Assessment of guidelines for bariatric and metabolic surgery: a systematic review and evaluation using appraisal of guidelines for research and evaluation II (AGREE II).

BACKGROUND: In recent years, multiple guidelines on bariatric and metabolic surgery were published, however, their quality remains unknown, leaving providers with uncertainty when using them to make perioperative decisions. This study aims to evaluate the quality of existing guidelines for perioperative bariatric surgery care. METHODS: A comprehensive search of MEDLINE and EMBASE were conducted from January 2010 to October 2022 for bariatric clinical practice guidelines. Guideline evaluation was carried out using the Appraisal of Guidelines for Research and Evaluation II (AGREE II) framework. RESULTS: The initial search yielded 1483 citations, of which, 26 were included in final analysis. The overall median domain scores for guidelines were: (1) scope and purpose: 87.5% (IQR: 57-94%), (2) stakeholder involvement: 49% (IQR: 40-64%), (3) rigor of development: 42.5% (IQR: 22-68%), (4) clarity of presentation: 85% (IQR: 81-90%), (5) applicability: 6% (IQR: 3-16%), (6) editorial independence: 50% (IQR: 48-67%), (7) overall impressions: 48% (IQR: 33-67%). Only six guidelines achieved an overall score >70%. CONCLUSIONS: Bariatric surgery guidelines effectively outlined their aim and presented recommendations. However, many did not adequately seek patient input, state search criteria, use evidence rating tools, and consider resource implications. Future guidelines should reference the AGREE II framework in study design.

Presentations, management and outcomes of postoperative bariatric patients seen in the emergency department.

BACKGROUND: Bariatric surgery is becoming increasingly common and postoperative patients often present to the emergency department (ED) with complications. We sought to describe the presenting complaints, management, and outcomes of postoperative bariatric surgery patients seen in the ED. METHODS: We conducted a health records review of 300 consecutive postoperative Roux-en-Y bypass surgery patients who presented to two tertiary care EDs of a major bariatric surgery center within one year of surgery. Cases were identified using a data analytic tool, and two evaluators abstracted clinical variables, imaging, treatments, and outcomes using the electronic health record. Attending emergency physicians verified the data and an experienced bariatric surgeon interpreted the computed tomography (CT) results and surgical procedures. RESULTS: We included 300 patients with mean age 43.0 years, 89.7% female. Of these, 70.0% presented within 30 days of surgery and 41.7% were admitted to hospital. ED treatments included intravenous fluids (67.0%), antiemetics (53.3%), and analgesia (61.9%). Patients presenting within 30 days of surgery were more likely to undergo a CT (74.3% vs 63.3%; p = 0.06) and to have clinically important CT findings (31.9% vs 6.6%; p ≤0.001). More of the ≤30-day patients were admitted to hospital (46.2% vs 31.1%; p = 0.02). While a higher proportion of patients presenting after 30 days underwent a procedure, a large number of those were not directly related to bariatric surgery, such as appendectomy and cholecystectomy. Of the 34 patients undergoing a procedure, the majority presented with abdominal pain (76.5%). CONCLUSION: This is the first detailed health records review of postoperative bariatric patients seen in the ED in the emergency medicine literature. Those presenting with abdominal pain were more likely to undergo CT abdomen and a surgical procedure. Similarly, those presenting within 30 days of surgery were more likely to have significant CT findings and require hospital admission. Others presenting with primarily nausea and vomiting may improve with ED symptom management and be discharged home with bariatric team follow-up.

A lay of the land: a description of academic acute care surgery models in Canada.

BACKGROUND: Patients who require emergency general surgery (EGS) are at a substantially higher risk for perioperative morbidity and mortality than patients undergoing elective general surgery. The acute care surgery (ACS) model has been shown to improve EGS patient outcomes and cost-effectiveness. A recent systematic review has shown extensive heterogeneity in the structure of ACS models worldwide. The objective of this study was to describe the current landscape of ACS models in academic centres across Canada. METHODS: We sent an online questionnaire to the 18 academic centres in Canada. The lead ACS physicians from each institution completed the questionnaire, describing the structure of their ACS models. RESULTS: In total, 16 institutions responded, all of which reported having ACS models, with a total of 29 ACS services described. All services had resident coverage. Of the 29, 18 (62%) had dedicated allied health care staff. The staff surgeon was free from elective duties while covering ACS in 17/29 (59%) services. More than half (15/29; 52%) of the services described protected ACS operating room time, but only 7/15 (47%) had a dedicated ACS room all 5 weekdays. Four of 29 services (14%) had no protected ACS operating room time. Only 1/16 (6%) institutions reported a mandate to conduct ACS research, while 12/16 (75%) found ACS research difficult, owing to lack of resources. CONCLUSION: We saw large variations in the structure of ACS models in academic centres in Canada. The components of ACS models that are most important to patient outcomes remain poorly defined. Future research will focus on defining the necessary cornerstones of ACS models.

