Liver disease in cystic fibrosis: A prospective study on incidence, risk factors, and outcome

A single centre experience of liver disease in adults with cystic fibrosis 1995-2006

BACKGROUND

Liver disease is an important cause of death in adults with cystic fibrosis (CF). Ursodeoxycholic acid (UDCA) may slow progression. Managing varices and timely evaluation for liver transplantation are important.

METHODS

Adults with CF underwent annual review. Abnormalities of liver function tests or ultrasound prompted referral to the CF/liver clinic where UDCA was commenced. Endoscopic surveillance for varices was undertaken if ultrasound suggested portal hypertension.

RESULTS

154 patients were followed for a median 5 years. 43 had significant liver disease, 29 had cirrhosis with portal hypertension and 14 had ultrasound evidence of cirrhosis without portal hypertension. All started UDCA. Only one patient developed chronic liver failure and none required liver transplantation. 27 underwent endoscopy; 1 required variceal banding, the others had insignificant varices. Ultrasound was normal in 97 patients while five had steatosis; nine further patients had splenomegaly but no other evidence of portal hypertension. Neither spleen size nor platelet count correlated with portal hypertension.

CONCLUSIONS

Liver disease was common in adults with CF but disease progression was rare. Thus liver disease detected and closely monitored in adults appeared to have a milder course than childhood CF. Splenomegaly, unrelated to portal hypertension may be a consequence of CF.

Cyclic AMP regulates bicarbonate secretion in cholangiocytes through release of ATP into bile

BACKGROUND & AIMS

Bicarbonate secretion is a primary function of cholangiocytes. Either adenosine 3',5'-cyclic monophosphate (cAMP) or cytosolic Ca(2+) can mediate bicarbonate secretion, but these are thought to act through separate pathways. We examined the role of the inositol 1,4,5-trisphosphate receptor (InsP3R) in mediating bicarbonate secretion because this is the only intracellular Ca(2+) release channel in cholangiocytes.

METHODS

Intrahepatic bile duct units (IBDUs) were microdissected from rat liver then luminal pH was examined by confocal microscopy during IBDU microperfusion. Cyclic AMP was increased using forskolin or secretin, and Ca(2+) was increased using acetylcholine (ACh) or adenosine triphosphate (ATP). Apyrase was used to hydrolyze extracellular ATP, and suramin was used to block apical P2Y ATP receptors. In selected experiments, IBDUs were pretreated with short interfering RNA (siRNA) to silence expression of specific InsP3R isoforms.

RESULTS

Both cAMP and Ca(2+) agonists increased luminal pH. The effect of ACh on luminal pH was reduced by siRNA for basolateral (types I and II) but not apical (type III) InsP3R isoforms. The effect of forskolin on luminal pH was reduced by a cystic fibrosis transmembrane conductance regulator (CFTR) inhibitor and by siRNA for the type III InsP3R. Luminal apyrase or suramin blocked the effects of forskolin but not ACh on luminal pH.

CONCLUSIONS

Cyclic AMP-induced ductular bicarbonate secretion depends on an autocrine signaling pathway that involves CFTR, apical release of ATP, stimulation of apical nucleotide receptors, and then activation of apical, type III InsP3Rs. The primary role of CFTR in bile duct secretion may be to regulate secretion of ATP rather than to secrete chloride and/or bicarbonate.

Laboratory parameter profiles among patients with cystic fibrosis

BACKGROUND

Clinical trials in cystic fibrosis (CF) currently use laboratory-specific reference ranges to evaluate chemistry and hematology measurements. Laboratory-specific normal reference ranges may not accurately reflect what is abnormal but clinically insignificant among CF patients.

METHODS

To address this concern, data from the Phase III trial of inhaled tobramycin in CF patients was used to describe the distribution and variability of laboratory parameters. The laboratory specimens were analyzed at a central laboratory after being obtained at baseline and throughout the 24-week trial.

RESULTS

At the time of entry into the clinical trial, 91% (463 of 508) of patients had at least a single value outside the normal range. Liver function tests (AST, ALT) were above the normal range in 16% and 12% of the patients respectively, with 2.4% of patients having an AST>2.0 times the upper limit of normal. Of the 243 patients on placebo, 242 (99.6%) had at least one laboratory parameter that changed from normal to abnormal during the 24-week follow-up period. Of those same placebo patients, 11.5% (N=28) had a laboratory parameter change from a Common Toxicity Criteria (CTC) grade 0 to grade 2 or higher during follow-up.

CONCLUSIONS

Patients with CF frequently have laboratory values outside the normal range and have significant longitudinal variability of laboratory values. Interpretation of adverse events in the clinical trial setting may be complicated by the underlying high rates of some laboratory abnormalities in the CF population. This data was presented in poster format at the American Thoracic Society International Conference, Atlanta, USA, 2002, appearing subsequently in the Conference proceedings [Goss CH, Mayer-Hamblett N, Yunker A, Waltz DA, Kronmal RA, Ramsey BW. Laboratory parameter profiles among patients with cystic fibrosis. Am J Rep Crit Care Med 2002;165(8):A283].

