Sepsis and Cholestasis

Michael Fuchs, MD, PhD, FEBG,Arun J. Sanyal, MD, MBBS*

Division of Gastroenterology, Department of Internal Medicine,

Virginia Commonwealth University Medical Center, 1200 E Broad Street,

PO Box 980341, Richmond, VA 23298–0341, USA

Sepsis is defined as the presence or presumed presence of an infection ac-companied by evidence of a systemic inflammatory response. This responseis a complex cascade of events that encompasses proinflammatory, anti-inflammatory, humoral, cellular, and circulatory involvement. Clinical fea-tures of sepsis may include fever or hypothermia, leukocytosis or leukope-nia, and tachypnea or raised minute ventilation. Sepsis may progress toorgan dysfunction/failure and septic shock, a clinical scenario of hypoten-sion, despite adequate fluid resuscitation.

Sepsis is the leading cause of death in critically ill patients, the secondleading cause of death among patients in non–coronary intensive care units,and the tenth leading cause of death overall in the United States [1,2]. Theaverage length of hospital stay caused by sepsis is 3 weeks, which results inan economic burden of nearly $17 billion annually in the United States [3].Significant progress has been achieved in our understanding of the patho-physiologic alterations that occur during activation of the inflammatorycascade, but sepsis-associated mortality seems unlikely to change. Unfortu-nately an increasing number of elderly and immunocompromised patientstogether with an increasing number of pathogens with resistance to antibi-otics likely will increase the incidence of sepsis in the near future.

For decades, gram-negative organisms were considered the main cause ofsepsis in the United States. In the last decade, gram-positive organisms havebeen increasingly identified as the source of sepsis and currently surpassgram-negative pathogens as the etiologic agents of sepsis [4,5]. This findingis consistent with data from Europe, which showed that 60% of community-acquired bloodstream infections were caused by lower respiratory tract,

Clin Liver Dis 12 (2008) 151–172

* Corresponding author.

E-mail address: ajsanyal@hsc.vcu.edu (A.J. Sanyal).

1089-3261/08/$ - see front matter � 2008 Elsevier Inc. All rights reserved.

doi:10.1016/j.cld.2007.11.002 liver.theclinics.com

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intra-abdominal, and genitourinary tract infections, with 44% of the path-ogens being gram positive, most of which were Staphylococcus aureus andStreptococcus pneumoniae [6].

Jaundice or hyperbilirubinemia is the principal clinical manifestation ofcholestasis. Jaundice does not generally appear until a patient’s serum totalbilirubin exceeds 2.5 mg/dL. In general, inflammatory jaundice may resulteither directly from bacterial products or as a consequence of the host re-sponse to infection. Although jaundice may occur as an isolated abnormal-ity with predominantly unconjugated hyperbilirubinemia in patients withbacterial infections, it usually is associated with features of cholestasiswith predominantly conjugated hyperbilirubinemia. It is not widely appreci-ated that infection and sepsis-associated cholestasis are the leading causes ofjaundice in hospitalized patients and are surpassed only by malignant biliaryobstruction [7]. The incidence of sepsis-associated cholestasis in the newbornand early infant population varies between 20% and 60% [8]. Sepsis is morelikely to manifest with jaundice in infants and children compared to adults.In this population, male infants have a higher incidence of jaundice.

Jaundice is commonly encountered in critically ill patients (eg, patients inthe intensive care unit) with an incidence as high as 40% [9]. In these pa-tients the clinical picture often poses a challenge in terms of diagnostic eval-uation and management. Several factors besides obstructive jaundice mustbe considered as contributing to jaundice, including (1) sepsis, (2) hemolysis,(3) disseminated intravascular coagulation, (4) hypoxemia, (5) heart failure,(6) total parenteral nutrition, (7) mechanical ventilatory support, (8) renalinsufficiency, (9) pre-existing liver disease, and (10) drug toxicity. Persistentjaundice has been shown to represent a surrogate marker for patientmorbidity and mortality in such cases [10]. The unfavorable prognosis isprimarily related to the extrahepatic complications of the systemic inflam-mation, whereas cholestasis per se rarely progresses to liver failure withcoagulation defects and encephalopathy.

Physiology of bile formation and bilirubin metabolism

The molecular and biochemical mechanisms by which cholestasis andjaundice develop in response to inflammation and sepsis are best consideredin the context of normal physiology.

Bile formation

Bile formation (Fig. 1) depends on the proper functioning of integralmembrane proteins that transport bile constituents across the canalicularplasma membrane. It also requires an intact cytoskeleton, tight junctions,and an intracellular signal transduction cascade for regulation of trans-porter expression and localization [11]. Bile acids are transported to the liverafter intestinal absorption. This enterohepatic circulation minimizes fecal