Redefining the role of routine postoperative bloodwork following uncomplicated bariatric surgery.

BACKGROUND: A quality improvement opportunity was identified to de-adopt the low-value care practice of routinely performing bloodwork for all patients undergoing elective bariatric surgery. While these patients are typically discharged on postoperative day 1 (POD1) after bloodwork is performed, it is uncommon for the discharge plan to change due to unexpected laboratory abnormalities alone. METHODS: Patients undergoing bariatric surgery between September 2020 and April 2021 only had POD1 bloodwork if there were perioperative clinical concerns, they had insulin-dependent diabetes, or they were therapeutically anticoagulated. Thirty-day Emergency Department (ED) visits and readmissions were monitored as balancing measures. Outcomes were compared to a control group that underwent bariatric surgery prior to September 2020 when POD1 laboratory testing was routinely performed. Financial and environmental costs were estimated based our institutional standards. RESULTS: The intervention group consisted of 303 patients: 248 (82%) Roux-en-Y gastric bypasses and 55 (18%) sleeve gastrectomies. Most patients (n = 256, 84.5%) did not have POD1 bloodwork. Twelve (3.9%) had bloodwork performed in violation of our protocol, of which none had a change in management based on the results. Of the 35 (12%) who had appropriately ordered bloodwork, 6 (2%) required a transfusion and 2 (0.7%) required a second surgery on the same admission for hemorrhage. Forty-four (14.5%) had 30-day ED visits of which 17 (5.6%) were within 7 days. Sixteen (5.3%) were readmitted. There were no significant differences between intervention and control groups in the rate of transfusion, second surgery, or 30-day ED visits. The avoidance of POD1 bloodwork saved approximately $6602.24 in lab processing fees alone and 512 test tubes. CONCLUSION: POD1 bloodwork can be safely avoided in the absence of clinical concerns. In addition to not significantly increasing postoperative complications, there were benefits from a financial cost, environmental impact, and patient discomfort perspective.

Paraesophageal hernia repair in elderly patients: outcomes from a 10-year retrospective study.

BACKGROUND: Laparoscopic surgery has become the preferred management for paraesophageal hernias (PEH); however surgical management versus watchful waiting remains controversial in older patients. METHODS: This retrospective study analyzed the outcomes of PEH repair in elderly patients surgically managed at The Ottawa Hospital over a 10-year period. Patients older than 60 years who underwent PEH repair were examined with respect to presentation, technique and associated complications. RESULTS: Despite similar demographics, our study groups showed significantly different characteristics of surgical techniques. Most surgeries were performed laparoscopically; however, patients aged 70 years or older underwent more open and emergency surgeries than the younger group. Despite a 30-day postoperative complication rate of 45 % and 13 % in the older (≥ 70 yr) and younger (60-69 yr) groups, respectively, the rates during elective repair were similar. There were no deaths in the younger group, whereas the 30-day mortality rate was 5 % in patients aged 70 years and older, including a 2-fold increase with emergency repair (4 v. 2 patients). CONCLUSION: Management of PEH in older adults remains controversial in relation to a surgical versus watchful waiting approach. We found that in patients aged 70 years and older who undergo surgical management of PEH experience more open and emergency procedures, which are associated with higher complication rates. However, in the elective setting older patients had increased laparoscopic repairs and comparable complication rates to younger patients. We found the greatest outcomes with early, elective laparoscopic repair, irrespective of age.

Implementation, results and face validity of the Consultation and Relational Empathy measure in a Canadian department of surgery.

BACKGROUND: The Consultation and Relational Empathy (CARE) Measure, a validated questionnaire designed to assess patients' perceptions of their physician's communication skills and empathy, has been used to assess empathy in medical specialties but has seldom been applied to surgery. We assessed empathy and communication skills among a group of surgeons within a single academic institution. METHODS: All surgeons within our department of surgery were invited to participate. Patients seen in clinics of participating surgeons were recruited prospectively from July 2018 to February 2019. At the end of each clinical encounter, they were asked to complete a CARE survey. Surveys were analyzed according to previously validated inclusion and exclusion criteria. We calculated mean scores for each surgeon and surgical division. About 6 months after study completion, surgeons were provided with their individual score and de-identified division scores, and were asked to complete a follow-up survey assessing their attitudes toward the CARE Measure. RESULTS: Of the 82 surgeons invited, 51 (62%) agreed to participate; 7 had fewer than 25 completed surveys and were excluded from analysis. A total of 1801 surveys for 44 surgeons (33 male and 11 female) were included in the final analysis. The average CARE score across the department was 46.9 (95% confidence interval [CI] 46.6-47.1). Female surgeons received significantly higher scores than male surgeons (mean 47.6 [95% CI 47.1-48.0] v. 46.7 [95% CI 46.4-48.0]). Of the 35 surgeons who responded to the follow-up survey, 31 (89%) felt that the questions in the CARE Measure applied to their practice, and half of these reported that they intended to make changes in response to the feedback. CONCLUSION: We found high communication and empathy scores among surgeons in the outpatient setting, with enough variability to encourage continued improvement. The CARE Measure appears to have face validity among surgeons, and the vast majority found it relevant to their practice. Further study is needed to formally assess the relevance, performance, reliability and construct validity of this measure.

