Inguinal hernia repair is one of the most commonly performed surgical procedures in children. However, a number of controversial issues, such as optimal timing and approach to repair, continue to be debated. This publication reviews the available data pertaining to these controversial issues and identifies best practices in management of inguinal hernias in children.
Inguinal hernias are a common condition requiring surgical repair in children. Pediatric inguinal hernias are generally indirect, characterized by protrusion of intraabdominal contents through a patent processus vaginalis (PPV). The incidence of inguinal hernias is approximately 8 to 50 per 1000 live births in term infants, increasing to nearly 20% in extremely low birth weight (<1000 g) infants.1,2 The risk of an incarcerated inguinal hernia in children is estimated to be 4%, with the highest risk (8%) noted in infants; consequently, they are commonly repaired shortly after diagnosis.3,4 This report reviews the embryology, pathophysiology, and natural history of PPV and the contemporary evaluation and treatment of pediatric hernias, with special attention to the risks of general anesthetic in very young children. Some controversies in management of inguinal hernias include optimal timing of repair in preterm infants, who should be performing these repairs, optimal approach, need for contralateral evaluation, approach to recurrent hernias, and management of an asymptomatic PPV identified during a nonhernia-related exploration of the abdomen.
Embryology and Natural History of the Patent Processus Vaginalis
Complete understanding of the issues related to surgical repair of an inguinal hernia requires an understanding of the embryology and subsequent development of the processus vaginalis. In males, testicular descent involves 2 phases: intraabdominal and extraabdominal.5 The developing testis is initially attached to the diaphragm by the craniosuspensory ligament; regression of this ligament results in transabdominal migration of the testis. Simultaneously, as the male fetus grows and the abdomen elongates, the testis is essentially anchored by the thickened gubernaculum to the dependent scrotum.6 In the female fetus, the craniosuspensory ligament is maintained; hence, the ovary retains its dorsal (retrocoelomic or retroperitoneal) intraabdominal location. In addition, the gubernaculum does not thicken but persists as the ovarian round ligament.
During the extraabdominal phase (25–35 weeks of gestation), the testis descends through the inguinal canal, drawing with it an extension of the peritoneal lining called the processus vaginalis.7 Normally, the processus vaginalis obliterates and persists as the tunica vaginalis, enveloping the testis. Both human in vitro tissue culture and rodent model studies implicate genitofemoral nerve innervation as critical for regulation of gubernacular length, as well as obliteration of the processus vaginalis.8–10 Incomplete involution results in a PPV, which, when fluid-filled, can present clinically as a hydrocele. If the communication is large or intraabdominal pressures are high, intraabdominal structures such as bowel may herniate, resulting in an indirect inguinal hernia. In this manuscript, PPV indicates a communication between the labia/scrotum and peritoneal cavity, “hydrocele” indicates a PPV containing fluid, and “inguinal hernia” indicates a PPV containing abdominal contents.
The relation of the processus vaginalis with testicular descent is believed to explain why more than 90% of pediatric inguinal hernias occur in boys.11 Involution of the left processus vaginalis precedes that of right, which is consistent with the observation that 60% of indirect inguinal hernias occur on the right side.12 The prevalence of PPV is highest during infancy (as high as 47% in newborn infants and 27% in children younger than 2 years) and declines with age.13 Congenital hydroceles, which are essentially clinically apparent PPV, usually resolve spontaneously within 18 to 24 months.14–16 These prevalence estimates, however, have been generally extrapolated from findings at time of exploration of the contralateral internal ring during inguinal hernia repair and possibly overestimate the true prevalence of PPV in the general population. Rowe et al reported a 64% rate of contralateral PPV identified at the time of inguinal hernia repair in infants younger than 2 months. Reported rates of contralateral PPV decrease to between 33% and 50% in children younger than 1 year and are as low as 15% by 5 years.13,17–20 Centeno-Wolf et al and Weaver et al reported the rate of asymptomatic PPV in children undergoing nonhernia-related abdominal surgeries to be 9.1% and 20%, respectively.16,21 Most patients