Twenty-year perspective on blunt traumatic diaphragmatic injury in level 1 trauma centre: Early versus delayed diagnosis injury patterns and outcomes.

OBJECTIVE: Blunt traumatic diaphragmatic injury (TDI) is typically associated with severe trauma and concomitant injuries. It is a diagnostic challenge in the setting of blunt trauma and can be easily overlooked especially in the acute phase often dominated by concurrent injuries. METHODS: A retrospective review was conducted of patients with blunt-TDI identified from a level 1 trauma registry. Variables associated with early versus delayed diagnosis as well as non-survivor and survivor groups were collected to examine factors associated with delayed diagnosis. RESULTS: A total of 155 patients were included (mean age 46 ± 20, 60.6% male). Diagnosis was made <24 h in 126 (81.3%), and >24 h in 29 (18.7%). Of the delayed diagnosis group, 14 (48%) were diagnosed >7 days. Overall, 27 (21.4%) patients had a diagnostic initial CXR and 64 (50.8%) had a diagnostic initial CT. Fifty-eight (37.4%) patients were diagnosed intraoperatively. Of the delayed diagnosis group, 22 (75.9%) had no initial signs on CXR or CT, 15 (52%) of this group had persistent pleural-effusions/elevated-hemidiaphragm leading to further investigation and diagnosis. No significant difference in survival was observed between early and delayed diagnoses, no clinically significant injury patterns to predict delayed diagnoses were noted. CONCLUSION: The diagnosis of TDI is challenging. Without frank signs of herniation of abdominal contents on CXR or CT, the diagnosis is often not made on initial imaging. In patients with the evidence of blunt traumatic injury in the lower-chest/upper-abdomen, a high degree of clinical suspicion should be held and follow-up CXRs/CTs arranged.

Artificial Intelligence for Pre-operative Diagnosis of Malignant Thyroid Nodules Based on Sonographic Features and Cytology Category.

BACKGROUND: Current diagnosis and classification of thyroid nodules are susceptible to subjective factors. Despite widespread use of ultrasonography (USG) and fine needle aspiration cytology (FNAC) to assess thyroid nodules, the interpretation of results is nuanced and requires specialist endocrine surgery input. Using readily available pre-operative data, the aims of this study were to develop artificial intelligence (AI) models to classify nodules into likely benign or malignant and to compare the diagnostic performance of the models. METHODS: Patients undergoing surgery for thyroid nodules between 2010 and 2020 were recruited from our institution's database into training and testing groups. Demographics, serum TSH level, cytology, ultrasonography features and histopathology data were extracted. The training group USG images were re-reviewed by a study radiologist experienced in thyroid USG, who reported the relevant features and supplemented with data extracted from existing reports to reduce sampling bias. Testing group USG features were extracted solely from existing reports to reflect real-life practice of a non-thyroid specialist. We developed four AI models based on classification algorithms (k-Nearest Neighbour, Support Vector Machine, Decision Tree, Naïve Bayes) and evaluated their diagnostic performance of thyroid malignancy. RESULTS: In the training group (n = 857), 75% were female and 27% of cases were malignant. The testing group (n = 198) consisted of 77% females and 17% malignant cases. Mean age was 54.7 ± 16.2 years for the training group and 50.1 ± 17.4 years for the testing group. Following validation with the testing group, support vector machine classifier was found to perform best in predicting final histopathology with an accuracy of 89%, sensitivity 89%, specificity 83%, F-score 94% and AUROC 0.86. CONCLUSION: We have developed a first of its kind, pilot AI model that can accurately predict malignancy in thyroid nodules using USG features, FNAC, demographics and serum TSH. There is potential for a model like this to be used as a decision support tool in under-resourced areas as well as by non-thyroid specialists.

Cancer in thyroglossal duct cysts.

