Antegrade Transvenous Obliteration Research Articles

Transjugular antegrade transvenous obliteration, with and without portal decompression, for management of rectal variceal hemorrhage

PurposeTo report antegrade transvenous obliteration, with or without concurrent portosystemic shunt creation, for the treatment of hemorrhagic rectal varices.Materials and methodsEight patients, including five (62.5%) females and three (37.5%) males, with mean age of 55.8 ± 13.8 years (range: 30–70 years), underwent transjugular-approach antegrade transvenous obliteration of rectal varices, with or without portosystemic shunt creation. Demographic data, procedural details, technical success of variceal obliteration, clinical success, adverse events, and follow-up outcomes were retrospectively recorded. Clinical success was defined as resolution of rectal hemorrhage.ResultsPortal venous access was achieved via a transjugular intrahepatic approach in all patients. The inferior mesenteric vein was selected, and foamy sclerosant (1:2:3 mixture by volume of ethiodized oil: sodium tetradecyl sulfate: air) was injected into the rectal varices with antegrade balloon occlusion in seven (87.5%) and without balloon occlusion in one (12.5%). Five of eight (62.5%) patients underwent concomitant transjugular intrahepatic portosystemic shunt (TIPS) creation (mean diameter 8.4 ± 0.9-mm) immediately following transvenous obliteration. Technical success of variceal obliteration was achieved in all patients. There were no immediate post-procedural adverse events. There were no reported occurrences of rectal ischemia, perforation, or stricture following obliteration. Two (40%) of the patients who underwent concomitant TIPS creation developed hepatic encephalopathy within 30 days of the procedure, which was medically managed. Clinical resolution of hemorrhage was achieved in all patients with no recurrent rectal variceal hemorrhage during mean follow-up of 666 ± 396 days (range: 14 − 1,224 days).ConclusionTransvenous obliteration, with or without concurrent TIPS creation, is feasible with promising results for the management of rectal variceal hemorrhage.

Interventional Management of Variceal Bleeding: Techniques and Emerging Concepts

AbstractDespite technical advancements and disease understanding, variceal bleeding remains the leading cause of mortality in patients with cirrhosis. Endoscopic therapies are the main cornerstone of therapy in variceal bleeding. Interventional radiology (IR) plays a significant role in managing variceal bleeding, especially in cases where endoscopic therapies are not feasible or failed. Cross-sectional imaging is often critical to identify relevant anatomy before IR therapies. Transjugular intrahepatic portosystemic shunt (TIPS) is indicated as salvage therapy in patients with refractory variceal bleeding. Retrograde transvenous variceal embolization (RTO) procedures provide superior bleeding control in patients with gastric and ectopic varices, however, without increasing the risk of hepatic encephalopathy and liver function deterioration. Antegrade transvenous obliteration is a viable alternative when RTO is not feasible. Left-sided portal hypertension is a distinct entity resulting from splenic vein stenosis or occlusion, and variceal bleeding in left-sided portal hypertension does not respond to TIPS, requiring variceal embolization, partial splenic embolization, or splenic vein recanalization. Occasionally, endovascular splenorenal or mesorenal shunt and splenic vein occlusion with distal splenorenal diversion are performed to control variceal bleeding. This article entails the basic concepts and procedural aspects of various interventional radiological procedures performed in patients with variceal bleeding.

Interventional Radiology for Bleeding Ectopic Varices: Individualized Approach Based on Vascular Anatomy.

Ectopic varices are rare but potentially life-threatening conditions usually resulting from a combination of global portal hypertension and local occlusive components. As imaging, innovative devices, and interventional radiologic techniques evolve and are more widely adopted, interventional radiology is becoming essential in the management of ectopic varices. The interventional radiologist starts by diagnosing the underlying causes of portal hypertension and evaluating the afferent and efferent veins of ectopic varices with CT. If decompensated portal hypertension is causing ectopic varices, placement of a transjugular intrahepatic portosystemic shunt is considered the first-line treatment, although this treatment alone may not be effective in managing ectopic variceal bleeding because it may not sufficiently resolve focal mesenteric venous obstruction causing ectopic varices. Therefore, additional variceal embolization should be considered after placement of a transjugular intrahepatic portosystemic shunt. Retrograde transvenous obliteration can serve as a definitive treatment when the efferent vein connected to the systemic vein is accessible. Antegrade transvenous obliteration is a vital component of interventional radiologic management of ectopic varices because ectopic varices often exhibit complex anatomy and commonly lack catheterizable portosystemic shunts. Superficial veins of the portal venous system such as recanalized umbilical veins may provide safe access for antegrade transvenous obliteration. Given the absence of consensus and guidelines, a multidisciplinary team approach is essential for the individualized management of ectopic varices. Interventional radiologists must be knowledgeable about the anatomy and hemodynamic characteristics of ectopic varices based on CT images and be prepared to consider appropriate options for each specific situation. ©RSNA, 2024 Supplemental material is available for this article.

