Serum Bile Acid: an Alternative Liver Function Marker in the

ORIGINAL ARTICLE
Serum Bile Acid: an Alternative Liver Function Marker
in the Obstructive Jaundice Patient
Toar J.M. Lalisang, Marzuki Suryaatmadja
Department of Surgery, Faculty of Medicine, University of Indonesia – Cipto Mangunkusumo Hospital.
Jl. Diponegoro no. 71, Jakarta 10430, Indonesia. Correspondence mail: [email protected], [email protected].
ABSTRAK
Tujuan: untuk mengkonfirmasi peran asam empedu sebagai petanda tunggal untuk fungsi hati bila
dibandingan dengan pemeriksaan klasik fungsi hati pada pasien dengan ikterus. Metode: studi sebelum dan
sesudah terhadap pasien dengan ikterus dilakukan dari Desember 2007 – Januari 2009. Petanda fungsi hati
diukur sebelum, pada hari ke-7 dan hari ke-14 setelah dekompresi saluran empedu (DSE). Koleksistektomi
terbuka, sebagai teknik dekompresi saluran empedu, menjadi model untuk mengobservasi perubahan petanda.
Subjek studi di kumpulkan oleh tenaga medis profesional dan menggunakan Autometed clinical chemestry
analyzer (ACA) TRX 7010 untuk mengukur nilai petanda. Semua data berkesinambungan di presentasikan
sebagai rerata (SD) dan variabelnya di bandingkan serta dianalisa dengan t-test. Pengukuran data jamak
menggunakan SPSS v.16 dengan nilai p<0.05 dianggap signifikan secara statistik. Hasil: dua puluh satu pasien
masuk dalam studi ini. Semua pasien mengalami akumulasi asam empedu dan peningkatan hasil laboratorium
fungsi hati konvensional. Setelah dekompresi, nilai rata-rata serum asam empedu menurun secara signifikan
(p<0.05). Penurunan signifikan juga terjadi pada total bilirubin serum (p<0.05) dan alkaline fosfatase (ALP)
serum (p<0.05). Terdapat juga kecenderungan perbaikkan pada fungsi koagulasi yang dibuktikan dengan
pemendekan protrombine time (PT) dan activated partial thromboplastin time (APTT). Kadar albumin sedikit
meningkat dari 2.8 menjadi 2.9 mg/dL sementara aktifitas cholinesterase (CHE) rendah secara konstan.
Penurunan aktifitas rata-rata dari aspartate transaminase (AST) (p<0.05) dan alcaline transferase (ALT)
juga di observasi. Kesimpulan: kadar asam empedu serum mengikuti perubahan petanda klasik fungsi hati.
Asam empedu serum dapat digunakan sebagai alternatif petanda tunggal dalam evaluasi fungsi hati, dimana
pemeriksaannya sederhana dan mampu laksana.
Kata kunci: asam empedu, bilirubin, fungsi hati.
ABSTRACT
Aim: to confirm the role of bile acid value as single marker for liver function test as compared to the
conventional liver function tests on obstructive jaundice patients. Methods: before and after study on severe
obstructive jaundice patients was performed from December 2007 until January 2009. The liver function markers
were measured before, 7th day and 14th day after bile duct decompression (BDD). Open Cholecystostomy
as BDD was used as a model to observe the markers changes. Samples were collected by trained medical
professionals and Automated clinical chemistry analyzer (ACA) TRX 7010 was used to measure the markers
value. All continuous data were presented as mean (SD) and the variables were compared and analyzed by t-test
and multiple measurements test using SPSS v.16 with a p-value of < 0.05 considered to be statistically significant.
Results: twenty one patients were included. All patients suffered bile acid accumulation and impairment of all
conventional liver functions tests. After decompression, the average serum bile acid decreased significantly
(p<0.05). Significant decrease after decompression happened to serum total bilirubin (p<0.05) and serum ALP
(p<0.05). A trend towards improvement in coagulation function was evident by the shortening of PT and APTT.