Smoking in bariatric surgery: a systematic review.

BACKGROUND: The prevalence of smoking among patients undergoing bariatric surgery has been reported to be as high as 40%. The effect of smoking in the perioperative period has been extensively studied for various surgical procedures, but limited data are available for bariatric surgery. The objective of this study is to review the existing literature to assess: (1) the impact of smoking on postoperative morbidity and mortality after bariatric surgery, (2) the relationship between smoking and weight loss after bariatric surgery, and (3) the efficacy of smoking cessation in the perioperative period among bariatric surgery patients. METHODS: A comprehensive search of electronic databases including MEDLINE, EMBASE and the Cochrane Library from 1946 to February 2020 was performed to identify relevant articles. Following an initial screen of 940 titles and abstracts, 540 full articles were reviewed. RESULTS: Forty-eight studies met criteria for analysis: five structured interviews, three longitudinal studies, thirty-two retrospective studies and eight prospective studies. Smoking within 1 year prior to bariatric surgery was found to be an independent risk factor for increased 30-day mortality and major postoperative complications, particularly wound and pulmonary complications. Smoking was significantly associated with long-term complications including marginal ulceration and bone fracture. Smoking has little to no effect on weight loss following bariatric surgery, with studies reporting at most a 3% increased percentage excess weight loss. Rates of smoking recidivism are high with studies reporting that up to 17% of patients continue to smoke postoperatively. CONCLUSIONS: Although current best practice guidelines recommend only a minimum of 6 weeks of abstinence from smoking prior to bariatric surgery, the findings of this review suggest that smoking within 1 year prior to bariatric surgery is associated with significant postoperative morbidity. More investigation is needed on strategies to improve smoking cessation compliance among bariatric surgery patients in the perioperative period.

Effect of intraperitoneal local anesthesia on enhanced recovery outcomes after bariatric surgery: a randomized controlled pilot study.

BACKGROUND: Patients with extreme obesity are at high risk for adverse perioperative events, especially when opioid-centric analgesic protocols are used, and perioperative pain management interventions in bariatric surgery could improve safety, outcomes and satisfaction. We aimed to evaluate the impact of intraperitoneal local anesthesia (IPLA) on enhanced recovery after bariatric surgery (ERABS) outcomes. METHODS: We conducted a prospective double-blind randomized controlled pilot study in adherence to an a priori peer-reviewed protocol. Patients undergoing laparoscopic Roux-en-Y gastric bypass surgery (LRYGB) with an established ERABS protocol between July 2014 and February 2015 were randomly allocated to receive either IPLA with 0.2% ropivacaine (intervention group) or normal saline (control group). We measured pain scores, analgesic consumption and adverse effects. Functional prehabilitation outcomes, including peak expiratory flow (PEF) and the Six Minute Walk Test (6MWT) and Quality of Recovery Survey-40 (QoR-40) scores, were assessed before surgery, and 1 day and 7 days postoperatively. RESULTS: One hundred patients were randomly allocated to the study groups, of whom 92 completed the study, 46 in each group. There were no statistically significant differences between the 2 groups in baseline characteristics or any primary or secondary outcomes. Pain scores and analgesic consumption were low in both groups. There were no adverse events. Significant declines in PEF and 6MWT and QoR-40 scores were noted on postoperative day 1 in both groups; the values returned to baseline on postoperative day 7 in both groups. CONCLUSION: Intraperitoneal local anesthesia with ropivacaine did not reduce postoperative pain or analgesic consumption when administered intraoperatively to patients undergoing LRYGB. Standardization of the ERABS protocol benefited patients, with functional prehabilitation outcomes returning to baseline postoperatively. Trial registration: ClinicalTrials.gov no. NCT02154763.

Canadian consensus statement: enhanced recovery after surgery in bariatric surgery.

