Assessing anatomical variations of the superior mesenteric artery via three-dimensional CT angiography and laparoscopic right hemicolectomy: a retrospective observational study.

OBJECTIVE: This study aimed to analyse the anatomical relationships and differences between the superior mesenteric vessels and their branches by reviewing a laparoscopic right hemicolectomy surgery video and comparing it with preoperative three-dimensional computed tomography (3D-CT) angiography and to verify the accuracy of 3D-CT vascular reconstruction techniques. METHODS: Surgical videos and preoperative imaging data of 52 patients undergoing laparoscopic right hemicolectomy were analysed to observe and summarize the probability of occurrence and adjacency of superior mesenteric vascular branches, and the lengths of specific sites of their branches were measured using the above two methods. RESULTS: Preoperative CT images and surgical video showed that the ileocolic artery (ICA) was present in 98.1% (51/52) and the ileocolic vein (ICV) was present in 100% (52/52), and ICA was present in 13.7% (7/51) of the ICV directly anteriorly, 13.7% (7/51) anteriorly superiorly, 3.9% (2/51) anteriorly inferiorly, 11.8% (6/51) directly posteriorly, 37.2% (19/51) post superiorly, and 19.7% (10/51) posteriorly inferiorly. In the surgical video, the probability of presence of the right colic artery (RCA) was 21.2% (11/52). On CT images, the RCA was present in 10 patients. The length of the origin of the middle colic artery (MCA) from its bifurcations was 2.33 ± 0.87 cm measured intraoperatively using a sterile isometric filament, and the length measured using 3D-CT vascular reconstruction was 2.36 ± 0.91 cm; the difference was not statistically significant (P = 0.348). The length of the MCA and ICA initiation points was 3.22 ± 0.75 cm measured intraoperatively using sterile isometric filaments and 3.36 ± 0.72 cm measured using 3D-CT vascular reconstruction, which was a statistically significant difference (P < 0.001). CONCLUSIONS: 3D-CT vascular reconstruction can accurately predict the vessels related to right hemicolectomy in most cases. It is an important method for preoperative prediction of superior mesenteric vessels, which can guide surgeons in the intraoperative vessel identification.

Mesenteric Ischemia.

Mesenteric ischemia occurs when perfusion of the visceral organs fails to meet normal metabolic requirements and subsequently results in abdominal symptoms such as diffuse postprandial pain, peritonitis, food fear, and weight loss. While generally divided into acute and chronic manifestations, mesenteric ischemia is commonly misdiagnosed at initial presentation due to the significant overlap with symptoms of other abdominal pathologies. Prompt recognition and diagnosis, mesenteric revascularization, and critical care management remain the mainstay of treatment in these patients for optimal outcomes. This review will highlight acute versus chronic mesenteric ischemia, their etiology, diagnostic criteria, treatment options, and will emphasize the joint role of the gastrointestinal and vascular surgeon in the timely management of this condition to prevent devastating outcomes.

Doppler ultrasound, a noninvasive tool for the study of mesenteric arterial flow in systemic sclerosis: a cross-sectional study of a patient cohort with review and meta-analysis of the literature.

