initial large diameter of common bile duct is associated with long-term dilatation of bile duct...

Original article

Initial large diameter of common bile duct is associated withlong-term dilatation of bile duct after endoscopic extraction

of stones

Chang Whan KIM,* Jae Hyuck CHANG,* Yeon Soo LIM,† Tae Ho KIM,* In Seok LEE* & Sok Won HAN*

Departments of *Internal Medicine and †Radiology, College of Medicine, The Catholic University of Korea,Seoul, Republic of Korea

OBJECTIVE: To investigate the time and extent ofrecovery of dilated common bile duct (CBD) after theextraction of CBD stones and to identify the factorsrelated to the long-term dilatation of the CBD afterstone removal.

METHODS: Data of 329 consecutive patients under-going endoscopic extraction of CBD stones fromJanuary 2008 to December 2012 were retrospectivelyreviewed. Finally, 44 patients were enrolled in thestudy.

RESULTS: The CBD diameter significantly decreasedafter stone extraction (P < 0.001). However, the CBDdiameter in patients who were followed up for1 week and longer and <1 week did not differ signifi-cantly. The diameter decreased more in patients with

an initial CBD diameter ≥ 15 mm than in those withan initial CBD diameter <15 mm before stone extrac-tion (P = 0.007), but the normalization of dilatedCBD was less frequent in patients with a large initialCBD diameter. The factors related to the long-termdilatation of CBD (>10 mm for >6 months) wereinitial CBD diameter, the largest diameter of CBDstone and endoscopic papillary large balloon dilata-tion. Initial CBD diameter was an independent factorwith multivariate analysis (OR 1.754, P = 0.017).

CONCLUSIONS: The CBD diameter recoversrapidly after the extraction of CBD stones. An initiallarge CBD diameter before stone extraction is associ-ated with the long-term dilatation of CBD.

KEY WORDS: common bile duct, common bile duct gallstone, computed tomography, endoscopic retrogradecholangiography, magnetic resonance cholangiopancreatography.

INTRODUCTION

Normally, common bile duct (CBD) is thin with adiameter of less than 6 mm,1,2 and its wall consists

of thin elastic and smooth muscle fibrils.3,4 When theCBD is obstructed by stones, the pressure caused byretained bile makes the CBD dilate. After the extrac-tion of stones, the size of dilated CBD is expected todecrease; however, the dilatation of the CBD some-times persists. Clinicians make efforts to find out thereason why a dilated CBD does not improve orwhen and how much the dilatation of the CBDimproves after the stones are removed. Based onultrasonographic evaluation, a significant decrease inCBD diameter occurs one week after endoscopicsphincterotomy and extraction of CBD stones.4 In

Correspondence to: Jae Hyuck CHANG, Division of Gastroenterology,Department of Internal Medicine, Bucheon St Mary’s Hospital, Collegeof Medicine, Catholic University of Korea, 327, Sosa-ro, Wonmi-Gu,Bucheon 420-717, Republic of Korea. Email: [email protected]© 2013 Chinese Medical Association Shanghai Branch, ChineseSociety of Gastroenterology, Renji Hospital Affiliated to ShanghaiJiaotong University School of Medicine and Wiley Publishing AsiaPty Ltd

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Journal of Digestive Diseases 2014; 15; 35–41 doi: 10.1111/1751-2980.12100

35

another report, the CBD diameter returned tonormal in 98.3% of patients 6 months after theremoval of stones.5

Ultrasonography is a commonly used modality tomeasure the size of the CBD in almost all thestudies.1,4–8 Although it can show the overall image ofthe CBD, the largest diameter or stricture of CBDmight not be clearly demonstrated by this method.Therefore, computed tomography (CT), which hasbeen used to measure the CBD diameter in adults orpost-cholecystectomy,2 and magnetic resonancecholangiopancreatography (MRCP) are applied toshow the whole CBD structure, to find the portionwith the largest diameter and to detail any abnormali-ties of the CBD.9–12

In this study, we aimed to investigate the time andextent of recovery of dilated CBD after the extractionof stones using CT and MRCP, and to identify thefactors related to dilated CBD six months after theextraction of CBD stones.