included in the former study were older than 8 years, potentially explaining the lower point prevalence estimate in that group.17 Not all patients with an asymptomatic PPV subsequently develop an inguinal hernia. In patients undergoing an intervention for inguinal pathology, Toki et al estimated the rate of spontaneous regression of PPV after 9 months of age to range from 67% to 91%.22 Rowe et al reported that contralateral PPV obliterates in approximately 40% of patients in the first few months of life and an additional 20% in the next 2 years, and only 40% remain patent after 2 years.17 Among those with a PPV after 2 years, approximately half will develop a clinical hernia.23–25 Among patients without a previously known inguinal pathology and an incidentally discovered PPV in the studies by Centeno-Wolf and Weaver et al, a clinically evident inguinal hernia developed at the rate of 10.5% and 13.5%, respectively, during a median follow-up period of 10.5 and 8.1 years, respectively.16,21 The incidence of PPV incidentally discovered in adults is similarly estimated to be 12%, and the presence of one confers a 12% risk of developing a subsequent indirect inguinal hernia.26
Optimal Timing of Repair in Preterm Infants
Among preterm infants, the incidence of inguinal hernias is reported to be as high as 20%.2 Despite being one of the most commonly performed operations in preterm neonates, the optimal timing of inguinal hernia repair remains controversial, as suggested by the significant variability in practice among pediatric surgical specialists. Sulkowski et al reported that, although children treated at the Pediatric Health Information System-participating hospitals were overall more likely (67.1%) to undergo repair before hospital discharge, there were notable variations in practice, with anywhere from 3% to 74% of repairs at individual sites being performed on an outpatient basis.27 In addition, slightly more than half (53%) of the pediatric surgical specialists, in a survey performed by the American Academy of Pediatrics, reported repairing inguinal hernias in preterm neonates when convenient.28 Possible motivations for delaying inguinal hernia repair in preterm neonates include technical challenges, higher rate of recurrence, comorbid conditions associated with prematurity, and anesthesia-related concerns including risk of postoperative apnea and prolonged postoperative ventilator dependence.29,30
Lautz et al, using the 2003 and 2006 Kids’ Inpatient Database, demonstrated that the rate of inguinal hernia incarceration in 49 000 preterm infants reviewed was 16%, with a proportional increase in the rate of incarceration with increasing corrected gestational age at the time of surgery.31 Given this possible higher incidence of incarceration in preterm infants, some pediatric surgeons argue that delayed repair can increase the frequency of inguinal hernia-related complications, such as bowel incarceration, strangulation, and testicular atrophy.32,33 Moreover, in the event of an incarceration, emergent repairs in this group of patients also pose an enhanced risk of perioperative complications. Others hypothesize that repeated hernia reductions attributable to intermittent incarceration can potentially lead to scarring of the hernia sac, thereby increasing the complexity of the subsequent repair.34 A recent meta-analysis including 7 retrospective studies with a total of 2024 patients attempted to identify optimal timing of repair.30 Included in this analysis were 1176 patients who underwent repair before and 848 patients who underwent repair after NICU discharge, with no observed differences in the rates of incarceration—18.1% versus 11.3%, respectively. The rates of recurrence (5.7% vs 1.8%), reoperation (5.7% vs 3.3%), respiratory complications (odds ratio = 4.9), and the duration of surgery were significantly higher in those who underwent repair before NICU discharge. In addition, a retrospective study of 263 preterm infants revealed a considerably lower postrepair hospital length of stay in the cohort that underwent repair after discharge from the NICU (11.75 vs 1.02 days).29 The authors concluded that there was moderate-quality evidence supporting deferring inguinal hernia repair until after discharge from the NICU in preterm infants, because this may reduce the risk of respiratory difficulties without increasing the risk of incarceration and reoperation.30 The Timing of Inguinal Hernia Repair in Premature Infants trial (#NCT01678638) recently finished enrolling patients. The results of this trial are awaited and expected to help determine whether an early or late-repair approach is optimal in preterm infants.35
Who Should Be Performing Pediatric Inguinal Hernia Repairs?