BACKGROUND: In Canada, bariatric surgery continues to remain the most effective treatment for severe obesity and its comorbidities. As the number of bariatric surgeries continues to grow, the need for consensus guidelines for optimal perioperative care is imperative. In colorectal surgery, enhanced recovery after surgery (ERAS) protocols were created for this purpose. The objective of this review is to develop evidence-based ERAS guidelines for bariatric surgery. METHODS: A literature search of the MEDLINE database was performed using ERAS-specific search terms. Recently published articles with a focus on randomized controlled trials, systematic reviews, and meta-analyses were included. Quality of evidence and recommendations were evaluated using the GRADE assessment system. RESULTS: Canadian bariatric surgeons from six provinces and ten bariatric centers performed a review of the evidence surrounding ERAS in bariatric surgery and created consensus guidelines for 14 essential ERAS elements. Our main recommendations were (1) to encourage participation in a presurgical weight loss program; (2) to abstain from tobacco and excessive alcohol; (3) low-calorie liquid diet for at least 2 weeks prior to surgery; (4) to avoid preanesthetic anxiolytics and long-acting opioids; (5) unfractionated or low-molecular-weight heparin prior to surgery; (6) antibiotic prophylaxis with cefazolin ± metronidazole; (7) reduced opioids during surgery; (8) surgeon preference regarding intraoperative leak testing; (9) nasogastric intubation needed only for Veress access; (10) to avoid abdominal drains and urinary catheters; (11) to prevent ileus by discontinuing intravenous fluids early; (12) postoperative analgesia with acetaminophen, short-term NSAIDS, and minimal opioids; (13) to resume full fluid diet on first postoperative day; (14) early telephone follow-up with full clinic follow-up at 3-4 weeks. CONCLUSIONS: The purpose of addressing these ERAS elements is to develop guidelines that can be implemented and practiced clinically. ERAS is an excellent model that improves surgical efficiency and acts as a common perioperative pathway. In the interim, this multimodal bariatric perioperative guideline serves as a common consensus point for Canadian bariatric surgeons.

Impact of miniport laparoscopic cholecystectomy versus standard port laparoscopic cholecystectomy on recovery of physical activity: a randomized trial.

INTRODUCTION: We conducted a randomized trial comparing minilaparoscopic cholecystectomy (MLC) to conventional laparoscopic cholecystectomy (CLC) to determine whether MLC accelerated recovery of physical activity after elective surgery (NCT01397565). METHODS: A total of 115 patients scheduled for elective cholecystectomy were randomized to either CLC or MLC. Both procedures used a 10-mm umbilical port, but the three upper abdominal ports were 5 mm in CLC and 3 mm in MLC. Primary outcome was self-reported physical activity 1 month after surgery as estimated by Community Health Activities Model Program for Seniors questionnaire (kcal/kg/week). Secondary outcomes were umbilical pain, abdominal pain, nausea and fatigue (VAS, 1-10), and cosmetic result at one and 3 months. Patients received identical surgical dressings for 1 week, and assessors were blinded to group allocation. RESULTS: Forty-two patients randomized to CLC group and 33 patients randomized to MLC remained in the trial and were analyzed. Both groups were similar at baseline characteristics. In the MLC group, at least one 5-mm port was used in 17 (51.5 %) mainly due to unavailability of ML equipment. Median (IQR) physical activity for the CLC and MLC groups was similar at baseline (23.4 [13.1, 44.6] vs 23.6 [14.2, 66.9] kcal/kg/week, p = 0.35) and at 1 month (20 [7.9, 52.5] vs 16.8 [11.8, 28.6] kcal/kg/week, p = 0.90). One month post-op, umbilical pain and abdominal pain were similar, but the CLC group reported higher fatigue (4 [1-5] vs 1 [0-4], p = 0.05) and worse scar appearance scores (4 [3, 4] vs 4.5 [4, 5], p = 0.009). At 3 months, the CLC group had worse scar appearance (4 [3-5] vs 5 [4-5], p = 0.02) and lower scar satisfaction scores (4 [3, 4] vs 4 [3.5-4], p = 0.04). CONCLUSION: Recovery of physical activity was similar after MLC and CLC. MLC resulted in less fatigue and better scar appearance and satisfaction. These benefits were seen despite the need to upsize one or more ports in more than half of patients related to availability of the miniature instruments.

Retrospective assessment of the utility of an iron-based agent for contrast-enhanced magnetic resonance venography in patients with endstage renal diseases.

PURPOSE: To compare abdominopelvic and lower extremity venous enhancement in contrast-enhanced magnetic resonance venography (ceMRV), using iron-based ferumoxytol and gadolinium-based gadofosveset. MATERIALS AND METHODS: This was a Health Insurance Portability and Accountability Act (HIPAA)-compliant retrospective study. Thirty-four patients were identified who had undergone ceMRV using either ferumoxtyol (Group A, all with chronic renal insufficiency) or gadofosveset (Group B). Two radiologists rated confidence for evaluation of the major abdominopelvic and lower extremity veins from 4 (excellent confidence) to 1 (nondiagnostic). A third radiologist measured signal intensity ratios (SIRs) of venous segments compared with adjacent muscles. Scores were compared using repeated-measures analysis of variance (ANOVA). The medical record was searched for contemporaneous imaging to confirm the ceMRV findings. RESULTS: In Group A, 14/225 venous segments were thrombosed, compared with 18/282 in Group B. There was no statistically significant difference between confidence scores (3.79 ± 0.44 vs. 3.85 ± 0.44, P = 0.34) or SIRs (2.40 ± 0.73 vs. 2.38 ± 0.51, P = 0.51) for patent segments in the two groups, nor were confidences scores (3.89 ± 0.29 vs. 3.72 ± 0.46, P = 0.31) or SIRs (0.90 ± 0.12 vs. 0.84 ± 0.19, P = 0.31) significantly different for thrombosed segments. Contemporaneous imaging confirmed ceMRV findings in 227 segments. CONCLUSION: ceMRV can be performed with ferumoxytol, yielding similar image quality to a blood pool gadolinium-based contrast agent.

