Clinical approach and medical history

Cholestatic DILI can manifest clinically in a range of presentations, including asymptomatic ALP elevation, mild non-specific symptoms (fatigue, fever, anorexia, weakness, vomiting, chills, right upper quadrant pain, pruritus, skin rash, etc.) to severe protracted jaundice, ascites, coagulopathy, and encephalopathy [1, 12].

Clinical suspicion should be guided by a detailed medical history including exposure to all drugs, herbs, and dietary supplements consumed in the last 6 months. However, clinicians should bear in mind that there are drugs with a longer latency such as minocycline, statins, metrotexate, or nitrofurantoin [13, 14]. A meticulous history should include information about start and stop dates of each suspected agent, eventual dosage changes, and previous exposure. Worsening of liver injury after the re-administration of the drug (rechallenge) which often happens inadvertently, and improvement after cessation of the drug (dechallenge) need to be looked for to support a DILI diagnosis [15]. Other situations that may cause cholestasis such as alcohol consumption, total parenteral nutrition, or causes of hepatic ischaemia (heart failure, sepsis, or hypotension) must be investigated [16].

Laboratory test and characterisation

In most cases of DILI, the diagnostic suspicion is triggered by an alteration in liver biochemical blood test. The initial laboratory tests should include ALT, ALP, total bilirubin, and direct bilirubin levels as well as international normalized ratio (INR) and albumin, which determine the severity [16, 17].

Around 10–20% of the population have minimal alterations in liver biochemical blood test [15], so to define correctly DILI, it is necessary to meet one of the following requirements: a) > 5 ULN elevation in ALT, b) > 2 ULN elevation in ALP in absence of other causes (e.g., bone pathology) and especially when accompanied by elevated gamma-glutamyltransferase (GGT), c) > 3 ULN elevation in ALT and > 2 ULN elevation in total bilirubin concentration. In patients with a baseline abnormal liver test, ULN is replaced by the mean values prior to the initiation of the hepatotoxic agent [2, 15, 17].

In order to categorize DILI according to its biochemical pattern, the calculation of the R value is used. This is defined as the result of dividing ALT/ULN-ALT by ALP/ULN-ALP, using the first serum values available during the event. If the R value is ≤ 2, the pattern is defined as cholestatic while values ≥ 5 classify it as hepatocellular liver injury and intermediate values as mixed liver injury. Cholestatic DILI can also be defined as an increase in ALP above 2 times the ULN [18]. Approximately, 20–40% of all DILI cases have a cholestatic pattern. Mixed liver injury typically behaves like cholestatic liver injury so some analysis in the literature combines both [19]. Moreover, studies on hepatic histological findings show similar features in biopsies from cases of mixed and cholestatic injury [20]. Consistent biochemical pattern of liver injury observed for many drugs is considered a useful clue in the diagnosis of DILI, but clinicians should bear in mind that this “signature” is not so straightforward as some drugs have been associated with various biochemical profiles [16]. In addition, the analytical parameters (likewise R value) may be dynamic during the evolution of hepatocellular cases. Therefore, the same drug may initially produce hepatocellular damage, which may later turn into mixed damage or even cholestatic damage. This is because the dynamics of ALT resolution is much faster than that of ALP [17]. This could be a confounding issue to define the pattern damage in some cases.

Furthermore, laboratory workup to exclude alternative causes of liver damage is needed. It is recommended to rule out infectious hepatitis in suspected DILI including routine test for anti-hepatitis E virus (HEV), immunoglobulin M (IgM; or HEV-RNA), and hepatitis C virus (HCV)-RNA [16, 17]. While most infectious hepatitis manifests with a hepatocellular injury pattern, some microorganisms such as Epstein-Barr virus, hepatitis A virus, Salmonella typhi, and Coxiella burnetii can cause cholestatic liver injury [19].

Other laboratory tests recommended in the aetiological assesment of liver damage are ceruloplasmin levels (Wilson’s disease), autoantibodies, and immunoglobulin G (IgG; autoimmune hepatitis) and, especially in cholestatic cases, antimitochondrial antibodies levels to rule out PBC [15].

