Hepatic Vasculature: A Conceptual Review Yet, about 20years ago, A. Bejan25 proved that dendritic configurations can be predicted, and that they exist for a very specific purpose. Radiology 256(1):3261. J Plast Reconstr Aesthet Surg 61(5):562565, discussion 565, Tonolini M, Campari A, Bianco R (2012) Extravasation of radiographic contrast media: prevention, diagnosis, and treatment. Differential enhancement of false lumen of an aortic dissection can also be due to delayed opacification due to higher inherent luminal pressures. The portal vein (which is rich in nutrients and relatively high in oxygen) provides two thirds of blood flow to the liver. The portal vein and hepatic arteries form the liver's dual blood supply. Approximately 75% of hepatic blood flow is derived from the portal vein, while the remainder is from the hepatic arteries. [4] Unlike most veins, the portal vein does not drain into the heart. Causes of splenomegaly are myriad, as are the read more . These are, however, not commonly seen in left atrium or left ventricle, and whenever seen should be considered abnormal (Fig. A less dramatic, but equally important observation may be seen in patients with congestive heart failure with resultant poor or no opacification of left cardiac chambers and aorta during a CT pulmonary angiogram (Fig. Anatomical variations of the hepatic artery are important in the planning and performance of abdominal surgical procedures. PubMed Central In addition, use of distal access sites (i.e. reports a lobule permeability of 4.8 109 m2. With this end goal in mind, understanding the anatomy and physiology of the cardiovascular system as it pertains to contrast flow dynamics can serve as a useful starting point. 4 with the definition of the fluid volume Vd12L1i=0g3i/3ki, we finally write: We demonstrated previously that the most efficient flow architectures are the ones featuring equipartition of thermodynamics imperfections32. Use OR to account for alternate terms Murray CD. In the simplest case we assume that the ducts have a round cross section of diameter d and length L. The pulsatile nature of blood flow in the hepatic artery network is classically expressed through an electrical impedance analogy. Use for phrases Plaats AVD, et al. Detailed measurements of the geometrical features of the human liver blood network are scarce. 2). For the right atrium, usually the normal diameters suggested by echocardiography on four-chamber view have been used: right atrium (long-axis dimensions 3.45.3cm and 2.64.4cm for short axis) and for right ventricle (basal dimensions 3.94.5cm and longitudinal dimension 89.1cm) [5]. Korean J Radiol: Off J Korean Radiol Soc 15(3):322329, Lidegran MK, Ringertz HG, Frenckner BP, Linden VB (2005) Chest and abdominal CT during extracorporeal membrane oxygenation: Clinical benefits in diagnosis and treatment. Alternatively, new access from the contralateral extremity vein can be obtained. 1). This resulted in peak pressure reaching 300psi with resultant disarming and decreased flow rate of 2.8mL/s with suboptimal pulmonary artery enhancement. There may be more than one type of CT scanner within the same hospital system. Some authors use a 1-min delay provided the injection is antecubital due to shorter distance to pulmonary artery and in patients with cavopulmonary connections than atriopulmonary connections [28]. Google Scholar, National Center for Health Statistics, Emergency Department Summary Tables (2011).17, Sohrabi S, Hope M, Saloner D, Keedy A, Naeger D, Lorca MC et al (2015) Left atrial transverse diameter on computed tomography angiography can accurately diagnose left atrial enlargement in patients with atrial fibrillation. Control of hepatic blood flow J Am Soc Echocardiogr: Off Publ Am Soc Echocardiogr 23(7):685713, quiz 786-688, Article Mixing artifacts in the true lumen of the descending aortic aneurysm with Type B aortic dissection which resolve on delayed phase acquisition. Missing is a theoretical approach, based on first principles, that would allow to predict the flow architecture of the hepatic circulation: liver transplant, or liver resection as a treatment for liver tumors, may end up to liver failure with disastrous consequences when the change in blood pressure is not controlled1416. The modeling of the hepatic circulation has been a challenge for several decades. Contrast flow and enhancement patterns seen on CTA can often be challenging and