Obesity triples the radiation dose of stone protocol computerized tomography.

PURPOSE: Patients with recurrent nephrolithiasis are often evaluated and followed with computerized tomography. Obesity is a risk factor for nephrolithiasis. We evaluated the radiation dose of computerized tomography in obese and nonobese adults. MATERIALS AND METHODS: We scanned a validated, anthropomorphic male phantom according to our institutional renal stone evaluation protocol. The obese model consisted of the phantom wrapped in 2 Custom Fat Layers (CIRS, Norfolk, Virginia), which have been verified to have the same radiographic tissue density as fat. High sensitivity metal oxide semiconductor field effect transistor dosimeters were placed at 20 organ locations in the phantoms to measure organ specific radiation doses. The nonobese and obese models have an approximate body mass index of 24 and 30 kg/m(2), respectively. Three runs of renal stone protocol computerized tomography were performed on each phantom under automatic tube current modulation. Organ specific absorbed doses were measured and effective doses were calculated. RESULTS: The bone marrow of each model received the highest dose and the skin received the second highest dose. The mean ± SD effective dose for the nonobese and obese models was 3.04 ± 0.34 and 10.22 ± 0.50 mSv, respectively (p <0.0001). CONCLUSIONS: The effective dose of stone protocol computerized tomography in obese patients is more than threefold higher than the dose in nonobese patients using automatic tube current modulation. The implication of this finding extends beyond the urological stone population and adds to our understanding of radiation exposure from medical imaging.

Impact of an enhanced recovery program on short-term outcomes after scheduled laparoscopic colon resection.

INTRODUCTION: Both enhanced recovery programs (ERP) and laparoscopy can reduce complications and length of stay (LOS) in colon surgery. We investigated whether ERP further improved the short-term outcomes of scheduled laparoscopic colectomies. METHODS: We performed an audit of all patients undergoing scheduled laparoscopic colon resection between January 2003 and August 2010 in our institution. An ERP including accelerated introduction of oral nutrition, mobilization, pain control, and catheter management was introduced in 2005. Demographic data, intra and postoperative details and 30-day ER visit and readmission rate were collected. We compared LOS and short-term outcomes for patients on the program with those receiving traditional postoperative care using Chi-square and regression models. Data are presented as median [25th, 75th percentile]. Statistical significance was defined as p < 0.05. RESULTS: 136 (46%) of 297 eligible patients were enrolled in the ERP. At baseline, the two groups had similar demographic characteristics, but patients in the ERP were more likely to have their operation by a colorectal surgeon (p = 0.01). Patients in the ERP ate solids earlier (p < 0.001) and had earlier removal of their urinary catheter (p < 0.001). LOS was 4 [3, 6] days for both groups (p < 0.01), with more patients in the ERP discharged by POD 3 (p < 0.001). After adjusting for other variables, ERP enrolment remained an independent predictor of LOS (p < 0.01), along with age (p < 0.01) and in-hospital complications (p < 0.001). Complication rates were similar between the two groups. Patients in the ERP had significantly fewer ER visits (p = 0.02), but there were no differences in readmission rates. CONCLUSION: In patients undergoing scheduled laparoscopic colectomy in a university-based clinical teaching unit, ERP can further reduce length of stay and postoperative ER visits without increasing readmission rates.

Role of Tranexamic Acid (TXA) in Preventing Bleeding Following Sleeve Gastrectomy: a Systematic Review and Meta-analysis.

