Endohepatology, Present and Future Directions, by Peter Canine and Marvin Yu. Endohepatology refers to the application of endoscopic techniques, particularly endoscopic ultrasound, to the diagnosis and treatment of patients with liver disease. The past few decades have seen a rapid growth in available methods of endoscopically evaluating the liver and managing the sequelae of advanced chronic liver disease. At this time, there are a wide variety of available procedures within the field of endohepatology which can be performed within the same session as a one-stop shop, and many more are on the horizon. This video will highlight the currently available procedures, as well as future directions and novel techniques. EOS-guided liver biopsy is technically straightforward and has an excellent safety record. Given the transducer's proximity to the liver and Doppler interrogation, optimal parenchymal samples can be obtained while avoiding intervening vasculature and bile ducts. Recent randomized controlled trials have shown EOS liver biopsy to be equivalent, if not superior, to traditional precutaneous methods in terms of yield and safety. Direct portosystemic pressure gradient measurements can now be performed using an FDA-approved 25-gauge device. The procedure entails sequential measurement of the hepatic venous system followed by the portal venous system. For each vascular target, heparinized saline is injected, causing the pressure readings to rise and eventually plateau, and the mean value is obtained. The portosystemic pressure gradient measurement is the difference between the mean portal and mean hepatic vein measurements. No longer do we require a wedged hepatic vein pressure to serve as a proxy or estimate of the portal vein pressure. It can now be directly ascertained. Consequently, there is less inter-observer variability and more accurate measurements, particularly in presinusoidal causes of portal hypertension. For therapeutic endohepatology, a recent addition is EOS-guided coil-based injection therapies. EOS coiling is possible even in the setting of massive hemorrhage, which typically precludes traditional endoscopic therapies. With EOS, the gastric variceal target is well visualized and needle access is precise. In this case, the largest axial diameter of the vessels is 10 mm and the variceal nest measures roughly 4 cm. EOS also allows for injection of discrete hemostatic coils. After the needle is advanced, coils are deployed, usually in multiples. These soft coils cause thrombosis by mechanical packing as well as by initiating the coagulation cascade. Doppler is able to provide real-time information regarding hemostasis. The available literature supports EOS-guided therapy over traditional direct endoscopic injection in terms of superior acute hemostasis, lower re-bleeding, and increased safety. Head-to-head studies with BRTO are currently being planned. The following endohepatology procedures are currently in the pipeline and are likely to be added soon to the armamentarium, representing the future of the field. EOS liver indentation is a simple and quick diagnostic technique that replicates the physical exam maneuver of liver palpation. The EOS platform is able to measure the degree of maximal indentation with sonographic calipers. A recent pilot study in patients with Masold demonstrated that degree of indentation correlates well with fibrosis levels on biopsy and reliably screens for cirrhosis. For normal liver, F0-1, the indentation is approximately 5-6 mm. In contrast, for F4 disease or cirrhosis, the indentation is less than 3.5 mm. Shear wave elastography is available on the newer EOS platforms and measures elastography or tissue stiffness for a two-dimensional swath of tissue. Shear wave elastography is now able to be performed rapidly. Here are serial shear wave measurements in a patient with normal liver, consistently less than 8 kPa. Here are shear wave measurements in a patient with cirrhosis, consistently greater than 15 kPa. Because the difference between the transducer and liver surface is reproducibly less than 1 cm, regardless of body habitus, EOS shear wave elastography has been shown to be more accurate than traditional manual transabdominal methods, including FibroScan, particularly in obese patients. Future endohepatology procedures may include therapeutic procedures like TIPS. Here is a demonstration of an intrahepatic portosystemic shunt procedure in a preclinical model. The hepatic vein and portal vein are identified in series. Next, a needle is advanced through the hepatic vein into the portal vein. A guide wire is advanced and the needle withdrawn. After balloon dilation of the access tract, a lumen-opposing metal stent is deployed to span both vascular targets. Doppler confirms flow. The field of endohepatology offers a wide variety of diagnostic and therapeutic procedures for patients with liver disease, which have an excellent safety and utility profile. These can be combined into a single endoscopic session, and the list of available procedures continues to grow.

Endohepatology

Endoscopic Ultrasound

Liver Biopsies

Portosystemic Pressure

EUS Techniques