Feasibility and safety of robotic-assisted surgical approach in median arcuate ligament syndrome-a systematic review.

Median arcuate ligament syndrome (MALS) is rare syndrome and is diagnosis of exclusion. Though first robotic median arcuate ligament release (MALR) was described in 2007, there are only a few case reports (CR), case series (CS), and retrospective cohort studies (RCS) in the published literature. The purpose of this study was to assess the feasibility and safety of robotic-assisted MALR (r-MALR). PubMed, Embase, and Cochrane databases were searched (last search December 2023) for articles reporting r-MALR. All studies including CR, CS, RCS reporting technical feasibility (operating time and rate of conversions), safety (intra-operative complications, blood loss, post-operative complications), and outcome (length of stay [LoS]) were included (PROSPERO: CRD42024502792). A total of 23 studies (8-CR, 5-CS, 10-RCS) with total 290 patients were available in the literature. Except 1-RCS, all studies reported age and mean age for CR was 40.38 ± 17.7, 36.08 ± 15.12 for CS, 39.72 ± 7.35 years for RS; except 2-RCS, all studies reported gender distribution and there were 57 males and 214 females. Operating time: 3-CR, 4-CS, 9-RCS reported operating time, and mean time was 111 ± 54, 131.69 ± 7.51, 117.34 ± 35.03 min, respectively. Conversion rate: All studies reported data on conversion and only four (1.37%) cases were converted-one to laparoscopic approach, three to open approach (1-inadvertent celiac arteriotomy, 2-reasons not mentioned). Intraoperative complications: only 5-CR, 4-CS, and 9-RCS reported data on intra-operative complications, and there were only 6 complications (1.5%): 1-inadvertent celiac arteriotomy converted to open; 3-unnamed vascular injuries (2 managed robotically, 1 converted to open); 1-bleeding managed robotically; there were no other reported injuries. Estimated blood loss ranged from 5 to 30 ml. Post-operative complications: 5-CR, 4-CS, 8-RCS described post-operative complications in 21 (7%) patients. Twenty cases were grade I, one was grade IIIa, and all managed successfully. LoS stay: 2-CR, 4-CS, 10-RCS reported LoS and overall, it was 2 days. r-MALR is reasonable, technically feasible, safe, and has acceptable outcomes. In addition, robotic approach provided superior vision, improved dexterity, precise, and easy circumferential dissection.PROSPERO registration: The protocol was registered in the PROSPERO database (CRD42024502792).

Clinical outcomes after surgical decompression of median arcuate ligament syndrome-An observational study.

BACKGROUND AND OBJECTIVES: Median arcuate ligament syndrome is caused by compression and stenosis of the celiac artery. Incision of the median arcuate ligament improves persistent abdominal symptoms. The study aimed at evaluating the outcomes in patients who underwent median arcuate ligament syndrome decompression using a self-report questionnaire. METHODS: This single-center retrospective study included patients with median arcuate ligament syndrome who underwent decompression surgery between April 2021 and February 2023. The medical records were retrospectively reviewed. RESULTS: Ten patients were included in the study. Laparotomy and laparoscopic surgeries were performed in seven and three patients, respectively. The median operation time was 147 minutes. The median hospitalization period after the operation was seven days. The degrees of celiac artery stenosis before and after surgery were compared and the per cent diameter stenosis did not significantly improve; five of 10 patients (50%) had > 50% stenosis in the celiac artery after the operation. Compared to the baseline, the scores of upper gastrointestinal symptoms significantly improved during the six months' period (p < 0.001). Additionally, we evaluated the influence of post-operative per cent diameter stenosis and divided the patients into two groups (≥ 50% vs, < 50%). The scores of upper gastrointestinal (GI) symptoms in both groups improved significantly from baseline. However, the symptomatic improvement at six months in the post-operative per cent diameter stenosis < 50% group was significantly greater than that in the ≥ 50% group (p = 0.016). The scores of lower gastrointestinal symptoms did not change significantly during the six-month period. CONCLUSION: Decompression surgery for median arcuate ligament syndrome could improve upper gastrointestinal symptoms regardless of the post-operative per cent diameter stenosis.

[A Case of Adenocarcinoma of Pancreatic Head of Liver Disfunction after Pancreaticoduodenectomy with Celiac Artery Stenosis Treated by Urgent Median Arcuate Ligament Release].

