PubMed Health⌕ Search

Biomedical subjects

Amitabh Chak

Publications and source records attributed to Amitabh Chak.

At least 37 records · Page 2Linked to original sources
PubMed2006

A primer on natural orifice transluminal endoscopic surgery: building a new paradigm.

Access to the abdominal cavity is required for diagnostic and therapeutic endeavors for a variety of medical and surgical diseases. Historically, abdominal access has required a formal laparotomy to provide adequate exposure. Natural orifice transluminal endoscopic surgery (NOTES) is an emerging experimental alternative to conventional surgery that eliminates abdominal incisions and incision-related complications by combining endoscopic and laparoscopic techniques to diagnose and treat abdominal pathology. During NOTES, commercially available flexible video endoscopes are used to create a controlled transvisceral incision via natural orifice access to enter the peritoneal cavity. Common incision-related complications such as wound infections, incisional hernias, postoperative pain, aesthetic disdain, and adhesions could be minimized or eliminated by NOTES. NOTES has evolved from more than 2 centuries of technological innovations and continued growth in the field of surgical endoscopy. Innovative surgical endoscopists have slowly developed means to surpass the constraints of the gastrointestinal lumen by using a flexible endoscope. The future of surgical endoscopy may be the shared entity of NOTES, which further integrates endoscopy, gastroenterology, and minimally invasive and general surgery. Although the promise of NOTES is electrifying to surgeons and endoscopists, several key issues need to be characterized prior to the incorporation of NOTES into routine practice. This article reviews the status, contemporary body of literature, limitations, and potential future implications accompanying the development of NOTES.

Abdominal Cavity↗
PubMed2006

Sedationless upper endoscopy.

The use of sedation with peroral passage of conventionally sized endoscopes for upper endoscopy is the standard practice for most endoscopists in the United States. The administration of sedatives requires time-consuming and resource-intensive patient monitoring, has substantial cost, and can produce side effects and rare complications. Ultra-thin videoendoscopes (outer diameter less than 6 mm) have been developed, can easily be passed transorally or transnasally without sedation, and have been shown to be well tolerated and accurate. Unsedated upper endoscopy can provide an efficient, cost-effective alternative to standard endoscopy, should be useful for endoscopic screening, and can be offered as an option to conventional sedated examination.

Endoscopes, Gastrointestinal↗
PubMed2006

Sedationless upper endoscopy.

The use of sedation with peroral passage of conventionally sized endoscopes for upper endoscopy is the standard practice for most endoscopists in the United States. The administration of sedatives requires time-consuming and resource-intensive patient monitoring, has substantial cost, and can produce side effects and rare complications. Ultra-thin videoendoscopes (outer diameter less than 6 mm) have been developed, can easily be passed transorally or transnasally without sedation, and have been shown to be well tolerated and accurate. Unsedated upper endoscopy can provide an efficient, cost-effective alternative to standard endoscopy, should be useful for endoscopic screening, and can be offered as an option to conventional sedated examination.

Endoscopes, Gastrointestinal↗
PubMed2005

Increased risk of squamous cell esophageal cancer after adjuvant radiation therapy for primary breast cancer.

Prior studies have demonstrated that adjuvant radiation therapy following mastectomy for breast cancer increases the risk of second primary esophageal cancer after 10 years, but the risk following breast-conserving surgery (lumpectomy) has yet to be determined. The authors used 1973-2000 data from the population-based Surveillance, Epidemiology, and End Results Program and estimated relative risks of 2.83 (95% confidence interval: 1.35, 5.92) and 2.17 (95% confidence interval: 1.67, 4.02) for squamous cell esophageal cancer at 5-9 and > or =10 years, respectively, following postmastectomy radiation therapy. This increase was mainly due to tumors located in the upper and middle thirds of the esophagus. No significant increase in risk was found for adenocarcinoma following mastectomy or for any type of esophageal cancer following lumpectomy. In summary, postmastectomy radiation therapy moderately increases the risk of squamous cell esophageal cancer starting 5 years after exposure, which persists after 10 years, with no increase in the risk of adenocarcinoma. This finding appears to be a function of the portals used for postmastectomy radiation therapy, which do not expose the lowest third of the esophagus, where adenocarcinomas commonly arise.