Percutaneous Antegrade Transvenous Variceal Obliteration for Portal Vesiculopathy-Related Gross Hematuria

AbstractVesical varices secondary to portal hypertension are extremely rare cause of hematuria with only a few cases reported to date. We report a case of portal vesiculopathy in a patient of hepatitis B virus-related chronic liver disease presenting with gross hematuria, successfully treated with percutaneous antegrade transvenous obliteration using n-butyl cyanoacrylate glue and Amplatzer vascular plug.

Transvenous obliteration of gastric varices

Gastric varices on the background of portal hypertension occur less frequently than esophageal varices but they develop at lower portal pressure and are associated with more massive bleedings and higher mortality rate. Balloon-occluded retrograde transvenous obliteration (BRTO) has been well documented as an effective therapy for gastric varices caused by portal hypertension. However, BRTO requires long-term, higher-level post-procedural monitoring and can have complications related to balloon rupture and adverse effects of sclerosing agents. Several modified BRTO techniques have been developed, including vascular plug-assisted retrograde transvenous obliteration, coil-assisted retrograde transvenous obliteration, and balloon-occluded antegrade transvenous obliteration. This article provides an overview of BRTO various and modified BRTO techniques.

Atypical Presentation of Isolated Gastric Variceal Bleeding Requiring Multidisciplinary Management

Variceal bleeding is the most lethal manifestation of portal hypertension, most commonly due to esophageal varices in the setting of liver cirrhosis. Isolated gastric varices (IGV) are a rare cause of upper gastrointestinal bleeding, often of pancreatic origin. In this case we present a complex patient with a history of remote splenic injury leading to portopulmonary hypertension and the development of refractory bleeding due to IGV. We discuss the extensive multidisciplinary approach taken to provide comprehensive care and to control bleeding, which included endoscopic (sclerotherapy), radiologic (balloon-occluded antegrade transvenous obliteration [BATO] and splenic artery embolization) and surgical interventions (splenectomy).

S2273 Balloon-Occluded Antegrade Transvenous Obliteration ( BATO) as Salvage Therapy for Gastric Variceal Bleed

S2273 Balloon-Occluded Antegrade Transvenous Obliteration ( BATO) as Salvage Therapy for Gastric Variceal Bleed

The use of balloon-assisted antegrade transvenous obliteration should be cautious

The use of balloon-assisted antegrade transvenous obliteration should be cautious

