Interventional radiology of the gallbladder

Interventional radiology of the gallbladder

9 Interventional radiology of the gallbladder W. R. LEES Interventional radiology and surgery of the gallbladder have gone through dramatic changes i...

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9 Interventional radiology of the gallbladder W. R. LEES

Interventional radiology and surgery of the gallbladder have gone through dramatic changes in recent years, and although the overwhelming success of laparoscopic techniques now means that the radiologist no longer offers alternatives to elective surgery, many of the techniques learned during this period of intense competition remain vitally important to the management of complicated gallbladder disease (Reddick and Olsen, 1989). FINE-NEEDLE

ASPIRATION

Puncture of the gallbladder with fine-needle aspiration used to be considered a high-risk procedure, but in the absence of biliary obstruction the accumulated evidence would suggest that biliary peritonitis is a rare event. Fine-needle aspiration of gallbladder contents is primarily performed for suspected sepsis (Figure 1). However, primary carcinoma of the gallbladder

Figure 1. Sagittal section showing empyema of the gallbladder. The presence of internal echoes does not necessarily mean the presence of pus: this pattern can also be seen in hepatitis and in patients with total parenteral nutrition. Fine-needle aspiration must be performed to establish the diagnosis. BaiNi&e’s

Clinical

Gastroenterology-

Vol. 6,No. 2, June 1992 ISBN O-7020-162F3

383 Copyright 0 1992, by Baillitre Tindall All rights of reproduction in any form reserved

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frequently presents as acute cholecystitis or empyema and cytological examination may be the only way to determine the diagnosis with certainty (Figure 2). Standard culture techniques have a sensitivity of less than 60% in determining the presence of biliary infection (McGahan and Linfors, 1988)) and the appearance and odour of the bile sample should be considered more important in determining whether to proceed to drainage immediately. Whenever possible, the gallbladder should be punctured under ultrasonographic control with a lateral transhepatic approach via the bare area of the

Figure 2. (a) A CT scan of carcinoma of the gallbladder. (b) Carcinoma of the gallbladder presenting with sepsis and perforation. A fine-needle contrast study outlines an abscesscavity with communication to the duodenum, and the diagnosis can only be made by cytological analysis.

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gallbladder. Computed tomography (CT) studies have shown that the relationship of the liver to the gallbladder is not constant and that the transhepatic approach may miss the bare area in up to 40% of patients (Warren et al, 1988; Hruby et al, 1989a). The gallbladder depending from the liver surface by a mesentery is rare, occurring in l-2%; it is easily recognized by the gallbladder rolling away from the liver edge upon puncturing. With a distended gallbladder, the transhepatic approach might not be feasible and a fundal puncture should be performed. CI-IOLECYSTOGRAPHY Direct injection of contrast medium into the gallbladder to outline the lumen will readily demonstrate the cystic duct. Contrast at almost all dilutions will layer within the gallbladder and small stones can easily be missed unless bile is aspirated completely. If the cystic duct appears occluded or if the bile is infected, then contrast infusion should be on a replacement basis or the bile should be aspirated from the gallbladder completely to avoid bacteraemia (Figure 3).

Figure 3. Fine-needle antegrade cholecystography. The gallbladder has been outlined following puncture by the transhepatic route. Several small stones are seen partially occluding the cystic duct.

With careful positioning, contrast infused down the cystic duct can display the entire biliary tree, and antegrade cholecystography is a safe alternative to percutaneous transhepatic cholangiography (PTC) in patients who have a normal calibre biliary tract or in sclerosing cholangitis. PERCUTANEOUS

CHOLECYSTOSTOMY

The present indications for percutaneous

cholecystostomy

are:

386 1. 2. 3. 4.

W. R. LEES

Direct cholangiography. Biliary drainage. To develop an access track for stone removal. Decompression and drainage in acute cholecystitis and empyema.

