INDICATION OVERVIEW

Acute cholecystitis is a sudden onset of inflammation of the gallbladder that causes severe abdominal pain. Abdominal pain is often accompanied by fever and abnormally high white blood cell count (leukocytes).¹ Acute cholecystitis is usually caused by gallstones obstructing the cystic duct.² This prevents the normal flow of bile in and out of the gallbladder into the bowel. Increased pressure in the gallbladder due to the obstruction results in inflammation and pain. Up to 14% of acute cholecystitis cases are acalculous.² In these patients, there is an obstruction but gallstones are not the cause. Acute acalculous cholecystitis usually occurs in patients who are already critically ill from another medical condition. Mortality and morbidity is high in patients with acute acalculous cholecystitis.

The initial treatment for acute cholecystitis in the emergency room is usually intravenous antibiotics, hydration, and analgesia. If inflammation of the gallbladder continues, removal of the gallbladder (cholecystectomy) is usually required.³

Complications of acute cholecystitis include gangrenous cholecystitis (gangrene of the gallbladder wall), gallbladder perforation (hole or piercing of the wall of the gallbladder), and emphysematous cholecystitis (acute infection of the gallbladder caused by gas-forming organisms). These complications occur in up to 20% of people with cholecystitis, have high mortality associated with them, and therefore require emergency surgery.²

Population: Patients with suspected acute cholecystitis.

Intervention: Cholescintigraphy.

Cholescintigraphy, also known as a hepatobiliary iminodiacetic (HIDA) scan, is a nuclear medicine test used to diagnose intrahepatic or extrahepatic obstruction of the bile ducts, gallbladder disease, and bile leaks. Before cholescintigraphy, patients are injected with a radiopharmaceutical tracer (technetium-99m [^99mTc]-iminodiacetic acid). Patients need to fast three to four hours before this injection to avoid gallbladder contraction.⁴ After injection, a gamma camera is used to detect gamma rays emitted by the patient from the injected radiopharmaceuticals. Images are created from the detected gamma rays. If there is no cystic duct blockage, the radiopharmaceutical will enter the gallbladder, which will be visualized in images created by the gamma camera. If a gallstone is obstructing a patient’s cystic duct, the radiopharmaceutical will not enter the gallbladder and visualization of the gallbladder cannot occur. Non-visualization of the gallbladder is indicative of acute cholecystitis. If the gallbladder is not seen one hour after injection, images should be retaken three to four hours after injection.⁵ This delayed imaging increases the specificity of cholescintigraphy for the diagnosis of acute cholecystitis. An alternative to delayed imaging is to inject the patient with a small amount of morphine sulphate (0.02 mcg/kg). Administration of morphine sulphate facilitates the flow of bile toward the cystic duct by causing contraction of the sphincter of Oddi. The injection of morphine sulphate can reduce the time to confirm the diagnosis from three or four hours to 1.5 hours.⁴

Comparators: For this report, the following diagnostic tests are considered as alternatives to cholescintigraphy:

• Computed Tomography (CT): In a CT scan, a rotating x-ray device moves around the patient and takes multiple detailed images of organs and body parts.⁶ Sometimes patients are injected with a contrast agent before images are taken, for better visualization of the body part being examined.⁶ CT findings consistent with acute cholecystitis include gallbladder wall thickening, gallbladder distention, pericholecystic fluid, and pericholecystic fat.
• Magnetic Resonance Cholangiopancreatography (MRCP): An MRCP is a magnetic resonance imaging (MRI) test that produces detailed images of the hepatobiliary and pancreatic systems. Images are created using a magnetic field and radiofrequency pulses. Patients undergoing MRI are placed on to a table that is moved into the centre of the MRI machine. Some patients are given contrast material before the MRI. MRCP findings indicative of acute cholecystitis include gallbladder stones, wall thickening, and pericholecystic fluid.⁷
• Ultrasound (U/S): During a U/S, a transducer is placed over the organ of interest. The transducer generates sound waves that pass through the body and produce echoes that are analyzed by a computer to produce images of the body part being analyzed.⁸ U/S findings consistent with acute cholecystitis include the visualization of gallstones, intraluminal sludge, thickening of the gallbladder wall, pericholecystic fluid, increased blood flow in the gallbladder wall, and sonographic Murphy’s sign.⁹ Murphy’s sign of cholecystitis refers to pain felt by the patient on taking a deep breath while pressure is placed in the right upper quadrant of the abdomen.¹⁰