BACKGROUND: Thyroglossal duct cysts (TDC) account for 7% of midline neck swellings. TDC carcinoma (TDCC) is rare, reported in 1% of all TDCs. We aimed to describe the incidence of TDCC, the accuracy of fine needle aspiration cytology (FNAC), and to identify suspicious, predictive ultrasound (USG) features. METHOD: A cross sectional study of TDC patients in the Monash University Endocrine Surgery Database from 2001 to 2021. RESULTS: Eighty-six patients had surgery for TDC, of median age 48 and a female preponderance (62%). Preoperative USG was used in 85% and FNAC in 57%. There were six cases (7%) of TDCC with papillary thyroid cancer (PTC). USG in five TDCC cases showed a solid nodule within the cyst wall. FNAC was undertaken in five TDCC cases from the solid nodule; malignant in one and suspicious for malignancy in two. Two TDCC patients had concurrent total thyroidectomy (TT), and three subsequently had a TT. Multifocal thyroid PTC was found in two patients. One patient had a recurrence in the lateral lymph nodes, nine years after excision of the TDCC and TT. All patients are alive and well with no distant metastases (median follow up 11 years). CONCLUSION: The 7% incidence of TDCC is higher than the usually reported 1% in the literature. We recommend a preoperative USG to evaluate the TDC, thyroid gland and cervical lymph nodes, and an FNAC to target the solid component of the TDC, and favour total thyroidectomy for all patients with TDCC.

ECMO (extra corporeal membrane oxygenation) in major trauma: A 10 year single centre experience.

Aim To review the indications, complications and outcomes of extracorporeal membrane oxygenation (ECMO) in major trauma patients. Methods Single centre, retrospective, cohort study. Results Over a ten year period, from 13,420 major trauma patients, 11 were identified from our institutional trauma registry as having received ECMO. These patients were predominantly younger (mean 39 +/- 17 years), male (91%) and severely traumatised (median ISS 50, IQR 34 - 54). Veno-venous (VV) ECMO was used predominantly (n = 7, 64%), to treat hypoxic respiratory failure (mean PaO2/FiO2 ratio 69.7 +/- 38.6), secondary to traumatic lung injury. Veno-arterial (VA) ECMO was used less frequently, primarily to treat massive pulmonary embolism following trauma. Major bleeding complications occurred in four patients, however only one patient died from haemorrhage. Heparin free (2/11), delayed (3/11) or low dose heparin (2/11) therapy was frequently utilised. The median time from injury to ECMO initiation was 1 day (IQR 0.5 - 5.5) and median ECMO duration 9 days (IQR 6.5 - 10.5). ECMO was initiated <72 hours in 6 patients, with survival to discharge 67%, compared to 20% in those initiated >72 hours. Overall survival to discharge was 45%, and was higher with VV ECMO (64%), than other configurations (25%). Conclusion ECMO was rarely used in major trauma, the most common indication being severe hypoxaemic respiratory failure secondary to lung injury. In this severely injured cohort, overall survival was poor but better in VV compared to VA and better if initiated early (<72 hours), compared to late.

Investigation of recurrent laryngeal palsy rates for potential associations during thyroidectomy.

BACKGROUND: There are many clinical associations and potential mechanisms of injury resulting in recurrent laryngeal nerve palsy (RLNP) after thyroidectomy. One possible cause of RLNP is focal intralaryngeal compression of the recurrent laryngeal nerve (RLN), which may be associated with the tracheal tube (TT). Therefore, we examined current RLNP rates to investigate potential associations, including intralaryngeal, airway, anaesthetic and anthropometric factors. METHODS: We analysed 1003 patients undergoing thyroid surgery at The Alfred from 2010 to 2017, who had anatomically intact RLNs at the conclusion of thyroidectomy. All included patients underwent pre- and post-operative flexible nasendoscopy. The primary outcome was RLNP rate. We analysed potential associated factors including age, sex, operative time, surgical indication, pathology, American Society of Anaesthesiologists Physical Status, Mallampati scores, body mass index, intubation grade, TT size and specimen weight. The independent risk factors were identified by logistic regression analysis. RESULTS: Overall, RLNP occurred in 83 patients (8.3%) of which one was permanent (0.1%). On univariate analysis, RLNP was associated with male sex (P = 0.02), and duration of surgery (P = 0.002). On multivariate analysis, both male sex (P = 0.047) and duration of surgery (P = 0.04) remained significant. Further, factors postulated to cause intralaryngeal compression of the RLN, including TT size, body mass index, intubation grade and Mallampati score, were not significantly associated with RLNP. CONCLUSION: Our study showed a RLNP rate of 8.3%, and associations with longer operative duration, and male sex. Potential intralaryngeal factors were not identified.