Imaging

Imaging tests beyond abdominal ultrasound (which is typically normal) are usually not necessary in a suspected case of DILI. This allows an initial assessment of biliary obstruction, liver cirrhosis, or focal parenchymal lesions. However, when a cholestatic pattern is present and/or jaundice or abdominal pain predominates, it is recommended to perform computerized tomography (CT) or magnetic resonance cholangiography to exclude other aetiologies.

In the presence of biliary tract strictures in a patient with suspected DILI, a diagnosis of drug-induced secondary sclerosing cholangitis, characterised by jaundice and slower resolution, should be considered. This disorder has been described with exposure to amiodarone, atorvastatin, amoxicillin-clavulanate, gabapentin, infliximab, 6-mercaptopurine, nivolumab, sevoflurane, ketamine, and venlafaxine [16, 17, 21, 22].

Biopsy

Liver biopsy should be considered in patients with suspected DILI who worsen or non-resolve the biochemical abnormalities despite drug discontinuation. However, it should be emphasised that the time to resolution of cholestatic DILI is slower than for the hepatocellular pattern [19]. Histological findings may be helpful in the differential diagnosis by identifying other cholestatic diseases like antimitochondrial antibody-negative PBC, small duct PSC, or hepatic overlap syndromes [12].

Moreover, biopsy can be a useful tool to establish prognosis of DILI cases, because some histological findings (ductular reaction, microvesicular steatosis, higher degrees of necrosis, and hepatic fibrosis) have been associated with an increased risk of liver failure and death [20].

Causality assessment

In order to confidently attribute manifestations of liver injury to a particular drug, a structured assessment is necessary. For this purpose, various causality scales have been developed. The DILIN structured expert opinion process scores DILI cases from 1 (definite) to 5 (unlikely) according to the likelihood of being caused by a given drug. However, this scale has a complex applicability due to the lack of DILI experts and low external validity. In the pharmacovigilance arena and clinical practice, the Rousell Uclaf causality assessment method (RUCAM) [18], also known as Council for International Organizations of Medical Sciences (CIOMS)/RUCAM scale, has been used since more than 30 years, although this tool is critiqued due to its complexity and poor reproducibility among raters. Recently, in a collaborative work, a revised electronic causality assessment method (RECAM) has been developed, which has some advantages over RUCAM by eliminating risk factors, simplifying the latency and dechallenge fields and the ability to include data on histological findings, other diagnostic tests or rechallenge if any; nevertheless, the reliability of scale needs to be validated in future studies [15, 23].

NSAIDs

The prevalence of NSAID hepatotoxicity in several large prospective DILI registries worldwide oscillates between 3% and 36%, being a strikingly frequent causative agent of DILI in Italy [24–26]. DILI cases attributed to NSAIDs collected in DILIN were analyzed. There were significant rates of autoimmunity traits (38%). The most frequent agent implicated was diclofenac, all cases exhibited a hepatocellular pattern, but subtle increases of ALP were identified. Diclofenac-induced liver injury was often severe [27]. Ibuprofen has been also reported in the literature as causative of DILI, with a predominance of hepatocellular pattern [24]. Nonetheless, an analysis of cases of ibuprofen-related DILI in Spanish and Latin-American revealed an important representation of cholestatic/mixed form of liver damage (42%) [26]. Besides, vanishing bile duct syndrome, which is considered a serious variant of liver damage characterised by bile duct injury and ductopenia has been linked to ibuprofen use [24]. Case reports of celecoxib-and sulindac-induced cholestasis have been published, notably, presenting as fulminant liver failure [28, 29].

On the other hand, there are described cases of long-standing cholestasis due to NSAIDs as flurbiprofen or celecoxib reported in the literature [30, 31]. Liver damage associated with piroxicam and rofecoxib is typically cholestatic or mixed [32–34]. A recent multicentre international study carried out in Latin America and Spain analyzing DILI cases due to nimesulide showed that the percentage of cholestatic/mixed damage was 33%, with a significantly higher proportion of pruritus (37% vs. 5.3%) and lower severity (percentage of acute liver failure, 5.3% vs. 29%) compared to hepatocellular cases [35].

