EXPERIMENTAL AND CLINICAL TRANSPLANTATION

Abstract
Piggyback syndrome is a rare complication of orthotopic liver transplant performed via the piggyback technique. Where conventional orthotopic liver transplant involves anastomosis of both the donor and recipient inferior vena cava, piggyback orthotopic liver transplant instead involves anastomosis between the donor inferior vena cava and recipient hepatic veins. Piggyback syndrome is hepatic vein outflow obstruction as a result of anastomotic stenosis after piggyback orthotopic liver transplant. We present a case of piggyback syndrome successfully treated with percutaneous stenting and balloon angioplasty and discuss the etiology, diagnosis, and treatment of this syndrome.

Key words : Ascites, Balloon angioplasty, Hepatic venous outflow obstruction, Inferior vena cava, Stenosis

Introduction
Piggyback syndrome is a rare complication of orthotopic liver transplant (OLT) performed via the piggyback technique. Where conventional OLT involves anastomosis of both the donor and recipient inferior vena cava (IVC), piggyback OLT instead involves anastomosis between the donor IVC and recipient hepatic veins. People with piggyback syndrome experience the sequelae of hepatic vein outflow obstruction arising from anastomotic stenosis following piggyback OLT. We present a case of piggyback syndrome successfully treated with percutaneous stenting and balloon angioplasty and discuss the etiology, diagnosis, and treatment of the syndrome.

Case Report
Our patient, a 46-year-old man with alcohol use disorder, initially presented to an outside hospital with a 1-month history of worsening jaundice and abdominal distention. He was found to have acute-on-chronic liver failure secondary to alcohol-associated cirrhosis and was transferred to our institution for liver transplant evaluation. On arrival, his sodium Model for End-Stage Liver Disease score was 38. He was listed for liver transplant and received an offer during the same admission. He successfully underwent deceased donor liver transplant via the piggyback technique. Postoperative Doppler scans revealed normal-appearing transplant vasculature. The patient was discharged to physical therapy rehabilitation and then subsequently to home with stable liver function.
Five months later, the patient began developing progressive abdominal distention and lower extremity edema. Magnetic resonance imaging of the abdomen revealed new hepatomegaly and large-volume ascites without suspicious liver lesions or biliary ductal dilation. He underwent therapeutic and diagnostic paracentesis, which was consistent with transudative ascites. Doppler ultrasonography of the hepatic vasculature showed decreased cardiac phasicity in the right and middle hepatic vein anastomoses with elevated hepatic vein pressure gradient of 26 mm Hg, suggestive of stenosis. Transjugular liver biopsy revealed sinusoidal dilatation consistent with hepatic venous outflow obstruction. No findings of acute cellular rejection were seen on liver biopsy.
The patient subsequently was seen by interventional radiology for hepatic venogram and intervention. Venogram revealed moderate to severe stenosis of the middle hepatic vein. An uncovered 20 mm × 60-mm stent was deployed across the stenotic area extending from the middle hepatic vein anastomosis to the IVC. Balloon venoplasty of the stent was then performed with 14-mm, 16-mm, and 18-mm balloon catheters. A venogram after the procedure demonstrated substantial improvement of the stenotic area and patency of the piggyback anastomosis.
The patient remained without ascites and with normal liver-associated enzymes at 1-, 2-, 3-, and 6-month follow-up appointments.

Discussion
Conventional OLT was first described in 1963 by Starzl and colleagues and involved end-to-end anastomosis of the donor and recipient retrohepatic IVC.¹ This technique required intraoperative clamping of the recipient IVC to facilitate formation of the anastomosis. This maneuver was often associated with substantial decreases in cardiac preload and subsequent hemodynamic instability. Veno-venous bypass addressed the issue of decreased cardiac venous return but at the cost of increasing procedural complexity.
The piggyback technique was first described by Caine and colleagues in 1968 and further improved on the conventional technique by preserving the recipient’s IVC.² Instead, anastomoses are formed between the donor IVC and the recipient hepatic veins. This technique preserves cardiac venous return throughout the procedure with fewer hemodynamic disruptions and without the need for veno-venous bypass.
Anastomotic strictures are a rare complication of piggyback OLT, estimated to have an incidence of 0.8% to 1%.³ Multiple etiologies for these strictures have been proposed, including vessel size discrepancy and graft torsion. In adult patients who receive adult donor livers, a vessel size discrepancy substantial enough to cause anastomotic stricture is unlikely. Risk for graft torsion increases with reduced-size liver grafts. In the absence of peritoneal attachments, small grafts are more prone to rotate within the subphrenic space and result in kinking of anastomoses. In one case, graft torsion leading to outflow obstruction was attributed to liver allograft segmental hypoperfusion and atrophy resulting in excessive rotation of the organ.
A recent paper by Ye and colleagues also evaluated recipient hepatic drainage pattern as a risk factor for hepatic vein occlusion following piggyback OLT.⁴ Patients were divided into 3 groups based on patterns of hepatic vein drainage into the IVC as determined by preoperative 3-dimensional reconstruction: left and middle hepatic veins forming common trunk before IVC, right and middle hepatic veins forming common trunk before IVC, and finally left, middle, and right hepatic veins forming common trunk before IVC. After anastomosis formation, the angle between the anastomosis and IVC was measured, as well as the length of reconstructed outflow. A larger angle between anastomosis and IVC was found to be associated with significantly increased odds of anastomosis twisting. Furthermore, larger ratios between lengths of reconstructed outflow and anastomosis-IVC angle were found to be associated with significantly increased odds for anastomosis compression.
Prompt recognition of symptoms suggestive of hepatic venous outflow obstruction is paramount to guide subsequent diagnostic testing and appropriate treatment. Initial symptoms may be acute to subacute and can be consistent with the presentation of Budd-Chiari syndrome: ascites, hepatomegaly, splenomegaly, and lower extremity edema, which were all shown in our patient. Liver function can also be affected. Duplex ultrasonography is a noninvasive, specific, and sensitive tool to evaluate the hepatic vasculature and anastomoses.⁵
Monophasic flow in the hepatic veins and elevated flow velocity through the anastomosis are suggestive of stenosis. Hepatic venography remains the gold standard for diagnosis, as this study tool can accurately identify location and severity of obstruction, at the cost of being an invasive test. Percutaneous stenting and balloon angioplasty are minimally invasive, safe, and effective techniques to alleviate anastomotic strictures.⁶ In cases where percutaneous intervention is unsuccessful, surgical intervention may be pursued via excision and reanastomosis, retransplant, or cavo-atrial shunt via vascular graft.

Volume: 23 Issue: 2 February 2025

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