Oral cholecystography vs gallbladder sonography: a prospective, blinded reappraisal

The role of (99m)technetium-labelled hepato imino diacetic acid (HIDA) scan in the management of biliary pain

OBJECTIVE

To assess the outcome of laparoscopic cholecystectomy on the basis of an abnormal provocative (99m)technetium-labelled hepato imino diacetic acid (HIDA) scan for patients with typical biliary pain and normal trans-abdominal ultrasound (TUS) scan.

PATIENTS AND METHODS

Prospective data were collected for 1201 consecutive patients with typical biliary symptoms. Patients who were found to have a normal TUS and upper GI endoscopy subsequently underwent cholescintigraphy (HIDA scan). Patients with an abnormal HIDA scan, i.e.<40% ejection fraction with Sincalide (cholecystokinin octapeptide)--were offered cholecystectomy. Symptoms and histology were reviewed postoperatively.

RESULTS

In all, 48/1201 (4%) patients with typical biliary symptoms had a normal ultrasound and endoscopy; 35/48 patients had an abnormal provocative HIDA scan and all underwent laparoscopic cholecystectomy. Histology in all cases revealed chronic cholecystitis and 18 patients had sludge or microlithiasis within the gallbladder. At 6-week follow-up, 31 of the 35 patients were completely asymptomatic or improved. Furthermore, 79% of patients remained symptom-free or improved at a median follow-up of 28.5 months (range 4-70).

CONCLUSIONS

HIDA scan is a useful clinical tool as an adjunct to the diagnosis and management of patients who present with typical biliary pain and a normal TUS scan.

Gallbladder stones: imaging and intervention

Imaging of the gallbladder for cholelithiasis and its complications has changed dramatically in recent decades along with expansion of interventional techniques related to the disease. Ultrasonography (US) is the method of choice for detection of gallstones. The characteristic US findings of gallstones are a highly reflective echo from the anterior surface of the gallstone, mobility of the gallstone on repositioning the patient, and marked posterior acoustic shadowing. Oral cholecystography remains an excellent method of gallstone detection, but its role has been limited due to the advantages of US. Most people with cholelithiasis will not experience symptoms or complications related to gallstones. When biliary colic does occur, it is typically caused by transient obstruction of the cystic duct by a stone. The primary imaging modality in suspected acute calculous cholecystitis is usually US or cholescintigraphy. Detection of gallstones alone does not permit a diagnosis of acute cholecystitis; however, secondary US findings provide more specific information. In detection of choledocholithiasis, endoscopic retrograde cholangiopancreatography and magnetic resonance cholangiopancreatography are superior to US. In certain clinical settings, interventional radiologic procedures have become an important alternative to surgery in the treatment of gallstones and their complications; techniques include percutaneous cholecystostomy and gallstone removal.

Accuracy of ultrasound and oral cholecystography in assessing the number and size of gallstones: implications for non-surgical therapy

Prior to non-surgical therapy of gallstones it is important to assess their number and size. In order to evaluate the accuracy of ultrasound (US) and oral cholecystography (OCG) in counting and measuring gallstones, a prospective blind study was conducted to compare the results of US (n = 99) and OCG (n = 36), either alone or in combination (n = 34), with the number and size of gallstones retrieved after cholecystectomy. The number of gallstones was accurately estimated by US and OCG in 74% and 69% of the cases, respectively. In assessing the presence of up to three, five or 10 gallstones both US and OCG proved reliable. In measuring the size of gallstones, there was 19% accuracy with US compared with only 3% with OCG. With an accepted measurement error of 3 mm these values increased to 80% for US and 44% for OCG. US proved more reliable than OCG in discriminating gallstones smaller or larger than 10 mm and smaller or larger than 20 mm, but with US, detection of gallstones larger than 30 mm was problematic. Both US and OCG underestimated gallstone size. The combination of both techniques did not significantly improve the assessment of either number or size of gallstones compared with the results obtained with US or OCG alone. It is concluded that (1) both US and OCG have some limitations in assessing the number and size of gallstones, (2) the combination of both examinations does not improve accuracy, and (3) patient selection for non-surgical treatment of gallstones can be started by US alone.