Adenocarcinoma↗
PubMed2005

The polyp detection rate of colonoscopy: a national study of Medicare beneficiaries.

National-level data on the proportion of colonoscopies in routine practice that result in polyp detection are limited. Our goal was to determine the diagnostic yield of colonoscopy among population subgroups. We reviewed Medicare claims data for all fee-for-service beneficiaries 65 years or older who underwent colonoscopy in 1999. With the use of diagnosis and procedure codes, the proportion of procedures with polyps was estimated. Three different criteria for polyp detection were used. Approximately 1.8 million colonoscopy procedures were identified. Depending on the specific criteria used, 23.9% to 35.7% of examinations noted polyps. The detection rate was highest in younger patients, men, and whites. The apparent yield of colonoscopy in terms of polyp detection is at least 24%. These data may be informative in predicting resource allocation for therapeutic procedures associated with colonoscopy. Future studies should determine the use and yield of serial colonoscopies for polyp surveillance.

Age Factors↗
PubMed2005

In vivo optical coherence tomography imaging of the pancreatic and biliary ductal system.

BACKGROUND: In vivo optical coherence tomography (OCT) imaging has not yet been applied to the pancreatic ductal system. The aim of this study was to obtain in vivo OCT images of dog pancreatic and biliary ducts, and to correlate the images with histology. METHODS: Images of dog pancreatic and biliary ducts were obtained by using an in vivo OCT probe introduced through the respective papillary orifices. Each duct was imaged in multiple locations, and the site of imaging was marked with injected India ink. After imaging, the dogs were euthanized, and the pancreaticobiliary system was harvested. Histologic cross sections were correlated with in vivo OCT images by measuring the structures seen on in vivo OCT images and correlating them with structures seen on corresponding histology slides that contained India ink. OBSERVATIONS: Eighteen pairs of in vivo OCT images and histology slides from the bile duct and the pancreatic duct were obtained from 5 dogs. The entire duct wall could be visualized. A low reflective in vivo OCT layer corresponding to the epithelium could be discerned on many images. The bile duct showed a more complex architecture and had greater variations within the reflective OCT layers, possibly because of greater cellularity within the lamina propria. Nuclei within cells could not be identified, and structures adjacent to the ducts could not be imaged. CONCLUSIONS: In vivo OCT is capable of imaging the pancreaticobiliary ductal system and of identifying the epithelial layer. Because of limited depth of imaging (320-845 micron), OCT is unlikely to serve the purpose of tumor staging.

Animals↗
PubMed2005

Accuracy of endoscopic optical coherence tomography in the detection of dysplasia in Barrett's esophagus: a prospective, double-blinded study.

