Transluminal closure for NOTES: an ex vivo study comparing leak pressures of various gastrotomy and colotomy closure modalities.

BACKGROUND AND STUDY AIMS: Transluminal closure is fundamental to the safe introduction of natural orifice transluminal endoscopic surgery (NOTES) into humans. Suture, staples, and clips have been used. We aimed to evaluate the acute strength of various gastrotomy and colotomy closure techniques in an ex vivo porcine model by assessing air leak pressures. PATIENTS AND METHODS: The following closure modalities were assessed with at least five samples per arm: conventional open/laparoscopic suturing techniques including full-thickness interrupted sutures, double-layer sutures, and purse-string sutures, as well as endoscopic clips and endoscopic staples. Historical values for transgastric closures with hand-sewn interrupted sutures, endoscopic clips, and a prototype endoscopic suture device were used from our laboratory's prior study. RESULTS: Using Kruskal-Wallis analysis, the overall comparisons were significant ( P = 0.0038 for gastrotomy closure; P = 0.0018 for colotomy closure). Post hoc paired comparisons revealed that the difference between all closure arms versus negative control were significant. Significance could not be established among the various closure arms. However, trends suggested hand-sewn double-layer sutures, endoscopic staples, and both hand-sewn and endoscopically-placed purse-string sutures produced the strongest closures. Furthermore, endoscopic clips appeared sufficient for colotomy closure when ideally placed. CONCLUSIONS: Suture (both hand-sewn and endoscopically deployed) appears to produce the strongest closures in both stomach and colon, with the important caveats that (1) a continuous through-thickness suture track be avoided, such as in the full-thickness closure, or (2) suture holes be buried, such as in the purse-string configuration. When suture tracks are full-thickness, they can serve as leak sites. Staples and clips can produce comparable closures, but only under ideal conditions.

Natural orifice transesophageal mediastinoscopy and thoracoscopy.

BACKGROUND: Thoracoscopy and mediastinoscopy are common procedures with painful incisions and prominent scars. A natural orifice transesophageal endoscopic surgical (NOTES) approach could reduce pain, eliminate intercostal neuralgia, provide access to the posterior mediastinal compartment, and improve cosmesis. In addition NOTES esophageal access routes also have the potential to replace conventional thoracoscopic approaches for medial or hilar lesions. METHODS: Five healthy Yorkshire swine underwent nonsurvival natural orifice transesophageal mediastinoscopy and thoracoscopy under general anesthesia. An 8- to 9.8-mm video endoscope was introduced into the esophagus, and a 10-cm submucosal tunnel was created with blunt dissection. The endoscope then was passed through the muscular layers of the esophagus into the mediastinal space. The mediastinal compartment, pleura, lung, mediastinal lymph nodes, thoracic duct, vagus nerves, and exterior surface of the esophagus were identified. Mediastinal lymph node resection was easily accomplished. For thoracoscopy, a small incision was created through the pleura, and the endoscope was introduced into the thoracic cavity. The lung, chest wall, pleura, pericardium, and diaphragmatic surface were identified. Pleural biopsies were obtained with endoscopic forceps. The endoscope was withdrawn and the procedure terminated. RESULTS: Mediastinal and thoracic structures could be identified without difficulty via a transesophageal approach. Lymph node resection was easily accomplished. Pleural biopsy under direct visualization was feasible. Selective mainstem bronchus intubation and collapse of the ipsilateral lung facilitated thoracoscopy. In one animal, an inadvertent 4-mm lung incision resulted in a pneumothorax. This was decompressed with a small venting intercostal incision, and the remainder of the procedure was completed without difficulty. CONCLUSIONS: Transesophageal endoscopic mediastinoscopy, lymph node resection, thoracoscopy, and pleural biopsy are feasible and provide excellent visualization of mediastinal and intrathoracic structures. Survival studies will be needed to confirm the safety of this approach.

Transcolonic ventral wall hernia mesh fixation in a porcine model.

