Abdominal Sonography Part II Lecture 17 • Abdominal Organ Transplants • Liver • Kidneys • Pancreas Holdorf
A brief Doppler Spectral analysis recap: • Biphasic • Triphasic • Monophasic
Vascular Technology: Doppler has three sounds: monophasic, biphasic and triphasic. These sounds relate to how well the vascular system is functioning. How do the changes in the vascular system cause the different sounds that are produced? Regarding blood flow in peripheral arteries the typical pattern of flow in a resting state is to accelerate quickly then stop and even briefly flow backwards as a pressure wave traveling faster than the blood itself reflects back from the smaller arterioles near the end of the pathway blood follows.
Because the reflected pressure wave stops and even briefly reverses the flow of blood in the artery, two components are heard/seen. That type of pattern is called biphasic and is normal. Also normal is a pattern where the blood goes forward, reverses briefly then forward again (because the large artery leaving the heart - the aorta - has an elastic wall and stretches like a balloon when the heart contracts. A valve at the start of the aorta stops blood from flowing back into the heart. The elastic walls returning to their normal shape propel blood away from the heart throughout the entire heartbeat, not just when the heart is squeezing).
This elastic recoil pushes the blood forward again giving the Doppler noise we hear a third component (triphasic). If the artery being listened to have a severe blockage, the arterioles will open (vasodilation) to allow more flow in an attempt to deliver the amount of blood required by parts of the body downstream. That stops the reflection of the pressure wave giving a flow pattern with only one sound - in a forward direction - which is described as monophasic.
Biphasic and triphasic flow patterns are normal in a resting person. Monophasic flow generally indicates significant peripheral vascular disease. A person can have peripheral vascular disease even if their Doppler waveforms are bi or triphasic but some form of exercise testing may be required to reveal it. This type of testing is best done in an accredited vascular lab.
Ultrasound Examination of Solid-Organ Transplants Indications/Contraindications • Indications for an ultrasound examination of a solid-organ transplant include but are not limited to the following:
A. Liver Transplant 1. Performance of a screening ultrasound examination to establish a baseline after transplantation as per the hospital surveillance protocol 2. Follow-up of abnormal findings on a prior transplant ultrasound examination; 3. Assessment of the transplant in the setting of abnormal liver function tests 4. Evaluation for pain, fever, sepsis, or laboratory abnormalities 5. Evaluation for a possible fluid collection or assessment of drainage catheter output; 6. Assessment of the biliary tree for dilatation, a stricture, Biloma, or an abscess; 7. Evaluation for vascular patency; and 8. Evaluation for malignancy, either recurrent or post-transplant lymphoproliferative disorder
B. Renal Transplant 1. Performance of a screening ultrasound examination to establish a baseline after transplantation as per the hospital surveillance protocol; 2. Follow-up of abnormal findings on a prior transplant ultrasound examination; 3. Evaluation for pain, fever, sepsis, or abnormal laboratory or clinical values (eg, elevated creatinine and low or decreased urine output); 4. Evaluation for vascular patency; 5. Assessment of hematuria or known or suspected hydronephrosis, hydroureter, or bladder abnormality; 6. Evaluation for a possible fluid collection or assessment of drainage catheter output; 7. Evaluation of the transplant in the setting of hypertension or bruit; 8. Evaluation for iatrogenic injury or complications after biopsy of a transplanted kidney; and 9. Evaluation for malignancy, either recurrent or post-transplant lymphoproliferative disorder.
C. Pancreas Transplant 1. Performance of a screening ultrasound examination to establish a baseline after transplantation as per the hospital surveillance protocol; 2. Follow-up of abnormal findings on a prior transplant ultrasound examination. 3. Assessment of graft dysfunction in patients with abnormal laboratory values or clinical parameters (eg, elevated blood glucose); 4. Evaluation for suspected stenosis or thrombosis of the vasculature; 5. Evaluation of pain at or near the surgical site; 6. Evaluation of the response to treatment (eg, immunosuppressive therapy in the setting of rejection); 7. Evaluation for iatrogenic injury or complications after biopsy of a transplanted pancreas; and 8. Assessment of the transplant in the setting of infection or pancreatitis.
An ultrasound examination of the transplanted liver, kidney(s), or pancreas should be performed when there is a valid medical reason.
Orthotopic liver transplantation refers to a procedure in which a failed liver is removed from the patient's body and a healthy donor liver is transplanted into the same location. The procedure is the most common method used to transplant livers.
