Hepatic vein flow reversal at duplex sonography: a sign of transjugular intrahepatic portosystemic shunt dysfunction

The Role of Spleen and Liver Elastography and Color-Doppler Ultrasound in the Assessment of Transjugular Intrahepatic Portosystemic Shunt Function

The reference standard for assessing transjugular intrahepatic portosystemic shunt (TIPS) function is venography with portosystemic pressure gradient (PPG) measurement. This procedure is invasive and expensive; thus, we assessed the feasibility, reproducibility and diagnostic accuracy of color-Doppler ultrasound (CDUS) and spleen and liver stiffness (LS) measurements for identifying TIPS dysfunction. Twenty-four patients (15 undergoing TIPS placement and nine undergoing TIPS revision) consecutively underwent CDUS examination and LS and spleen stiffness (SS) determination by transient elastography (TE) and point shear-wave elastography (pSWE). All parameters were taken before TIPS placement/revision (1-15 d before) and 24 h after, just before revision by venography. pSWE inter-observer agreement was assessed by intra-class correlation coefficient (ICC). CDUS and elastographic data were correlated (Pearson coefficient) with pressure gradients (hepatic venous pressure gradient [HVPG], PPG). Main determinants of TIPS dysfunction were investigated by linear regression. Forty-nine paired examinations were performed in total: 49 (100%) SS reliable measurements by pSWE and 38 (88%) by TE. The ICC for pSWE values was 0.90 (95% confidence interval [CI] 0.81‒0.94). SS values significantly correlated with HVPG and PPG (R = 0.51, p = 0.01). The area under the Receiver-Operating Characteristic (AUROC) curve of SS for diagnosing TIPS dysfunction was 0.86 (95% CI 0.70‒0.96) using a 25 kPa cutoff. At multivariate analysis, the flow direction of the intrahepatic portal vein branches and SS values were independently associated to TIPS dysfunction. The intrahepatic portal vein branches flow direction and SS value are two simple, highly sensitive parameters accurately excluding TIPS dysfunction. SS measurement by pSWE is feasible, reproducible and both positively and significantly correlates with HVPG and PPG values.

Understanding the spectral Doppler waveform of the hepatic veins in health and disease

Duplex Doppler sonography is a fundamental component of the complete ultrasonographic examination of the liver. Accurate interpretation of the spectral Doppler tracing from the hepatic veins is valuable, as it reflects important cardiac and hepatic physiology. Normally, there are four phases: A, S, V, and D; the S and D waves indicate flow in the antegrade direction toward the heart. In hepatic and cardiac disease, these normal waves may be absent, a finding indicative of flow in a nonphysiologic manner. In addition, transient patient factors such as phase of the respiratory cycle may influence the appearance of the spectral tracing. Familiarity with the normal and abnormal spectral Doppler waveforms from the hepatic veins and knowledge of their respective physiology and pathophysiology provide valuable insights. Systematic analysis of the direction, regularity, and phasicity of the spectral tracing and the ratio of the amplitudes of the S and D waves allows one to arrive at the correct differential diagnosis in most situations.

Parâmetros dopplervelocimétricos na avaliação da perviedade da anastomose portossistêmica intra-hepática transjugular (TIPS)

A anastomose portossistêmica intra-hepática transjugular (TIPS) é um procedimento intervencionista minimamente invasivo realizado pela introdução de prótese metálica auto-expansível no parênquima hepático, via transjugular. Tem por objetivo tratar as complicações da hipertensão portal, principalmente a hemorragia digestiva alta e a ascite refratária. A estenose é complicação freqüente, embora o procedimento seja eficaz e com baixo índice de insucesso. O diagnóstico precoce da estenose é de fundamental importância, pois interfere no tipo de tratamento a ser realizado e o reaparecimento dos sintomas pode ser grave. O ultra-som Doppler é então utilizado para o seguimento dos pacientes portadores do TIPS, e vários parâmetros são descritos na literatura para o diagnóstico de estenose, como: as velocidades mínima e máxima no interior da prótese, a velocidade na veia porta, o gradiente de velocidade entre dois pontos da prótese, e outros. Infelizmente não há consenso sobre qual parâmetro ou conjunto de parâmetros é mais eficaz no diagnóstico, porque os protocolos de avaliação variam de instituição para instituição. Os autores realizaram uma revisão dos parâmetros de estenose descritos na literatura e de outros aspectos de fundamental importância na compreensão do procedimento, como as indicações, as contra-indicações e a fisiopatologia da estenose.

