CT-Guided Percutaneous Catheter Drainage of Acute Infectious Necrotizing Pancreatitis: Assessment of Effectiveness and Safety

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1 Vascular and Interventional Radiology Original Research Baudin et al. CT-Guided Drainage of Acute Necrotizing Pancreatitis Vascular and Interventional Radiology Original Research Guillaume Baudin 1 Madleen Chassang 1 Eve Gelsi 2 Sébastien Novellas 1 Gilles Bernardin 3 Xavier Hébuterne 2 Patrick Chevallier 1 Baudin G, Chassang M, Gelsi E, et al. Keywords: pancreatic necrosis, pancreatitis, percutaneous catheter drainage DOI: /AJR Received April 6, 2011; accepted after revision December 16, Department of Radiology, University Hospital of Nice, 151 Rte de Saint-Antoine de Ginestière, Nice, Alpes Maritimes 06200, France. Address correspondence to G. Baudin (baudin.g@chu-nice.fr). 2 Department of Hepatogastroenterology and Clinical Nutrition, University Hospital of Nice, Nice, France. 3 Department of Medical ICU, University Hospital of Nice, Nice, France. AJR 2012; 199: X/12/ American Roentgen Ray Society CT-Guided Percutaneous Catheter Drainage of Acute Infectious Necrotizing Pancreatitis: Assessment of Effectiveness and Safety OBJECTIVE. The purpose of this study is to assess retrospectively the effectiveness and safety of CT-guided percutaneous drainage and to determine the factors influencing clinical success and mortality in patients with infectious necrotizing pancreatitis. MATERIALS AND METHODS. From April 1997 to December 2005, 48 consecutive patients (33 men and 15 women; median age, 58.5 years) with proven infectious necrotizing pancreatitis underwent percutaneous catheter drainage via CT guidance. Evaluated factors included clinical, biologic, and radiologic scores; drainage and catheter characteristics; and complications. Clinical success was defined as control of sepsis without requirement for surgery. Univariate analysis was performed to determine factors that could have affected the clinical success and the mortality rates. RESULTS. Clinical success was achieved in 31 of 48 patients (64.6%) and was significantly associated with Ranson score (p = 0.01) and with the delay between admission and the beginning of the drainage (p = 0.005), with a calculated threshold delay of 18 days (p = 0.001). The global mortality rate (14/48 [29%]) was also influenced by the Ranson score (p = 01) and the delay of drainage (p = 0.04) with the same threshold delay (p = 0.01). Only two major nonlethal procedure-related complications were observed. CONCLUSION. Percutaneous catheter drainage is a safe and effective technique to treat acute infectious necrotizing pancreatitis. A cute pancreatitis (AP) presents with a wide range of clinical findings, clinical severity, and morphologic manifestations. Among all possible complications, infectious pancreatic necrosis (IPN) is, by far, the most dreaded and the most severe, causing 80% of the deaths associated with AP [1]. Necrosis is defined as diffuse or focal areas of nonviable pancreatic parenchyma that typically are associated with peripancreatic fat necrosis [2]. It occurs in about 20% of patients with AP, and diagnosis is made by contrastenhanced CT using the International Symposium on Acute Pancreatitis criteria [2, 3]. Bacteriologic infection can occur in 40 60% of the cases, resulting in high morbidity and mortality rates [3 5]. The risk of infection increases with the duration of the disease, reaching a peak during the third week with an incidence rate of 71% [5]. Clinical, biologic, and radiologic signs are not specific enough to reveal infection of the necrosis [6]. Only fineneedle aspiration performed under radiologic guidance can provide bacteriologic confirmation of infection with both high sensitivity and specificity [7]. It is generally accepted that, in IPN, the infected nonvital solid tissue has to be removed to control the sepsis [8]. Surgical necrosectomy has been the preferred treatment of years, with very variable mortality rates ranging from 3% to 42% [8, 9]. Since the early 1980s, several teams have been working on alternative nonsurgical techniques, such as percutaneous catheter drainage (PCD), inspired by the promising results of PCD in the treatment of the other complications routinely associated with AP, such as acute fluid collections, pancreatic abscesses, and pancreatic pseudocysts [10, 11]. The use of PCD in patients with IPN has already been reported as an alternative to surgical treatment by surveys in the literature during the past 25 years, with a varying and wide range of clinical success and mortality rates [12]. The purpose of our study was to assess retrospectively the effectiveness and safety of PCD 192 AJR:199, July 2012