may often reveal more than is immediately apparent. The hemodynamics of flow in these patients, especially those on a venoarterial ECMO, are altered, with retrograde flow occurring in the access artery and in case of femoral artery access, in theaorta [32]. The hepatic artery (which is oxygen-rich) supplies the rest. The hepatic artery originates from the common hepatic artery and divides into the right and left hepatic arteries. Street network theory of organization in nature. The physiological principle of minimum work: I. All the cells of the porous lobule-system fulfill the metabolic and filtering functions. The objective of this work is to lay the theoretical foundations of the deterministic behavior of the human liver vasculature, as a hierarchical fluid mechanics system. Two graphs are generated by the power injector, which plot the change in pressure over time and flow rate of the injection over time (3 A, B). In type B dissection, identification of false lumen thrombus can be overestimated by first pass CTA/MRA. The minimum pressure difference is obtained by minimizing p for the fixed volume V. The corresponding diameter ratio is given by31: As the splitting number is n = 3 on an average, Eq. Unless the vessel is patent, additional studies should be performed with a contralateral upper extremity injection to permit adequate contrast opacification. A physiologically-based flow network model for hepatic drug elimination II: variable lattice lobule models. Size of the cannula used for delivery of contrast medium is important to achieve the desired flow rate for the duration of the injection [9]. In the absence of more precise data, Eq. Miguel AF. Non-target vessel opacification may hold key to underlying pathophysiology. Why the bigger live longer and travel farther: animals, vehicles, rivers and the winds. The radial distribution of the fluid would generate a flow resistance P/mradial which order of magnitude is R/3gdradial4. Torres Rojas AM, Meza Romero A, Pagonabarraga I, Travasso RDM, Corvera Poir E. Obstructions in vascular networks: relation between network morphology and blood supply. Pericardial tamponade on CECT. If pain is the main symptom, we use cold compresses, and if the extravasation has occurred in a location where there is a higher likelihood of compartment syndrome, we use hot compresses. A physiologically-based flow network model for hepatic drug elimination I: regular lattice lobule model. The .gov means its official. WebAnswer (1 of 1): The portal vein and hepatic artery provide blood flow to the liver. The shape of the liver is assumed to be a hemisphere with a radius R, the center of which being located at the level of the blood inlet (Fig. When using a scanner with shorter acquisition time, non target vessel enhancement may be less than expected, and these vessels should be interpreted with caution. Hepatic vasculature: a conceptual review - PubMed Landes, G. Einige Untersuchungen an elektrischen Analogieschaltungen zum Kreislaufsystem. Hepatic infarction results from hepatic artery disorders. Fontan shunt is performed as the third stage of ventricular repair and involves anastomosis between the IVC and the left pulmonary artery. This dual, reciprocally compensatory blood supply provides some protection from hepatic ischemia in healthy people. Kim S, Lorente S, Bejan A. Vascularized materials: tree-shaped flow architectures matched canopy to canopy. Contrast opacifies the right portal vein secondary to backflow from hepatic vein into portal vein. Regardless of the post-extravasation treatment method, patients should be evaluated by the radiologist. Blood vessels of abdomen and pelvis : Anatomy overview | Kenhub 1). LIVER AND BILIARY: Normal liver morphology and enhancement. J Comput Assist Tomogr 34(1):7581, Clough RE, Hussain T, Uribe S, Greil GF, Razavi R, Taylor PR et al (2011) A new method for quantification of false lumen thrombosis in aortic dissection using magnetic resonance imaging and a blood pool contrast agent. The liver vasculature makes its unique among the other organs as it is made of the superimposition of three main networks, two inlets and one outlet. The narrowing of the left subclavian vein prevented adequate opacification of the pulmonary artery. However, the arrival of contrast media may not always be simultaneous due to different resistance, collaterals, and flow velocities. Each central vein of a hexagon receives mh/6 from the 