In most circumstances the lateral transhepatic approach to the gallbladder is used with ultrasound guidance. The gallbladder can be punctured with a fine-needle introducer set or directly with a sheathed needle, the aim being to leave in a self-retaining catheter of the Cope loop type (Figure 4). In an

Figure 4. (a) Empyema of the gallbladder drained via the transperitoneal fundal approach. The cystic duct has been occluded by tumour overgrowth from a stented carcinoma of the pancreas. A self-retaining Cope loop catheter was inserted for long-term drainage. (b) The gallbladder has been evacuated and the catheter pulled back to the anterior abdominal wall to provide tamponade.

emergency with an empyema and profound sepsis, a single-stick puncturing technique is to be preferred, using the most direct and simplest route into the gallbladder, aiming to decompress it and evacuate its contents (Figure 5). Recovery in such circumstances can be dramatic, and a catheter exchange may be performed at 24-48 hours to allow drainage for 2-3 weeks prior to definitive treatment. A simple drain is likely to fall out when the patient is mobilized (Cope et al, 1990; Lee et al, 1991; Zagar et al, 1991). Technique The initial approach is as for simple fine-needle aspiration of the gallbladder, using a fine-needle introducer or by direct puncture with a sheathed needle. If the gallbladder is firmly attached to the liver then the transhepatic route is to be preferred and a standard J guide wire will suffice, with

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Figure 5. Mirrizi syndrome. A large calculus in Hartmann’s pouch was occluding both the common bile duct and the gallbladder outflow. The patient was septic and jaundiced. The jaundice was relieved with endoscopic stenting and the empyema by insertion of a simple drain via a single-stick approach. After successful resolution of both jaundice and sepsis, the tract was dilated and the stones extracted using nephroscopic techniques.

Figure 6. Disaster! Access to the gallbladder has been lost and the gallbladder has been decompressed; copious quantities of bile are seen in the right upper quadrant. Provided that a drain can be reinserted into the gallbladder and the free fluid has been evacuated, conservative management will almost certainly be adequate.

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subsequent dilation with Teflon dilators to 8-9 FG to allow the introduction of a self-retaining catheter which can be then pulled back to the puncture site to provide a degree of tamponade. If the gallbladder proves to be poorly attached and mobile, a superstiff or a Lunderquist exchange wire with a short, floppy tip should be used, as any significant deflection of the track can make dilation impossible. Care should be taken to ensure that the floppy tip of the guide wire is contained completely within the gallbladder. In view of the small volume of the gallbladder, this can be difficult and a Lunderquist exchange wire with a lo-mm floppy tip is essential. Such wires, however, are dangerous and great care should be taken to avoid perforation of the gallbladder wall (Figure 6). With transperitoneal fundal puncture, the line of the puncture track should run from the fundus to the gallbladder neck. Invagination of the gallbladder wall will undoubtedly occur to some degree and there should be enough working space within the gallbladder to allow for this. For dilation up to l&12 FG, an anchoring device is not required when dilating over a stiff guide wire.

7. Acute acalculous cholecystitis (intensive therapy case). A simple 5-FG pigtail catheter was inserted into the gallbladder at the bedside. Contrast study revealed oedematous and necrotic gallbladder mucosa and obstruction of the gallbladder outlet. Although the gallbladder contents were not frankly purulent, the patient’s sepsis resolved within 24 hours of drainage.

Figure

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The gallbladder contents should be evacuated completely at the time of the procedure. Catheters as small as 5-6 FG are adequate to decompress the gallbladder and to drain pus or bile. In presence of profound sepsis the use of a single-stick catheter minimizes the amount of manipulation that is needed and drainage can be performed at the bedside or in the intensive therapy unit. The author prefers to use simple Teflon pigtail catheters which are easier to insert (Figure 7). These should be exchanged for self-retaining polyethylene or polyurethane catheters before the patient is mobilized (Thornton et al, 1983). Antibiotics All manipulative procedures of the infected gallbladder can produce bacteraemia, and cover with a broad-spectrum intravenous antibiotic is mandatory. Long-term