This patient visited our hospital for the purpose of detailed examination of prostate cancer in his seventies. Abdominal contrast-enhanced computed tomography(CT)revealed a low-density mass of 2 cm in the pancreatic head. He was diagnosed with pancreatic cancer. Pancreaticoduodenectomy was performed after 2 courses of gemcitabine and S-1 therapy were performed as neoadjuvant chemotherapy. An intraoperative clamp test of the gastroduodenal artery showed that the pulsation of the common hepatic artery and the proper hepatic artery was weak but sufficient, so the gastroduodenal artery was cut and the operation was completed as planned. A blood test on the 1st day after the operation showed elevated levels of AST 537 U/L, ALT 616 U/L, and 7 hours later blood sampling showed further increases in AST 1,455 U/L, ALT 1,314 U/L. After a detailed review of the preoperative CT, celiac artery stenosis due to compression of the arcuate ligament was suspected, and urgent median arcuate ligament release was performed on the same day. Dissection of the arcuate ligament significantly improved the pulsation of the common hepatic artery and proper hepatic artery. Postoperatively, hepatic enzymes improved and ISGPS showed Grade B pancreatic juice leakage, but the patient was discharged from the hospital on the 49th postoperative day without any other complications. He took S-1 as adjuvant chemotherapy, and no signs of recurrence have been observed 9 months after the operation.

Intraoperative assessment of blood flow using transabdominal ultrasound during laparoscopic surgery of celiac artery compression syndrome.

Surgical treatment of celiac artery (CA) compression syndrome (CACS) is to release the median arcuate ligament (MAL) by removing the abdominal nerve plexus surrounding CA. In laparoscopic surgery of CACS, objective intraoperative assessment of blood flow in CA is highly desirable. We herein demonstrate a case of laparoscopic surgery of CACS with use of intraoperative transabdominal ultrasound. A 52-year-old woman was presented with epigastric pain and vomiting after eating. Contrast-enhanced computed tomography demonstrated significant stenosis at the origin of CA. Doppler study of CA was also performed, and she was diagnosed as CACS. Laparoscopic surgery was performed, and the MAL was divided. And then, Doppler study using intraoperative transabdominal ultrasound confirmed the successful decompression of CA. This patient was discharged on postoperative day 11, and her symptoms was improved. Intraoperative assessment of blood flow in CA using transabdominal ultrasound was a simple and useful method for laparoscopic surgery of CACS.

Median arcuate ligament release at the time of pancreaticoduodenectomy or total pancreatectomy.

BACKGROUND: Celiac artery compression can complicate the performance of pancreaticoduodenectomy or total pancreatectomy due to the need for ligation of the gastroduodenal artery. Median arcuate ligament release restores normal arterial flow to the liver, spleen, and stomach and may avoid complications related to poor perfusion of the foregut. METHODS: All patients who underwent median arcuate ligament release for celiac artery compression at the time of pancreatectomy between 2009 and 2023 were reviewed. Pre- and postoperative computed tomography was used to categorize celiac artery compression by the extent of compression (types A [<50%], B [50%-80%], and C [>80%]). RESULTS: Of 695 patients who underwent pancreatectomy, 22 (3%) had celiac artery compression, and a majority (17) were identified on preoperative imaging. Median celiac artery compression was 52% (interquartile range = 18); 8 (36%) patients had type A and 14 (64%) had type B compression with a median celiac artery compression of 39% (interquartile range = 18) and 59% (interquartile range = 14), respectively (P < .001). Postoperative imaging was available for 20 (90%) patients, and a reduction in the median celiac artery compression occurred in all patients: type A, 14%, and type B, 31%. Complications included 1 (5%) death after hospital discharge, 1 (5%) pancreatic fistula, 1 (5%) delayed gastric emptying, and 4 (18%) readmissions. No patient had evidence of a biliary leak or liver dysfunction. CONCLUSION: Preoperative computed tomography allows accurate identification of celiac artery compression. Ligation of the gastroduodenal artery during pancreaticoduodenectomy or total pancreatectomy in the setting of celiac artery compression requires median arcuate ligament release to restore normal arterial flow to the foregut and avoid preventable complications.

Clinical Outcomes after Median Arcuate Ligament Release in Patients Responsive to Celiac Plexus Block.