Gastrointestinal involvement (GI) is a frequent and troublesome complication of systemic sclerosis (SSc), whose etiology is poorly understood, though it is hypothesized that autoimmunity and progressive vasculopathy may play a role. Vasculopathy is considered one of the main pathogenetic pathways responsible for many of the clinical manifestations of SSc, and, therefore, studying the principal splanchnic vessels (i.e., superior mesenteric artery-SMA and inferior mesenteric artery-IMA) with Doppler Ultrasound (DUS) may provide further insights into measuring the progression of vasculopathy, evaluating its possible association with SSc GI symptoms, and determining whether it plays a role in the development or severity of SSc GI disease. A cohort of SSc patients consecutively recruited underwent DUS examination, and associations with GI (UCLA-GIT 2.0 questionnaire) and extraintestinal SSc characteristics were evaluated. Semiquantitative DUS parameters (resistive index-RI and pulsatility index-PI), were applied for splanchnic vessel assessment in SSc patients and healthy subjects (HS). Moreover, a review and meta-analysis of the literature to understand which the values of the main semiquantitative DUS parameters (RI and PI) are both in SSc patients and HS has been conducted. Seventy-eight patients completed DUS examinations and clinical assessments. 30 (39%) were classified as diffuse cutaneous SSc (dcSSC), 35 (45%) as limited cutaneous SSc (lcSSc) and 13 (17%) as sine scleroderma. A significant difference was found both for SMA RI (p for trend = 0.032) and SMA PI (p for trend = 0.004) between patients with sine scleroderma, lcSSc and dcSSc, with lower values observed in the sine scleroderma and lcSSc groups. IMA RI and PI were significantly correlated with GI symptoms such as fecal incontinence (á¿¥ - 0.33, p = 0.008 and á¿¥ - 0.30, p = 0.021, respectively). By multivariate analysis, significant associations were confirmed between SMA RI and SMA PI and mRSS (ß 0.248, p = 0.030 and ß 2.995, p = 0.004, respectively) and with bosentan (ß 0.400, p = 0.003 and ß 3.508, p = 0.001, respectively), but not with anticentromere antibody (ACA). No significant differences were found between the weighted median values of SMA RI and SMA PI of SSc patients compared to those of HS that were derived from the meta-analysis of the literature (p = 0.72 and p = 0.64, respectively). This cross-sectional study confirms that the splanchnic vasculature of SSc patients can noninvasively been studied with DUS. Vascular splanchnic involvement correlates with the presence and/or severity of specific clinical features in SSc, including GI. Larger and prospective studies are needed to confirm these preliminary observations and to examine the role of DUS in SSc-risk stratification and GI progression and to obtain definitive data regarding both HS and SSc patients splanchnic DUS parameters.

The value evaluation of Nomogram prediction model based on CTA imaging features for selecting treatment methods for isolated superior mesenteric artery dissection.

OBJECTIVE: To evaluate value of Nomogram prediction model based on CTA imaging features for selecting treatment methods for isolated superior mesenteric artery dissection (ISMAD). METHODS: Symptomatic ISMAD patients were randomly divided into a training set and a validation set in a 7:3 ratio. In the training set, relevant risk factors for conservative treatment failure in ISMAD patients were analyzed, and a Nomogram prediction model for treatment outcome of ISMAD was constructed with risk factors. The predictive value of the model was evaluated. RESULTS: Low true lumen residual ratio (TLRR), long dissection length, and large arterial angle (superior mesenteric artery [SMA]/abdominal aorta [AA]) were identified as independent high-risk factors for conservative treatment failure (P < 0.05). The receiver operating characteristic curve (ROC) results showed that the area under curve (AUC) of Nomogram prediction model was 0.826 (95% CI: 0.740-0.912), indicating good discrimination. The Hosmer-Lemeshow goodness-of-fit test showed good consistency between the predicted curve and the ideal curve of the Nomogram prediction model. The decision curve analysis (DCA) analysis results showed that when probability threshold for the occurrence of conservative treatment failure predicted was 0.05-0.98, patients could obtain more net benefits. Similar results were obtained for the predictive value in the validation set. CONCLUSION: Low TLRR, long dissection length, and large arterial angle (SMA/AA) are independent high-risk factors for conservative treatment failure in ISMAD. The Nomogram model constructed with independent high-risk factors has good clinical effectiveness in predicting the failure.

Spontaneous Isolated Superior Mesenteric Arterial Dissection Treated with a Coronary Covered Stent: A Case Report.

Spontaneous isolated dissection of the superior mesenteric artery is rare with a wide spectrum of clinical symptoms. The management of isolated dissections mainly depends on the clinical symptomatology and imaging presentation. This case report describes a 51-year-old male presenting with persistent abdominal pain. Computed tomography angiography revealed an isolated superior mesenteric arterial dissection associated with severe true lumen stenosis and thrombosed false lumen with an ulcer-like projection. Definitive treatment was performed with a coronary covered stent to reopen the true lumen and completely exclude the false lumen.

Robot-Assisted Pancreaticoduodenectomy Using the Anterior Superior Mesenteric Artery-First Approach for Pancreatic Cancer.

