A computed tomography study investigating the effects of botulinum toxin injections prior to complex abdominal wall reconstruction.

OBJECTIVE: To explore how intramuscular injection of botulinum toxin A (BTA) affects the lateral abdominal wall (LAW) musculature, abdominal- and hernia dimensions, and muscle structure on computed tomography (CT) in patients scheduled for complex abdominal wall reconstruction (CAWR). METHODS: Retrospective analysis of prospectively registered patients who received bilateral intramuscular BTA injections into all three muscles of the LAW. Only patients for which a CT was available before and 3-6 weeks after BTA treatment prior to surgery were analyzed. RESULTS: Fifty-two patients were analyzed. Median hernia width in all patients decreased with 0.4 cm (IQR - 2.1;0.6) (p = 0.023). Median intra-abdominal transverse diameter increased with 0.9 cm (IQR - 0.2;3.3) (p = 0.001) and the intra-abdominal anterior-posterior diameter decreased with 0.5 cm (IQR - 1.3;0.5) (p = 0.017), making the abdomen more oval. Median LAW muscle length increased with 0.9 cm (IQR 0.0;2.4) per side (p < 0.001), muscle thickness decreased with 0.5 cm (IQR - 0.8;- 0.2) (- 25.0%) per side (p < 0.001), and muscle mass decreased with 3.9 cm2 (IQR - 6.4;-1.5) (- 15.8%) per side (p < 0.001). Median HU of the psoas muscles (density) increased with 4.8 HU (IQR 0.4;9.7) (10.3%) per side (p < 0.001). Effects of BTA were more pronounced in patients with a loss of domain (LoD) ≥ 20%. CONCLUSIONS: The main effect of BTA injections is elongation and thinning of the LAW muscles, more than a decrease in hernia width. Concomitantly, the abdomen becomes more oval. An increase of psoas muscles density is seen, associated with offloading of the LAW muscles. Patients with large LoD have a proportionally higher effect of BTA.

A systematic review and meta-analysis of technical aspects and clinical outcomes of botulinum toxin prior to abdominal wall reconstruction.

PURPOSE: To systematically review technical aspects and treatment regimens of botulinum toxin A (BTA) injections in the lateral abdominal wall musculature. We also investigated the effect of BTA on abdominal muscle- and hernia dimensions, and clinical outcome. METHODS: PubMed, EMBASE, CENTRAL, and CINAHL were searched for studies that investigate the injection of BTA in the lateral abdominal wall muscles. Study characteristics, BTA treatment regimens, surgical procedures, and clinical outcomes are presented descriptively. The effect of BTA on muscle- and hernia dimensions is analyzed using random-effects meta-analyses, and exclusively for studies that investigate ventral incisional hernia patients. RESULTS: We identified 23 studies, comprising 995 patients. Generally, either 500 units of Dysport® or 200-300 units of Botox® are injected at 3-5 locations bilaterally in all three muscles of the lateral abdominal wall, about 4 weeks prior to surgery. No major procedural complications are reported. Meta-analyses show that BTA provides significant elongation of the lateral abdominal wall of 3.2 cm per side (95% CI 2.0-4.3, I2 = 0%, p < 0.001); 6.3 cm total elongation, and a significant but heterogeneous decrease in transverse hernia width (95% CI 0.2-6.8, I2 = 94%, p = 0.04). Furthermore, meta-analysis shows that BTA pretreatment in ventral hernia patients significantly increases the fascial closure rate [RR 1.08 (95% CI 1.02-1.16, I2 = 0%, p = 0.02)]. CONCLUSION: The injection technique and treatment regimens of botulinum toxin A as well as patient selection require standardization. Bilateral pretreatment in hernia patients significantly elongates the lateral abdominal wall muscles, making fascial closure during surgical hernia repair more likely. STUDY REGISTRATION: A review protocol for this meta-analysis was registered at PROSPERO (CRD42020198246).

Outcomes of mid-term and long-term degradable biosynthetic meshes in single-stage open complex abdominal wall reconstruction.