Fig. 1. Bile formation. At the basolateral membrane of hepatocytes (upper panel, left side) bile

acid uptake is mediated by a sodium-dependent (NTCP) and a sodium-independent (OATP)

uptake system. Organic cations are taken up. OCT1, MRP3, MRP4, and the heteromeric

organic solute transporter OSTa/b (upper panel, right side) provide an alternative excretion

route for bile acids into the systemic circulation. Bile acids are excreted into bile via a canalicular

bile salt export pump. The export pump MRP2 can excrete bile acids and conjugated organic

anions. The phospholipid export pump multidrug resistance protein 3 mediates the excretion

of phosphatidylcholine (upper panel, left side). The other main lipid excreted into bile is choles-

terol, and its export is facilitated by ABCG5/G8 (upper panel, center right). The canalicular

membrane contains a multidrug export pump (multidrug resistance protein 1) for cationic

drugs, a chloride/bicarbonate anion exchanger (anion exchanger isoform 2), and breast cancer

resistance protein, a transporter for anionic conjugates. Cholangiocytes (bile duct epithelial

cells) contain a chloride channel that is the cystic fibrosis transmembrane regulator (CFTR)

driving bicarbonate excretion via anion exchanger isoform 2 (lower panel, right side). Cholan-

giocytes contain the ileal sodium-dependent bile acid transporter (ASBT) for reabsorption

and cholehepatic cycling of bile acids and OSTa/b, which is also involved in bile acid reabsorp-

tion (lower panel, left side).

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bile acid loss (approximately 1%) and de novo bile acid synthesis by theliver. At the basolateral (sinusoidal) membrane, aided by the ATP-dependentNa/K/ATPase pump, which maintains an inwardly directed sodium gra-dient, the sodium taurocholate co-transporting polypeptide (NTCP,SLC10A1) is largely responsible for the first-pass clearance of conjugatedbile acids as they are returned to the liver in portal blood [12]. Unconjugatedbile acids are variably taken up by one or more of four members of thesolute carrier organic anion transporter family (SLC21), formally knownas organic anion transporting polypeptides (OATPs) [13]. These nonspecific

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carriers also facilitate the uptake of many different organic anions, oligopep-tides, and organic cations. Organic cations are taken up by another solutecarrier, the organic cation transporter 1 (OCT1, SLC22A1) [14]. The baso-lateral membrane also contains efflux systems for bile acids, the multidrugresistance-associated proteins 3 (MRP3, ABCC3) and 4 (MRP4, ABCC4)[15], and the heterodimeric organic solute transporter OSTa/b [16].

Bile acid-dependent and -independent bile flow is largely generated by thebile salt export pump (BSEP, ABCB11) and the multidrug-resistance-asso-ciated protein 2 (MRP2, ABCC2), respectively [10]. The bile salt exportpump and MRP2 are members of the ABC superfamily of ATP-dependenttransporters. Although the bile salt export pump is relatively specific for thesecretion of bile acids, MRP2 exports glutathione and numerous other or-ganic anions into bile usually conjugated with glutathione, glucuronide, orsulfate [17]. The multidrug resistance protein 1 (ABCB1) [18] is responsiblefor transporting amphipathic organic cations (eg, drugs). Secretion of phos-pholipids (eg, phosphatidylcholines) is facilitated by a flippase (multidrugresistance protein 3, ABCB4) [19], and biliary cholesterol elimination re-quires the two half-transporters ABCG5/G8 [20], whereas anionic conju-gates are secreted into bile via the breast cancer resistance protein(ABCG2) [21]. Finally, the chloride-bicarbonate anion exchanger isoform2 (SLC4A2) promotes bicarbonate secretion [22].

At the bile duct level, the fluidity and pH of the canalicular bile are reg-ulated by a cyclic AMP-activated chloride channel, the cystic fibrosis trans-membrane regulator (ABCC7), which drives the secretion of bicarbonatemediated by anion exchanger isoform 2 [23]. Bile acids are reabsorbedfrom cholangiocytes via the apical sodium-dependent bile acid transporterASBT/SLC10A2 [24] and effluxed by OSTa-OSTb [16].

Bilirubin metabolism

Bilirubin is the end product of breakdown of the heme moiety of hemo-proteins. In humans, the liver excretes approximately 300 mg of bilirubinper day, 80% of which is derived from hemoglobin [25]. Unconjugatedbilirubin is a highly hydrophobic molecule that circulates tightly but is re-versibly bound to albumin in plasma and, to a minor amount, to apolipo-protein D [26]. This high affinity binding to albumin together with the14-day half-life of albumin explains why jaundice may persist beyond thenormalization of the patient’s physiology and serum laboratory tests.

At the basolateral membrane of hepatocytes (Fig. 2), bilirubin dissociatesfrom albumin and hepatic uptake is promoted by members of the organicanion transport protein family (OATP, SLC21A) [27,28]. Within hepato-cytes, bilirubin is bound by a group of cytosolic proteins (mainly glutathi-one-S-transferases) thereby preventing the efflux of bilirubin from the celland conjugated to monoglucuronides and diglucuronides by UGT1A1,a member of the uridine diphosphate-glucuronosyltransferase family [29].

Fig. 2. Bilirubin metabolism. Unconjugated bilirubin (UCB) dissociates from albumin at the

basolateral membrane and is taken up by OATP. Intracellularly, UCB is bound to cytosolic

proteins, such as glutathione-S-transferase (GST), and then conjugated by uridine diphos-

phate-glucuronosyltransferase (UGT1A1). After glucuronidation, conjugated bilirubin (CB)

is transported across the canalicular membrane by the apical export pump MRP2.

