Hepatic artery: effect of a meal in healthy persons and transplant recipients

Effect of meal intake for evaluating hepatic artery by Doppler ultrasonography in liver transplants: Does fasting matter for screening hepatic artery due to hemodynamic changes in splanchnic circulation?

PURPOSE

The aim of this study is to assess the utility of fasting on Doppler ultrasonography findings of hepatic artery in liver transplants.

METHODS

Liver transplant patients without vascular abnormalities were prospectively evaluated between December 2017 and January 2020. Doppler sonography was used to describe hemodynamic changes in response to a standard meal. The diameter, peak systolic velocity, blood flow, resistive index of the main hepatic artery and portal vein peak velocity were measured.

RESULTS

The mean hepatic arterial diameter of 44 patients was higher in the fasting group (4,5 mm) than in the postprandial group (3,3 mm) (p<0,05). The mean hepatic arterial blood flow decreased (from 0,276 L/min to 0,127 L/min) and hepatic arterial resistive index increased (from 0,66 to 0.71) following meal ingestion (p<0,05). Hepatic arterial velocity was significantly lower and portal venous velocity was higher after oral intake.

CONCLUSION

Meal ingestion has an important effect on hepatic artery Doppler features in liver transplants. Therefore, Doppler ultrasound evaluation should be considered after appropriate fasting due to postprandial responses of liver transplant. This article is protected by copyright. All rights reserved.

Cystic artery velocity as a predictor of acute cholecystitis

PURPOSE

To evaluate angle-corrected peak systolic cystic artery velocity (CAv) as a predictor of acute cholecystitis among patients presenting to the emergency department (ED) with right upper quadrant (RUQ) pain.

METHODS

In this IRB-approved and retrospective study, CAv was evaluated in 73 patients, 43 who underwent definitive treatment with cholecystectomy or percutaneous cholecystostomy and 30 control patients without clinical suspicion for cholecystitis. In addition to CAv, the following were reviewed by 3 radiologists: CBD diameter, cholelithiasis, impacted stone in the neck, sludge, gallbladder wall thickness > 3 mm, gallbladder transverse dimension ≥ 4 cm, longitudinal dimension ≥ 8 cm, tensile gallbladder fundus sign, pericholecystic fluid, pericholecystic echogenic fat, and sonographic Murphy sign.

RESULTS

Of the 43 patients who underwent definitive treatment, 25 had acute cholecystitis (34%) and 18 (25%) had chronic cholecystitis. Average CAv measurements were 50 ± 16 cm/s (acute), 28 ± 8 cm/s (chronic), and 22 ± 8 cm/s (control; p < 0.0001). In univariate analysis, among patients who underwent definitive therapy, CAv ≥ 40 cm/s, gallbladder wall thickness, stone impaction, GB long dimension ≥ 8 cm, and elevated WBC were associated with acute cholecystitis (p < 0.05). In multivariate analysis, CAv ≥ 40 cm/s was the only statistically significant variable (p = 0.016). CAv ≥ 40 cm/s alone had a PPV of 94.7% and overall accuracy of 81.4% in diagnosing acute cholecystitis.

CONCLUSION

CAv ≥ 40 cm/s is highly associated with acute cholecystitis in patients presenting to the ED with RUQ pain.

Doppler ultrasound in liver cirrhosis: correlation of hepatic artery and portal vein measurements with model for end-stage liver disease score in Egypt

Background

Liver cirrhosis is a multi-etiological entity that alters the hepatic functions and vascularity by varying grades. Hereby, a cross-sectional study enrolling 100 cirrhotic patients (51 males and 49 females), who were diagnosed clinically and assessed by model for end-stage liver disease (MELD) score, then correlated to the hepatic Doppler parameters and ultrasound (US) findings of hepatic decompensation like ascites and splenomegaly.

Results

By Doppler and US, splenomegaly was evident in 49% of patients, while ascites was present in 44% of them. Increased hepatic artery velocity (HAV) was found in70% of cases, while 59% showed reduced portal vein velocity (PVV).

There was a statistically significant correlation between HAV and MELD score (ρ = 0.000), but no significant correlation with either hepatic artery resistivity index (HARI) (ρ = 0.675) or PVV (ρ =0.266).

Moreover, HAV had been correlated to splenomegaly (ρ = 0.000), whereas HARI (ρ = 0.137) and PVV (ρ = 0.241) did not significantly correlate.

Also, ascites had correlated significantly to MELD score and HAV (ρ = 0.000), but neither HARI (ρ = 0.607) nor PVV (ρ = 0.143) was significantly correlated.