Liver disease in cystic fibrosis

Liver involvement in Cystic Fibrosis (CF) is much less frequent than both pulmonary and pancreatic diseases that are present in 80-90% of CF patients; liver disease (LD) affects only one third of CF patients, however, because of the decreasing mortality from extrahepatic causes, its recognition and management is becoming a relevant clinical issue. Recent observations suggest that clinical expression of LD in CF may be influenced by genetic modifiers; their identification is an important issue because it may allow recognition of patients at risk for the development of LD at the time of diagnosis of CF and early institution of prophylactic strategies. Oral bile acid therapy, aimed at improving biliary secretion in terms of bile viscosity and bile acid composition, is currently the only available therapeutic approach for CF-associated LD. However, the impact of this therapy on the natural history of LD remains to be defined and long-term effectiveness on clinically relevant outcomes should be further investigated. Liver transplantation should be offered to CF patients with progressive liver failure and/or with life-threatening sequelae of portal hypertension, who also have mild pulmonary involvement that is expected to support long-term survival. The 1-year survival rate after transplantation in CF patients is approximately 80%, with beneficial effects on lung function, nutritional status, body composition and quality of life in most cases.

Variceal hemorrhage and cystic fibrosis: outcomes and implications for liver transplantation

Autopsy and imaging studies show that liver involvement is common in cystic fibrosis. However, complications of chronic liver disease including portal hypertension and variceal bleeding are infrequently encountered, and the degree to which variceal hemorrhage affects prognosis in cystic fibrosis is unclear. This uncertainty has lead to debate as to whether liver transplantation is indicated in these patients. We describe a case series of 18 patients and compare their survival with a control group of cystic fibrosis patients without liver disease. The median age at first bleed was 20.0 years (range 9.7-30.9). The median survival after first bleed was 8.4 years, compared to 13.0 years in the control group (P = 0.15). A total of 14 patients have died, 9 from respiratory disease with no discernable contribution from their liver disease. Liver disease contributed to 4 deaths. Only 1 patient suffered a fatal hemorrhage, which may have been either variceal or bronchial in origin. Long-term survival is a frequent occurrence in patients with cystic fibrosis who suffer variceal hemorrhage, and age at death is comparable to the general cystic fibrosis population. In conclusion, this suggests that liver transplantation is not indicated in these patients without additional features of liver decompensation.

Activation of CFTR by ASBT-mediated bile salt absorption

In cholangiocytes, bile salt (BS) uptake via the apical sodium-dependent bile acid transporter (ASBT) may evoke ductular flow by enhancing cAMP-mediated signaling to the cystic fibrosis transmembrane conductance regulator (CFTR) anion channel. We considered that ASBT-mediated BS uptake in the distal ileum might also modulate intestinal fluid secretion. Taurocholate (TC) induced a biphasic rise in the short circuit current across ileal tissue, reflecting transepithelial electrogenic ion transport. This response was sensitive to bumetanide and largely abrogated in Cftr-null mice, indicating that it predominantly reflects CFTR-mediated Cl- secretion. The residual response in Cftr-null mice could be attributed to electrogenic ASBT activity, as it matched the TC-coupled absorptive Na+ flux. TC-evoked Cl- secretion required ASBT-mediated TC uptake, because it was blocked by a selective ASBT inhibitor and was restricted to the distal ileum. Suppression of neurotransmitter or prostaglandin release, blocking of the histamine H1 receptor, or pretreatment with 5-hydroxytryptamine did not abrogate the TC response, suggesting that neurocrine or immune mediators of Cl- secretion are not involved. Responses to TC were retained after carbachol treatment and after permeabilization of the basolateral membrane with nystatin, indicating that BS modulate CFTR channel gating rather than the driving force for Cl- exit. TC-induced Cl- secretion was maintained in cGMP-dependent protein kinase II-deficient mice and only partially inhibited by the cAMP-dependent protein kinase inhibitor H89, suggesting a mechanism of CFTR activation different from cAMP or cGMP signaling. We conclude that active BS absorption in the ileum triggers CFTR activation and, consequently, local salt and water secretion, which may serve to prevent intestinal obstruction in the postprandial state.

Advanced hepatocellular carcinoma associated with cystic fibrosis

Advances in the treatment of the respiratory complications of cystic fibrosis, including the availability of lung transplantation have led to a greater awareness of the manifestations of liver disease in up to 40% of patients with Cystic Fibrosis (CF). We report the case of an 18 year old female with CF who presented with advanced hepatocellular carcinoma and no prior clinical evidence of chronic liver disease. Hepatocellular carcinoma is usually the most severe manifestation of advanced cirrhosis although its development in non-cirrhotic cases of chronic liver disease has been reported. With the increasing life expectancy of CF patients it is likely that more unusual hepatic complications of this disease may be identified. Greater awareness may perhaps lead to earlier diagnosis in those at risk.

