Background
Hepatolithiasis is a complicated and challenging disease characterized by formation of stones in the intrahepatic bile duct with the chronic but progressive nature. Incidence and etiology of hepatolithiasis varies dramatically. In east Asia, this prevalent disease is often primary with a reported incidence between 3.1% and 21.2% [
1]. However, in western countries, hepatolithiasis with the incidence of 1% approximately tends to be secondary to cholestasis (e.g. Caroli Disease), biliary stricture (e.g. common bile duct injury) or cholangitis (e.g. primary sclerosing cholangitis or infection). It’s noteworthy that there have been emerging cases of hepatolithiasis in north America since immigrants from epidemic regions of the world increased enormously [
2,
3].
Manifestation of hepatolithiasis ranges from mild chronic abdominal pains to severe refractory cholangitis. Stones, infections, inflammations and strictures promote the exacerbation of the disease mutually, leading to the atrophy in the affected liver segments and compensatory hypertrophy in the uninvolved parts [
4]. This atrophy–hypertrophy complex (AHC) along with changes of anatomic configuration like portal triads may be a thorny issue during surgical intervention. Under extremely rare circumstances, the main liver (Couinaud’s segment II–VIII) can be almost totally atrophic while the caudate lobe (Couinaud’s segment I) has been exceedingly hypertrophic. Subtotal (segment II–VIII) hepatectomy instead of liver transplant has scarcely been reported in the literature to treat bilateral diffuse hepatolithiasis [
5,
6]. The introduction of our experience aims to describe the precise preoperative evaluation and challenging procedure details.
Discussion and conclusions
In 1985, Kumon firstly divided caudate lobe into three parts: Spiegel lobe, paracaval portion and caudate processus [
8]. Caudate lobe is usually referred as a silent liver reserve, accounting for approximately 2% to 3% of the total liver volume (TLV) [
7]. However, our study reported the extremely rare cases with utmost hypertrophy of Spiegel lobe (68.4% of TLV) in case 1 and exceeding hypertrophy of paracaval portion and caudate processus (65.8% of TLV) in case 2. The surgical outcomes of both patients demonstrate the safety and potential effectiveness of subtotal (segment II–VIII) hepatectomy. Less blood loss and shorter operation time was achieved compared with previous reports [
5,
6]. Thus, our limited experience of treating bilateral diffuse hepatolithiasis with hypertrophic caudate lobe may provide a valuable reference for similar thorny cases.
Recognition of the hypertrophic caudate lobe should be the top priority during preoperative evaluation. Otherwise, misdiagnosis will be easily made, for example, the CT images of case 2 is liable to be mistaken for normal right liver and atrophic left liver with hepatolithiasis. Such inaccurate preoperative evaluations will lead to inappropriate operation planning. In that case surgeons will lose the alert to protect the blood supply and bile duct of the caudate lobe. It is practical to identify caudate lobe via thickened short hepatic veins from hypertrophic caudate lobe. On account of complete anatomic variation, it is difficult to make an intuitive judgement according to conventional CT image. In that case, employment of 3D liver reconstruction is beneficial to recognition of caudate lobe hypertrophy, assessment of liver volume and planning of the operation. Via 3D liver reconstruction, it is easy to visualize the configuration of Glisson system and hepatic veins, and to avoid intraoperative injuries to the vasculature of the caudate lobe. In that condition, dysfunction of the remnant liver or even death will occur.
As for the key points during the operation, it is difficult to distinguish the anatomic structure of hepatic hilum due to the severe adhesions and rotation of liver. We advise to apply the intrafascial approach to expose and dissect the branches of hepatic artery, portal vein and bile duct to the caudate lobe. Maneuver must be gentle and meticulous to avoid any injury to the vital blood supply or bile drainage of the caudate lobe. To differentiate the demarcation between hypertrophic caudate lobe and segment II–VIII is another critical issue. Normally, the Spiegel lobe on the left side of IVC is relatively isolated and easier to be distinguished from the peripheral liver segments, but the boundary between the paracaval portion of caudate lobe and the right posterior liver lobe is difficult to be defined. In the reports of Takayama and Midorikawa, by the means of puncturing the right posterior portal vein under the guidance of intraoperative ultrasound, the boundary between caudate lobe and right posterior liver lobe is identified by counterstaining and tattooing techniques [
9,
10]. Kogure et al. have reported that the caudate processus hepatic vein can be used as the demarcation between caudate processus and right posterior lobe, but the boundary between paracaval portion and right posterior lobe is still unclear [
11]. Maki et al. used 3D liver reconstruction to demonstrate that in half of normal people, a small branch from the root of right hepatic vein, named "paracaval vein", can be used as the boundary between paracaval portion and segment VII or VIII [
12]. Interestingly, there is a natural demarcation between atrophic main liver and hypertrophic caudate lobe in case of AHC, which can be served as the reference line of liver parenchyma transection.
As to the choledochojejunostomy, we propose that indications should be as follows: (1) dysfunction of Oddi sphincter; (2) strictures of extrahepatic bile duct. If strictured bile duct has not been resected totally, it is easier to initiate cholangitis and recurrence of hepatolithiasis after choledochojejunostomy.
Since the bile from the caudate lobe flow upward into the hepatic duct or bilioenteric anastomosis, patients are encouraged to take intermittent prone position during sleep to promote the bile drainage and prevent cholestasis.
In conclusion, subtotal (segment II–VIII) hepatectomy under the guidance of 3D liver reconstruction is one of several treatments possible for selected patients with bilateral diffuse hepatolithiasis accompanied by compensatory caudate lobe hypertrophy. Dissecting the porta hepatis carefully and protecting the vessels and bile duct to the caudate lobe is crucial to surgical procedure.
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