Our results showed that HAV > 145 cm/s could confidently predict a high MELD score with 62.50% and 97.62 % sensitivity and specificity.

Conclusion

Doppler parameters of hepatic vessels (specifically HAV) in addition to the US findings of hepatic decompensation proved to be a non-invasive and cost-effective imaging tool for severity assessment in cirrhotic patients (scored by MELD); they could be used as additional prognostic parameters for improving the available treatment options and outcomes.

Indirect Doppler ultrasound abnormalities of significant portal vein stenosis after liver transplantation

PURPOSE

To determine indirect Doppler ultrasound (DUS) abnormalities associated with significant portal vein (PV) stenosis (PVS) in recipients of liver transplantation (LT).

METHODS

This retrospective study was approved by our institutional review board. Between February 2006 and May 2017, 41 LT recipients were diagnosed with significant PVS, defined as having more than 50% narrowing of PV diameter for any reason, including thrombosis or flow disturbance associated with prominent collateral vessels on portal venography. We reviewed the DUS findings of hepatic arteries (HAs) as well as PVs of them, before and after treatment of PVS, and in comparison, with a one-to-one case-matched control. Inter-group comparison of frequency in DUS abnormalities was performed using Chi square (χ²) with Fisher's exact test and McNemar's test. Diagnostic values of each abnormal DUS finding and combinations were also evaluated.

RESULTS

DUS of significant PVS showed "no demonstrable color flow," either at recipient PVs or anastomoses (26.7%), and showed turbulence (66.7%) and hepatofugal portal flow (HFPF; 20.0%) at the graft PVs. HFPF was more frequently observed in those with "no demonstrable color flow" at recipient PVs or anastomoses (p = 0.006). DUS of graft HAs revealed tardus-parvus waveforms (20.9%) and prolonged systolic acceleration times (16.3%), more commonly in the "no demonstrable color flow" group (p = 0.012). These indirect DUS abnormalities disappeared and resolved on follow-up DUS after treatment. In the control group, such Doppler abnormalities were less frequently shown than in the PVS group (p ≤ 0.01, respectively). When one of the portal-blood flow velocity (PFV)-related index abnormalities (such as increased time average velocity [TAV] at anastomosis and TAV ratio between recipient PV and anastomosis) or "no demonstrable color flow" were shown in DUS as well as one of the indirect DUS abnormalities, sensitivity, and specificity was 71.11 and 97.78%, respectively.

CONCLUSION

In addition to PFV-related abnormalities, DUS occasionally shows "no demonstrable color flow" either at recipient PVs or anastomoses, and indirect Doppler abnormalities such as turbulence, HFPF at graft PVs, and abnormal waveforms at graft HAs in LT recipients with significant PVS. The combination of PFV-related abnormalities and indirect DUS abnormalities would be helpful for diagnosis of PVS.

Regulation of hepatic blood flow: The hepatic arterial buffer response revisited

The interest in the liver dates back to ancient times when it was considered to be the seat of life processes. The liver is indeed essential to life, not only due to its complex functions in biosynthesis, metabolism and clearance, but also its dramatic role as the blood volume reservoir. Among parenchymal organs, blood flow to the liver is unique due to the dual supply from the portal vein and the hepatic artery. Knowledge of the mutual communication of both the hepatic artery and the portal vein is essential to understand hepatic physiology and pathophysiology. To distinguish the individual importance of each of these inflows in normal and abnormal states is still a challenging task and the subject of ongoing research. A central mechanism that controls and allows constancy of hepatic blood flow is the hepatic arterial buffer response. The current paper reviews the relevance of this intimate hepatic blood flow regulatory system in health and disease. We exclusively focus on the endogenous interrelationship between the hepatic arterial and portal venous inflow circuits in liver resection and transplantation, as well as inflammatory and chronic liver diseases. We do not consider the hepatic microvascular anatomy, as this has been the subject of another recent review.

