정승원 도플러초음파를이용한간문맥과간정맥혈류의측정 도플러초음파를이용한간문맥과간정맥혈류의측정 How to Assess Portal and Hepatic Vein Flow? - Focused on Doppler Sono - 정승원순천향대학교서울병원소화기내과 Soung Won Jeong Division of Gastroenterology, Department of Internal Medicine, Soonchunhyang University Hospital, Seoul, South Korea Portal hypertension (PH) is a major pathophysiology in cirrhosis and the result of increased hepatic vascular resistance and portal blood flow. Hepatic venous pressure gradient (HVPG) has been the gold standard for assessing the degree of PH. However, its invasiveness and limited availability have prompted attempts to develop noninvasive alternatives. Many investigators have tried to diagnose and grade PH using non-invasive ultrasonography (US) to replace HVPG measurements. US can be used to investigate portal hemodynamics via measurements of the velocity and flow of the portal veins and the waveform and damping index (DI) of the hepatic vein (HV). However, portal blood velocity and flow can differ between patients with similar portal pressures due to significant variability in porto-systemic collateral patterns. HV wave form and DI showed an increased accuracy for diagnosing PH, and may be useful for the detection of significant PH. 서론 간경변증에서동반되는문맥압항진증은간문맥과간정맥의혈류에도변화를가져온다. Hepatic venous pressure gradient (HVPG) 는문맥압항진증의정도를평가하는가장정확한검사로시행되어왔지만, [1] 침습적인검사라서, 비침습적이고시행이간편한진단방법들이필요했고, 비침습적인도플러초음파가 HVPG 를대체하여문맥압항진증을진단하고평가할수있도록시도되어져왔다. [2,3] 도플러초음파는펄스파도플러 (pulse waved doppler) 와색도플러 (color Doppler) 를이용하여간문맥과간정맥의혈역학을파악할수있다. 간문맥의도플러초음파 간문맥의도플러초음파측정은심와부의좌측에서 oblique scan 으로간동맥과간문맥이만나는위치 를확인후, 초음파빔과혈류의입사각도가 50-55 도를이루도록탐촉자를위치하고환자는정상호흡에 www.kasl.org 125
2018 대한간학회추계학술대회 서숨을내쉰뒤, 잠시동안숨을멈추도록한상태에서 3.5-5MHz 의 convex probe 를이용하여측정한다. 도플러초음파에서간문맥이나간정맥의혈류를확인할경우에호흡은자연스럽게정상적으로숨을쉬게하면서, 숨을내쉰상태에서잠깐숨을멈추도록하고측정을하는경우에가장좋은결과를얻을수있다. 깊이숨을호흡할경우에는정상간정맥의파형에영향을미칠수있으므로주의한다. 정상적인간문맥의파형은단상파형이며심장의박동에영향을받을수있다 (Figure 1). [4] Figure 1. Normal portal vein waveforms. A. Monophasic waveform with no pulsatility. B. Normal portal vein waveform demonstrating moderate cardiac pulsatility. The minimum velocity is approximately two-thirds the maximum velocity. 정상적인간문맥의혈류는 hepatopetal flow (towards the liver) 이지만심한문맥압상승시에는 hepatofugal flow (away from the liver) 로바뀌게된다 (Figure 2). [4] Figure 2. Total vein flow reversal. Logitudinal view of the main portal vein and right portal vein shows retrograde flow (arrow) in both vessels. 126 대한간학회 Korean Association for the Study of the Liver
정승원 도플러초음파를이용한간문맥과간정맥혈류의측정 문맥압항진증때볼수있는초음파소견의하나로간문맥의직경이증가하는것을확인할수있는데 (Figure 3), 간문맥의정상직경에대해서는연구결과에따라약간씩차이가있다. Goyal 등은간문맥직경의정상상한치를 16mm 로보고하였고 ( 민감도 72%, 정확도 91%, 특이도 100%), [5] 다른연구에서는 13 mm 로보고하였다. [6] 그러나간문맥직경하나로문맥압항진증을진단할수없으며, 간문맥의직경이증가하고간문맥의혈류속도가감소하는경우에문맥압항진증을의심할수있다 (Figure 4). 문맥압항진증에서는간내혈관저항의증가로문맥의혈류속도가낮아져서, 정상인에서는일반적으로 20 cm/sec 내외이나, 문맥압항진증환자에서는연구결과에따라서차이가있으나대개 16 cm/sec 이하로감소되어있다. [7] 그러나, 간문맥혈류속도와 HVPG 와의연관성을조사한체계적문헌고찰에서간문맥혈류속도는 10.2 에서 23.5 cm/s 를보였으며, 9개의연구중에서단지 4개에서만 HVPG 와간문맥혈류속도와의연관성을보였다. [8] 최근의연구에서는대상성간경변에서간문맥혈류속도가 < 12.8 cm/s 일때, 비대상성으로진행될수있는예후인자이며, 비대상성간경변증에서간문맥혈류가역방향 (reverse portal flow) 일때는나쁜예후를시사한다고보고하였다. [9] Figure 3. Longitudinal view of main portal vein. The diameter of portal vein (PV) is 16.9 mm. www.kasl.org 127
2018 대한간학회추계학술대회 Figure 4. Doppler ultrasonography shows that the portal venous velocity is 10.8 cm/s in a patient with liver cirrhosis. 간정맥의도플러초음파 간정맥의도플러초음파측정은늑간스캔에서종축으로우측간정맥을색도플러초음파로확인후에간정맥과하대정맥이나뉘는지점으로부터 3-6 cm 위치에서환자의호기말상태에서숨을잠깐멎게한후에 convex probe 로측정한다. 정상인에서의간정맥의도플러파형은두개의큰전향적혈류 (antegrade flow) 와심방의수축과관련된한개의후향적혈류 (retrograde flow) 에의한삼상파형 (triphasic waveform) 으로나타난다. 그러나간경변증이나문맥압항진증환자에서는정상삼상도플러파형이바뀌어서, 파형의진폭이감소되거나역류가없어져서이상파형 (biphasic waveform) 을보이거나, 파형에진폭이없는단상파형 (monophasic waveform) 으로나타나는데, 약 75-92% 에서비정상적인간정맥파형을보였다. [10] (Figure 5). 특히단상파형을보이는경우는 HVPG 15 mmhg 이상의심각한문맥압항진증을가질가능성이높았다. 128 대한간학회 Korean Association for the Study of the Liver