OBJECTIVE: To assess clinical outcomes in patients that underwent open single-stage complex abdominal wall reconstruction (CAWR) with biosynthetic mesh. METHODS: Retrospective observational study of two prospectively registered series of consecutive patients undergoing CAWR with either long-term degradable (LTD) Phasix™ or mid-term degradable (MTD) BIO-A® biosynthetic mesh in a single institution between June 2016 and December 2019. RESULTS: From 169 patients with CAWR, 70 consecutive patients were identified who underwent CAWR with either LTD or MTD biosynthetic mesh. More than 85% of patients had an incisional hernia that could be classified as moderately complex to major complex due to a previous wound infection (67%), one or more complicating comorbidities (87.1%), one or more complicating hernia characteristics (75.7%) or contaminated or dirty defects (37.1%). Concomitant component separation was performed in 43 of 70 patients (61.4%). Overall surgical site infection (SSI) rate in these CAWR patients was 45.7%. Seventeen of 70 patients (24.3%) had computed tomography (CT) - and culture-confirmed SSI in direct contact of mesh, suspicious of mesh infection. Mesh removal for persistent local infection occurred in 10% (7 of 70) after a median of 229 days since surgery. Salvage rate of mesh after direct contact with infection was 58.8%. All removed meshes were in the LTD group. Seven patients (10%) had a recurrence; four patients in the LTD group (10%) had a recurrence at a median follow-up of 35 months and three patients in the MTD group (10%) at a median follow-up of 11 months. Three of the seven recurrences occurred in patients with SSI in persistent and direct contact with mesh. CONCLUSIONS: Comorbid patients undergoing open complex abdominal wall reconstruction are at high risk of postoperative wound complications regardless of which type of biosynthetic mesh is used. When in persistent and direct contact with infection, long-term biodegradable biosynthetic meshes may need to be removed, whereas mid-term biodegradable biosynthetic meshes can be salvaged.

Validation of a Scoring System to Distinguish Uncomplicated From Complicated Appendicitis.

BACKGROUND: Studies have shown that uncomplicated appendicitis can be treated conservatively with antibiotics. It is important to select only those patients with uncomplicated appendicitis when considering conservative management. Recently, a scoring system based on clinical evaluation and ultrasound was developed to improve this selection and aid in shared decision making when considering an antibiotics-first strategy. The aim of this study was to externally validate the scoring system. MATERIALS AND METHODS: A retrospective cohort study of all adult patients presenting to the emergency department between January 2014 and January 2017 with suspected acute appendicitis based on clinical evaluation and ultrasound was performed. For every patient, a score was calculated using the previously described scoring system. A final diagnosis, subdivided into complicated appendicitis, uncomplicated appendicitis, complicated alternative disease, and uncomplicated alternative disease, was assigned to every patient based on operative findings. RESULTS: A total of 678 patients with suspected acute appendicitis based on clinical and ultrasonography findings were identified, of whom 175 (25.8%) had complicated appendicitis, 491 (72.4%) had uncomplicated appendicitis, and 12 (1.8%) had an alternative disease. Of the 678 patients, 272 had a score of five points or less, of whom 17 (6.2%) had complicated appendicitis, giving a negative predictive value of 93.8%. CONCLUSIONS: With the scoring system based on clinical and ultrasonography features, 93.8% of patients predicted to have uncomplicated appendicitis were correctly identified. The scoring system could help identify patients suitable for conservative management in future studies.

Closed incision prophylactic negative pressure wound therapy in patients undergoing major complex abdominal wall repair.

PURPOSE: To evaluate if incisional prophylactic negative pressure wound therapy (pNPWT) reduces wound infections and other wound complications in high-risk patients undergoing major complex ventral abdominal wall repair. METHODS: Retrospective before-after comparison nested in a consecutive series of patients undergoing elective major complex abdominal wall repair. Starting January 2014, pNPWT was applied on the closed incisional wound for a minimum of 5 days. To minimize selection bias, we compared two periods of 14 months before and after January 2014. Wound infections according to the Centre for Disease Control Surgical Site Infection classification as well as other wound complications were recorded. RESULTS: Thirty-two patients were included in the pNPWT group and 34 in the control group. The study group involved clean-contaminated and contaminated operations due to enterocutaneous fistula, enterostomies or infected mesh. Median duration of pNPWT was 5 days (IQR 5-7). Overall wound infection rate was 35%. pNPWT was associated with a significant decrease in postoperative wound infection rate (24 versus 51%; p = 0.029, OR 0.30 (95% CI 0.10-0.90)). Incisional wound infection rates dropped from 48 to 7% (p < 0.01, OR 0.08 (95% CI 0.16-0.39), whereas the number of subcutaneous abscesses was comparable in both groups. Moreover, less interventions were needed in the pNPWT group (p < 0.001). CONCLUSIONS: Closed incision pNPWT seems a promising solution to reduce the incidence of wound infections in complex abdominal wall surgery. Randomized controlled trials are needed to estimate more precisely the value and cost-effectiveness of pNPWT in this high-risk setting.

