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Background: Use of chemoprophylaxis for prevention of venous thromboembolism (VTE) after bariatric surgery is a generally accepted principle; however, the optimal strategy in terms of medication type and pre- and postoperative dosing is uncertain. In our healthcare system, four hospitals performed bariatric surgery and utilized differing protocols for VTE prophylaxis. The analysis sought to evaluate the association of differing prophylaxis strategies on bleeding and VTE occurrence., Methods: Adult patients who underwent laparoscopic sleeve gastrectomy (SG) or Roux-en-Y gastric bypass (RYGB) from 2018 to 2021 at four hospitals were studied. Patients were grouped by whether or not they received preoperative chemoprophylaxis. The primary outcome was postoperative bleeding, defined as requiring a blood transfusion or reoperation for bleeding within 30 days. Bivariate analyses were performed with Chi-square and Wilcoxon Rank tests where applicable. Multivariate logistic regression was performed for the outcome of postoperative bleeding., Results: A total of 2145 bariatric surgeries were evaluated (33.6% RYGB, 66.4% SG). Among 1712 patients who underwent surgery at Hospitals A, B, and C, 93.1% received preoperative VTE prophylaxis, compared with 1 patient (0.1%) among 433 patients operated on at Hospital D. Postoperative bleeding occurred more frequently in patients who received preoperative VTE prophylaxis versus those who did not (3.7% vs 1.1%; p < 0.01). After multivariable regression analysis, only RYGB (OR 3.59; p < 0.01) and preoperative VTE prophylaxis (OR 3.54; p = 0.02) were significantly associated with postoperative bleeding. Rates of VTE for patients receiving preoperative VTE prophylaxis or no prophylaxis were not significantly different (0.6% vs. 0.2%; p = 0.26)., Discussion: Preoperative VTE prophylaxis prior to bariatric surgery was associated with postoperative bleeding without differences in VTE occurrence. These results call into question the routine use of VTE chemoprophylaxis for all patients undergoing bariatric surgery and favor selective usage., Competing Interests: Declaration. Disclosure: Joseph E. Sanchez, Audra Reiter, Catherine S. Valukas, Whitney N Jones, Dominic J Vitello, Joanne Prinz, Yan Li, Eric S. Hungness, and Ezra N. Teitelbaum have no conflicts of interest or financial ties to disclose., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Objective: The primary objective was to determine the prognostic significance of circulating tumor DNA (ctDNA) in patients receiving neoadjuvant chemotherapy (NAC) for localized pancreatic ductal adenocarcinoma (PDAC) using digital droplet polymerase chain reaction (ddPCR)., Summary and Background Data: Increasingly, ctDNA is being used for clinical decision-making in a variety of solid malignancies. However, the detection and prognostic value of KRAS ctDNA as assessed by ddPCR during NAC has yet to be characterized., Methods: Patients with localized PDAC eligible to receive NAC were prospectively enrolled. Peripheral blood samples were obtained at diagnosis, after NAC, and after resection and analyzed for ctDNA using ddPCR. Log-rank tests and Cox proportional hazards model were used to assess for association with OS., Results: 84 patients were included in the analysis. Mutant KRAS ctDNA was detected in 49.3% of patients at diagnosis, 69.6% of patients after NAC, and 69.7% of patients after resection, respectively. There were 15 (17.9%) patients that cleared mutational ctDNA over the course of treatment. Clearance of ctDNA during NAC was associated with improved overall survival (OS) (18.4 mo. vs NR, P<0.05). Detection of mutant KRAS G12V after NAC and resection was associated with shorter OS (18.0 versus NR months, P<0.031). Detection of the KRAS G12V mutation after resection was associated with reduced OS (aHR 36.75, 95% CI 2.93-461.38)., Conclusions: Throughout treatment, KRAS ctDNA is detectable by ddPCR in patients with localized PDAC treated with NAC. Detection of mutant KRAS G12V after resection was associated with reduced OS., Competing Interests: Conflicts of interest: The authors have no pertinent conflicts of interest to disclose., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Purpose: The treatment of gastric adenocarcinoma (GA) continues to evolve. While neoadjuvant chemotherapy (NAC) has demonstrated emerging benefit, the optimal treatment regimen, and sequence remain to be firmly established., Methods: Patients with nonmetastatic GA who underwent resection were identified within the 2020 National Cancer Database. Patients were compared between the mutually exclusive treatment groups of NAC, neoadjuvant chemoradiotherapy (NCRT), adjuvant chemotherapy, adjuvant chemoradiotherapy (CRT), and surgery only. The primary endpoint was receipt of NAC or NCRT. Patients were 1-to-1 propensity score matched for receiving any neoadjuvant therapy. Multivariable logistic regression was used to identify predictors of receipt of any neoadjuvant therapy and receipt of any adjuvant therapy., Results: Twenty-five thousand and seventy-three patients were included in the analysis. Patients were treated with NAC (25.0%), NCRT (31.4%), adjuvant chemotherapy (6.5%), adjuvant CRT (12.6%), and surgery only (24.5%). Compared to 2006-2011, patients diagnosed between 2012 and 2017 experienced the greatest increases in NAC (18.6% vs. 29.0%; p < 0.001) and NCRT (25.0% vs. 35.5%; p < 0.001). Median OS was 44.9 months. OS was longest for patients who received any neoadjuvant therapy compared to those receiving adjuvant or surgery only (51.0 vs. 42.4 vs. 38.0 months, respectively; p < 0.001). Patients who were Black, in the lowest income quartile or treated at lower volume facilities were less likely to receive NAT (all p < 0.001)., Conclusions: There has been significant acceleration in the use of neoadjuvant therapy for GA. Currently, NCRT followed by surgery are the most common treatment sequences in the United States. Additional trials are needed to further define the optimal treatment sequence., (© 2024 The Author(s). Journal of Surgical Oncology published by Wiley Periodicals LLC.)

