Variations Of Hepatic Artery Research Articles

Surgical anatomy of the vasculobiliary apparatus at the hepatic hilum as applied to liver transplantations and major liver resections

IntroductionTo evaluate the hepatic arterial, bile duct and portal venous anatomy as applicable to major liver resections. MethodsThe study was conducted on 100 formalin fixed adult cadaveric livers. The hepatic arterial, bile ductal and portal venous anatomy of the liver was dissected from their origin up to their segmental branching. Left and right hemilivers were compared with regard to the single and multiple vascular or biliary pedicles entering their respective hemilivers. ResultsThe anatomy of all the three structures, ie., hepatic artery, bile duct and portal vein were conventional in 39% and variant, i.e., “triple” anomaly in 4% of liver specimens. In 57% liver specimens, the anatomy of one or two structures was variant and individual variation of hepatic artery, bile duct and portal vein anatomy was observed in 34%, 42% and 14% of livers respectively. The anatomy of hepatic artery was classified according to the Michels classification. In 9% of livers, rare variations not included in Michels classification was found. The drainage pattern of bile ducts was grouped according to Blumgart’s classification. In 11% of livers, rare variations not included in Blumgart’s classification were found. The branching pattern of main portal vein was classified according to the Akgul’s classification. In 1% of livers, rare variations in the right portal vein were found. DiscussionIn the present study, the vasculobiliary anatomies of liver were highly complex with the existence of many anatomic variations. The increasing complexity of hepatic surgical procedures necessitates appropriate knowledge of these anatomic variations.

Awareness of hepatic arterial variants is required in surgical oncology decision making strategy: Case report and review of literature.

Surgery for the treatment of pancreatic cancer remains the gold standard, however, the identification of the vascular supply of the pancreas and the nearby organs remains a crucial difficulties in a curative resection. During pancreatic head resection for carcinoma dissection of regional arterial vasculature is mandatory. Normal coeliac and hepatic arterial anatomy occurs in ~50–70% of patients and multiple variations have been described. Knowledge of multiple arterial anomalies is essential in hepato-pancreatico-billary surgery to avoid unnecessary complications. The present study presents coeliac trunk and common hepatic artery (CHA) anomalies along with their clinical importance, as reviewed according to the available literature. Patients diagnosed with cancer of the pancreatic head were hospitalized for staging and planning of radical surgical therapy. Computed tomography (CT) revealed a large tumour mass in the head of the pancreas and CHA, which branched directly from the superior mesenteric artery. A three-dimensional CT reconstruction revealed a demonstrative vascular anomaly, which was confirmed during an operation. Despite the anomalous origin of the CHA, pylorus preserving pancreatoduodenectomy and regional lymph node dissection without intraoperative complications was performed in each case. The patient's postoperative clinical course was uneventful and adjuvant chemotherapy could be administered without delay. In the multidisciplinary treatment of pancreatic carcinoma the surgeon and radiologist must be aware of the aberrant anatomy in order to avoid potential complications. As CT scans used for the preoperative staging are of diagnostic value for vascular anomaly, it is required for appropriate surgical decision making.

Anatomic variation and introperative disposal of right hepatic artery in pancreaticoduodenectomy

Anatomic variation of right hepatic artery (RHA) is not rare in clinical. we retrospective reviewed the clinical data of 179 patients underwent pancreaticoduodenectomy (PD) between January 2012 and June 2017 in Department of Hepatobiliary Surgery, Hospital of Binzhou Medical University, Shandong Province, China. 28 patients from them presented variant RHA including replaced RHA (rRHA) and accessory RHA (aRHA), and the incidence of aberrant RHA was about 15.64%. The variation was confirmed with preoperative imaging in 25 cases by contrast-enhanced computed tomographic (CT) and the preoperative diagnostic accuracy was up to 89.29% in our study. The duration of operation in variant group was prolonged than normal and there was a statistical difference between two groups, no difference was demonstrated in estimated amount of blood loss and postoperative complications including biliary fistula, pancreatic fistula, chylous fistula, intraperitoneal haemorrhage between two groups. It is essential for surgeons to be vigilant for rRHA or aRHA to avoid potentially disastrous complications and the best introperative disposal, only if transection and reconstruction is unavoidable, is to dissect and preserve despite it may cost much more time.