Major Complex Abdominal Wall Repair in Contaminated Fields with Use of a Non-cross-linked Biologic Mesh: A Dual-Institutional Experience.

BACKGROUND: Data on the use of biologic mesh in abdominal wall repair in complex cases remain sparse. Aim of this study was to evaluate a non-cross-linked porcine acellular dermal matrix for repair of complex contaminated abdominal wall defects. METHODS: Retrospective observational cohort study of consecutive patients undergoing abdominal wall repair with use of Strattice™ Reconstructive Tissue Matrix (LifeCell Corporation, Oxford, UK) between January 2011 and February 2015 at two National Intestinal Failure Units. RESULTS: Eighty patients were identified. Indications for abdominal wall repair included enterocutaneous fistula takedown (n = 50), infected synthetic mesh removal (n = 9), restoration of continuity or creation of a stoma with concomitant ventral hernia repair (n = 12), and others (n = 9). The median defect area was 143.0 cm2 (interquartile range or IQR 70.0-256.0 cm2). All had a grade III or IV hernia. Component separation technique (CST) was performed in 54 patients (68%). Complete fascial closure was not possible despite CST and biologic mesh-assisted traction (bridged repair) in 20 patients (25%). In-hospital mortality was 1%. Thirty-six patients (45%) developed a wound infection. None required mesh removal. Of 76 patients with a median clinical follow-up of 7 months (IQR 4-15) available for analysis, 10 patients (13%) developed a hernia recurrence, of whom 3 had undergone bridged repairs. Seven patients developed a postoperative (recurrent) fistula (9%). CONCLUSION: Repair of challenging and contaminated abdominal wall defects can be done effectively with non-cross-linked biologic mesh and component separation technique without the need for mesh removal despite wound infections.

[A preschooler with abdominal pain in the right lower quadrant]. / Een kleuter met pijn rechts onderin de buik.

A 5-year-old boy with acute abdominal pain in the right lower quadrant and fever underwent open appendectomy following clinical observation and serial equivocal ultrasound. During exploration we encountered a normal-looking appendix but multiple enlarged mesenteric lymph nodes, suggestive of mesenteric lymphadenitis. The boy had an uneventful postoperative course and recovered completely.

Meta-analysis and trial sequential analysis of triclosan-coated sutures for the prevention of surgical-site infection.

BACKGROUND: Triclosan-coated sutures (TCS) were developed to reduce the risk of surgical-site infection (SSI). Level 1A evidence of effectiveness has been presented in various recent meta-analyses, yet well designed RCTs have not been able to reproduce these favourable results. The aim of this study was to evaluate all available evidence critically with comprehensive analysis to seek a more reliable answer regarding the effectiveness of TCS in the prevention of SSI. METHODS: PubMed, MEDLINE, Embase and Cochrane Library databases were searched from 1990 to November 2015 for RCTs that compared TCS with sutures that were exactly the same, but uncoated, in the prevention of SSI. Pooled relative risks (RRs) with corresponding 95 per cent confidence intervals were estimated using a random-effects model. Metaregression was used to substantiate subgroup effects, trial sequential analysis was employed to assess the risk of random error, and quality of evidence was determined using Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology. RESULTS: Twenty-one RCTs including 6462 patients were included. Risk of bias was serious. Pooled effects showed a RR of 0·72 (95 per cent c.i. 0·60 to 0·86; P < 0·001) for all publications. At a risk of 138 SSIs per 1000 procedures, the use of TCS reduced this by 39 (95 per cent c.i. 19, 55). Trial sequential analysis confirmed a RR reduction of 15 per cent for the use of TCS. CONCLUSION: GRADE assessment shows moderate-quality evidence that TCS are effective in reducing SSI. Trial sequential analysis indicates that the effect was robust, and additional data are unlikely to alter the summary effect.

Outcome of acute intestinal failure.