PURPOSE: To determine if symptom relief with celiac plexus block (CPB) is associated with favorable clinical outcomes after median arcuate ligament release (MALR) surgery. MATERIALS AND METHODS: A retrospective review was performed from January 2000 to December 2021. Fifty-seven patients (42 women, 15 men; mean age, 43 years [range, 18-84 years]) with clinical and radiographic features suggestive of median arcuate ligament syndrome (MALS) underwent computed tomography (CT)-guided percutaneous CPB for suspected MALS. Clinical outcomes of CPB and MALR surgery were correlated. Adverse events were classified according to the Society of Interventional Radiology (SIR) guidelines. RESULTS: CT-guided percutaneous CPB was successfully performed in all 57 (100%) patients with suspected MALS. A cohort of 38 (67%) patients showed clinical improvement with CPB. A subset of 28 (74%) patients in this group subsequently underwent open MALR surgery; 27 (96%) responders to CPB showed favorable clinical outcomes with surgery. There was 1 (4%) CPB-related mild adverse event. There were no moderate, severe, or life-threatening adverse events. CONCLUSIONS: Patients who responded to CPB were selected to undergo surgery, and 96% of them improved after surgery.

Laparoscopic Median Arcuate Ligament Release: Surgical Technique and Clinical Outcomes.

BACKGROUND: Median arcuate ligament syndrome (MALS) is characterized by a constellation of symptoms related to the compression of the celiac artery trunk. Laparoscopic release of the ligament has demonstrated its effectiveness in alleviating these symptoms while showing lower postoperative complication rates, reduced hospital stays, and improved clinical outcomes. This study describes a single institution's experience with this procedure and reports on the preoperative assessment, surgical technique, and clinical outcomes of patients with MALS. METHODS: We performed a retrospective chart review of all patients who underwent a primary laparoscopic MAL release (MALR) at a single high-volume academic institution from June 2021 to July 2023. Patient demographics, preoperative assessment, postoperative complications, and resolution of preoperative symptoms data were collected. RESULTS: A total of 30 patients underwent laparoscopic MALR, with 76.7% being female and a mean age of 33.4±16.3 years. The most common presenting symptom was postprandial epigastric pain (100%), followed by abdominal pain and nausea (83.3%), among others. The preoperative evaluation for all patients included a duplex mesenteric doppler and CT angiogram during inspiration and expiration and 3D reconstruction. Successful laparoscopic decompression of the celiac artery was achieved in 96.6% of cases, with only one conversion to an open procedure. There was only one reported early (<30 d postoperatively) complication with no subsequent late complications or mortality. None of the patients required reintervention or reoperation. Only 1 patient required postoperative celiac plexus/splanchnic block injection to alleviate pain. CONCLUSIONS: MALS can be effectively and safely managed using a laparoscopic approach when performed by an experienced minimally invasive surgeon. Further studies with longer follow-ups are needed to confirm the long-term effectiveness of this technique.

Characteristics and Trends in Median Arcuate Ligament Syndrome (MALS) Associated Visceral Artery Aneurysms: A Systematic Descriptive Review of the Literature.

Introduction: Median Arcuate Ligament Syndrome (MALS) is associated with true aneurysms, mainly of both the pancreaticoduodenal artery (PDA) and gastroduodenal artery (GDA). Although rare, their potential for rupture and adverse clinical outcomes warrants analysis. Prior studies suggest high rupture rates even for smaller aneurysms under 2 cm in this setting. We performed a systematic literature review, synthesising the evidence on visceral artery aneurysms related to MAL syndrome, with a focus on descriptive analyses of aneurysm size, presentation, rupture rates, and management. Methods: Literature search was performed using (Medline, EMBASE, Emcare and CINAHL). Inclusion criteria included true aneurysms secondary to MALS with or without rupture. The cases with pseudoaneurysms, concomitant pathologies eg, pancreatitis, conservatively managed aneurysms and articles with non-granular pooled data were excluded. Cases were assessed according to demographics, clinical presentation, aneurysm diameter, aneurysm rupture and management technique. Results: 39 articles describing 72 patients were identified. Aneurysm diameter in symptomatic patients was not significantly different from asymptomatic patients {21.0 and 22.3 mm respectively, P = .84}. Ruptured aneurysms were overall smaller than non-ruptured at presentation {12.3 mm v 30.8 mm respectively, P = .02}. Patients presented with abdominal pain (75.6%), nausea/vomiting (15.6%), hypotension (33.9%), shock (20.0%) and haemodynamic collapse (8.9%). 56.9% of all cases were managed with an endovascular approach, 19.4% were managed with an open surgical approach, and 23.6% were managed hybrid. Conclusion: This review suggests visceral artery aneurysms associated with median arcuate ligament rupture at variable sizes. Despite inability to clearly correlate size and rupture risk, our data supports prompt intervention irrespective of size, given the adverse outcomes. Further research is critically needed to clarify size thresholds or other predictors to guide management.

