Acalculous cholecystitis is a common extrahepatic manifestation of hepatitis E and suggests a more serious condition

Hepatitis E (HE) is a disease mediated by the hepatitis E virus (HEV) that is transmitted mainly through the digestive tract. Most people infected with HEV are asymptomatic or self-limiting, with a mortality rate of up to 3% in young people [1] and 30% in pregnant women [2]. HE virions are quasi-enveloped or non-enveloped, 27–34 nm in diameter, with a single capsid protein, which belongs to the species Paslahepevirus balayani, genus Paslahepevirus and family Hepeviridae [3], and contains four open reading frames (ORFs). ORF1 encodes non-structural proteins for replication, including methyltransferase, ribonucleic acid (RNA) helicase, RNA polymerase and papain-like cysteine protease. ORF2 encodes the capsid protein, that is used for vaccine preparation. ORF3 partially overlaps with ORF2 and encodes a multifunctional protein that may be involved in viral secretion [4]. Recently, a new ORF4 was discovered in genotype 1, which may mediate the interaction of the virus with the host protein to participate in its replication [5]. To date, eight genotypes have been identified [6, 7]. Genotypes 1 and 2 infect only humans and are transmitted primarily in developing countries through the fecal–oral route via contaminated water and food [8]. Genotypes 3 and 4 can infect pigs, deer, and other zoonoses and can be transmitted through contaminated water and food, contact with infected animals, and transfusions of contaminated blood products [9]. Genotypes 5 and 6 have been found in wild animals in Japan. Genotypes 7 and 8 have been detected in camels from the Middle East and China, respectively.

Acalculous cholecystitis refers to inflammation of the gallbladder without gallstones, which is usually caused by mechanical factors, chemical materials, or infection [10]. Acalculous acute cholecystitis is identified in approximately 5–10% of patients with acute cholecystitis. Unlike calculous cholecystitis, acalculous cholecystitis is the most frequent complication in critically ill patients, with an incidence ranging from 0.5 to 18%. Acalculous cholecystitis can occur in conjunction with multiple organ failure, and its occurrence often indicates multisystemic failure [11]. Although it was reported in 1987 that acalculous cholecystitis may be an extrahepatic complication of liver disease [12], viral hepatitis-related acalculous cholecystitis is mostly reported in relation to hepatitis A virus (HAV) [13‐20] with few reports in hepatitis B virus (HBV) [21] and C [22‐24]. Metabolites of the virus may invade the wall of the gallbladder or biliary epithelial cells, leading to cholestasis, which in turn results in acalculous cholecystitis [10, 25]. The extrahepatic manifestations of HE reported to date mainly include acute pancreatitis [26], neurological diseases [27, 28], kidney injury [29], and hematologic disorders [30, 31]. HE-related cholecystitis was not reported in a study from Qatar until 2009; however, there were only two cases [32]. Subsequent reports of HE related cholecystitis were also case reports [25], two of which were coinfected with HAV [33] and Salmonella typhi [34] making it difficult to reveal the significance and mechanism of cholecystitis in HE.

Therefore, we retrospectively investigated 114 patients diagnosed with acute HE to demonstrate the significance of acalculous cholecystitis in acute HE.

Viral hepatitis is a group of diseases characterized by hepatocyte damage caused by a hepatitis virus infection, that mediates inflammation. However, hepatitis viruses can also spread to other tissues and cells; for example, HBV can infect the kidneys and cause hepatitis B related nephropathy, HEV can spread to the central nervous system and cause Guillain–Barre syndrome [37]. Cholecystitis, a common extrahepatic manifestation of liver disease, has been reported more frequently in hepatitis A; however, only a few cases have been reported in HE. First, we retrospectively analyzed 114 patients with acute HE who did not have gallstones or undergo cholecystectomy or gallbladder imaging to determine the exact incidence of cholecystitis. Surprisingly, this study found that 57.89% of patients with sporadic acute HE had signs of acute acalculous cholecystitis, indicating that cholecystitis is very common in acute HE. However, the strains infected in all the PCR-positive cases in this study were confirmed to be genotype 4 by sequencing. Ken Fujioka et al. reported a case of cholecystitis secondary to genotype 1 HEV infection in 2016 [25]. In 2020, ER et al. also reported a case report of overlapping HAV and HEV infection with cholecystitis, but only serological results were available without genotype data [33]. Therefore, whether acalculous cholecystitis is specific to genotype 4 HEV infection or similar manifestations are present in other genotypes requires further investigation.

It has been previously reported that HBV and HAV can cause acalculous cholecystitis. Therefore, we compared the incidence of cholecystitis caused by HEV infection alone and coinfected with HBV and/or HAV. There was no difference in the incidence of cholecystitis between the HEV-alone and HBV superinfection and/or HAV groups. The multivariate analysis showed similar results. These results suggest that acalculous cholecystitis is an inherent phenomenon of acute HE. However, the mechanism of acalculous cholecystitis in patients with hepatitis E remains unclear. Based on previous and the present study, we speculate that there may be some possible mechanisms as follows. Since evidence of HEV replication has been reported in bile duct epithelial cells in animal models [38], so whether gallbladder inflammation is caused by HEV directly or by immune responses against HEV in human needs to be further verified. In addition, when HEV causes inflammation of hepatocytes, the bile secreted by the hepatocytes may contain elevated inflammatory cytokines. And when the bile containing increased inflammatory cytokines flow through the gallbladder, it may stimulate thickening and edema of the gallbladder wall [39]. Furthermore, it has been shown that bacterial translocation can occur in various acute and chronic liver diseases [40], and also bacterial infection is one of the important mechanisms of acalculous cholecystitis. The present study showed that the proportion of patients with spontaneous peritonitis in the presence of cholecystitis was also significantly higher than that in patients without cholecystitis. Therefore, whether bacterial translocation is involved in the development of cholecystitis in patients with hepatitis E requires further investigation.

To obtain more information on the mechanisms and their clinical meaning, we further analyzed the clinical outcomes and biochemical parameters between the two groups of patients with and without cholecystitis. Since bile is synthesized and secreted by hepatocytes and excreted through the biliary tract, we initially wondered whether cholecystitis was due to more severe hepatocyte damage, leading to metabolite changes in bile and cholestasis. However, there was no significant difference between the two groups in the levels of ALT, AST, ALP, GGT, and LDH, which reflect hepatocyte damage and cholestasis. Interestingly, the indicators that reflected the anabolic capacity of the liver, such as ALB, CHE, TB, and PTA were significantly lower than those in the group without cholecystitis. Multivariate analysis showed that ALB and TB were the two major risk factors for the occurrence of acalculous cholecystitis. However, the causality between acalculous cholecystitis and the decline of anabolic function is currently difficult to determine, and further research is needed. Bacterial infections have also been identified as an important cause of acalculous cholecystitis. In the present study, patients with cholecystitis also had a significantly higher incidence of spontaneous peritonitis and neutrophil percentage than those without cholecystitis. In terms of clinical outcomes, there was no significant difference in the incidence of liver failure and mortality between the two groups, but the mean hospital stay in the cholecystitis group was significantly longer than that in the non-cholecystitis group, consistent with the worse anabolic indices in this group, suggesting that gallbladder inflammation may serve as a potential indicator of poor prognosis.

Nevertheless, the present study is retrospective, and the sample size of patients with liver failure and death was small. Therefore, our findings could be biased. In the future, prospective studies with a larger sample size are needed to clarify the value of mechanisms of acalculous cholecystitis as an extrahepatic manifestation of HE.