Emergency department resuscitative thoracotomy at an adult major trauma centre: Outcomes following a training programme with standardised indications.

OBJECTIVE: The objective of this study was to report the procedural incidence and patient outcomes after the 2009 introduction of an institutional resuscitative thoracotomy (RT) programme. Emergency physicians, general surgeons and emergency nursing trauma team members were trained to perform RT on thoracic trauma patients with an unresponsive systolic blood pressure (SBP) <70 mmHg within 30 min of arrival, prior to cardiothoracic team back-up. METHODS: A retrospective cohort study was conducted on patients who underwent RT from 2009 to 2017. The primary outcome measures were the incidence of the procedure and patients' survival to hospital discharge. Variables associated with survival were assessed using univariable logistic regression analyses. RESULTS: There were 12 399 major trauma patients, including 7657 with major thoracic trauma and 315 presenting with SBP <70 mmHg. There were 32 RTs performed (incidence of 0.4%; 95% confidence interval [CI] 0.3-0.6) among patients with major thoracic trauma and 10.2% (99% CI 7.3-13.4) among patients with major thoracic trauma and SBP <70 mmHg. There were eight (25%; 95% CI 13.2-42.1) survivors to hospital discharge and no late mortality (mean follow-up 2.8 years). Survival was significantly associated with the procedure performed within 30 min of arrival (odds ratio 0.09; 95% CI 0.01-0.67) while mortality was associated with the procedure being performed in the setting of traumatic cardiac arrest (odds ratio 18.3; 95% CI 2.4-140.4). CONCLUSIONS: A formal training and credentialing programme was associated with a low incidence of the procedure, yet achieved a survival rate of 25%, which is comparable to other reported literature.

Feasibility study for implementation of resuscitative balloon occlusion of the aorta in peri-arrest, exsanguinating trauma at an adult level 1 Australian trauma centre.

OBJECTIVE: This prospective, observational, interventional study sought to determine if the introduction of resuscitative balloon occlusion of the aorta (REBOA) at an Australian adult major trauma centre would improve survival for major trauma patients. METHODS: Patients aged 18-60 years, transported directly from scene with exsanguinating, sub-diaphragmatic haemorrhage and hypovolaemic shock (systolic BP <70 mmHg or hypovolaemic cardiac arrest) were eligible for recruitment and followed up until hospital discharge (ACTRN12618000550202). RESULTS: During the 14-month study period (17 January 2015 to 12 March 2016) 3032 patients were admitted direct from scene with an overall mortality of 97 (3.71%). Of these patients 3019 had trauma centre vital signs recorded in the data set (99.57%) and 1523 were between the ages of 18-60, including 143 patients with a shock index of >1.0 (4.74%). There were 13 (0.43%) patients with a systolic BP <70 mmHg and/or cardiorespiratory arrest on arrival. The mortality in this group was six out of 13 (46.15%). Of these 13 patients, there were two (0.07% of the total cohort) where REBOA was attempted. There were no eligible patients for whom REBOA was achieved. None of the six patients who died would have benefited from REBOA deployment. CONCLUSIONS: Despite considerable training and resource allocation to ensure 24-h availability, the introduction of REBOA failed to effectively demonstrate any impact on patient outcome. Despite retrospective literature supporting the introduction of REBOA, in this 14-month prospective study there was no evidence of benefit. Further studies may define indications and subgroups of patients who may benefit.