Antiinfectives

Statins

Statins are a common cause of DILI worldwide [69, 70]. Statin-associated DILI has a genetic background as a specific polymorphism on chromosome 18 (rs116561224) has been identified [65]. In the Spanish DILI Registry, atorvastatin was one of the drugs linked to cholestatic damage in elderly patients [71]. Atorvastatin-induced liver injury is a well-defined entity whose pattern of damage is largely cholestatic although it may be presented as autoimmune-like liver disease [72–75]. Simvastatin-induced cholestasis has been reported but it patterns of damage is mostly hepatocellular [76, 77].

Psychotropic drugs

Chlorpromazine is a prototypical, long-standing example of a hepatotoxic drug. This agent causes cholestatis and it is responsible for chronic cholestasis and even ductopenia, leading to cirrhosis [78]. Other psychotropic agents which classically have been related to cholestatic damage are tricyclic antidepressants (imipramine or amitriptyline) or selective serotonin reuptake inhibitors (fluoxetine, duloxetine, or citalopram) [79–82].

Immunomodulator and antineoplastic drugs

Azathioprine is an immunomodulator widely used in autoimmune diseases. In some series, percentage of DILI due to azathioprine ranges from 3% to 10%, and typically presents during the first 3 months of therapy [83–85]. Although azathioprine-induced liver damage is predominantly hepatocellular, azathioprine-induced cholestasis is a well-established entity with many cases reported in the literature. In some instances, in which a liver biopsy was performed, nodular regenerative hyperplasia was a prominent histological feature [86–89].

Eculizumab is a monoclonal antibody to complement factor 5, which blocks complement activation and is used to treat paroxysmal nocturnal hemoglobinuria and also hemolytic uremic syndrome. This agent has been linked to cholestatic injury [90]. Cases of cholestasis-induced chemotherapeutics, as cisplatin, have been previously published [91]. The vast majority of immunotherapy-related DILI is biochemically hepatocellular, but in some cases a cholestatic or mixed damage arises [92]. It is worth to highlight a particular type of immunecheckpoint inhibitors-induced liver damage known as secondary sclerosing cholangitis. This entity is characterized by cholestatic pattern, with structural change (diffuse biliary duct dilatation and thickening of the bile ducts) [93]. It has been reported cases of secondary sclerosing cholangitis due to nivolumab, avelumab, pembrolizumab, durvalumab, and atezolizumab [94–102]. Cases of cholestasis due to checkpoint inhibitors have a poorer response to standard treatment compared to hepatocellular pattern with greater rates of steroid-resistance in some published cases [94, 95, 98].

Pexidartinib is a potent kinase inhibitor drug with a highly lithified clinical setting, used in the treatment of adults with symptomatic tenosynovial giant cell tumour. Patients treated with this molecule frequently experienced increases of ALP (near to 20%). Furthermore, biopsy revealed bile duct damage and duct loss. Cases of acute liver failure and liver transplantation have been reported [103, 104].

AAS

The use of banned ASS is a growing concern worldwide. The fraction of AAS cases in the DILIN Registry is 5% of the total cases [105]. In the Spanish and the Latin American DILI cohorts, the proportion of AAS-induced liver injury is 2.3% and 5%, respectively [5, 106]. AAS hepatotoxicity has been reported extensively in the literature. Liver damage related to anabolic steroids is typically cholestatic, with deep and prolonged jaundice (normally than 3 months) as well as itching, which is sometimes refractory to pharmacological therapy. Hy’s law is commonly fulfilled in hepatocellular cases, but fulminant liver failure has not been reported. Acute kidney injury accompanies AAS-hepatotoxicity in 14–24% of cases, and it is related to the extremely high bilirubin levels [107, 108]. Besides, the long-term use of anabolic steroids has been associated with peliosis hepatis and liver tumours [109].

