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Role of pre-operative ultrasonography in assessment of technical difficulties during laparoscopic cholecystectomy requiring conversion to open procedure

Laparoscopic cholecystectomy is the treatment of choice for symptomatic gallstones. It offers a cure for gallstones with a minimally invasive procedure, less pain and scarring, and early return to full activity. When important anatomic structures cannot be clearly identified or when no progress is made over a set period of time, a conversion to an open procedure is usually indicated in order to avoid injury to structures like common bile duct or duodenum. Conversion rates are typically less than 10% for both elective and emergency procedures.


INTRODUCTION
Laparoscopic cholecystectomy is the treatment of choice for symptomatic gallstones. It offers a cure for gallstones with a minimally invasive procedure, less pain and scarring, and early return to full activity. When important anatomic structures cannot be clearly identified or when no progress is made over a set period of time, a conversion to an open procedure is usually indicated in order to avoid injury to structures like common bile duct or duodenum. Conversion rates are typically less than 10% for both elective and emergency procedures. 1,2 An ultrasound is the initial investigation of any patient suspected of disease of the biliary tree. It is non-invasive, painless, does not expose the patient to radiation, and can be performed on critically ill patients. It is dependent upon the skills and the experience of the operator. Adjacent organs can frequently be examined at the same time. Ultrasound will show stones in the gallbladder with sensitivity and specificity of more than 90%. Stones are acoustically dense and reflect the ultrasound waves back to the ultrasonic transducer.
The study aim was to evaluate the accuracy of certain ultrasound parameters to predict a difficult laparoscopic cholecystectomy.

Study site
St. Stephen's Hospital, New Delhi

Study population
Patients of all ages and both sexes, irrespective of comorbidities or duration of disease, with symptomatic gall stones, who get admitted under department of surgery in St Stephen's Hospital, with ultrasonography of whole abdomen done within 1 week prior to the planned laparoscopic cholecystectomy.

Exclusion criteria
Exclusion criteria were 1) patients with common bile duct stones, requiring common bile duct exploration 2) patients with jaundice or abnormal liver function tests 3) patients with pregnancy 4) patients with portal hypertension, cholangitis, known carcinoma gall bladder, acute pancreatitis, known biliary-enteric fistula, known Mirizzi syndrome (types II-V) 5) patients with previous upper abdominal surgery 6) patients with any contraindication to laparoscopic surgery 7) conversion to open procedure due to equipment malfunction.

Study design
Prospective observational study.

Sample size
120 patients were included in the study.

Preoperative ultrasonography
This was done after overnight fasting within one week prior to the planned date for surgery in the department of radio-diagnosis of St Stephen's Hospital, New Delhi.
The following criteria were assessed: 1) gall bladder wall thickness-more than 4 mm was considered to be a predictor of a difficult laparoscopic cholecystectomy 2) gall stone mobility-impacted gall stones in gall bladder neck were considered to be a predictor of difficult laparoscopic cholecystectomy 3) gall bladder morphology-contracted gall bladder was considered to be a predictor of a difficult laparoscopic cholecystectomy 4) diameter of common bile duct-more than 6mm was considered to be a predictor of difficult laparoscopic cholecystectomy.

Intraoperative assessment
During the laparoscopic cholecystectomy presence of any of the following observations were considered as difficult cholecystectomy: 1) total duration of surgery from creation of pneumoperitoneum to extraction of gall bladder being more than 90 minutes 2) tear of gall bladder during dissection, with spillage of bile and stones, due to difficult and unclear anatomy, and dense pericholecystic adhesions 3) conversion to open procedure because of: difficult dissection (adhesions at Calot's triangle), unclear anatomy (short/dilated cystic duct, unusual positions of cystic artery), to avoid risk of injury to biliary tract or any surrounding viscera, or uncontrollable bleeding.

Statistical methods
Descriptive statistics were analyzed with SPSS version 17.0 software. Categorical variables were expressed as frequencies and percentages. The Pearson's chi-square test was used to determine the relationship between two categorical variables.
Sensitivity, specificity and p values were calculated for various ultrasound parameters as predictors for difficult laparoscopic cholecystectomy. P value<0.05 was considered statistically significant.