Pancreaticoduodenal Artery Aneurysm Complicated by Median Arcuate Ligament Syndrome.

PURPOSE: To highlight median arcuate ligament syndrome as a potential cause for celiac artery stenosis and pancreaticoduodenal artery aneurysm, and describe treatment options in this setting. CASE REPORT: A 63-year-old male presented with a pancreaticoduodenal artery aneurysm and concomitant celiac artery stenosis that was treated with celiac artery stenting and aneurysm coiling. He subsequently developed stent fracture and celiac artery occlusion secondary to previously unrecognized median arcuate ligament syndrome causing reperfusion of the aneurysm. This was treated with open median arcuate ligament release and aorta to common hepatic artery bypass with good clinical result and stable 20-month surveillance imaging. CONCLUSION: It is critical to recognize median arcuate ligament syndrome as a cause of celiac artery stenosis in the setting of pancreaticoduodenal artery aneurysm given the high risk of failure of endovascular stenting. Open aorto-hepatic artery bypass and endovascular aneurysm coiling should be the preferred approach in these patients.

[Diagnosis and treatment of Dunbar syndrome]. / Diagnostik und Therapie des Dunbar-Syndroms.

The rare Dunbar syndrome or medial arcuate ligament syndrome (MALS) is defined as compression of the celiac trunk and/or ganglion by the medial arcuate ligament. It is often diagnosed after patients have suffered for a long time and is characterized by intermittent food-related pain, nausea, and unexplained weight loss. After exclusion of other causes of the above symptoms by gastroscopy, colonoscopy, CT, or MRI, the gold standard for diagnosis is dynamic color-coded duplex sonography, which may be supplemented by CT or MR angiography. The treatment of choice is a laparoscopic division of the arcuate ligament at the celiac trunk, although percutaneous transluminal angioplasty (PTA) with stent implantation may be performed in cases of postoperative persistence of symptoms or recurrent stenosis. Since symptoms persist postoperatively in up to 50% of cases, strict indication and complete diagnosis in designated centers are of great importance for successful treatment.

First description of a histopathologic grading system and relationship to outcomes after robotic median arcuate ligament release with celiac ganglionectomy and lymphadenectomy.

BACKGROUND: Two dominating theories regarding median arcuate ligament syndrome include vascular and neurogenic etiologies from celiac artery and ganglion compression, respectively. Celiac ganglionectomy is not routine during surgery, and specimens are rarely excised; therefore, the extent of nerve involvement and histopathology are unknown. Our study aims to characterize histopathologic findings in median arcuate ligament syndrome, establish a histopathologic grading system, and correlate with clinical outcomes. METHODS: Robotic median arcuate ligament release, celiac ganglionectomy, and lymphadenectomy were performed with specimens excised and stained using hematoxylin & eosin, trichrome, and S100. Neurofibrosis, adiposity, and reactive changes were described, a grading scale was developed, and results were analyzed with clinical outcomes. RESULTS: Fifty-four patients were evaluated, of whom 36 met inclusion criteria (81% female, 34.9 [25.9-47.5] years, body mass index 23.5 [19.6-28.1] kg/m2). Histopathologic evaluation revealed fibrosis (hematoxylin & eosin and trichrome median score 1.5 [0-2.5]), reactive lymphadenopathy (89%), intraparenchymal nerves (31%), and lipogranulomas (31%). Greater fibrosis was associated with a lack of preoperative celiac plexus block relief (100% vs. 30%, P = .044) and lower postoperative celiac artery velocities (198 vs 323 cm/s, P = .02). Intraparenchymal nerves were associated with greater decreases in pre to postoperative velocities (161 vs 84 cm/s, P = .037). Symptoms improved in 28 patients (78%). CONCLUSION: We developed the first histopathologic grading system and identified unique findings of intraparenchymal nerves and lipogranulomas. Histopathologic abnormalities were associated with objective improvement and symptomatic relief postoperatively. These findings support nerve compression and inflammation as predominant contributors to median arcuate ligament syndrome pain, celiac ganglia resection to treat symptoms, and continued histopathologic analysis to better elucidate median arcuate ligament syndrome etiology.