6 triads distant of Lh from the central vein (the hexagon is made of 6 equilateral triangles of side Lh). We observe the patient in the radiology department for at least 1h to ensure that there are no new symptoms, such as pain or numbness to suggest development of compartment syndrome. Lucia U, Grisolia G. Time: a constructal viewpoint & its consequences. There is no solution to this artifact once acquired, but this can be avoided by using spiral instead of axial acquisitions. In the case of fluid flow networks it means that the minimum pumping power is found when the pressure losses are equally distributed over the flow architecture. Imaging Pearl: Different approaches have been suggested to perform contrast-enhanced CTA in patients on ECMO: injection into the arterial cannula of the ECMO after the membrane oxygenator or into the venous line distal to the membrane oxygenator [33]. The study indicated that the tube length ratio (daughter tube length divided by mother tube length) for minimum pumping power was a constant of about 0.50 regardless the number of tubes connected to the center of the disk. As the majority of thoracic CTAsare performed with the patients arms raised, compression of the subclavian vein (asymptomatic or symptomatic) can lead to compromises in IV contrast delivery to the central vascular structures, affecting bolus timing and leading to suboptimal opacification due to reductions in flow rate (Fig. Considered a physiologic artifact, transient attenuation or interruption of the contrast bolus refers to disruption of the normal opacified contrast column secondary to return of unopacified venous blood via the inferior vena cava (IVC) in the setting of deep inspiration (Fig. The authors published the radii, lengths and number of branches of the hepatic artery, the portal vein and the hepatic vein. Test. statement and 18 gives a permeability K ranging between 3 1010 m2 and 9 1012 m2. WebThe hepatic circulation is highly sensitive to changes in circulating blood volume and serves as a major buffer for expanded or contracted blood volume. To confront the theoretical approach developed in this paper to experimental data, we rely on anatomic results provided by two different groups19,22,29. Radiology 236(1):369370, author reply 370, Bae KT (2010) Intravenous contrast medium administration and scan timing at CT: considerations and approaches. Cookies policy. No peripancreatic fluid. Lee J, Kim S, Lorente S, Bejan A. Vascularization with trees matched canopy to canopy: Diagonal channels with multiple sizes. The blood distribution within the lobule is similar to a reverse river basin connecting rivulets to a central sink. 13), and when using prospective ECG triggered CTA (Fig. Therefore, from the measurements of 4 representative portions of the liver, they considered that the total number of branches could be estimated in proportion of the total liver volume. For example, for a pulmonary embolus study, we use a post-threshold delay of at least 5s on a 64 slice scanner, buta longer delay of 8sis used on a 256 or a dual source scanner. We consider that Ah=AS, which means that the hexagon is reshaped to become a square, and LS=33/42Lh1.6Lh. Fisher B, Updegraff H. Effect of increased hepatic blood flow upon liver regeneration. Bhattacharya S, Shoda LKM, Zhang Q, Woods CG, Howell BA, Siler SQ, Woodhead JL, Yang Y, McMullen P, Watkins PB, Andersen M. E modeling drug- and chemical-induced hepatotoxicity with systems biology approaches. WebUltrasound demonstrated a sonographically normal liver without nodularity or cirrhosis and patent hepatic vasculature ( Fig. {"url":"/signup-modal-props.json?lang=us"}, Hartung M, How to read a CT of the abdomen and pelvis. The portal vein brings blood rich in nutrients and antigens from the gastrointestinal system. Proc Staff Meet Mayo Clin 31(9):281287, CAS Accounting for the discrepancy of the measurements from one generation level to the other, we consider the predicted value of 3-1/3 0.69 as reliable. Part of 7a and b). Bejan A, Tondeur D. Equipartition, optimal allocation, and the constructal approach to predicting organization in nature. The hepatic artery, portal vein and hepatic vein form a compact three-dimensional dendritic architecture within the liver. Portal hypertension can also cause varices (abnormally enlarged blood vessels) in the esophagus or stomach that may become prone to bleeding. Debbaut C, et al. 4, we see that the