Abdominal ultrasonography following laparoscopic cholecystectomy: A prospective study

Clinical Radiology (1993) 47, I 11-113

Abdominal Ultrasonography Following Laparoscopic Cholecystectomy: A Prospective Study T. A. F A R R E L L , J. G. G E R A G H T Y * and F. K E E L I N G

Departments of Radiology and *Surgery, Beaumont Hospital, Dublin, Ireland Laparoscopic cholecystectomy has gained widespread acceptance as the operation of choice for symptomatic gall-stones. We prospectively performed ultrasonography on 100 consecutive patients after laparoscopic cholecystectomy to determine the effect of this procedure on common bile duct diameter. This study also examines the incidence and clinical significance of intra-abdominal fluid collections after laparoscopic cholecystectomy. Our results show that 24% of patients had dilatation of the common duct (greater than 6 mm) when scanned 48 h post-operatively. The incidence of dilated common ducts fell to 9% when the patients were scanned 1 month later. This transient dilatation of the common duct, occurring post-operatively, has not been previously described. Intra-abdominai fluid collections were demonstrated in 10% of our patients but were clinically significant in only 1%. This study suggests that routine ultrasonography has a low yield immediately after laparoscopic cholecystectomy. Farrell, T.A., Geraghty, J.G. & Keeling, F. (1993). Clinical Radiology 47, 111-113. Abdominal Ultrasonography Following Laparoscopic Cholecystectomy: A Prospective Study

Accepted for Publication 29 August 1992

Since it was first performed in 1987, laparoscopic cholecystectomy has gained widespread acceptance in the management of symptomatic gall-stones. Because o f the reduced hospital stay and early return to work, laparoscopic cholecystectomy has replaced open cholecystectomy as the treatment of choice in many centres [1,2]. It has been reported that common duct dilatation as detected by ultrasonography does not occur in the majority of patients in response to open cholecystectomy [3,4]. The influence o f laparoscopic cholecystectomy on common bile duct size is unknown. Furthermore, fluid collections in the sub-hepatic and sub-phrenic space are well recognized complications of open cholecystectomy but there is little information on the incidence o f this complication in patients undergoing laparoscopic cholecystectomy [5-7]. This study prospectively evaluates the natural history of common bile duct diameter in 100 consecutive patients post-laparoscopic cholecystectomy. This study also evaluates the role of routine scanning for sub-phrenic and sub-hepatic fluid collections in patients after laparoscopic cholecystectomy. PATIENTS A N D M E T H O D S All 100 patients undergoing laparoscopic cholecystectomy between 1 July 1991 and 1 November 1991 were entered into the study. There were 84 women and 16 men with ages ranging from 19 to 70 years (mean 46 years). Nineteen patients were lost to follow-up at 1 month. Routine laparoscopic cholecystectomy was performed as previously described [8]. Abdominal drains were not used and patients were excluded from the study if their cholecystectomy was converted to an open technique. Written informed consent was received from all patients. Correspondence to: T. A. Farrell, Department of Radiology, Beaumont Hospital, Dublin 9, Ireland.

In addition the patient's temperature, white cell count and liver function tests were obtained pre-operatively and again 48 h post-operatively. A standard Siemens 3.5 MHz ultrasound transducer was used and all patients were scanned by one of us (TF) in the supine and left lateral decubitus positions while fasting between 0700 and 0800 h. The common duct diameter was evaluated by measuring the mucosa to mucosa diameter at the level of the fight hepatic artery and we took 6 mm as the upper limit of normal. In addition, the sub-phrenic and sub-hepatic spaces were scanned specifically to look for a fluid collection. Each patient was scanned pre-operatively and again 48 h postoperatively. Patients were followed up at 1 month, at which time ultrasonography was repeated. The results are presented as mean _+standard error of the mean (SEM) and comparison of the two means was performed using a Student's t-test. Common Duct Diameter The distribution of the common duct diameter measurements is shown in Fig. 1. O f the 100 patients, only three (3%) had a dilated duct pre-operatively. However, when scanned 48 h post-operatively, 24% of patients had a duct diameter greater than 6 mm (Fig. 2). When scanned again at 1 month, this incidence had reduced to 9%. Table 1 shows the mean and range of duct diameters. There was a statistically significant increase in the mean common duct diameter at 48 h (P < 0.05) when compared with the pre-operative value. There was no correlation between serum bilirubin and alkaline phosphatase, and duct diameter in those with dilated ducts at 48 h. None of the three patients with dilated ducts pre-operatively had biochemical evidence of biliary obstruction.