Introduction: While frailty has gained attention for its utility in risk stratification, no studies have directly compared them to existing risk calculators. The objective of this study was to compare the risk stratification of the American College of Surgeons Surgical Risk Calculator (ACS-SRC), the Revised Risk Analysis Index (RAI-rev), and the Modified Frailty Index (5-mFI). The primary outcomes were 30-day postoperative morbidity, 30-day postoperative mortality, unplanned readmission, unplanned reoperation, and discharge disposition other than home., Methods: Patients undergoing anatomic lung resection for primary, nonsmall cell lung cancer were identified within the ACS National Quality Improvement Program (ACS NSQIP) database. Tools were compared for discrimination in the primary outcomes., Results: 9663 patients undergoing anatomic lung resection for cancer between 2012 and 2014 were included. The cohort was 53.1% female. Median age at diagnosis was 67 (IQR 59-74) years. Perioperative morbidity and mortality rates were 10.9% (n = 1048) and 1.6% (n = 158). Rates of 30-day postoperative unplanned readmission and reoperation were 7.5% (n = 725) and 4.8% (n = 468). The ACS-SRC had the highest discrimination for all measured outcomes, as measured by the area under the receiver operating curve (AUC) and corresponding confidence interval (95% CI). This included perioperative mortality (AUC 0.74, 95% CI 0.71-0.78), compared to RAI-rev (AUC 0.66, 95% CI 0.62-0.69) and 5-mFI (AUC 0.61, 95% CI 0.57-0.65; p < 0.001). The RAI-rev and 5-mFI had similar discrimination for all measured outcomes., Conclusion: ACS-SRC was the perioperative risk stratification tool with the highest predictive discrimination for adverse, 30-day, postoperative events for patients with cancer treated with anatomic lung resection., (© 2024 The Author(s). Journal of Surgical Oncology published by Wiley Periodicals LLC.)