Regulatory processes interacting to maintain hepatic blood flow constancy: Vascular compliance, hepatic arterial buffer response, hepatorenal reflex, liver regeneration, escape from vasoconstriction

Constancy of hepatic blood flow (HBF) is crucial for several homeostatic roles. The present conceptual review focuses on interrelated mechanisms that act to maintain a constant HBF per liver mass. The liver cannot directly control portal blood flow (PF); therefore, these mechanisms largely operate to compensate for PF changes. A reduction in PF leads to reduced intrahepatic distending pressure, resulting in the highly compliant hepatic vasculature passively expelling up to 50% of its blood volume, thus adding to venous return, cardiac output and HBF. Also activated immediately upon reduction of PF are the hepatic arterial buffer response and an HBF-dependent hepatorenal reflex. Adenosine is secreted at a constant rate into the small fluid space of Mall which surrounds the terminal branches of the hepatic arterioles, portal venules and sensory nerves. The concentration of adenosine is regulated by washout into the portal venules. Reduced PFreduces the washout and the accumulated adenosine causes dilation of the hepatic artery, thus buffering the PF change. Adenosine also activates hepatic sensory nerves to cause reflex renal fluid retention, thus increasing circulating blood volume and maintaining cardiac output and PF. If these mechanisms are not able to maintain total HBF, the hemodynamic imbalance results in hepatocyte proliferation, or apoptosis, by a shear stress/nitric oxide-dependent mechanism, to adjust total liver mass to match the blood supply. These mechanisms are specific to this unique vascular bed and provide an excellent example of multiple integrative regulation of a major homeostatic organ.

Intraoperative direct measurement of hepatic arterial buffer response in patients with or without cirrhosis

The hepatic arterial buffer response (HABR) is an intrinsic regulatory mechanism of the hepatic artery (HA) that compensates for reductions in portal venous (PV) blood flow. Whether this response is maintained in patients with cirrhosis (LC) is unclear. The aim of the present study was to examine whether HABR is maintained in patients with LC using direct blood flow measurements. PV and HA blood flow were intraoperatively measured and compared in patients with (LC group, n = 39) or without (control group, n = 22) cirrhosis at baseline (baseline HABR) and after PV clamping (acute HABR) using an ultrasound transit-time flowmeter. In contrast to the proportional relationship between the baseline PV and HA blood flow observed in the control group, HA blood flow and the HA-PV flow ratio increased when PV blood flow decreased in the LC group, suggesting that the baseline HABR had already been activated. Acute HABR, evaluated by the absolute and relative changes in HA blood flow and by the buffer capacity, was blunted in the LC group (P < 0.001, P < 0.01, and P = 0.01, respectively). An association between the degree of acute HABR impairment and the level of baseline HABR activation (HA-PV flow ratio) could not be confirmed in the LC group. In conclusion, the baseline HABR appears to be continuously activated in patients with LC; this phenomenon probably results in the impairment of the acute HABR.

Use of perfusional angiosonography in liver transplantation and conservative management of post-transplant intra-hepatic pseudo-aneurysm

Hepatic artery pseudo-aneurysm is a rare but severe complication of liver transplantation, which generally requires immediate surgical or angiographic treatment. The diagnosis is usually made by splanchnic percutaneous angiography. We report a case of an intra-hepatic pseudo-aneurysm after surgical correction of a thrombosed hepatic artery and its successful response to conservative management. Duplex Doppler ultrasound, associated with a new B-mode contrast-based sonographic technique, called "perfusional angiosonography", was used to diagnose the intra-hepatic pseudo-aneurysm. The combination of the two ultrasound techniques was useful in following the course of the pseudo-aneurysm, without further need for angiography. Eventually, this pseudo-aneurysm underwent spontaneous obliteration.

Diagnostic value of Doppler assessment of the hepatic and portal vessels and ultrasound of the spleen in liver disease

OBJECTIVES

To investigate the clinical utility and the intra-observer and inter-observer variability of Doppler ultrasound assessment of the hepatic and portal vessels along with measurement of spleen size in the diagnosis of chronic liver disease and cirrhosis.

METHODS AND MATERIALS

Ultrasound measurements of portal vein diameter (PVD), portal vein velocity (PVV), hepatic arterial resistance index (HARI), hepatic vein profile (HVP), and spleen size were obtained in 49 controls and 45 patients with liver disease (23 with primary biliary cirrhosis, 22 with hepatitis C) by two experienced observers, who each performed three blinded measurements of each variable. Control values were derived from normal hospital workers. Percutaneous liver biopsies in 41 of the patients showed cirrhosis (14 patients), moderate/severe fibrosis (13 patients), and early disease (14 patients).