BACKGROUND: Type 2 acute intestinal failure is characterized by the need for parenteral nutrition (PN) for several months, and is typically caused by complications of abdominal surgery with enteric fistulas or proximal stomas. This study aimed to evaluate clinical management according to quality indicators established by the Association of Surgeons of Great Britain and Ireland. METHODS: Consecutive patients with type 2 intestinal failure referred to a specialized centre were analysed. Outcomes included the rate of discontinuation of PN, morbidity and mortality. RESULTS: Eighty-nine patients were analysed, of whom 57 had an enteric fistula, 29 a proximal stoma (6 with distal fistulas), and three had intestinal failure owing to other causes. One patient was deemed inoperable, and nine patients died from underlying illness during initial management. Before reconstructive surgery, 94 per cent (65 of 66 operated and 3 patients scheduled for surgery) spent the period of rehabilitation at home. Discontinuation of PN owing to restoration of enteral autonomy was achieved in 65 (73 per cent) of 89 patients. Seven patients developed a recurrent fistula, which was successfully managed with a further operation in four, resulting in successful fistula takedown in 41 of 44 patients undergoing fistula resection. Three patients (5 per cent) died in hospital after reconstructive surgery. The overall mortality rate in this series, including preoperative deaths from underlying diseases, was 16 per cent (14 patients). CONCLUSION: Intestinal failure care and reconstructive surgery resulted in successful discontinuation of PN in the majority of patients, although disease-related mortality was considerable.

Ileostomy closure by colorectal surgeons results in less major morbidity: results from an institutional change in practice and awareness.

PURPOSE: Previous institutional analysis of ileostomy closure revealed substantial morbidity. This subsequent study aimed at determining if a change in clinical practice resulted in reduced complication rates. METHODS: Between June 2004 and January 2014, all consecutive adult patients undergoing ileostomy closure were retrospectively identified. Postoperative outcome after change in clinical practice consisting of routine participation of a colorectal surgeon, stapled side-to-side anastomosis and increased clinical awareness (cohort B) was compared with our previously published historical control group (cohort A). The primary outcome was major morbidity, defined as Clavien-Dindo grade three or higher. Independent risk factors of major morbidity were identified using multivariable analysis. RESULTS: In total, 165 patients underwent ileostomy closure in cohort A, and 144 patients in cohort B. At baseline, more primary diverting ileostomies were present in cohort A (94 vs. 82%; p = 0.001) with a similar rate of loop and end-ileostomy between the two cohorts (p = 0.331). A significant increase in colorectal surgeon participation (89 vs. 53%; p < 0.001) and stapled side-to-side anastomosis was observed (63 vs. 16%; p < 0.001). The major morbidity rate was 11% in cohort A, which significantly reduced to 4% in cohort B (p = 0.03). Surgery being performed or supervised by a colorectal surgeon (odds ratio [OR] 0.28, 95% CI 0.11-0.67) and loop-ileostomy compared to end-ileostomy (OR 0.18, 95% CI 0.07-0.52) were independently associated with lower major morbidity. CONCLUSION: Ileostomy closure appears to be more complex surgery then generally considered, especially end-ileostomy closure. Postoperative outcome could be significantly improved by a change in surgical practice.

Scoring system to distinguish uncomplicated from complicated acute appendicitis.

BACKGROUND: Non-operative management may be an alternative for uncomplicated appendicitis, but preoperative distinction between uncomplicated and complicated disease is challenging. This study aimed to develop a scoring system based on clinical and imaging features to distinguish uncomplicated from complicated appendicitis. METHODS: Patients with suspected acute appendicitis based on clinical evaluation and imaging were selected from two prospective multicentre diagnostic accuracy studies (OPTIMA and OPTIMAP). Features associated with complicated appendicitis were included in multivariable logistic regression analyses. Separate models were developed for CT and ultrasound imaging, internally validated and transformed into scoring systems. RESULTS: A total of 395 patients with suspected acute appendicitis based on clinical evaluation and imaging were identified, of whom 110 (27·8 per cent) had complicated appendicitis, 239 (60·5 per cent) had uncomplicated appendicitis and 46 (11·6 per cent) had an alternative disease. CT was positive for appendicitis in 284 patients, and ultrasound imaging in 312. Based on clinical and CT features, a model was created including age, body temperature, duration of symptoms, white blood cell count, C-reactive protein level, and presence of extraluminal free air, periappendiceal fluid and appendicolith. A scoring system was constructed, with a maximum possible score of 22 points. Of the 284 patients, 150 had a score of 6 points or less, of whom eight (5·3 per cent) had complicated appendicitis, giving a negative predictive value (NPV) of 94·7 per cent. The model based on ultrasound imaging included the same predictors except for extraluminal free air. The ultrasound score (maximum 19 points) was calculated for 312 patients; 105 had a score of 5 or less, of whom three (2·9 per cent) had complicated appendicitis, giving a NPV of 97·1 per cent. CONCLUSION: With use of novel scoring systems combining clinical and imaging features, 95 per cent of the patients deemed to have uncomplicated appendicitis were correctly identified as such. The score can aid in selection for non-operative management in clinical trials.