square image is made of about 16 hexagonal shapes of side Lh. Considering Darcy flow through the porous elemental system (i.e. Case study, Radiopaedia.org (Accessed on 01 May 2023) https://doi.org/10.53347/rID-66174. In this work we show that the challenge of predicting the hepatic multi-scale vascular network can be met thanks to the constructal law of design evolution. Delayed phase acquisition is recommended for a more accurate estimation of true extent of false lumen thrombus vs. slow flow. CECT shows marked left atrium enlargement (arrow) with mixing of opacified blood coming from pulmonary veins and non-opacificed blood from the left ventricle due to severe mitral regurgitation. Axial CTA shows moderate pericardial effusion and heterogeneous enhancement of descending aorta with blood contrast layering. Careful interpretation of power injector graphs, location of region of interest to trigger the scan, and pattern of contrast flow can help determine the cause. Each square element receives the blood from each of its 4 corners. This can lead to differential enhancement in different segments of the aorta, which merely indicates different contrast density at different time points. Insights into Imaging PubMedGoogle Scholar. Evaluation of these graphs is important in identifying the planned flow rate and any changes to that. This canopy-to-canopy feature is complemented by a porous medium, the lobules. Modify the injection protocol and post-threshold delay based on these factors. 6). The hepatic artery provides oxygenated blood to the liver, while the portal vein brings deoxygenated blood; the two mix in the sinusoids. In their 2005 paper, Wechsatol et al.33 documented the design of laminar dendritic networks on a fixed disc-shaped area. The two inlet Mosharaf-Dehkordi M. A fully coupled porous media and channels flow approach for simulation of blood and bile flow through the liver lobules. PubMed JBR-BTR 96(5):304307, Tsai PP, Chen JH, Huang JL, Shen WC (2002) Dependent pooling: a contrast-enhanced sign of cardiac arrest during CT. AJR Am J Roentgenol 178(5):10951099, Roth C, Sneider M, Bogot N, Todd M, Cronin P (2006) Dependent venous contrast pooling and layering: a sign of imminent cardiogenic shock. Consequences read more . If g is the generation number (g may vary from one tree to another) than the total number of HA (or PV) outlets or HV inlets is ng=3g, with a splitting number n=3. Unless sagittal images are also reviewed, this subtle sign may be the only significant clue seen on axial CTA images. CTA shows contrast reflux into IVC and dependent hepatic veins and blood-contrast level in the IVC. When present, these findings should raise the suspicion of altered flow dynamics including underlying intra- or extra-cardiac shunt. In. Differential enhancement of pulmonary arteries during a pulmonary artery CTA can be seen in patients with Fontan circulation (Fig. EXAMPLE REPORTING TEMPLATE WITH CHECKLIST: LOWER CHEST: Lung bases are clear. When using a scanner with shorter acquisition time, non-target vessel enhancement may be less than expected and these vessels should be interpreted with caution. The inlet flow comes from the hepatic artery and the portal vein constituting the triad (the third element being the bile canal). Assume one main sinusoid of diameter dh connects a triad to the central vein. Imaging pearl: In patients with known aortic aneurysm, ROI for test bolus or bolus tracking should be placed in that portion of the aorta which has the largest diameter. The overall pressure loss from the hexagon rim to the central vein is the sum of the pressure losses along the branches of the flow dendritic pathway. ADVERTISEMENT: Supporters see fewer/no ads. This should not be confused with a thrombus. From one source, the blood not only invades the sinusoids network in the broad direction of the central vein, but it must also flow along the hexagon periphery at mid-distance from the two neighboring sources. Central veins of the thorax convey blood/contrast bolus to the right atrium. As each square element is in contact with 3 other ones, the mass flow rate through the duct of diameter d and length Ld must be mh. We do not control or have responsibility for the content of any third-party site. 1Department of Mechanical Engineering, Villanova University, Villanova, PA 19085 USA, 2Departamento de Fsica, Facultad de Ciencias, Universidad Nacional Autnoma de Mxico, Circuito Exterior