S2192 Over-the-Scope Clip as Rescue Treatment for Bleeding Gastric Varices

INTRODUCTION: We present a case of gastrointestinal bleeding in a patient with pancreatitis-induced splenic vein thrombus. This case highlights an important etiology of gastric varices, a known complication of treating them, as well as a method for treating refractory bleeding. CASE DESCRIPTION/METHODS: An 18-year-old male with ALL s/p post allogeneic HSCT, chronic pancreatitis, bowel perforations s/p ileostomy presented with gastrointestinal bleeding. The patient had hospitalizations at other institutions with intermittent melena and occasional hematemesis. After multiple upper endoscopies that did not identify the etiology of bleeding, he was referred to our hospital for double balloon enteroscopy. His hemoglobin was down to 5.9 g/dL (baseline 9-10 g/dL). EGD was performed with plan for double balloon enteroscopy, but a large blood clot was seen in the stomach. A nodular area in the fundus was actively bleeding. Given concern for an isolated gastric varix (IGV-1), EUS-guidance was used to inject coils and N-butyl-2-cyanoacrylate into the gastric varices with adequate hemostasis. Follow-up imaging noted extensive portal and splenic vein embolization from the glue. The patient developed recurrent melena and an emergent TIPS placement with coronary vein coil embolization was performed. Recurrent gastrointestinal bleeding was again noted. CT angiography was obtained and revealed a splenic vein thrombus. The patient underwent a balloon-occluded antegrade transvenous obliteration with glue/coil embolization of a smaller vessel feeding the gastric varix. However, GI bleeding was again noted. A repeat endoscopy was subsequently performed with placement of three over the scope clips (OTSC) on the varix for successful hemostasis. DISCUSSION: Gastric varices are often associated with cirrhosis but can occur in patients with non-cirrhotic portal hypertension (i.e., splenic vein thrombosis). Cyanoacrylate glue injection is recommended for acute bleeding from IGV. A known complication of glue injection is the risk of embolization (approximately 1–2%). Endoscopic ultrasound guided coil deployment can act as a scaffold at the time of glue injection to reduce this risk. OTSC have been used successfully in esophageal variceal bleeding. We report the first successful use of OTSC for gastric varices which should be considered as salvage therapy.Figure 1.: Gastric varices with hemostasis after endoscopic ultrasound-guided coil and glue injection.Figure 2.: Portal vein embolization after endoscopic ultrasound-guided coil and N-butyl-2-cyanoacrylate injection.Figure 3.: Recurrent gastric variceal bleeding with hemostasis after successful over the scope clip deployment.

S0986 Outcomes of Balloon-Occluded Retrograde Transvenous Obliteration and Its Variants for Treatment of Gastric Varices at a High-Volume North American Center

INTRODUCTION: BRTO is a common alternative to TIPS or endoscopy for controlling gastric variceal bleeding. Its universal adoption has however been limited due to lack of expertise and fears regarding complications. This study evaluates outcomes of BRTO and its variants, Coil-Assisted Retrograde Transvenous Obliteration (CARTO) and Balloon-Occluded Antegrade Transvenous Obliteration (BATO) at a single center. METHODS: A retrospective review of patients undergoing BRTO or a variant procedure from 6/2013-6/2019 at our institution was performed. Data was collected on demographics, indication, MELD score at time of, 1 month and 1-year post procedure, technical success, complications, rebleed events, mortality, worsening of ascites, encephalopathy, esophageal varices, systemic thrombosis and hepatocellular carcinoma (HCC) incidence up to 1 year post procedure. Statistics were calculated using univariate two-group t-tests or Wilcoxon rank-sum test for continuous variables and non-parametric tests. RESULTS: A total of 65 patients, 11 (16.9%) BATO, 6 (9.2%) BRTO, 45 (69.2%) BRTO/CARTO and 3 (4.6%) BATO/BRTO were evaluated. A 93.8% technical success rate was noted with 2 failures in BATO and 2 in BRTO due to intraprocedural vessel rupture and anatomic issues. High risk gastric varices or bleeding was the most common indication occurring in 53 (81.5%) cases. 1 BATO/BRTO case was complicated by post-procedural sepsis. There were a total of 3 (5%) rebleeding events. 1 BATO patient died from rebleeding on day of procedure and 1 BRTO/CARTO patient died the following day. 4 patients developed new esophageal varices of which 2 bled within one year that was controllable endoscopically. 4 (6.5%) patients developed worsening ascites, 2 (3%) had new or worsened encephalopathy and 9 (13%) developed systemic thrombosis. No patients developed HCC post-procedurally. Mean change in MELD was −0.88 1 month post-procedure with no significant difference in MELD scores from procedure time to 1 month (P = 0.769) or 1 month to 1 year (P = 0.132) when comparing BRTO to its variants. CONCLUSION: Our data demonstrates that BRTO and its variants are effective alternatives to TIPS for treatment of gastric varices without significant adverse effect on MELD scores and minimal to no worsening of portal hypertension related complications. Physicians however must remain vigilant for risk of systemic thromboses and esophageal variceal formation. Of note, previous fears of worsening ascites or increased risk for HCC are not supported by our study.

The combination of balloon-assisted antegrade transvenous obliteration and transjugular intrahepatic portosystemic shunt for the management of cardiofundal varices hemorrhage.