Liver Donor Requirements Any member of the family, parent, sibling, child, spouse or a volunteer can donate their liver. The criteria for a liver donation include: • Being in good health • Having a blood type that matches or is compatible with the recipient's, although some centers now perform blood group incompatible transplants with special immun -suppression protocols • Having a charitable desire of donation without financial motivation • Being between 18 and 60 years old • Being of similar or bigger size than the recipient • Before one becomes a living donor, the donor must undergo testing to ensure that the individual is physically fit. Sometimes CT scans or MRIs are done to image the liver. In most cases, the work up is done in 2–3 weeks.
Indications for Liver Transplant • Primary or secondary biliary cirrhosis • Chronic active hepatitis with cirrhosis • Liver abscesses • Fatty liver infiltrates • Liver Ca
Liver TransplantComplications Graft rejection • Manifestations of graft rejection are: • Fever • Tachycardia • RUQ or flank pain • Diminished bile flow through t-tube or change in bile color • Increased bilirubin • Increased jaundice
Treatment for Cirrhosis of Liver Injection sclerotherapy: varices are sclerosed TIPS: Transjugular intrahepatic portosystemic shunt – placement of a portal shunt for esophageal varices Surgical bypass shunting procedures: Last resort: Ascites is shunted from the abdominal cavity to the superior vena cava Liver Transplantation
Liver Cancer Risk Factors • Cirrhosis • Metastasis from another site Dx (Patient has a history of…) • AFP: Alpha-fetoprotein tumor marker • Liver enzymes ALP elevated • Liver biopsy: definitive diagnosis
Liver Cancer • HCC- hepatocellular carcinoma most common of liver cancer • Most liver tumors are unrespectable • 5 year survival rate is less than 9%. • Clinical manifestations
Treatment For Liver Cancer • Chemotherapy via an surgically implanted infusion pump • Liver transplantation • Portions of a liver are transplanted and will regenerate • Transplantation surgery- 12 hours • Immunosuppressant drugs • Steroids • Monitor for infection and organ rejection
Vascular Anatomy that matters during Liver transplants • Main hepatic artery • Right and left intrahepatic arteries • Hepatic veins • IVC • Main Portal Vein • Intrahepatic portal veins
Liver Transplant Grayscale, color Doppler, and spectral Doppler examinations of the liver transplant vasculature should be performed. Before the ultrasound examination, the surgical anatomy and reconstructive techniques for that particular patient should be confirmed when this information is available. Comparisons with prior examinations should be made when possible.
Grayscale Evaluation of the Transplanted Liver A complete grayscale examination of the liver should be performed, including long-axis and transverse views. The liver parenchyma should be assessed for focal and/or diffuse abnormalities, and the echogenicity and echo texture of the liver should be noted. The biliary tree should be evaluated and the caliber of the common duct measured when possible. The subphrenic and subhepatic spaces should be investigated for possible fluid collections. Grayscale images of the hepatic vessels, including the portal vein, hepatic veins, and inferior vena cava (IVC), should be obtained.
Doppler Evaluation of the Transplanted Liver The vessels that should be examined include the main hepatic artery and right and left intrahepatic arteries, hepatic veins, IVC, main portal vein, and intrahepatic portal veins. The vascular anastomoses (hepatic arterial, portal venous, hepatic venous, and IVC) should be interrogated.
Hepatic Arteries The hepatic arteries should be interrogated to confirm normal flow and exclude complications such as hepatic artery thrombosis, stenosis, a pseudo -aneurysm, or an arteriovenous fistula. Both the main hepatic artery and the intrahepatic arteries should be evaluated when possible.
Main hepatic artery The main hepatic artery should be imaged along its length when possible. An attempt should be made to interrogate the native artery, region of the anastomosis, and donor artery. A Doppler evaluation should be obtained to demonstrate the presence of flow, configuration of the vessel, and any possible areas of color Doppler aliasing, which may suggest turbulent or high velocity flow. Spectral Doppler waveform morphology should be assessed. Velocity measurements may be obtained at the anastomosis and within the native and donor portions of the hepatic artery and at any areas of color flow aliasing. Doppler indices calculated from spectral Doppler waveforms obtained at these locations may include the peak systolic velocity (PSV), RI (systolic velocity – diastolic velocity/systolic velocity), and AT (time between end diastole and the first systolic peak)
Intrahepatic arteries The presence of flow should be confirmed in the intrahepatic (right and left hepatic) arteries. Resistive indices should be calculated from spectral Doppler waveforms obtained at these locations. Spectral Doppler waveform morphology should be assessed visually. Acceleration times can also be measured if the waveform appears abnormal, as in a tardus parvus waveform. Comparisons with prior examinations should be made when possible. Although the hepatic arterial waveform may change normally with time, some changes in the waveform configuration, RI, or PSV may require further evaluation.