BACKGROUND: The superior mesenteric artery (SMA)-first approach for pancreatic cancer (PC) is common surgical technique in pancreaticoduodenectomy. To date, few studies have reported SMA-first approach in robot-assisted pancreaticoduodenectomy (RPD). Herein, we present the anterior SMA-first approach for PC during RPD. PATIENT AND METHOD: A 75-year-old man with resectable PC underwent RPD after neoadjuvant chemotherapy. As pancreatic head tumor contacted with the superior mesenteric vein (SMV), the anterior SMA approach was applied. After the mesenteric Kocher maneuver, the jejunum was divided and the left side of the SMA was dissected. Subsequently, the anterior plane of the SMA was dissected. Following the division of branches from the mesenteric vessels, the SMA was taped, and the circumferential dissection around the SMA was performed to detach the pancreatic neck from the SMA completely. Finally, the dissection between the SMV and the tumor was performed under vascular control to remove the specimen. CONCLUSIONS: The anterior SMA-first approach can be optional in patients with PC undergoing RPD. This unique approach allows for the circumferential dissection around the SMA during RPD.

Revascularization of superior mesenteric artery occlusion via the arc of Buhler: A case report and literature review.

BACKGROUND: To report revascularization of a superior mesenteric artery (SMA) ostial occlusion via the Arc of Buhler. CASE REPORT: A 62-year-old female presented with 2 months of recurrent abdominal distension and postprandial pain. Computed tomography angiography (CTA) revealed ostial occlusion of the SMA with distal perfusion via the Arc of Buhler (connecting the celiac trunk and SMA). Conventional endovascular techniques failed. A 0.014 guidewire was passed retrograde through the occlusion via the Arc of Buhler. The guidewire was captured from the femoral sheath and balloon angioplasty with stent placement was performed. The patient had complete symptom resolution post-procedure. CONCLUSIONS: Retrograde revascularization via the Arc of Buhler is an effective method for treating the initial segment occlusion of the SMA.

Evaluation of Endoplasmic Reticulum Stress in an Experimental Intestinal Ischemia-Reperfusion Model in Rats: The Role of Ozone Therapy and Trimetazidine.

AIM: The objective of the study was to assess the impact of ozone (O3) and trimetazidine on the intestines following ischemia-reperfusion (I/R) injury through the investigation of endoplasmic reticulum stress. METHODS: Forty Sprague Dawley rats were separated into five groups. The groups were named as follows: control, O3, I/R, I/R + trimetazidine (TMZ), and I/R + O3. The control group had laparotomy and exploration of the superior mesenteric artery (SMA) only. Furthermore, alongside laparotomy and SMA exploration, an intraperitoneal (i.p.) administration of a 0.7 mg/kg ozone-oxygen (O3-O2) combination was given to the O3 group. In the experimental groups, the SMA was blocked with the silk suture ligation technique for a duration of 1 h and then restored to normal blood flow for another hour. In the I/R + O3 group, ozone was delivered i.p. at a dosage of 0.7 mg/kg, 30 min after ischemia. In the I/R + TMZ group, a dose of 20 mg/kg/day of trimetazidine was administered orally via gavage for a duration of 7 days, beginning 1 week prior to the induction of ischemia. Intestinal tissues were taken to assess indicators of intestinal mucosal injury and oxidative stress. RESULTS: The level of the lipid peroxidation marker malondialdehyde (MDA) was significantly reduced in the experimental groups as compared to the I/R group (p < 0.05). The experimental groups had considerably greater levels of glutathione (GSH), which reflects antioxidant capacity, compared to the I/R group (p < 0.05). Nevertheless, the concentration of GSH was observed to be increased in the I/R + O3 group in comparison to the I/R + TMZ group (p < 0.05). The histopathological damage score showed a substantial decrease in the experimental groups as compared to the I/R group (p < 0.05). The I/R + O3 group had the lowest injury score. The experimental groups exhibited significantly reduced positivity of the endoplasmic reticulum (ER) stress markers C/EBP homologous protein (CHOP) and glucose-regulated protein (GRP)-78 compared to the I/R group (p < 0.05). CONCLUSIONS: The findings provide evidence for the potential advantages of utilizing ozone therapy in the treatment of intestinal ischemia-reperfusion injury. Additionally, they propose that ozone should be assessed in more extensive clinical trials in the future as a therapeutic agent that can disrupt endoplasmic reticulum stress.

Endovascular Intervention for Acute Superior Mesenteric Artery Occlusion Following COVID-19 Pneumonia: Two Case Reports.