Several previous studies have shown that pediatric general surgical specialist volume and subspecialty training can lead to improved surgical outcomes.36,37 When fellowship-trained pediatric surgical specialists provide care for certain surgical conditions such as pyloromyotomy and acute appendicitis, improved outcomes have been previously demonstrated.38–40 Using the Canadian Institute for Health Information to review 20 545 pediatric inguinal hernia repairs, Borenstein et al41 demonstrated that, despite pediatric surgical specialists caring for a higher proportion of patients younger than 1 year, the overall risk of hernia recurrence was 2.4-fold higher among patients managed by general surgeons. Among pediatric surgical specialists, the estimated risk of recurrence was independent of surgical volumes. However, there was a significant inverse relationship between recurrence rates and general surgeon case volume: general surgeons performing fewer than 10 pediatric inguinal hernias per year had the highest incidence of recurrence, and the highest-volume general surgeons achieved recurrence rates similar to pediatric surgical specialists. Fellowship-trained pediatric surgical specialists have the lowest rate of hernia recurrences. However, if access to a pediatric surgical specialist is challenging because of geographic constraints, general surgeons who perform a reasonable number of pediatric hernia repairs can achieve similar outcomes. Similarly, pediatric urologists have been shown to achieve very low rates of inguinal hernia recurrences.42
Another resource needed for the optimal care of an infant undergoing inguinal hernia repair is care provided under the direction of a pediatric specialist anesthesiologist.43 Pediatric patients cared for by a pediatric anesthesiologist versus a general anesthesiologist have been shown to have a lower incidence of perioperative cardiac arrest and respiratory complications.44,45 Similar to the volume outcome ratio discussed previously for surgical providers, anesthesiologists providing 200 or more pediatric anesthetics per year appear to have lower rates of perianesthetic complications.46 If access to a pediatric anesthesiologist is limited because of geographic constraints, general anesthesiologists with yearly volume as described would be preferred. In addition, medically complex patients with higher risk of perioperative complications, such as those with uncorrected congenital heart disease, pulmonary hypertension, etc, likely would benefit from the additional expertise of a pediatric anesthesiologist.
Open Versus Laparoscopic Approach
The traditional gold standard approach to pediatric inguinal hernia repair has been via open high ligation of the hernia sac. However, laparoscopic approaches are increasingly more popular, as evidenced by a fivefold increase in the proportion of cases performed laparoscopically between 2009 and 2018.47,48 Initial comparisons of open versus laparoscopic repairs suggested potentially higher recurrence rates with the latter approach, which remains a frequent critique of this approach.30 More recent data have not supported these initial findings. Outcomes between open and laparoscopic approaches have been compared directly in 8 randomized controlled trials to date.30 Meta-analysis of these trials comparing 375 patients in each arm demonstrated no differences in the complication and recurrence rates. Laparoscopic approach was found to be associated with a significantly shorter operation time in patients with bilateral inguinal hernias as compared with the open approach.30 Chong et al,49 in a retrospective review of 1697 pediatric inguinal hernias, reported a significantly higher rate of development of metachronous contralateral inguinal hernia rate in the open (10.7 per 1000 person-years) as compared with the laparoscopic approach (3.4 per 1000 person-years). When compared with open surgery, the hazard ratio of needing a second surgery (metachronous contralateral hernia or recurrence) with a laparoscopic approach was 0.3, with numbers needed to treat of 33. This difference is likely explained by the ability to visualize the contralateral internal inguinal ring with the laparoscopic approach, leading to a considerably higher (38% vs 17%) observed rate of bilateral repairs in the laparoscopic group as opposed to the open group.50 Additionally, Shalaby et al,51 in a randomized controlled trial comparing open versus laparoscopic inguinal hernia repair, reported that 4% parents of the patients reported an “ugly” scar in the open repair group as compared with none in the laparoscopic group. They also reported that 3.3% patients in the open group had a significant reduction in testicular perfusion and size, with no differences noted in the pre- and postoperative ultrasonographic findings in the laparoscopic group. Koivusalo et al52 reported a considerably higher need for rescue analgesia in patients repaired via the open approach (79% vs 42%) as compared with the laparoscopic approach. The International Pediatric Endosurgery Group’s evidence-based guidelines on pediatric inguinal hernia repair also favor minimally invasive approaches to open surgery because of the reduced rate of postoperative complications, shorter operative time in patients needing bilateral repair, and similar rates of recurrence.50
In the realm of laparoscopic approaches, there is considerable variation in specific techniques for repairs. Speck and Smith, for the Society of American Gastrointestinal and Endoscopic Surgeons, have broadly classified these approaches into intracorporeal versus extracorporeal.53 Intracorporeal approaches aim to close the internal ring with an intracorporeally placed suture, whereas extracorporeal methods use placement of suture to close the internal ring in the preperitoneal plane via a separate inguinal incision under laparoscopic guidance. Three randomized studies have directly compared these methods of minimally invasive repair, revealing no differences in the rate of recurrence. However, operative times appear to be shorter using the extracorporeal technique.31,54–56
In summary, ample evidence suggests that laparoscopic approach is at least as effective as open high ligation. Within minimally invasive approaches, there is some evidence to favor the extraperitoneal approach.