Objectives:In this study, we propose a modified balloon-occluded retrograde transvenous obliteration (BRTO) strategy – balloon-assisted antegrade transvenous obliteration (BAATO), and explore the feasibility, efficacy and safety of BAATO combined with transjugular intrahepatic portosystemic shunt (TIPS) in the treatment of cardiofundal varices (GOV2 or IGV1) hemorrhage.Materials and methods:In this retrospective cohort study, 15 patients with cardiofundal varices hemorrhage who received BAATO combined with TIPS procedures, from August 2017 to September 2019 in our center, were enrolled. They consisted of seven patients with GOV2 and eight patients with IGV1. The clinical efficacy and safety of BAATO + TIPS procedures were assessed by comparing the clinical symptoms, laboratory and imaging examinations before and after treatment.Results:The technical success rate of BAATO + TIPS procedure was 100%. After the procedure, clinical symptoms were improved and complete regression of gastric varices (GVs) was observed in all patients, besides, the control efficiency of ascites and PVT which were 77.8 and 87.5%, respectively. No patient died or had a rebleeding during the follow up, but grade II hepatic encephalopathy (HE) occurred in two patients (13.3%) and shunt dysfunction was discovered in one patient (6.7%).Conclusion:For the treatment of GVs, the new technique BAATO is feasible, safe and effective, and it may be a more convenient and economical method than conventional BRTO. In addition, the combination of BAATO and TIPS may play a positive role in achieving hemostasis and improving the complications of portal hypertension such as ascites and PVT.

Gastric variceal hemorrhage treated with percutaneous transhepatic embolization with balloon-occluded antegrade transvenous obliteration

Gastric variceal hemorrhage treated with percutaneous transhepatic embolization with balloon-occluded antegrade transvenous obliteration

2428 Direct Intrahepatic Portocaval Shunt (DIPS) as a Therapeutic Option in Acute Variceal Hemorrhage

INTRODUCTION: Direct Intrahepatic Portocaval Shunt (DIPS) is a modified transjugular intrahepatic portosystemic shunt (TIPS) procedure, in which a stent is placed across the inferior vena cava directly into the portal vein under intravascular ultrasound guidance. DIPS is a recognized salvage therapy for acute variceal hemorrhage, but not commonly utilized. Indications for DIPS include patients with hepatic venous anomalies not amenable to TIPS, distorted post-surgical vascular anatomy of the liver, intrahepatic portal venous thrombus, or a prior failed TIPS. CASE DESCRIPTION/METHODS: A 73-year-old male with a history of cirrhosis from alcohol and hepatitis C virus and right lobe hepatocellular carcinoma status-post laparoscopic microwave ablation presented with hematemesis. An EGD revealed a gastric varix (Figure 1), which was deemed too large for treatment with cyanoacrylate glue deposition. A TIPS was attempted but failed due to hepatic venous anomalies. Subsequently, the varix was treated with a balloon-occluded antegrade transvenous obliteration (BATO) and a balloon occluded retrograde transvenous obliteration (BRTO). Figure 2 demonstrates the BATO, which coiled the afferent vessels to the varix (red arrow), and the BRTO, which coiled the efferent gastro-renal shunt of the varix (blue arrow). Two days after the BATO/BRTO, the patient had recurrent melena and anemia. An EGD doppler-guided glue deposition into the gastric varix was attempted but failed. A TIPS was not a viable option as an ultrasonography revealed a new portal vein thrombus extending into the anterior and posterior branches of the right portal vein. Thus, a DIPS was performed. Under intravascular ultrasound guidance, a catheter (red arrows) was advanced from the IVC directly to the left portal vein creating a shunt with stent placement as seen in Figure 3. The pre-procedure portosystemic gradient was 18 mm Hg, and post-procedure portosystemic gradient was 5 mm Hg with a reduction in the gastric varix. The patient is well three-months post-procedure without recurrent melena or anemia. DISCUSSION: This case demonstrates the successful utilization of DIPS in a patient where TIPS was not feasible due to hepatic venous anomalies and a portal vein thrombus. Furthermore, DIPS was successful in the treatment of a variceal hemorrhage when other therapies such as cyanoacrylate glue deposition, BATO, and BRTO failed. Therefore, DIPS should be utilized in challenging cases of variceal hemorrhage when performed by an experienced interventional radiologist.

Modified Balloon-Occluded Retrograde Transvenous Obliteration (BRTO) Techniques for the Treatment of Gastric Varices: Vascular Plug-Assisted Retrograde Transvenous Obliteration (PARTO)/Coil-Assisted Retrograde Transvenous Obliteration (CARTO)/Balloon-Occluded Antegrade Transvenous Obliteration (BATO).