drainage

The majority of acute gallbladder infections are secondary to calculous obstruction of the cystic duct. However, the author’s own practice contains many cases of malignant obstruction where the gallbladder has become infected following interventional radiologic or endoscopic procedures. Ainley et al (1991) reported that the gallbladder could be the source of sepsis in up to 3% of patients undergoing endoscopic stenting for malignant obstructive jaundice. If the cystic duct is occluded by tumour then there are three choices: 1. Simple aspiration and antibiotics. 2. Permanent gallbladder drainage for the remainder of the patient’s life. 3. Percutaneous drainage for 4-5 weeks with establishment of a mucous fistula. Options 1 and 3 run the risk of recrudescence of the empyema. Option 2 may be too uncomfortable for the patient to tolerate in the long term (Figure 8). Complications The early literature on percutaneous cholecystostomy contains several cases of life-threatening vagal reaction with one reported fatality (vansonnenberg et al, 1984). Vagal reactions are frequent with all biliary procedures and are particularly common with manipulation of the gallbladder neck and cystic duct. If promptly recognized, these reactions are easily reversed with intravenous atropine. A leakage of infected bile is potentially disastrous and can only be dealt with by establishing gallbladder drainage. Small amounts of biliary leakage are common during gallbladder procedures and can almost always be managed conservatively. Recovery is helped by a small drain placed adjacent to the gallbladder using ultrasound guidance (Figure 9). Bacteraemia should be minimized by using only small quantities of dilute

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contrast and endeavouring not to pressurize the gallbladder lumen. Exploration of cystic duct patency should be deferred until the acute infection has resolved. Pain following percutaneous cholecystostomy is common and is often inexplicable. Despite all these potential problems, percutaneous cholecystostomy is a safe and simple technique which can have an almost magical effect in

(4

(b)

Figure 8. Ideal catheter placement for long-term drainage shown on CT scans (a, b). A subcostal transhepatic approach has been employed, and the loop of the catheter fixes the gallbladder fundus to the posterior aspect of the anterior abdominal wall.

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relieving postoperative gallbladder sepsis. Its use does not preclude subsequent laparoscopic or conventional gallbladder surgery. It has even been proposed as a provocation test in cases where the source of sepsis is unknown, particularly in patients in intensive therapy units or postoperative patients, in whom acalculous cholecystolithiasis is undoubtedly much more common than had previously been realized (Van der Linden and Sunzel, 1970; Glen, 1981; Lindemann et al, 1988). Anaesthesia and analgesia Although the vast majority of simple cholecystostomies can be performed under local anaesthesia with intravenous sedation (pethidine and diazepam emulsion), in some patients the gallbladder is extraordinarily sensitive to stretch and severe, uncontrollable pain can occur. This is an unpredictable event, but seems far less likely to occur during emergency treatment than with elective procedures. Intercostal and coeliac plexus nerve blocks performed under ultrasonographic control with local anaesthesia diminish the sensation of pain but rarely allow complete control (Vogelzang and Nemcek, 1988). Most of the patients who are referred for elective gallbladder intervention are medically and surgically unfit, and it is essential for the radiologist to yield control of the patient to an anaesthetist. Most anaesthetists consider it safer to perform dangerous procedures under general anaesthesia rather than struggle with heavy intravenous sedation. Catheter and guide wire dislodgement are also less likely to occur in an anaesthetized patient. Postoperative pain can be due to bile leakage around the catheter or from an unsuspected perforation, but often ultrasound scanning will show only a very small quantity of free fluid around the gallbladder. Pain can also be secondary to irritation of the intercostal nerve by a catheter, and if long-term drainage is contemplated the subcostal route is more comfortable. Catheter removal Self-retaining catheters can often be difficult to remove; they are best extracted over a guide wire with fluoroscopic assistance. STONE EXTRACTION

TECHNIQUES

Although it is possible to extract small stones through a 12 or 14 FG sheath under local anaesthesia using baskets or flexible mini-endoscopes (Hruby et al, 1989b), the vast majority of patients with gallstone disease will require lithotripsy (Figures 9, 10). Direct contact electrohydraulic laser lithotripsy will fragment stones, but patients with a significant stone burden will almost certainly require multiple sessions. The rotary lithotrite developed by Baxter is a derivative of the Kensey catheter (Wholey and Smoot, 1988). A small, rotating impeller is delivered into the gallbladder via a 12-FG metal sheath and is deployed within a protective cage of expanding metal prongs.