112

CLINICALRADIOLOGY DISCUSSION

Fluid Collections

Ten patients (10%) had intra-abdominal fluid collections demonstrable on ultrasound (Fig. 3). Only one of these was regarded as clinically significant in that the patient developed right upper quadrant pain, leucocytosis and pyrexia. Ultrasound at 24 h demonstrated a well defined fluid collection in the sub-hepatic space. The patient responded to intravenous antibiotics and fluids, and did not require a drainage procedure. One patient had a small right basal pleural effusion demonstrated at 48 h which was asymptomatic.

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Fig. 1 - The distribution of common duct diameters in patients scanned pre-operatively, 48 h post-operatively and 1 month post-operatively. The short horizontal lines represent the mean common duct diameter on each occasion. The upper limit of normal was taken as 6 mm.

This study shows that almost one quarter of our patients had dilated c o m m o n ducts when scanned 48 h post-laparoscopic cholecystectomy. This increase in comm o n duct size was transient as the diameter had returned to normal values at 1 month. This change in c o m m o n duct size in the early post-operative period h a s not been described previously. G r a h a m et al. [3] have shown that 16% of patients have c o m m o n ducts larger than 4 m m when scanned after open cholecystectomy, and in these patients the duct m a y measure up to 10 mm. However, the interval between surgery and the repeat scanning, in their study, varied from 4-16 months with a mean of 11.1 months. Mueller [4] demonstrated that 5% of patients had a c o m m o n duct diameter greater than 6 m m when scanned 6 months postcholecystectomy. However, neither of these studies measured the c o m m o n duct diameter in the immediate postoperative period. The results of the present study are in agreement with Mueller and Graham, demonstrating that c o m m o n duct diameter is increased in less than 10% of patients at 1 month. Our results differ from other reports in that they show a transient rise in c o m m o n duct diameter shortly after laparoscopic cholecystectomy. M a h o u r [9] used cholangiography to describe an increase in c o m m o n duct size in a canine model postcholecystectomy. Dilatation of the c o m m o n duct was present by the third day and maximal during the third and fourth weeks. Thereafter the duct diameter regressed, remaining about twice that recorded at the time o f cholecystectomy. These results differ from those in the present study and this difference may be due to the use of direct cholangiography rather than the non-invasive technique of ultrasonography to image the c o m m o n bile

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Fig. 2 - Ultrasound scan of the right upper quadrant in the parasagittal plane taken 48 h post-operatively. The common duct measured 8,9 m m in diameter.

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Fig, 3 - Oblique scan through the right upper quadrant showing a welldefined fluid collection in the sub-hepatic space.

Table 1 - T h e m e a n and range o f c o m m o n duct ( C D ) diameters

Mean (mm) Range (mm) No, o f patients whose C D exceed 6 mm *P<0.05.

Pre-op (n = 100)

48 h post-op (n = 100)

I month post-op (n =81)

4.1 2.8-7 3

5.3* 3-11 24

4.3 3-9.5 9

ABDOMINALUS FOLLO'WINGLAPAROSCOPICCHOLECYSTECTOMY duct. Alternatively differences in species m a y a c c o u n t for these varying results. The results o f the present study have i m p o r t a n t implications in the interpretation o f ultrasonographic findings in the early period after laparoscopic cholecystectomy. Given that pre-operative c h o l a n g i o g r a p h y at laparoscopic cholecystectomy is not routine in m a n y centres, it is not k n o w n whether stones m a y be present in the c o m m o n bile duct. This study shows that ultrasound assessment o f the biliary tree in the early post-operative period is unreliable, and suggests that repeat ultrasound examinations at later intervals are a more accurate determinant o f c o m m o n duct pathology. The cause o f c o m m o n duct dilatation in the early post-operative period is not clear but is p r o b a b l y due to a localized ileus. Sub-hepatic fluid collection is a well k n o w n complication o f open cholecystectomy o c c u r r i n g in significant a m o u n t s in up to 18% o f patients [6]. Ten o f our patients (10%) had demonstrable fluid collections post-operatively. Only one patient had a clinically significant collection. This patient was pyrexial and had a raised white cell count. These results suggest that routine postoperative screening for sub-hepatic collections is unnecessary and should be limited to patients with other supportive clinical features. In conclusion this study demonstrates a transient dilatation in c o m m o n duct diameter in 24% o f patients shortly after laparoscopic cholecystectomy. It also demonstrates a low yield if u l t r a s o n o g r a p h y is used to screen for sub-hepatic collections at this time. These results suggest that ultrasound examination o f the abdo-

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men is an unnecessary screening procedure in the early period after laparoscopic cholecystectomy. Acknowledgements. We are indebted to our surgical colleagues for allowing us to examine their patients. REFERENCES

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