A Randomized Trial Comparing Antibiotics with Appendectomy for Appendicitis.

BACKGROUND: Antibiotic therapy has been proposed as an alternative to surgery for the treatment of appendicitis. METHODS: We conducted a pragmatic, nonblinded, noninferiority, randomized trial comparing antibiotic therapy (10-day course) with appendectomy in patients with appendicitis at 25 U.S. centers. The primary outcome was 30-day health status, as assessed with the European Quality of Life-5 Dimensions (EQ-5D) questionnaire (scores range from 0 to 1, with higher scores indicating better health status; noninferiority margin, 0.05 points). Secondary outcomes included appendectomy in the antibiotics group and complications through 90 days; analyses were prespecified in subgroups defined according to the presence or absence of an appendicolith. RESULTS: In total, 1552 adults (414 with an appendicolith) underwent randomization; 776 were assigned to receive antibiotics (47% of whom were not hospitalized for the index treatment) and 776 to undergo appendectomy (96% of whom underwent a laparoscopic procedure). Antibiotics were noninferior to appendectomy on the basis of 30-day EQ-5D scores (mean difference, 0.01 points; 95% confidence interval [CI], -0.001 to 0.03). In the antibiotics group, 29% had undergone appendectomy by 90 days, including 41% of those with an appendicolith and 25% of those without an appendicolith. Complications were more common in the antibiotics group than in the appendectomy group (8.1 vs. 3.5 per 100 participants; rate ratio, 2.28; 95% CI, 1.30 to 3.98); the higher rate in the antibiotics group could be attributed to those with an appendicolith (20.2 vs. 3.6 per 100 participants; rate ratio, 5.69; 95% CI, 2.11 to 15.38) and not to those without an appendicolith (3.7 vs. 3.5 per 100 participants; rate ratio, 1.05; 95% CI, 0.45 to 2.43). The rate of serious adverse events was 4.0 per 100 participants in the antibiotics group and 3.0 per 100 participants in the appendectomy group (rate ratio, 1.29; 95% CI, 0.67 to 2.50). CONCLUSIONS: For the treatment of appendicitis, antibiotics were noninferior to appendectomy on the basis of results of a standard health-status measure. In the antibiotics group, nearly 3 in 10 participants had undergone appendectomy by 90 days. Participants with an appendicolith were at a higher risk for appendectomy and for complications than those without an appendicolith. (Funded by the Patient-Centered Outcomes Research Institute; CODA ClinicalTrials.gov number, NCT02800785.).

Intraoperative cholangiography: a stepping stone to streamlining the treatment of choledocholithiasis.

BACKGROUND: An estimated 8-15% of patients undergoing cholecystectomy have concomitant common bile duct stones. In this 14-year study, we utilize data of patients at a high-volume tertiary care academic center and compare the clinical outcomes of patients undergoing intraoperative cholangiography (IOC) and endoscopic retrograde pancreatography (ERCP). METHODS: The charts of 1715 patients in the institutional NSQIP database who underwent cholecystectomy between October 1st, 2005 and September 30th, 2019 were retrospectively reviewed. Patients who underwent cholecystectomy in relation to a malignancy diagnosis or who underwent an ERCP in a different index hospitalization were excluded. Main outcomes included hospital length of stay (LOS), post-operative morbidity, and rate of readmissions. RESULTS: Of the 1409 patients included in the final analysis, 185 patients underwent ERCP, while 95 patients underwent IOC. Use of IOC compared to preoperative ERCP resulted in a shorter LOS (2.6 vs. 5.3 days, p < 0.001), lower rate of readmission (1.1% vs. 6.5%, p = 0.040), and similar rates of post-operative complications. Mean operative time increased by only 15 min in the IOC compared to the ERCP group (129 vs.114 min, p = 0.047). Additional variables that increased LOS on multivariable logistic regression included age, ASA classification, post-operative complications, and increased number of preoperative tests. CONCLUSIONS: This study demonstrates that use of IOC during cholecystectomy results in shorter LOS and fewer readmissions compared to ERCP. Future studies comparing these two approaches should focus on patient randomization, a cost-effectiveness analysis, and identifying barriers to implementation of a one-stage approach in the management of suspected choledocholithiasis.

Novel Method Suggests Global Superiority of Short-Duration Antibiotics for Intra-abdominal Infections.

Desirability of outcome ranking and response adjusted for duration of antibiotic risk (DOOR/RADAR) are novel and innovative methods of evaluating data in antibiotic trials. We analyzed data from a noninferiority trial of short-course antimicrobial therapy for intra-abdominal infection (STOP-IT), and results suggest global superiority of short-duration therapy for intra-abdominal infections.