To provide optimal care in pancreatic ductal adenocarcinoma, involvement of palliative medicine and nutritional support is recommended. Advances in endoscopy have resulted in robust options for biliary and gastrointestinal stenting for relief of obstruction. Notwithstanding, surgical hepaticojejunostomy and gastrojejunostomy remain incontrovertible considerations for biliary obstruction and gastric outlet obstruction, respectively. For PDAC-associated pain, opioid therapy continues to be the mainstay. However, refractory pain may be treated with interventional procedures such as celiac or splanchnic nerve blocks or neurolysis. In patients with PDAC, enteral nutrition can be further complicated by exocrine pancreatic insufficiency, which should be treated with oral pancreatic enzyme supplementation., Competing Interests: Disclosure The authors have no conflicts of interest to disclose., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Introduction: Regionalizing hepatic resections to high-volume hospitals (HVH) has improved outcomes, yet widened disparities in access. We sought to evaluate the association of hospital volume with quality care outcomes and overall survival (OS) between minor and major hepatectomy for primary liver cancer., Methods: The National Cancer Database identified patients with primary liver cancer who underwent minor/major hepatectomy (2009-2019). HVHs were defined by the top quartile in annual case volume (vs. the bottom three quartiles). Quality care outcomes (time to resection, margin status, length of stay, 30-day readmission, 30-day mortality, 90-day mortality) and OS were assessed using multivariable regression., Results: Overall, 6,988 patients underwent minor hepatectomy and 4880 major hepatectomy. No differences in quality care outcomes or OS based on hospital volume for minor hepatectomy were observed (all p > 0.05). Treatment at HVHs for major hepatectomy was associated with decreased odds of 30-day and 90-day mortality events (all p < 0.05). Median OS was 40.2 months [IQR 21.7-66.6] at HVHs versus 33.5 [IQR 17.0-58.7] at low-volume hospitals which remained independently predictive of improved OS on multivariable analysis (HR 0.86, 95% CI 0.79-0.93)., Conclusion: These results support regionalization to HVHs for major hepatectomy; however, minor hepatectomy can be safely performed at hospitals regardless of volume., (© 2024 Wiley Periodicals LLC.)

Background: For gastric gastrointestinal stromal tumors (GISTs), neoadjuvant imatinib is most often reserved for tumors near the gastroesophageal junction, multivisceral involvement, or limited metastatic disease. Whether localized gastric GISTs benefit from neoadjuvant therapy (NAT) remains unknown. We sought to examine factors associated with NAT utilization for localized gastric GISTs and evaluate implications on survival., Methods: The National Cancer Database identified patients with localized gastric GISTs treated with NAT (2010-2020), excluding tumors extending beyond the gastric wall, located in the cardia, or with metastatic disease. Multivariable logistic regression assessed characteristics of NAT use. After 1:1 propensity score matching, Kaplan-Meier methods and multivariable Cox regression assessed overall survival (OS)., Results: Of 7203 patients, 762 (10.6%) received NAT followed by resection. On multivariable analysis, increasing tumor size was associated with NAT use (<2.0 cm vs 2.0-5.0 cm [odds ratio {OR}, 2.03; 95% CI, 1.19-3.47; P = .010] vs >5 cm [OR, 16.87; 95% CI, 10.02-28.40; P < .001]). After propensity score matching, 1506 patients remained. Median OS for NAT was 46.0 months vs 43.0 months for resection (P = .059), which was independently predictive of improved survival on multivariable analysis (hazard ratio [HR], 0.89; 95% CI, 0.80-0.99; P = .041). Subgroup analysis by tumor size showed no survival differences for tumors <2.0 cm or from 2.0 to 5.0 cm. Median OS was higher for tumors > 5.0 cm treated with NAT (NAT, 45.4 months [IQR, 29.5-65.9] vs upfront resection, 42.3 months [IQR 26.9-62.8]) and associated with improved survival on multivariable analysis (HR, 0.88; 95% CI, 0.78-0.99; P = .040)., Conclusion: Although patients who received NAT had improved survival, this was primarily due to tumors >5.0 cm. Expanding NAT selection criteria to include localized gastric GISTs >5.0 cm may improve outcomes and warrants investigation through clinical trials., (Copyright © 2024 Society for Surgery of the Alimentary Tract. Published by Elsevier Inc. All rights reserved.)

Introduction: Perioperative risk stratification is an essential component of preoperative planning for cancer surgery. While frailty has gained attention for its utility in risk stratification, no studies have directly compared it to existing risk calculators. Therefore, the objective of this study was to compare the risk stratification of the American College of Surgeons Surgical Risk Calculator (ACS-SRC), the Revised Risk Analysis Index (RAI-rev), and the Modified Frailty Index (5-mFI). The primary outcomes were 30-day postoperative morbidity, 30-day postoperative mortality, unplanned readmission, unplanned reoperation, and discharge disposition other-than-home., Methods: Patients undergoing anatomic lung resection for primary, non-small cell lung cancer were identified within the American College of Surgeons National Quality Improvement Program (ACS NSQIP) database. The ACS-SRC, RAI-rev, and 5-mFI tools were used to predict adverse postoperative events. Tools were compared for discrimination in the primary outcomes., Results: 9663 patients undergoing anatomic lung resection for cancer between 2012 and 2014 were included. The cohort was 53.1% female. Median age at diagnosis was 67 (interquartile range = 59-74) years. Cardiothoracic surgeons performed 89% and general surgeons performed 11.0% of the operations. Perioperative morbidity and mortality rates were 10.9% (n = 1048) and 1.6% (n = 158). Rates of 30-day postoperative unplanned readmission and reoperation were 7.5% (n = 725) and 4.8% (n = 468). The ACS-SRC had the highest discrimination for all measured outcomes, as measured by the area under the receiver operating curve (AUC) and corresponding confidence interval (95% confidence interval [CI]). This included perioperative mortality (AUC = 0.74, 95% CI = 0.71-0.78), compared to RAI-rev (AUC = 0.66, 95% CI = 0.62-0.69) and 5-mFI (AUC = 0.61, 95% CI = 0.57-0.65; p < 0.001). The RAI-rev and 5-mFI had similar discrimination for all measured outcomes., Conclusion: ACS-SRC was the perioperative risk stratification tool with the highest predictive discrimination for adverse, 30-day, postoperative events for patients with cancer treated with anatomic lung resection., (© 2024 The Author(s). Journal of Surgical Oncology published by Wiley Periodicals LLC.)