BACKGROUND: Tranexamic acid (TXA) has drawn growing interest over the last decade for its benefit in optimizing post-operative bleeding, yet its role in bariatric surgery is poorly understood. METHODS: The medical librarian developed and executed comprehensive searches on September 28, 2022. The population of interest included adults who underwent elective bariatric surgery. The intervention was tranexamic acid administration while the comparison was placebo or standard peri-operative therapy. The primary outcome of interest was post-operative bleeding which was defined a priori. RESULTS: A total of four studies were identified comprising of 475 patients. Of those, 207 (50%) received TXA at induction and all underwent laparoscopic sleeve gastrectomy (LSG). The majority of patients were female (n = 343, 80.7%) with ages ranging from 17 to 70 years of age and mean BMIs ranging from 37 to 56 kg/m2. Post-operative bleeding after LSG ranged from 0 to 28% depending on bleed definition and TXA administration with no differences in venous thromboembolic events or mortality between groups. Meta-analysis of post-operative bleeding demonstrated a statistically significant benefit with TXA administration (OR 0.40; 95% CI 0.23-0.70; p = 0.001) for patients undergoing elective LSG. CONCLUSIONS: Intravenous tranexamic acid at the time of laparoscopic sleeve gastrectomy is associated with a significant reduction of post-operative bleeding with no observed differences in thromboembolic events or mortality. Further high-quality studies are needed to better delineate the ideal bariatric population to receives TXA in addition to the optimal timing, dose, and duration of TXA therapy.

Rate of contrast material extravasations and allergic-like reactions: effect of extrinsic warming of low-osmolality iodinated CT contrast material to 37 degrees C.

PURPOSE: To retrospectively determine whether extrinsic warming of the low-osmolality contrast material iopamidol to 37°C prior to intravenous administration at computed tomography (CT) affects extravasation and allergic-like reaction rates. MATERIALS AND METHODS: The need to obtain informed patient consent was waived for this HIPAA-compliant and institutional review board-approved analysis. All adverse events related to the intravenous administration of iopamidol during CT examinations occurring 200 days before (period 1) and 200 days after (period 2) the cessation of extrinsic contrast material warming (37°C) for intravenous injections of less than 6 mL/sec at Duke University Medical Center (Durham, NC) were retrospectively reviewed. Adverse event rates were compared by using χ2 statistics. RESULTS: There were 12,682 injections during period 1 (10,831 injections of iopamidol 300 and 1851 injections of iopamidol 370) and 12,138 injections (10, 064 injections of iopamidol 300 and 2074 injections of iopamidol 370) during period 2. Adverse event rates for iopamidol 300 were not affected by extrinsic warming (extravasation rates: 0.30% [32 of 10,831] in period 1 vs 0.23% [23 of 10,064] in period 2, P=.64; allergic-like reaction rates: 0.39% [42 of 10,831] in period 1 vs 0.46% [46 of 10,064] in period 2, P=.74; overall adverse events: 0.68% [74 of 10,831] in period 1 vs 0.69% [69 of 10,064] in period 2, P=.99). Discontinuation of extrinsic warming was associated with significantly increased extravasation and overall adverse event rates for iopamidol 370 (extravasation rates: 0.27% [five of 1851] vs 0.87% [18 of 2074], P=.05; allergic-like reaction rates: 0.16% [three of 1851] vs 0.39% [eight of 2074], P=.42; overall adverse events: 0.43% [eight of 1851] vs 1.25% [26 of 2074], P=.02). CONCLUSION: Extrinsic warming (to 37°C) does not appear to affect adverse event rates for intravenous injections of iopamidol 300 of less than 6 mL/sec but is associated with a significant reduction in extravasation and overall adverse event rates for the more viscous iopamidol 370.

Histogram analysis of small solid renal masses: differentiating minimal fat angiomyolipoma from renal cell carcinoma.

OBJECTIVE: The objective of our study was to retrospectively determine whether minimal fat renal angiomyolipoma can be differentiated from clear cell or papillary renal cell carcinoma (RCC) in small renal masses using attenuation measurement histogram analysis on unenhanced CT. MATERIALS AND METHODS: Twenty minimal fat renal angiomyolipomas were compared with 22 clear cell RCCs and 23 papillary RCCs using an institutional database. All masses were histologically confirmed and all minimal fat renal angiomyolipomas lacked radiographic evidence of macroscopic fat. Using attenuation measurement histogram analysis, two blinded radiologists determined the percentage of negative pixels within each renal mass. The percentages of negative pixels below attenuation thresholds of 0, -5, -10, -15, -20, -25, and -30 HU were recorded. Sensitivity, specificity, positive predictive value, negative predictive value, and receiver operator characteristic curves for the diagnosis of minimal fat renal angiomyolipoma were generated for each threshold. The Student t test was used to compare radiologists and cohorts. Previously published attenuation and pixel-counting thresholds reported as having a specificity of near 100% for discriminating between minimal fat renal angiomyolipomas and RCCs were analyzed. RESULTS: The mean maximal transverse lesion diameter was 1.8 cm for minimal fat renal angiomyolipomas (SD, 0.5 cm; range, 1.1-3.0 cm), 2.1 cm for clear cell RCCs (SD, 0.5 cm; range, 1.0-2.9 cm), and 2.1 cm for papillary RCCs (SD, 0.7 cm; range, 1.3-3.9 cm). No significant difference in the percentage of negative pixels was found between minimal fat renal angiomyolipomas and clear cell RCCs or between minimal fat renal angiomyolipomas and papillary RCCs at any of the selected attenuation thresholds for either radiologist (p = 0.210-0.499). Radiologist 1 and radiologist 2 used significantly different region-of-interest sizes (p < 0.001), but neither radiologist could differentiate minimal fat renal angiomyolipoma from RCC. No previously published threshold allowed discrimination between minimal fat renal angiomyolipoma and RCC with 100% specificity. CONCLUSION: Attenuation measurement histogram analysis cannot reliably differentiate minimal fat renal angiomyolipoma from RCC.