BACKGROUND AND STUDY AIMS: A natural orifice transluminal endoscopic surgery (NOTES) approach to ventral wall hernia repair may represent a potentially less invasive alternative to current transabdominal surgical techniques. We aimed to investigate the feasibility of using transcolonic NOTES to deliver hernia repair mesh into the peritoneal cavity, as well as the ability to manipulate composite mesh and secure it to the abdominal wall. METHODS: Five pigs weighing 20 to 25 kg were used in this feasibility study involving two acute and three survival experiments. A prototype mesh delivery system was used to transfer 1.5 - 2-cm x 2.5 - 3-cm pieces of composite hernia mesh into the peritoneal cavity. Neodymium magnets on a prototype control arm were used to help position the mesh by magnetically engaging previously placed endoscopic clips. Transfascial fixation of the mesh with 3-0 monofilament sutures was achieved using a 19-gauge hollow needle, pusher wire, and a suture tag system. RESULTS: Composite hernia mesh was successfully transferred and secured in 5/5 attempts. All three survival animals thrived for 14 days prior to elective sacrifice. At necropsy, the mesh sites were found to be well peritonealized without adhesions. Suture placement through the posterior fascia was confirmed in 10/12 sutures. Of these, four sutures were within the abdominal musculature, and two sutures were through the anterior fascia (transfascial). CONCLUSIONS: Transcolonic delivery, transcutaneous magnetic manipulation, and fixation of composite hernia mesh are technically feasible in a porcine model with animal survival. An effective suturing method that allows consistent anchoring through the anterior fascia would be preferred and may require the development of novel devices.

Dual-port distal pancreatectomy using a prototype endoscope and endoscopic stapler: a natural orifice transluminal endoscopic surgery (NOTES) survival study in a porcine model.

BACKGROUND AND STUDY AIMS: Natural orifice transluminal endoscopic surgery (NOTES) is a potentially less invasive alternative to laparoscopic surgery that may be applicable to distal pancreatectomy. We aimed to demonstrate the technical feasibility of a NOTES distal pancreatectomy in an in vivo porcine model via a combined transvaginal-transcolonic approach. MATERIAL AND METHODS: The procedure was performed in five female Yorkshire pigs weighing approximately 30 kg each. A prototype endoscope ("R-scope"), advanced into the peritoneal cavity through an anterior colotomy, and a computer-assisted linear stapler, introduced transvaginally, were used in dissection and resection of the distal pancreas. Prone positioning was used to enhance retroperitoneal exposure. Pneumodissection was used for blunt dissection. The colotomies were closed with endoloops. Necropsies were done immediately after the procedure in the first three animals, and after 2 weeks' survival in the final two animals. RESULTS: Distal pancreatectomy was successful in all five animals. Prone positioning was critically important for proper exposure of retroperitoneal and pelvic structures. Pneumodissection was effective for blunt dissection, and both the linear stapler and R-scope functioned smoothly. Transvaginal and transcolonic access provided similar intraperitoneal views, and the dual-lumen approach enhanced triangulation. Both survival animals thrived postoperatively. Necropsies revealed clean staple lines; closed transcolonic and transvaginal incisions; and absence of infection, hemorrhage, or fluid collections. CONCLUSIONS: NOTES distal pancreatectomy is technically feasible in the porcine model. The transvaginal approach provides a vantage point very similar to that of the transcolonic route and holds promise as a NOTES access site, either singly or as part of a dual-lumen approach. The endoscopic linear stapler and R-scope both advance NOTES capabilities. The novel concepts of fully prone positioning, pneumodissection, and endoloop colotomy closures are introduced. Considering anatomical differences and that healthy animals were used, transferring this technique to patients with pancreatic disease might be difficult and further modifications would likely be needed.

Operative time is a poor surrogate for the learning curve in laparoscopic colorectal surgery.

BACKGROUND: Previous studies have relied on conversion rate and operative time for construction of learning curves in laparoscopic colorectal surgery. The authors hypothesized that conversion rate and operative time were less important than complication and readmission rates in defining good outcomes and hence the learning curve. METHODS: A database of 287 consecutive laparoscopic colorectal resections from a single tertiary referral center was analyzed. Outcome measures included operative time, conversion rate, major and minor complications, length of hospital stay, and the 15- and 30-day hospital readmission rate. Data were analyzed both by surgeons and by quartile case numbers. RESULTS: A total of 151 right colectomies and 136 left colectomies were performed between 1995 and 2005. For both right and left colectomies, the conversion rate decreased in each of the first three quartiles, reaching a nadir of 0% for right colectomies and 3% for left colectomies in the third quartile. The conversion rates increased slightly in the fourth quartile. The operative time remained stable for three quartiles, then increased slightly in the fourth quartile. Two surgeons managed 199 of the 287 cases. Analysis of the two high-volume surgeons demonstrated that for left-sided resections, the surgeon with the shorter operative times had the higher major complication rate (13% vs 2%), overall complication rate (22% vs 2%), 30-day readmission rate (13% vs 0%), and length of stay (3.8 vs 3.1 days) (p < 0.05 for all comparisons). CONCLUSIONS: In this series, operative time failed to decrease with experience, and shorter operative times did not correlate with better clinical outcomes. The failure of operative time to decline with experience often reflects surgeons' willingness to attempt more difficult cases rather than an accurate representation of a "learning curve." Therefore, complication and readmission rates are more important than operative time and conversion rates for evaluating the learning curve and quality of laparoscopic colorectal surgery.