Need for Contralateral Evaluation
Among patients with unilateral inguinal hernia, contralateral exploration has been a subject of considerable debate. Proponents of exploration cite a 10% to 15% rate of development of a metachronous hernia. Therefore, routine exploration and, if identified, ligation of a PPV could potentially avoid a subsequent anesthetic.30 Opponents counter that not all PPVs evolve into a clinically significant inguinal hernia, and routine exploration exposes the patient to potentially unnecessary operative complications. Meta-analysis of 23 retrospective studies with 9603 patients reported that a contralateral processus vaginalis is identified in 63.5% of patients undergoing unilateral inguinal hernia repair with an approximately 1.9% rate of complications with routine contralateral exploration.30 In this analysis, only 8.4% of patients who underwent unilateral repair without contralateral exploration developed a metachronous hernia. Although these pooled data suggest a reduction in the rate of development of a metachronous inguinal hernia with routine contralateral exploration, given the low quality of data, no firm recommendations could be made.
Use of a laparoscopic approach, however, allows inspection of the contralateral side without any additional interventions. However, when a contralateral PPV is identified in an otherwise asymptomatic child, there is controversy whether a ligation is appropriate. A systematic review encompassing 129 published studies by Kokorowski et al57 reported that there is a 30% rate of detection of a contralateral PPV with only a 7.3% rate of development of a contralateral metachronous inguinal hernia, implying that 3 asymptomatic PPVs will need to be closed to prevent one metachronous contralateral inguinal hernia. In the absence of better-quality data, it remains unclear whether these incidentally identified PPV should be repaired. A preoperative, family-centered discussion encompassing the low but present risk of developing a contralateral hernia, the very low but potentially harmful risk of incarcerated hernia, and the potential need for another surgical procedure in the future can guide operative management, because different families may have a variety of perspectives related to risk and benefit.
Optimal Approach to Recurrent Inguinal Hernias
Recurrence remains a rare complication, with an approximately 1% estimated rate after elective hernia repairs.58 Rate of recurrence can increase to as high as 24% with certain patient factors such as incarceration, presence of ascites, or a ventriculoperitoneal shunt.58 Several technical factors can contribute to the risk of development of a recurrent hernia after open repair. These include failure to ligate the sac high enough, repair of an excessively large internal inguinal ring, and excessive dissection leading to damage to the inguinal floor resulting in a subsequent direct hernia.58 Similarly, after laparoscopic repair, excessive tension and presence of skip areas (particularly close to the testicular vessels, vas deferens, and epigastric vessels) can lead to a higher risk of recurrence.59 Repair of these recurrent hernias via repeat inguinal exploration can be extremely challenging, particularly in male patients, because of the difficulty in identifying critical structures and are known to be associated with an increased risk of testicular atrophy.60 Laparoscopic approach to these recurrent hernias offers the advantage of a previously unexplored field (if index approach was open), identification of the root cause of recurrence, and the opportunity to identify rare defects such as a femoral hernia. Shalaby et al, in describing their series of 42 recurrent inguinal hernias, reported that the perceived difficulty of the procedure and the operative times for recurrent inguinal hernias managed laparoscopically was the same as a primary laparoscopic hernia repair.58 Yildiz et al61 compared open versus laparoscopic approach to recurrent pediatric inguinal hernias and noted a considerably shorter operative time in the laparoscopic group (32.4 vs 61 minutes), with no postoperative recurrences or testicular atrophy during the 8- to 16-month follow-up. On the basis of the retrospective data and intuitively given the advantages listed above, laparoscopy appears to be a feasible option in managing recurrent pediatric inguinal hernias.