The albumin level increased slightly from 2.8 to 2.9 mg/dL while CHE activity was fixed at low level. A decrease
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Toar J.M. Lalisang
Acta Med Indones-Indones J Intern Med
in average activity of transaminase enzyme (AST (p<0.05) and ALT) was also observed. Conclusion: the sBA
level follow the pattern of changes of classic liver function markers. Serum bile acid could be considered to be
used as alternative marker to evaluate liver function, which is simple and applicable.
Key words: bile acid, bilirubin, liver function.
INTRODUCTION
Since 1970, serum bile acids (sBA) has been
recognized as the only index which is able to
simultaneously assess the liver function such
as liver cells integrities, excretion, synthesis,
and metabolic activities.1 Bile acid (BA) is
end product of cholesterol which was mostly
metabolized in the liver cells and excreted to
bile in bile duct as bile fluids and then enters the
entro-hepatic circulation and then pooled in the
liver.1,2 That role, however, has been abandoned
for the last five decades due to the complexity
of its assay method and less popular among
physician in clinical work.3
Sensitivity and specificity of sBA to assess
liver function had been demonstrated by several
studies in the last decade.3-7 Advance understanding
of the cellular and molecular pathophysiology of
sBA has been rapidly led to a better knowledge
of hepatocyte injury, which became the point of
liver function measurement.6,8,9
Inaccurate understanding and the shortage
of bile acid assay has made the role of sBA
as a liver function test forgotten. Nowadays,
modern assay equipment is already available
and, therefore, bile acid assay is more feasible
to be performed. We aimed to confirm the role of
sBA compared to the conventional liver function
tests on obstructive jaundice patients after BDD.
METHODS
A before-and-after study was done on
obstructive jaundice patients, mostly due to periampullar or Klatskin tumor with serum bilirubin
above 10 mg/dL, who were admitted to Cipto
Mangunkusumo Hospital from December 2007
to January 2009.
Patients with active Hepatitis A, B, or C, liver
malignancy, severe liver impairment with massive
ascites, had previously undergone decompression
procedure or had prior implantation of an internal
drainage device, and chronic liver failure were
excluded. The study protocols were reviewed and
approved by the Hospital Ethical Commission.
234
Bile duct decompression through an open
cholecystostomy was used as a model to observe the
marker changes. Routine laboratory investigation,
sBA, level of bile acid in the bile fluid, direct and
indirect bilirubin, alcaline phosphatase (ALP),
gamma glutamyltransferase (g-GT), albumin,
cholinesterase (CHE), protrombine time (PT),
activated partial thromboplastin time (aPTT),
aspartate transaminase (AST) and alcaline
transferase (ALT) were done before, 7 days, and
14 days after decompression procedure. Samples
were collected by trained medical professionals
and Automated clinical chemistry analyzer (ACA)
TRX 7010 was used to measure the marker values.
All continuous data were presented as mean
(SD) and the variables were compared and
analyzed by t-test and multiple measurements
test using SPSS v.16 with a p-value of <0.05
considered being statistically significant.
RESULTS
Along the study timeframe, 21 severe
obstructive jaundice patients due to mostly
Periampulary tumor acceptable to the protocol
criteria were included. Baseline characteristics
of patients included in the study are presented
in Table 1.
Table 1. Baseline characteristics of patients included in
the study
Characteristics
Sex - female/male
Age
7/14
44 (12,7)
Diagnosis
-- Peri-ampullar Malignancy
15
-- Peri-ampullar Benign Tumor
6
Routine Laboratory Examination (before
decompression)
-- Hb(g/dL)
11,2
-- Ht (%)
32,7
-- WBC( 1000/μL)
11,3
-- Platelets (1000/μl)
260
-- Ureum/Creatin(mg/dL)
35,5/0,9
-- Blood Glucose (mg/dL)
104
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Serum Bile Acid: an Alternative Liver Function Marker in the Obstructive
All the patients underwent bile duct
decompression procedure. sBA accumulation
as well as impaired liver functions occurred in
all patients.