The anatomical relationship between the celiac artery and the median arch ligament in degenerative spinal surgery.

BACKGROUND: This study aimed to characterize the anatomical relationship between the spine, the celiac artery (CA), and the median arcuate ligament using preoperative contrast-enhanced computed tomography (CT) images of patients with spinal deformity who underwent surgical correction. METHODS: This retrospective study included 81 consecutive patients (34 males, 47 females; average age: 70.2 years). The spinal level at which the CA originated, the diameter, extent of stenosis, and calcification were determined using CT sagittal images. Patients were divided into two groups: CA stenosis group and non-stenosis group. Factors associated with stenosis were examined. RESULTS: CA stenosis was observed in 17 (21%) patients. CA stenosis group had significantly higher body mass index (24.9 ± 3.9 vs. 22.7 ± 3.7, p = 0.03). In the CA stenosis group, J-type CA (upward angling of the course by more than 90° immediately after descending) was more frequently observed (64.7% vs. 18.8%, p < 0.001). The CA stenosis group had lower pelvic tilt (18.6 ± 6.7 vs. 25.1 ± 9.9, p = 0.02) than non-stenosis group. CONCLUSIONS: High BMI, J-type, and shorter distance between CA and MAL were risk factors for CA stenosis in this study. Patients with high BMI undergoing fixation of multiple intervertebral corrective fusions at the thoracolumbar junction should undergo preoperative CT evaluation of the anatomy of CA to assess the poteitial risk of celiac artery compression syndrome.

Pancreaticoduodenectomy combined gastroduodenal collateral reconstruction and preservation due to median arcuate ligament syndrome: technical notes with two surgical cases report (with video).

INTRODUCTION: Pancreaticoduodenectomy in patients with CA stenosis due to median arcuate ligament often required carefully collateral pathways management to avoid hepatic ischemic complications. CASES PRESENTATION: Case 1: A 63-year-old man was referred to our department because of jaundice with distal common bile duct tumor. Pancreaticoduodenectomy with left posterior SMA first approach and circumferential lymphadenectomy was performed. Case 2: A 48-year-old man was referred to our department because of right-upper-quadrant abdominal pain with Vater tumor. Laparoscopic pancreaticoduodenectomy with left posterior SMA first approach and circumferential lymphadenectomy was performed. Postoperatively, in all two cases, three-dimensional reconstruction images showed developed collateral pathways around the pancreatic head, and the CA was stenosis in 75% and 70% due to MAL, respectively. Intraoperatively, in all two cases, we confirmed poor blood flow in the common hepatic artery (CHA) by palpation and observation. So that in the first case, we have decided to proceed a no-touch technique of GDA segmental resection en bloc with the tumor and reconstructed with an end-to-end GDA anastomosis; in the second cases, we have decided to proceed gastroduodenal collateral preservation. When preserving these collateral pathways, we confirmed that the PHA flow remained pulsatile as an indicator that the blood flow was adequate. CONCLUSION: Celiac axis stenosis was a rare but difficult-to-managed condition associated with pancreaticoduodenectomy. Collateral pathways management depends on variety of collateral pathways.

Trauma-Induced Median Arcuate Ligament Syndrome is an Under-Recognized Source of Chronic Abdominal Pain.

Median arcuate ligament syndrome (MALS) can be a debilitating condition resulting in epigastric pain, nausea, difficulty eating due to postprandial pain, weight loss, and malnutrition in otherwise healthy individuals. The pain is caused by the compression of the celiac artery and neural ganglia by the median arcuate ligament as it attaches from the spine to the diaphragm. Diagnostic imaging, either duplex or angiography, can show the abnormality however, vague symptoms can lead to a missed diagnosis. While MALS is a known anatomical variation in the population, to our knowledge, has not been identified to be caused by trauma. Here, we present 4 patients who developed MALS following abdominal or spinal trauma whom all required surgery to alleviate lifestyle-limiting pain.