S/N, Ciudad Universitaria, CP04510 Coyoacn, Ciudad de Mxico, Mexico, 3Centro Mdico 20 de Noviembre, ISSSTE,, Flix Cuevas 540, Del Valle Sur, Benito Jurez, CP03100 Ciudad de Mxico, Mexico. Using contrast enhancement and flow patterns to identify the cause of a non-diagnostic CTA. Hopkins Medicine Nevertheless considering that the hexagonal shape is close to the circle shape, the same expression was used in this work to predict the order of magnitude of the lobule permeability. White D, Coombe D, Rezania V, Tuszynski J. Imaging Pearl: Manufacturer recommendations for the central venous catheter that is being used should be adhered to for peak flow rate. Understanding these graphs will help the radiologist plan a repeat contrast injection to overcome the deficiencies of the first injection and thus obtain a diagnostic scan. There is controversy regarding the clinical significance of this finding. Review of the axial images in the upper abdomen (b) reveal contrast reflux into IVC, dependent hepatic veins, and a blood-contrast level in the IVC. This prompted initiation of cardiopulmonary resuscitation and calling the code team. Bejan A. 2), the contrast enhancement may or may not rise as quickly as expected (2). Also note the differential enhancement in descending aorta. The proximal end of the stent extends into the right atrium in this patient, who was not a suitable candidate for liver transplantation. Ma R, et al. The hexagonal cross section shows 6 portal triads made of the bile duct, the portal vein and the hepatic artery. In our approach, the liver becomes a multi-scale dendritic fluid network constituted of superimposed tree-shaped architectures that provides and drains the blood flow. Hepatic Artery and Their Importance On an average, the measured splitting number is 2.76 for the hepatic artery, 2.80 for the portal vein, and 3.22 for the hepatic vein, which translated into the integer n = 3. Alalaimi M, Lorente S, Wechsatol W, Bejan A. Pater L, Berg J. one lobule), the average velocity of the blood flowing to the central vein is. Vasculature The three tree-shaped architectures correspond to a volume-to-point flow. Before Differential aortic enhancement can also be seen in patients with coarctation of aorta (Fig. WebThe Hepatic circulation is unique among vascular beds. Repeat injection with the left arm downby the patients side (b) shows excellent opacification of the left subclavian vein and no filling of venous collaterals, permitting a diagnostic scan for evaluation of pulmonary embolus, Chronic left subclavian vein thrombus with venous collateral formation. Greenway CV, Stark RD. WebPortal Circulation. Why a hexagon? 9). The lobule is considered to be the liver functional unit, the elemental system. Necrosis The iliac arteries branch off of the bottom of the aorta, the large artery coming out of the top of the heart. Peak flow rate needed varies on the indication for the CTA: preferred flow rate for pulmonary artery CTA is 35cc/s [10], for aortic evaluation is > 3cc/s [11], and for coronary artery assessment is>5cc/s [12] (Table 3). Please confirm that you are a health care professional. The Physics of Life: The Evolution of Everything. ADVERTISEMENT: Radiopaedia is free thanks to our supporters and advertisers. This is indicative of poor stroke volume from tamponade. The volume of blood flowing through the lobule is a constant. In case of an access vein size and i.v. The patient is instructed to seek medical attention if new neurologic or circulatory symptoms or skin ulceration develop [9]. CT image during test bolus injection (a) with regions of interest over the ascending aorta (1), descending aorta (2) and pulmonary artery (3). 3a), leak at the level of the hub (Fig. We gathered the values of fn from Wechsatol et al.33 They are 13.16, 16.31, 18.67, 20.5, 21.8 and 22.6 for n=2 to 7 respectively, which means that for increasing pairing levels, fn reaches an asymptote close to 25. The total number of squares is the same as the number of hexagons, namely 16. Before discharge, a radiologist discusses the findings that would suggest a developing compartment syndrome with the patient. The necessary pumping power is provided by the heart, and is proportional to mp. Blood then enters the right ventricle across the tricuspid valve. The splitting number is calculated from the ratio of the number of daughter branches and mother branches. Use of delayed images after 30s can help