Seven and fourteen days after decompression,
the average of sBA decreased as much as 59%
after 7 days and 87% after 14 days (before: 96.4
(53.8) μmol/L, day 7: 39.9 (39.5) μmol/L, day
14: 13 (12.6) μmol/L; p<0.05). Meanwhile, bile
acid in the bile fluid also increases as much as
30% after 7 days and 53% after 14 days (before:
987 (182) μmol/L, day 7: 1400 (182) μmol/L, day
14: 2087 (2076) μmol/L; p<0.05).
Serum total bilirubin (before: 20.0 (9) mg/
dL, day 7: 13.3 (5) mg/dL, day 14: 6.2 (4.1) mg/
dL; p<0.05) and serum ALP (before: 908 (873)
IU/L, day 7: 453 (460) IU/L, day 14: 298 (198)
IU/L; p<0.05) also decreased significantly after
decompression. After decompression procedure,
γ-GT decreased as much as 48% after 7 days
and 59% after 14 days (before: 431 (421) IU/L,
day 7: 222 (153) IU/L, day 14: 177 (96.6) IU/L;
p<0.05).
The average of albumin level increased
3% from 2.8 (0.4) mg/dL to 2.9 (0.7) mg/dL
while CHE activity was fixed at low level after
decompression, and only 3 patients reached the
normal level.
PT (before: 19.5 seconds, day 7: 14.3
seconds, day 14: 14.7 seconds) and APTT
(before: 57.5 seconds, day 7: 38.7 seconds,
day 14: 42.1 seconds) were shortened after
decompression.
After decompression procedure, activity of
AST (before: 111.8 IU/L, day 7: 110.2 IU/L,
day 14: 72.6 IU/L; p<0.05) and ALT (66.7
IU/L, day 7: 72.8 IU/L, day 14: 54.3 IU/L)
decreased. Changes in the results of laboratory
measurements are summarized in Table 2.
DISCUSSION
The liver function and volume are two
important issues to be assessed preoperatively in
order to evaluate the liver condition, especially
in living donor transplantation.10-12 There is no
diagnostic test that can exactly confirm the liver
function, even liver biopsy.2,13
The sBA value have already been suggested
as a simultaneous marker by Annoni and as a
diagnostic test for hepatobiliary diseases by
Heaton and Sardi.1,3,7 Due to the shortage of
Table 2. Changes of liver markers before, after 7 and
14 days
Markers
(normal range)
Mean (SD)
Before
Day 7
Day 14
Serum bile acid
(6-10μmol/L)*
96.4 (53.9)
39.9 (39.5)
13.0 (12.6)
Bile acid in bile
fluid*
987 (1229)
1400 (2076)
2087 (1795)
Bilirubin
(<1 mg/dL)*
20.08 (9)
13.3 (5.0)
6.2 (4.1)
ALP
(<270 IU/L)*
908 (873)
453 (460)
298 (198)
γ-GT
(5-61 IU/L)*
431 (432)
222 (153)
177 (153)
ALB
(3.4-5.0 g/dL)
2.8 (0.4)
2.8 (0.7)
2.9 (0.7)
3604 (1381)
4100 (209)
3622 (1432)
PT (12-14
seconds)
19.5 (1,4)
14.3 (1.9)
14.7 (2.8)
aPTT (25.6-35.2
seconds)
57.5 (58,5)
38.7 (8.5)
42.08 (12.5)
AST
(<38 IU/L)*
111.8 (60.6)
110.2 (101.7)
72,67 (36.0)
66.7 (60)
72.8 (78.9)
54.3 (28.7)
CHE (520012900 IU/L)
ALT (<41 IU/L)
* p<0.05
assay for sBA in the past, and negative physician
opinion, the sBA value was abandoned for many
years.