RESULTS

Seventy-one percent of cirrhotic patients had splenomegaly (> 13.6 cm). The spleen size was significantly larger in cirrhotics (16.0 cm) than in non-cirrhotics (13.0 cm, P < 0.009) and healthy controls (10.7 cm, P < 0.00005), and was the only independent predictor of cirrhosis, with a threshold of 15 cm predicting cirrhosis with a specificity of 98%, positive predictive value of 93%, sensitivity of 57% and negative predictive value of 80%. HVP was abnormal in 76.9% of cirrhotics, 57.7% of non-cirrhotics and 2.1% of controls (P < 0.04). However, the mean PVV, PVD and HARI were no different between controls and patients or between cirrhotic and non-cirrhotic liver disease. There was significant inter-observer variability for PVV, but intra-observer and inter-observer variability was acceptable for the other measurements.

CONCLUSIONS

Splenomegaly size and abnormal HVP are useful predictors of chronic liver disease and cirrhosis, and both can be measured reliably and reproducibly. However, Doppler measurements of PVV, PVD and HARI are not useful in distinguishing patients with chronic liver disease from normal controls.

Effect of Levovist on splanchnic hemodynamics in cirrhotic patients

This study was aimed to assess the effect of Levovist on Doppler parameters of splanchnic hemodynamics. A total of 12 patients with cirrhosis and 12 healthy subjects underwent Doppler ultrasound (US) examination of the portal vein and of the hepatic, splenic and superior mesenteric arteries before, 5 to 8 and 12 to 15 min after the start of an 8-min long IV infusion of 2.5 g of Levovist. Mean velocity and mean diameter were calculated for the portal vein. Resistance index was determined for the arteries. A significant increase of resistance index was observed in the hepatic (0.80 +/- 0.07 vs. 0.71 +/- 0.06; p < 0.01) and splenic arteries (0.72 +/- 0.06 vs. 0.64 +/- 0.06; p < 0.01) 5 to 8 min after contrast agent injection in patients with cirrhosis, but not in controls. Neither portal vein diameter nor portal flow mean velocity changed during the test in both controls and cirrhotic patients. This effect might be related to a selective trapping of microbubbles in the altered hepatic and splenic microvasculature in patients with cirrhosis rather than being artefactual. It might have implications on harmonic imaging US protocols designed to image the cirrhotic liver in the early arterial phase.

Duplex Doppler ultrasound of the hepatic artery in patients with acute alcoholic hepatitis

BACKGROUND

Acute alcoholic hepatitis (AAH) is a clinical diagnosis associated with increased hepatic artery diameter and flow. Duplex Doppler ultrasound (DDU) has been shown to accurately measure arterial flow in both liver and kidney transplant patients. The authors conducted a blinded, controlled study to evaluate the accuracy of measuring hepatic artery parameters with DDU in diagnosing AAH.

STUDY

Duplex Doppler ultrasound was performed by an investigator, blinded to group makeup, on 22 consecutive hospital inpatients with the clinical diagnosis of AAH. The diagnosis of AAH was based on specific criteria, including the following: recent alcohol abuse, hyperbilirubinemia, prolonged prothrombin time, leukocytosis, hepatomegaly, hepatic bruit, and marked redistribution of isotope on 99mTc-sulfur colloid liver-spleen scan. Controls were 12 cirrhotic patients without AAH and 17 healthy volunteers. Duplex Doppler ultrasound measurements were obtained most consistently from the proximal right hepatic artery. Measured parameters included the following: peak systolic velocity (PSV); resistive index = (PSV - end diastolic velocity [EDV])/PSV; pulsatility index = (PSV - EDV)/mean velocity; and hepatic artery diameter.

RESULTS

The mean hepatic artery diameter was significantly larger in patients with AAH (3.55 +/- 0.72 mm) than in patients with cirrhosis (2.75 +/- 0.69 mm; p = 0.003) and healthy controls (2.68 +/- 0.69 mm; p = 0.001). The mean PSV was significantly higher in patients with AAH (187 +/- 52 cm/s) compared with cirrhotic (67 +/- 51 cm/s) and healthy (66 +/- 51 cm/s) controls (p = 0.0001). The mean resistive index was lower in AAH patients (0.60 +/- 0.11) compared with cirrhotic (0.69 +/- 0.10; p value was not significant) and healthy controls (0.72 +/- 0.11; p = 0.004). The mean pulsatility index was lower in AAH patients (1.04 +/- 0.47) compared with cirrhotic (1.36 +/- 0.45; p value was not significant) and healthy controls (1.53 +/- 0.45; p = 0.01).

CONCLUSIONS

In the appropriate clinical setting, an elevated hepatic artery diameter or PSV measurement is suggestive of AAH. Duplex Doppler ultrasound offers a noninvasive test to assist in the diagnosis of AAH.

