Imaging helps avoid pitfalls and detect biliary, vascular, and gastric problems early in organ transplantation Imaging plays an increasingly important role in demonstrating the diverse range of complications in living donors after partial liver resection. To ensure the safety of donors, meticulous radiological surveillance is mandatory, especially during the early postoperative period, according to a Korean study presented at the 2007 Radiological Society of North America meeting held in Chicago.
Imaging helps avoid pitfalls and detect biliary, vascular, and gastric problems early in organ transplantationImaging plays an increasingly important role in demonstrating the diverse range of complications in living donors after partial liver resection. To ensure the safety of donors, meticulous radiological surveillance is mandatory, especially during the early postoperative period, according to a Korean study presented at the 2007 Radiological Society of North America meeting held in Chicago.
A shortage of cadaveric donors means that living donor liver transplantation (LDLT) is now widely accepted as an alternative method for patients with end-stage liver disease.
"In many Asian countries, cadaveric organ harvesting is limited, and this is the only realistic option to overcome the organ shortage," said Dr. Heon-Ju Kwon of the radiology department at the University of Ulsan Asan Medical Center in Seoul. "The overwhelming benefits of LDLT for critically ill patients should not undermine concern for the safety of healthy living donors."
Kwon presented details about a large survey of five Asian centers. The overall donor complication rate at the centers was about 15%, with a further operation required in 1.1% of cases. The complication rate was higher in right-lobe (28%) donors than in left-lateral-segment (9.3%) or left-lobe (7.5%) donors. Right-lobe donors also had more serious complications, including cholestasis (7.3%), bile leakage (6.1%), biliary stricture (1.1%), portal vein thrombosis (0.5%), intra-abdominal bleeding (0.5%), and pulmonary embolism (0.5%). No hospital mortality was noted in this survey.
Sufficient graft volume is essential for a successful LDLT outcome. A graft-to-recipient weight ratio of 1% appears to be a safe limit for adult recipients, regardless of the cause of disease, according to Kwon. The right lobe accounts for around two-thirds of the entire liver volume and usually meets the graft-to-recipient weight ratio requirement. In a donor with a large left hepatic lobe and/or for a small recipient, the left lobe graft can be used. The left lateral segment is used as a graft for a pediatric recipient.
Patients with normal liver function can tolerate resection up to 60%, but to minimize morbidity and ensure donor safety, the limit for living liver donors should be 40% of total hepatic volume. A remnant liver volume of 27% represents the lowest limit. Given the need for a safety margin, 30% remnant volume is probably the lowest practical limit.
An accurate preoperative volumetry in potential donors for LDLT is of utmost importance to estimate graft and remnant liver volumes and avoid postoperative hepatic dysfunction in donors and recipients, Kwon said. Liver volume can be estimated successfully, by both manual and automated methods, using CT.
Bleeding is a major risk in liver resection, and harvesting of hemilivers is associated with a significantly larger resection plane, which increases the amount of blood loss. Although hemostasis is usually performed in donors after harvesting of hemilivers, arterial spasm may obscure the foci of bleeding intraoperatively.
In one case at the Asan Medical Center, massive bleeding occurred after right hemiliver donation, and the hemoclip was dislodged as well. Multislice CT showed acute hematoma in the perihepatic space and active extravasation of contrast agent from the right hepatic arterial stump during the arterial phase. Close scrutiny of the arterial stump is vital in the evaluation of postoperative CT in living liver donors.
Right adrenal hemorrhage following a hepatectomy is another well-known condition. Mobilization of liver segments close to the inferior vena cava may choke off or cause trauma to the right adrenal vein, resulting in venous congestion and hemorrhagic infarction of the gland. Stress may also contribute in adults. Although a hemorrhagic adrenal gland may rupture and produce severe bleeding, necessitating another operation, postoperative adrenal hematoma is considered self-limited in most cases, Kwon said. CT usually allows an accurate diagnosis by demonstrating both the size and density of the gland. Most adrenal hemorrhages are centrally hypoattenuating, with higher peripheral attenuation.
Biliary complications such as bile leakage and bile duct stricture are frequent and sometimes serious, and can result in a deterioration of liver function, abscess, and even sepsis if an appropriate pathway for biliary diversion is not provided at an early stage.
Postoperative bile leakage may occur in the parenchymal transection surface of the liver, repair site of the hepatic duct, and caudate branches in the hilar plate. However, biliary variants can be assessed precisely using CT or MR cholangiography and intraoperative direct cholangiography. Postoperative bile leakage is clinically suspected when bile-colored fluid persists in the drain catheters and CT shows no remarkable abnormal findings other than usual postoperative fluid collection in the surgical bed.
On a hepatobiliary scan, radioisotopes accumulate in the perihepatic space during the excretory and late phases. Usually, bile leakage can be successfully managed by biliary diversion, but biliary leaks may cause biloma or bile peritonitis, which need radiological or surgical intervention.
Bile duct stricture is often related to excessive dissection of the bile duct in the porta hepatis. MR cholangiography can usually demonstrate the location and strength of the stricture segment. Unlike those in recipients, postoperative bile duct strictures in donors are usually improved by interventional management.
Although rare, portal vein thrombosis or stenosis may occur in donors after hemiliver resection. Portal vein complications tend to occur in donors with a portal vein variation. In these donors, surgeons may transect the right anterior and posterior portal veins en bloc from the main portal vein, possibly resulting in disturbance of portal vein flow.
Doppler ultrasound is a primary screening method for detection of postoperative vascular complications, but extensive bowel gas or extrahepatic fluid collection and hematomas can pose problems, Kwon said. Multislice CT can provide excellent visualization of filling defects within the portal vein or focal narrowing, which usually occurs at the junction between the left portal vein and main portal vein.
If a donor complains of upper gastrointestinal obstruction symptoms after the procedure, gastric volvulus should be suspected. As the volume of the remaining liver in the donor gradually expands, and the dead space disappears by degrees, the recurrence of gastric volvulus is decreased.
Adhesion is commonly seen in patients who have undergone laparotomy, including hepatectomy, but only a few cases produce symptoms.Incisional hernia is a frequent complication of laparotomy; most develop during the first four months after surgery, but they may remain clinically silent for up to five years. They can be diagnosed precisely on MSCT by demonstrating abdominal wall defects and the hernial contents, as well as signs of bowel ischemia, if present.
Finally, severe pulmonary embolism due to deep vein thrombosis is a rare complication for donors. Diagnosis of acute PE on contrast-enhanced CT is based on the presence of partial or complete filling defects. "Some complications may become fatal if the diagnosis and treatment are delayed. Early detection is of utmost importance," Kwon said.
-By Philip Ward