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After conjugation within the hepatocyte, which yields relatively hydrophilicmolecules monoglucuronosyl and bisglucuronosyl bilirubin, the conjugatesare transported across the canalicular membrane into bile by the apical con-jugate export pump MRP2, a member of the ABCC subfamily of ATP-dependent transporters.

Hepatic response to inflammatory processes: the liver as actor

The liver plays a central role in the regulation of host defense. Kupffercells of the liver comprise approximately 70% of the total macrophage pop-ulation of the body and are presumed to represent the primary defenseagainst portal bacteremia and endotoxinemia by removing them from theportal vein blood [30,31]. Kupffer cells are also potent scavengers for sys-temic and gut-derived inflammatory mediators and cytokines, thereby limit-ing the extent of the inflammatory response [32]. Hepatocytes exhibitreceptors for several mediators, including tumor necrosis factor a (TNF-a)and interleukins (IL). In response to inflammation they modify theirmetabolic pathway toward amino acid uptake, ureagenesis, gluconeogene-sis, and increased synthesis and release of coagulant factors, complementfactors, and antiproteolytic enzymes, all prioritizing protein synthesis andtissue repair [33].

Pathophysiology of sepsis-associated cholestasis

Hepatic response to inflammatory processes: the liver as victim

Kupffer cells, hepatocytes, and sinusoidal endothelial cells contribute tothe liver’s response to inflammation and sepsis. Endotoxins are frequentlyreleased into the circulation from peripheral sites of infection without the

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entry of intact infectious bacteria into the blood [34]. Once activated,Kupffer cells are the source of the soluble mediators of sepsis, includingproinflammatory cytokines, nitric oxide, reactive oxygen products, andeicosanoid mediators [35]. Proinflammatory cytokines include TNF-a,IL-1, IL-6, and IL-12 [36].

TNF-a forms a biologically active trimer and binds to two receptors ofdistinct molecular weights. Stimulation of the type I TNF-a receptor repro-duces many of the biologic activities of TNF-a, including cytotoxicity,expression of adhesion molecules on endothelial cells, and activation of nu-clear factor kB [37]. The complex effects of TNF-a in the liver include theinduction of cytokines for tissue injury and repair [36]. IL-1 exerts its effectsby binding to the IL-1 receptor. TNF-a and IL-1 share several biologiceffects and may synergize in their toxic effects. Both cytokines are pyrogenic,and they activate the cytokine network, the coagulation system, fibrinolysis,and neutrophils [37]. IL-6 is one of the most important cytokines that affectthe liver in patients with sepsis, because it orchestrates synthesis of acutephase proteins in the septic liver [38]. The biologic effects of IL-6 are medi-ated by the common signal transducer gp130 and include production ofimmunoglobulins, proliferation and differentiation of T cells, enhancementof the activity of natural killer cells, and maturation of megakaryocytes[37]. IL-12 induces production of interferon-g in T cells and natural killercells and is considered to be the key cytokine in induction of T helper celltype 1 activation [39]. IL-12 and interferon-g strongly potentiate eachother’s production and the effects of endotoxin on monocytes andmacrophages.

To control the exaggerated proinflammatory response, the immune sys-tem produces various anti-inflammatory mediators to reduce the synthesisand action of proinflammatory cytokines. The interactions between pro-and anti-inflammatory mediators play a crucial role in maintaining a balancebetween adequate immune response to infections and uncontrolled systemicinflammation. Activation of this compensatory anti-inflammatory responsesyndrome can lead to suppression of the immune system in later stages,which increases the susceptibility of patients to opportunistic infections.

Kupffer cell–derived leukotriene B4 and TNF-a attract neutrophils to theliver. These activated leukocytes express increased levels of integrins andhave increased adherence to endothelial cells in the septic liver. Once adher-ent to the endothelium, neutrophils transmigrate into the parenchyma,where they produce reactive oxygen radicals and proteases to induce hepa-tocyte injury [40].

Hepatic endothelial cells that are located adjacent to hepatocytes in theliver sinusoid are in contact with Kupffer cells, their mediators, and adher-ent neutrophils. These interactions change the endothelial cells to acquireprocoagulant and proinflammatory activities, as observed in patients withsepsis [38]. Endothelial cells in the normal liver spontaneously produceIL-1 and IL-6, and this production is increased when endothelial cells are

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exposed to endotoxin [41]. Endothelial cells produce also nitric oxide, whichregulates the systemic and hepatic circulation and may lead to severe hypo-tension and vascular collapse, which inevitably impair liver circulation[42,43]. Endothelial damage, decreased blood flow through the sinusoids,and formation of fibrin microthrombi are the results of endotoxin-mediatedcompromise of hepatic microvascular circulation causing pronounced hepa-tocellular necrosis [44,45].