Anatomic variation of the right hepatic artery during laparoscopic cholecystectomy

Anatomic variation of the right hepatic artery during laparoscopic cholecystectomy

Evaluation of Variants in Hepatic Artery Anatomy on Conventional Angiography in Patients Undergoing Transarterial Chemoembolization (TACE): Experience at SIUT

Objective: The purpose of this research is to evaluate common and uncommon variant of hepatic arterial anatomy thatusually come across during Hepatic Angiographies.Study Design: Cross sectional study.Methods: This study included 50 patients having history of Hepatocellular Carcinoma from May to October 2015. Hepatic Angiography (Transarterial chemoembolization for management of Hepatoma and identification of classical and variant anatomy of hepatic artery) was evaluated in angiography unit. All procedures were performed on Digital Subtraction Angiography (DSA) machine (Toshiba KXO100 G). Selective DSA of the superior mesenteric artery and celiac trunk is performed initially to evaluate the frequency of normal and variant arterial anatomy and secondly to determine origin and course of tumor-feeding vessels. Evaluation of common and uncommon variants of hepatic arteries was done by using Michel’s classification as reference standard.

The prevalence of transpancreatic common hepatic artery and coexisting variant anatomy.

We studied the prevalence of the transpancreatic common hepatic artery (tp-CHA) and coexisting variant anatomy. The study group comprised 788 consecutive liver transplant donor candidates who had undergone thin-section multidetector-row computed tomography (MDCT) studies to investigate vascular anatomy. Multiplanar reformatted (MPR) images obtained from the arterial phase were retrospectively reviewed to assess the presence/absence of the tp-CHA. Five cases of tp-CHA with pancreaticobiliary tumors were also included in an investigation of the presence/absence of variant hepatic arteries, celiac stenosis, and circumportal pancreas. Three of the 788 (0.38%) donor candidates had a tp-CHA. Overall, eight tp-CHA cases were assessed for coexisting variant anatomy. Seven of these eight cases had a hepatomesenteric trunk, six had celiac stenosis, and two had a circumportal pancreas. The prevalence of the tp-CHA was 0.38% (approx. one in 260 in normal populations). A tp-CHA can commonly be associated with a hepatomesenteric trunk and celiac stenosis. A circumportal pancreas can also coexist with a tp-CHA. Clin. Anat. 31:598-604, 2018. © 2017 Wiley Periodicals, Inc.

Anastomotic loop between common hepatic artery and gastroduodenal artery in coexistence with an aberrant right hepatic artery.

Anatomical variations of the hepatic arteries are not uncommon. The anomalous hepatic arterial supply is of paramount importance in hepatobiliary, pancreatic or liver transplantation and in laparoscopic surgery. We describe an unusual case of a 66-year-old Greek male cadaver, where a rare anastomosis (in the form of an enlarged arterial loop, 4.84 mm in diameter) between the common hepatic artery (6.42 mm) and the gastroduodenal artery (GDA) (4.82 mm) coexisted with an aberrant right hepatic artery (ARHA) (6.38 mm) originating from the superior mesenteric artery. The proper hepatic artery was absent. The ARHA followed a route posterior to the portal vein and the common hepatic duct, entering the liver and supplying the right hepatic segment. A hypoplastic right gastric artery emanated from the GDA. Our case report highlights the combined variations of hepatic arteries and possible anastomoses emphasizing that a thorough knowledge of the classic and variable hepatic arterial anatomy are mandatory for surgeons and radiologists performing hepatic surgery and arteriography to avoid potential iatrogenic injuries in hepatobiliary and pancreas area and further medico-legal implications.

A rare variation of celiac trunk and hepatic artery complicating pancreaticoduodenectomy