Herbs

Herbal products and dietary supplements use are a growing habit nowadays. Although liver damage secondary to herbs usually presents with a hepatocellular pattern, the liver injury related to several herbal products is characterised by a cholestatic/mixed phenotype [5]. Kratom, which is botanical extract from the Mitragyna speciosa consumed in many Southest Asiatic countries is one of the herbs that characteristically presents as long-lasting cholestatic damage, behaving similarly to anabolic steroids [110].

Ashwagandha (also called “Indian ginseng”), derived from Withania somnifera, is taken for its anti-inflammatory and neuroprotective condition in Southest Asia and India. Ashwagandha-related liver impairment is mainly cholestatic or mixed [111]. Neither herb (Kratom and Ashwagandha) has been linked to acute liver failure.

Tribulus is an herbal product (resulting from fruits or roots of Tribulus terrestris) used globally for aphrodisiac purposes and the bodybuilding setting. Liver damage due to tribulus is characterized by profound jaundice accompanied by renal impairment. Histologically, it usually presents as bland cholestasis [112].

Severe acute respiratory syndrome coronavirus 2 vaccine

Following the establishment of the global vaccination campaign against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, acute de novo hepatitis cases began to be identified, with typical features of autoimmune hepatitis but temporally coinciding with the SARS-CoV-2 vaccine. Subsequently, case reports and case series of probable hepatitis secondary to the COVID-19 vaccine were published [113]. Recently, an international multicentre study has reported 59 cases of post-vaccination hepatitis, finding significant rates of positive autoantibodies, elevated IgG levels, and biopsies consistent with autoimmune hepatitis. Although 95% of the cases corresponded to a hepatocellular pattern, 5% of them exhibited a mixed pattern. Centralized analysis of biopsies identified 2 cases with bland cholestasis in the histology [114]. In a previous international study of 87 patients, the proportion of SARS-CoV-2 vaccine-related cholestatic and mixed hepatotoxicity was 6% and 10% respectively [115]. A summary of the most representative drugs for the different cholestatic phenotypes of liver damage can be observed in Table 3.

UDCA

UDCA has been used for decades in cholestatic DILI to reduce the time to resolution. In cholestatic liver disease, UDCA provides protection against bile salt toxicity, stimulates hepatobiliary secretion, has antioxidant activity, enhances glutathione levels, and inhibits liver cell apoptosis [116, 128]. A recent systematic review suggests that UDCA may be effective and safe in both prevention and treatment of DILI, although the lack of robust trials means that a strong recommendation cannot be made [129].

Corticosteroids

Corticosteroids have been prescribed empirically, especially in DILI patients with immnoallergic features or when there is no response to other therapies. Their use is controversial as some studies have shown no benefit, or even worsening, in cases of acute liver failure [130, 131]. On the other hand, a recent propensity score-matched analysis showed benefits and lack of serious risk of corticosteroids in DILI. In these cohorts 12% and 20% of the group treated with corticosteroids were cholestatic and mixed respectively, compared to 20% cholestatic and 20% mixed pattern in the untreated arm [132]. Specifically, in cholestatic DILI, there is limited evidence on the use of corticosteroids. Their use could be beneficial in combination with UDCA in terms of rapid reduction of bilirubin and transaminases [133].

Cholestyramine

Specific therapies have been described for particular forms of DILI. One example is the use of cholestyramine for terbinafine-induced liver injury, which presents with a cholestatic pattern in most cases. Cholestyramine also seems to be beneficial in DILI caused by leflunomide, although this agent mostly induces a hepatocellular pattern. The use of cholestyramine appears to short the course of hepatotoxicity, although these data come from case report and case series [17, 134, 135].

MARS^®

In patients who do not respond to standard medical therapy, the use of extracorporeal liver support systems may be considered, although these methods have not been shown to decrease mortality in patients with liver failure [17, 134]. However, an improvement of cholestasis parameters in patients with anabolic steroid-induced liver injury and DILI related with a few drugs has been reported with the use of extracorporeal liver support system, called albumin dialysis with MARS^® [136–139].

Liver transplantation

When acute liver failure ensues, liver transplantation should be contemplated as the first-line rescue therapy. In this situation, the likelihood of spontaneous recovery is about 25% [16, 17, 140].