PATIENTS AND METHODS

Patients

From January 2008 to December 2012, 329 patientswho underwent endoscopic removal of CBDstones at Bucheon St. Mary’s Hospital (Seoul, Korea),were recruited consecutively. Endoscopic retrogradecholangiopancreatography (ERCP) was performedwhen the imaging study and laboratory tests indicatedCBD stones with acute cholangitis. Among the eligiblepatients, 225 patients without imaging follow-up afterthe extraction of the CBD stones were excluded. Theenrolled patients underwent abdominal CT and/orMRCP before ERCP and during the follow-up. We alsoexcluded another 60 patients who had conditions thatmight have affected the diameter of the CBD: laparo-scopic cholecystectomy after endoscopic stone extrac-tion (n = 30), recurrent or residual CBD stones duringfollow-up (n = 12), stricture of CBD including chronicpancreatitis (n = 5), severe liver cirrhosis with ascites(n = 3), Billroth II surgery (n = 3), liver surgery (oneleft lateral segmentectomy and one right lobectomy),choledochal cyst (n = 1), periampullary perforation(n = 1), bile duct papillomatosis (n = 1), chole-dochoduodenostomy (n = 1) and Mirizzi’s syndrome(n = 1). Patient’s anonymity was preserved andthe Institutional Review Board approved this study(no. HC13RISI0028). The study protocol was in

complete compliance with the Declaration ofHelsinki, as revised in Seoul in 2008.

Endoscopic extraction of CBD stones

ERCP was performed with a duodenoscope (JF 240;Olympus, Tokyo, Japan). Two experienced gastro-enterologists who had performed more than 1000ERCP conducted the procedures. Conscious sedationof the patients was achieved with midazolamand pethidine hydrochloride. A contrast medium(iopromide) at a dilution of 1:1 was injected to obtainthe cholangiogram after the cannulation of thebile duct without papillotomy. When CBD stoneswere confirmed in the cholangiogram, endoscopicsphincterotomy or papillary balloon dilation was per-formed. The bile duct was swept with a basket andretrieval balloon catheter to remove the calculi. Endo-scopic nasobiliary drainage (ENBD) tube was insertedin all patients who had undergone endoscopic extrac-tion of CBD stones. A tubogram via the ENBD tubewas performed to confirm the absence of residualstones in the CBD 1–2 days later.

CT and MRCP

CT was performed using a 64-slice multidetector CTscanner (Somatom Sensation 64; Siemens, Erlangen,Germany) with a detector collimation of 24.0 mm ×1.2 mm, a table feed of 28.8 mm per rotation, a rota-tion time of 1 s, a tube current of 200 effective mAsand a tube voltage of 120 kVp. The pre-contrast scanranged from the diaphragm to the iliac crest and thepost-contrast scan ranged from the diaphragm to thesymphysis pubis. Altogether 120 mL contrast material(Ultravist 300, Bayer, Berlin, Germany) was injectedinto the antecubital vein with an injection rate of2 mL/s. Image acquisition was initiated after 90 s ofcontrast injection. Pre-contract and post-contrast axialimages were reconstructed in 5 mm without overlapand post-contrast coronal images by 3 mm withoutoverlap.

Magnetic resonance (MR) images were obtained withmagnetic resonance imaging (MRI) (3.0T Achieva;Philips Healthcare, Best, The Netherlands) using atorso phased-array coil. Axial T1-weighted gradient-echo images (TR/TE 10/2.3 ms, FA 15° and 7-mmslice thickness), axial T2-weighted spin-echo images(TR/TE 1741/80 ms, FA 90° and slice thickness of3 mm), coronal T2-weighted spin-echo images (TR/TE1516/80 ms, FA 90° and slice thickness of 3 mm) and

Journal of Digestive Diseases 2014; 15; 35–4136 CW Kim et al.

© 2013 Chinese Medical Association Shanghai Branch, Chinese Society of Gastroenterology, Renji Hospital Affiliated to Shanghai Jiaotong University Schoolof Medicine and Wiley Publishing Asia Pty Ltd

thick-slab MRCP images (TR/TE 10695/920 ms, FA90° and slice thickness of 40 mm) were acquired. Nocontrast media were used.