Quantifying the Prognostic Value of Preoperative Surgeon Intuition: Comparing Surgeon Intuition and Clinical Risk Prediction as Derived from the American College of Surgeons NSQIP Risk Calculator.

BACKGROUND: Surgical risk prediction models traditionally use patient attributes and measures of physiology to generate predictions about postoperative outcomes. However, the surgeon's assessment of the patient may be a valuable predictor, given the surgeon's ability to detect and incorporate factors that existing models cannot capture. We compare the predictive utility of surgeon intuition and a risk calculator derived from the American College of Surgeons (ACS) NSQIP. STUDY DESIGN: From January 10, 2021 to January 9, 2022, surgeons were surveyed immediately before performing surgery to assess their perception of a patient's risk of developing any postoperative complication. Clinical data were abstracted from ACS NSQIP. Both sources of data were independently used to build models to predict the likelihood of a patient experiencing any 30-day postoperative complication as defined by ACS NSQIP. RESULTS: Preoperative surgeon assessment was obtained for 216 patients. NSQIP data were available for 9,182 patients who underwent general surgery (January 1, 2017 to January 9, 2022). A binomial regression model trained on clinical data alone had an area under the receiver operating characteristic curve (AUC) of 0.83 (95% CI 0.80 to 0.85) in predicting any complication. A model trained on only preoperative surgeon intuition had an AUC of 0.70 (95% CI 0.63 to 0.78). A model trained on surgeon intuition and a subset of clinical predictors had an AUC of 0.83 (95% CI 0.77 to 0.89). CONCLUSIONS: Preoperative surgeon intuition alone is an independent predictor of patient outcomes; however, a risk calculator derived from ACS NSQIP is a more robust predictor of postoperative complication. Combining intuition and clinical data did not strengthen prediction.

Trial Participation and Outcomes Among English-Speaking and Spanish-Speaking Patients With Appendicitis Randomized to Antibiotics: A Secondary Analysis of the CODA Randomized Clinical Trial.

Importance: Spanish-speaking participants are underrepresented in clinical trials, limiting study generalizability and contributing to ongoing health inequity. The Comparison of Outcomes of Antibiotic Drugs and Appendectomy (CODA) trial intentionally included Spanish-speaking participants. Objective: To describe trial participation and compare clinical and patient-reported outcomes among Spanish-speaking and English-speaking participants with acute appendicitis randomized to antibiotics. Design, Setting, and Participants: This study is a secondary analysis of the CODA trial, a pragmatic randomized trial comparing antibiotic therapy with appendectomy in adult patients with imaging-confirmed appendicitis enrolled at 25 centers across the US from May 1, 2016, to February 28, 2020. The trial was conducted in English and Spanish. All 776 participants randomized to antibiotics are included in this analysis. The data were analyzed from November 15, 2021, through August 24, 2022. Intervention: Randomization to a 10-day course of antibiotics or appendectomy. Main Outcomes and Measures: Trial participation, European Quality of Life-5 Dimensions (EQ-5D) questionnaire scores (higher scores indicating a better health status), rate of appendectomy, treatment satisfaction, decisional regret, and days of work missed. Outcomes are also reported for a subset of participants that were recruited from the 5 sites with a large proportion of Spanish-speaking participants. Results: Among eligible patients 476 of 1050 Spanish speakers (45%) and 1076 of 3982 of English speakers (27%) consented, comprising the 1552 participants who underwent 1:1 randomization (mean age, 38.0 years; 976 male [63%]). Of the 776 participants randomized to antibiotics, 238 were Spanish speaking (31%). Among Spanish speakers randomized to antibiotics, the rate of appendectomy was 22% (95% CI, 17%-28%) at 30 days and 45% (95% CI, 38%-52%) at 1 year, while in English speakers, these rates were 20% (95% CI, 16%-23%) at 30 days and 42% (95% CI 38%-47%) at 1 year. Mean EQ-5D scores were 0.93 (95% CI, 0.92-0.95) among Spanish speakers and 0.92 (95% CI, 0.91-0.93) among English speakers. Symptom resolution at 30 days was reported by 68% (95% CI, 61%-74%) of Spanish speakers and 69% (95% CI, 64%-73%) of English speakers. Spanish speakers missed 6.69 (95% CI, 5.51-7.87) days of work on average, while English speakers missed 3.76 (95% CI, 3.20-4.32) days. Presentation to the emergency department or urgent care, hospitalization, treatment dissatisfaction, and decisional regret were low for both groups. Conclusions and Relevance: A high proportion of Spanish speakers participated in the CODA trial. Clinical and most patient-reported outcomes were similar for English- and Spanish-speaking participants treated with antibiotics. Spanish speakers reported more days of missed work. Trial Registration: ClinicalTrials.gov Identifier: NCT02800785.