Hepatocellular and ductal mechanism of cholestasis

Cholestasis may result from either a functional defect in bile formation atthe level of the hepatocyte (eg, reduced expression and function of transportsystems) or an impairment in bile secretion and flow at the bile duct level(Fig. 3). Most information about hepatocellular transporter expression isderived from animal studies. Decreased bile acid secretion and bile flow dur-ing endotoxemia is caused by a concomitant reduction in the expression ofthe export pumps BSEP and MRP2, respectively [46,47]. The maximal re-duction in bile acid flow seems to occur within the first 24 hours after cyto-kine challenge and may be augmented nitric oxide–mediated impairedcanalicular motility [48]. In contrast to the transcriptional down-regulationof these transporters in rodents, posttranscriptional mechanisms seem toplay a more prominent role in humans [49,50]. This finding has been con-firmed with percutaneous liver biopsy samples from patients with inflamma-tion-induced cholestasis [51]. One such mechanism involved is the rapidretrieval of hepatobiliary transporters from the canalicular and basolateralmembrane [52–54], which occurs even before down-regulation of mRNAand protein levels [55].

Fig. 3. Molecular mechanisms of sepsis-associated cholestasis. Endotoxemia causes down-reg-

ulation of the basolateral uptake (NTCP, OATP) and canalicular export (BSEP, MRP2) sys-

tems (left side). Additional alterations (right side) include impairment of transporter

trafficking to and from the canalicular membrane caused by cytoskeletal changes to microtu-

bules and pericanalicular actin microfilaments. Disruption of tight junction (center) further con-

tributes to cholestasis.

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In addition to hepatocellular changes, sepsis is also known to frequentlycause bile duct changes [56]. TNF-a, IL-1b, IL-6, and nitric oxide all impaircAMP-dependent ductal chloride and bicarbonate secretion [57,58]. Inter-feron-g also stimulates nitric oxide production by cholangiocytes and pro-motes lymphocytic infiltration of the biliary epithelium [23]. Beyondrepresenting a target for inflammatory mediators, the biliary epitheliumactively participates in liver inflammation by secreting proinflammatoryand chemotactic cytokines and growth factors that are not produced underphysiologic conditions.

Intrinsic hepatoprotective responses to cholestasis

Cholestasis is associated with a disruption of the enterohepatic and neph-rohepatic circulation, with an increased cholehepatic shunting (reabsorbingtoxic, stagnant bile acids from obstructed ducts) and an increased basolat-eral efflux of biliary compounds from liver followed by their renal elimina-tion. Under conditions of inflammation and sepsis, these secondaryalterations in transport systems may at least partly explain the impairmentof transport function resulting in or maintaining cholestasis (Fig. 4). Al-though some of these alterations are ‘‘pro-cholestatic,’’ however, otherchanges are ‘‘anti-cholestatic,’’ providing alternative excretory routes foraccumulating cholephiles in cholestasis. These transporter changes may beassisted by metabolic changes of phase I and II enzyme systems (eg, cyto-chrome P450 enzymes, sulfotransferases, glucuronyltransferases) involvedin the detoxification of bile acids and other biliary compounds, whichmake them less toxic and better substrates for alternative elimination path-ways [59].

Fig. 4. Hepatocellular responses to sepsis-associated cholestasis. At the basolateral membrane

of hepatocytes (upper panel, left side) bile acid uptake is reduced by decreased expression of

NTCP and OATP uptake system. At the same time, expression of alternative basolateral export

systems, such as MRP3, MRP4, and OSTa/b, is increased (upper panel, right side). Bile acid de-

toxification (upper panel, left side) occurs by up-regulating key enzymes of hydroxylation

(CYP3A4) and conjugation (SULT2A1, UGT2B4, UGT2B7). Intracellular accumulation of

bile acids suppresses key enzymes of bile acid synthesis, such as CYP7A1, CYP27A1, and

CYP8B1, respectively (upper panel, right side). Not displayed is the activation of renal bile

acid transport systems.

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Reducing basolateral bile acid uptake

TNF-a and IL-1b reduce the expression of NTCP and OATPs in a nu-

clear receptor–dependent manner [60], thereby decreasing the basolateralbile acid uptake. Altered membrane fluidity of the basolateral membranecaused by endotoxin may further contribute to reduced bile acid uptake[61]. These adaptive changes may be considered as a major hepatic defensemechanism counteracting bile acid accumulation within hepatocytes.

Basolateral bile acid excretion

Although bile acids are normally excreted into bile, alternative basolat-

eral bile acid excretion into portal blood may become a major pathwayfor hepatic bile acid elimination during cholestasis. Alternative basolateralbile acid export is mediated by members of the MRP family (MRP3 andMRP4). These export systems are normally expressed at low levels at thebasolateral membrane but are dramatically up-regulated by cytokines[62,63] and in cholestatic liver diseases [64,65]. Because MRP3 and MRP4are able to transport sulfated and glucuronidated bile acids that are elimi-nated into urine during cholestasis [66], the induction of these transportersmay explain the shift toward renal excretion of bile acids as a major mech-anism for bile acid elimination.