Rationale:Anatomical variations of the celiac trunk and the hepatic artery are of considerable importance in hepatopancreatobiliary surgery, liver transplants, and radiological abdominal interventions.Patient concerns:Here, we report a 57-year-old man with 2 weeks of painless progressive jaundice. Preoperative imaging and cytology brush results suggested an ampullary tumor and common hepatic artery anomaly (CTA) was reported. The patient underwent pancreaticoduodenectomy (PD). Intraoperatively, the CHA and gastroduodenal artery (GDA) were abnormal. The CHA emerged from the superior mesenteric artery (SMA). Computer tomography angiography (CTA) was performed postoperatively; surprisingly, the left gastric artery (LGA) and splenic artery (SA) arising from the anterior wall of the abdominal aorta replaced the normal structure of the celiac trunk, and an accessory left hepatic artery (LHA) emerged from the LGA.Diagnoses:The patient was diagnosed with cholangiocarcinoma and accompanying extremely rare variation of celiac trunk and hepatic artery.Interventions and outcomes:The patient underwent PD and had an uneventful postoperative evolution. There was no recurrence of the tumor and with normal liver function during the 10-month follow-up.Interventions:The patient underwent PD and had an uneventful postoperative evolution.Outcomes:There was no recurrence of the tumor and with normal liver function during the 10-month follow-up.Lessons:Surgeons must keep in mind that arterial variation may be present in the vascular structures intraoperatively, even if it was not revealed in preoperative imaging. The preoperative identification of arterial variation and its relationship with the tumor is necessary to avoid intraoperative vascular injury and complications after surgery.

Adult-to-adult living donor liver transplantation preoperative survey using MDCT, a single medical center experience in Taiwan

This study evaluated multi-detector computed tomography (MDCT) scans performed on potential living donors for adult-to-adult liver transplantation (LDLT), with the aim of identifying significant findings that could be used to exclude potential transplantation donors. We retrospectively reviewed the medical records of 151 consecutive potential adult donors for LDLT from May 2007 to January 2015. Liver parenchyma steatosis, focal hepatic mass or intraabdominal malignancy, vascular variations, and donor liver volume were evaluated via MDCT. Grounds for excluding potential donors were also recorded and analyzed. Of the 151 potential donors, nine (6.0%) had moderate to severe fatty liver, 37 (24.5%) had hepatic arterial variants, 22 (14.6%) had significant portal venous variants, and more than half were found to have right accessory inferior hepatic vein. No intraabdominal malignancies were found. Eighty-eight potential donors were rejected, with the most common cause being insufficient recipient volume or remnant donor volume (47.7%), moderate to severe parenchymal steatosis (10.2%), and recipient expiration prior to transplantation (8.0%). An additional 16 potential donors were excluded by the surgical team due to the complexity of their portal venous variations. The rate of exclusion by pre-transplant imaging evaluation with MDCT was 33.8%. MDCT can provide accurate quantification of donor liver volume and steatosis severity along with precise demonstration of vascular variants, which are crucial for the preoperative evaluation of LDLT. However, MDCT may be ineffective for evaluating the biliary system without hepatobiliary-excreted contrast agent and has the disadvantage of ionizing radiation.

Cadaveric Study of Anatomical Variations of Hepatic artery in Sudanese 2014

Cadaveric Study of Anatomical Variations of Hepatic artery in Sudanese 2014

Successful radical resection of pancreatic head carcinoma in a patient with replaced right hepatic artery originating from posterior inferior pancreaticoduodenal artery: a case report

Anatomical variations of hepatic arteries may be problematic in pancreaticoduodenectomy (PD). We experienced pancreatic head cancer in a patient with rare variation of hepatic artery and performed PD successfully with the resection of this artery. A 75-year-old woman showed pancreatic head tumor on CT. Preoperative CT detected rare variation of hepatic artery; posterior segmental branch of right hepatic artery (RHA-PB) originating from posterior inferior pancreaticoduodenal artery. The image also demonstrated that there was a junction between RHA-PB and anterior branch of right hepatic artery (RHA-AB). We performed PD for suspected pancreatic head cancer. We divided RHA-PB for complete resection of cancer because we preoperatively knew that there was the junction between RHA-PB and RHA-AB. She was discharged uneventfully, and there was no evidence of local recurrence throughout the whole course. Careful preoperative assessment of hepatic blood supply is the key to perform successful PD even in this troublesome situation.

Early Hepatic Artery Thrombosis After Liver Transplantation: What is the Impact of the Arterial Reconstruction Type?