Parathyroidectomy Without the Utilisation of iPTH: The Gold Standard is Still a Good Operation-How Understanding the Anatomy and a Simple US Can Help.

Parathyroid surgery is frequently performed after at least two preoperative localisation studies, in addition to the use of intraoperative ioPTH. The key to performing a successful parathyroidectomy is reliant on the surgeon having an outstanding knowledge of parathyroid embryology and anatomy. With this, it is possible to undertake surgery with a simple neck ultrasound and without more expensive pre- and intraoperative localisation studies.

Survival following traumatic thoracic compartment syndrome managed with VV-ECMO.

Whilst post-traumatic respiratory failure is the most common indication for use of VV-ECMO in trauma patients, its use in traumatic thoracic compartment syndrome is not yet well described. Thoracic compartment syndrome, a rare complication of thoracic trauma, occurs in the setting of chest wall injuries, impaired chest wall compliance, pulmonary contusions and subsequent high ventilatory pressures. This in turn impairs venous return and increases risk of circulatory arrest due to obstructive shock. This case study describes the successful use of VV-ECMO in a young male with thoracic compartment syndrome following severe blunt chest trauma sustained in a high speed motor vehicle crash. Following brief circulatory arrest, thoracic compartment syndrome was relieved during thoracotomy but reoccurred on chest closure. The use of VV-ECMO for oxygenation permitted lower ventilatory pressures, allowing venous return and primary closure of the thoracotomy. The patient subsequently had an excellent functional outcome. This case describes the successful use of VV-ECMO for a novel indication. The indications for ECMO in thoracic trauma patients continue to evolve.

Temporal analysis of thyroid cancer management in a Melbourne tertiary centre.

BACKGROUND: The American Thyroid Association (ATA) management guidelines for thyroid cancer were revised in 2009. The aim of this study was to determine if management of thyroid cancer in our institution has changed in accordance with the introduction of the revised ATA guidelines (ATA2009 ), and to compare the characteristics and management of thyroid cancer in a Melbourne endocrine surgery unit over a 7-year period. METHODS: All patients treated by the Monash University Endocrine Surgery Unit for thyroid cancer between 2007 and 2013 were divided into two groups - the pre-ATA2009 group (2007-2010) and the post-ATA2009 group (2011-2013). Comparisons were made of the demographics, cytology, pathology, surgical outcome and adjuvant therapy using t-test and chi-squared tests. RESULTS: There were 333 patients in the pre-ATA2009 group and 342 patients in the post-ATA2009 group. Fewer non-diagnostic fine-needle aspiration cytology results were identified in the post-ATA2009 group (4% versus 0.9%; P = 0.01), while the rates of other fine-needle aspiration cytology categories were similar. There was a reduction in the use of radioactive iodine ablation in the post-ATA2009 group, both in the proportion of patients being treated (66% versus 48%; P < 0.001) and the dosages used (mean 96 mCi versus 80 mCi; P < 0.01), despite similar tumour size in both groups. CONCLUSION: The key changes in practice thought to be attributable to the 2009 revised ATA guidelines were the reduction in the use and dosage of radioactive iodine in the management of differentiated thyroid cancer.

Thyroidectomy Then and Now: A 50-Year Australian Perspective.