General Anesthesia and Effect on Neurodevelopment
Over the last several years, there has been an increasing concern related to the effect of general anesthesia on pediatric neurodevelopment after the publication of a “Drug Safety Communication” by the US Food and Drug Administration, which included a warning regarding the neurodevelopmental effects of general anesthesia.62 This concern originally arose from animal studies demonstrating development of learning and behavioral deficits after exposure to general anesthesia later in life.63 A number of human studies have also explored the relationship between exposure to general anesthesia and subsequent neurodevelopmental deficits in children. As noted in a recent systematic review,64 human studies have reported conflicting evidence of any association between exposure to anesthesia in early childhood and adverse long-term neurodevelopmental outcomes. A number of these studies are marred by significant variations in the study methodology, including tools used for assessment of neurodevelopment: Some have relied on teacher or parent opinions via surveys and others still evaluated exposure to any number of anesthetics. Because young children usually undergo general anesthesia for surgical procedures or investigative studies, it is possible that the underlying pathology or other comorbidities are important unadjusted confounders for the risk of subsequent poor neurodevelopmental outcomes.
The 2 most robust studies available to look at this association are the General Anesthesia Compared with Spinal Anesthesia (GAS) and Pediatric Anesthesia Neurodevelopment Assessment studies. In the GAS trial,65,66 infants up to 60 weeks’ postmenstrual age scheduled for unilateral or bilateral inguinal hernia repair who were born at greater than 26 weeks’ gestation were included in this randomized control trial at 28 participating hospitals on 3 continents. Those with risk factors for potential neurologic injury or previous exposure to volatile general anesthesia were excluded from the study, and 363 patients were randomized to awake-regional (spinal, caudal, or combined) anesthesia and 359 to general anesthesia using sevoflurane. The primary outcome of the trial was the full-scale IQ score on the Wechsler Preschool and Primary Scale of Intelligence scale at 5 years of age. Secondary outcome was the composite cognitive score of the Bayley Scales of Infant and Toddler Development III, assessed at 2 years of age. The median duration of anesthesia in the general anesthesia group was 54 minutes. At 2 years of age, secondary outcome data were analyzed for 238 children in the awake-regional anesthesia group and for 294 children in the general anesthesia group. The mean (SD) cognitive composite score in the awake-regional group and in the general anesthesia group was equivalent (98.6 [14.2] vs 98.2 [14.7]). At 5 years of age, primary outcome data were analyzed for 205 children in the awake-regional anesthesia group and 242 in the general anesthesia group. The mean (SD) full-scale IQ score was 99.08 (18.35) in the awake-regional anesthesia group and 98.97 (19.66) in the general anesthesia group, with a difference in means (awake-regional anesthesia minus general anesthesia) of 0.23 (95% confidence interval, −2.59 to 3.06), providing strong evidence of equivalence.
The Pediatric Anesthesia Neurodevelopment Assessment study67 assessed neuropsychological functions and behavior at 8 to 15 years of age using a sibling-matched cohort design in patients who had undergone a single exposure to general anesthesia during inguinal hernia surgery before 36 months of age from 2000 to 2010. Global cognitive function (IQ) was the primary outcome, and domain-specific neurocognitive functions and behavior were secondary outcomes. A total of 105 sibling pairs (exposed versus unexposed) had IQ testing at mean ages of 10.6 and 10.9 years, respectively. All exposed children received inhaled anesthetic agents with a median duration of 80 minutes. Mean IQ scores between exposed siblings (scores: full scale = 111; performance = 108; verbal = 111) and unexposed siblings (scores: full scale = 111; performance = 107; verbal = 111) were not statistically significantly different. No statistically significant differences in mean scores were found between sibling pairs in memory/learning, motor/processing speed, visuospatial function, attention, executive function, language, or behavior. Grabowski et al,64 in their systematic review of studies looking at the effect of general anesthesia with neurodevelopmental outcomes, concluded that, although it would be reasonable to avoid multiple exposures to or prolonged anesthesia for elective surgical procedures, there is no evidence that exposure to a single brief general anesthetic poses any significant risk to neurodevelopment, academic performance, or risk of attention-deficit/hyperactivity disorder or autism spectrum disorder. The American Academy of Pediatrics also noted in its response to the US Food and Drug Administration warning on anesthesia use in children that controlled trials in humans and multiple epidemiologic studies have not demonstrated any developmental problems in children exposed to a single, short anesthetic or sedation.68
General Anesthesia and Risk of Postanesthetic Apnea
Among former preterm infants, the risk of postoperative apnea is an important consideration when considering ambulatory setting for repair. A number of prospective and retrospective studies have attempted to identify patients most at risk.69–72 A combined analysis of 8 prospective studies noted that the risk of postoperative apnea was strongly associated with gestational age, postconceptional age, and anemia.72 Among nonanemic infants without recovery room apnea, the risk of postoperative apnea did not decrease below 1% until the postconceptional age was 56 weeks with gestational age of 32 weeks or postconceptional age of 54 weeks with gestational age of 35 weeks. A secondary analysis of the GAS study noted that the overall risk of postoperative apnea was independent of the technique of anesthetic used, although spinal/regional anesthesia was associated with a reduced risk of early apnea; the study authors recommended cardiorespiratory monitoring in all former preterm infants less than 60 weeks of corrected gestational age.73 In light of these data, institutional policies should be developed outlining the need and duration of observation after anesthesia in former preterm infants.