Hepatic artery thrombosis (HAT) is the most severe vascular complication occurring after liver transplantation, with an incidence ranging from 2 to 9% in adults. Although the ideal arterial reconstruction is often described as a short and non-redundant anastomosis fashioned between the recipient and donor hepatic arteries, there is no strong evidence about this ideal reconstruction in the literature. The aim of this study was to assess the impact of the type of arterial reconstruction on early HAT after primary liver transplantation. We retrospectively reviewed a contemporary MELD era cohort of 282 patients who underwent deceased donor primary liver transplantation from 2007 to 2012. Graft artery was classified as "short" when the section was located at the proper/common hepatic artery or "long" when the celiac trunk was used for anastomosis. Recipient arterial sites for arterial anastomosis were classified in three sites: (1) "distal" (proper hepatic artery or common hepatic artery/gastro-duodenal bifurcation), (2) "intermediate" (common hepatic artery) and (3) "proximal" (celiac trunk-splenic artery-aorta). We used univariate and multivariate analyses to assess the impact of different types of arterial reconstruction on early HAT. Of 282 primary liver transplantations, 17 patients (6%) developed early HAT. Patients with and without early HAT had comparable demographic and operative data. The main anastomotic combination was short graft artery on the recipient-common hepatic artery (n=111, 39%). A long graft artery was used in 91 patients (32%) and was associated with hepatic artery variations (56%; n=51; p=0.001). Arterial reconstructions using a long graft artery (p=0.003), a recipient proximal site as celiac trunk-splenic artery-aorta (p=0.02) and the combination of a long graft artery on the recipient distal hepatic artery (p=0.02) were significantly associated with early HAT. The early HAT rate in patients with a long graft artery was not significantly different between patients with or without donor arterial variation (respectively, 12% (n=6/51) vs. 12% (n=5/40); p=1). In multivariate analysis, the use of a long graft artery, whatever the recipient anastomosis site, was an independent risk factor of early HAT (OR 3.2; 95% CI 1.2-9; p=0.02). The type of arterial reconstruction used for arterial anastomosis during primary liver transplantation has an impact on the occurrence of early HAT. The use of a long graft artery is an independent risk factor of early HAT. Thereby, we recommend the use of a short graft artery with a direct path when feasible to reduce the occurrence of early HAT after primary liver transplantation.

ANATOMIC VARIATIONS OF HEPATIC ARTERY: A STUDY IN 479 LIVER TRANSPLANTATIONS.

ABSTRACTBackground:The incidence of anatomic variations of hepatic artery ranges from 20-50% in different series. Variations are especially important in the context of liver orthotopic transplantation, since, besides being an ideal opportunity for surgical anatomical study, their precise identification is crucial to the success of the procedure. Aim:To identify the anatomical variations in the hepatic arterial system in hepatic transplantation. Methods: 479 medical records of transplanted adult patients in the 13-year period were retrospectively analyzed, and collected data on hepatic arterial anatomy of the deceased donor. Results:It was identified normal hepatic arterial anatomy in 416 donors (86.84%). The other 63 patients (13.15%) showed some variation. According to the Michels classification, the most frequently observed abnormalities were: right hepatic artery branch of superior mesenteric artery (Type III, n=27, 5.63%); left hepatic artery branch of the left gastric artery (Type II, n=13, 2.71%); right hepatic artery arising from the superior mesenteric artery associated with the left hepatic artery arising from the left gastric artery (Type IV, n=4, 0.83%). Similarly, in relation to Hiatt classification, the most prevalent changes were: right hepatic accessory artery or substitute of the superior mesenteric artery (Type III, n=28, 6.05%)), followed by liver ancillary left artery or replacement of gastric artery left (Type II, n=16, 3.34. Fourteen donors (2.92%) showed no anatomical abnormalities defined in classifications, the highest frequency being hepatomesenteric trunk identified in five (01.04%). Conclusion:Detailed knowledge of the variations of hepatic arterial anatomy is of utmost importance to surgeons who perform approaches in this area, particularly in liver transplantation, since their identification and proper management are critical to the success of the procedure.