Measure of CBD diameter

CT and MRCP data sets were transferred to picturearchives and communication system workstations foranalysis. CT and MRCP images were interpreted byone radiologist who had more than 10 years of expe-riences in interpreting gastroenterological images. TheCBD diameter was measured using electronic caliperson the workstation. The largest diameter perpendicu-lar to the long axis of the CBD was regarded as repre-sentative. We chose 10 mm as the upper limit ofnormal for CBD diameter in the study population,considering the age and history of cholecystectomy ofour patients.

Statistical analysis

Statistical analyses were performed using SPSS 20(SPSS Inc., Chicago, IL, USA). Paired t-test was used tocompare the initial CBD diameter and that at the lastmeasure after stone removal. In a comparison betweenthe serial changes of CBD diameter in patients duringthe follow-up period, the Wilcoxon signed-rank testwas used. The recovery of CBD diameter after theextraction of stones based on the initial CBD diameterwas compared using ANOVA or Pearson’s χ2 test.Fisher’s exact test was used for categorical data and theMann–Whitney U test was used for continuous data.Univariate and multivariate analyses were performedwith the logistic regression analysis to determine thefactors that related to the long-term dilatation of CBDafter the extraction of stones. P ≤ 0.05 were consideredstatistically significant.

RESULTS

The characteristics of the patients

Finally, 44 patients were enrolled in the study. Thecharacteristics of the patients are shown in Table 1.The mean age of the patients was 71.4 ± 14.9 years,with a slight male predominance (54.5%). The meanfollow-up period was 14.3 ± 13.9 months (range 0.1–48.1 months). The patients underwent CT or MRCPbefore and after the extraction of the stones. Duringthe follow-up period, imaging examinations were per-formed for a general medical check-up or otherabdominal conditions. The overall numbers of CT andMRCP performed were 65 and 34, respectively. Inall, 11 patients were followed up twice with imaging

studies after the extraction of stones. All patientsunderwent endoscopic sphincteroplasty. Of these, 38patients (86.4%) underwent endoscopic sphinctero-tomy, 28 (63.6%) underwent endoscopic papillaryballoon dilatation and 22 (50.0%) underwent bothprocedures. Overall, 14 (31.8%) underwent endo-scopic large balloon dilatation (≥12 mm).

Changes in CBD diameters after the extraction ofthe stones

CBD diameters significantly decreased from12.4 ± 5.2 mm to 8.6 ± 4.1 mm after the endoscopicextraction of stones (P < 0.001, Table 1). However,changes in CBD diameters after the extraction of thestones did not differ based on the follow-up duration(P = 0.802, Table 2). There were also no significantdifferences between any two groups in the changes ofCBD diameter (P > 0.05). Therefore, the patients witha longer follow-up period did not show a significant

Table 1. Patients’ characteristics

Number of patients 44Age (years, mean ± SD) 71.4 ± 14.9Male gender, n (%) 24 (54.5)Previous cholecystectomy, n (%) 8 (18.2)Number of CBD stones (mean ± SD) 1.9 ± 1.5Size of largest CBD stone (mm, mean ± SD) 10.8 ± 5.8ES or EPBD, n (%) 44 (100)

ES 38 (86.4)EPBD 28 (63.6)ES + EPBD 22 (50.0)Endoscopic large balloon dilatation

(≥12 mm)14 (31.8)

Size of balloon dilatation (mm,mean ± SD)

13.2 ± 3.1

Imaging examinations, CT : MRCP (n) 65:34Follow-up (months, mean ± SD) 14.3 ± 13.9Initial CBD diameter (mm, mean ± SD)* 12.4 ± 5.2CBD diameter at the last follow-up

(mm, mean ± SD)*8.6 ± 4.1

Reasons for follow-up imagingexamination (n)

General medical check-up 17Abdominal pain without cholangitis 8Gallbladder stone 7Ureter stone 5Hepatoma 2Others† 5

*Initial versus the last follow up, P < 0.001.†Colon cancer, liver abscess, pancreas tail cancer, renal cell cancer,acute pyelonephritis.CBD, common bile duct; CT, computed tomography; EPBD,endoscopic papillary balloon dilatation; ES, endoscopicsphincterotomy; MRCP, magnetic resonancecholangiopancreatography; SD, standard deviation.