Estimating three synaptic conductances in a stochastic neural model.

We present a method for the reconstruction of three stimulus-evoked time-varying synaptic input conductances from voltage recordings. Our approach is based on exploiting the stochastic nature of synaptic conductances and membrane voltage. Starting with the assumption that the variances of the conductances are known, we use a stochastic differential equation to model dynamics of membrane potential and derive equations for first and second moments that can be solved to find conductances. We successfully apply the new reconstruction method to simulated data. We also explore the robustness of the method as the assumptions of the underlying model are relaxed. We vary the noise levels, the reversal potentials, the number of stimulus repetitions, and the accuracy of conductance variance estimation to quantify the robustness of reconstruction. These studies pave the way for the application of the method to experimental data.

The Effect of Anticoagulation and Antiplatelet Use in Trauma Patients on Mortality and Length of Stay.

BACKGROUND: Though many trauma patients are on anticoagulation or antiplatelet therapy (AAT), there are few generalizable data on the risks for these patients. The purpose of this study was to analyze the impact of anticoagulation (AC) and antiplatelet (AP) therapy on mortality and length of stay (LOS) in general trauma patients. METHODS: A retrospective review was performed of patients in the institutional trauma registry during 2019 to determine AAT use on admission and discharge. Outcomes were compared using standard statistics. RESULTS: Of 2261 patients who met the inclusion criteria, 2 were excluded due to an incomplete medication reconciliation, resulting in 2259 patients. Patients on AAT had a higher mortality (4.5% vs 2.1%). On multivariable analysis, preadmission AC (odds ratio OR, 3.325, P = .001), age (OR 1.040, P < .001), and injury severity score ((ISS) 1.094, P < .001) were associated with mortality. Anticoagulation use was also associated with longer LOS on multivariable analysis (OR: 1.626, P = .005). Antiplatelet use was not associated with higher mortality or longer LOS. More patients on AAT were unable to be discharged home. However, patients on AAT did not have a greater blood transfusion requirement or need more hemorrhage control procedures. Lastly, 23.7% of patients on preadmission AAT were not discharged on any AAT. DISCUSSION: These data demonstrate that patients on AC, but not AP, have greater mortality and longer hospital LOS. This may provide guidance for those being newly started on AAT. Further work to determine which patients benefit most from restarting AAT would lead to improvement in the care of trauma patients.

Self-selection vs Randomized Assignment of Treatment for Appendicitis.

Importance: For adults with appendicitis, several randomized clinical trials have demonstrated that antibiotics are an effective alternative to appendectomy. However, it remains unknown how the characteristics of patients in such trials compare with those of patients who select their treatment and whether outcomes differ. Objective: To compare participants in the Comparison of Outcomes of Antibiotic Drugs and Appendectomy (CODA) randomized clinical trial (RCT) with a parallel cohort study of participants who declined randomization and self-selected treatment. Design, Setting, and Participants: The CODA trial was conducted in 25 US medical centers. Participants were enrolled between May 3, 2016, and February 5, 2020; all participants were eligible for at least 1 year of follow-up, with all follow-up ending in 2021. The randomized cohort included 1094 adults with appendicitis; the self-selection cohort included patients who declined participation in the randomized group, of whom 253 selected appendectomy and 257 selected antibiotics. In this secondary analysis, characteristics and outcomes in both self-selection and randomized cohorts are described with an exploratory analysis of cohort status and receipt of appendectomy. Interventions: Appendectomy vs antibiotics. Main Outcomes and Measures: Characteristics among participants randomized to either appendectomy or antibiotics were compared with those of participants who selected their own treatment. Results: Clinical characteristics were similar across the self-selection cohort (510 patients; mean age, 35.8 years [95% CI, 34.5-37.1]; 218 female [43%; 95% CI, 39%-47%]) and the randomized group (1094 patients; mean age, 38.2 years [95% CI, 37.4-39.0]; 386 female [35%; 95% CI, 33%-38%]). Compared with the randomized group, those in the self-selection cohort were less often Spanish speaking (n = 99 [19%; 95% CI, 16%-23%] vs n = 336 [31%; 95% CI, 28%-34%]), reported more formal education (some college or more, n = 355 [72%; 95% CI, 68%-76%] vs n = 674 [63%; 95% CI, 60%-65%]), and more often had commercial insurance (n = 259 [53%; 95% CI, 48%-57%] vs n = 486 [45%; 95% CI, 42%-48%]). Most outcomes were similar between the self-selection and randomized cohorts. The number of patients undergoing appendectomy by 30 days was 38 (15.3%; 95% CI, 10.7%-19.7%) among those selecting antibiotics and 155 (19.2%; 95% CI, 15.9%-22.5%) in those who were randomized to antibiotics (difference, 3.9%; 95% CI, -1.7% to 9.5%). Differences in the rate of appendectomy were primarily observed in the non-appendicolith subgroup. Conclusions and Relevance: This secondary analysis of the CODA RCT found substantially similar outcomes across the randomized and self-selection cohorts, suggesting that the randomized trial results are generalizable to the community at large. Trial Registration: ClinicalTrials.gov Identifier: NCT02800785.