Alterations in sBA metabolism is usually the
reflection of liver dysfunction.3 The increasing
value suggests that uptake, secretion process, or
porto-veno systemic shunt has been impaired.1,14
The fasting serum bile acid level in non
cholestatic human is less then 6 -10 μmol/L.1,2,7
Sardi et al in 1987 reported the normal fasting
value of sBA was 3.4 ±1.9 μmol/L.7 In this study
the average amount of sBA pre decompression
was 94.6 μmol/L and the increment was
caused by obstruction which regurgitate or
redistribute the BA after conjugation process in
the hepatocyte back to the liver sinusoids and the
to the periphery circulation (due to tight junction
rupture).15
Bile acids are the end products of cholesterol
breakdown which takes place in the hepatocytes.2,7
It starts with the uptake of cholesterol at the liver
sinusoid and then follows the classic or alternative
pathways in the hepatocyte to be changed into
primary bile acids as secretion product.2,4,16,17
Since bile acid metabolism mostly occurs in
hepatocytes,1,7 there will be an accumulation of
235
Toar J.M. Lalisang
bile acid if there is impairment in hepatocyte
uptake, synthetic or secretion function.1,14,17
One important criterion to justify a marker
as qualitative and quantitative liver markers
is that the marker must be formed outside the
liver and passes through the liver totally without
being retained in the liver.2,18 Bile acid fulfills
that criterion. Thus, such measurement is highly
possible to be used to assess the endogenous
clearance test.
In obstructive jaundice, as also shown in this
study, the serum bile acid level will increase,
while its level in the biliary duct decreases
through absorption, regurgitation and urinary
excretion. These phenomena were proven in this
study by the high value of sBA and low value
of fluid BA before decompression and these
values inversed after BBD (Table 2). Bile duct
decompression releases the high pressure and
inhibits the activation of hepatocyte apoptosis
cascade which impact the recovery of the
hepatocyte count and functions.
In this study bile fluid BA increases after
bile duct decompression. This indicates that the
BA uptake and conjugation process at the level
of hepatocyte have already been improved. The
decrease of sBA was followed significantly by
the liver secretion markers such as bilirubin,
phosphate alkaline and γ-GT due to the same
pathways as mentioned above (Figure 1)
Serum bile acids (sBA) values decrease
along with the improvement of secretion function
as confirmed by the decrease bilirubin, alkaline
phosphate and GGT value although all those
three markers were not specific due to hepatocyte
dysfunction (Figure 1). This might be caused by
the BDD which released the intra bile duct high
pressure. Release of the accumulating pressure
then promotes the BA metabolism on hepatocyte
side. The second impact of BA break down is
that the BA accumulation was inhibited which
decreases the hepatocyte apoptosis and necrosis.8
Pattern of changes in markers of liver
synthesis, however, was not quite parallel with
changes in sBA value. This may be due to the
shortness of decompression compared to the half
life of albumin and CHE synthesis. Extra liver
factors might also influence both markers (Figure
2). According to the half life of albumin and CHE
synthesis process, the serum BA metabolism
process was more rationale and representative
as synthesis marker in short period.
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Acta Med Indones-Indones J Intern Med
100 0
10 0
10
1
Serum b ile a cid
Bilirubin
A LP
?- GT
Figure 1. Comparison of the averages of serum bile acids
level to the averages of total bilirubin level (mr/dL), ALP
activity (IU/L), and γ-GT (IU/L) in logarithmic scale.
10000
1000
100
10
1
Serum bile acid
A LB
CHE
The average of albumin level increased 3% from 2.8 (SD 0.4) to
2.9 (SD 0.7) mg/dL while CHE activity was fixed at low level after
decompression, and only 3 patients reached the normal level.