Change in portal flow after liver transplantation: effect on hepatic arterial resistance indices and role of spleen size

Information on changes in splanchnic hemodynamics after liver transplantation is incomplete. In particular, data on long-term changes are lacking, and the relationship between changes in arterial and portal parameters is still under debate. The effect of liver transplantation on splanchnic hemodynamics was analyzed with echo-Doppler in 41 patients with cirrhosis who were followed for up to 4 years. Doppler parameters were also evaluated in 7 patients transplanted for acute liver failure and in 35 controls. In cirrhotics, portal blood velocity and flow increased immediately after transplantation (from 9.1 plus minus 3.7 cm/sec to 38.3 plus minus 14.6 and from 808 plus minus 479 mL/min to 2,817 plus minus 1,153, respectively, P <.001). Hepatic arterial resistance index (pulsatility index) also augmented (from 1.36 plus minus 0.32 to 2.34 plus minus 1.29, P <.001) and was correlated with portal blood velocity and flow. The early changes in these parameters were related, in agreement with the hepatic buffer response theory. Portal flow returned to normal values after 2 years. Superior mesenteric artery flow normalized after 3 to 6 months. Splenomegaly persisted after 4 years, when spleen size was related to portal blood flow. In 7 patients transplanted for acute liver failure, portal flow, and hepatic arterial resistance index were normal after transplantation. In conclusion, a high portal flow was present in cirrhotics until 2 years after transplantation, probably because of maintenance of elevated splenic flow. An early increase in hepatic arterial resistance indices is a common finding, but it is transient and is related to the increase in portal blood flow. A normal time course of portal-hepatic hemodynamics was detected in patients transplanted for acute liver failure.

Radiology in liver transplantation

Imaging studies are becoming essential in the management of orthotopic liver transplantation (LT). They have a very important role in the preoperative evaluation and selection of suitable candidates. At the same time, they are essential in the early detection of postoperative complications, the recognition of which allows the prompt institution of appropriate therapeutic measures. Timely recognition of complications improves the success of LT; furthermore, some complications can be treated with interventional radiologic procedures, avoiding additional surgery. This article reviews the current application of diagnostic and interventional imaging in liver transplantation, both for cadaveric and living donor transplants.

Systemic and splanchnic hemodynamic changes after liver transplantation for cirrhosis: a long-term prospective study

The effect of orthotopic liver transplantation (OLT) on the systemic and splanchnic hemodynamic alterations of cirrhosis is still largely unknown. The aim of this study was to prospectively investigate the long-term changes induced by OLT on several hemodynamic parameters. In 28 patients undergoing OLT for cirrhosis, the following parameters were measured before surgery and subsequently at 6-month intervals (mean follow-up period, 17 months): cardiac index, mean arterial pressure (MAP), heart rate, total peripheral resistance (TPR), portal vein flow velocity and flow volume, spleen size, and Doppler ultrasound resistance or pulsatility indexes (RI or PI) in the: 1) interlobular renal, 2) superior mesenteric, 3) splenic, and 4) hepatic arteries. The same parameters were measured in 10 healthy controls. After OLT, cardiac index and heart rate significantly decreased (P <.01), while MAP and TPR increased (P <.001), so that any significant difference from controls disappeared. Renal RI progressively decreased, achieving a significant reduction (P <.05) to normal values at the 12th month of follow-up. Portal flow velocity and hepatic and splenic RI returned to values not significantly different from controls. Portal flow volume increased over normal values after OLT (P <.001), and SMA PI, lower than normal before OLT, did not show any statistically significant increase thereafter. Spleen size decreased significantly, but persisted to be larger than in controls. In conclusion, systemic, renal, and most, but interestingly not all, splanchnic circulatory alterations of cirrhosis are restored to normal after OLT.

Hepatic arterial resistance after mixed-meal ingestion in healthy subjects and patients with chronic liver disease

PURPOSE

This study investigated hemodynamic changes in the resistance index of the hepatic artery after mixed-meal ingestion.

METHODS

We used color Doppler sonography to measure hemodynamic changes in the right hepatic artery in response to mixed-meal ingestion (225 ml, 69 g, 300 kcal) in 9 healthy subjects, 15 patients with chronic hepatitis with low-grade fibrosis (no bridging), 10 patients with chronic hepatitis with moderate-grade (bridging) fibrosis, and 18 patients with cirrhosis.