Bile acid hydroxylation and conjugation

Nuclear receptor–dependent bile acid hydroxylation by CYP3A4 ren-

ders bile acids more hydrophilic, less toxic, and more amenable for uri-nary excretion [59], which represents an important pathway for bileacid detoxification. Besides hydroxylation, conjugation of bile acidswith sulfate or glucuronidate is also an important mechanism of bileacid detoxification. Dehydroepiandrosterone-sulfotransferase catalyzessulfoconjugation of bile acids [67]. Upon sulfation, bile acids becomepolar and water soluble, which facilitates urinary excretion [68]. Glucur-onidation of bile acids is catalyzed by the UDP-glucuronosyltransferasesUGT2B4 and UGT2B7 [69] and is an almost selective conjugation path-way for 6-hydroxylated bile acids, such as hyocholic acid and hyodeoxy-cholic acid, that are formed from lithocholic acid and chenodeoxycholicacid by CYP3A4. An important consequence of bile acid glucuronidationis the introduction of an additional negative charge in the molecule thatallows their transport by MRP3, which may explain the appearance ofthese more hydrophilic compounds in urine of patients with cholestasis[70].

Inhibition of bile acid synthesis

Key enzymes of bile acid synthesis, such as cholesterol 7a-hydroxylase

(CYP7A1), sterol 27-hydroxylase (CYP27A1), and sterol 12a-hydroxylase(CYP8B1), are repressed in response to accumulating intracellular bile

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acid levels during cholestasis. This occurs in nuclear receptor–dependentand –independent mechanisms [59].

Renal bile acid transport

Increased renal excretion of bile acids may be attributed to increased pas-

sive glomerular filtration because of elevated serum bile acid levels and re-duced tubular bile acid reabsorption via repressed ASBT [71]. Passiveglomerular filtration of bile acids also might be aided by active tubular se-cretion of sulfated and glucuronidated bile acids via MRP2 and MRP4,which are localized to the apical tubular membrane [72].

Bilirubin metabolism in systemic inflammation

The pathogenesis of jaundice in systemic infections is multifactorial. Thedevelopment of jaundice may occur from an aberration in the processing ofbilirubin by the hepatocyte or from other effects on the liver that lead toaccumulation of bilirubin within the body.

Hepatocellular processing of bilirubin

Intrahepatic processing and, in particular, canalicular excretion are im-

portant mechanisms for jaundice associated with infections. This findingis supported by the occurrence of mainly conjugated hyperbilirubinemiain severe inflammation and sepsis. It is unlikely that bilirubin conjugationis substantially affected by sepsis because most of the bilirubin in blood isconjugated. Endotoxin decreases the clearance of conjugated bilirubin tothe same degree as unconjugated bilirubin, which suggests that the conjuga-tion of bilirubin does not contribute to the impairment in bilirubin clearance[73]. This finding is further supported by the observation that the degree ofbilirubin conjugation in livers exposed to endotoxin is not substantially dif-ferent from normal controls [73].

Hemolysis

Infection, even in the absence of sepsis, may cause hemolysis. Although

hemolysis contributes to jaundice in sepsis, it is not the principal mechanismbecause the jaundice is caused by conjugated and not unconjugated hyper-bilirubinemia [74]. There are multiple mechanisms by which hemolysis mayoccur in the setting of bacterial infection [75]. Clostridium perfringens cangive rise to severe, often fatal hemolysis in subjects with normal red cells[76]. It is triggered by C perfringens phospholipase C, which reacts withred cell membrane lipoproteins to release lysolecithin and facilitates redcell membrane lysis. Other infections that commonly cause hemolysis aremalaria and babesiosis [77]. Escherichia coli infection periodically maylead to hemolysis in normal red blood cells [78]. Aside from bacterial infec-tion directly causing hemolysis, multiple drugs (eg, penicillin, antimalarialmedications, sulfa medications, and acetaminophen), portal hypertension,

161SEPSIS AND CHOLESTASIS

or neoplasm can increase the sequestration and phagocytosis of erythrocytes[75,78].

Immunologically mediated red cell injury is another mechanism by whichhemolysis may occur. Overall, infections account for approximately 8% ofcases of autoimmune hemolytic anemia and approximately 27% of suchcases in children [79]. Immunologically mediated hemolysis may developby three mechanisms: antibody directed to red cell antigens (IgM or IgG me-diated), antigen/antibody complexes, or polyagglutination [80]. IgM anti-bodies give rise to intravascular hemolysis, and IgG antibodies give rise toextravascular hemolysis [79]. Several pathogens (eg, Mycoplasma pneumo-niae and Legionella) may cause a cold agglutinin-associated hemolyticanemia [79]. The cold agglutinins, often IgM, bind to the red cell at low tem-peratures, fix complement, and cause intravascular hemolysis. On the otherhand, IgG antibodies (eg, Donath-Landsteiner antibodies in paroxysmalcold hemoglobinuria) often cause extravascular hemolysis. This conditionhas been associated with upper respiratory tract infections and various in-fections that normally do not lead to sepsis (eg, syphilis, varicella, EpsteinBarr, measles and mumps) [79,80].