Portal Vein The main portal vein and right and left branches should be scanned in their entirety, including the portal vein anastomosis. Images should document the presence of flow, the direction of flow, and any areas of possible color Doppler aliasing. Spectral Doppler evaluation should include an assessment of the waveform as well as angle-corrected peak velocity measurements proximal to, at, and distal to the main portal vein anastomosis. If there appears to be a discrepancy in velocities within the portal vein, an anastomotic-to-preanastomotic velocity ratio can be performed.
Hepatic Veins and IVC The type of surgical anastomosis (piggyback versus interposition) should be determined before scanning when possible. Color and spectral Doppler tracings should be obtained from the right, middle, and left hepatic veins and the IVC in whole-liver transplants and from the existing hepatic veins and IVC in partial-liver transplants. In the case of a piggyback hepatic venous anastomosis, both the recipient IVC and the piggybacked hepatic vein confluence/donor IVC segment should be interrogated. Flow should be verified and the waveform assessed for the degree of phasicity. Comparisons with prior examinations should be made when possible. Follow-up examinations may be helpful if the initial ultrasound examination shows an abnormal waveform.
The type of surgical anastomosis (piggyback versus interposition)
Orthotopic liver transplantation (OLT) in adult patients has traditionally been performed using conventional caval reconstruction technique (CV) with veno-venous bypass. Recently, the piggyback technique (PB) without veno-venous bypass has begun to be widely used in order to preserve the Cava
Postoperative Doppler evaluation of liver transplants Doppler ultrasound plays an important role in the postoperative management of hepatic transplantation, by enabling early detection and treatment of various vascular complications. Doppler ultrasound is the modality of choice for evaluating post liver transplant patients for vascular complications. Awareness of the normal postoperative Doppler findings and timely identification of various vascular complications is essential for improving outcome of liver transplantation.
Liver transplantation is the only curative treatment for end-stage liver disease. The common indications for liver transplantation include cirrhosis secondary to alcoholic liver disease, hepatitis, hepatocellular carcinoma, non-alcoholic and metabolic diseases, and hepatic failure. Over the last few decades, advancement in surgical techniques and perioperative management has greatly improved the outcomes of liver transplantation. Early detection of vascular complications by postoperative Doppler imaging has played a vital role in decreasing the incidence of graft failure.
The allograft for liver transplantation can be obtained either from a deceased donor or from a living donor after performing a partial hepatectomy. Deceased donor liver transplantation is by far the most prevalent method of transplantation in much of the western world. For example, approximately 300 living donor liver transplants (LDLT) are performed every year in the US compared to 6000 cadaveric donor transplants. In countries where cadaveric organ procurement is difficult, LDLT is more common than cadaveric donor transplants. Although the preoperative workup and technique of cadaveric donor and LDLT are different, the principles of postoperative Doppler imaging, performed to evaluate the vascular patency, are similar.
During liver transplantation surgery, inferior vena cava (IVC) anastomosis is followed by portal venous, arterial, and biliary anastomoses. For deceased donors, IVC anastomosis can be performed using the 'standard' or 'piggyback' techniques. In the standard technique, the recipient liver is removed along with the IVC. End-to-end anastomoses, between the donor and recipient IVCs, are performed above and below the allograft. In the piggyback technique, the donor hepatic venous confluence is anastomosed with the recipient IVC. Piggyback anastomosis helps maintain hemodynamic stability during surgery. The piggyback technique is used for all LDLTs.
Vascular complications are a common cause for allograft failure after hepatic transplantation. Early detection and treatment of vascular complications help reduce the incidence of graft failure. Doppler ultrasound is a noninvasive test that allows real time dynamic evaluation of the allograft vasculature and is extensively used in the postoperative evaluation of allografts.
Gray-scale ultrasound of the right upper quadrant precedes Doppler interrogation of the allograft vasculature. Along with evaluation of the hepatic parenchyma, attention is paid to the presence any peri-hepatic fluid collection. Peri-hepatic fluid collections may represent postoperative hematomas, seromas or bilomas. Superinfection of any fluid collection can cause abscess formation. Pneumobilia can be present in patients with an anastomosis. Presence of biliary dilation may indicate development of biliary stenosis. Doppler examination of the liver transplant involves interrogation of the main hepatic artery and its intrahepatic branches, main portal vein and its branches, hepatic veins, and the IVC.
The first post-transplant Doppler examination is often performed within the first 24 hours of surgery, with follow-up exams, as clinically indicated. The main, right, and left hepatic arteries are evaluated and should have a similar appearance. When examining the hepatic arterial waveform, attention is directed to the systolic upstroke, peak systolic velocity, and resistive index (RI)