An audit of ultrasound diagnosis of gallbladder calculi

Many series suggest that ultrasound is an accurate method for demonstrating cholelithiasis. However, these series were often prospective and the examinations performed by experienced sonographers. This audit addresses whether the accuracy is maintained in daily practice. We reviewed the ultrasound scans of 128 patients who underwent cholecystectomy for cholelithiasis and compared the findings. The operative and ultrasound findings were at variance in eight of the 128 patients (6.2%). Five were reported as having gallstones on ultrasound but none were found at cholecystectomy, a false positive rate for ultrasound of 3.9%. Three had abnormal gallbladders with no gallstones on ultrasound but gallstones were found at operation, a false negative rate of 2.3%. To avoid false positive diagnoses, suboptimal examinations should be repeated and the scan should be repeated immediately pre-operatively if only small calculi are seen. Alternative imaging should be performed if necessary, either cholescintigraphy in the acute situation or elective oral cholecystography. Some false negative examinations may be avoided by performing repeat examinations if the gallbladder is thick-walled and tender. With these provisos we conclude that ultrasound correctly diagnoses cholelithiasis in daily practice.

The value of sonography in determining cystic duct patency

A prospective blinded comparison of ultrasonography (US) and oral cholecystography (OCG) was performed in 100 patients with symptomatic gall-stones to determine whether US would enable an accurate assessment of cystic duct patency to be made. Patency of the cystic duct was defined as gall-bladder opacification on OCG or a greater than 20% decrease in gall-bladder volume by US post-fatty meal. The ellipsoid method of volume measurement was used. Any patient who had a non-opacified gall-bladder on OCG but a greater than 20% volume decrease on US had cholescintigraphy performed (DISIDA). Oral cholecystography demonstrated cystic duct patency in 88 patients (88%), and fatty-meal gall-bladder US met the specified study criteria for patency in 86 patients (86%). False negative results were identified in four of the OCG and in six of the US examinations. The results of this study indicate that gall-bladder sonography with a post-fatty meal contraction of greater than 20% is a very accurate predictor of cystic duct patency. A contraction of less than 20%, however, cannot be considered a reliable predictor of cystic duct occlusion.

Acute cholecystitis: radiological management

Acute cholecystitis is a common condition which may be difficult to diagnose with confidence on clinical grounds alone. A large number of techniques are now available for imaging the gall bladder but, in practice, ultrasonography and cholescintigraphy are of greatest value. The former is cheap, readily available and features such as the presence of gall stones, gall bladder wall inflammation and a positive sonographic Murphy sign strongly suggest the diagnosis of acute cholecystitis. In addition to its diagnostic uses, ultrasonographically guided percutaneous cholecystostomy provides an alternative and sometimes life-saving form of treatment in those patients who are unfit for surgery. Cholescintigraphy is a highly accurate, non-invasive method for assessing patency of the cystic duct but is not always available in the emergency situation and takes longer to perform than an ultrasound examination. Acute cholecystitis, however, has many manifestations and may be calculous or acalculous, be associated with a patent or obstructed cystic duct, and may be complicated or uncomplicated. Imagining modalities other than those mentioned above may be useful in certain circumstances and this chapter aims to present the advantages and disadvantages of each technique in order to provide guidance for the clinician caring for a patient with suspected acute cholecystitis.

Accuracy of ultrasound in counting and measuring gallstones

A prospective study of accuracy of ultrasound in measuring and counting gallstones was undertaken in 30 patients undergoing cholecystectomy. Stones were correctly counted (up to five) in 27 of 30 patients. Ninety-three of 106 stones (88%) examined were measured accurately (with a 2 mm error margin). The size of the smaller stones tended to be overestimated, whereas the size of the larger stones tended to be underestimated. When nonoperative treatment of gallstones is considered, ultrasound can be used as the first examination to identify patients who will not be eligible for one or another protocol on the basis of size or number of stones.