2 CT-Guided Drainage of Acute Necrotizing Pancreatitis of exclusive proven IPN in a homogeneous population and to determine the factors influencing clinical success and mortality. Materials and Methods Patients We received ethical review board approval for our retrospective study, and informed consent was waived. By query of the hospital and the radiology division s database from April 1997 to December 2005, we retrospectively identified 48 consecutive patients (33 men and 15 women; median age, 58.5 years; age range, years) of the total of 1186 patients admitted with a diagnosis of AP in our center during the same period, who underwent CTguided PCD of IPN. In our center, patients considered for acute IPN systematically benefit from PCD in first intent. The cause of the pancreatitis was a biliary tract disease in 17 patients, alcoholism in 15, ERCP in six, postsurgical complications in three, hypertriglyceridemia in one, and pancreas divisum in one. Four cases were idiopathic, and one remained undocumented. Inclusion Criteria Patients had to meet all three of the following criteria: first, have proven AP with acute abdominal pain and an increase in serum amylase level within the first 48 hours, using a threshold of 3 or 4 times the upper limit of the normal, as recommended by the French symposium on AP [13]; second, show evidence of pancreatic necrosis on the contrast-enhanced CT performed between the 48th and 72nd hours after the onset of symptoms, as recommended by the French consensus conference [13]; and third, have an infection of the necrosis suspected by clinical, biologic, and radiologic signs and proven by using CT-guided percutaneous aspiration with gram-positive stain or culture. Necrosis was defined as presence of focal or diffuse wellmarginated zones of unenhanced pancreatic parenchyma with contrast density less than 50 HU, larger than 3 cm in maximum diameter, or greater than 30% of the area of the pancreas [14]. We excluded patients with infected acute fluid collections, pancreatic abscesses, and infected pseudocysts, according to the definitions provided by the International Symposium on Acute Pancreatitis [2, 14]. TABLE 1: Distribution of Current Study Population According to International Symposium on Acute Pancreatitis Definition of Severe Acute Pancreatitis Definition Patient Distribution Predictive scores Ranson score (31/40) APACHE II score (21/24) Organ failure 73 (35/48) Shock (systolic blood pressure < 90 mm Hg), no. of patients 25 Pulmonary insufficiency (Pao 2 60 mm Hg), no. of patients 23 Renal failure (creatinine level > 170 mmol/l after rehydration), no. of patients 26 Gastrointestinal bleeding (> 500 ml/24 h), no. of patients 1 Presence of a local complication Necrosis 100 (48/48) Abscess 0 Pseudocyst 0 Note Except where noted otherwise, data are percentage of patients (no./total). The International Symposium on Acute Pancreatitis s definition of acute pancreatitis has been published elsewhere [2]. APACHE = acute physiology, age, and chronic health evaluation. Medical, Biologic, and Radiologic Review We recorded the following data for each patient: age, sex, length of hospital stay, number of days spent in ICU, cause of the AP, and occurrence of the general complications that were defined as severe according to the definition of organ failure of the International Symposium on Acute Pancreatitis [2] (Table 1). Clinical and biologic data were also recorded to calculate predictive scores, including Ranson and acute physiology, age, and chronic health evaluation (APACHE) II score; missing data did not constitute an exclusion criterion in our study [15, 16]. Kinetics of the C-reactive protein (CRP) values were recorded as milligrams per liter at entrance, mid treatment, end of PCD, and at discharge. All patients underwent CT imaging between the 48th and the 72nd hour after the onset of symptoms to assess the presence of the necrosis (graded as < 30%, 30 50%, and > 50%) and to evaluate the numbers and the localization of the necrotic collections. CT severity index scores and scores according to Balthazar et al. [17] were recorded for each of the 48 patients by reviewing the radiologic reports and images. Review was performed in consensus by three radiologists with 4, 8, and 15 years of experience, respectively, specialized in abdominal imaging. From 1997 to 2004, CT scans were performed on a Tomoscan AV (Philips Healthcare). After 2004, they were obtained with a LightSpeed VCT (8- or 64-MDCT, GE Healthcare). Unenhanced scanning was first performed focused on the pancreatic bed. Then contrast-enhanced slices were performed seconds after IV injection of 2 ml/kg of iobitridol (Xenetix 300, Guerbet) using a power injector at a rate of 2 4 ml/s. Drainage Indication, Procedure, Catheter Management, and Complications Drainage indication The therapeutic algorithm (Fig. 1) was strictly the same during the 9 years of the study. In suspected cases of infected necrosis (i.e., persistent fever, medically uncontrolled multiorgan failure, and increased WBC