BACKGROUND: Since the mid-1800s, thyroidectomy has transformed from a procedure associated with high to near-zero mortality. Nonetheless, surgeons must continue to strive to improve patient care. Using historical records and contemporary data, this study compares the practice and outcomes of thyroid surgery at a tertiary institution during two periods, 50 years apart. METHODS: 'The Alfred Hospital Clinical Reports' recorded all cases of surgically managed thyroid disease from 1946 to 1959. These historical cases were compared to contemporary thyroidectomy cases at the Alfred Hospital from 2007 to 2016. Cases were compared for surgical indication and post-operative outcomes. RESULTS: There were 746 patients in the historical group (mean age 53 years; 87% female) and 787 patients in the contemporary group (mean age 52 years; 80% female). The most common indication for thyroidectomy in both groups was non-toxic nodular goitre. A greater proportion of the contemporary group were diagnosed with thyroid malignancy (27% vs. 8%; p < 0.001). The contemporary group recorded significantly fewer cases of thyrotoxic crisis (2.1% vs. 0%; p = 0.001), permanent nerve palsy (4.6% vs. 0.4%; p < 0.001) and bilateral nerve palsy (1.2% vs. 0%; p = 0.01). There were no mortalities in the contemporary group, while the historical data recorded three deaths (0.44%). CONCLUSIONS: This study compared thyroid surgery in two cohorts separated by a 50-year period. While it is not surprising that outcomes of thyroidectomy have improved, this study uniquely demonstrates trends of thyroid surgery over time and areas in which further improvements may be made.

Total thyroidectomy for pressure symptoms in patients with Hashimoto's thyroiditis.

BACKGROUND: Hashimoto's thyroiditis (HT) is rarely on its own the indication for thyroidectomy. However, surgery in patients with HT will be undertaken when there is malignancy and may be required for pressure symptoms. Therefore, this study aimed to investigate the indications for surgery in HT patients. METHODS: The Monash University Endocrine Surgery Database was analysed from 1994 to 2013 for patients with HT. Patients with HT were compared to a similar group of patients with no HT on histopathology. Patient demographics, indication for surgery, histopathology, gland weight and complications were analysed. RESULTS: A total of 2346 patients underwent total thyroidectomy during the study period. The median age was 55 years. Eleven percent of patients had HT on final pathology (259/2346). HT patients reported more pressure symptoms, 25.5% compared to those with other pathology, 18.9% (P = 0.01). Patients with pressure symptoms had heavier glands, 113 g compared to 85 g in those with other indications for surgery (P = 0.048). Within the HT cohort, the median gland weight was 66 g compared to 93 g in those without HT (P < 0.01). On multivariate analysis, pressure symptoms as an indication for surgery was associated with HT (P < 0.01), but age, gender and gland weight were not associated. In patients operated for pressure with HT as the only pathology, 90% had relief of pressure symptoms. CONCLUSION: Patients with HT were more likely to have pressure symptoms as an indication for surgery independent of gland weights.

Surgery for parathyroid microadenomas: patient characteristics, localization success and operative cures.

BACKGROUND: In recent years, patients with primary hyperparathyroidism (PHPT) are being diagnosed earlier, with milder elevations in parathyroid hormone (PTH) and serum calcium. We aimed to investigate whether adenoma size reflects biochemical severity of presentation and influences localization of pre-operative scans. METHODS: A total of 630 consecutive patients undergoing parathyroidectomy for PHPT were recruited into either the microadenoma (≤200 mg) or macroadenoma (>200 mg) group. Pre-operative serum calcium, PTH, rates of minimally invasive parathyroidectomy and bilateral neck exploration, localization of adenomas with pre-operative ultrasound and sestamibi (MIBI) scans, cure rates and other demographic parameters were compared. The data were analysed using Student's t-test, Chi-squared test, linear and multiple regression analyses. RESULTS: Patients in the microadenoma group had significantly lower pre-operative serum calcium (P < 0.001) and PTH (P < 0.001), less accurate MIBI (P < 0.001) and ultrasound (P < 0.001), lower cure rates (P = 0.04) and were more likely to undergo bilateral neck exploration (P = 0.001). However, multivariate analysis revealed that microadenomas are most strongly associated with the findings of less accurate MIBI (P = 0.03) and lower pre-operative calcium (P = 0.04). CONCLUSION: In conclusion, smaller adenomas are strongly associated with biochemically milder PHPT and less accurate localization studies. Therefore, microadenomas continue to present as a challenge in both diagnosis and management.