Comparison of Imaging Strategies with Conditional versus Immediate Contrast-Enhanced Computed Tomography in Patients with Clinical Suspicion of Acute Appendicitis.

OBJECTIVES: To compare the diagnostic accuracy of conditional computed tomography (CT), i.e. CT when initial ultrasound findings are negative or inconclusive, and immediate CT for patients with suspected appendicitis. METHODS: Data were collected within a prospective diagnostic accuracy study on imaging in adults with acute abdominal pain. All patients underwent ultrasound and CT, read by different observers who were blinded from the other modality. Only patients with clinical suspicion of appendicitis were included. An expert panel assigned a final diagnosis to each patient after 6 months of follow-up (clinical reference standard). RESULTS: A total of 422 patients were included with final diagnosis appendicitis in 251 (60 %). For 199 patients (47 %), ultrasound findings were inconclusive or negative. Conditional CT imaging correctly identified 241 of 251 (96 %) appendicitis cases (95 %CI, 92 % to 98 %), versus 238 (95 %) with immediate CT (95 %CI, 91 % to 97 %). The specificity of conditional CT imaging was lower: 77 % (95 %CI, 70 % to 83 %) versus 87 % for immediate CT (95 %CI, 81 % to 91 %). CONCLUSION: A conditional CT strategy correctly identifies as many patients with appendicitis as an immediate CT strategy, and can halve the number of CTs needed. However, conditional CT imaging results in more false positives. KEY POINTS: • Conditional CT (CT after negative/inconclusive ultrasound findings) can be used for suspected appendicitis. • Half the number of CT examinations is needed with a conditional strategy. • Conditional CT correctly identifies as many patients with appendicitis as immediate CT. • Conditional imaging results in more false positive appendicitis cases.

Systematic review and meta-analysis of the open abdomen and temporary abdominal closure techniques in non-trauma patients.

BACKGROUND: Several challenging clinical situations in patients with peritonitis can result in an open abdomen (OA) and subsequent temporary abdominal closure (TAC). Indications and treatment choices differ among surgeons. The risk of fistula development and the possibility to achieve delayed fascial closure differ between techniques. The aim of this study was to review the literature on the OA and TAC in peritonitis patients, to analyze indications and to assess delayed fascial closure, enteroatmospheric fistula and mortality rate, overall and per TAC technique. METHODS: Electronic databases were searched for studies describing the OA in patients of whom 50% or more had peritonitis of a non-traumatic origin. RESULTS: The search identified 74 studies describing 78 patient series, comprising 4,358 patients of which 3,461 (79%) had peritonitis. The overall quality of the included studies was low and the indications for open abdominal management differed considerably. Negative pressure wound therapy (NPWT) was the most frequent described TAC technique (38 of 78 series). The highest weighted fascial closure rate was found in series describing NPWT with continuous mesh or suture mediated fascial traction (6 series, 463 patients: 73.1%, 95% confidence interval 63.3-81.0%) and dynamic retention sutures (5 series, 77 patients: 73.6%, 51.1-88.1%). Weighted rates of fistula varied from 5.7% after NPWT with fascial traction (2.2-14.1%), 14.6% (12.1-17.6%) for NPWT only, and 17.2% after mesh inlay (17.2-29.5%). CONCLUSION: Although the best results in terms of achieving delayed fascial closure and risk of enteroatmospheric fistula were shown for NPWT with continuous fascial traction, the overall quality of the available evidence was poor, and uniform recommendations cannot be made.

A systematic review of complicated diverticulitis in post-transplant patients.