Update on cystic fibrosis epidemiology

PURPOSE OF REVIEW

With the improving survival of cystic fibrosis (CF) patients, the clinical spectrum of this complex multisystem disease continues to evolve. Epidemiologic studies have provided important insight into the disease course, prognosis, and complications. This review summarizes recent advances in our understanding of predictors of survival and outcome and modifiers of disease in CF. This review is not meant to be comprehensive, but highlights selected studies, many of which have particular relevance to the growing number of older CF patients.

RECENT FINDINGS

Survival rates of US CF patients improved remarkably over the past 15 years, but most of the improvement was limited to patients 2 to 15 years of age. Both median household income and ambient air pollutants were found to be important modifiers of disease, echoing research reported in other chronic lung diseases. Genotype classified according to functional mutation class was highly associated with outcome (class I, II, and III mutations were associated with the highest mortality). Of the emerging pathogens, B. cepacia complex and B. gladioli are the most prominent. A small but significant percentage of patients have been shown to acquire new B. cepacia complex or B. gladioli strains with time.

SUMMARY

Epidemiologic research in cystic fibrosis continues to inform patient care and clinical research, and to generate new hypotheses regarding pathophysiology. Survival and outcomes continue to improve in this multisystem disease. With continued improving survival, epidemiologic studies will be critical to tracking changes in prognosis and outcome.

Phenotypic expression of genotype-phenotype correlation in cystic fibrosis patients carrying the 852del22 mutation

Currently, more than 1,000 mutations have been identified in the cystic fibrosis transmembrane regulator (CFTR) gene. While some mutations are common worldwide, the majority are restricted in certain ethnic groups. We have found that in Southern Italy, the 852del22 mutation is well represented with a frequency of 3.5%. We have screened, by reverse dot blot, denaturing gradient gel electrophoresis (DGGE), and gene sequencing, the entire coding regions of CFTR gene in 371 consecutive cystic fibrosis (CF) patients from Southern Italy and have identified 17 patients carrying rare genotypes, among which 13 [6 M; median age 21.7 years (range: 4.5-47.7 years)] carry the 852del22 mutation. To assess the phenotypic expression of CF in patients with the 852del22 mutations we have compared these patients with a group of age and gender matched patients homozygous for the DeltaF508 mutation [n = 34; 19 M; median age 19.9 years (range: 3.8-34.6 years)]. Overall, we found no difference in terms of complications, patient survival (17.6% vs. 30.7%; P = NS), estimated time needed to develop a severe lung disease (22.1 vs. 24.5 years; P = NS), nutritional status, and rate of infection or colonization by most common pathogens between patients in the two groups. Finally, we have found that a late diagnosis was associated with a poor outcome (severe lung disease) regardless of genotype. Our data show that 852del22 mutation results in a phenotypic expression of disease as severe as that determined by the more typical DeltaF508 and, as in the latter case, there is no strict genotype/phenotype correlation.

Carbohydrate 19-9 antigen is not a marker of liver disease in patients with cystic fibrosis

Serum concentration of carbohydrate 19-9 antigen (CA 19-9), a sensitive marker of pancreatic cancer and cholangiocarcinoma, increases in a variety of liver diseases due to higher production and release by bile duct cells. Biliary epithelial cells are primarily affected in liver disease associated with cystic fibrosis (CF), which develops in up to 30% of CF patients. Our aim was to evaluate the usefulness of serum CA 19-9 concentration as a test of liver involvement in CF. Serum concentration of CA 19-9, liver enzymes, bile acids, and total amylase was determined in 107 CF patients (49 with and 58 without liver disease) and 56 healthy subjects. Serum CA 19-9 concentration was significantly higher in CF patients (67 U/ml, 95% CI 53.5-80.5 U/ml) than in controls (11.8 U/ml, 95% CI 2.5-44 U/ml; p < 0.001) and in CF patients with liver disease (92.3 U/ml, 95% CI 75-109.5 U/ml) compared to CF patients without liver disease (46.6 U/ml, 95% CI 27.8-65.4 U/ml; p < 0.001). In CF patients, stepwise logistic regression analysis identified alanine aminotransferase, gamma-glutamyltranspeptidase, amylase, and CA 19-9 as the most useful predictors of liver disease (p < 0.0001). Receiver-operating characteristic (ROC) curve analysis revealed gamma-glutamyltranspeptidase and CA 19-9 as the best tests for identification of liver disease in CF patients; at a CA 19-9 cut-off arbitrarily fixed at 73 U/ml, positive and negative predictive value was 70% and 78%, respectively (sensitivity 57%, specificity 81%). To increase sensitivity to 94%, the cut-off had to be fixed at 31 U/ml, which corresponds to a specificity of only 36.2% (predictive value 33%). Our study indicates that measurement of the serum CA 19-9 concentration alone cannot be proposed as a reliable test of early hepatic involvement in CF.