Quantitative study of voice dysfunction after thyroidectomy.

BACKGROUND: Up to 80% of patients without a recurrent laryngeal nerve palsy report alteration in their voice after a thyroid procedure. The aims of this study were (1) to quantify voice changes after thyroid operation; (2) to correlate the changes to the extent of operation; and (3) to correlate voice changes to intraoperative recurrent laryngeal nerve swelling. METHODS: Patients undergoing total and hemithyroidectomy were recruited prospectively from the Monash University Endocrine Surgery Unit during a 12-month period. Voice quality was scored subjectively using the Voice Disorder Index (score 0-40, from best to worst) and objectively using the Dysphonia Severity Index (score -5 to 5, from worst to best), before and after operation. These assessments were carried out by 2 speech pathologists. Recurrent laryngeal nerve diameter was measured intraoperatively at the commencement and conclusion of the lobectomy, using Vernier calipers with a resolution of 0.1 mm. Statistical methods used included Student t test, χ2, Wilcoxon signed-rank test, and linear regression. RESULTS: A total of 62 patients were included in the study, with a mean age of 48 ± 16 years and a female preponderance (6:1). Overall, the voice quality deteriorated both subjectively (mean Voice Disorder Index 4.2 ± 0.8-9.4 ± 1.2, P < .01) and objectively (mean Dysphonia Severity Index 3.9 ± 0.3-2.8 ± 0.3, P < .01) with thyroid operation. Patients who underwent either hemi- or total thyroidectomy both reported significant deterioration of voice (mean Voice Disorder Index 5.4 ± 1.5-7.9 ± 1.4, P = .02 and 3.4 ± 0.7-10.4 ± 1.8, P < .01 respectively). However, on objective assessment, only total thyroidectomy patients showed significant deterioration (Mean Dysphonia Severity Index 4.0 ± 0.3-2.5 ± 0.3, P < .01). At 6-12 months, both Voice Disorder Index and DSI returned to preoperative levels. Intraoperatively, the recurrent laryngeal nerve diameter increased by 0.58 ± 0.05 mm (1.82 ± 0.05 mm-2.40 ± 0.05 mm; P < .01). In hemithyroidectomy patients, the degree of nerve swelling correlated with the degree of deterioration in objective voice assessment, in that the greater the increase in recurrent laryngeal nerve diameter, the worse the Dysphonia Severity Index score (coefficient -0.4, P = .03). This was not the case in the total thyroidectomy patients. CONCLUSION: Voice quality deteriorates with thyroid operation despite functionally intact recurrent laryngeal nerve. While likely multifactorial, the degree of deterioration is related to the extent of operation and may also be related to the degree of recurrent laryngeal nerve swelling. Spontaneous resolution is expected in the majority of patients.

No need to abandon focused parathyroidectomy: a multicenter study of long-term outcome after surgery for primary hyperparathyroidism.

OBJECTIVE: The aim of this study was to investigate long-term outcomes after focused parathyroidectomy (FPTX) and open 4-gland parathyroid exploration (OPTX) for primary hyperparathyroidism (pHPT). BACKGROUND: Concerns about increased long-term recurrence rates after FPTX in conjunction with decreased operative times for OPTX have led some groups to abandon FPTX in favor of routine 4-gland exploration. METHODS: This is a multicenter retrospective cohort study of patients undergoing parathyroidectomy for pHPT from 1990 to 2013. The patient cohort was divided into 2 groups, FPTX and OPTX, based on intention-to-treat analysis. The primary outcome measure was the persistence of pHPT. Secondary outcome measures were differences in the long-term recurrence rate of persisting pHPT and surgical complications. RESULTS: A total of 4569 patients (3585 females) were included. The overall persistence and recurrence rates were 2.2% and 0.9%, respectively, after a median follow-up of 6.5 years. There were 2531 FPTX cases and 2038 OPTX cases. The initial persistence rate was higher for FPTX than for OPTX (2.7% vs 1.7%, P = 0.036); however, the long-term recurrence rate was not different (5-year 0.6% vs 0.4%, log-rank P = 0.08). Complications were more common in OPTX than in FPTX (7.6% vs 3.6%, P < 0.001). CONCLUSIONS: FPTX was associated with fewer operative complications and an equivalent rate of long-term recurrence than with OPTX. Although initial persistence rates were higher after FPTX than after OPTX, most were readily resolved with subsequent early reoperation. FPTX should not be abandoned in patients with positive preoperative localization.

