A wide spectrum of biliary complications particularly biliary stricture has been seen in post-LDLT recipients. Thus, there is a need for a non-invasive technique that can be used as a screening method in this group. With advances in the imaging technique, MRCP has become a robust, non-invasive potential imaging modality to diagnose biliary strictures [16]. Furthermore, because a contrast medium is not necessary, MRCP presents the biliary tree in its physiologic state. Owing to the inherent contrast provided by the biliary fluid, the bile ducts are visible above and below stenotic site [12].
Superposition of extrahepatic fluid may be a problem during image analysis, especially in patients with frequent bilomas and abdominal fluid collection at the site of the biliary anastomosis. This occurred once in our study; in addition, the main disadvantage of MRCP is its lack of therapeutic ability. So, our study shows that MRCP is an accurate and valuable imaging technique for the assessment of post-liver transplant biliary strictures. In our center, MRCP is performed almost routinely in transplant recipients with abnormal liver enzyme tests or dilated intrahepatic bile ducts (detected by US) to rule out/confirm and to locate biliary strictures.
In the present study, the mean time interval between liver transplantation and presentation with biliary stricture was 7.4 months. This was similar to the mean time interval being 7.1 months in the study performed by Garg et al. [16].
Kyoden et al. [17] reported that the high rate of stricture formation is referred to the surgical techniques which can injure the bile ducts. However, our study showed only one case of intraoperative difficulty of bile duct anastomosis with suture slippage and re-anastomosis.
Within our studied cases, from 30 recipients with duct-to-duct anastomosis, 28 recipients developed anastomotic biliary strictures, while only two showed non-anastomotic (intrahepatic) strictures, which is in agreement with the study carried out by Shah et al. [18] who reported that duct-to-duct biliary reconstruction has a higher risk of anastomotic stricture formation than biliary-enteric reconstruction.
According to our results, MRCP showed 28 recipients (87.5%) were diagnosed to have anastomotic biliary strictures, two (6.3%) had non-anastomotic (Intrahepatic) stricture, and two (6.3%) had both biliary strictures (mixed). Also, during our study, nine recipients (28.1%) had a suggestion of biliary leak with two of them presenting later with postcholangitic hepatic abscesses and two (6.3%) had filling defects in the biliary tree suggesting the presence of stones. A similar finding was drawn by Garg et al. [16], as in the MRCP study of 34 post-living donor liver transplant recipients reported that 23 recipients (67.6%) had anastomotic biliary strictures, nine recipients (26.5%) had a suggestion of biliary leak, and four recipients (11.8%) had filling defects in the biliary system suggestive of stones or sludge. In three cases, of the total 34 cases, the presence of cholangitis or postcholangitic abscesses was seen in the liver allograft on MRCP.
Our two recipients (6.3%) with non-anastomotic (intrahepatic) biliary strictures were found to have vascular complications in the form of hepatic artery stenosis and steal phenomenon from the hepatic artery to the gasteroduodenal artery, in addition to one case which was diagnosed before transplantation as primary sclerosing cholangitis, compared with studies carried out by Kochhar et al. [15] and Villa and Harrison [5] who reported that ischemia has been shown to be responsible for the occurrence of non-anastomotic biliary stricture (NAS). Besides ischemia, an immunological cause has also been proposed due to the observation of an increased incidence of NAS in patients with autoimmune hepatitis or primary sclerosing cholangitis.
Our studied recipients with biliary strictures were classified by MRCP into four grades according to the degree of biliary stenosis and subsequent intrahepatic biliary dilatation as the majority of cases presented with a mild degree of biliary stricture (59.4%), while minimal, moderate, and severe strictures were found to be 21.8%, 15.6%, 3.1% respectively.
Once biliary stricture was diagnosed, the type, number, and degree of strictures were recorded to plan the management. Also, the size discrepancy as well as angulation between donor and recipient bile ducts should be noted [19].
Williams and Draganov [7] showed that the endoscopic therapy is currently the first-line approach to the treatment of post-transplant biliary strictures. ERCP is a widely available and effective procedure and it has relatively limited complications in comparison with surgical intervention which is in agreement with our study as 20 out of 24 managed recipients had undergone endoscopic therapy (by ERCP), compared to only four recipients by surgical intervention (biliary-enteric reconstruction).
In our study, satisfactory improvement of the biliary strictures was noted in about 80% of managed recipients (16 out of 20) by endoscopic therapy, compared with the study carried out by Hsieh et al. [20] who reported that the endoscopic techniques for post-transplant anastomotic biliary strictures attained sustained patency of the biliary anastomoses in about 84.2% of patients (32 out of 38).
Wadhawan and Kumar [19] showed that multiple duct anastomoses and details of each anastomosis should be taken into consideration, as it has implications on the number of stents to be placed. Also, in the case of a single duct anastomosis, the possibility of stricture extending intrahepatically is to be considered as this can convert a single duct anastomosis similar to double duct thus mandating more than one stent. Within our studied cases, two recipients had undergone two CBD stent insertions by ERCP as MRCP diagnosed one of them with complex biliary strictures, anterior bile duct anastomotic kink (minimal degree), and posterior bile duct intrahepatic stricture (moderate degree) with recurrence of stricture about 6 months after stent removal which was defined as biochemical derangement and recurrence of intrahepatic biliary dilatation, shifting management to surgical intervention, which is in agreement with the study carried out by Villa and Harrison [5] who reported that post-transplant cases with narrow or complex anastomotic strictures or stricture extended within the small intrahepatic biliary tree, ERCP guided therapy may fail, and surgical intervention may be required for rescue therapy.
In the present study, two recipients with non-anastomotic (intrahepatic) strictures were managed by endoscopic therapy, one by balloon dilatation only with no improvement of the distal intrahepatic biliary dilatation and the other by balloon dilatation followed by stent insertion with relief of the stricture. Also, within our studied cases, two with mixed (anastomotic and intrahepatic) biliary strictures, as one was managed by ERCP with two stent insertions, its follow-up revealed no improvement in biochemical derangement or intrahepatic biliary dilatation, while the other case managed by biliary-enteric reconstruction revealed good improvement with MRCP follow-up.
Our eight cases with MRCP diagnosis of minimal anastomotic biliary stricture (21.8%) were exposed only for long-term follow-up without management as only one revealed progress of stricture to mild and then moderate degree with no clinical or biochemical improvement.
The present study and the previous studies show that MRCP is an accurate and useful imaging procedure for the assessment of biliary strictures following living donor liver transplant. The limitation of the present study lies in being a relatively small number of cases examined. In our study, post-LDLT recipients with clinical suspicion of biliary strictures had undergone MRCP to confirm the presence of stricture and record its type and degree, consequently enabling the clinicians with less effort to define the best management plan with better results and limiting the occurrence of post-management complications.