BACKGROUND: Immunosuppression could increase the complication rate in patients with acute diverticulitis. This would justify a low threshold for elective sigmoid resection in these patients after an episode of diverticulitis. Well-documented groups of immunocompromised patients are transplant patients, in which many prospective studies have been conducted. OBJECTIVES: The aim of this systematic review is to assess the incidence of complicated diverticulitis in post-transplant patients. DATA SOURCE: We searched MEDLINE, EMBASE, CINAHL, and Cochrane databases for papers published between January 1966 and January 2014. STUDY SELECTION AND INTERVENTION: Publications dealing with post-transplant patients and left-sided diverticulitis were eligible for inclusion. The following exclusion criteria were used for study selection: abstracts, case-series and non-English articles. MAIN OUTCOME MEASURES: Primary outcome measure was the incidence of complicated diverticulitis. Secondary outcome was the incidence of acute diverticulitis and the proportion of complicated diverticulitis. Pooling of data was only performed when more than five reported on the outcome of interest with comparable cohorts. Only studies describing proportion of complicated diverticulitis and renal transplant studies were eligible for pooling data. RESULTS: Seventeen articles met the inclusion criteria. Nine renal transplant cohorts, four mixed lung-heart-heart lung transplant cohorts, two heart transplant cohorts, and two lung cohorts. A total of 11,966 post-transplant patients were included in the present review. Overall incidence of complicated diverticulitis in all transplantation studies ranged from 0.1 to 3.5%. Nine studies only included renal transplant patients. Pooled incidence of complicated diverticulitis in these patients was 1.0% (95% CI 0.6 to 1.5%). Ten studies provided proportion of complicated diverticulitis. Pooled incidence of acute diverticulitis in these studies was 1.7% (95% CI 1.0 to 2.7%). Pooled proportion of complicated diverticulitis among these patients was 40.1% (95% CI 32.2 to 49.7%). All studies were of moderate quality using the MINORS scoring scale. CONCLUSION: The incidence of complicated diverticulitis is about one in 100 transplant patients. Additionally when a transplant patient develops an episode of acute diverticulitis, a high proportion of patients have a complicated disease course.

Posterior circumflex humeral artery injury with distal embolisation in professional volleyball players: a discussion of three cases.

Presented are three cases of volleyball players with ischaemia of the hand due to arterial emboli originating from an injured posterior circumflex humeral artery (PCHA). An operative treatment with ligation of the PCHA was performed in all patients because of the proximity of the occlusion to the axillary artery. After a rehabilitation programme, all patients could return to their previous level of competition. During overhead motion, the PCHA is prone to injury in its position overlying the humeral head and its course through the quadrilateral space. Recognition of the vascular origin of these symptoms in athletes is important to prevent serious ischaemic complications. Signs of ischaemia might be subtle and may be misdiagnosed as musculoskeletal injuries. Therefore, the examining physician must have a high index of suspicion and awareness about these injuries is important.

Dispersal in the spiny damselfish, Acanthochromis polyacanthus, a coral reef fish species without a larval pelagic stage.

The spiny damselfish, Acanthochromis polyacanthus, is widely distributed throughout the Indo-Australian archipelago. However, this species lacks a larval dispersal stage and shows genetic differentiation between populations from closely spaced reefs. To investigate the dispersal strategy of this unique species, we used microsatellite markers to determine genetic relatedness at five dispersal scales: within broods of juveniles, between adults within a collection site (approximately 30 m(2)), between sites on single reefs, between nearby reefs in a reef cluster, and between reef clusters. We sampled broods of juveniles and adults from seven reefs in the Capricorn-Bunker and Swain groups of the Great Barrier Reef. We found that extra-pair mating is rare and juveniles remain with their parents until fledged. Adults from single sites are less related than broods but more related than expected by chance. However, there is no evidence of inbreeding suggesting the existence of assortative mating and/or adult migration. Genetic differences were found between all of the reefs tested except between Heron and Sykes reefs, which are separated only by a 2-km area of shallow water (less than 10 m). There was a strong correlation between genetic distance, geographical distance and water depth. Apparently, under present-day conditions spiny damselfish populations are connected only between sites of shallow water, through dispersal of adults over short distances. Assuming that dispersal behaviour has not changed, the broad distribution of A. polyacanthus as a species is likely based on historical colonization patterns when reefs were connected by shallow water at times of lower sea levels.