or CRP level), patients underwent a contrast-enhanced CT scan to exclude any other cause of instability or infection and so that fine-needle aspiration of all the necrotic collections could be performed using an 18-gauge needle under CT guidance. In cases of the presence of purulent material on fluid inspection or for positive bacteriologic studies, PCD was performed. If the sample was negative, PCD was precluded, and in cases of persistent signs of infection, another needle aspiration was performed within 7 days. Appropriate IV broad-spectrum antibiotics were subsequently administered to each patient. Drainage procedure Initial PCD was performed under CT guidance, in strict sterile conditions, using local anesthesia, light sedation, or general anesthesia if assisted ventilation was needed. The patient s position on the interventional CT table was adjusted to the region of interest. All procedures were performed by trained interventional radiologists assisted by fellows. The Seldinger technique was systematically used, sequentially dilating the tract over a inch J-shaped stiff hydrophilic guidewire (RF*OA351d53M, Terumo), to place a catheter in each of the necrotic collections via the most direct transperitoneal route, avoiding intervening bowels and solid organs. One or more multiperforated double-sump 12- to 16-French catheters (RMSU ACL, Cook Medical) were placed to aspirate the cavity fluid and to start a continuous irrigation with 1 L/drain/day of normal saline. Twenty-four to 72 hours after the initial catheter placement, the patients came back into our interventional radiology suite, to benefit from opacification of the necrotic cavity through the radiologic drain using an injection of ioxithalamate meglumine (Te- AJR:199, July

3 Baudin et al. Identify and localize necrotic collections Purulent material Acute pancreatitis Enhanced CT scan (48th h) Surveillance Clinical and/or biologic suspicion of infection Contrast-enhanced CT scan Fine-needle aspiration Bacteriologic study PCD Positive Necrosis extent (CT severity index) Nonpurulent material Negative Fig. 1 Flowchart shows schematic representation of approach that was used in patients with suspected infectious pancreatic necrosis. PCD = percutaneous catheter drainage. lebrix 30 Meglumine, Guerbet) diluted by half. The initial catheter was removed over a guidewire, and a new larger catheter was inserted after sequential dilation under fluoroscopic guidance (Multidiagnost 3, Philips Healthcare) and light sedation. The goal was to increase the diameter of the catheter to a maximum of French using double-sump large-bore catheters whose distal holes were expanded manually (Sherwood, Argyle). This allows an easier evacuation of the necrotic debris, thus providing a percutaneous necrosectomy. As for the initial drainage, continuous and abundant daily irrigation was initiated, ranging from 0.5 to 1.5 L/drain/day of normal saline, depending on the size of the collection. The time from admission until PCD (delay of drainage [DOD] or date of death) was recorded and calculated from the first day of hospitalization. Catheter management Catheters were regularly changed, at least once a week, especially if drainage decreased or signs of infection reappeared. Systematic gentle injection of contrast medium through the catheters permitted us to control the necrotic cavity size and the catheter s position and to look for a digestive or pancreatic fistula. CT scan controls were also performed, initially once a week and then every 2 weeks, to check the disease s evolution and drainage s efficacy. The decision to remove the catheters and stop the drainage was a consensual multidisciplinary decision based on clinical improvement (i.e., control of the sepsis, defervescence of the fever, and hemodynamic stability), biologic improvement (i.e., stable return of WBC to normal and dramatic and stable decrease of the CRP level), resolution of the necrotic cavity on CT and fluoroscopic control, and when the amount of drain fluid was less than 10 ml/day (Fig. 2). Complications PCD-related complications were recorded and classified as minor or major according to the Society of Cardiovascular and Interventional Radiology classification [18]. Outcome Assessment Technical success Technical success was defined as adequate placement of one or more drainage catheters into the target necrotic cavities, with confirmation by means of subsequent aspiration of cavity fluid and CT scan control. Clinical success Clinical success was defined when the three following parameters were achieved: control of the sepsis, resolution of the necrotic cavities on imaging, and no requirement for surgical necrosectomy. In case of suspected failure of the PCD treatment, a multidisciplinary roundtable decided on the patient s outcome, by performing a surgical necrosectomy. Mortality The occurrence of a death was recorded