Outcomes of Median Arcuate Ligament Release: A Single Institution Retrospective Review.

BACKGROUND: Median arcuate ligament syndrome (MALS) is an uncommon diagnosis that is often associated with variable clinical presentation and inconsistent response to treatment. Due to the nature of MALS, the optimal treatment modality and predictors of outcomes remain unclear. METHODS: A retrospective review was performed of all median arcuate ligament release (MALR) procedures at a single academic institution between 2000 and 2020. Variables examined included patient demographics, symptom characteristics, operative technique (open, robotic, laparoscopic), patient symptoms before release, symptom relief within 1 year, and recurrence of symptoms between release and last clinical follow-up. RESULTS: During the study period, 47 patients (75% female, mean age 42.1 years) underwent MALR with 19 (36%) robotic, 18 (34%) open, 14 (26%) laparoscopic, and 2 (4%) laparoscopic converted to open procedures. Abdominal pain, weight loss, and nausea and vomiting were the most common symptoms. Postoperatively, 19 (40%) had complete symptom relief within 1 year, 18 (38%) had partial relief, and 10 (21%) had no symptom improvement. 6 were excluded due to loss of follow-up. Laparoscopic and open procedures had the highest rate of complete symptom relief by year 1 with 7 (58%) and 8 (50%) respectively. Twenty-one (57%) patients had recurrence with the greatest rate of recurrence seen among laparoscopic (80%), compared to robotic (57%) and open (38%). Patients reporting a weight loss of 20 pounds or more before surgery were more likely to have partial or complete symptom relief after 1 year compared to those reporting less than 20-pound weight loss (92% vs. 64%). Furthermore, 84% of patients younger than 60 years old reported partial or complete symptom relief compared to only 56% of those older than 60. CONCLUSIONS: MALS continues to be a rare disorder with widely variable surgical outcomes, requiring further study. While our patients presented with several gastrointestinal symptoms, the most common was postprandial pain. Our center employed laparoscopic, open, and robotic operative techniques with varying success rates, in terms of symptom relief and recurrence. Consistent with current literature, our study found greater surgical success among patients younger than 60 years regardless of operative technique. This suggests the need for better predictors to determine which patients are the most likely to have complete or prolonged remission of symptoms following MALR.

Robotic Approach for Median Arcuate Ligament Relief: A Case Report and Literature Review.

Introduction: There are very few reported cases of robotic surgery for median arcuate ligament syndrome. This clinical condition develops when the root of the celiac trunk is compressed by the median arcuate ligament of the diaphragm. The symptoms that typically accompany this syndrome are: discomfort and pain in the upper abdominal region, particularly after eating, and weight loss. During the diagnostic process, it is important to rule out other potential causes and demonstrate compression using any imaging technique available. Transecting the median arcuate ligament is the primary focus of the surgical treatment. We report a case of robotic MAL release, focusing on the particular aspects of the surgical technique. A literature review was also performed on the topic of robotic approach for MALS. Clinical case: A 25-year-old woman presented with sudden onset severe upper abdominal pain after physical activity and eating. She was then diagnosed with median arcuate ligament syndrome by imagistic means with computer tomography, doppler ultrasound, and angiographic computed tomography. After conservative management and careful planning, we performed robotic division of median arcuate ligament. The patient was discharged from the hospital without any complaint on the second day after surgery. Subsequent imaging studies revealed no residual celiac axis stenosis. Conclusion: The robotic approach is a safe and feasible treatment modality for median arcuate ligament syndrome.

Minimally Invasive Surgery for Median Arcuate Ligament Syndrome and Celiac Artery Stenosis.

Median arcuate ligament syndrome (MALS) is a pathology commonly reported in educational literature, although in reality it is scarcely seen. Herein, we present the case of a 48-year-old female patient who presented with nausea, vomiting, and unintentional weight loss. After thorough work up of her symptoms through a variety of different modalities, MALS was confirmed and she underwent surgical release via a minimally invasive approach. The authors of this article feel that this case is important to present due to paucity of reported cases in the literature. In addition, this patient was exceptionally unique to report as we selected to perform a slight adaptation of a minimally invasive approach, while there are multiple different treatment techniques and management plans that have previously been described in a variety of different literatures and require further discussion.