In subjects with underlying red cell defects, such as glucose-6-phosphatedehydrogenase (G6PD) deficiency [81], the threshold for hemolysis is oftenlower than in normal individuals. G6PD is required for regeneration ofnicotinamide adenine dinucleotide dehydrogenase (NADPH), which isessential for reducing oxygen radicals. In the absence of G6PD, red cellNADPH stores are diminished, which lowers the threshold for oxidantstress-mediated cell injury. Sepsis is often associated with an oxidant stress,which may induce hemolysis, particularly in patients with a lowered thresh-old for oxidant-mediated injury.

Clinical presentation

The jaundice of sepsis can occur within a few days of the onset of bacter-emia and may even appear before the other clinical features of the underly-ing infection become apparent [82]. In the absence of intra-abdominalinfection, abdominal pain is rare. Similarly, pruritus is not a major manifes-tation of cholestasis associated with infection. Hepatomegaly is present inapproximately half the cases [82]. Conjugated hyperbilirubinemia in therange of 2 to 10 mg/dL is often seen, although sometimes higher levelscan be seen. The serum alkaline phosphatase levels are usually elevatedbut rarely above two to three times the upper limit of normal, and serumtransaminase levels are generally only modestly elevated [82]. Histologically,the most prominent feature of sepsis-associated cholestasis is intrahepaticcholestasis [83], which is accompanied with Kupffer cell hyperplasia, mono-nuclear cell infiltrates in the portal tract, and focal hepatocyte dropout.Liver biopsy is seldom required to diagnose sepsis-associated cholestasis,however.

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Specific clinical scenarios of infection and jaundice

Bile duct disease

Obstruction or infection of the biliary tree should be considered as a po-

tential cause of jaundice, especially when a patient presents with right upperquadrant pain and fever. Cholangitis most commonly occurs secondary toobstruction of the biliary tree with gallstones or after biliary intervention.Less common causes are neoplastic ampullar, biliary, or pancreatic lesions.Laboratory results reveal leukocytosis, conjugated hyperbilirubinemia,and elevation of alkaline phosphatase, which is disproportionate totransaminasemia.

Liver abscess

Biliary tract disease is the most commonly associated condition with liver

abscess [84]. Another potential cause of pyogenic abscess is spread throughthe portal vein from an intra-abdominal primary site to the liver. Almostone third of liver abscesses are cryptogenic [85]. Patients present with fever,chills, and weight loss. Abdominal complaints most often are vague orabsent, and hepatomegaly is present in up to two third of patients. Alkalinephosphatase levels are invariably elevated with less frequent elevation of bil-irubin and transaminases. Optimal treatment includes prompt diagnosis,percutaneous or surgical drainage of the abscess, and broad-spectrum en-teric antibiotic coverage.

Pneumonia

The male-to-female ratio of patients who develop jaundice with pneumo-

coccal pneumonia is 10:1 [86]. It is believed that pneumonia-associatedjaundice is caused by hepatocellular damage, which is evident from the ob-servation that many patients with pneumonia, with or without jaundice,have patch hepatic necrosis [74,87].

Infants

Cholestasis is a known complication of gram-negative bacterial infection,

especially in infants and especially in the neonatal period. It accounts for asmuch as one third of the cases with neonatal jaundice. Most infants haveevidence of gram-negative bacteremia with E coli [74,88]. The urinary tractseems to be is the most common site of infection [88]. The manifestations ofthe underlying infection usually dominate the presentation.

Typhoid fever

Typhoid or enteric fever is an acute systemic illness caused by Salmonella

typhi, which causes jaundice and liver injury [74,89]. Hepatomegaly occursin approximately 30% of patients, and jaundice occurs in approximatelyone third of these cases. Alkaline phosphatase levels are usually elevatedtwo- to threefold, and serum transaminases are rarely elevated more than

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fivefold [74]. Hepatic damage seems to be mediated by endotoxin or mayoccur by local release of cytotoxins or local inflammatory reactions withinreticuloendothelial cells [90].

Evaluation of infected patients with jaundice

The guiding principles in the evaluation of a given patient include (1) con-sideration of the differential diagnosis, (2) consideration of specific diagno-ses that are likely to have a negative impact on the subject if missed, and (3)consideration of the therapeutic options available when a diagnosis can bemade. The outcome of sepsis-associated jaundice is linked to the effectivetreatment of sepsis. When jaundice develops in a patient with an establisheddiagnosis of infection, the possibility of sepsis-related jaundice is obvious.On the other hand, a high index of suspicion is often necessary to diagnosethis condition when jaundice is the presenting manifestation of infection.The presence of hyperbilirubinemia and abnormal hepatic parametersmay draw attention from assessing a more serious underlying disease pro-cess and lead to an unnecessary search for hepatic or biliary disease. If a sep-tic source is not known, however, the possibility of hepatic or biliaryinfection as a cause of jaundice also should be considered. Many specific en-tities require special attention.