Anti-thyroid antibodies as a predictor of thyroid cancer.

BACKGROUND: Recent literature has suggested an association between autoimmune thyroiditis and papillary thyroid cancer. The aims of this study were to evaluate if positive thyroid antibodies are associated with thyroid carcinoma and to examine the role of thyroid antibodies in the management of thyroid nodules. METHODS: This is a database study of all patients undergoing thyroidectomy with recorded preoperative thyroid antibodies (autoantibodies to thyroglobulin and/or thyroid peroxidase) levels from 2010 to 2012. We analysed preoperative thyroid antibody levels, fine needle aspiration cytology (FNAC) results, type of thyroid surgery and final histopathology. RESULTS: There were 960 patients who underwent thyroidectomy with recorded preoperative thyroid antibodies. Of 960 patients, 784 had preoperative FNAC of thyroid nodules. Final histopathology showed 758 benign and 202 malignant cases. As expected, there was a strong association between raised thyroid antibodies and lymphocytic thyroiditis on histology (P = 0.0001) (two-sided probability). Overall, positive thyroid antibodies were not found to be a predictor of thyroid carcinoma (P = 0.161) (two-sided probability). However, in patients with benign FNAC, positive thyroid antibodies increased the risk of thyroid malignancy (odds ratio 2.16; 95% confidence interval 1.11 to 4.21, P = 0.027) (two-sided probability). CONCLUSION: Patients with positive thyroid antibodies have a greater risk of malignancy in those with benign FNAC. We recommend routine thyroid antibody assessment in addition to FNAC as part of the assessment of thyroid nodules.

Differential recurrent laryngeal nerve palsy rates after thyroidectomy.

INTRODUCTION: Recurrent laryngeal nerve (RLN) palsy is a devastating complication of thyroidectomy. Although neurapraxia is thought to be the most common cause, the underlying mechanisms are poorly understood. The objectives of this study were to examine the differential palsy rates between the left and right RLNs, and the role of intraoperative nerve swelling as a risk factor of postoperative palsy. METHODS: Thyroidectomy data were collected, including demographics, change in RLN diameter, and RLN electromyographic (EMG) reading. Left and right RLNs, as well as bilateral and unilateral subgroup analyses were performed. RESULTS: A total of 5,334 RLNs were at risk in 3,408 thyroidectomies in this study. The overall RLN palsy rate was 1.5%, greater on the right side than the left for bilateral cases (P = .025), and greater on the left side than the right for unilateral cases (P = .007). In a subgroup of 519 RLNs, the diameter and EMG amplitude were measured. The RLN diameter increased by approximately 1.5-fold (P < .001), and corresponded to increased EMG amplitude (P = .01) during the procedure. The diameter of the right RLN was larger than the left RLN, both at the beginning and end of the dissection (P = .001). CONCLUSION: The right-left differential rates of post-thyroidectomy RLN palsy seemed to be due in part to differential RLN diameters, with stretch having a more deleterious effect on RLNs with a smaller diameter; also, edema as a result of stretch might be an underlying mechanism for postoperative neurapraxia and palsy. Thyroid surgeons should be aware of the different vulnerabilities of each RLN and develop practices to avoid iatrogenic injury.