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Fitiv 9. Transhepatic drainage. Some leakage of contrast can be seen from the puncture ‘site to the liver edge and Morrison’s pouch.

Figure 10. A steerable catheter is used to gain transcystic duct access to the common bile duct, to disimpact and fragment the obstructing calculus after failed endoscopic sphincterotomy.

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As the impeller rotates at speeds up to 30000 rev/min, mobile stones within the gallbladder lumen are drawn in and emulsified. Stones of any composition and less than 3 cm in diameter can be dealt with by this device. The average rotation time is 14 minutes, but harder stones and larger stone burdens may take up to an hour. This is the most effective contact lithotripsy device available for use within the gallbladder, but its use is limited at present to patients unfit for general anaesthesia. In the author’s experience of 25 cases there were only 2 cases where the device failed to emulsify mobile stones, but in 5 cases cholecystoscopy was employed to dislodge stones impacted in the cystic duct or in fundal loculi (Figure 11). Our experience with small track procedures has shown to us that ultrasound, cholangiography and direct vision are all needed to ensure that complete gallbladder clearance is achieved. Small stones can be missed by any of these techniques used in isolation. Patients with impacted stones or large stones are better dealt with by rigid nephroscopic techniques than by flexible endoscopy (Kellett et al, 1988). In the author’s practice we have performed over 150 percutaneous cholecystolithotomy procedures, working predominantly through 28 or 30 FG sheaths

Figure 11. Flexible cholecystoscopy. Fully functional endoscopes are now manufactured with calibres as small as 9 FG; they are capable of taking guide wires and baskets for stone disimpaction and can easily accommodate the smallest electrohydraulic lithotriptor of 3 FG. Here a lo-mm stone in the neck of the cystic duct has been fragmented by contact lithotripsy.

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of Amplatz type. Although the procedure can be performed in two stages under local anaesthesia, over 90% of these cases were performed under elective general anaesthesia. Puncture was usually transperitoneal, with 80% employing the subcostal rather than the intercostal route. Initial puncture under ultrasound control was followed by insertion of a Lunderquist 0.038 exchange wire with dilation to 8 FG using Teflon dilators; then

Figure 12. Percutaneous cholecystolithatomy. (a) A 30-FG Amplatz sheath has been inserted into the gallbladder via a transperitoneal fundal approach. The sheath has been retracted to allow working space within the gallbladder lumen and the gallbladder distended by the use of a Foley catheter occluding the sheath lumen. A safety guide wire is generously looped within the gallbladder. (b) Ideal placement of instruments within the gallbladder is often best achieved using ultrasound rather than fluoroscopic guidance, as the gallbladder wall and stones can be directly observed. This example shows the Amplatz sheath within the lumen of the gallbladder together with the safety guide wire.

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GALLBLADDER

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coaxial telescoping metal dilators were used for rapid dilation to 30 FG and subsequent insertion of an Amplatz sheath (Figure 12). Nephroscopy with saline flush was used to clear the gallbladder of small stones and fragments, with contrast electrolithotripsy required in 55% of cases. The excellent field of view obtained through rigid optics ensured

Figure

13. Position of Amplatz sheath within the gallbladder following successful clearance.

Figure 14. A Foley catheter providing gallbladder drainage. The balloon has been inflated to fill the fundus and provide tamponade.