Clinical significance of circumportal pancreas, a rare congenital anomaly, in pancreatectomy

BackgroundCircumportal pancreas is a rare congenital pancreatic anomaly. The aim of this study was to clarify the clinical characteristics of patients with circumportal pancreases undergoing pancreatectomy. MethodsThe medical records of 508 patients who underwent pancreatectomy were retrospectively reviewed. The prevalence of circumportal pancreas and related anatomical variations were assessed. Surgical procedures and postoperative outcomes were compared in patients with and without circumportal pancreas. ResultsCircumportal pancreas was observed in 9 of the 508 patients (1.7%). In all nine patients, the portal vein was completely encircled by the pancreatic parenchyma above the level of the splenoportal junction, and the main pancreatic duct ran dorsal to the portal vein. The rate of variant hepatic artery did not differ significantly in patients with and without circumportal pancreas. Pancreatic fistula developed more frequently in patients with than without circumportal pancreas (44% vs. 14%, p = 0.03), but other clinical parameters did not differ significantly in these two groups. ConclusionsDespite being rare, circumportal pancreas may increase the risk of postoperative pancreatic fistula in patients undergoing pancreatectomy. However, a prospective, large-cohort study is necessary to determine the real incidence of relevant anatomical variations and the definitive clinical significance of this rare anomaly.

Celiac trunk and hepatic artery variants: A retrospective preliminary MSCT report among Egyptian patients

ObjectiveTo evaluate the feasibility of MSCT angiography of the celiac trunk and hepatic artery variants with a non-tailored protocol among Egyptian patients. Patients and methods1285 Egyptian patients were retrospectively analyzed in our Radiology Department – Ain Shams University came for triphasic CT or CT aortic angiography. The celiac trunk origin and its main branches mainly the common hepatic artery were identified. The incidence of different celiac and hepatic artery anomalies was calculated depending on Uflacker’s and Michel’s classifications. ResultsAbout 90.5% of the patients showed normal trifurcation pattern of the celiac trunk (Uflacker type I) with the commonest variant was gastro-splenic trunk (Uflacker type V) with 4.3% incidence. The bifurcation pattern was representing 7.7% of cases. Regarding the hepatic artery, 74.3% of the cases showed normal origin of the hepatic arteries (Michel type I) with the commonest anomaly was Michel type III with 12.5% incidence. Some cases are discovered not previously described by either Uflacker’s or Michel’s classifications. ConclusionIn our preliminary reports, Good imaging quality of MSCT angiography has proved effectiveness in depicting different celiac trunk and hepatic artery variants. This is important pre-interventional or pre-surgical to decrease the complications and the morbidity rates.

Assessment of the parenchymal blood volume by C-arm computed tomography for radioembolization dosimetry

PurposeAim of the study was to evaluate the impact of parenchymal blood volume (PBV) C-arm CT in transarterial radioembolization (TARE) planning procedure regarding the appropriateness of segmental blood supply from selective catheter positions defined by angiographic images compared to PBV mapsto determine the influence of changed target volumes on dose calculation. Material and methodsA total of 22 consecutive patients (median age, 62 years) underwent a TARE planning procedure were included in this retrospective study. Selective angiograms and selective PBV C-arm CT (right and left liver lobe) were evaluated in a blinded fashion, regarding segmental hepatic artery variants. Volumetry of target volume and dosimetry of glass and resin microspheres were performed. ResultsClassification of segment IV and segment I to the corresponding target vascular bed supply was correct in 91.0% (20/22) and 86.4% (19/22) for angiography and C-arm CT, respectively. Except one case, all other liver segments were classified properly to the left and right hepatic arterial supply. Based on the mismatch of the angiographic and the C-arm CT approach, changes of target volume were evident in 27.3% of patients, resulting in a mean mismatch volume of 90±54ml (range, 51–198ml) and a percentage of dose differences of 14.2±11.8% and 12.6±10.6% for the right and 12.5±8.5% and 11.1±7.8% for the left liver lobe in glass and resin microspheres, respectively. ConclusionThe C-arm CT approach is superior to the angiographic determination of vascular supply of specific liver segments for dosimetry before radioembolization. Especially for unexperienced interventional radiologists or for a complex anatomy, C-arm CT improves individualized dosimetry concepts.

The "Vessel through Strait" Sign is a Signature Radiological Sign for the Diagnosis of Left Hepatic Artery Variation.

An aberrant artery (AA) can frequently be observed coursing through the fissure for the ligamentum venosum (FLV) which was termed the “vessel through strait” sign (VTSS) by us. Fundamental data including the incidence, anatomical composition and clinical significance of VTSS and the AAs composing VTSS are still lacking. We sought to give a systematic demonstration on this issue in the present study. VTSS was respectively analyzed in 2,275 patients and was observed in 357 of them. Interestingly, 319 (89.4%) out of the 357 patients exhibiting VTSS were proved to have left hepatic artery variation (LHAV) (247 with replaced left hepatic artery, 64 with accessory left hepatic artery and 8 with variant common hepatic artery). We therefore hypothesized that VTSS could be a sign that strongly associated with LHAV and could be used for its diagnosis. In the following validating analysis, VTSS gained a sensitivity of 96.3% and a specificity of 98.3% for the diagnosis of LHAV in another bicenter cohort consisted of 1,329 patients. In conclusion, VTSS is a signature radiological sign of LHAV which could be used as an easy and specific method for the diagnosis of LHAV.