COVID-19 patients may experience acute mesenteric ischaemia. Identifying acute mesenteric ischaemia is challenging, particularly as initial symptoms are often vague and easily overlooked. Early detection and immediate intervention to restore blood flow can prevent these severe consequences. Presented in this report are two cases of superior mesenteric artery (SMA) thrombosis following severe acute respiratory syndrome coronavirus 2 infection. CT scans demonstrated SMA thrombosis in both patients, with no evidence of bowel necrosis. Endovascular intervention with self-expanding stent placement was performed after angiographic confirmation of the diagnosis. At 6-month follow-up, both patients remained asymptomatic on dual antiplatelet therapy. Atypical gastrointestinal manifestations in COVID-19 patients should raise suspicion for uncommon complications, such as SMA thrombosis. For SMA occlusion without associated bowel necrosis, endovascular therapy represents a viable treatment approach.

Case Report: Superior mesenteric artery vasculitis causing aneurysm following COVID-19 infection.

Objective: Arteritis refers to all infectious and non-infectious conditions that lead to inflammation of the arterial wall. However, little is known about its presence in patients with coronavirus disease 2019 (COVID-19). Most patients improved with steroids along with conservative treatments in a few studies. We report our experience with superior mesenteric artery (SMA) arteritis causing an aneurysm following COVID-19 infection. Case presentation: A 66-year-old female patient who was infected with COVID-19 1 month prior presented with abdominal pain. A computed tomography scan revealed proximal SMA arteritis. Although preliminary antibacterial treatment was initiated, the follow-up CT revealed an aggressive and fast-growing 5.7-cm SMA aneurysm. Subsequently, an open interposition bypass of the SMA aneurysm was performed successfully. As the specimens retrieved during surgery showed no bacterial colonization in the tissue or blood cultures, the patient was discharged without complications. Conclusions: The mechanism of arteritis in patients with COVID-19 has not been elucidated. In the absence of evidence of bacterial infection in arteritis, it is necessary to consider the possibility of viral infection caused by COVID-19 during the COVID-19 pandemic era and start with high-dose steroid therapy promptly.

A case of superior mesenteric artery stenting for small intestinal ischaemia caused by superior mesenteric artery invasion of pancreatic cancer.

Superior mesenteric artery (SMA) invasion by a malignant tumour is a serious condition leading to intestinal ischaemia. Although SMA stenting has been reported to be useful for SMA dissection and stenosis caused by atherosclerotic plaque, SMA stenting for stenosis caused by malignant tumour invasion is rarely reported and uncertain. A 75-year-old woman presented intestinal ulcer and melena caused by SMA invasion of unresectable pancreatic cancer. The bare metal stent was implanted for the vessel stenosis, and a small intestinal ulcer was markedly improved after stenting. However, one and a half months after stenting the stent was occluded and a thrombectomy was performed. After thrombectomy, residual stenosis caused by tumour invasion was observed in the stent. The patient suddenly died 2 days after thrombectomy before additional covered stenting for residual stenosis. Stent implantation may be a treatment option for intestinal ischaemia caused by vessel invasion of malignant tumours. On the other hand, re-stenosis of the stent due to tumour ingrowth is a problem, and covered stenting is considered for long-term stent patency.

Performance of Prenatal Ultrasound Screening for the Relative Positioning of Mesenteric Vessels.

OBJECTIVES: Abnormal relative positioning of the superior mesenteric artery (SMA) and vein (SMV) can lead to intestinal malrotation that predisposes to midgut volvulus. The aim of this study was to assess the prenatal ultrasound ability to visualize the relative position of SMA and SMV in normal pregnancies. METHODS: Prospective cohort study performed in Montpellier University Hospital Centre, including 80 fetuses during routine 3rd trimester ultrasound scan. For each fetus included, the relative position of the vessels on an axial image was defined as SMV on the right, forward, or on the left of SMA. Doppler imaging was additionally used if necessary. Data were compared to the neonatal abdominal scans performed by pediatric radiologist. RESULTS: The superior mesenteric vessels were identified in 79 fetuses. Prenatal findings showed a usual relative position of the vessels, that is, the vein on the right of the artery, in 96.2%. In 2 cases, the vein was strictly in front of the artery, and in 1 case, the vein was on the left side of the artery. Seventy-four neonates were examined and comparison with prenatal finding showed a perfect agreement (Kappa coefficient of 100%). An intestinal malrotation was postnatally diagnosed corresponding to the case where vein was on the left side of the artery. CONCLUSION: This study showed that the relative position of the SMA and SMV could be assessed using ultrasound prenatal examination with a perfect agreement with postnatal findings. In case of abnormal vessels positioning more examinations should be promote including prenatal MRI and postnatal conventional radiologic examinations to confirm intestinal malrotation.