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gallbladder clearance in all but 4 patients (Figures 13-16). Most patients can be discharged after PCCL within 48 hours, returning on the 10th day for a careful contrast study and for the removal of the Foley catheter if clearance is achieved. PCCL was developed to the level of a routine procedure with a mean operating time of 40 minutes in the latter part of the series (Tables 1 and 2). It can certainly be considered a viable alternative to open cholecystectomy has been almost totally replaced by laparoscopic techniques. It can be still considered useful in three contexts:

Figure 15. Ultrasound scan of a correctly positioned Foley catheter within the gallbladder lumen.

Figure 16. Foley catheter. The subcostal approach is the most comfortable.

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Table 1. Summary of percutaneous cholecvstolithotomy Results of procedure (number of patients) Success Failed puncture/dilation Retained cystic duct stone Stages (number of patients) Single Multiple Duration of procedure-median (minutes) First 10 cases Last 50 cases Hospital stay (from initial stage)-median (days) Elective: single staged Acute Convalescence-median (days) Full recovery Employment

cases. 100 (89%) 6 7 72 28 166 51 2 5 12 12 18

Table 2. Stone size and number in 100 patients who underwent successful percutaneous cholecystolithotomy. Stone size (mm) uptos 6-10 11-1.5 16-20 21-25 26-30 Total

Number of patients 19 33 20 11 15 2 100

Stone number 1 2-5 6-10 1l-20 21-50 >50 Total

Number of of patients 24 29 12 16 11 8 100

1. Where a drainage track has already been established in a patient presenting with gallbladder sepsis and with large stones. A simple gallbladder clearance can be a definitive treatment, particularly if the patient is elderly and unfit. 2. In chronic cholecystitis where the gallbladder is contracted and firmly attached to the liver within the gallbladder fossa, and a laparoscopic cholecystostomy is considered impossible. 3. In cirrhosis, particularly in the presence of varices around the gallbladder and porta hepatis. In the author’s present practice over 90% of patients are suitable for laparoscopic methods, but there is a small but significant residuum of cases requiring interventional gallbladder procedures. GALLSTONE

DISSOLUTION

Stones formed predominantly of cholesterol can be successfully dissolved by methyl-t-butyl ether (MTBE) instilled either manually or through an

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oscillatory pump via a Foley catheter (Zakko et al, 1987). Although several successful series using this technique have been reported, the procedure is associated with several disadvantages. Gallstone composition can be only approximately assessed by high-resolution CT scanning, and although cholesterol may be successfully dissolved out, residual calcium carbonate or bile pigment crystals will remain in the majority of patients. These fragments are also unaffected by oral bile acid therapy and will undoubtedly remain as nidi for future gallstone formation. The agent MTBE is an inflammable, toxic material which is difficult to handle and if absorbed can produce anaesthesia in the patient. Spillage of MTBE on the peritoneal surfaces causes severe pain, and its toxicity to the gallbladder mucosa is unknown. GALLSTONE

RECURRENCE

All techniques that leave the gallbladder in situ carry the risk of subsequent formation of further stones or even of development of carcinoma (Burhenne and Stoller, 1985; So et al, 1990). Although stone extraction techniques can return a non-functioning gallbladder to normal function, which may provide considerable symptomatic relief, the evidence accumulated in the surgical literature is that the better the function the greaterthe likelihood that stones will reform (Dempsey JO, personal communication). The author has a cohort of 100 consecutive patients who had undergone PCCL with successful clearance and are being followed up by ultrasonography at three monthly intervals. The recurrence rate in this population is almost identical to that of the classic surgical literature, with a 30% recurrence rate at 2 years. SYMPTOMATIC GALLSTONES

Ultkound scan

Severe AC empyema

)

Immediate percutaneous cholecystostomy

FNA --t

‘Hot’ gallbladder

2 weeks PCCL /

Un~wli-@d

.___...+ Unfit -

f sphincterotomy

cholecystectomy

PCCL

Convert to mini-laparoscopic cholecystectomy

Figure 17. Protocol for management of gallbladder stone disease. AC, acute cholecystitis; CBD, common bile duct; FNA, fine-needle aspiration; PCCL, percutaneous cholecystolithotomy.