to allow an analysis of the factor influencing the global and early mortality rates. Statistical Analysis Results were expressed as mean (± SD) and range. Univariate analysis was performed with the Mann-Whitney U test for continuous variables and with the Fisher exact or chi-square test for categoric variables. Multiple logistic regression analysis was used to explain clinical success with calculation of odds ratios and 95% CIs. For both death and DOD, Kaplan-Meier curves were compared using the logrank test. The best cutoff for DOD was defined as the one that offered the best compromise between true-positive and false-negative. A Cox proportional hazards model was used to explain death and its delay of occurrence, with calculation of hazard ratio and 95% CI. A p value of less than 0.05 was considered to indicate a statistically significant difference. Statistical analysis was performed with SAS software (version 9.1, SAS Institute). Results Hospitalization The mean hospital stay for our patients was 83 ± 48 days (range, days). Patients for whom PCD was a clinical success were hospitalized for an average of 101 ± 42.5 days (range, days), including 48 ± 22 days of drainage (range, days). ICU hospitalization was required for 31 of 48 patients (64.6%), with a mean length of stay of 30.2 ± 29.8 days (range, days). Predictive Scores and Serum C-Reactive Protein Level The average Ranson score was 3.5 ± 1.4 (range, 1 6). The Ranson score was less than 3 for nine patients, 3 5 for 28 patients, and greater than 6 for three patients. For eight patients, the score could not be calculated because of missing data. The APACHE II score was 14.8 ± 5.6 (range, 4 24) for 24 of the 31 patients admitted to the ICU (seven patients had missing data). Most of the patients with missing data had been transferred from a peripheral hospital. The initial serum CRP level was 282 ± 119 mg/l (range, mg/l) in the overall population, 275 ± 94 mg/l (range, mg/l) in PCD-cured patients, and 310 ± 154 mg/l (range, mg/l) in patients who were not cured with PCD. Among patients who were cured with PCD, the CRP level 194 AJR:199, July 2012

4 CT-Guided Drainage of Acute Necrotizing Pancreatitis was 132 ± 77 mg/l (range, mg/l) at midterm, 49 ± 32 mg/l (range, mg/l) at removal of the catheters, and 33 ± 36 mg/l (range, mg/l) at discharge. The overall gravity of our patient s conditions is summarized in Table 1 according to AP severity criteria as defined by the International Symposium on Acute Pancreatitis [19]. Imaging On the initial contrast-enhanced CT, 42 patients had disease of Balthazar score E and six had disease of Balthazar score D. The necrosis extent was less than 30% in 19 patients, 30 50% in 12 patients, and greater than 50% in 15 patients. The CT severity index averaged 7.7 ± 1.8 (range, 5 10). One A D Fig year-old man with infectious pancreatic necrosis (IPN) that was cured with percutaneous catheter drainage (PCD). A, Contrast-enhanced CT scan obtained at day 28 after onset of disease shows subtotal gland necrosis (arrowheads) and extensive gas within area of necrosis (star) indicating IPN. B, CT-guided fine-needle aspiration of pancreatic collection using 18-gauge needle (arrow) was performed with retroperitoneal approach. Aspiration showed purulent material. C, Double-sump 16-French catheter (arrow) was placed in necrotic cavity using Seldinger technique. D, Unenhanced CT scan obtained 7 days after drainage procedure shows reduction in size of necrotic space (arrowheads). Note that catheter shown in panel (C) has been exchanged for 28-French double-sump catheter (arrow). E, Gentle injection of diluted iodine through radiologic drain (arrowhead) under fluoroscopic guidance 38 days after PCD shows opacification of digestive tract due to duodenal fistula (arrow). F, Contrast-enhanced CT scan obtained 6 months after treatment only shows some persistent heterogeneous areas of enhancement on pancreatic tail (arrow). hundred ten necrotic collections were identified, with a mean of 2.3 ± 0.8 collections per patient (range, 1 5 collections/patient). Bacteriological Analysis Entrance criteria required all subjects to have infected pancreatic necrosis, as determined by aspiration; of these, 22 (47%) cases were polymicrobial. The different organisms cultured were gram-negative bacilli. PCD PCD required the placement of 89 catheters in 110 necrotic collections, averaging 1.8 ± 0.8 catheters per patient (range, 1 4 catheters/ patient). Repartition was made as follows: 17 patients had only one catheter, 23 patients had B E two catheters, six patients had three catheters, and two patients had up to four catheters placed at some point. The average drain diameter was 24.4 ± 4.4 French (range, French). The delay between the start of the hospitalization and the need to start the drainage was, on average, 19.8 ± 15.7 days (range, 2 90 days). Catheters were revised and exchanged 360 times, averaging 7.5 ± 4.1 catheter changes per patient (range, 0 17 catheter changes/patient). These changes occurred every 4.6 ± 1.2 days (range, days). Technical Success Technical success was achieved in 100% of our patients (48/48), with a good placement of our catheter in the infected necrotic cavities. C F AJR:199, July