Parâmetros dopplervelocimétricos na avaliação da perviedade da anastomose portossistêmica intra-hepática transjugular (TIPS): estudo prospectivo

OBJETIVO: Estudar as alterações hemodinâmicas consideradas normais após a realização da anastomose portossistêmica intra-hepática transjugular (TIPS) e a eficácia dos parâmetros sugestivos de estenose do TIPS com o ultra-som Doppler. MATERIAIS E MÉTODOS: Dezesseis pacientes foram avaliados de maneira prospectiva, no período de dezembro de 2001 a março de 2003. As avaliações foram realizadas 24-48 horas após o TIPS e a seguir em intervalos regulares de 30 dias, três meses, seis meses e um ano, com ultra-som modo B, Doppler pulsado, Doppler colorido e de amplitude em diferentes pontos da prótese relacionados ao TIPS. A angiografia foi realizada apenas para a confirmação dos resultados e terapêutica pertinente. RESULTADOS: Até o momento apenas os achados de fluxo contínuo no terço proximal da prótese e o gradiente de velocidade entre dois pontos da prótese apresentaram significância estatística para o diagnóstico de estenose do TIPS (p < 0,001), mas outros diferentes critérios também estiveram presentes, porém sem significância estatística. CONCLUSÃO: O ultra-som Doppler é uma ferramenta eficaz no diagnóstico da perviedade e das complicações secundárias à realização do TIPS, sobretudo da estenose. No entanto, é necessária casuística maior, a fim de determinar um conjunto de parâmetros que facilite o seguimento destes pacientes, reservando a angiografia apenas para o tratamento pertinente.

Doppler evaluation of transjugular intrahepatic portosystemic shunts

Transjugular intrahepatic portosystemic shunts are becoming an increasingly popular technique for the treatment of portal hypertension and its complications. However, to maintain patency, revisions are periodically required to treat stenosis and thrombosis. At many centers, Doppler sonography is used for routine follow-up. A variety of hemodynamic parameters, including main portal vein velocity, maximum stent velocity, minimum stent velocity, velocity gradient in the stent, temporal changes in stent velocity, flow direction in the intrahepatic portal and hepatic veins, and pulsatility of flow in the stent can be used. Many studies have confirmed that Doppler sonography is a valuable, noninvasive means of detecting stent malfunction, although the criteria vary somewhat at different institutions.

Ultrasonography of the liver. An update on new applications

Sonography is highly useful in evaluating the patient with severe liver disease before and after the placement of a TIPS and before and after organ transplantation. Efforts to use ultrasound imaging to evaluate for primary and metastatic lesions to the liver have been reviewed. With its Doppler and color flow capabilities, ultrasound imaging will remain an important modality for hepatic imaging, especially in the evaluation of portal vein patency and hepatic artery thrombosis.

Esophageal varices. II. TIPS (transjugular intrahepatic portosystemic shunt) and surgical therapy

The role of surgery in the prevention and treatment of variceal hemorrhage is reviewed. Types of available surgery, their physiologic basis, and literature supporting their use are discussed in the context of the natural history of variceal hemorrhage. The evolution of transjugular intrahepatic portosystemic shunt (TIPS) as a treatment modality for variceal hemorrhage is reviewed. The effects of TIPS on portal and systemic hemodynamics and clinical usefulness in the management of variceal hemorrhage are discussed. A treatment algorithm for the integrated use of the various treatments is provided.

Transjugular intrahepatic portosystemic shunts (TIPS): a decade later

Since the introduction of transjugular intrahepatic portosystemic shunt (TIPS) 10 years ago, it has been used increasingly in the management of portal hypertension and its complications. TIPS is now considered the procedure of choice for management of refractory variceal bleeding. Its role in the management of refractory ascites, hepatic hydrothorax, hepatorenal syndrome, and hepatopulmonary syndrome still awaits further prospective studies. The two main complications of TIPS are hepatic encephalopathy and shunt malfunction. Generally, TIPS stenosis or occlusion is a major drawback requiring routine surveillance of TIPS with doppler ultrasound. Venography with balloon dilation of the stent or placement of serial or parallel stents may be required in some cases. Promising modalities of preventing TIPS malfunction (e.g., brachy-therapy, covered stents, or anti-platelet derived growth factor) are currently being investigated.