Patient Factors Associated With Appendectomy Within 30 Days of Initiating Antibiotic Treatment for Appendicitis.

IMPORTANCE: Use of antibiotics for the treatment of appendicitis is safe and has been found to be noninferior to appendectomy based on self-reported health status at 30 days. Identifying patient characteristics associated with a greater likelihood of appendectomy within 30 days in those who initiate antibiotics could support more individualized decision-making. OBJECTIVE: To assess patient factors associated with undergoing appendectomy within 30 days of initiating antibiotics for appendicitis. DESIGN, SETTING, AND PARTICIPANTS: In this cohort study using data from the Comparison of Outcomes of Antibiotic Drugs and Appendectomy (CODA) randomized clinical trial, characteristics among patients who initiated antibiotics were compared between those who did and did not undergo appendectomy within 30 days. The study was conducted at 25 US medical centers; participants were enrolled between May 3, 2016, and February 5, 2020. A total of 1552 participants with acute appendicitis were randomized to antibiotics (776 participants) or appendectomy (776 participants). Data were analyzed from September 2020 to July 2021. EXPOSURES: Appendectomy vs antibiotics. MAIN OUTCOMES AND MEASURES: Conditional logistic regression models were fit to estimate associations between specific patient factors and the odds of undergoing appendectomy within 30 days after initiating antibiotics. A sensitivity analysis was performed excluding participants who underwent appendectomy within 30 days for nonclinical reasons. RESULTS: Of 776 participants initiating antibiotics (mean [SD] age, 38.3 [13.4] years; 286 [37%] women and 490 [63%] men), 735 participants had 30-day outcomes, including 154 participants (21%) who underwent appendectomy within 30 days. After adjustment for other factors, female sex (odds ratio [OR], 1.53; 95% CI, 1.01-2.31), radiographic finding of wider appendiceal diameter (OR per 1-mm increase, 1.09; 95% CI, 1.00-1.18), and presence of appendicolith (OR, 1.99; 95% CI, 1.28-3.10) were associated with increased odds of undergoing appendectomy within 30 days. Characteristics that are often associated with increased risk of complications (eg, advanced age, comorbid conditions) and those clinicians often use to describe appendicitis severity (eg, fever: OR, 1.28; 95% CI, 0.82-1.98) were not associated with odds of 30-day appendectomy. The sensitivity analysis limited to appendectomies performed for clinical reasons provided similar results regarding appendicolith (adjusted OR, 2.41; 95% CI, 1.49-3.91). CONCLUSIONS AND RELEVANCE: This cohort study found that presence of an appendicolith was associated with a nearly 2-fold increased risk of undergoing appendectomy within 30 days of initiating antibiotics. Clinical characteristics often used to describe severity of appendicitis were not associated with odds of 30-day appendectomy. This information may help guide more individualized decision-making for people with appendicitis.

The effect of anticoagulation on outcomes after liver and spleen injuries: A research consortium of New England centers for trauma (ReCONECT) study.