BACKGROUND: Endoscopic optical coherence tomography (EOCT) is a high-resolution, cross-sectional tissue-imaging technique that provides microscopic morphologic information. EOCT should detect dysplasia in Barrett's epithelium, but this has not been established in a prospective blinded study. This study evaluated the accuracy of EOCT for the diagnosis and the exclusion of dysplasia in patients with Barrett's esophagus. METHODS: A 2.4-mm diameter EOCT probe was modified for use with a cap-fitted, two-channel endoscope. Pairs of EOCT image streams and jumbo biopsy specimens were obtained. Endoscopy/EOCT procedures were performed by 4 endoscopists who separately reviewed the EOCT digital images for the absence or the presence of dysplasia (low grade, high grade, or cancer) for each biopsy specimen obtained. The endoscopists were blinded to the interpretation of the pathology. An experienced pathologist blinded to the endoscopic/EOCT findings evaluated each biopsy for the absence or the presence of dysplasia. The setting of the study was a major academic medical center. Adult patients with documented Barrett's esophagus greater than 2 cm were included in the study. The main outcome measurement was the accuracy of EOCT in the detection of dysplasia in patients with Barrett's esophagus. RESULTS: A total of 314 usable EOCT image stream/biopsy pairs were obtained in 33 patients. By using histology as the standard, the performance of EOCT was sensitivity, 68%; specificity, 82%; positive predictive value, 53%; negative predictive value, 89%; and diagnostic accuracy, 78%. Diagnostic accuracy for the 4 endoscopists ranged from 56% to 98%. Limitations of the study were the variability in endoscopists' accuracy rates, difficulty in real-time interpretation, and the need for refined criteria of dysplasia by EOCT imaging. CONCLUSIONS: The current EOCT system has an accuracy of 78% for the detection of dysplasia in patients with Barrett's esophagus. EOCT could be used to target biopsies to areas of Barrett's epithelium with a higher probability for the presence of dysplasia. However, further modifications, including increased resolution and identification of further potential OCT characteristics of dysplasia, are needed before EOCT can be used clinically.

Adult↗
PubMed2005

The changing landscape of practice patterns regarding unsedated endoscopy and propofol use: a national Web survey.

BACKGROUND: Lower reimbursements for endoscopic procedures and increasing demand for screening endoscopy over the past decade have spurred efforts to increase efficiency in the performance of endoscopic procedures. Two dichotomous approaches have emerged: (1) unsedated endoscopy and (2) propofol sedation. The aim was to determine national practice patterns of unsedated endoscopy and propofol sedation, and to assess endoscopists' attitudes toward unsedated screening with an electronic survey. METHODS: A short survey was developed and then was converted to a Web-based format. All national members of the American Society for Gastrointestinal Endoscopy (ASGE) were invited via electronic mail (e-mail) to participate. Survey data were collected electronically. RESULTS: Two e-mails elicited responses to the Web survey from 18% (724) of national ASGE members contacted, within 2 weeks. Of the respondents, 45% do not routinely offer unsedated EGD and colonoscopy, and only 15% of those respondents plan to incorporate unsedated endoscopy into their practice in the next year. Of the 55% who currently perform unsedated endoscopy, 85% do no more than 25 unsedated procedures per year. Lack of patient acceptance was the most common reason cited for not offering unsedated endoscopy. Most endoscopists felt that the availability of unsedated esophagoscopy or colonoscopy would not significantly increase screening for Barrett's esophagus or colonic polyps/colorectal cancer, respectively. Routine use of propofol sedation for EGD, colonoscopy, and ERCP/EUS was reported by 19%, 22%, and 19%, respectively. Community practitioners were more likely to use propofol than those at academic centers (p < 0.0002 for all). Of those not currently using propofol, 43% plan to incorporate it into their practice within the next year. Over 70% of respondents would themselves choose to be sedated for routine endoscopic procedures. CONCLUSIONS: Electronic surveys allow for rapid distribution and data collection but suffer from a limited response rate. The survey suggests that unsedated endoscopy has limited acceptance in the United States, and, without a major intervention that affects endoscopists' attitudes, its use is not likely to increase significantly. Unsedated endoscopy will not have a great impact on endoscopic screening. In contrast, propofol sedation has already gained acceptance in the community, and the routine use of propofol in endoscopy units will likely increase in the future.

Anesthetics, Intravenous↗
PubMed2005

Endoscopic treatment of high-grade dysplasia and early cancer in Barrett's oesophagus.