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Although virtually all the patients with recurrent stones are asymptomatic, it is likely that their symptoms will eventually recur, certainly by 5-10 years after the procedure (Wenckert and Robertson, 1966; Gracie and Ransohoff, 1982). All such gallbladder preserving procedures are only appropriate for elderly patients or those in whom poor gallbladder function contributes to the symptom complex (Aranha et al, 1982; Houghton et al, 1985; Huber et al, 1988). An alternative approach to the problem of stone recurrence is gallbladder ablation (Becker et al, 1988). Work on animals has demonstrated that the cystic duct can be satisfactorily occluded by electrocautery or by using bicap heater probes mounted on small catheters. Complete destruction of the gallbladder mucosa is difficult to achieve, as the epithelium tends to be preserved in the crypts and the Rokitansky-Aschoff sinuses and grows back to recolonize the gallbladder wall after a period of only a few weeks. Experiments have been performed with ethanol, sodium tetradecyl sulphate, hot contrast and with a neodymium-YAG laser. Approximately a dozen cases using ethanol and sodium tetradecyl sulphate have been reported, demonstrating that the technique is safe in clinical practice. However, this technique can only be considered as an alternative to laparoscopic cholecystectomy when the stone extraction and ablation can be performed at a single session and the indwelling catheter dispensed with. Aftercare It is essential to maintain continuous gallbladder drainage after any interventional procedure other than fine-needle aspiration. A period of at least 10 days is required for a sufficiently mature track to form to avoid leakage. The catheter size should be comparable with the largest instruments or dilators used. Thus a 30 FG track requires a 16-18 FG drainage catheter; a 12 FG track requires a 10 FG drain. Balloon catheters are preferred as they produce additional tamponade and the rubber will promote track formation. Other self-retaining catheters can cause problems, by pulling on or distorting the gallbladder wall. CLINICAL

PROTOCOLS

The author’s present management protocol for gallbladder stone disease is given in Figure 17. Every patient receives a careful ultrasound assessment to determine the stone burden, the presence of inflammatory changes in the gallbladder wall, the relationship of the gallbladder to the liver, the depth of the gallbladder fossa, the size of the common bile duct (CBD) and the presence of common duct stones. Cholangiography data obtained from the percutaneous cholecystolithotomy patients showed no CBD stones in patients with bile ducts of less than 6mm diameter. Where the CBD diameter exceeded 7 mm the incidence of stones was 50%. Patients with atypical symptoms or abnormal liver function tests require endoscopic retrograde cholangiography-pancreatography (ERCP) prior to surgery. The incidence of associated carcinoma of the bile duct or pancreas in the

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R. LEES

Figure 18. Gallbladder volume is assessed by measurement of its three major axes and calculated by the ellipsoid formula (A x B x C x 0.52).

author’s series of both percutaneous cholecystolithotomy and laparoscopic cholecystectomy patients is 2%, and a thorough preoperative ultrasound scan is essential. Gallbladder function can be assessed by ultrasound measurement before and after a fatty meal stimulus. A reduction in volume of more than 25% is considered normal (Figure 18) (Dodds et al, 1985). Interventional radiology of the gallbladder has come full circle but remains a vital adjunct to the surgical management of gallbladder disease. REFERENCES Ainley CC, Williams SJ, Smith AC, Hatfield ARW, Russell RCG & Lees WR (1991) Gallbladder sepsis after stent insertion for bile duct obstruction; management by percutaneous cholecystostomy. British Journal of Surgery 78: 961-963. Aranha GV, Sontag SJ & Greenlee HB (1982) Cholecystectomy in cirrhotic patients: a formidable operation. American Journal of Surgery 143: 55-59. Becker CDS, Quenville NF & Burhenne HJ (1988) Long term occlusion of the porcine cystic duct by means of endoluminal radiofrequency electrocoagulation. Radiology 167: 63-68. Burhenne HJ & Stoller JL (1985) Minicholecystostomy and radiologic stone extraction in high risk cholelithiasis patients. American Journal of Surgery 149: 632-635. Cope C, Burke DR & Meranze SG (1990) Percutaneous treatments for biliary disease. Radiology

176: 25-30.