BACKGROUND: Liver and spleen injuries are the most commonly injured solid organs, the effects of anticoagulation on these injuries has not yet been well characterized. STUDY DESIGN: Multicenter retrospective study. RESULT: During the 4-year study period, 1254 patients, 64 (5%) on anticoagulation (AC), were admitted with liver and/or splenic injury. 58% of patients had a splenic injury, 53% had a liver injury and 11% had both. Patients on AC were older than non-AC patients (mean age 60.9 vs. 38.6 years, p < 0.001). The most common AC drug was warfarin (70%) with atrial fibrillation (47%) the most common indication for AC. There was no significant difference in AAST injury grade between AC and non-AC patients (median grade 2), but AC patients required a blood product transfusion more commonly (58 vs 40%, p = 0.007) particularly FFP (4 vs 19%, p < 0.01). Among those transfused, non-AC patients required slightly more PRBC (5.7 vs 3.8 units, p = 0.018) but similar amount of FFP (3.2 vs 3.1 units, p = 0.92). The two groups had no significant difference in the rates of initial non-operative management (50% (AC) vs 56% (non-AC), p = 0.3)) or failure of non-operative management (7 vs 4%, p = 0.16). AC patients were more likely to be managed initially with angiography (36 vs 20%, p = 0.001) while non-AC patients with surgery (24% vs 13%, p = 0.04). There was no significant difference in LOS and mortality. CONCLUSION: The use of anticoagulation did not result in a difference in outcomes among patients with spleen and/or liver injuries.

Cervical spine MRI in patients with negative CT: A prospective, multicenter study of the Research Consortium of New England Centers for Trauma (ReCONECT).

BACKGROUND: Although cervical spine CT (CSCT) accurately detects bony injuries, it may not identify all soft tissue injuries. Although some clinicians rely exclusively on a negative CT to remove spine precautions in unevaluable patients or patients with cervicalgia, others use MRI for that purpose. The objective of this study was to determine the rates of abnormal MRI after a negative CSCT. METHODS: Blunt trauma patients who either were unevaluable or had persistent midline cervicalgia and underwent an MRI of the C-spine after a negative CSCT were enrolled prospectively in eight Level I and II New England trauma centers. Demographics, injury patterns, CT and MRI results, and any changes in cervical spine management as a result of MRI imaging were recorded. RESULTS: A total of 767 patients had MRI because of cervicalgia (43.0%), inability to evaluate (44.1%), or both (9.4%). MRI was abnormal in 23.6% of all patients, including ligamentous injury (16.6%), soft tissue swelling (4.3%), vertebral disc injury (1.4%), and dural hematomas (1.3%). Rates of abnormal neurological signs or symptoms were not different among patients with normal versus abnormal MRI. (15.2 vs. 18.8%, p = 0.25). The c-collar was removed in 88.1% of patients with normal MRI and 13.3% of patients with an abnormal MRI. No patient required halo placement, but 11 patients underwent cervical spine surgery after the MRI results. Six of the eleven had neurological signs or symptoms. CONCLUSIONS: In a select population of patients, MRI identified additional injuries in 23.6% of patients despite a normal CSCT. It is uncertain if this is a true limitation of CT technology or represents subtle injuries missed in the interpretation of the scan. The clinical significance of these abnormal MRI findings cannot be determined from this study group. LEVEL OF EVIDENCE: Therapeutic study, level IV.

Lithopedion presenting as intra-abdominal abscess and fecal fistula: report of a case and review of the literature.

A rare case of unrecognized and long-standing lithopedion ("stone baby") with erosion into the bowel with fecal fistula formation is described. A literature review is also presented.

Diabetes insipidus uncovered during conservative management of complicated acute appendicitis.

Diabetes insipidus (DI) arises from impaired function of antidiuretic hormone, characterized by hypovolemia, hypernatremia, polyuria, and polydipsia. This case is a reminder of the rare but challenging obstacle that undiagnosed DI poses in fasting surgical patients, requiring prompt recognition and vigilant management of marked homeostatic imbalances.

Extremes of shock index predicts death in trauma patients.

CONTEXT: We noted a bimodal relationship between mortality and shock index (SI), the ratio of heart rate to systolic blood pressure. AIMS: To determine if extremes of SI can predict mortality in trauma patients. SETTINGS AND DESIGNS: Retrospective evaluation of adult trauma patients at a tertiary care center from 2000 to 2012 in the United States. MATERIALS AND METHODS: We examined the SI in trauma patients and determined the adjusted mortality for patients with and without head injuries. STATISTICAL ANALYSIS USED: Descriptive statistics and multivariable logistic regression. RESULTS: SI values demonstrated a U-shaped relationship with mortality. Compared with patients with a SI between 0.5 and 0.7, patients with a SI of <0.3 had an odds ratio for death of 2.2 (95% confidence interval [CI] 21.2-4.1) after adjustment for age, Glasgow Coma score, and injury severity score while patients with SI >1.3 had an odds ratio of death of 3.1. (95% CI 1.6-5.9). Elevated SI is associated with increased mortality in patients with isolated torso injuries, and is associated with death at both low and high values in patients with head injury. CONCLUSION: Our data indicate a bimodal relationship between SI and mortality in head injured patients that persists after correction for various co-factors. The distribution of mortality is different between head injured patients and patients without head injuries. Elevated SI predicts death in all trauma patients, but low SI values only predict death in head injured patients.