Outcomes: Eleven outcomes (referred to as criteria) are considered in this report:

• Criterion 1: Size of the affected population
• Criterion 2: Timeliness and urgency of test results in planning patient management
• Criterion 3: Impact of not performing a diagnostic imaging test on mortality related to the underlying condition
• Criterion 4: Impact of not performing a diagnostic imaging test on morbidity or quality of life related to the underlying condition
• Criterion 5: Relative impact on health disparities
• Criterion 6: Relative acceptability of the test to patients
• Criterion 7: Relative diagnostic accuracy of the test
• Criterion 8: Relative risks associated with the test
• Criterion 9: Relative availability of personnel with expertise and experience required for the test
• Criterion 10: Accessibility of alternative tests (equipment and wait times)
• Criterion 11: Relative cost of the test.

Definitions of the criteria are in Appendix 1.

METHODS

The literature search was performed by an information specialist using a peer-reviewed search strategy.

Published literature was identified by searching the following bibliographic databases: MEDLINE with In-Process records and daily updates via Ovid; The Cochrane Library (2011, Issue 2) via Wiley; and PubMed. The search strategy consisted of both controlled vocabulary, such as the National Library of Medicine’s MeSH (Medical Subject Headings), and keywords. The main search concepts were radionuclide imaging and cholecystitis.

Methodological filters were applied to limit retrieval to health technology assessments, systematic reviews, meta-analyses, randomized controlled trials, and non-randomized studies, including diagnostic accuracy studies. The search was limited to English language. No date limits were applied for the systematic review search. The primary studies search was limited to documents published between January 1, 1996, and March 2, 2011. Regular alerts were established to update the search until October 2011. Detailed search strategies are located in Appendix 2.

Grey literature (literature that is not commercially published) was identified by searching relevant sections of the CADTH Grey Matters checklist. Google was used to search for additional web-based materials. The searches were supplemented by reviewing the bibliographies of key papers. See Appendix 2 for more information on the grey literature search strategy.

Targeted searches were done as required for the criteria, using the aforementioned databases and Internet search engines. When no literature was identified that addressed specific criteria, experts were consulted.

SEARCH RESULTS

Fourteen articles^11–24 were identified through the MA/SR/HTA search; of those, eight^{13–18,21,24} underwent full text review. One systematic review¹⁵ was identified from the full text review that compared the diagnostic accuracy of cholescintigraphy with one of the alternative imaging modalities.

A review of primary studies was conducted to identify studies that directly compared the diagnostic accuracy of cholescintigraphy with one of its alternatives. Four primary studies^25–28 were found that compared cholescintigraphy with U/S. No primary studies were identified that directly compared cholescintigraphy with CT, with MRCP, or with ERCP. Articles from the grey literature search were used to address criterion 1 (one article)²⁹ and criterion 8 (one article).³⁰ Articles from the primary study search were used to help address criterion 1 (one article),³¹ criterion 3 (one article),³² criterion 6 (four articles), and criterion 8 (two articles).

Literature from targeted searches was used to supplement the articles identified in the primary study search. When no literature was identified addressing specific criteria, experts were consulted.

SUMMARY TABLE

Table 1. Summary of Criterion Evidence (PDF, 209K)

CRITERION 4: Impact of not performing a diagnostic imaging test on morbidity or quality of life related to the underlying condition (link to definition)

If a test for diagnosing acute cholecystitis is not available, treatment might be delayed and patients may have to suffer symptoms of acute cholecystitis longer than necessary. Additionally, delayed treatment may make patients more susceptible to complications that could affect their survival or their quality of life.