Background: A complete total mesorectal excision is the criterion standard in curative rectal cancer surgery. Ensuring quality is challenging in a narrow pelvis, and obesity amplifies technical difficulties. Pelvimetry is the measurement of pelvic dimensions, but its role in gauging preoperatively the difficulty of proctectomy is largely unexplored., Objective: To determine pelvic structural factors associated with incomplete total mesorectal excision after curative proctectomy and build a predictive model for total mesorectal excision quality., Design: Retrospective cohort study., Setting: A quaternary referral center database of patients diagnosed with rectal adenocarcinoma (2009-2017)., Patients: Curative-intent proctectomy for rectal adenocarcinoma., Interventions: All radiological measurements were obtained from preoperative CT images using validated imaging processing software tools. Completeness of total mesorectal excision was obtained from histology reports., Main Outcome Measures: Ability of radiological pelvimetry and obesity measurements to predict total mesorectal excision quality., Results: Of the 410 cases meeting inclusion criteria, 362 underwent a complete total mesorectal excision (88%). Multivariable regression identified a deeper sacral curve (per 100 mm 2 [OR: 1.14; 95% CI, 1.06-1.23; p < 0.001]) and a greater transverse distance of the pelvic outlet (per 10 mm [OR:1.41, 95% CI, 1.08-1.84; p = 0.012]) to be independently associated with incomplete total mesorectal excision. An increased area of the pelvic inlet (per 10 cm 2 [OR: 0.85; 95% CI, 0.75-0.97; p = 0.02) was associated with a higher rate of complete mesorectal excision. No difference in visceral obesity ratio and visceral obesity (ratio >0.4 vs <0.4) between BMI (<30 vs ≥30) and sex was identified. A model was built to predict mesorectal quality using the following variables: depth of sacral curve, area of pelvic inlet, and transverse distance of the pelvic outlet., Limitations: Retrospective analysis is not controlled for the choice of surgical approach., Conclusions: Pelvimetry predicts total mesorectal excision quality in rectal cancer surgery and can alert surgeons preoperatively to cases of unusual difficulty. This predictive model may contribute to treatment strategy and aid in the comparison of outcomes between traditional and novel techniques of total mesorectal excision. See Video Abstract ., Uso De Mediciones De Pelvimetra Y Obesidad Visceral Basadas En Tc Para Predecir La Calidad De Tme En Pacientes Sometidos a Ciruga De Cncer De Recto: ANTECEDENTES:Una escisión mesorrectal total y completa es el estándar de oro en la cirugía curativa del cáncer de recto. Garantizar la calidad es un desafío en una pelvis estrecha y la obesidad amplifica las dificultades técnicas. La pelvimetría es la medición de las dimensiones pélvicas, pero su papel para medir la dificultad preoperatoria de la proctectomía está en gran medida inexplorado.OBJETIVO:Determinar los factores estructurales pélvicos asociados con la escisión mesorrectal total incompleta después de una proctectomía curativa y construir un modelo predictivo para la calidad de la escisión mesorrectal total.DISEÑO:Estudio de cohorte retrospectivo.ÁMBITO:Base de datos de un centro de referencia cuaternario de pacientes diagnosticados con adenocarcinoma de recto (2009-2017).PACIENTES:Proctectomía con intención curativa para adenocarcinoma de recto.INTERVENCIONES:Todas las mediciones radiológicas se obtuvieron a partir de imágenes de TC preoperatorias utilizando herramientas de software de procesamiento de imágenes validadas. La integridad de la escisión mesorrectal total se obtuvo a partir de informes histológicos.PRINCIPALES MEDIDAS DE VALORACIÓN:Capacidad de la pelvimetría radiológica y las mediciones de obesidad para predecir la calidad total de la escisión mesorrectal.RESULTADOS:De los 410 casos que cumplieron los criterios de inclusión, 362 tuvieron una escisión mesorrectal total completa (88%). Una regresión multivariable identificó una curva sacra más profunda (por 100 mm2); OR:1,14,[IC95%:1,06-1,23,p<0,001], y mayor distancia transversal de salida pélvica (por 10mm); OR:1,41, [IC 95%:1,08-1,84,p=0,012] como asociación independiente con escisión mesorrectal total incompleta. Un área aumentada de entrada pélvica (por 10 cm2); OR:0,85, [IC95%:0,75-0,97,p=0,02] se asoció con una mayor tasa de escisión mesorrectal completa. No se identificaron diferencias en la proporción de obesidad visceral y la obesidad visceral (proporción>0,4 vs.<0,4) entre el índice de masa corporal (<30 vs.>=30) o el sexo. Se construyó un modelo para predecir la calidad mesorrectal utilizando variables: profundidad de la curva sacra, área de la entrada pélvica y distancia transversal de la salida pélvica.LIMITACIONES:Análisis retrospectivo no controlado por la elección del abordaje quirúrgico.CONCLUSIONES:La pelvimetría predice la calidad de la escisión mesorrectal total en la cirugía del cáncer de recto y puede alertar a los cirujanos preoperatoriamente sobre casos de dificultad inusual. Este modelo predictivo puede contribuir a la estrategia de tratamiento y ayudar en la comparación de resultados entre técnicas tradicionales y novedosas de escisión mesorrectal total. (Traducción- Dr. Ingrid Melo)., (Copyright © The ASCRS 2024.)