Gastric varices in the setting of portal hypertension occur less frequently than esophageal varices but occur at lower portal pressures and are associated with more massive bleeding events and higher mortality rate. Balloon-occluded retrograde transvenous obliteration (BRTO) of gastric varices has been well documented as an effective therapy for portal hypertensive gastric varices. However, BRTO requires lengthy, higher-level post-procedural monitoring and can have complications related to balloon rupture and adverse effects of sclerosing agents. Several modified BRTO techniques have been developed including vascular plug-assisted retrograde transvenous obliteration, coil-assisted retrograde transvenous obliteration, and balloon-occluded antegrade transvenous obliteration. This article provides an overview of various modified BRTO techniques.

Successful Treatment of Bleeding Rectal Varices with Balloon Occluded Antegrade Transvenous Obliteration: 2016 ACG Presidential Poster Award.

Successful Treatment of Bleeding Rectal Varices with Balloon Occluded Antegrade Transvenous Obliteration: 2016 ACG Presidential Poster Award.

The Conventional Balloon-Occluded Retrograde Transvenous Obliteration Procedure: Indications, Contraindications, and Technical Applications

Transvenous obliteration of gastric varices can be performed from the systemic venous side (draining veins or shunts) or from the portal venous side (portal afferent feeders). Balloon-occluded transvenous obliteration from the systemic veins is referred to as balloon-occluded retrograde transvenous obliteration (BRTO) and balloon-occluded transvenous obliteration from the portal veins is referred to as balloon-occluded antegrade (anterograde) transvenous obliteration (BATO). BRTO is the conventional balloon-occluded transvenous obliteration procedure and BATO is considered an alternative or adjunctive approach. This is because, from a technical standpoint, the least invasive choice of access or approach for balloon-occluded transvenous obliteration of gastric varices is the traditional or conventional transrenal route. The objective of BRTO or BATO or both is complete obliteration of the gastric varices with preservation of the anatomical hepatopetal flow of the splenoportal circulation. This article reviews the indications, contraindications, and technical considerations of the conventional BRTO procedure. The indications of concomitant portal venous modulators such as splenic embolization or the creation of a transjugular intrahepatic portosystemic shunt or both are also discussed.

Stomal Varices: Management With Decompression TIPS and Transvenous Obliteration or Sclerosis

Stomal or parastomal varices are extraperitoneal ectopic mesenteric varices. Parastomal varices are not common but can be a source of considerable bleeding. They usually occur in the setting of portal hypertension, although, in theory, they can occur because of vascular thrombosis of the mesentery. An obstructive element (not necessarily venous thrombosis, but a constrictive effect) most likely exists and thus localizes the bleeding to the stomal mesenteric varices. This obstruction can be due to postsurgical changes associated with the stoma creation itself. Bleeding is the main presentation of stomal varices. Bleeding can be life threatening; however, most of it can be controlled by manual compression by patients who are consciously aware. Anecdotally, there are 2 pathologic bleeding presentations. Certain stomas are diffusely congested and ooze blood diffusely, and others bleed focally from a particular site (from a particular mesenteric varix). The focal bleeders are the ones that respond favorably to manual compression by the patient. The stomas that are diffusely congested or engorged with diffuse venous oozing do better with transjugular intrahepatic portosystemic shunt (TIPS) decompression. Bleeding from focal varices in the stoma (with the rest of the stomal mucosa looking normal and not engorged) can be treated with TIPS (if the portal or mesenteric vein or both are patent) or with transvenous obliteration utilizing 1% sodium tetradecyl sulfate (not 3% sodium tetradecyl sulfate). Balloon-occluded retrograde transvenous obliteration, percutaneous transhepatic obliteration, trans-TIPS balloon-occluded antegrade transvenous obliteration can all be adequate approaches to transvenous obliteration. However, the least invasive (in the authors' opinion) and simplest is the direct mesenteric venous stick (balloon-occluded antegrade transvenous obliteration-type) approach with ultrasound-guided compression of the systemic outflow vein.