Evaluating an optimal gastric closure method for transgastric surgery.

BACKGROUND: The transgastric approach is currently being studied as a potentially less invasive alternative to conventional laparoscopy for intra-abdominal surgery. A major obstacle to overcome is the closure of the transgastric incision in a rapid, reproducible, and safe manner. The effectiveness of various techniques for gastrotomy closure were compared by assessing leak pressures in an ex vivo porcine stomach model. METHODS: Whole stomachs from adult white pigs were suspended in a Plexiglas box to facilitate endoscopic technique. Standard gastrotomies were made by needle knife incision and dilation with a controlled radial expansion (CRE) balloon. The first arm used standard QuickClips; the second, a prototype device developed by LSI Solutions; the third, hand-sewn by a senior surgeon; the final, a control with open gastrotomy. Five stomachs were tested per study arm. After closure, each stomach was inflated by an automated pressure gauge. The pressures to achieve air leakage and liquid leakage were recorded. RESULTS: The unclosed controls demonstrated air leakage at a median pressure of 15 mmHg, representing baseline system resistance. The QuickClip closures leaked air at a median pressure of 33 mmHg. The prototype gastrotomy device yielded the highest median air leak pressure of 85 mmHg while dramatically diminishing time for incision and gastrotomy closure to approximately 5 min. The hand-sewn closures leaked air at a median pressure of 47 mmHg. Using Kruskal-Wallis statistical analysis, the comparisons were significant (p = 0.0019). Post hoc paired comparisons using MULTTEST procedure with both Bonferroni and bootstrap adjustments revealed that the difference between prototype and clips was significant; prototype versus hand-sewn was not. Liquid-leak pressures produced similar results. CONCLUSIONS: The prototype device decreases procedure time and yields leak-resistant gastrotomy closures that are superior to clips and rival hand-sewn interrupted stitches.

Changes in serum ghrelin predict weight loss after Roux-en-Y gastric bypass in rats.

BACKGROUND: Although Roux-en-Y gastric bypass (RYGB) is an effective and widely used therapy for severe obesity, the mechanisms by which it induces weight loss are not well understood. Several studies have shown that RYGB in human patients causes a decrease in circulating levels of ghrelin, a gastric hormone that strongly stimulates food intake. Substantial variation in the effect of RYGB on serum ghrelin has been reported in different studies and among individual patients, suggesting that regulation of this hormone is complex and subject to genetic and other patient-specific factors. To control for these factors and to enable more detailed study of physiologic mechanisms, we have recently developed a clinically relevant rat model of RYGB. In this study, we used this model to examine the effect of RYGB on serum ghrelin levels. METHODS: Fifteen Sprague-Dawley rats that had received a high-fat diet to induce moderate obesity underwent RYGB. The operation closely resembled the procedure in humans. Serum samples were collected 1 month before and 3 months after RYGB, and serum ghrelin levels were measured. The primary outcomes of the study were the changes in body weight, food intake, and circulating ghrelin levels after RYGB. A multiple linear regression model was developed to examine the relationship between ghrelin levels and weight change after RYGB. RESULTS: Three months after the procedure, RYGB-treated rats weighed 20 +/- 5% less than they would have, had they not undergone the procedure. Despite the weight loss, serum ghrelin levels were 38 +/- 6% lower than before surgery. There was appreciable variation in the weight loss in individual animals, and preoperative weight and pre- and postoperative ghrelin levels were the best predictors of postoperative weight loss. Thus, the animals who had the greatest weight loss were those that were heaviest before surgery. These rats had the highest preoperative and lowest postoperative ghrelin levels. CONCLUSIONS: Using our recently developed rat model of RYGB, we found that postoperative weight loss is correlated with the magnitude of the decrease in circulating ghrelin levels. This correlation provides the strongest evidence to date that altered ghrelin signaling contributes to weight loss after this operation. The lower level of circulating ghrelin after RYGB likely blunts the appetitive drive, leading to decreased food intake in these animals.