Two studies were identified that evaluated the quality of life impact of acute cholecystitis. A 2005 Norwegian study by Vetrhus et al.⁵¹ compared the quality of life over a five-year period of 64 patients presenting at their institution with acute cholecystitis. Patients were randomized to one of two treatment groups (all patients treated conservatively with antibiotics): observation, or cholecystectomy. Quality of life was assessed using the Psychological General Well-Being index (PGWB) and the Nottingham Health Profile (NHP) part II. Pain was evaluated using a pain score and a visual analogue pain scale (VAPS). No statistically significant differences between the two treatment groups over time were found in any of the instruments. However, the differences in mean scores in the quality of life and pain instruments at randomization and at five years reflect the morbidity impact of the acute cholecystitis episode. Table 2 presents selected findings of the study.

Table 2

Selected Results Reported in Vetrhus et al. 2005.

Bass et al.⁵² estimated the quality of life impact of different types and treatments of gallbladder disease. After being presented with descriptions of different diseases and procedures, 40 subjects (without gallstones) provided preference scores by means of either a simple 0 to 100 rating scale (n = 22; score of 0 = immediate death and 100 = perfect health) or standard gamble (n = 18). The relative mean rating score — rated relative to other related conditions — for an episode of acute cholecystitis was 0.36 and 0.77 by standard gamble.

Return to Summary Table

CRITERION 7: Relative diagnostic accuracy of the test (link to definition)

One systematic review¹⁵ was identified that evaluated the diagnostic accuracy of cholescintigraphy with U/S in patients suspected to have acute cholecystitis. This review was somewhat dated (1994) and the majority of studies included were not head-to-head comparisons of cholescintigraphy and U/S. No systematic reviews were identified that compared cholescintigraphy with CT or MRCP. Therefore, a search for primary diagnostic accuracy studies comparing cholescintigraphy with any of the alternatives (U/S, CT, and MRCP) was conducted. Four primary studies were identifed that compared the diagnostic accuracy of cholescintigraphy to U/S.^25–28 Three of the studies reported sensitivity, specificity, or both sensitivity and specificity of the diagnostic test.^25,27,28 The other study reported only the correlation of findings between cholescintigraphy and U/S. No primary studies were found that compared cholescintigraphy with CT or MRCP.

Cholescintigraphy versus U/S

Table 3 presents the sensitivity and specificity reported in one systematic review¹⁵ and three primary studies^25,27,28 that compared the diagnostic accuracy of cholescintigraphy and U/S for acute cholecystitis. In their systematic review, Shea et al.¹⁵ estimated the sensitivity of cholescintigraphy and U/S to be 0.97 (95% confidence interval [CI], 0.96 to 0.98) and 0.88 (95% CI, 0.74 to 1.0), respectively. They estimated the specificity of cholescintigraphy to be 0.90 (95% CI, 0.86 to 0.95) and the specificity of U/S to be 0.80 (95% CI, 0.62 to 0.98). The sensitivity and specificity estimates incorporated an adjustment to account for verification bias.

Table 3

Sensitivity and Specificity of Cholescintigraphy and Ultrasonography.

The three primary retrospective studies all found cholescintigraphy to have higher sensitivity than U/S for the diagnosis of acute cholecystitis. Chatziioannou et al.²⁷ found the sensitivity of cholescintigraphy and U/S to be 0.88 and 0.50, respectively. Kalimi et al.²⁸ reported the sensitivity of cholescintigraphy and U/S to be 0.86 and 0.48, respectively, while Alobaidi et al.²⁵ reported the sensitivity of cholescintigraphy and U/S to be 0.91 and 0.62, respectively. In their study, Chatziioannou et al.²⁷ found the specificity of cholescintigraphy to be 0.93 compared with 0.88 for U/S. In all three of these primary studies, findings from the imaging tests were compared with histopathological findings of the same patients suspected of acute cholecystitis. In Chatziioannou et al.,²⁷ all 107 patients in the study underwent both cholescintigraphy and U/S.

Tables 3 and 4 present other diagnostic findings from primary studies. Chatziioannou et al.²⁷ found the overall accuracy of cholescintigraphy and U/S to be 0.92 and 0.77, respectively. Blaivas et al.²⁶ found the correlation between the diagnosis of acute cholecystitis with cholescintigraphy and U/S to be 0.74.

Table 4

Other Measures of Diagnostic Accuracy for Cholescintigraphy and Ultrasonography.

Cholescintigraphy versus CT

No studies were identified that compared the diagnostic accuracy of cholescintigraphy and CT scan.