Vascular Anatomy and the Morphologic and Hemodynamic Classifications of Gastric Varices and Spontaneous Portosystemic Shunts Relevant to the BRTO Procedure

The pathologic anatomy and hemodynamics of the left-sided portal circulation that is associated with gastric varices (GVs) are complex and highly variable. Understanding the pathologic anatomy and hemodynamics associated with GVs is important for clinical management decisions and for the technical descriptive details of the balloon-occluded retrograde transvenous obliteration (BRTO) and balloon-occluded antegrade transvenous obliteration procedures. A reflection of the considerable variability in anatomy, pathology, and hemodynamics is the numerous descriptive and categorical classifications that have been described in the past 2 decades. This article reviews the detailed descriptive gross anatomy, radiographic anatomy, and portosystemic venous hemodynamics that are associated with GVs and that can be encountered during the BRTO or balloon-occluded antegrade transvenous obliteration procedure(s) or both. Definitions are also set to clarify this detailed anatomy that received limited description in the prior literature. Moreover, all the classifications that have been described (to the best of the author's knowledge) that are relevant to the BRTO procedure are detailed in the article.

Inventory Used for Balloon-Occluded Retrograde (BRTO) and Antegrade (BATO) Transvenous Obliteration: Sclerosants and Balloon Occlusion Devices

The inventory used for the balloon-occluded retrograde transvenous obliteration (BRTO) and balloon-occluded antegrade transvenous obliteration procedures includes coaxial introducer sheath, catheters, balloon occlusion catheters, possibly microcatheters, possibly coils and preeminent vascular occlusion devices, and sclerosant mixtures. The inventory can be collectively categorized into "hardware" (sheaths, catheters, balloon occlusion devices, and alloy embolic agents) and sclerosant mixtures (contrast and sclerosing agents). The hardware inventory used in Japan is different from that used in the United States. Moreover, the inventory used in Japan is commonly specifically (purpose-built) designed for the BRTO procedure. Conversely, the hardware inventory used in the United States is a "generic" (multipurpose), which operators use for multiple other anatomical and clinical settings. Using different inventories that are not purposefully designed together requires multiple trials and errors to reach size and length compatibility. From a sclerosant standpoint, there is an ongoing paradigm shift toward foam-state sclerosant mixture in Japan and the United States (as of 2006). This article discusses the inventory used for BRTO and balloon-occluded antegrade transvenous obliteration in Japan and the United States and focuses on the inventory (including compatibility of inventory) that has worked and has become popularly used in the United States. The article also discusses the sclerosant mixture components, types and states (foam, froth, or liquid).

Balloon-Occluded Antegrade Transvenous Obliteration With or Without Balloon-Occluded Retrograde Transvenous Obliteration for the Management of Gastric Varices: Concept and Technical Applications

Alternative routes for transvenous obliteration are sometimes resorted in the management of gastric varices. These alternative routes can be classified into A, portal venous access routes and B, systemic venous access routes. The portal venous approach to transvenous obliteration is called balloon-occluded antegrade transvenous obliteration (BATO) and is a collective definition, including 1-percutaneous transhepatic obliteration (PTO), 2-through an existing transjugular intrahepatic portosystemic shunt [(Trans-TIPS), and 3-trans-iliocolic vein obliteration (TIO)]. PTO is usually out of necessity; however, trans-TIPS approach is usually used out of serendipity (because the low-risk access route is there). The TIPS for the trans-TIPS BATO is not formed for mere access, but is done to create a TIPS or is done when there is a preexisting TIPS. The trans-TIPS approach can be resorted to in the United States in up to 19% of balloon-occluded retrograde transvenous obliteration (BRTO) cases. PTO is resorted to, out of necessity, in the United States and Japan in 10% of BRTO cases (2%-19% of BRTO cases) and can increase the technical and obliterative success rate of the transvenous obliteration procedure from 84%-98% to 98%-100%. The advantage of BATO as an adjunct to BRTO (combining a BRTO and BATO approach to obliterate the gastric varices) is not only limited to increasing the technical success rate of the obliterative procedure. BATO reduces the risk of overspill of the sclerosant from the gastric variceal system into the portal vein. Moreover, if the BATO is performed from a trans-TIPS approach, any overspill of the sclerosant mixture will partly (if not mostly) go through the patent TIPS to the systemic circulation (lung) rather than the intrahepatic portal vein branches (prevent portal vein embolization). This article discusses the clinical and technical applications, technical considerations, and the outcomes of BATO.