Long-term results of intraoperative electron beam radiotherapy for primary and recurrent retroperitoneal soft tissue sarcoma.

PURPOSE: This study assesses the long-term outcome of patients with retroperitoneal sarcoma treated by preoperative external beam radiotherapy, resection, and intraoperative electron beam radiation (IOERT). METHODS AND MATERIALS: From 1980 to 1996, 37 patients were treated with curative intent for primary or recurrent retroperitoneal soft tissue sarcoma. All patients underwent external beam radiotherapy with a median dose of 45 Gy. This was followed by laparotomy, resection, and IOERT, if feasible. Twenty patients received 10-20 Gy of IOERT with 9-15 MeV electrons. These patients were compared to a group of 17 patients receiving preoperative irradiation without IOERT. RESULTS: The 5-yr actuarial overall survival (OS), disease-free survival, local control (LC), and freedom from distant disease of all 37 patients was 50%, 38%, 59%, and 54%, respectively. After preoperative irradiation, 29 patients (78%) underwent gross total resection. For 16 patients undergoing gross total resection and IOERT, OS and LC were 74% and 83%, respectively. In contrast, these results were less satisfactory for 13 patients undergoing gross total resection without IOERT. For these patients, OS and LC were 30% and 61%, respectively. Four patients experienced treatment-related morbidity. CONCLUSIONS: In selected patients, IOERT results in excellent local control and disease-free survival with acceptable morbidity.

Peritoneal exfoliative cytology and Ki-ras mutational analysis in patients with pancreatic adenocarcinoma.

This is the first description of the detection of pancreatic adenocarcinoma peritoneal metastasis by established radiolabeled polymerase chain reaction (PCR) based Ki-ras mutational analysis. The present study evaluates both routine cytology and Ki-ras mutational analysis in the detection of peritoneal micrometastases in 24 subjects with pancreatic adenocarcinoma compared to seven control cases of chronic pancreatitis and seven control cases of cholecystitis. Locoregional extension, vascular invasion, and distal metastases were confirmed in 21/24 (88%) of the subjects with pancreatic adenocarcinoma by compute tomography, angiography, endosonography, or laparoscopy. The most common site of histologically confirmed extrapancreatic involvement was the vasculature (29%), followed by the liver (25%), duodenum (17%), peritoneum (17%), and lymph nodes (12%). Peritoneal lavage cytology was positive in 3/24 (12%) cases of pancreatic carcinoma while Ki-ras codon 12 mutational analysis was positive in 2/24 (8%). Two histologically confirmed cases of peritoneal metastases were not detected by either methodology, while peritoneal lavage cytology detected malignant cells in one case with histologically confirmed lymph node metastasis.

Giant cell tumor of the pancreas of mixed osteoclastic and pleomorphic cell type: evidence for a histogenetic relationship and mesenchymal differentiation.

We describe a giant cell tumor of the pancreas composed of a mixture of osteoclastic and pleomorphic cell types. This rare tumor had a unique immunohistochemical profile. Both types of tumor giant cells stained for vimentin, alpha-1-antitrypsin, alpha-1-antichymotrypsin, synaptophysin, muscle actin, and neuron-specific enolase, but not for epithelial markers. Electron microscopy showed cells which resembled primitive fibroblasts and osteoclast with no epithelial features. These findings are most consistent with mesenchymal differentiation. The extensive homologies in immunohistochemical staining of both osteoclastic and pleomorphic giant cells in this case indicates that these cells are histogenetically related.

Measuring improved quality of life after laparoscopic Nissen fundoplication.