Introduction: The International Study Group of Liver Surgery's criteria stratifies post-hepatectomy liver failure (PHLF) into grades A, B, and C. The clinical significance of these grades has not been fully established., Methods: The American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) hepatectomy-targeted database was analyzed. Outcomes between patients without PHLF, with grade A PHLF, and grade B or C PHLF were compared. Univariate and multivariable logistic regression were performed., Results: Six thousand two hundred seventy-four adults undergoing elective major hepatectomy were included in the analysis. The incidence of grade A PHLF was 4.3% and grade B or C was 5.3%. Mortality was similar between patients without PHLF (1.2%) and with grade A PHLF (1.1%), but higher in those with grades B or C PHLF (25.4%). Overall morbidities rates were 19.3%, 41.7%, and 72.8% in patients without PHLF, with grade A PHLF, and with grade B or C PHLF, respectively (p < 0.001). Grade A PHLF was associated with increased morbidity (grade A: odds ratios [OR] 2.7 [95% CI: 2.0-3.5]), unplanned reoperation (grade A: OR 3.4 [95% CI: 2.2-5.1]), nonoperative intervention (grade A: OR 2.6 [95% CI: 1.9-3.6]), length of stay (grade A: OR 3.1 [95% CI: 2.3-4.1]), and readmission (grade A: OR 1.8 [95% CI: 1.3-2.5]) compared to patients without PHLF., Conclusions: Although mortality was similar between patients without PHLF and with grade A PHLF, other postoperative outcomes were notably inferior. Grade A PHLF is a clinically distinct entity with relevant associated postoperative morbidity., (© 2024 The Authors. Journal of Surgical Oncology published by Wiley Periodicals LLC.)