Characterization of adrenal nodules with dual-energy CT: can virtual unenhanced attenuation values replace true unenhanced attenuation values?

OBJECTIVE: The purpose of our study was to investigate whether virtual unenhanced adrenal nodule attenuation values can replace true noncontrast attenuation values. MATERIALS AND METHODS: Twenty-three incidentally discovered adrenal nodules (19 adenomas and four metastases) were identified in 19 patients (11 men and eight women; mean age, 65 years; age range, 38-84 years) who underwent unenhanced single-energy CT followed by contrast-enhanced dual-energy CT on the same scanner. A virtual unenhanced imaging dataset was generated from each dual-energy CT dataset. CT attenuation of each adrenal nodule was measured at the same location on virtual unenhanced images and true unenhanced images by three radiologists and mean values compared using the Student t test. Correlation between virtual unenhanced and true unenhanced values was determined using linear regression analysis. The mean difference and percentage of diagnostic agreement were also determined. Interreader variability was assessed using the intraclass correlation coefficient (ICC). RESULTS: The mean ± SD attenuation values for virtual unenhanced images and true unenhanced images were 14.7 ± 15.1 HU and 12.9 ± 13.4 HU, respectively (p = 0.2). Strong positive correlation was observed between virtual unenhanced images and true unenhanced images (R = 0.83-0.87). The mean difference between virtual unenhanced images and true unenhanced images was 1.8 ± 1.7 HU. Diagnostic agreement between virtual unenhanced images and true unenhanced images was 83-91% for three radiologists. No malignant nodules were misclassified as benign on virtual unenhanced images. The ICC was 0.88 and 0.96 for virtual unenhanced images and true unenhanced images, respectively, indicating high interreader agreement. CONCLUSION: Virtual unenhanced and true unenhanced attenuation measurements of adrenal nodules were not significantly different and showed strongly positive linear correlation. This finding resulted in substantial diagnostic agreement between virtual unenhanced images and true unenhanced images for distinguishing benign from malignant nodules.

Detection of renal lesion enhancement with dual-energy multidetector CT.

PURPOSE: To determine whether dual-energy multidetector CT enables detection of renal lesion enhancement by using calculated nonenhanced images with spectral-based extraction in a non-body weight-restricted patient population. MATERIALS AND METHODS: Between January 2008 and December 2009, 139 patients were enrolled in this prospective HIPAA-compliant, institutional review board-approved study. Written informed consent was obtained from all patients. After single-energy nonenhanced 120-kVp CT images were acquired, contrast material-enhanced dual-energy multidetector CT images were acquired at 80 and 140 kVp. Calculated nonenhanced images were generated by using spectral-based iodine extraction. Lesion attenuation was measured on the acquired nonenhanced, calculated nonenhanced, and 140-kVp contrast-enhanced nephrographic images. Enhancement, defined as a 15-HU or greater increase in attenuation on the nephrographic images, was assessed by using the baseline attenuation on the acquired and calculated nonenhanced images. Acquired nonenhanced versus calculated nonenhanced image attenuation, as well as enhancement values, were compared by using paired Student t tests and Bland-Altman plots. RESULTS: Hypoattenuating (n = 66) and hyperattenuating (n = 28) cysts, angiomyolipomas (n = 18), and solid enhancing lesions (n = 27) were detected. Mean attenuation values for hypoattenuating cysts on the acquired and calculated nonenhanced CT images were 6.5 HU ± 5.8 (standard deviation) and 8.1 HU ± 3.1 (P = .13), respectively, with corresponding enhancement values of 1.1 HU ± 5.2 and -0.5 HU ± 6.2 (P = .12), respectively. Mean values for hyperattenuating cysts were 29.4 HU ± 5.6 on acquired images and 31.7 HU ± 5.1 on calculated images (P = .39) (corresponding enhancement, 4.7 HU ± 3.3 and 2.3 HU ± 4.1, respectively; P = .09). Mean values for fat-containing enhancing lesions were -90.6 HU ± 24.7 on acquired images and -85.9 HU ± 23.7 on calculated images (P = .57) (corresponding enhancement, 18.2 HU ± 10.1 and 13.6 HU ± 10.7, respectively; P = .19). Mean attenuation values for solid enhancing lesions were 26.0 HU ± 15.0 on acquired images and 27.7 HU ± 14.9 on calculated images (P = .45) (corresponding enhancement, 60.3 HU ± 13.1 and 58.3 HU ± 15.5, respectively; P = .38). CONCLUSION: Dual-energy CT acquisitions with spectral-based postprocessing enabled accurate detection of renal lesion enhancement across the attenuation spectrum of frequently encountered renal lesions in a non-body habitus-restricted patient population.