5 Baudin et al. A B C Fig year-old man with infectious pancreatic necrosis with uncontrolled sepsis despite optimal percutaneous catheter drainage (PCD). A, Contrast-enhanced CT scan performed 48 hours after onset of symptoms shows extensive gland necrosis (star). B, Enhanced CT scan obtained after PCD shows persistence of extensive gas within area of proven infected necrosis (arrowheads) and one of two 28-French doublesump catheters (arrow) placed in this patient 10 days after scan described in A. Sepsis could not be controlled by PCD alone, and patient benefited from surgical necrosectomy 3 weeks after catheter placement. C, Contrast-enhanced CT scan performed 2 months after surgery shows almost complete collapse of necrotic space with persistent residual unenhanced pancreatic parenchyma (arrow). Clinical Success Among the 48 patients of our study, clinical success was achieved for 31 (64.6%). Clinical success was significantly associated with the Ranson score (p = 0.01), with an average score of 2.9 ± 1.2 (range, 1 5) in cases of successful PCD treatment versus 4.3 ± 1.3 (range, 2 6) in cases of failed PCD treatment. The delay between hospital admission and the beginning of drainage was strongly related to success (p = 0.005), with an average delay of 24 ± 18 days (range, 3 90 days) in successfully treated patients versus 12 ± 7 days (range, 2 27 days) in cases of treatment failure. PCD was successful in 88% (22/25) of our patients if drainage was performed 18 days or more after admission. Conversely, only 39% (9/23) of patients were cured if drainage was performed before this threshold (odds ratio, 10.9; 95% CI, ; p = 0.001). Among the 17 patients for whom PCD failed, nine required surgical treatment Surviving Patients (%) Ranson Score < 3 Ranson Score Days of uncontrolled sepsis, and the remaining eight died of multiorgan failure. Control of Sepsis None of the 31 patients for whom sepsis was controlled by means of PCD died or needed a surgical treatment in relation to the IPN. Among the 17 other patients, 13 died (76%), including five after surgery, whereas four were subsequently cured with surgery. A single patient died during his hospital stay, despite PCD sepsis control after removal of the catheters, from a massive pulmonary embolism. Ranson Score Fig. 4 Kaplan- Meier curves show occurrence of death and its delay according to different Ranson score groups. Drainage-Related Complications Only two (4%) major drainage-related complications were recorded. During a catheter exchange session, two patients had hemorrhagic episodes, with bleeding through the drainage s cutaneous holes, that were not controlled by the drain replacement. A celiomesenteric arteriography was then performed and was normal. Bleeding ceased spontaneously without consequence for the patient, and no blood transfusion was needed for either of the two patients. Minor complications occurred in all of our patients, most often related to catheter obstruction caused by necrotic debris, pain, or catheter site leakage. Technical complications also happened, with a lost drainage route during a catheter exchange and a catheter pulled out by the patient. Fistulas Sixteen patients had 18 fistulas identified during catheter drainage, including 13 gastrointestinal (eight to the duodenum, three to the colon, and three to the small bowel) and five pancreatic fistulas. These fistulas arose away from the catheter and resolved spontaneously in three patients, with the help of enteral feeding in six patients, or with endoscopic or surgical treatment in seven patients. The presence of a fistula resulted in a longer hospital stay, with an average of 113 ± 45 days (range, days) versus 97 ± 37 days (range, days) in patients without fistulas. It also extended the duration of drainage (61 ± 27 days [range, days] vs 41 ± 17 days [range, days]). No significant difference was found for clinical success or surgery requirement (associated with IPN treatment as defined). Surgery Requirement Nine patients (19%) failed to show clinical improvement by remaining septic and required 196 AJR:199, July 2012

