IR management of portal hypertension complications

INTRODUCTION

Complications resulting from clinically significant portal hypertension, such as ascites, acute variceal bleeding (AVB), and HE cause significant morbidity and mortality:¹ Interventional radiology plays a significant role in the diagnosis and treatment of these complications.

HVPG measurement

The BAVENO VII guidelines indicate the measurement of the HVPG as the gold standard for the diagnosis of clinically significant portal hypertension.² There are many technical nuances that can affect the HVPG reading and prognosis.³ For example, the free hepatic vein pressure or IVC pressure should be used as the systemic pressure component of the reading instead of the right atrial pressure.¹ A balloon occlusion catheter should be used to measure wedged hepatic venous pressures instead of end-hole catheter (because insufficient wedging leads to artificially low wedged hepatic venous pressures),⁴ and ree hepatic vein pressure should be measured within 2 cm of the IVC confluence where the hepatic vein is largest (because damping of the waveform due to presence of a large catheter in a small vein results in artificially high ree hepatic vein pressure).⁵ Angiography should be routinely performed to exclude venovenous and venoportal shunts, which can significantly alter the HVPG readings—if shunts are present, a different vein should be used, or direct portal pressure measurements performed.⁵

TIPS

TIPS procedure

TIPS was first described by Josef Rösch in 1969.⁶ Since then, the technique has been refined and is now considered the standard of care for secondary prevention of AVB (ie, failed medical and endoscopic therapy) with a reported technical success rate of over 95%.⁷ Briefly, a directional metallic cannula with a puncture needle is advanced into the hepatic vein by means of jugular access. Under fluoroscopy, the portal vein is punctured, traversing the parenchyma between the hepatic and portal veins. The tract is dilated and lined with a stent to maintain its patency. The initially used bare metal stents were fraught with early occlusions and have been largely replaced by hybrid self-expanding metallic stent grafts, which combine covered and uncovered portions.⁸ The original 8 or 10 mm Viatorr TIPS stent graft (Gore, Flagstaff, Arizona) has recently been replaced by the variable (8–10 mm) diameter Viatorr CX graft,⁹ which allows the procedurist to adjust the diameter to 8, 9, or 10 mm depending on the desired pressure gradient. The advancing liver therapeutic approaches consortium provides multidisciplinary evidence-based recommendations for TIPS.¹

Ultrasound-guided TIPS creation

The transhepatic portal vein puncture is considered the most difficult part of the TIPS procedure because the traditional method of puncture relies on anatomical landmarks and 2-dimensional imaging of the portal vein on fluoroscopy acquired through a wedged transhepatic portogram. This may require multiple needle passes, increasing the risk of hemorrhage due to extrahepatic portal vein puncture.¹⁰ The use of intravascular or transabdominal ultrasound has significantly improved this step, as described in several articles.^7,11 Transabdominal ultrasound is the preferred guidance used in our institution as it avoids the high cost of intravascular ultrasound, and portal punctures can be successfully achieved with 1 or 2 needle passes.

Preemptive or “early” TIPS

Preemptive TIPS (pTIPS) is defined as a TIPS procedure within 72 hours from admission for AVB.^12,13 TIPS management of AVB has seen a significant shift in recent years from late rescue therapy to pTIPS, especially in high-risk patients.¹⁴ The BAVENO VI consensus statement¹⁵ first adopted the use of pTIPS in patients with AVB who are at high risk of treatment failure, and much discussion in the literature has focused on the definition of this “high-risk group.” Child-Pugh C (score 10–13) patients show clear-cut benefits from pTIPS with over 20% improved mortality without increased HE.¹⁶ Note that the highest risk category of Child-Pugh C patients (score 14) is excluded for medical futility.^14,16

The benefit in Child-Pugh B (score 7–9) patients are more varied, and a recent large meta-analysis¹⁶ has provided further stratification of this heterogenous population. The subgroup of Child-Pugh B patients with scores of 8–9 and with active bleeding showed clear mortality benefit with pTIPS compared with drug + endoscopic therapy. The Child-Pugh-B7 with active bleeding score subgroup did not see a survival benefit with pTIPS, although there was a signal toward improved ascites control and/or reduced rebleeding.

Primary constrained TIPS

HE is a major drawback of TIPS, reportedly occurring in 5%–35% of cases and remaining refractory to medical therapy in 3%–7% of cases.^17,18 Prediction of portosystemic gradient post-shunt creation is not very reliable.¹⁹ There can be significant differences in gradient measured immediately after shunt creation versus during a subsequent procedure.¹⁸ In several instances, patients require shunt reduction due to refractory encephalopathy to 6–7 mm diameters.²⁰