BACKGROUND AND OBJECTIVES: Neoadjuvant chemotherapy (NAC) and chemoradiation (NCRT) have demonstrated improved survival for gastric cancer. However, the optimal neoadjuvant treatment remains unclear. We sought to evaluate perioperative and histopathologic outcomes among neoadjuvant treatments for locoregional gastric cancer., Methods: The National Cancer Database queried patients who received NAC or NCRT followed by resection for T2-T4 and/or node-positive gastric cancer (2006-2018). Logistic and Poisson regression assessed perioperative (30-day readmission, 30- and 90-day mortality, length of stay [LOS]) and histopathologic outcomes (pathologic complete response [PCR], margin status, and negative pathologic lymph nodes [ypN0]). Kaplan-Meier methods and Cox regression assessed overall survival (OS)., Results: Of 9831 patients, 4221 (42.9%) received NAC and 5610 (57.1%) NCRT. There were no differences in perioperative outcomes, apart from patients treated with NCRT exhibiting increased LOS (incidence rate ratio 1.09, 95% confidence interval [CI] 1.03-1.16). Patients who received NCRT were more likely to achieve PCR, margin-negative resection, and ypN0 (all p < 0.05). Median OS was 36.8 months for NAC and 33.6 months for NCRT (p < 0.001). NCRT independently predicted worse OS (vs. NAC, hazard ratio 1.10, 95% CI 1.03-1.18)., Conclusion: NCRT was associated with better histologic tumor response although NAC was associated with improved OS. Better understanding prognostication through histologic assessment following neoadjuvant therapy is needed., (© 2023 The Authors. Journal of Surgical Oncology published by Wiley Periodicals LLC.)

Colorectal cancer (CRC) is the third most commonly diagnosed cancer in men and women (Siegel et al. in CA Cancer J Clin 72(1):7-33). Over one-half of newly diagnosed individuals will develop liver metastases. Among those with liver-only metastatic disease, only about one in five will be candidates for potentially curable resection., (© 2024. The Author(s), under exclusive license to Springer Nature Switzerland AG.)

Despite overall advances in cancer therapy, patients with pancreatic ductal adenocarcinoma continue to have a poor prognosis. While adjuvant therapy is still considered standard, there is mounting evidence that neoadjuvant therapy confers similar benefits in patients with locally advanced disease. The primary measures of response are radiographic, biochemical, margin status, and pathologic. Given overall low response rates and the need for new treatment strategies, standard metrics remain important to the investigation of new systemic agents., (© 2021 Wiley Periodicals LLC.)

Background: The purpose of this study was to compare the results and complications among obese veterans undergoing sleeve gastrectomy and gastric bypass at a low-volume center., Materials and Methods: This is a retrospective review of bariatric procedures performed by a single surgeon from 2009-2013. Outcomes of interest were mortality, complications, and length of stay. Weight loss and comorbidity resolution were compared between sleeve gastrectomy (SG) and Roux-y gastric bypass (RYGB). Length of stay and distance traveled to receive services were analyzed. Distributed groups were compared with Student's t test. Welch's correction was used where variances were unequal via ANOVA. Complications were compared using Fisher's exact test., Results: Eighty-five patients (SG = 51, RYGB = 34) were analyzed. Postoperatively, patients were seen in clinic, contacted by phone or email, and their electronic health care records were reviewed. Average length of follow-up was 114.3 weeks. Mortality was 0 %. Complication rates were comparable between groups. The percent total weight loss was 22.6 % for the SG and 27.5 % for the RYGB (p = 0.02). The percent excess weight loss was 49 % for SG and 55 % for RYGB (p = 0.149). Percent excess body mass index (BMI) loss was 54 and 61 % (p = 0.197) for SG and RYGB, respectively. Comorbidity resolution was similar between groups except for diabetes which was superior for RYGB (p = 0.03). Veterans lived an average of 141.3 miles from our VA, and all 85 patients were able to be contacted for follow-up., Conclusions: Despite long travel distances for high-risk veterans, bariatric surgery can be performed safely even at a low-volume VA hospital with acceptable morbidity and mortality and excellent follow-up. There was no difference in morbidity or mortality between patients undergoing SG vs RYGB.

Purpose. The gravimetric method of weighing surgical sponges is used to quantify intraoperative blood loss. The dry mass minus the wet mass of the gauze equals the volume of blood lost. This method assumes that the density of blood is equivalent to water (1 gm/mL). This study's purpose was to validate the assumption that the density of blood is equivalent to water and to correlate density with hematocrit. Methods. 50 µL of whole blood was weighed from eighteen rats. A distilled water control was weighed for each blood sample. The averages of the blood and water were compared utilizing a Student's unpaired, one-tailed t-test. The masses of the blood samples and the hematocrits were compared using a linear regression. Results. The average mass of the eighteen blood samples was 0.0489 g and that of the distilled water controls was 0.0492 g. The t-test showed P = 0.2269 and R (2) = 0.03154. The hematocrit values ranged from 24% to 48%. The linear regression R (2) value was 0.1767. Conclusions. The R (2) value comparing the blood and distilled water masses suggests high correlation between the two populations. Linear regression showed the hematocrit was not proportional to the mass of the blood. The study confirmed that the measured density of blood is similar to water.