BACKGROUND: While the correction of pathologic gastroesophageal reflux by means of laparoscopic Nissen fundoplication (LNF) has been well documented, the psychological profiles of patients with this disease and the impact on their quality of life are less well understood. We obtained a baseline psychological profile and measured the impact of LNF on patients' quality of life with 2 standardized instruments: the psychological general well-being index (PGWB) and the gastrointestinal symptoms rating scale (GSRS). The study included 34 consecutive patients with typical symptoms of gastroesophageal reflux who underwent LNF in 1995 at a tertiary care university medical center. METHODS: Patients filled out PGWB and GSRS surveys preoperatively and at 2 weeks, 2 months, and 12 months postoperatively. Data were collected in a blinded fashion by a study nurse and analyzed after completion of the study. Data are expressed as mean +/- standard deviation. RESULTS: The mean preoperative PGWB score (69.6 +/- 17.3) of study patients with gastroesophageal reflux disease was lower than that expected for a healthy population. This was primarily attributable to low scores in the general health domain of the questionnaire, although LNF patients also had low scores in the vitality and positive well-being domains of the PGWB scale. LNF improved the PGWB score to a normal level (78.7 +/- 19.3) (P = .05 vs the preoperative PGWB score) at 12 months post surgery. The GSRS also showed improvement from 34.7 +/- 7.8 to 28.1 +/- 10 (P = .008). The improvement in GSRS was attributed to improvement in the heartburn (7.12 +/- 2.4 to 2.72 +/- 1.2, P < .001) and abdominal pain (6.58 +/- 2.5 to 4.92 +/- 1.6, P = .006) domains of the scale. LNF had no impact on the diarrhea, indigestion, and obstipation domains of the GSRS. CONCLUSIONS: Patients with gastroesophageal reflux disease who are candidates for LNF have low psychological and general well-being scores that are restored to normal levels by successful LNF. When compared with baseline measurements, LNF effectively relieved heartburn and did not cause significant new gastrointestinal complaints.

Outcomes of atypical symptoms attributed to gastroesophageal reflux treated by laparoscopic fundoplication.

BACKGROUND: The introduction of laparoscopic fundoplication (LF) has lowered the threshold for operation in patients with symptoms attributed to gastroesophageal reflux. We sought to determine whether the outcomes in patients referred for atypical symptoms (pulmonary, pharyngolaryngeal, and pain syndromes) were as good as those referred for correction of heartburn and regurgitation (typical symptoms). METHODS: Thirty-five of 150 consecutive patients undergoing LF with a minimum of 12 months of follow-up were referred primarily for correction of atypical symptoms. A standard preoperative evaluation included endoscopy, manometry, upper gastrointestinal contrast radiography, and 24-hour pH probe testing (33 of 35 patients with atypical symptoms). Patients completed a symptom questionnaire administered by a study nurse before the operation and 3 and 12 months after the operation. Symptoms were scored from 0 to 10. RESULTS: Heartburn was relieved by LF in 93% of patients, whereas only 56% of patients had relief of atypical symptoms. Furthermore, the degree of improvement in typical symptoms was greater than that seen for atypical symptoms as measured by the 0 to 10-symptom rating score (improvement in typical symptoms = 6.2 vs improvement in atypical symptoms = 4.4 [p = 0.01]). The response rate for laryngeal, pulmonary, and epigastric/chest pain symptoms was 78%, 58%, and 48%, respectively. Analysis of factors associated with relief of atypical symptoms revealed that response to a preoperative trial of omeprazole or H2-blockers was significantly associated with successful surgical outcome (p = 0.03). Six of seven patients with laryngeal symptoms who had acid reflux above the cricopharyngeal level shown by dual-probe pH testing had relief of the symptoms after LF. Manometric findings (amplitude of esophageal body contractions, propagation of contractions, and lower esophageal sphincter resting pressure) neither predicted nor correlated with relief of atypical symptoms after the operation. CONCLUSIONS: Relief of atypical symptoms attributed to gastroesophageal reflux by LF is less satisfactory and more difficult to predict than relief of heartburn and regurgitation. The only useful preoperative predictors of relief of atypical symptoms in this study were the response to pharmacologic acid suppression and dual-probe pH testing (only in patients with laryngeal symptoms).

Pancreatic microcirculatory changes in experimental pancreatitis of graded severity in the rat.