Concurrent Encounter of Superior Mesenteric Artery Syndrome and Nutcracker Syndrome in a Young Female Patient: A Case Report and Literature Review.

Superior mesenteric artery (SMA) syndrome causes duodenal obstruction between the SMA and aorta, which culminates into bowel obstruction. Meanwhile, nutcracker syndrome (NCS) involves left renal vein compression between the aorta and SMA, categorized by the compression site. We present a 15-year-old female with no prior medical or surgical history who displayed early signs of the rarely coexisting SMA and nutcracker phenomena, which were managed symptomatically along with nutritional support to reach her optimal body mass index.

A Delayed Presentation of Superior Mesenteric Artery Syndrome Treated With Robotic-Assisted Strong Procedure.

Superior mesenteric artery (SMA) syndrome, also known as Wilkie's syndrome, is a rare condition resulting from compression of the third portion of the duodenum between the aorta and the superior mesenteric artery. When symptomatic, this compression may result in nausea, vomiting, epigastric discomfort, and weight loss, requiring clinical attention and imaging to make the diagnosis. Typically, SMA syndrome presents in young females and is associated with an underlying condition such as anorexia nervosa, cachexia, postoperative development after scoliosis surgery, etc. In this report, we present the case of an atypical delayed presentation of SMA syndrome in an 84-year-old male who had epigastric pain, nausea, intermittent vomiting, and a 30-pound weight loss over two years. SMA syndrome was diagnosed on a computed tomography (CT) scan by a decreased angle between the superior mesenteric artery and abdominal aorta, and treatment with a robotic-assisted strong procedure was performed. The patient was followed postoperatively in the clinic and tolerated the procedure well.

Morphology of True Lumen and Surgical Outcomes of Acute Type A Aortic Dissection Repair with Superior Mesenteric Artery Malperfusion.

BACKGROUND: Acute type A aortic dissection (ATAD) can cause visceral malperfusion. Central aortic repair may resolve malperfusion but some require further intervention. This study aimed to review outcomes after ATAD presenting with visceral malperfusion and to evaluate the predictive value of true lumen (TL) morphologies in preoperative computed tomography (CT) for persistent superior mesenteric artery (SMA) ischemia after central repair. METHODS: Open surgical repair of ATAD performed between 2008-2023 at our institution was retrospectively reviewed. Patients with central repair first approach were included for analysis. Patients with inadequate CT scan data to assess luminal morphology were excluded. TL morphology was reviewed at the diaphragm level and categorized as concave or convex. The malperfusion pattern, static vs. dynamic, was assessed at SMA orifices. Data were analyzed using a contingency table and parametric and nonparametric methods. RESULTS: A total of 543 open ATAD repairs were performed. Of these, 263 patients were eligible under the inclusion criteria and, subsequently, analyzed. The mean age was 57±14, and 83 (31%) patients were female. SMA malperfusion developed in 42 (16%) of the 263 patients, including 26 patients with dynamic obstruction, 6 patients with static obstruction, and 10 patients with dynamic and static obstruction. Regarding dissection flap morphology, 78 patients (30%) exhibited concave morphology, while 185 patients (70%) had convex morphology. TL diameter was significantly larger in convex than concave (concave: 6 mm vs. convex: 16 mm, p<0.0001). The prevalence of clinically significant SMA malperfusion was higher in concave-shaped TL (concave 41% vs. convex 5%, p<0.0001). Dynamic SMA obstruction was more frequently observed in the concave group (concave 72% vs. convex 30%, P <0.001). However, significantly more patients with convex-shaped TL required bowel resection than concave (concave 13% vs. convex 70%, p<0.001). The operative mortality was higher in the convex group, although statistically insignificant (concave 19% vs. convex 50%, p=0.0059). CONCLUSION: Central repair first strategy could resolve more than 80% of SMA malperfusion in ATAD when the TL is concave-shaped at the level of the diaphragm. Convex-shaped TL morphology was associated with less incidence of SMA malperfusion but was more frequently associated with static obstruction and higher incidence of bowel resection. The morphology evaluation of the TL at the diaphragm level may be simple and beneficial for surgical planning for ATAD presenting with SMA malperfusion.