6 CT-Guided Drainage of Acute Necrotizing Pancreatitis Surviving Patients (%) Days surgical necrosectomy (Fig. 3). The average delay to start drainage in these patients was 10.2 ± 6 days (range, 2 19 days); only one patient had to undergo drainage after the 18th day. Five of these patients (55.6%) died even after surgical treatment. The other four, including the one who underwent drainage after day 18, were cured with an average hospital stay of 90.5 ± 32 days (range, days). Global and Early Mortality Global mortality Fourteen patients (29%) died in the hospital, with an average delay of occurrence of 37 ± 25.2 days (range, days). Univariate analysis managed to show a statistically significant association with the Ranson score (p = 0.01), with a score of 3 ± 1.1 (range, 1 5) among the surviving patients versus 4.3 ± 1.6 (range, 1 6) among the deceased ones (Fig. 4). The DOD was also significant for the global mortality (p = 0.04), with an average delay of 23 ± 18.7 days (range, 3 90 days) among surviving patients versus 13 ± 7.5 days (range, 2 27 days) among the deceased. As for clinical success, the 18th-day threshold remained the most significant factor (hazard ratio, 5.1; 95% CI, ; p = 0.01) (Fig. 5), with an overall mortality rate of 47.8% (11/23) if early drainage was needed. On the other hand, only 12.5% (3/25) of the patients who underwent drainage after the 18th-day threshold died (Fig. 6). Early mortality Seven (14.6%) of our patients died within the first month of hospitalization. The variables significantly influencing early mortality were the same as those influencing the global mortality that is, the Ranson score (p = 0.03) and the DOD (p = 0.01). All seven patients who died within the first 30 days had to undergo drainage before the 18th day, with an average delay of 9 ± 5.3 days (range, 2 17 days), versus 21 ± 16.6 days for the others. PCD Day 18 PCD < Day Discussion PCD of IPN is a well-recognized minimally invasive alternative treatment to primary surgical necrosectomy. However, only a few surveys are available. The pitfalls of these studies are a low level of evidence with a limited total number of patients. The populations studied and the PCD procedures are heterogeneous, according to the different authors, with a various and wide range of clinical success and mortality rates [12]. The main explanation for this fact is that only a few of these studies really use the different definitions provided by the International Symposium on Acute Pancreatitis criteria to assess predicted and actual severity, organ failure, and local complications [20]. Freeny et al. [21] first described a homogeneous group of 34 patients exclusively treated by PCD for IPN using precise definitions of necrosis and infection. They recorded a clinical success rate of 47% and were able to identify multiorgan failure and central necrosis on CT as two predicting factors of poor response to catheter drainage. Fig. 6 Influence of delay of drainage among clinical success and global mortality. PCD = percutaneous catheter drainage, white bars = patients who underwent PCD, black bars = decreased patients, light gray bars = clinical successes, dark grey bars = patients requiring surgery. Fig. 5 Kaplan- Meier curves show occurrence of death and its delay according to 18th-day threshold. PCD = percutaneous catheter drainage. Patients The clinical success rate in the present study (64.6%) is in the range of the main studies on this topic [12, 21 31]. The clinical success rate was influenced by the Ranson score, but the International Symposium on Acute Pancreatitis criteria classic threshold was not recognized as a significant factor by our univariate analysis, probably because of the overall high severity of the AP in our series (Table 1). The last variable influencing clinical success was the DOD, especially the 18th-day threshold identified by our statistical analysis. Eight studies report these data in their results, with delays ranging from 1 to 154 days [12, 21, 25 28, 30, 31]. None of them identified DOD as an influencing factor of success or mortality. The main challenge in AP is to classify it as severe or mild as early as possible. Several tools can be used for this task, including predictive scores (e.g., Ranson or APACHE II) or CT (e.g., CT severity index), but none of them are specific to infected necrosis. If sepsis and organ failure occur early in the evolution of the disease despite optimal medical treatment, requiring early catheter drainage, we think that the DOD could be a good marker of severity in patients with IPN. For years, this observation has already been made by surgeons, who used to operate on patients with pancreatic necrosis within the first 72 hours, with high rates of mortality and morbidity. Then, the consensus was to treat these patients medically as long as possible and to operate on them later, during the third or fourth week, resulting in a dramatic decrease in mortality and morbidity rates [32]. In our survey, patients who experienced particularly severe AP with early IPN, indicating the completion of PCD before the 18th Delay in Days to Start PCD >25 0 AJR:199, July