Needs assessment for a focused radiology curriculum in surgical residency: a multicenter study.

BACKGROUND: Patient instability and limited radiology staffing may compel surgeons to make clinical decisions based on their independent interpretations of imaging studies. Despite potential implications for patients, no research to date has assessed the need for a diagnostic radiology curriculum in general surgery residency. METHODS: We performed a cross-sectional study of surgery faculty and residents at 13 teaching hospitals across the United States. Survey responses were summarized using frequency and percentage, and analyzed by chi-square, Mantel-Haenszel chi-square, and McNemar tests. RESULTS: Surveys were distributed to 465 faculty and 520 residents, with response rates of 26% and 30%, respectively. Most respondents reported making decisions based on their independent imaging interpretation at least sometimes, with higher frequency in acute scenarios. The majority voiced a need for a dedicated radiology curriculum, with teaching in chest x-rays, abdominal x-rays, abdominal computed tomography, chest computed tomography, and focused assessment with sonography in trauma examinations. CONCLUSIONS: Surgeons and surgical residents enact treatment plans based on their independent interpretation of imaging studies, especially during acute patient scenarios. Further curricular development efforts are warranted to ensure trainee accuracy in radiologic interpretation.

The rate of adenocarcinoma in endoscopically removed colorectal polyps.

The purpose of this study was to determine the rate of cancer in a modern series of colorectal polyps. All pathology reports from colon and rectal polyps from 1999 to 2002 were reviewed. Reports of bowel resections, cancer-free polyps, and polyp-free mucosal biopsies were excluded. Polyps were grouped by size, and the rate of adenocarcinoma was determined. x2 was used for analysis. A total of 4,443 polyps were found, of which 3,225 were adenomatous [2,883 (89.4%) tubular adenomas, 399 (9.3%) tubulo-villous adenomas, 32 (1.0%) villous adenomas, and 11 (0.3%) carcinomas]. The rate of adenocarcinoma by size was 0.07 per cent for polyps <1 cm, 2.41 per cent for polyps 1-2 cm, and 19.35 per cent for polyps >2 cm, representing significantly fewer cancers for each category of polyp size than the accepted standard. The rate of carcinoma in colon polyps is much lower than previously thought and currently stated in many texts. These data do not alter the recommendations for polyp removal, however, failure to retrieve a specimen in a polyp <1 cm in size is unlikely to have an adverse outcome because the chances of malignancy are very low.

Evidence-based medicine applied to sentinel lymph node biopsy in patients with breast cancer.

Sentinel lymph node biopsy (SLNB) has not been examined using the principles of evidence-based medicine (EBM). Specifically, likelihood ratios have not been used to assess the validity of SLNB. The Surveillance, Epidemiology, and End Results (SEER) public database of the National Cancer Institute was used to establish the baseline or pretest probability of finding a positive lymph axillary node for each stage of breast cancer. Rates of false negative results of SLNB for all breast cancer stages were determined from the surgical literature. Positive and negative likelihood ratios (LR) were calculated. For each stage of breast cancer, the Bayesian nomogram was used to find the post-test probability of missing a metastatic axillary node when the SLN was negative. The SEER database of 213,292 female patients with breast cancer yielded the following rates of positivity of axillary lymph nodes for each breast tumor size: T1a, 7.8 per cent; T1b, 13.3 per cent; T1c, 28.5 per cent; T2, 50.2 per cent; T3, 70.1 per cent. The combined data from 13 published studies of SLNB (6444 successful SLNBs) demonstrated a false negative rate of 8.5 per cent. The LR of a negative test is 0.086. According to the nomogram, the chances of missing a positive node for stage of cancer are as follows: T1a, 0.7 per cent; T1b, 1.5 per cent; T1c, 3.0 per cent; T2, 7 per cent; T3, 18 per cent. The risk of missing a positive axillary node can accurately be estimated for each stage of breast cancer using the LR, which is much more useful than the simple false negative rate. Surgeons should use this information when deciding whether to perform SLNB and in their informed consent discussions.