Beware the contracted gallbladder – Ultrasonic predictors of conversion

Abstract

Introduction

Pre-operative ultrasound is the gold standard pre-operative investigation for patients undergoing a cholecystectomy. Ultrasound provides a sensitive approach for analysing characteristics of the gallbladder. Thus, we aimed to examine the importance of ultrasonic gallbladder characteristics on laparoscopic cholecystectomy conversion rates and then sought to devise a pre-operative predictive score for conversion based on our findings.

Methods

A retrospective analysis of patients undergoing a laparoscopic cholecystectomy was performed between January 2000 and December 2006. Patient demographic data and pre-operative imaging results from abdominal ultrasounds were analysed. We then devised a pre-operative predictive score for conversion based on independent variables derived from multivariate analysis.

Results

A total of 1061 patients underwent a laparoscopic cholecystectomy. Conversion to an open procedure was required in 58 cases. The overall conversion rate was 5.4%. Univariate analysis revealed male gender (p < 0.0001), gallbladder wall thickness >4 mm (p = 0.0024), a contracted gallbladder (p = 0.005) and a dilated CBD (p = 0.0416) as being significantly associated with conversion. These variables were then evaluated using multivariate analysis and three variables, namely, male gender, a contracted gallbladder and a thickened gallbladder wall were identified as independent predictors. A pre-operative predictive score for conversion was devised from a training cohort (n = 761) and tested on a sub-cohort (n = 300). Patients with a score of 2 or more had a 19.2% risk of conversion (p < 0.001).

Conclusion

Conversion to an open cholecystectomy shows a strong associated with gallbladder ultrasonic characteristics which are available pre-operatively. The likelihood of conversion can be accurately predicted using a pre-operative scoring system.

Introduction

The last 25 years has seen a dramatic change in the management of gallbladder disease, acute cholecystitis in particular. Since the advent of laparoscopic surgery, laparoscopic cholecystectomy has emerged as the gold standard treatment for symptomatic cholelithiasis.¹ Laparoscopy has the advantage of being minimally invasive and is associated with less morbidity, shorter hospital stay, decreased postoperative pain, decreased postoperative ileus incidence, earlier oral intake, earlier return to normal activity, and improved cosmetic results.

Laparoscopic cholecystectomy has evolved over time and in recent years adaptations have emerged in the form of single port cholecystectomy and NOTES surgery.2, 3 Despite these adaptations, occasionally conversion to an open operation is necessary. Conversion increases the patient's risk of morbidity including wound infections and lower respiratory tract infections and results in an increase in length of hospital stay.⁴ A clear understanding of pre-operative predictors for conversion enables the operating team and patient to plan for the procedure appropriately.

Abdominal ultrasound is the gold standard pre-operative investigation for assessment of gallbladder disease.⁵ Ultrasound provides useful information on the characteristics of the gallbladder and its contents pre-operatively and represents a sensitive diagnostic tool for evidence of chronic inflammation in the gallbladder bed and its surrounds. Chronic inflammation in this area gives rise to effects such as gallbladder contraction and thickening of the gallbladder wall. The presence of these features is associated with increased adhesion formation, severe pericholecystic fibrosis and distorted anatomy in Calot's triangle. This can contribute greatly to the difficulties faced by a surgeon performing a laparoscopic cholecystectomy and lead to an increased risk of conversion.

Thus, the aims of this study were to examine the relationship between pre-operative ultrasonic characteristics and conversion rates for laparoscopic cholecystectomy. Following this, we sought to devise a pre-operative predictive score for conversion based on ultrasonic variables available pre-operatively.