Journal of Digestive Diseases 2014; 15; 35–41 Diameter of CBD after stone extraction 37


improvement of their CBD diameter compared withthose with a shorter follow-up duration, and thediameters in the patients followed up for one weekand longer did not decrease further than those in thepatients followed up for less than one week.

When the initial CBD diameters before the extractionof stones were divided into four groups, that is,<10 mm, 10–14 mm, 15–19 mm and ≥20 mm, recov-ery of the CBD diameter differed significantly accord-ing to the initial CBD diameter (P < 0.001, Table 3).Recovery of the CBD diameter in patients with aninitial CBD diameter of ≥ 15 mm was greater than inthose with initial CBD diameter < 15 mm (P = 0.007).The proportion of patients with CBD dia-meters >10 mm at the last follow-up also differedaccording to the initial CBD diameter (63.6% of thepatients with an initial CBD diameter ≥ 15 mm vs9.1% of those with an initial CBD diameter < 15 mm,P = 0.001). The proportion of patients followed up formore than 6 months with CBD diameters >10 mm atthe last follow-up also differed significantly accordingto the initial CBD diameter (5 [71.4%] with an initialCBD diameter ≥ 15 mm vs 2 [8.7%] of those with an

initial CBD diameter < 15 mm, P = 0.003). The pro-portion of patients who had a previous chole-cystectomy also differed according to the differentinitial CBD diameter (P = 0.033) as chole-cystectomy had been performed more often inpatients with an initial CBD diameter ≥ 15 mm thanin those with an initial CBD diameter < 15 mm(P = 0.008).

In all, 11 patients were followed up twice withimaging studies after stone extraction (Table 4). TheCBD diameter significantly decreased at the firstfollow-up (P = 0.003), but it did not significantlychange between the first and second follow-up(P = 0.180). The CBD diameter between the first andsecond follow-up did not change in nine (81.8%) ofthese patients, and it decreased by 2 mm over 10.5months and by 1.5 mm over 16.6 months in theremaining two patients.

The factors related to long-term dilatation of CBD

The analysis of factors related to the long-term dilata-tion of CBD, defined as a CBD >10 mm more than 6

Table 2. Changes in common bile duct (CBD) diameters according to follow-up duration

Follow-up duration Change of CBD diameter* (mean ± SD)

Patients (n)

Initial CBD diameter (mm)

<10 10–14 15–19 ≥20 Total

<1 week −3.9 ± 6.1 2 1 0 1 41 week–<1 month −4.3 ± 0.3 0 2 0 0 21–<6 months −4.8 ± 2.9 3 2 3 0 86–<12 months −4.4 ± 3.3 4 6 1 1 1212–<24 months −2.7 ± 2.2 4 4 0 0 8≥24 months −3.9 ± 3.2 4 1 3 2 10

*P = 0.802. SD, standard deviation.

Table 3. Changes in common bile duct (CBD) diameters according to the initial diameter

Initial CBD diameter (mm)

P value<10 10–14 15–19 ≥20

Patients (n) 17 16 7 4Age (years, mean ± SD) 65.6 ± 19.8 76.1 ± 8.8 73.3 ± 11.8 74.3 ± 11.2 0.231Previous cholecystectomy, n (%) 3 (17.6) 3 (18.8) 5 (71.4) 2 (50) 0.033Follow-up duration (months, median [interquartile

range])11.4 (12.5) 7.4 (10.3) 11.9 (24.7) 25.8 (39.2) 0.319

Change of CBD diameter (mm, mean ± SD) −1.8 ± 1.7 −4.3 ± 2.3 −6.4 ± 3.3 −6.7 ± 5.4 <0.001CBD diameter > 10 mm at the last follow-up, n (%) 0 (0) 3 (18.8) 4 (57.1) 3 (75.0) 0.001CBD diameter >10 mm at the last follow-up

among patients followed up for >6 months, n (%)0/12 (0) 2/11 (18.2) 2/4 (50.0) 3/3 (100) 0.002

SD, standard deviation.



months after the extraction of stones, indicated thatit was associated with the initial CBD diameter(P = 0.017), the largest diameter of CBD stone(P = 0.008) and endoscopic papillary large balloondilatation (P = 0.038, Table 5). In multivariate analy-sis, only the initial CBD diameter was a significantlyrelated factor to the long-term dilatation of the CBD(odds ratio [OR] 1.754, 95% confidence interval [CI]1.107–2.778, P = 0.017).