BACKGROUND: A technique with two complementary methods, intravital microscopy (IVM) and diffuse reflectance spectroscopy (DRS), was developed to analyze pancreatic tissue perfusion. METHODS: After initial in vivo and in vitro validation of the techniques, we studied pancreatic microcirculation in models of mild, moderate, and severe pancreatitis. Anesthetized Sprague-Dawley rats were randomly allocated to the three models or to serve as controls. Stable systemic hemodynamic parameters were maintained with normal saline solution infusion. Exocrine capillary perfusion was assessed by IVM; hemoglobin oxygenation and hemoglobin content were measured by DRS. RESULTS: Capillary perfusion in mild pancreatitis initially increased significantly at 30 minutes to 155% +/- 38% of baseline values but returned to baseline within 3 hours. Hemoglobin content and oxygen saturation remained stable. In moderate and severe pancreatitis capillary perfusion significantly decreased versus the control group to 12% +/- 6% and 6% (range, 0% to 14%) of baseline values, respectively, at 6 hours. Oxygen saturation decreased significantly in moderate pancreatitis from 48.5% +/- 2.3% to 41.6% +/- 3.5% (p < 0.05) and in severe pancreatitis from 47.2% +/- 1.5% to 38.9% +/- 0.5% (p < 0.05), whereas hemoglobin content did not change. CONCLUSIONS: We conclude that (1) IVM and DRS provide both unique and complementary data on tissue perfusion of the pancreas, (2) that moderate and severe experimental pancreatitis are accompanied by progressive tissue ischemia, and (3) that significant stasis (decreased perfusion) and decreased oxygen saturation occur whereas generalized vasoconstriction (decreased hemoglobin levels) was not found. In contrast, mild experimental pancreatitis was accompanied by initial hyperperfusion and normal oxygen delivery was maintained.

Interstitial protease activation is the central event in progression to necrotizing pancreatitis.

BACKGROUND: Although intracellular protease activation is thought to be an early event in acute pancreatitis, factors determining progression from edematous to necrotizing pancreatitis are largely unknown. With enterokinase as a probe and an immunoassay quantifying free trypsinogen activation peptides (TAP), we sought evidence for the presence of interstitial trypsinogen in edematous pancreatitis and documented the effects of its ectopic activation. METHODS: Edematous pancreatitis in the rat was induced by supramaximal stimulation with cerulein (5 micrograms/kg/hr) and coupled with enterokinase infused into the pancreatic duct at 30 mm Hg. Blue dextran infusion at this pressure corroborated interstitial delivery. Rats with no stimulation, maximal physiologic stimulation (0.25 microgram/kg/hr of cerulein), or intraductal saline infusion served as controls. TAP levels measured by enzyme-linked immunosorbent assay, 6-hour survival, and histopathology were used as end points. RESULTS: Intraductal enterokinase infusion alone or in combination with maximal physiologic stimulation generated only slight increases in TAP level and no or minimal pancreatic injury. In contrast, enterokinase superimposed on edematous pancreatitis (supramaximal cerulein stimulation) produced fulminant pancreatitis and rapid death of all animals within 6 hours. Pancreatic histopathology showed severe intrapancreatic hemorrhage, acinar inflammation, and necrosis. TAP levels were significantly higher in plasma (p = 0.02), urine (p = 0.05), and ascites (p < 0.001) when compared with all other groups. CONCLUSIONS: In edematous pancreatitis a large pool of trypsinogen accumulates in the interstitial space. Activation of these proenzymes leads to catastrophic consequences and may underlie progression from mild to necrotizing pancreatitis.

Evidence for extraluminal trypsinogen activation in three different models of acute pancreatitis.

BACKGROUND: Inappropriate extraluminal activation of trypsin is assumed to play a part in the pathogenesis of acute pancreatitis (AP), but proof has been elusive because active trypsin is transient and difficult to measure. We have previously shown increased levels of trypsinogen activation peptides (TAP), a direct measure of trypsin activation, to correlate with severity of AP, tissue necrosis, and survival in a rodent model induced by cerulein hyperstimulation and bile salt infusion. The present study seeks to show that increased trypsinogen activation also characterizes three other models of experimental AP in rodents to give credence to the generality of the phenomenon and to its potential relevance to human AP. METHODS: Experimental AP was induced in mice by a choline-deficient diet supplemented with ethionine and in rats by creation of a closed duodenal loop or by ligation of the biliopancreatic duct plus physiologic stimulation. TAP were quantified by an immunoassay in tissue and plasma at various time points after onset of AP. RESULTS: In the group with choline-deficient diet supplemented with ethionine a significant increase in tissue and plasma TAP was found at 48 and 72 hours, respectively. In the group with closed duodenal loop significant TAP elevations were found in plasma as early as 6 hours and in the group with ligation of the biliopancreatic duct plus physiologic stimulation at 24 hours. CONCLUSIONS: These experiments provide further evidence that extraluminal protease activation is a pathophysiologic event common to the evolution of various models of experimental acute pancreatitis and therefore increase the likelihood that this phenomenon is important in the human disease as well.

