Children with portal vein thrombosis — a condition with often unknown cause in which a clot develops in the vein that drains blood from the intestine into the liver, leading to complications such as portal hypertension, fluid accumulation in the abdomen, and elevated ammonia levels that can affect brain function — are often treated with a liver transplant, but the University of Colorado Department of Surgery is one of a handful of centers in the country that offers a different treatment option. Known as a mesenteric-Rex bypass, the operation uses one of the body’s two jugular veins to create a bypass between the mesenteric vein and the portal vein inside the liver, beyond the clot.
“It's very effective because the children are able to have resolution of their GI bleeding symptoms. They're able to develop normally,” says Jon Merola, MD, PhD, assistant professor in the Division of Transplant Surgery. “Their spleen size goes down, and you're using their native vein, so it saves them a transplant, which was one of the solutions that was used previously.”
Specialized training
Merola, a new hire in the CU Anschutz Department of Surgery, is trained to do the procedure, as is Megan Adams, MD, associate professor of transplant surgery.
“We both got additional training from pediatric hepatobiliary surgeons who have a lot of experience with this,” Merola says. “We're excited to grow the program here and offer it for children who have a portal vein clot or portal hypertension without significant liver disease that would otherwise require transplant.”
The open operation usually requires the patient to recover in the hospital for five to seven days and to take blood thinners for three to six months to keep the connections on either end of the bypass open.
Portal vein thrombosis can often go undetected until the child presents with bleeding in the lower esophagus and upper stomach, Merola says. An endoscopy is used to find enlarged vessels, then a CAT scan will identify the clot in the portal vein. Though the condition is often present at birth, it is often not detected in children until they are school age — between 6 and 12 years old
“That’s because the body has formed vessels around that clot, and that takes time to develop,” he says. “You may have the clot for a while, but it will go undetected until you develop these collateral vessels that are prone to bleeding. Sometimes the spleen can become enlarged, so your white blood cell and platelet counts can drop because the cells aren't being properly filtered. Sometimes on routine blood work, patients will present with abnormal labs, and the clot will be discovered that way as well.”
Journey to transplant
Merola, whose father is a primary care doctor, thought he would go into primary care as well. But his career goals changed during his second year of medical school, when he was invited to observe a liver transplant on a young woman who had a drug allergy that led to liver failure.
“She was on death's door, and a week after the operation, she walked out of the hospital looking totally normal,” Merola recalls. “That showed me the resilience of pediatric transplant recipients and how you can totally change the trajectory of somebody's life with one operation. That got me interested in pediatric transplant, and I chose my residency and fellowship based on places that had surgeons who were really experienced with some of these nuanced techniques.”
Improving organs for transplant
Merola did his residency at Yale, followed by a pediatric transplant surgery fellowship at Columbia University, where he trained in the mesenteric-Rex bypass and other advanced procedures. He comes to CU from Cincinnati Children’s Hospital Medical Center, bringing with him a research lab investigating ways to improve donated organs prior to transplant.
“If you go up to the transplant ward, either at the adult hospital or at the pediatric hospital, everybody is suffering as a consequence of too much immunosuppression, where they develop infections or bad side effects from the medicines that they need, or too little immunosuppression, and they develop a rejection,” he says. “Historically, the way we've dealt with that is trial and error. Everybody gets put on a protocol, and then we adjust accordingly.
“But in the past few years, perfusion technology has become much more mainstream,” he says. “The thought is, rather than expose the recipient to all of these toxic medications, can we modify the organ before it's implanted, while it's maintained on a perfusion pump? There are proteins that the immune system recognizes that trigger rejection, so can we genetically modify the organ, to make it more immunologically compatible while that organ is out of the body, and avoid or at least minimize the amount of immunosuppression that's needed after the transplant?”
Split technique
Merola also is part of an effort at the CU Anschutz Division of Transplant Surgery to split donated livers so that part of the organ goes to an adult recipient and a smaller part goes to a child in need of a liver.
“We're working on new partnerships with the organ procurement bank here to be able to split a liver inside somebody who's passed away, so that both sides can be utilized for two recipients,” he says. “The anatomy can vary person to person, so you need to review the imaging and plan things out so that both portions of the liver can be successfully transplanted. Being able to offer that has significantly shortened the waiting times for children on the wait list nationally.
“When a child is on the wait list, there is a lot of unspoken suffering that isn't captured in statistics, but you can see it in the clinic,” he says. “Sometimes children get brought into the hospital for a feeding tube because they are malnourished or accumulate fluid that limits their activity. Liver disease has a tremendous impact on their quality of life, so the shorter amount of time you can keep them on the wait list, the better. These diseases are never their fault — they're born with this — so being able to restore health is a huge privilege and is really meaningful, not only for myself, but for the whole transplant team that we assemble around them.”