Due to this, several authors^19,21,22 have proposed the primary constriction of TIPS stents so as to allow for controlled gradual dilatation of the shunt over time (“dial-a-TIPS approach”). The technique we prefer at our institution is to place a short (6 mm diameter × 19 mm length) balloon expandable stent in the hepatic parenchymal tract before insertion of the TIPS stent to form a “belt” around the covered portion of the Viatorr stent graft (Figure 1). The main indication for this is refractory ascites—an initial diameter of 6 mm is accepted regardless of gradient. The patient is monitored clinically for improvement and then brought back for subsequent TIPS dilatation procedures over several weeks or months, depending on clinical need. At each interval, the shunt is gradually expanded by 1 mm until the desired clinical effect is achieved. This approach may prevent the onset of refractory encephalopathy due to drastic changes in portosystemic gradient but remains to be validated by larger patient numbers. Others have suggested under-dilation of the TIPS at the initial creation (ie, without the constraining stent, but balloon dilatation only to 6 or 7 mm).²³ However, given that the Viatorr is a self-expanding stent graft comprising of shape-memory Nitinol (nickel-titanium alloy)²⁴ scaffold, this strategy does not reliably prevent stent expansion to its nominal diameter over time. With the new Viatorr Cx now available, we place a constraining stent only when diameters below 8 mm are required.

FIGURE 1.

(A) US-guided constrained TIPS performed in a 78 year old with refractory ascites HE. Arrows show the needle pass into the right portal vein. (B) Angiogram of portal vein(*) through the TIPS puncture set. (C) Post-TIPS venogram shows a TIPS stent with a mid-segment narrowing (arrow) due to the constrainging stent restricting the shunt diameter to 6 mm. This can be progressively dilated as needed. (D) Coronal CT shows the TIPS stent and constraining stent (arrow) more clearly.

Balloon occluded retrograde (or antegrade) transvenous obliteration, BRTO (or BATO)

Variants include plug-assisted retrograde transvenous obliteration of varices and coil-assisted retrograde transvenous obliteration of varices techniques.¹³ These local occlusive therapies require access to the variceal network, which is most commonly achieved by means of the left renal vein. BAVENO VII guidelines support balloon occluded retrograde transvenous obliteration of varices as an alternative to endoscopic treatment and TIPS for type 1 isolated gastric varices, type 2 gastroesophageal varices, and ectopic varices²; however, any accessible variceal network is potentially suitable. Occluding the variceal inflow allows for better visualization and filling of the ectatic system to obliterate as much of the structure as possible using sclerosants and/or liquid agents, for example, cyanoacrylate glue. Without the occlusion, the embolic agents tend to only block off a small portion of the variceal network allowing recanalization and risk of rebleeding. These methods have the advantage of obliterating potential sites of bleeding even in patients who may be poor candidates for TIPS (eg, poor liver function or encephalopathy), and therapeutic effects can be achieved even without excessive portal gradient reduction (Figure 2).²⁵

FIGURE 2.

(A) Coronal CT image of a 58-year-old woman with variceal bleeding shows large GOV2 and PGV. (B) Balloon occluded retrograde venogram shows GV and PGV (white arrow). Note coil embolization (arrowhead) of the left inferior phrenic vein. This allows the GV to be better visualized and prevents reflux of sclerosant into the inferior phrenic vein (C) Post-BRTO showing complete angiographic sclerosis of the GOV2. (D) Post-BRTO CT shows disappearance of the GOV2 and PGV. Abbreviations: BRTO, balloon occluded retrograde transvenous obliteration of varices; GOV2, gastro-esophageal varices.

Partial splenic arterial embolization (PSAE)

PSAE is performed by catheter-directed introduction of embolic agents into portions of the spleen resulting in controlled tissue infarction of at least 50%. PSAE is established for improving the platelet count in patients with hypersplenism. However, recent evidence suggests a role in secondary prevention of variceal hemorrhage, particularly in patients who cannot receive the TIPS procedure. Sun et al, comparing endoscopic therapy with and without PSAE in 102 patients, reported a significantly lower 2-year rebleeding rate of 22% versus 67% (p < 0.001) when PSAE was added.²⁶ Wan et al reported markedly improved 5-year patency of TIPS when combined with PSAE.²⁷ However, PSAE should be weighed against postembolic adverse events such as abdominal pain and fever.

Variceal and shunt embolization

With or without TIPS, embolization of symptomatic varices can be explored for improvement of HE, intrahepatic portal venous flow, and synthetic liver function.²⁸ Access to these varices may be obtained by means of direct puncture (eg, in parastomal varices), a transhepatic puncture for rectal varices, or in combination with a standard TIPS approach.²⁹ Arterial portal shunts may be the primary cause of portal hypertension and should be embolized where possible.³⁰ Prehepatic portal hypertension, for example, due to splenic or portal vein stenosis, requires stenting of these segments and is, therefore unlikely to improve with TIPS alone.¹³

Summary

Interventional radiology procedures are well established for the diagnosis and management of portal hypertension. Recent revisions to guidelines based on emerging evidence have placed greater emphasis on HVPG and TIPS earlier in the patient journey. Combination therapies should be explored in a multidisciplinary manner for optimal outcomes.