Helical CT angiography of transjugular intrahepatic portosystemic shunts

Shunt dysfunction due to draining hepatic vein and/or stent stenosis is a common long-term complication of transjugular intrahepatic portosystemic shunts (TIPS). Currently, Doppler sonography is the preferred modality for routine screening of TIPS for the detection of these complications. However, this method is time-consuming, highly operator-dependent, and difficult to perform because of the anatomic attributes of the cirrhotic liver. The use of helical CT angiography (HCTA) for imaging TIPS has been recently described. HCTA of TIPS is performed after a rapid i.v. injection of a bolus of low osmolality contrast medium, followed by helical data acquisition of the region of the shunt using thin sections. The data are then reprocessed a overlapping intervals and various reformations are obtained. Preliminary reports show the sensitivity and specificity of the helical CT angiography to be comparable with Doppler sonography.

Ultrasonography. Update on liver technique

Sonography is very useful in the evaluation of the patient with severe liver disease before and after the placement of a TIPS, and before and after organ transplantation. Efforts to use ultrasound to evaluate for primary and metastatic lesions to the liver have been reviewed. With its Doppler and color flow capabilities, ultrasound remains an important modality for hepatic imaging, especially in the evaluation of portal vein patency and hepatic artery thrombosis.

Long-term follow-up after TIPS: use of Doppler velocity criteria for detecting elevation of the portosystemic gradient

PURPOSE

To evaluate the performance of Doppler ultrasound as a screening test for detecting elevated portosystemic gradients in failing transjugular intrahepatic portosystemic shunts (TIPS).

MATERIALS AND METHODS

Twenty-seven of 61 patients who underwent TIPS creation between November 1991 and March 1996 were studied. At routine intervals, angle-corrected velocity measurements of portal venous and intrashunt blood flow (at the portal venous, middle, and hepatic venous levels of the shunt) were obtained. These were compared with portal hemodynamics for diagnostic accuracy in predicting clinically significant elevation of the portosystemic gradient. Venographic and manometric correlations were obtained on all patients available for follow-up and were not limited to those with symptoms or "abnormal" Doppler studies. Receiver-operating characteristic (ROC) curves were done. Linear regression was done to study correlation of shunt velocities with portal pressure, and logistic regression was done to predict shunt stenosis with use of shunt velocities.

RESULTS

The most accurate location for shunt velocity measurement was the main portal vein, but this had an area under the ROC curve of only 0.70. Accuracy of any velocity threshold (including maximum shunt velocity) was no greater than 70%. Maximum shunt velocity of less than 60 cm/sec was 93% specific for detecting shunt restenosis, but only 25% sensitive, for an overall accuracy of 64%. High sensitivity (90%) could only be achieved with poor specificity (< 33%). Linear regression revealed poor correlation between shunt or portal vein velocity measurements and portal pressure (/r/ < 0.23 for all).

CONCLUSIONS

Intrashunt and portal venous Doppler velocities alone do not accurately predict elevation of the portosystemic gradient on long-term follow-up after TIPS.

The hemodynamics of transjugular intrahepatic portosystemic shunts: investigations with Doppler sonography and development of an in vitro model

RATIONALE AND OBJECTIVES

We evaluated Doppler sonography-based measurements of transjugular intrahepatic portosystemic shunt (TIPS) function and developed an in vitro model of normal TIPS hemodynamics.

METHODS

We reviewed retrospectively the results of all trans-TIPS manometries (N = 116) performed during a 24-month period. Portosystemic pressure gradient was compared with peak stent velocity as measured by angle-corrected Doppler sonography. A flow phantom simulating TIPS was created using 8-, 10-, and 12-mm-diameter wire-mesh stents placed in cylindrical channels with lengths ranging from 3.4 to 6.0 cm.

RESULTS

Among 50 trans-TIPS manometries with corresponding Doppler sonography performed on well-functioning shunts, measured portosystemic pressure gradient and peak velocity were not correlated (R2 = .014). On the basis of a regression of measurements in the flow phantom, pressure loss in a stented cylindrical channel was estimated as follows: delta p = rho.(0.145 -0.001.Rey + 0.816.L/D).(Vmean2/2), where rho is the fluid density, Rey is the Reynolds number, L is the channel length, D is the stent diameter, and Vmean is the time-averaged velocity within the stent. Predicted and measured pressure gradients were correlated (R2 = .91).

CONCLUSION

Peak velocity in patients with a normally functioning TIPS does not predict the magnitude of the portosystemic pressure gradient.