, medium, and
low volume years as defined by the number ofnon-head resections performed.*
Low volume yearsMedium volume yearsHigh volume yearsNon-head resections (n  =  42)Head resections (n  =  93)Non-head resections (n  =  57)Head resections (n  =  64)Non-head resections (n  =  106)Head resections (n  =  149)Total (n  =  511)Death1 (2.1%)3 (3.2%)1 (1.8%)1 (1.6%)2 (1.9%)3 (2%)11 (2.2%)Wound infection2 (4.8%)14 (15.1%)1 (1.8%)10 (15.6%)6 (5.7%)13 (8.7%)46 (9%)Pancreatic fistula1 (2.4%)9 (9.7%)1 (1.8%)9 (14.1%)6 (5.7%)14 (9.4%)40 (7.8%)Gastroparesis1 (2.4%)6 (6.5%)1 (1.8%)9 (14.1%)1 (0.9%)16 (10.7%)34 (6.7%)Intraabdominal abscess1 (2.4%)14 (15.1%)4 (7%)10 (15.6%)6 (5.7%)18 (12.1%)53 (10.4%)Bile leak0 (0%)2 (2.2%)0 (0%)1 (1.6%)0 (0%)2 (1.3%)5 (1%)Pneumonia1 (2.4%)7 (7.5%)1 (1.8%)3 (4.7%)2 (1.9%)5 (3.4%)19 (3.7%)Urinary tract infection0 (0%)6 (6.5%)3 (5.3%)2 (3.1%)5 (4.7%)9 (6%)25 (4.9%)Postoperative bleeding0 (0%)6 (96.5%)1 (1.8%)0 (0%)2 (1.9%)3 (2%)12 (2.3%)Reoperation3 (7.1%)7 (97.5%)3 (5.3%)6 (9.4%)2 (1.9%)10 (6.7%)31 (6.1%)Other7 (16.7%)38 (40.9%)9 (15.8%)22 (34.4%)15 (14.2%)53 (35.6%)144 (28.2%)*Each study year was listed by
number of resections performed. The years
were then divided by volume into three roughly equally sized groups: high,
medium, and low.


## 4. Discussion

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) [15], 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 [2–10]. 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 [3], and why it may be possible
to “export” good outcomes to low-volume hospitals [14]. 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 [17], the proportion of minorities treated at a
given hospital, surgeon volume [18], and even surgeon age [19] 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 [20]. Some have suggested that
differences in the quality of managing postoperative complications may account
for differences in-hospital outcomes [21]; 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 [10], and to be consistent with a
large study which showed a volume-outcome relationship for pancreatic head
resections [3], 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 [20]. In our series, 31.4% of patients had one or
more surgical complications following pancreatic head resection, consistent
with the reported overall morbidity of 30–55% [22]. 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 [25].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 [4]. The higher observed incidence of gastroparesis
may be due to the higher incidence of gastroparesis reported with malignancy
itself [26–29].Our
study has many important limitations. First, it was retrospective. 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 [17], that clinical studies are
less likely to find volume-outcome relationships than administrative studies [13], and that patient
characteristics at high and low volume hospitals differ significantly [9, 12], all pointsto 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. Further investigation is needed into what
elements make that possible.


## 5. Conclusions

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.



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