In light of the common causes of jaundice and the different circumstancesin which it is encountered, a thorough, systematic approach should be car-ried out to evaluate the cause (Box 1). Box 2 lists various causes included inthe differential diagnosis in this setting. The type of jaundice (ie, unconju-gated versus conjugated and isolated hyperbilirubinemia versus jaundicewith liver enzyme abnormalities) provides valuable clues that should guidefurther evaluation. The finding of unconjugated hyperbilirubinemia should

Box 1. Evaluation of patients with jaundice

Assess the type of hyperbilirubinemiaunconjugated hyperbilirubinemia: search for hemolysisconjugated hyperbilirubinemia: search for hepatobiliary cause

(ultrasound, CT)isolated hyperbilirubinemia versus hyperbilirubinemia with

elevated liver enzymes

Evaluate for infection by obtaining the following:complete blood count with differentialurine analysiscultures: blood, urine, sputum, catheter tips, drainsimaging studies: chest radiograph, further imaging of potential

sites of infection

Box 2. Etiology of jaundice

Biliary tract diseasecholecystitischolangitis: stent obstruction, postbiliary intervention

Liver disease 9hepatitisliver abscess

Systemic infectionpneumoniaurinary tract infectionother sites of primary infectionbacteremia, septicemia

Hemolysisspecific infectionsdrugs

Drugsacetaminophenantibiotics

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initiate a search for hemolysis and potential causes of hemolysis. On theother hand, when a predominantly cholestatic jaundice is present, it isimperative to exclude a potentially treatable hepatobiliary cause of sepsisand jaundice. Imaging studies to evaluate the hepatobiliary tract are valu-able for this purpose. Sonography is relatively inexpensive and can be per-formed at the bedside in critically sick patients. Doppler sonography canexclude vascular occlusion as a cause of jaundice. Sonography is not sensi-tive enough to pick up small abscesses, however, and a CT scan should beperformed when a hepatic abscess is suspected.

In patients at risk for sepsis who develop jaundice without other featuresof infection, blood cultures, urine cultures, and a chest radiograph should beobtained as a minimum evaluation to exclude sepsis. Cultures also should besent from intravascular catheter tips, drains, or any other source of potentialinfection. If there is still no obvious cause, further aggressive evaluation forunderlying infection or iatrogenic causes should be sought. There are nocontrolled data to either validate or refute the use of empiric antibiotic cov-erage in all patients with jaundice who have not yet shown other features ofinfection. Frequently, in patients who are likely to be unable to tolerate sep-sis, empiric antibiotic coverage with a broad-spectrum antibiotic is used.Hepatic parameters should be followed closely. These parameters usuallyimprove within 1 to 2 weeks after therapy of the underlying infection.

165SEPSIS AND CHOLESTASIS

Hepatocellular jaundice is diagnosed when hyperbilirubinemia is accom-panied by high AST and ALT levels and only modest or no elevation ofalkaline phosphatase, which is usually caused by ischemia, toxins, viralinfection, or iatrogenic injury. Hepatitis viral serologic testing should bedone. An acetaminophen level may be obtained if this drug has been usedto treat fever associated with infection. Typically, the ALT levels are mark-edly elevated in such cases. The passage of biliary sludge sometimes may beassociated with rapid rise in AST levels that decline just as rapidly after pas-sage of the sludge. A sonogram can be used to confirm the presence ofsludge.

Management of critically ill patients with sepsis-associated cholestasis

The most challenging part of management is the timely discrimination be-tween sepsis-associated causes of cholestasis and other causes of cholestasisand hyperbilirubinemia that are unrelated to sepsis (Table 1). Some of themost important aspects of treatment of sepsis-associated cholestasis areoutlined.

Antibiotics

The only effective treatment of cholestasis of sepsis is the appropriatemanagement of the underlying infection. The primary site of infection ismost often intra-abdominal, but other types of infection, such as urinarytract infection, pneumonia, endocarditis, and meningitis, have been con-nected with sepsis-associated cholestasis. Appropriate antibiotic therapyshould be initiated as soon as possible because the window of opportunityfor successful intervention is short. If there is a delay in diagnosing infection

Table 1

Differential diagnosis of sepsis-associated jaundice in critically ill patients

Cause of jaundice Clues

Ischemic hepatitis Episode of hypoxemia (shock), right-sided heart

failure, hemodynamic instability, rapid onset, high

aminotransferases

Drugs Fever, pruritus, arthralgias, skin rush,

lymphadenopathy, eosinophilia

Total parenteral nutrition Usually takes weeks to develop, short-bowel

Hemolysis Multiple blood transfusions

Acalculous cholecystitis Thickened gallbladder wall, prolonged total

parenteral nutrition, major surgery, burns,

immunocompromised or diabetic patients

Hepatic abscess Right upper quadrant pain, fever, hepatic mass

Secondary sclerosing cholangitis Weeks after trauma, shock or severe burns, bile duct

strictures

166 FUCHS & SANYAL

and initializing antibiotic therapy, the prognosis is significantly worsened.The following recommendations can be made [5]:

1. Antibiotic therapy should be started as soon as sepsis has been diag-nosed and appropriate cultures have been obtained.

2. Initial empirical anti-infective therapy should include one or more drugsthat have activity against the likely pathogens and penetrate into thepresumed source of sepsis. The choice of drugs should be guided bythe susceptibility patterns of micro-organisms in the community andin the hospital.

3. Current recommendations for antibiotics include carbapenems, third- orfourth-generation cephalosporins, and extended-spectrum carboxypeni-cillins or ureidopenicillins combined with ß-lactamase inhibitors. Anti-biotics that are excreted into bile (eg, ceftriaxone, mezlocillin) shouldbe avoided or used at a reduced dose.