RESULTS

After mixed-meal ingestion, the mean (+/-standard error) maximum increase in the resistance index of the right hepatic artery in healthy subjects was 31+/-2%. These changes were significantly greater than those in patients with chronic hepatitis with low-grade fibrosis (22+/-2%; p<0.05), patients with chronic hepatitis with moderate-grade fibrosis (11+/-2%; p<0.01), and cirrhotic patients (5+/-2%; p<0.01). Mixed-meal ingestion produced significantly smaller increases in the resistance index in cirrhotic patients than in patients with chronic hepatitis with low-grade fibrosis (p<0.01). A postprandial increase in the resistance index of 15% or less was associated with 100% sensitivity, 72% specificity, and 84% accuracy in distinguishing patients with cirrhosis from patients with chronic hepatitis.

CONCLUSIONS

The response of the resistance index after mixed-meal ingestion decreases as the severity of hepatic fibrosis increases. Doppler evaluation of postprandial increases in the resistance index of the right hepatic artery may be useful in differentiating between patients with chronic hepatitis and those with cirrhosis.

Hepatic arterial pulsatility index in cirrhosis: correlation with portal pressure

BACKGROUND/AIMS

Determination of the pulsatility index by means of duplex sonography provides the opportunity to evaluate the vascular resistance of the hepatic artery noninvasively. The aim of this study was to investigate the relationship between the hepatic arterial pulsatility index and the hepatic venous pressure gradient in cirrhosis.

METHODS

In 50 patients with cirrhosis, hepatic venous pressure gradient was determined in the fasting state. Immediately thereafter, hepatic arterial pulsatility index and portal blood flow velocity were measured by duplex sonography with no knowledge of hepatic venous pressure values. In addition, the duplex parameters were determined in 20 controls.

RESULTS

Hepatic arterial pulsatility index was significantly higher in patients with cirrhosis than in controls (0.92+/-0.1 vs. 1.14+/-0.18; p<0.001) and directly correlated with the hepatic venous pressure gradient (r = 0.7; p<0.001). Furthermore, weak correlations were found between hepatic arterial pulsatility index and Child-Pugh score (r = 0.49; p<0.01) and between portal blood flow velocity and hepatic venous pressure gradient (r = -0.48; p<0.01).

CONCLUSION

In cirrhosis the hepatic arterial vascular resistance seems to increase parallel to the rise of the portal pressure. Therefore, duplex sonographic determination of the hepatic arterial pulsatility index may contribute to the noninvasive evaluation of portal hypertension.

Doppler sonographic assessment of functional response of the right and left portal venous branches to a meal

PURPOSE

The aim of our study was to quantitate by Doppler sonography the blood flow in the right and left portal vein branches before and after a standard meal. We also assessed the functional response of the right and left lobes of the liver.

METHODS

Portal blood flow was measured by Doppler sonography in the left and right portal vein branches and main portal trunk in 20 healthy volunteers in both fasting and postprandial states. The ratio between portal blood flow and liver volume (determined by MRI) was the portal flow index (PFI).

RESULTS

Before the meal, a statistically significant difference in portal blood flow volume was observed between the right and left portal branches (p < 0.01). The right PFI (0.83 ml/minute/cm3) and left PFI (1.1 ml/minute/cm3) were also significantly different (p < 0.01). The increase in portal venous blood flow after a meal was found to be greater in the left portal branch (128%) than in the right portal branch (78%). The postprandial PFI also differed significantly (right, 1.54 ml/minute/cm3; left, 2.5 ml/minute/cm3).

CONCLUSIONS

These findings suggest that the left lobe of the liver has a better postprandial compliance than the right lobe has.

Duodenal meal stimulation leads to coeliac artery vasoconstriction and superior mesenteric artery vasodilatation: an intra-abdominal ultrasound study

To evaluate the influence of duodenal feeding on splanchnic blood flow, 14 patients with normal coeliac and superior mesenteric arteries underwent intra-abdominal duplex scanning of the systemic and splanchnic circulation under standardised basal and meal-stimulated conditions. Doppler samples and diameter measurements were taken of the aorta, coeliac artery, common hepatic artery, splenic artery, superior mesenteric artery, and inferior mesenteric artery. Duodenal meal stimulation has no systemic effects (p > 0.4). However, duodenal meal stimulation results in coeliac artery vasoconstriction (p < 0.06) and superior mesenteric artery vasodilatation (p < 0.05). This study supports other reported results that gastrointestinal blood flow is dependent on the site of food stimulation.

Doppler study of fasting and postprandial resistance indices in the superior mesenteric artery in healthy subjects and patients with cirrhosis

PURPOSE

We assessed the resistance index (RI) in the superior mesenteric artery under fasting and postprandial conditions in healthy subjects and in patients with cirrhosis to determine whether the amount of change in the RI reflects the presence or severity of liver dysfunction.