Dodds WJ, Groh WJ, Danveesh RMA, LawtonTL, Kishk SM & Kern MK (1985) Sonographic measurement of gallbladder volume. American Journal of Roenfgenology 145: 1009-1011. Glen F (1981) Surgical management of acute cholecystitis in patients 65 years of age and older. American

Journal

of Surgery

193: 56-59.

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Gracie WA & Ransohoff DF (1982) The natural history of silent gallstones: the innocent gallstone is not a myth. New England Journal of Medicine 307: 798-800. Houghton PWJ, Jenkinson LR & Donaldson LA (1985) Cholecystectomy in the elderly: a prospective study. British Journal of Surgery 72: 220-222. Hruby W, Stack1 W, Urban M, Armbruster C & Marburger M (1989a) Percutaneous endoscopic cholecystolithotripsy. Work in progress. Radiology 173: 477479. Hruby W, Urgan M, Stack1 W, Armbruster C & Marburger M (1989b) Stone-bearing gallbladders: CTanatomy as the key to safe percutaneous lithotripsy. Radiology 173: 385-387. Huber DF, Martin EW Jr & Cooperman M (1988) Cholecystectomy in elderly patients. American Journal of Surgery 146: 719-721. Kellett MJ, Wickham JEA & Russell RCG (1988) Percutaneous cholecystolithotomy. British Medical

Journal

296: 453-455.

Lee MJ, Saini S, Brink JA et al (1991) Treatment of critically ill patients with sepsis of unknown cause: value of percutaneous cholecystostomy. American Journal of Roentgenology 156: 1163-1166. Lindemann SR, Tung G, Silverman SG & Mueller PR (1988) Percutaneous cholecystostomy. Seminars in Interventional Radiology 5: 179-185. McGahan JP & Linfors KK (1988) Acute cholecystitis: diagnostic accuracy of percutaneous aspiration of the gallbladder. Radiology 167: 669-671. Reddick EJ & Olsen DO (1989) Laparoscopic laser cholecystectomy: a comparison with minilap cholecystectomy. Surgical Endoscopy 3: 131-133. So CB, Gibney RG & Scudamore CH (1990) Carcinoma of the gallbladder: a risk associated with gallbladder-preserving treatment for cholelithiasis. Radiology 174: 127-130. Thornton JR, Heaton KW, Espiner HJ, Eltringham KW, Espiner HJ & Eltringham WK (1983) Empyema of the gallbladder: reappraisal of a neglected disease. Gut 24: 1183-1195. Van der Linden W & Sunzel H (1970) Early versus delayed operation for acute cholecystitis. A controlled clinical trial. American Journal of Surgery 120: 7-13. vansonnenberg E, Wing VW, Pollard JW & Casola G (1984) Life-threatening vagal reactions associated with percutaneous cholecystostomy. Radiology 151: 377. Vogelzang RL & Nemcek AA (1988) Towards painless percutaneous biliary procedures: new strategies and alternatives. Journal of Interventional Radiology 3: 131-134. Warren P, Kadir S & Dunnick RN (1988) Percutaneous cholecystostomy: anatomic considerations Radiology 168: 615-616. Wenckert A & Robertson B (1966) The natural course of gallstone disease. Eleven-year review of 781 nonoperated cases. Gastroenterology 50: 376-381. Wholey MH & Smoot S (1988) Choledocholithiasis: percutaneous pulverization with a highspeed rotational catheter (technical note). American Journal of Roentgenology 150: 129 130. Zagar SA, Khuroo MS, Mahajan Ret al (1991) US-guided fine needle aspiration biopsy of gall bladder masses. Radiology 179: 275-278. Zakko SF, Hofmann AF, Schteingart C, vansonnenberg E & Wheeler HO (1987) Percutaneous gallbladder stone dissolution using a microprocessor-assisted solvent transfer (MAST) system. Gastroenterology 92: 1794 (abstract).