DISCUSSION

The present study demonstrated that the diameter ofCBD recovered rapidly after stone extraction, and themore dilated the CBD was before stone extraction thegreater its diameter decreased, but the normalizationof CBD was not common. And a large CBD diameterbefore stone extraction was associated with the long-term dilatation of the CBD.

The wall of CBD consists of the columnar epithelium,subepithelial connective tissue, fibromuscular layerand adventitia. The subepithelial layer containsnumerous tough connective tissue fibers that con-tribute to the solid consistency of the wall. Thisfibroelastic layer may contain scant smooth musclefibers.13 There has been disagreement over whetherthere are smooth muscle fibers in the extrahepaticduct. In one study,13 100 post-mortem examinationsrevealed that 88% of CBD had no smooth musclefibers, but another study including 101 patients whounderwent surgical resection demonstrated that 99%of them had smooth muscle fibers in the CBD.3 Theseresearchers found that smooth muscle fibers in thelower third of the extrahepatic bile duct had a ten-dency to form either continuous or interrupted layer,whereas the proximal portion generally had no oronly scattered muscle fibers.3 Therefore, the scarcity ofsmooth muscle might contribute to the dilatation of

Table 4. Serial changes of common bile duct (CBD) diameters in patients followed up twice

Patient no.Duration from stone removal

to follow-up (months) CBD diameter (mm)*

1st follow-up 2nd follow-up Initial 1st follow-up 2nd follow-up

1 0.5 1.8 6.0 4.0 4.02 0.2 17.9 7.5 5.5 5.53 0.1 5.1 8.0 7.0 7.04 0.1 6.2 10.0 7.5 7.55 0.2 3.7 10.5 5.5 5.56 1.1 11.6 12.0 10.0 8.07 0.9 17.5 14.5 13.0 11.58 1.0 28.1 15.0 10.0 10.09 0.1 2.3 19.0 10.5 10.5

10 13.4 18.4 14.0 9.0 9.011 10.9 28.0 18.0 11.5 11.5

*Initial vs 1st follow-up, P = 0.003; 1st vs 2nd follow-up, P = 0.180.

Table 5. Analysis of the factors related to long-term dilatation of the common bile duct (CBD) (>10 mm more than 6months after stone extraction)

Factors

Univariate analysis Multivariate analysis

OR (95% CI) P value OR (95% CI) P value

Age 0.979 (0.911–1.051) 0.555Initial CBD diameter 1.754 (1.107–2.778) 0.017 1.754 (1.107–2.778) 0.017Previous cholecystectomy 0.265 (0.045–1.543) 0.139Periampullary diverticulum 2.889 (0.433-19.281) 0.273Number of CBD stones 0.814 (0.401–1.652) 0.568Largest diameter of CBD stone 1.364 (1.084–1.716) 0.008 0.803Endoscopic papillary large balloon dilatation 11.25 (1.146–110.5) 0.038 0.667

CI, confidence interval; OR, odds ratio.



the CBD. Another reason for CBD dilatation is that thescattered bundles of smooth muscle are arranged pre-dominantly in a longitudinal direction with respect tothe axis of the bile duct.14 Thus, the force of contrac-tion in the longitudinal direction is approximatelythrice that in the transverse direction.14 The elastic andsmooth muscle fibrils oppose the pressure caused byspace-occupying stones.4 When the pathologicalprocess is curtailed, the CBD returns to normal.