Barrett's oesophagus is the premalignant precursor of oesophageal adenocarcinoma. Non-dysplastic metaplasia can progress to low-grade dysplasia, high-grade dysplasia, and finally to invasive cancer. Although the frequency of adenocarcinoma in patients with Barrett's oesophagus is low, surveillance is justified because the outcome of adenocarcinoma is poor. Oesophagectomy remains the standard treatment for patients with high-grade dysplasia and superficial carcinoma. However, it has been associated with substantial morbidity and mortality and some patients are judged unfit for surgery. In this review, the present status of less invasive procedures is discussed. Endotherapy preserves the integrity of the oesophagus and allows a better quality of life to patients at low risk of developing lymph-node metastases. Opposition to endoscopic treatment is based mainly on the identification of undetected foci of cancer and high-grade dysplasia in oesophagectomy samples. The current ablative techniques used are photodynamic therapy, argon plasma coagulation, laser treatment, and endoscopic mucosal resection.

Adenocarcinoma↗
PubMed2005

The yield of bleeding scans in acute lower gastrointestinal hemorrhage.

GOALS/BACKGROUND: Previous studies have demonstrated low yield and conflicting results as to the ability of technetium-99m labeled red blood cell (TRBC) scintigraphy to accurately localize the site of bleeding in acute lower gastrointestinal hemorrhage. Our objective was to evaluate the accuracy of TRBC scintigraphy in clinical day-to-day practice at our institution and to determine predictors of a positive test. METHODS: A retrospective medical records review of all patients who underwent TRBC scintigraphy over a 5-year period was conducted at a single academic medical center. The site of bleeding found on TRBC scintigraphy was correlated with the endoscopic, angiographic, surgical, and pathologic findings in each patient. RESULTS: A total of 127 scans were performed in 115 patients. Forty-nine scans were positive (39%) and 78 were negative (61%). Forty-two patients had further evaluation after a positive scan, and the bleeding site was confirmed to be accurate in 20 of 42 patients (48%). A contradictory bleeding site was found in 5 of 49 positive scans (10%). Patients transfused greater than 2 units of packed red blood cells within 24 hours preceding the TRBC scan were twice as likely to have a positive scan (64%) than those transfused 2 units or less (32%) (P = 0.002). Multivariate analysis demonstrated that the number of units of blood transfused within 24 hours prior to the TRBC scan and the lowest recorded hematocrit were significantly different between patients with positive and negative scans. There was no difference in the rate of endoscopy between patients with a positive or negative scan result. CONCLUSIONS: TRBC scintigraphy has a relatively low yield in the evaluation of acute lower gastrointestinal bleeding. Objective selection criteria such as number of units of packed red blood cells transfused prior to obtaining the scan may increase the overall yield.

Acute Disease↗
PubMed2004

Association of ampullary and colorectal malignancies.

BACKGROUND: Because of the similarities in terms of carcinogenesis and natural history between cancer of the ampulla of Vater and colorectal cancer, the authors examined whether ampullary and colorectal malignancies occur in the same individuals at increased rates. METHODS: We used data from the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute for the period from January 1973 through December 1999. Person-years of follow-up for patients with ampullary (or colorectal) cancer were used to calculate the expected number of cases of colorectal (or ampullary) cancer as a second primary malignancy. Standardized incidence ratios (SIRs) with 95% confidence intervals (CIs) were calculated using Byar limits and assuming a Poisson distribution. RESULTS: The authors identified 2043 white patients with ampullary cancer who were included in the SEER registry between 1973 and 1999. Over an aggregate 5674 person-years of follow-up, 30 patients, compared with an expected 14, developed colorectal cancer, yielding an overall SIR of 2.14 (95% CI, 1.45-3.06). Similarly, 57 of 262,066 white patients with colorectal cancer developed ampullary cancer over an aggregate 1,270,255 person-years of follow-up, yielding an SIR of 2.18 (95% CI, 1.69-2.85). CONCLUSIONS: Patients with ampullary cancer are at increased risk for a second primary colorectal malignancy, and patients with colorectal cancer are at increased risk for a second primary ampullary malignancy. These findings suggest that ampullary and colorectal malignancies share common environmental and/or genetic risk factors.

Age Distribution↗
PubMed2004

Endoscopic management of adenoma of the major duodenal papilla.