Inguinal hernias are a common pediatric surgical condition, and the risk of incarceration drives the preference for and timing of surgical repair.
In preterm infants, repair can be safely considered after discharge from the NICU.
Ideally, pediatric surgical specialists, pediatric urologists, or general surgeons with a significant yearly case volume should repair pediatric inguinal hernias to achieve optimal outcomes.
The laparoscopic approach appears to be gaining popularity and is at least as effective as, if not better than, traditional open high ligation.
In the absence of strong data for or against repair of incidentally discovered contralateral PPV, family values related to the risks and benefits of each approach from a nuanced preoperative discussion should be considered.
Laparoscopy appears to be a feasible alternative in managing recurrent hernias.
There is no conclusive evidence to suggest that exposure to a single relatively short duration of anesthetic has adverse effects on neurodevelopmental outcomes in otherwise healthy children.
Faraz A. Khan, MD, FAAP
Tim Jancelewicz, MD, FAAP
Kathleen Kieran, MD, FAAP
Saleem Islam, MD, FAAP
Committee on Fetus and Newborn, 2021–2022
Eric Eichenwald, MD, Chairperson
Charleta Guillory, MD
Ivan Hand, MD
Mark Hudak, MD
David Kaufman, MD
Camilia Martin, MD
Ashley Lucke, MD
Margaret Parker, MD
Arun Pramanik, MD
Kelly Wade, MD
Timothy Jancelewicz, MD – AAP Section on Surgery
Michael Narvey, MD – Canadian Pediatric Society
Russell Miller, MD – American College of Obstetricians and Gynecologists
RADM Wanda Barfield, MD, MPH – Centers for Disease Control and Prevention
Lisa Grisham, APRN, NNP-BC – National Association of Neonatal Nurses
Jim Couto, MA
Section on Surgery Executive Committee, 2021–2022
Kenneth William Gow, MD, FAAP, Chair
Elizabeth Beierle, MD, FAAP
Marybeth Browne, MD, FAAP
Andrew Davidoff, MD, FAAP, Immediate Past Chair
Cynthia D. Downard, MD, FAAP
Saleem Islam, MD, MPH, FAAP
Danielle Saunders Walsh, MD, FAAP
Regan Frances Williams, MD, FAAP – early career liaison
Section on Urology Executive Committee, 2021–2022
Nicholas Cost, MD, FAAP, Chairperson
Stephen Canon, MD, FAAP
Gregory Dean, MD, FAAP
Martin Kaefer, MD, FAAP
Kathleen Kieran, MD, FAAP
Andrew Kirsch, MD, FAAP, Immediate Past Chairperson
John C. Pope, MD, FAAP
Elizabeth Yerkes, MD, FAAP
Dr Khan designed the outline, performed literature review, drafted the manuscript, reviewed and compiled the feedback from all the authors, and finalized the manuscript; Dr Islam supervised development of the outline and critically reviewed the manuscript for important intellectual content; Drs Jancelwicz and Kieran critically reviewed the manuscript for important intellectual content; and all authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work.
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The guidance in this report does not indicate an exclusive course of treatment or serve as a standard of medical care. Variations, taking into account individual circumstances, may be appropriate.
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