Cholescintigraphy versus MRCP

No studies were identified that compared the diagnostic accuracy of cholescintigraphy and MRCP.

Details of the diagnostic accuracy studies can be found in Appendix 3.

Return to Summary Table

CRITERION 8: Relative risks associated with the test (link to definition)

Non–radiation-related Risks

Cholescintigraphy

Risks associated with cholescintigraphy include allergy to HIDA, pain during cholecystokinin (CCK) injection (causes gallbladder contraction), chills, nausea, and rash. In susceptible subjects, CCK has induced panic attacks.⁴⁰ Rapid administration of CCK has been associated with deterioration in blood gases and respiratory function in infants. In a study of 18 subjects, slow infusion of CCK resulted in no adverse reactions, specifically abdominal pain, which was present in the group that had a bolus injection. Slow infusion of CCK is now a well-recognized practice (MIIMAC expert opinion).

CT

Some patients may experience an allergic reaction to the contrast agent (if required), which may worsen with repeated exposure.⁴¹ In addition, patients may experience mild side effects from the contrast agent such as nausea, vomiting, or hives. A 2009 retrospective review of all intravascular doses of low-osmolar iodinated and Gd contrast materials administered at the Mayo Clinic between 2002 and 2006 (456,930 doses) found that 0.15% of patients given CT contrast material experienced side effects, most of which were mild. A serious side effect was experienced by 0.005% of patients.⁵³ CT is contraindicated in patients with elevated heart rate, hypercalcemia, and impaired renal function.⁴²

MRI

MRI is contraindicated in patients with metallic implants, including pacemakers.⁴³ MRI is often used in conjunction with the contrast agent Gd. Some patients may experience an allergic reaction to the contrast agent (if required), which may worsen with repeated exposure.⁴¹ Side effects of Gd include headaches, nausea, and metallic taste. Gd is contraindicated in patients with renal failure or end-stage renal disease, as they are at risk of nephrogenic systemic fibrosis. According to the American College of Radiology Manual on Contrast Media,⁴² the frequency of severe, life-threatening reactions with Gd is extremely rare (0.001% to 0.01%). Moderate reactions resembling an allergic response (i.e., rash, hives, urticaria) are also very unusual and range in frequency from 0.004% to 0.7%.⁴²

U/S

There are no reported risks associated with U/S in the literature that was reviewed.

Radiation-related Risks

Among the modalities to diagnose acute cholecystitis, cholescintigraphy, CT, and ERCP expose the patient to ionizing radiation. The average effective dose of radiation delivered with each of these procedures can be found in Table 5.

Table 5

Effective Radiation Doses for Various Imaging Tests.

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CRITERION 9: Relative availability of personnel with expertise and experience required for the test (link to definition)

Cholescintigraphy

In Canada, physicians involved in the performance, supervision, and interpretation of cholescintigraphy should be nuclear medicine physicians or diagnostic radiologists with training or expertise in nuclear imaging.⁵⁶ Physicians should have a Fellowship of Certification in Nuclear Medicine or Diagnostic Radiology with the Royal College of Physicians and Surgeons of Canada and/or the Collège des médecins du Québec. Nuclear medicine technologists are required to conduct hepatobiliary scans. Technologists must be certified by the Canadian Association of Medical Radiation Technologists (CAMRT) or an equivalent licensing body.

All alternative imaging modalities

In Canada, physicians involved in the performance, supervision, and interpretation of diagnostic CT scans, MRI, and U/S should be diagnostic radiologists⁴⁷ and must have a Fellowship or Certification in Diagnostic Radiology with the Royal College of Physicians and Surgeons of Canada and/or the Collège des médecins du Québec. Foreign-trained radiologists also are qualified if they are certified by a recognized certifying body and hold a valid provincial license.⁵⁶

Service engineers are needed for system installation, calibration, and preventive maintenance of the imaging equipment at regularly scheduled intervals. The service engineer’s qualification will be ensured by the corporation responsible for service and the manufacturer of the equipment used at the site.

Qualified medical physicists (on-site or contracted part-time) should be available for the installation, testing, and ongoing quality control of CT scanners, MR scanners, and nuclear medicine equipment.⁵⁶

CT

For the performance of CT scan, medical radiation technologists who are certified by CAMRT, or an equivalent licensing body recognized by CAMRT, are required. The training of technologists specifically engaged in CT should meet with the applicable and valid national and provincial specialty qualifications.