BACKGROUND: It is well established that adenoma of the major duodenal papilla has a potential for malignant transformation. Standard treatment has been surgical (duodenotomy/local resection, pancreaticoduodenectomy). Endoscopic management is described, but there is no established consensus regarding the approach to papillectomy or the need for surveillance. This study describes endoscopic management and long-term follow-up of papillary tumors by 4 groups of expert pancreaticobiliary endoscopists. METHODS: Consecutive patients with papillary tumors referred to 4 pancreaticobiliary endoscopy centers for evaluation for endoscopic papillectomy were reviewed. For each patient, an extensive questionnaire was completed, which included 19 preoperative and 15 postoperative data points. A total of 103 patients (53 women, 50 men, age range 24-93) who underwent attempted endoscopic resection were included. Of these, 72 had sporadic adenoma, and the remaining patients had familial adenomatous polyposis, including Gardner's variant. Presenting symptoms were jaundice/cholangitis/pain (n=59), pancreatitis (n=18), and bleeding (n=12). Twenty-six patients were asymptomatic. RESULTS: Endoscopic treatment was successful, long term, in 83 patients (80%) and failed (initial failure or recurrent tumor) in 20 (20%) patients. Success was significantly associated with older age (54.7 [16.6] vs. 46.6 [21.7] years; p=0.08) and smaller lesions (21.1 [8.3] vs. 29.7 [7.2] mm; p<0.0001). Success rate was higher for sporadic lesions compared with genetically determined lesions (63 of 72 [86%] vs. 20 of 31 [67%]; p=0.02). There were 10 initial failures, which was more common for sporadic lesions (7 of 10). The overall success rate for papillectomy was similar in patients who had adjuvant thermal ablation (81%) compared with those who did not (78%). However, recurrence (n=10) was more common in the former group (9 of 10, [90%]; p=0.22). Complications (n=10) included acute pancreatitis (n=5), bleeding (n=2), and late papillary stenosis (n=3). Acute pancreatitis was more common in patients who did not have pancreatic duct stents placed (17% vs. 3.3%). Papillary stenosis was more frequent without short-term pancreatic duct stent placement (15.4% vs. 1.1%), although the difference was not statistically significant, because this complication was infrequent. CONCLUSIONS: Endoscopic treatment of papillary adenoma in selected patients appears to be highly successful. The majority can undergo complete resection after ERCP. In expert hands, complications are infrequent and may be avoided by routine placement of a pancreatic duct stent.

Adenoma↗
PubMed2004

Sphincter of Oddi manometry does not predispose to post-ERCP acute pancreatitis.

BACKGROUND: Sphincter of Oddi manometry is helpful in selecting patients with sphincter of Oddi dysfunction who will respond to sphincterotomy. However, studies have shown that sphincter of Oddi manometry is associated with a high risk of post-procedure pancreatitis. The primary objective of this study was to evaluate the safety of sphincter of Oddi manometry in patients with sphincter of 2Oddi dysfunction. The secondary objective was to determine the risk factors for post-ERCP pancreatitis in patients with sphincter of Oddi dysfunction. METHODS: Data were collected retrospectively for 268 patients who had elective ERCP performed at 3 tertiary care medical centers between 1996 and 2000. Consecutive patients with suspected sphincter of Oddi dysfunction formed the case group; the control group consisted of patients with bile duct stone. The case group was further subclassified into group A, patients who underwent sphincter of Oddi manometry followed by immediate ERCP, and group B, patients who had ERCP without manometry. The rate of post-ERCP acute pancreatitis was compared between case and control groups. RESULTS: Twenty-seven percent of patients in the case group with suspected sphincter of Oddi dysfunction developed acute pancreatitis compared with 3.2% of patients in the control group with bile duct stone (p<0.001). There was no significant difference in the rate of acute pancreatitis in patients with sphincter of Oddi dysfunction who underwent sphincter of Oddi manometry and ERCP compared with patients with sphincter of Oddi dysfunction who had ERCP without sphincter of Oddi manometry (odds ratio 0.72: 95% CI[0.08, 9.2]). Multivariable logistic regression analysis showed that biliary sphincterotomy (p=0.006) and pancreatography (p=0.03) were independent predictors of acute pancreatitis. CONCLUSIONS: Patients with suspected sphincter of Oddi dysfunction are at higher risk of post-ERCP acute pancreatitis. Sphincter of Oddi manometry by itself does not appear to predispose to this complication.