A rat model of pancreatic ductal adenocarcinoma: targeting chemical carcinogens.

BACKGROUND: Current experimental models of pancreatic cancer either fail to reproduce the ductal phenotype or cause simultaneous cancers in other organs also. To develop an animal of pancreatic cancer that accurately mimics the human condition, we restricted carcinogenic exposure to the pancreas and specifically targeted ductal epithelial cells. Three different carcinogens were either implanted directly into the pancreas or infused into the pancreatic duct, with or without near-total pancreatectomy (as a means of inducing pancreatic ductal cell proliferation). METHODS: Groups of male Sprague-Dawley rats were exposed to varying doses of dimethylbenzanthracine (DMBA), methynitronitrosoguanidine, or ethylnitronitrosoguanidine either through direct implantation into the pancreas or infusion into the pancreatic duct. Near-total pancreatectomy was added in all groups except two DMBA implantation groups. Surviving rats were killed at 3, 6, 9, or 12 months, and the pancreata were evaluated histologically. RESULTS: All three carcinogens caused pancreatic inflammation, ductal hyperplasia, atypia, and dysplasia beginning by 3 months and becoming more prominent at later time points. Only DMBA caused frequent invasive pancreatic ductal adenocarcinoma, which was first evident by 6 months. The prevalence of pancreatic cancer among DMBA-treated rats evaluated after 10 months was 39% (19 of 49). The addition of pancreatic resection did not enhance pancreatic cancer development. CONCLUSIONS: Of the strategies tested, only direct implantation of DMBA into the rat pancreas frequently produces pancreatic cancer histologically similar to human ductal adenocarcinoma. The development of hyperplastic, atypical, and dysplastic changes preceding and accompanying carcinomas suggests that these lesions are preneoplastic. This model recapitulates the progression from normal to neoplastic epithelium and is likely to be useful for the study of morphologic and molecular mechanisms underlying the early stages of pancreatic carcinogenesis and for the investigation of novel diagnostic and therapeutic techniques.

Differing roles of nitric oxide in the pathogenesis of acute edematous versus necrotizing pancreatitis.

BACKGROUND: Microcirculatory changes and leukocyte-endothelial interaction are both central to the pathogenesis of acute pancreatitis. We studied the effects of nitric oxide (NO) donors (intravenous or inhaled) and NO inhibitors, which affect each of these processes, on markers of experimental mild (edematous) and severe (necrotizing) pancreatitis in rats. METHODS: Mild pancreatitis was induced with intravenous cerulein (n = 100) and severe pancreatitis with intravenous cerulein and intraductal glycodeoxycholic acid (n = 100). Each group was randomly divided into five equal treatment subgroups: control, NO-synthase substrate L-arginine, NO donor sodium nitroprusside, NO-synthase inhibitor N-nitro-L-arginine methyl ester (L-NAME), and NO-inhalation. After 6 hours edema was measured by a wet/dry weight ratio, and pancreatic injury was quantified by tissue levels of trypsinogen activation peptides (TAPs) and by histologic analysis of inflammation and necrosis. RESULTS: In mild pancreatitis (1) both NO donors reduced edema formation (p < 0.001) and also reduced intrapancreatic TAPs (p < 0.03); (2) L-NAME significantly increased tissue TAPs (p < 0.03); and (3) inhaled NO had no effect. In severe pancreatitis (1) both intravenous NO donors reduced edema formation (p < 0.005) and both markedly reduced intrapancreatic TAPs (p < 0.001); (2) L-NAME did not further increase the already high tissue TAPs; and (3) inhaled NO decreased tissue TAPs (p = 0.01). Evaluation of inflammation and necrosis by histologic scoring confirmed the reduction of pancreatic injury by NO donors and worsening with NO-synthase inhibitor. CONCLUSIONS: NO donors have a beneficial effect on edema formation in acute pancreatitis but confer more important protection against ectopic trypsinogen activation, which correlates with mortality, inflammation, and necrosis. Although direct microcirculatory action is likely, the salutary effect of inhaled NO in severe pancreatitis may suggest indirect action on circulating leukocytes, which are thought to potentiate tissue injury.

Analysis of K-ras oncogene mutations in chronic pancreatitis with ductal hyperplasia.