RESULTS
Out of the 120 patients, 91 were females and 29 were males. Maximum incidence of gall stone disease was seen in the age group of 31-40 years in both sexes. Highest number of difficult laparoscopic cholecystectomies were encountered in the age group of 51-60 years ( Figure 1). Total 8 patients had gall bladder wall thickness>4mm of which 6 patients (75%) had a difficult laparoscopic surgery (Table 1).  Out of 8 patients with gall bladder wall thickness>4mm, 2 patients (25%) had to be converted to open (Table 2).    (Table 4).
Total 9 patients were found to have contracted gall bladder of which 8 patients (88.8%) had a difficult surgery (Table 5).    (Table 8).
Total 120 patients were operated upon, of whom 36 (30%) of them took more than 90 minutes from creation of pneumoperitoneum to extraction of gall bladder specimen (due to dense pericholecystic adhesions, unclear anatomy or conversion to open procedure) and have been considered as difficult (Table 9).    Among these 12 patients, 2 of them had a gall bladder wall thickness>4mm, while rest 10 had wall thickness<4mm.
Total 2 patients of these 12 patients had impacted calculi at gall bladder neck, while the remaining 10 did not. Of these 12 patients, 4 patients had contracted gall bladder and the other 8 had a distended gall bladder. Common bile duct diameter was>6mm in 2 patients, and<6mm in the other 10 patients. Several studies have been done previously to correlate preoperative ultrasound findings to predict a difficult laparoscopic cholecystectomy.
A study by Sharma et al had taken into consideration sonographic parameters like size of gall bladder, wall thickness, distance between hepaticoduodenal ligament and Hartmann's pouch and the size of stone were and difficulties in terms of adhesions around gall bladder, anatomy of Calot's triangle and difficulty in peeling off gall bladder from the bed and retrieval were analyzed.
It was concluded that preoperative sonographic signs can predict the difficulty in laparoscopic cholecystectomy. 3 In a study by Lal et al a preoperative ultrasound was performed just prior to surgery, and 4 ultrasonographic parameters were analyzed, namely gallbladder wall thickness, contracted gallbladder, impaction of gallstones at the neck of the gallbladder, and common bile duct stones. It was concluded that preoperative ultrasonography is a good predictor of difficulty in laparoscopic cholecystectomy in the majority of cases and should be used as a screening procedure. 4 A study by Vivek et al showed that a distended gall bladder or a gall bladder filled with stones, presence of inflammation around the gall bladder leads to problems of grasping, thus making the laparoscopic procedure difficult. Calot's triangle difficulty was associated with the sonographic parameters like contracted gall bladder, presence of peri-pancreatic fluid, presence of multiple stones, presence of cirrhosis on ultrasound, non visualisation of the gall bladder, inflamed gall bladder and presence of ductal anomalies. 5 Ercan et al concluded in a study that significant predictors of conversion to open cholecystectomy included preoperative ultrasound findings of a thickened gallbladder wall and dilated common bile duct. 6 Gabriel et al found that ultrasonography findings of multiple calculi and gall bladder wall thickness of more than 3 mm, and intraoperative gall bladder perforation with spillage of its contents in abdominal cavity and dense adhesions with difficult anatomy resulted in higher conversion rate. 7 A study by Nidoni et al revealed that sonographic findings of gall bladder wall thickness of>3mm and pericholecystic collection were statistically significant for predicting the difficult laparoscopic cholecystectomy and its conversion. 8 Study of Dhanke et al showed that gallbladder wall thickening, impacted stone, and pericholecystic collection are significant predictors of difficult laparoscopic cholecystectomy. 9 Chand et al found that gallbladder wall thickness more than 4 mm, stone impacted at the neck of gallbladder, contracted gallbladder and common bile duct size more than 6 mm in preoperative ultrasonography was a predictor of difficult laparoscopic cholecystectomy that requires conversion to open procedure. 10

CONCLUSION
It was found that ultrasonography can be a useful tool in predicting a difficult laparoscopic cholecystectomy. Significant association was found between all the independent ultrasound parameters and a difficult laparoscopic cholecystectomy. Apart from presence of contracted gall bladder, no significant association was found between the other ultrasound parameters and conversion to open cholecystectomy. Therefore, at the end of this study, it can be recommended that preoperative ultrasound should be used as a tool to predict a difficult laparoscopic cholecystectomy. It will help in preoperative counseling of patients and also explaining about chances of conversion to open procedure. It will help the surgeon to be mentally prepared when a difficult surgery is anticipated. But it should also be kept in mind that preoperative ultrasound is not the ideal modality to predict chances of conversion to open cholecystectomy and all difficult laparoscopic cholecystectomies do not need to be converted to open cholecystectomy.