METHODS

Fifteen subjects with normal livers and 27 patients with cirrhosis underwent Doppler sonography of the superior mesenteric artery before and after ingesting a standard meal. The RI at baseline (fasting state) and the postprandial RI were compared between the 2 groups. The fasting RIs and post postprandial RIs changes in cirrhotic patients were correlated with the severity of disease.

RESULTS

No difference was found between the baseline RIs in healthy (RI = 0.85) and cirrhotic subjects (RI = 0.84), nor was there a difference in baseline RIs between subgroups of cirrhotic patients according to the severity of liver disease. The RI decreased significantly (p < 0.05) after the meal in both the healthy (13%) and cirrhotic (8%) subjects, but the postprandial decrease was significantly less pronounced (p < 0.05) in cirrhotic patients than in healthy subjects. Among cirrhotic patients, there was no correlation between the postprandial decrease of the RI and severity of liver disease.

CONCLUSIONS

The marked decrease in the postprandial RI in the SMA in healthy subjects is generally not seen in patients with cirrhosis, and changes in the postprandial RI do not reliably predict the severity of liver dysfunction.

Hemodynamic changes in hepatic artery after glucose ingestion in healthy subjects and patients with cirrhosis

PURPOSE

The purpose of this study was to investigate hemodynamic changes in the hepatic artery after glucose ingestion.

METHODS

We used color Doppler sonography to measure hemodynamic changes in the right hepatic artery and the right portal vein in response to glucose ingestion (225 ml, 300 kcal) in 25 healthy subjects and 25 patients with cirrhosis.

RESULTS

In healthy subjects, the peak systolic and end-diastolic velocities in the right hepatic artery decreased (33 +/- 3% and 53 +/- 3%) from baseline velocities measured in the fasting state. The resistance index of the right hepatic artery and the velocity in the right portal vein in these subjects significantly (p < 0.01) increased (14 +/- 2% and 32 +/- 2%) from baseline values after glucose ingestion. Glucose ingestion produced significantly (p < 0.01) smaller changes in cirrhotic patients. The maximum decrease in the peak systolic and end-diastolic velocities in the right hepatic artery were 13 +/- 2% and 25 +/- 3% from baseline velocities, and the maximum increases in the resistance index of the right hepatic artery and the velocity in the right portal vein were 6 +/- 1% and 10 +/- 3% from baseline values.

CONCLUSIONS

The decrease in blood flow velocity in the right hepatic artery after glucose ingestion is presumably a homeostatic mechanism to maintain constant hepatic perfusion. This reciprocal response was reduced in cirrhotic patients.

Beneficial hemodynamic effects of dipyridamole on portal circulation in cirrhosis

OBJECTIVE

Dipyridamole is a vasodilator that inhibits the cellular uptake of adenosine, which physiologically reduces the resistance to hepatic arterial flow inside the liver. This study aims at assessing the acute effect of dipyridamole on functional liver plasma flow (measured as the extrarenal sorbitol clearance) and on the Doppler US Congestion Index of the portal vein (the ratio between the cross-sectional area of this vein and the mean velocity of portal flow), which correlates with the severity of portal hypertension.

METHODS

We have determined the extrarenal sorbitol clearance (14 cases) and the Congestion Index (seven cases) before and at 30, 60, and 90 min after the oral administration of 25 mg dipyridamole in patients with liver cirrhosis. We also measured the effect of dipyridamole on functional liver plasma flow in six healthy subjects.

RESULTS

Dipyridamole increased the extrarenal sorbitol clearance in controls (+17%, p < 0.01) and in cirrhotic patients (+15%, p < 0.01). The drug decreased the portal Congestion Index in all patients, averaging -24% (p < 0.05) 90 min after its oral administration.

CONCLUSIONS

This result was due both to a mean decrease of the portal sectional area and to a mean increase in portal flow velocity. In conclusion, these data suggest that dipyridamole should decrease the vascular resistance to portal flow in cirrhosis; this effect may be mediated by an adenosine-dependent vasodilation in the intrahepatic site or along the portosystemic collaterals.

Interobserver and interequipment variability of hepatic, splenic, and renal arterial Doppler resistance indices in normal subjects and patients with cirrhosis

BACKGROUND/AIMS

Doppler arterial resistance indices are used to evaluate alterations in arterial hemodynamics in the liver, spleen, and kidney. The purpose of this study was to determine the interobserver and interequipment variability of hepatic, splenic, and renal arterial Doppler resistance indices, and the influence of a cooperative training program of the operators on the reproducibility of the results.