4. Monotherapy is as efficacious as combination therapy with a b-lactamand an aminoglycoside as empirical therapy.

5. Modification of empirical antimicrobial therapy with the aim to restrictthe number of antibiotics and narrow the spectrum of antimicrobialtherapy is an important and responsible strategy for minimizing the de-velopment of resistant pathogens and containing costs.

6. The antimicrobial regimen always should be reassessed on the basis ofmicrobiologic and clinical data with the aim to use a narrow-spectrumantibiotic to prevent the development of resistance, reduce toxicity,and reduce costs. Once a causative pathogen is identified, there is noevidence that combination therapy is more effective than monotherapy.The duration of therapy typically should be 7 to 10 days and should beguided by clinical response.

Under appropriate antibiotic therapy, cholestasis resolves. Persistent orincreasing hyperbilirubinemia indicates ongoing or inadequately treatedinfection.

Source control

In addition to antibiotic treatment, source control by means of removing

or draining septic foci is also a priority in the management of patientswith sepsis-associated cholestasis [91]. For patients with cholecystitisand cholangitis, source control options include percutaneous cholecystos-tomy, decompression of the biliary tree by endoscopic retrograde cholangio-pancreatography with papillotomy, and nasobiliary or transhepaticdrainage.

Hemodynamic resuscitation

To combat circulatory abnormalities in response to proinflammatory

cytokines and other mediators of the septic cascade, it is mandatory that re-suscitative efforts not be delayed until the patient is admitted to the intensive

167SEPSIS AND CHOLESTASIS

care unit. This approach may help to restore organ perfusion before thetransition from reversible to irreversible cellular dysfunction occurs and pre-vent organ failure or death. Resuscitation is guided by central venous oxy-gen saturation, central venous pressure, mean arterial pressure, and urineoutput and is achieved by administration of fluids, vasopressors, dobut-amine, and, if necessary, packed red blood cell transfusion [92].

Glycemic control

Hyperglycemia is common among critically ill patients with sepsis and

occurs in patients without a history of diabetes mellitus. Insulin therapythat aims at normalizing blood glucose levels has been shown to reduce mor-tality in patients with sepsis-induced organ failure [93].

Glucocorticoid therapy

High levels of inflammatory cytokines in patients with sepsis can directly

inhibit cortisol synthesis [94]. Excessive inflammatory cytokines producedduring sepsis also can result in systemic or tissue-specific corticosteroid re-sistance [95]. Relative adrenal insufficiency, in which cortisol levels, al-though possibly elevated in absolute terms, are insufficient to control theinflammatory response in septic shock [95], is present in more than 50%of mechanically ventilated patients with septic shock. Low-dose corticoste-roid replacement could significantly reduce mortality and time on vasopres-sors [96]. Low-dose corticosteroids in septic shock have been associated withattenuation in markers of inflammation, including IL-6, IL-8, IL-10, andsoluble TNF receptors, whereas other proinflammatory markers, such asIL-12, were increased [97]. Corticosteroids also may be vital in overcomingtissue-specific corticosteroid resistance [95]. Reducing the inflammatory re-sponse while avoiding significant immunosuppression seems to be associatedwith improved patient outcome.

Nutrition

Fasting has several metabolic and endocrine consequences on intestinal

and liver function. Levels of gastrointestinal hormones are reduced in pa-tients who are not being enterally fed [98]. In the setting of sepsis-associatedcholestasis in critically ill patients, total parenteral nutrition can have severalconsequences, including intestinal stasis with bacterial overgrowth andtranslocation and reduced gallbladder contractility with development ofgallbladder sludge, all of which can potentially aggravate sepsis and chole-stasis. There is general consensus that enteral nutrition should be preferredto parenteral nutrition when the gut is considered to be adequately function-ing and that enteral nutrition should be started as early as possible [99].

Renal replacement therapy

Renal replacement therapy aims at purifying the circulation of bacterial

products and inflammatory mediators, such as cytokines. To date there is

168 FUCHS & SANYAL

not enough clinical evidence to support the use of renal replacement therapyin the setting of sepsis alone [100]. In patients with sepsis-induced acute re-nal failure, however, renal replacement therapy is indicated [101].

Extracorporeal liver support

Support devices such as the Molecular Adsorbents Recirculating System

have been used in patients with sepsis and jaundice [102]. Until controlledstudies that demonstrate effectiveness and safety are available, their use can-not be recommended.

Summary

Extrahepatic infections and sepsis are commonly associated with jaundiceand cholestasis, respectively. The clinical presentation varies according tothe severity of bacterial infection. Treatment focuses mainly on eradicatingunderlying infection and managing sepsis. In the past decade, substantialprogress has been made in our understanding of sepsis-associated cholesta-sis. Identifying the molecular mechanisms underlying liver injury and chole-stasis should aid in the development of targeted therapies for cholestasis.The future will show whether such interventions may favor reversiblechanges in the biliary tree over chronic bile duct destruction in sepsis-associated cholestasis.

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