MRCP

Medical technologists must have CAMRT certification in magnetic resonance or be certified by an equivalent licensing body recognized by CAMRT.

U/S

Sonographers (or ultrasonographers) should be graduates of an accredited school of sonography or have obtained certification by the Canadian Association of Registered Diagnostic Ultrasound Professionals. They should be members of their national or provincial professional organization. Sonography specialties include general sonography, vascular sonography, and cardiac sonography.⁴⁷ In Quebec, sonographers and medical radiation technologists are grouped together; in the rest of Canada, sonographers are considered a distinct professional group.⁴⁷

The availability of expertise to diagnose acute cholecystitis varies across the jurisdictions. Table 6 reports the number of medical imaging professionals nationally and highlights those provinces and territories that lack a specific expertise. Gastroenterologists are not included in this list; however, the number of gastroenterologists in Canada available to perform the procedure is reported to be 1.83 per 100,000 persons.⁵⁷

Table 6

Medical Imaging Professionals in Canada.

Return to Summary Table

CRITERION 10: Accessibility of alternative tests (equipment and wait times) (link to definition)

There are notable variations in the availability of medical imaging technologies across Canada. Table 7 provides an overview of the availability of equipment required to diagnose acute cholecystitis. Data for nuclear medicine cameras (including SPECT) are current to January 1, 2007. The number of CT, MRI, and SPECT/CT scanners is current to January 1, 2010. Data were not available for U/S.

Table 7

Diagnostic Imaging Equipment in Canada.

Cholescintigraphy

To perform cholescintigraphy, nuclear medicine facilities with gamma cameras (including SPECT) are required. Three jurisdictions, the Yukon, the Northwest Territories, and Nunavut, do not have any nuclear medicine equipment.⁴⁷

CT

No CT scanners are available in Nunavut.⁴⁸ The average weekly use of CT scanners ranged from 40 hours in PEI to 69 hours in Ontario, with a national average of 60 hours.⁴⁷ In 2010, the average wait time for a CT scan in Canada is 4.2 weeks.⁴⁹

ERCP

ERCP is an x-ray–based test. X-ray machines are widely available across the country.

MRCP

MRCP is an MRI based test. No MRI scanners available in the Yukon, Northwest Territories, or Nunavut.⁴⁸ According to CIHI’s National Survey of Selected Medical Imaging Equipment database, the average number of hours of operation per week for MRI scanners in 2006–2007 ranged from 40 hours in PEI to 99 hours in Ontario with a national average of 71 hours.⁴⁷ In 2010, the average wait time for MR imaging in Canada was 9.8 weeks.⁴⁹

U/S

U/S machines are widely available across the country. According to the Fraser Institute, the average wait time for U/S in 2010 was 4.5 weeks.

Return to Summary Table

CRITERION 11: Relative cost of the test (link to definition)

Fee codes from the Ontario Schedule of Benefits were used to estimate the relative costs of cholescintigraphy and its alternatives. Technical fees are intended to cover costs incurred by the hospital (i.e., radiopharmaceutical costs, medical/surgical supplies, and non-physician salaries). Maintenance fees are not billed to OHIP — estimates here were provided by St. Michael’s Hospital in Toronto. Certain procedures (i.e., PET scan, CT scan, MRI scan) are paid for, in part, out of the hospital’s global budget — these estimates were provided by The Ottawa Hospital. It is understood that the relative costs of imaging will vary from one institution to the next.

According to our estimates (Table 8), the cost of cholescintigraphy with ^99mTc-based radioisotopes is $298.38. CT is minimally more costly, MRCP is moderately more costly, and U/S is minimally less costly. An estimate for ERCP could not be obtained; however, actual costs (i.e., excluding professional fees) obtained from one Ontario hospital were reported to be approximately $1900. Therefore, ERCP is a significantly more costly alternative.

Table 8

Cost Estimates Based on the Ontario Schedule of Benefits for Physician Services Under the Health Insurance Act (September 2011).

Return to Summary Table

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APPENDICES