정승원 도플러초음파를이용한간문맥과간정맥혈류의측정 Figure 5. Hepatic vein waveform on doppler ultrasonography. A. Normal triphasic waveform is composed of two forward flows and one reverse flow. B. In patients with liver cirrhosis and portal hypertension, abnormal flat hepatic vein waverform (monophasic pattern) is observed. Damping Index (DI) 는간문맥의하향파형에서 minimum velocity/maximum velocity로계산하는데 DI 값은 HVPG 와연관성을보이며, DI 값이 >0.6 일경우에는 HVPG > 12mmHG 의상승과관련이보여서 ( 민감도 75.9%, 특이도 81.8%), 간경변의문맥압항진증의평가에유용하게적용할수있음을보여주었다 (Figure.6). [11] Fig. 6. Measurement of damping index (DI) of hepatic vein waveform. DI is calculated by the minimum velocity/maximum velocity of the downward hepatic vein wave. (A) A patient with liver cirrhosis showed 0.26 of DI with 7mmHg of hepatic venous pressure gradient (HVPG). (B) Another patient with liver cirrhosis showed 0.72 of DI with 15mmHg of HVPG. www.kasl.org 129
2018 대한간학회추계학술대회 결론 도플러초음파는간경변증에서간문맥과간정맥의혈역학을측정함으로서비침습적으로문맥압항진증을파악할수있는유용한방법이다. 그러나, 간문맥혈류속도는문맥-전신측부혈관의패턴 (porto-systemic collateral patterns) 에따라서실제적으로는비슷한문맥압을가지고있더라도다를수있으며, 간경변의정도와환자의초음파상의에코에따라서원하는혈관의위치가초음파탐촉자로찾기어려운경우도있으므로검사의재현성에제한점이있을수있다. 간문맥의초음파도플러에비해서간정맥의초음파도플러는재현성이좋고도플러파형과 DI 값을이용한문맥압항진증의평가가환자의간경변증진단에도움을줄수있으나, 마찬가지로환자의초음파창이좋지않거나간경변으로간이심하게위축되어변형된경우등에는검사의제한이있을수있다. 도플러초음파를이용한문맥압항진증의평가에대해서는향후대규모추가연구가필요하다. References 1. Lebrec D. Methods to evaluate portal hypertension. Gastroenterol Clin North Am 1992;21:41-59. 2. Schepke M, Raab P, Hoppe A, Schiedermaier P, Brensing KA, Sauerbruch T. Comparison of portal vein velocity and the hepatic venous pressure gradient in assessing the acute portal hemodynamic response to propranolol in patients with cirrhosis. Am J Gastroenterol 2000;95:2905-2909. 3. Ohnishi K, Saito M, Nakayama T, et al. Portal venous hemodynamics in chronic liver disease: effects of posture change and exercise. Radiology 1985;155:757-761. 4. Robinson KA, Middleton WD, Al-Sukaiti R, Teefey SA, Dahiya N. Doppler sonography of portal hypertension. Ultrasound Q 2009;25:3-13. 5. Goyal AK, Pokharna DS, Sharma SK. Ultrasonic measurements of portal vasculature in diagnosis of portal hypertension. A controversial subject reviewed. J Ultrasound Med 1990;9:45-48. 6. Weinreb J, Kumari S, Phillips G, Pochaczevsky R. Portal vein measurements by real-time sonography. AJR Am J Roentgenol 1982;139:497-499. 7. Al-Nakshabandi NA. The role of ultrasonography in portal hypertension. Saudi J Gastroenterol 2006;12:111-117. 8. Kim G, Cho YZ, Baik SK, Kim MY, Hong WK, Kwon SO. The accuracy of ultrasonography for the evaluation of portal hypertension in patients with cirrhosis: a systematic review. Korean J Radiol 2015;16:314-324. 9. Kondo T, Maruyama H, Sekimoto T, et al. Impact of portal hemodynamics on Doppler ultrasonography for predicting decompensation and long-term outcomes in patients with cirrhosis. Scand J Gastroenterol 2016;51:236-244. 10. Baik SK, Kim JW, Kim HS, et al. Recent variceal bleeding: Doppler US hepatic vein waveform in assessment of severity of portal hypertension and vasoactive drug response. Radiology 2006;240: 574-580. 11. Kim MY, Baik SK, Park DH, et al. Damping index of Doppler hepatic vein waveform to assess the severity of portal hypertension and response to propranolol in liver cirrhosis: a prospective nonrandomized study. Liver Int 2007;27:1103-1110. 130 대한간학회 Korean Association for the Study of the Liver