differentiate soft plaque/thrombus from slow flow when dependent pooling is seen. A test bolus is preferable to bolus tracking in patients with post-surgical repair of complex congenital heart diseases. The total pressure difference between the inlet and the outlet of a lobule is given by, Another way to pave entirely the square domain represented in Fig. Repeat injection with placement of ROI in true lumen resulted in adequate evaluation of dissection. Patients receiving chemotherapy also have an increased risk due to fragile, damaged, and often small caliber vessels. Delayed phase CECT in the same patient (b) shows resolution of the mixing artifact. Enter search terms to find related medical topics, multimedia and more. Manifestations of focal venous obstruction depend on the location. Each tree architecture is composed of a main trunk subdivided into smaller and smaller braches. S.L. PubMed Sketch of hexagonal (left side) and square configurations (right side). The flow resistance created in the case of a dendritic design is given by. In our experience, slowing the flow of the circuit to the minimal flow rate that would prevent thrombus formation for the duration of the scan (1520s) has worked well in cases of suspected pulmonary embolism (Fig. An electrical analogue of the entire human circulatory system. The entire network is similar to a river delta, except that in the case of the lobule the fluid flows in the reverse direction as in the river basin. No masses. No abdominal aortic aneurysm. The 10). Contrast opacifies the right portal vein secondary to backflow from hepatic vein into portal vein. In addition, attempts to remove the extravasated contrast via aspiration have not been shown to be consistently beneficial. The liver vasculature makes its unique among the other organs as it is made of the superimposition of three main networks, two inlets and one outlet. Alternate breathing instructions include requesting the patient to stop breathing or to take a slow gentle breath [20, 22]. Combining Eq. cannula mismatch the pressure may exceed the threshold, which may limit the flow rate. The lobules area porous medium located between the tree canopies. The portal venous system drains the intestines, pancreas, and spleen with numerous collateral anastomoses to other venous beds of the abdomen. This result is in agreement with the literature as the radial and tangential permeability of a lobule were estimated to be about 1.5 1014 m2 in Ref46, while Ref11. Contrast flow and enhancement patterns seen on thoracic CT angiography (CTA) can often be challenging and may often reveal more than is immediately apparent. Normal caliber intrahepatic and common bile ducts. As such, it is often described by a power-law model. Hence, if venous visualization is the primary clinical objective, a delayed phase should be obtained in addition to the arterial phase. Normal sequence of enhancement follows right atrium, right ventricle, pulmonary artery, pulmonary vein, left atrium, left ventricle, and aorta. The thinner channels form the canopy of the HA and PV trees and irrigate the lobules which behave like a porous system. The pulmonary artery to ascending aorta transit time (PTT) is a key circulatory parameter that can affect target, as well as non-target vessel opacification on a thoracic CTA. Once the geometrical ratios that characterize the liver vasculature are uncovered, the merit of a dendritic flow architecture over a radial one can be checked. The shape of the liver as a hemisphere of radius R. By the same token, the flow resistance ratio between the dendritic and radial configurations is: where L1 is the channel length corresponding to the first generation number. Their complexity often forces to reduce the hydrodynamic studies of the liver to its morphofunctional unit, the lobule23,24. However these models, regardless their sophistication level14,15, are descriptive. BNP was immediately obtained and was elevated at 23,000, echocardiogram obtained within the next 4h demonstrated a left ventricle EF of 22%, Mixing artifact in the left atrium in a patient with severe mitral regurgitation. 5 this means that 31/3k = 1, or said in other words: The averaged measured channel length ratio is 0.66, 0.72 and 0.66 for respectively HA, PV and HV. Wechsatol W, Lorente S, Bejan A. Optimal tree-shaped networks for fluid flow in a disc-shaped body. 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