Medical imaging

There is now a wide choice of medical imaging to show both focal and diffuse pathologies in various organs. Conventional radiology with plain films, fluoroscopy and contrast medium have many advantages, being readily available with low-cost apparatus and a familiarity that almost leads to contempt. The use of plain films in chest disease and in trauma does not need emphasizing, yet there are still too many occasions when the answer obtainable from a plain radiograph has not been available. The film may have been mislaid, or the examination was not requested, or the radiograph had been misinterpreted. The converse is also quite common. Examinations are performed that add nothing to patient management, such as skull films when CT will in any case be requested or views of the internal auditory meatus and heal pad thickness in acromegaly, to quote some examples. Other issues are more complicated. Should the patient who clinically has gall-bladder disease have more than a plain film that shows gall-stones? If the answer is yes, then why request a plain film if sonography will in any case be required to 'exclude' other pathologies especially of the liver or pancreas? But then should cholecystography, CT or scintigraphy be added for confirmation? Quite clearly there will be individual circumstances to indicate further imaging after sonography but in the vast majority of patients little or no extra information will be added. Statistics on accuracy and specificity will, in the case of gall-bladder pathology, vary widely if adenomyomatosis is considered by some to be a cause of symptoms or if sonographic examinations 'after fatty meals' are performed. The arguments for or against routine contrast urography rather than sonography are similar but the possibility of contrast reactions and the need to limit ionizing radiation must be borne in mind. These diagnostic strategies are also being influenced by their cost and availability; purely pragmatic considerations are not infrequently the overriding factor. Non-invasive methods will be preferred, particularly sonography as it is far more acceptable by not being claustrophobic and totally free of any known untoward effects. There is another quite different but unrelated aspect. The imaging methods, apart from limited exceptions, cannot characterize tissues as benign or malignant, granulomatous or neoplastic; cytology or histology usually provides the answer. Sonography is most commonly used to locate the needle tip correctly for percutaneous sampling of tissues. Frequently sonography with fine needle aspiration cytology or biopsy is the least expensive, safest and most direct route to a definitive diagnosis. Abscesses can be similarly diagnosed but with needles or catheters through which the pus can be drained. The versatility and mobility of sonography has spawned other uses, particularly for the very ill and immobile, for the intensive therapy units and for the operating theatre, as well in endosonography. The appointment of more skilled sonographers to the National Health Service could make a substantial contribution to cost-effective management of hospital services. Just when contrast agents and angiography have become safe and are performed rapidly, they are being supplanted by scanning methods. They are now mainly used for interventional procedures or of pre-operative 'road maps' and may be required even less in the future as MRI angiography and Doppler techniques progress. MRI will almost certainly extent its role beyond the central nervous system (CNS) should the equipment become more freely available, especially to orthopaedics. Until then plain films, sonography or CT will have to suffice. Even in the CNS there are conditions where CT is more diagnostic, as in showing calculations in cerebral cysticercosis. Then, too, in most cases CT produces results comparable to MRI apart from areas close to bone, structures at the base of the brain, in the posterior fossa and in the spinal cord. Scintigraphy for pulmonary infarcts and bone metastases and in renal disease in children plays a prominent role and its scope has increased with new equipment and radionuclides. Radio-immunoscintigraphy in particular is likely to expand greatly not only in tumour diagnosis but also in metabolic and infective conditions. Whether the therapeutic implications will be realized is more problematic. The value of MRS and NM for metabolic studies in clinical practice is equally problematical, although the data from cerebral activity are extremely interesting. While scanning has replaced many radiographic examinations, endoscopy has had a similar effect on barium meals and to a lesser extent on barium enemas. The combined visual/sonographic endoscope is likely to accelerate this process. There is no doubt that over the last 2 decades medical imaging has changed the diagnostic process, but its influence on the outcome of disease other than infections is less certain and probably indefinable. Data concerning the comparative efficacy in terms of patient outcome for each of the imaging techniques would be of considerable interest and a great help in determining diagnostic strategies.

Pathophysiology and treatment of gallstones

Spurred on by the discovery of "lithogenic bile" as a precursor, there has been much attention focused on the pathophysiology and treatment of gallstones. The article reviews the progress to date regarding the epidemiology, pathophysiology, diagnosis, therapy, and recurrence/prevention of gallstones.

Preferred imaging techniques for the diagnosis of cholecystitis and cholelithiasis

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