• 
• 

Three Part Question

In [patients with upper abdominal pain], is [ultrasound scan comparable to CT scan] in [identifying the cause of acute pancreatitis]?

Clinical Scenario

A 51 year old male attends the accident and emergency department with acute severe epigastric pain. You suspect that he may have acute pancreatitis and have sent off bloods for his serum amylase level to confirm the diagnosis.
You wonder if an ultrasound scan or a CT scan at this stage is better in identifying the cause of his condition.

Search Strategy

Medline and EMBASE 1966 to June Week 4 2006 using Ovid Interface.
({[pancreatitis.mp. or exp Pancreatitis, Acute Necrotizing/ or exp Pancreatitis/ or exp Pancreatitis, Alcoholic/] AND [exp Ultrasonography/ or ultrasound scan.mp.] AND [exp Tomography, X-Ray Computed/ or CT scan.mp.]} limit to human and English and adults(18 to 64 years))

Search Outcome

353 papers were found in total of which 3 were relevant. They are shown in the table below.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Y H. Su, C H. Lee, C H. Shiesh, S C. Lin, C Y. et al. 1988 Taiwan	88 patients with acute pancreatitis between 1986 and 1987. Pancreatitis diagnosed by serum amylase, lipase and pancreatic isoenzyme levels 10s.d. above mean	Diagnostic study	Gallstone pancreatitis	US sens 71.8%, spec 98.0%, PPV 96.6%, NPP 81.4%. accuracy 86.4%	Different goldstandards used Sample size not justified. Not all patients had CT scan because of urgent operations
				CT sens 52.9%, spec 100%, PPV 100%, NPP 73.3% accuracy 79.5%
				US+CT sens 82.1% spec 100%, PPV100%, NPP 87.5%, accuracy 93.2%
				US+biochemical test sens 94.9%, spec 100%, PPV 100%, NPP 96.1%, accuracy 97.7%
				Conclusion: US+biochemical test is the best non-invasive method to rapidly detect gallstone
Harvey, R T. Miller, W T Jr. 1999 USA	123 patients with acute pancreatitis who underwent both CT and US in the first 48hrs of each other between year 1995 and 1996	Retrospective diagnostic evaluation	Gallstone pancreatiits	US as initial imagining: sens 83%, spec 95%, PPV 75%, NPV 97%
				CT as initial imagining: sens 39%, spec 93%, PPV 50%, NPV 89%
				Conclusion: US is more sensitive than CT in identifying acute gallstone pancreatitis
Liu, C L. Lo, C M. Chan, J K. Poon, R T. Fan, S T 2000 China	89 patients with acute pancreatitis from 1996 to 1997 Gold standards: conventional US, CT or both.	Diagnostic study	Gallstone pancreatitis	US+/CT:=64 patients (71.9%). After EUS=78patients (87.6%)	EUS was only performed in patients with idiopathic pancreatitis, the overall effectiveness of EUS in identifying gallstone pancreatitis was not tested.
			Idiopathic pancreatitis	US+/CT=18 patients (20.2%). After EUS=4 patients (4.5%)
				Conclusion: EUS can identify gallstone in a large number of patients classified as having idiopathic pancreatitis by conventional radiological examinations

Comment(s)

Ultrasound scan is non-invasive, does not involve ionizing radiation and it can be performed at bedside. It can be accessed more readily than CT scan. All three papers found were in favour of ultrasound scan as an initial radiological investigation. It is a more sensitive test than CT scan in identifying gallstone. One study suggests that a combination of ultrasound scan and biochemical tests is best in predicting gallstone pancreatitis.

Clinical Bottom Line

Ultrasound scan is a more useful test in identifying acute gallstone pancreatitis than CT scan based on the evidence above.

References

1. Y H. Su, C H. Lee, C H. Shiesh, S C. Lin, C Y. et al Clinical significance of ultrasonography, computed tomography, and biochemical tests in the rapid diagnosis of gallstone-related pancreatitis: a prospective study. Pancreas. 3(2):153-8, 1988.
2. Harvey, R T. Miller, W T Jr. Acute biliary disease: initial CT and follow-up US versus initial US and follow-up CT. Radiology. 213(3):831-6, 1999 Dec.
3. Liu, C L. Lo, C M. Chan, J K. Poon, R T. Fan, S T. EUS for detection of occult cholelithiasis in patients with idiopathic pancreatitis. Gastrointestinal Endoscopy 51(1):28-32, 2000 Jan.