BACKGROUND: K-ras oncogene mutations have been identified in up to 95% of pancreatic cancers, implying their critical role in their molecular pathogenesis. However, the earliest stage in which K-ras mutations can be detected in potential precursor lesions of pancreatic cancer remains unclear. This study evaluates pancreatic ductal hyperplasia in the setting of chronic pancreatitis, which predisposes to pancreatic cancer development, for K-ras codon 12 and 13 mutations. METHODS: Paraffin-embedded surgical specimens from 42 patients with chronic pancreatitis were examined microscopically for the presence of ductal hyperplasia. Both hyperplastic and nonhyperplastic ducts were microdissected from the specimens that contained hyperplasia (11 of 42). Four of the remaining specimens without hyperplasia served as controls. Genomic DNA was extracted, and polymerase chain reaction and amplification of the K-ras oncogene was performed. Polymerase chain reaction products were evaluated by means of hybridization to mutant specific oligonucleotide probes and by means of automated DNA sequencing. RESULTS: K-ras codon 12 mutations representing glycine to valine substitutions were present in 2 of (18%) 11 patients with ductal hyperplasia. No mutations were found in the controls without ductal hyperplasia. CONCLUSIONS: Our study supports the premise that K-ras mutations develop in a subset of chronic pancreatitis associated hyperplasia and provides a genetic basis for the potential progression of chronic pancreatitis to pancreatic cancer.

Reflectance spectroscopy of pancreatic microcirculation.

A technique employing diffuse reflectance spectroscopy (DRS) is described to assess and mirror dynamic changes of pancreatic tissue perfusion. An especially designed reflectance spectrophotometer was initially used to derive the quantitative relation between hemoglobin concentration ([Hb]) and reflectance measurements in vitro. Over a wide range of scattering related to the medium in which the measurements were made (scattering coefficient: 6.5-13 cm-1), a close, direct correlation existed with a slope of 0.376 +/- 0.012. In Sprague-Dawley rats under general anesthesia, the pancreas was isolated in situ and perfused with graded infusions of hemoglobin solutions. A correlation, comparable to the in vitro setting, was found between a [Hb] of 0 and 14 g/dl in the perfusate with slopes of 0.0037 and 0.0035. Changes in perfusion induced by adrenergic drugs produced changes in hemoglobin oxygen saturation and [Hb] that correspond with measured alterations of systemic arterial pressure and aortic blood flow. We conclude that diffuse reflectance spectroscopy reliably provides data on intrapancreatic hemoglobin oxygen saturation and [Hb] that can be a valuable tool for minimally invasive on-line evaluation of these aspects of pancreatic perfusion in the rat. This newly designed device is superior to previously used ones in that it analyzes the entire spectrum and therefore can account for changes in scattering that are very likely to occur with pathophysiological alterations such as edema formation.

Patient satisfaction following laparoscopic and open antireflux surgery.

OBJECTIVE: To compare laparoscopic (LNF) with open Nissen fundoplication (ONF) in terms of hospital charges, efficacy, and patient satisfaction. DESIGN: A prospective, nonrandomized study with a median follow-up of 370 days. SETTING: Two tertiary care university hospitals. PATIENTS: Eighty-six patients with complications of gastroesophageal reflux who had not had previous antireflux surgery were studied. Patients chose ONF or LNF following discussion with the surgeon; 12 underwent ONF and 74 underwent LNF, of whom eight required conversion to laparotomy. MAIN OUTCOME MEASURES: Hospital charges, disability, satisfaction, and side effects of fundoplication. RESULTS: Patients were demographically similar. Total charges (mean +/- SD) for LNF ($11,673 +/- $4723) were significantly less than for ONF ($18,394 +/- $17,264). Patients who underwent LNF returned to work sooner (10 +/- 3 days) than those who underwent ONF (28 +/- 1 days). Bloating, dysphagia, and recurrent heartburn occurred with equal frequency in both groups. Recurrent reflex occurred in four of 74 LNF patients and one of 12 ONF patients. Overall satisfaction scores were similar, irrespective of operative technique (LNF, 3.35 +/- 0.87; ONF, 3.50 +/- 0.94. CONCLUSIONS: Laparoscopic Nissen fundoplication is as effective as ONF in the treatment of complications of gastroesophageal reflux disease and appears to cost less and lead to faster recovery from surgery, but does not result in higher patient satisfaction than ONF. The most important factor in patient satisfaction is the abolition of preoperative symptoms rather than the type of operation.