A dilated CBD is a challenging condition for clini-cians. When an inadequate decrease in the CBD dia-meter is found after the stone removal, residual stonesare suspected at first.4 However, the dilatation of CBDmay persist sometimes although there is no residualstone or stricture of the bile duct. In this study, weintended to identify the factors related to the sustaineddilatation of the CBD after stone extraction in patientswithout residual CBD stones, stricture of CBD orfurther surgical procedures. We identified the initialdiameter of CBD as an independently related factor tolong-term CBD dilatation. Therefore, a markedlydilated CBD before the extraction of stones might notbe normalized 6 months after the stone removal,although CBD with greater initial dilatation had agreater decrease in raw diameter than one that was lessdilated initially. Moreover, it is expected that CBDdilatation will continue or slightly decrease after 6months, based on the findings of our 11 patients whowere followed up twice. In addition, the relationshipbetween the diameter of the CBD and the recurrenceof stones had been reported in several studies,15–18 thatthe sustained dilatation of bile duct was a risk factorfor the recurrence of primary bile duct stones.

In previous reports the CBD diameter significantlydecreased 10 days after endoscopic sphincterotomyaccording to cholangiogram,19 and a considerabledecrease in the CBD diameter was detected within24 h after endoscopic sphincterotomy, which contin-ued gradually for the next 7 days.4 Because our studywas not a prospective serial follow-up trial, the timeand extent of recovery of CBD diameter after stoneextraction had to be inferred indirectly. We alsoshowed that the diameter of the CBD in patients fol-lowed up for more than 1 week did not demonstrate asignificant reduction compared with those followedup for less than 1 week. Moreover, a significantrecovery was achieved at the first follow-up and therewas little change in the CBD diameter after that atthe second follow-up. That is, the CBD diameterdecreased rapidly, especially within the first week afterthe extraction of the stones.

It is difficult to determine the upper limit of normaldiameter of the CBD. The dimensions of the CBD in150 adult corpses have shown a mean value of5.3 ± 1.3 mm.20 Conventionally, 6 mm is consideredto be the upper limit of normal value byultrasonography.1,2,21 However, the age of the patientand measurement location that is closer to the pancreasor liver may influence the CBD diameter. Some studieshave detected the bile duct diameter slightly increasedwith the patient’s age.22–24 One study showed that, innormal patients aged over 65 years the extrahepatic bileduct could measure up to 10 mm in diameter.24 Thediameter of the CBD which is located closer to thepancreas may be larger than that closer to the liver.Because ultrasound has a limited ability to evaluate theCBD that is located closer to the pancreas, we used CTand MRCP which can show the overall CBD structure.In one study that used a 64-slice CT the largest diameterof the CBD was up to 6 mm in most patients.2 An upperlimit of 8 mm appears reasonable in patients aged over50 years, and 10 mm seems appropriate for those whounderwent cholecystectomy.2 In the present study18.2% of patients had undergone cholecystectomybefore initiation of the study and the mean age ofour population was 71.4 years. Therefore, we chose10 mm as the upper limit of normal in our studypopulation. The diameter of CBD would have beenconsidered to be definitely abnormal if it had dilatedmore than 10 mm. Fluoroscopic images of ERCP werenot used in the present study because the diameterof the CBD could be exaggerated during ERCP. Thisdifference may be related to the effect of the contrastmedium injected into the bile duct under highpressure.25

There were some limitations to our study. First, thiswas a retrospective study. Prospective studies with aserial follow-up after stone extraction would be moreuseful to determine the time and extent of recovery ofthe CBD. However, CT or MRCP cannot be seriallyperformed within a short period due to radiationhazard or high cost, although it has several advantagesover ultrasonography. Comparison among variousfollow-up duration in our patients was possible as theduration varied in our study. Second, the sample sizeand the patients who were followed up twice were notlarge. Third, it is possible that small radiolucentresidual or recurrent stones were not detected inpatients with CT follow-up. To reduce this possibility,ENBD tube was inserted and tubogram was performedvia the ENBD tube in all patients who underwent theendoscopic extraction of CBD stones. In addition, wechecked the symptoms of patients and performed bio-



chemical tests together with imaging follow-up. Incase of any suspicion of CBD stones, we performedMRCP or ERCP.

In conclusion, CBD diameter recovers rapidly after theextraction of CBD stones. The greater the CBD isdilated before stone extraction, the less frequently it isnormalized, and the large diameter of CBD beforestone extraction is associated with the long-term dila-tation of the CBD. Prospective large-scale studies onthe changes in the CBD diameter are needed in thenear future.

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