Diagnosis of renal angiomyolipoma with hounsfield unit thresholds: effect of size of region of interest and nephrographic phase imaging.

PURPOSE: To retrospectively determine the optimal Hounsfield unit threshold and region of interest (ROI) size required to accurately diagnose renal angiomyolipoma (AML) and differentiate it from renal cell carcinoma (RCC). MATERIALS AND METHODS: This retrospective study was institutional review board approved and HIPAA compliant, and the requirement for written informed patient consent was waived. The radiologic reports on 4502 dual-phase abdominal computed tomography (CT) examinations (nonenhanced and nephrographic phases, 5-mm collimation, 120-140 kVp, variable milliampere-second settings) performed in 2872 patients from June 2002 through October 2007 were reviewed. Solid-component masses reported as suspicious for RCC or AML were correlated with histologic and/or follow-up imaging findings. ROIs of three different sizes-tiny (8-13 mm(2)), small (19-24 mm(2)), and medium (30-35 mm(2))-were drawn in the lowest-attenuation focus on images obtained during both phases. The test characteristics (sensitivity, specificity, positive predictive value, negative predictive value, false-positive rate, false-negative rate) of multiple attenuation thresholds at each combination of ROI size and contrast enhancement phase were calculated, and receiver operating characteristic (ROC) curves were derived. Areas under the ROC curve were calculated. RESULTS: There were 217 RCCs and 65 AMLs. With an attenuation threshold of -10 HU or lower at nonenhanced CT, RCC would be misdiagnosed as AML in 11 (5.1%) cases, one (0.5%) case, and one (0.5%) case with use of the tiny, small, and medium ROIs, respectively. With use of the tiny, small, and medium ROIs, misdiagnosis rates would be 2.3%, 0.5%, and 0.5%, respectively, at a threshold of -15 HU or lower and 1.8%, 0%, and 0%, respectively, at a threshold of -20 HU or lower. Areas under the ROC curve for the nonenhanced phase images (range, 0.874-0.889) were superior to those for the nephrographic phase images (range, 0.790-0.826). CONCLUSION: Nonenhanced CT images were superior to nephrographic phase CT images for the diagnosis of AML. An attenuation threshold of -10 HU or lower with an ROI of at least 19-24 mm(2) is optimal for the diagnosis of AML. This threshold is not accurate with use of smaller (8-13-mm(2)) ROIs.

Effect of organ enhancement and habitus on estimation of unenhanced attenuation at contrast-enhanced dual-energy MDCT: concepts for individualized and organ-specific spectral iodine subtraction strategies.

OBJECTIVE: The purpose of this study was to assess whether habitus and organ enhancement influence iodine subtraction and should be incorporated into spectral subtraction algorithms. SUBJECTS AND METHODS: This study included 171 patients. In the unenhanced phase, MDCT was performed with single-energy acquisition (120 kVp, 250 mAs) and in the parenchymal phase with dual-energy acquisitions (80 kVp, 499 mAs; 140 kVp, 126 mAs). Habitus was determined by measuring trunk diameters and calculating circumference. Iodine subtraction was performed with input parameters individualized to muscle, fat, and blood ratio. Attenuation of the liver, pancreas, spleen, kidneys, and aorta was assessed in truly and virtually unenhanced image series. Pearson analysis was performed to correlate habitus with the input parameters. Analysis of truly unenhanced and virtually unenhanced images was performed with the Student t test; magnitude of variation was evaluated with Bland-Altman plots. Correction strategies were derived from organ-specific regression analysis of scatterplots of truly unenhanced and virtually unenhanced attenuation and implemented in a pixel-by-pixel approach. Analysis of individual organ correction and truly unenhanced attenuation was performed with the Student t test. RESULTS: The correlations between habitus and blood ratio (r = 0.694) and attenuation variation of fat at 80 kVp (r = -0.468) and 140 kV (r = -0.454) were confirmed. Although overall mean attenuation differed by no more than 10 HU between truly and virtually unenhanced scans overall, these differences varied by organ and were large in individual patients. Paired comparisons of truly and virtually unenhanced measurements differed significantly for liver, spleen, pancreas, kidneys, and aortic blood pool (p < 0.001 for all comparisons), but paired comparisons of truly unenhanced and individually organ-corrected measurements did not differ when organ- and habitus-based correction strategies were applied (p > 0.38 for all comparisons). CONCLUSION: Habitus and organ enhancement influence virtually unenhanced imaging and should be incorporated into spectral subtraction algorithms.