7 Baudin et al. day, were cured in only 39% of cases, versus 88% of patients for whom PCD was performed after this threshold (Fig. 6). PCD also seems to be a safe technique with only two nonlethal major complications. Likewise, none of the 18 fistulas identified could be directly related to the catheter placement, and most authors consider them as an inner complication of AP and not of the PCD [22, 33, 34]. Surgery is always warranted by uncontrolled sepsis. The rate of 19% in the present study for secondary-intent surgical intervention is low according to the available figures in the literature, which range from 0% to 83% [12, 22 30]. Our global mortality rate is quite high compared with that reported in the literature. We think that this difference is caused by two main facts: the overall gravity of disease in our population and the exclusive presence of IPN [12, 22 30]. A large number of the studied variables, such as the APACHE II score, CT scores, and drainage characteristics, did not appear to influence mortality or clinical success rates. This phenomenon is certainly related to three major reasons. Two of them are limitations of our study its retrospective nature and the small size of our population and the third reason is linked to the homogeneity of the population in our study. The average hospital stay of 101 days among the cured patients and the average drainage time of 48 days underline the fact that PCD is a long and very demanding treatment that, to be effective, requires a great deal of effort and commitment by the interventional team. As already described by most authors and despite all the significant variables identified in the different surveys, we also think that clinical success and mortality rely mainly and strongly on the commitment and the close cooperation among radiologists, surgeons, gastroenterologists, and intensivists who are willing to take care of such patients [35]. However, these figures also highlight one of the main pitfalls of this technique. Indeed, this treatment requires long-term hospitalization with catheters in place for up to 96 days and an average of 7.6 visits to the radiology unit when, for selected patients, a single visit to the operating room can sometimes solve the problem. The main problem here is to be able to identify patients who will benefit the most from one treatment modality or the other, or even a combination of both techniques. At present, it is impossible to do this, because nobody could provide that information, and the probability of seeing a prospective randomized study comparing the different techniques is very low. It is the same for the PCD technique and the use of preferential types of catheter, size, and management, which is guided more by the experience of each team rather than by strong bibliographic evidence. This study emphasizes a major therapeutic problem in the choice of alternative treatments for patients for whom clinical evolution of IPN requires intervention, despite an optimized medical treatment. However, PCD seems to be an effective and safe alternative to surgery for this specific disease. References 1. Beger HG, Rau B, Mayer J, Pralle U. Natural course of acute pancreatitis. World J Surg 1997; 21: Bradley EL 3rd. 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Outcome of patients with acute, necrotizing pancreatitis requiring drainage: does drainage size mat- 198 AJR:199, July 2012

8 CT-Guided Drainage of Acute Necrotizing Pancreatitis ter? World J Gastroenterol 2008; 14: Berzin TM, Banks PA, Maurer R, Mortele KJ. CT-guided percutaneous catheter drainage in necrotizing pancreatitis: outcomes among patients discharged with drains in place. J Vasc Interv Radiol 2008; 19: Mortelé KJ, Girshman J, Szejnfeld D, et al. CTguided percutaneous catheter drainage of acute necrotizing pancreatitis: clinical experience and observations in patients with sterile and infected necrosis. AJR 2009; 192: Rocha FG, Benoit E, Zinner MJ, et al. Impact of radiologic intervention on mortality in necrotizing pancreatitis: the role of organ failure. Arch Surg 2009; 144: van Santvoort HC, Besselink MG, Bakker OJ, et al. A step-up approach or open necrosectomy for necrotizing pancreatitis. N Engl J Med 2010; 362: Cheung MT, Ho CN, Siu KW, Kwok PC. Percutaneous drainage and necrosectomy in the management of pancreatic necrosis. ANZ J Surg 2005; 75: Hartwig W, Maksan SM, Foitzik T, Schmidt J, Herfarth C, Klar E. Reduction in mortality with delayed surgical therapy of severe pancreatitis. J Gastrointest Surg 2002; 6: Fielding GA, McLatchie GR, Wilson C, Imrie CW, Carter DC. Acute pancreatitis and pancreatic fistula formation. Br J Surg 1989; 76: Ferrucci JT 3rd, Mueller PR. Interventional approach to pancreatic fluid collections. Radiol Clin North Am 2003; 41: [vii] 35. Mueller PR. Percutaneous drainage of pancreatic necrosis: is it ecstasy or agony? AJR 1998; 170: FOR YOUR INFORMATION Malpractice Issues in Radiology, 3rd edition, by Leonard Berlin, is now available! For more information or to purchase a copy, see AJR:199, July