Figure 2. Comparison of the average of serum bile acids
level to albumin level and CHE activity in logarithmic scale.
The PT and APTT values which represent
synthesis function were not improved
significantly after the bile duct decompression.
These might be interpreted that the impairment
itself was not in severe state or due to the high
reserve liver function.
The prolongation of PT and APTT in
obstruction jaundice patients was impacted by
fat mal absorption, which induced vitamin K
deficiency, and not due to liver factor itself. This
study confirms that the sBA changes are followed
by improvement of extrinsic haemostatic factor
(Figure 3).
In this study the destruction of hepatocyte
was attenuated after bile duct decompression.
It was confirmed by the decreasing of AST
and ALT values, which also meant as a clue of
better functional hepatocyte to metabolize BA.
(Figure 4).
Despite the increasing knowledge of the
importance of sBA, the test on bile salts is
unfamiliar in most hospital laboratories. Even
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Serum Bile Acid: an Alternative Liver Function Marker in the Obstructive
100
10
1
Serum bile a cid
PT
A PTT
Figure 3. Comparison of the average of serum bile acids
level to PT and APTT in logarithmic scale.
1000
100
10
1
Serum bile a cid
AST
A LT
Figure 4. Comparison of the average of serum bile acids
level to AST and ALT levels in logarithmic scale.
though there are technical problems, and
shortage of assay in the past made the count
of bile acid abandoned, but these are not
beyond the ingenuity of chemical pathologists.
Nowadays in the era of high performance liquid
chromatography (HPLC) and enzymatic assay
by automated clinical chemistry analyzer (ACA)
those problems have been solved.
Our data confirmed that the functional
hepatocyte mass was improved after the bile duct
decompression, which was proven by decreasing
sBA accumulation and increasing bile fluid BA
(Table 2).
The reluctance to measure bile acids lies
not in the laboratory but in the hands of the
physicians. Most of them seem to think that they
do not need to measure bile acid concentrations
to diagnose or manage their patients adequately.
Even though it is not an absolute approach to
diagnose any important or common; our data
suggested that sBA is actually very useful in
assessing liver function.
Altered bilirubin metabolism is clinically
obvious but it has no devastating effects, except
in the neonatal period, whereas altered bile salt
metabolism accounts for the major complications
of cholestasis, including mal-absorption of fat
and vitamin K and probably pruritus. Moreover,
a raised serum bile salt concentration, especially
after a meal, is a much more sensitive indicator
of liver cell dysfunction than is a raised bilirubin
concentration.
sBA is probably as sensitive as any liver
function test and has been technically possible
for half a century. The main reason why serum
bile acids were not measured routinely may
be due to emotional rather than intellectual.
Bilirubin is visible, often dramatically; whereas
bile salts (being colorless) are unseen. Another
reason in the past is technical. The sBA assay
is more difficult than that of bilirubin, and
especially the old method requires extraction
of the serum, which is more time-consuming.3
Nevertheless, simplified novel methods are
becoming available, including enzymatic kits
and rocket method, and even techniques which
do not require extraction of serum.
The pattern of decrease in liver function
markers as found in this study is similiar to those
found in animal study,6 and in a study by Franco
et.al. which examined the sBA concentration as
liver function test in workers who occupationally
exposed to organic solvents.5 The rapid decrement
pattern occurred in the first week after the
decompression, is due to reversible hepatocyte
dysfunction. There fore, after the obstruction
has been released, the hepatocyte will be
normaly functioning again. The slow decreased
pattern needs new hepatocyte to replace the
damaged hepatocyte from apoptosis to reach
the adequate normal capacity. This finding has
suggested that the repair of hepatocyte function
is significantly followed to the inhibiton of
bile acid accumulation through biliary duct
decompression.
CONCLUSION
Serum bile acid levels follow the pattern
of changes of classic liver function markers.
Serum bile acid could be considered being used
as alternative marker to evaluate liver function,
which is simple and applicable.
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