METHODS

In the first part of the study, hepatic (PI-L, RI-L), splenic (PI-S, RI-S), and renal (PI-K, RI-K) pulsatility and resistive indices were measured by echo-color-Doppler in eight control subjects and ten patients with cirrhosis by three operators using three different machines. In the second part of the study, measurements were taken by the three operators in nine controls and nine patients with cirrhosis, after cooperative training, with a single machine.

RESULTS

Significant interobserver variability was present for all parameters except RI-L. Significant interequipment variability was present for all parameters except PI-S and RI-S. Only 0-3% of variance was equipment- or operator-related, while 58-72% was patient-related. Hepatic and renal coefficients of variation were similar in patients with cirrhosis and controls, while splenic coefficients of variation were higher in patients with cirrhosis than in controls. After training, differences among operators disappeared for all variables except RI-K, and the operator-related component of variance nearly disappeared for all parameters.

CONCLUSIONS

Hepatic, splenic, and renal arterial resistance indices show small but significant interobserver and interequipment variability. Interobserver variability can be decreased to non-significant levels by a common training program. Thus, these indices can be widely applied to the study of arterial circulation in these organs.

The 1995 Ciba-Geigy Award Lecture. Intrinsic regulation of hepatic blood flow

Intrinsic regulation of hepatic blood flow is mediated only through the hepatic artery because the liver is not able to directly regulate portal vein blood flow. Hepatic metabolic activity does not affect hepatic artery flow. Although the hepatic artery is affected by sympathetic nerves and blood-borne agents, the intrinsic regulation of the hepatic artery can be demonstrated if these factors are controlled. The primary intrinsic regulator of the hepatic artery is the hepatic arterial buffer response, which is the inverse response of the hepatic artery to changes in portal vein flow. The hepatic arterial buffer response is sufficiently powerful that doubling portal vein flow leads to maximal constriction in the hepatic artery, while low portal vein flow can result in maximal dilation. The mechanism of the hepatic arterial buffer response is based on adenosine washout, whereby adenosine is produced at a constant rate, independent of oxygen supply or demand, and secreted into a small fluid compartment that surrounds the hepatic arterial resistance vessels. If portal vein flow decreases, less adenosine is washed away into the portal blood and the accumulated adenosine leads to hepatic arterial dilation. Similarly, hepatic arterial autoregulation operates by the same mechanism, whereby a decrease in arterial pressure leads to a decrease in hepatic arterial flow, thus resulting in less adenosine washout into the hepatic artery blood. The accumulated adenosine leads to hepatic artery dilation. These intrinsic regulatory mechanisms tend to maintain total hepatic blood flow at a constant level, thus stabilizing hepatic clearance of hormones, venous return, and cardiac output.

Hepatic arterial resistance in cirrhosis with and without portal vein thrombosis: relationships with portal hemodynamics

BACKGROUND/AIMS

Little information is available on hepatic arterial hemodynamics in cirrhosis because of the invasiveness of methods. Hepatic arterial resistance indexes were evaluated noninvasively by Doppler ultrasonography and were correlated with portal hemodynamics evaluated both noninvasively and invasively.

METHODS

Hepatic arterial resistance indexes, portal blood flow velocity and volume, and portal vein congestion index were evaluated in 31 controls and 171 cirrhotic patients with (n = 13) or without (n = 158) portal vein thrombosis. Resistance to portal blood flow was also calculated in 15 patients from hepatic venous pressure gradient, measured by hepatic vein catheterization, and portal blood flow.

RESULTS

Resistance indexes were significantly higher in cirrhotics without portal thrombosis than in controls (pulsatility index, 1.30 +/- 0.29 vs. 0.89 +/- 0.09; P < 0.001; resistive index, 0.71 +/- 0.07 vs. 0.59 +/- 0.04; P < 0.001). In patients with portal thrombosis, the pulsatility index (1.86 +/- 0.39) and resistive index (0.81 +/- 0.06) were significantly higher than in controls (P < 0.001) and in patients without thrombosis (P < 0.001). Resistance indexes directly correlated with portal resistance (P < 0.01), the congestion index (P < 0.01), and the degree of esophageal varices (P < 0.01).

CONCLUSIONS

Hepatic arterial resistance indexes increase in cirrhosis, particularly with portal vein thrombosis. The pathophysiology of the increase in hepatic arterial resistance seems to be parallel to that of portal resistance.