Utilizing 3D CT reconstructions to identify variant hepatic artery anatomy

Introduction: Hepatic artery (HA) anatomy is highly variant and may be difficult to recognize on traditional CT axial imaging. 3D reconstructions can be used in conjunction with axial imaging to identify variants pre-operatively. Our purpose was to create a database of common variant HA anatomy which can be used to educate surgeons and surgery residents on radiographic identification of variant anatomy to aid in pre-operative planning. Method: A database of variant HA anatomy was made from patients at a single tertiary care center. Images were de-identified prior to their transformation to 3D reconstructions. Only CTA studies were used, as these provide the optimal timing of the contrast bolus to facilitate the 3D reconstruction. Images representing the most commonly described HA variants were included. Results: Eight common variant HA images were included. 3D reconstructions are presented alongside axial images with descriptions of the variants, clues to identify the variants on imaging, and their clinical relevance. The user is able to rotate the 3D images and scroll through the axial cuts side by side to gain a better understanding of the anatomy. Conclusions: Surgeons can increase their understanding of variant HA anatomy prior to embarking on foregut resections by studying representative 3D reconstructions alongside axial imaging.

Evaluation of hepatic arterial anatomy by multidetector computed tomographic angiography in living donor liver transplantation.

The aim of this study was to define the different courses and percentages of hepatic artery that were detected during preoperative evaluation of living liver donors by multidetector computed tomographic angiography (MDCTA). We evaluated 150 donors before hepatic transplantation. All of the donors were evaluated by multislice CT scan with 256 detectors. For each patient, arterial, portal and venous phase images were obtained. The hepatic arterial variations were evaluated by the same radiologist according to Michels' classification. Common hepatic arterial anatomy (type I) was observed in 95 donors (63.3%). Other arterial variations were determined in the remaining 55 donors (36.6%). The second common variation was type XI which did not match with the description of Michels' classification variation in 15 donors (10%). The remaining variations described in Michels' classification were seen at lower rates. Type VII or X variation was not seen. MDCTA is a useful method to identify the blood supply of the liver before the liver transplantations, and surgeons can make their plan on the basis of CT data.

Hepatic Arterial Anatomy Variations Evaluated by the Computed Tomography Angiography in the Patients with Hepatocellular Carcinoma: A Case-Control Study

Background: Hepatic arterial anatomy is of major importance in performing many surgical and endovascular procedures on the liver. Hepatic artery anatomical variations are a common finding. Aim: The aim of our study was to estimate the prevalence of various hepatic arterial variants in HCC patients and compare it with that in individuals with no abdominal abnormality. Patients and methods: Total of 78 patients was included in the study. They were categorized into following groups: 1) Patients with HCC (n=46); 2) Control group (n=32). Prevalence of variant arterial anatomy in each group and subgroup was determined and compared to the values in Control Group. Results: Compared to the control group HCC group showed higher incidence of hepatic arterial anatomy variations (54.5% vs. 31.2%). The difference was statistically significant (p<0.05). Among the patients with HCC lesions larger than 10 cm the percentage of arterial variations was 81.25% which was very statistically significantly different from that of the control group (p<0.01). This subgroup of patients also showed higher incidence of SMA type RHA p<0.05). Among the patients with single HCC lesion the percentage of arterial variations was 76.92% which was very statistically significantly different from that of the control group (p<0.01). Among the patients with two HCC lesions the percentage of arterial variations was 62.5% which was not statistically significantly different from that of the control group. Groups of patients with HCC lesions less than 10 cm as well as the group with multiple HCC lesions did not show statistically significant difference of the hepatic arterial anatomy variation incidence compared to the control group either. Our study implies that there may be a difference in the incidence of hepatic arterial anatomical variations between HCC patients and healthy individuals. This issue is worth of conducting further research on large series.