Acute Disease↗
PubMed2004

Acute pancreatitis after EUS-guided FNA of solid pancreatic masses: a pooled analysis from EUS centers in the United States.

BACKGROUND: The aim of this study was to determine the frequency and the severity of pancreatitis after EUS-guided FNA of solid pancreatic masses. A survey of centers that offer training in EUS in the United States was conducted. METHODS: A list of centers in which training in EUS is offered was obtained from the Web site of the American Society for Gastrointestinal Endoscopy. Designated program directors were contacted via e-mail. The information requested included the number of EUS-guided FNA procedures performed for solid pancreatic masses, the number of cases of post-procedure pancreatitis, and the method for tracking complications. For each episode of pancreatitis, technical details were obtained about the procedure, including the location of the mass, the type of fine needle used, the number of needle passes, and the nature of the lesion. RESULTS: Nineteen of the 27 programs contacted returned the questionnaire (70%). In total, 4909 EUS-guided FNAs of solid pancreatic masses were performed in these 19 centers over a mean of 4 years (range 11 months to 9 years). Pancreatitis occurred after 14 (0.29%): 95% CI[0.16, 0.48] procedures. At two centers in which data on complications were prospectively collected, the frequency of acute pancreatitis was 0.64%, suggesting that the frequency of pancreatitis in the retrospective cohort (0.26%) was under-reported (p=0.22). The odds that cases of pancreatitis would be reported were 2.45 greater for the prospective compared with the retrospective cohort (95% CI[0.55, 10.98]). The median duration of hospitalization for treatment of pancreatitis was 3 days (range 1-21 days). The pancreatitis was classified as mild in 10 cases, moderate in 3, and severe in one; one death (proximate cause, pulmonary embolism) occurred after the development of pancreatitis in a patient with multiple comorbid conditions. CONCLUSIONS: EUS-guided FNA of solid pancreatic masses is infrequently associated with acute pancreatitis. The procedure appears to be safe when performed by experienced endosonographers. The frequency of post EUS-guided FNA pancreatitis may be underestimated by retrospective analysis.

Acute Disease↗
PubMed2004

Does prophylactic pancreatic stent placement reduce the risk of post-ERCP acute pancreatitis? A meta-analysis of controlled trials.

BACKGROUND: Impaired drainage of the pancreatic duct is one of the possible triggers for post-ERCP acute pancreatitis. The aim of this meta-analysis was to determine whether temporary stent placement across the main pancreatic-duct orifice lowers the frequency of post-ERCP acute pancreatitis in patients at high risk for this complication. METHODS: Two reviewers systematically identified prospective studies that (1) compared the risk of post-ERCP acute pancreatitis in patients with pancreatic stent placement vs. no stent placement and (2) included patients at high risk of developing this complication. Studies were assessed for methodologic quality and variations in execution and design. Frequency and severity of post-ERCP acute pancreatitis were the primary outcomes evaluated. RESULTS: Five trials involving 481 patients were selected. Of the 481, 55 (11.4%) patients developed pancreatitis after ERCP. Patients in the no stent group had 3-fold higher odds of developing pancreatitis compared with the stent group (15.5% vs. 5.8%; OR 3.2: 95% CI[1.6, 6.4]). Number needed to treat analysis showed that one in every 10 patients (95% CI[6,18]) could be expected to benefit from pancreatic-duct stent placement. CONCLUSIONS: Prophylactic temporary stent placement across the main pancreatic-duct orifice reduces the risk of post-ERCP acute pancreatitis in patients at risk for developing this complication.

Acute Disease↗