Mycotic superior mesenteric artery aneurysm with impending rupture due to infective endocarditis.

A 49-year-old woman with tachycardia was referred to our institution. Transthoracic echocardiography revealed severe mitral regurgitation, and surgery was planned. While awaiting surgery, she developed a fever. Transthoracic echocardiography and transesophageal echocardiography revealed vegetation on the mitral valve leaflet. Blood cultures were positive for Streptococcus anginosus. She was diagnosed with infective endocarditis, and antibiotics were administered. She experienced sudden abdominal pain 26 days after hospitalization. Contrast-enhanced computed tomography scan revealed a mycotic superior mesenteric artery aneurysm with impending rupture without intestinal ischemia, and aneurysm resection was performed. Mitral valve replacement was performed on postoperative day 10, with uneventful postoperative healing.

Successful Treatment of a Patient with Hepatic Portal Vein Gas after Radiofrequency Ablation of Atrial Fibrillation: A Case Report.

BACKGROUND: Transcatheter radiofrequency ablation is one of the main treatments for atrial fibrillation, but related complications of this surgery are uncommon. CASE PRESENTATION: Here, we report a 70-year-old elderly male patient with atrial fibrillation who experienced severe abdominal pain early after undergoing radiofrequency ablation; related imaging examinations suggested that the patient had intestinal edema and thickening, combined with hepatic portal vein gas accumulation. The reason was that the patient experienced intestinal necrosis due to superior mesenteric artery embolism related to radiofrequency surgery. The surgeon suggested laparotomy for exploration. However, after multidisciplinary consideration, we ultimately chose conservative treatment. After fasting, gastrointestinal decompression, spasmolysis, pain relief, somatostatin inhibition of intestinal edema, antiinfection, and anticoagulation, the patient's condition improved, and he was discharged. We followed the patient for 1 month after discharge, and there was no special discomfort. CONCLUSION: Hepatoportal vein gas accumulation after radiofrequency ablation of atrial fibrillation is rare, and imaging findings have important guiding significance for the diagnosis and treatment of the disease.

Rare Superior Mesenteric Artery Syndrome in an Eight-Year-Old Girl With Henoch-Schönlein Purpura: A Case Report.

Henoch-Schönlein purpura (HSP) is a systemic vasculitis characterized by palpable purpura, arthralgia or arthritis, GI symptoms, and renal involvement. Superior mesenteric artery (SMA) syndrome, a rare condition, occurs when the third part of the duodenum is compressed between the aorta and the SMA, leading to upper intestinal obstruction. This case report describes the clinical presentation, diagnostic process, and management of an eight-year-old girl with HSP complicated by SMA syndrome. The patient initially presented with abdominal pain and vomiting, eventually developing the characteristic rash of HSP. While initial management was supportive, her condition deteriorated. Treatment with intravenous methylprednisolone resulted in significant symptom improvement and resolution of both SMA syndrome and HSP manifestations. This case highlights the need to recognize SMA syndrome as a potential complication of HSP and demonstrates the effectiveness of steroid therapy in managing this condition. Further research is needed to develop comprehensive treatment guidelines for HSP patients with SMA syndrome.

Wilkie's syndrome in a patient with Duchenne's muscular dystrophy: A Case Report.

Superior mesenteric artery syndrome, or Wilkie's syndrome, is one of the rarest gastrointestinal disorders known to medical science. It is characterized by the vascular clamp of the third portion of the duodenum, between the superior mesenteric artery and the aorta. It presents as an uncommon cause of upper intestinal obstruction. Imaging is required, preferably with a contrast-enhanced CT or an MRI; conservative management is preferred, leaving surgery for the most complex cases. We present the case of a 34-year-old man with Duchenne's muscular dystrophy and a history of substantial weight loss after hospital admission for aspiration pneumonia. He underwent an abdominal CT scan that showed enlargement of the stomach, the second and third parts of the duodenum; without observing masses, the patient received conservative management with a nasojejunal feeding tube. At the outpatient reevaluation, 1 month postdischarge, he became asymptomatic and had progressive weight gain.