Acute Abdomen

Rationale and Objectives

We sought to assess retrospectively the added value of coronal reformations from isotropic voxels obtained with 64-slice multidetector row computed tomography (CT) of the acute abdomen.

Materials and Methods

This retrospective study was approved by the institutional review board and informed consent was waived. Multidetector helical 64-section CT (section thickness, 0.6 mm; pitch 1.75; table speed 35 mm/sec) was performed in 100 patients (60 women and 40 men; age range, 9∓85 years; mean age, 45.2 years) with acute nontraumatic abdominal pain who had been referred from the emergency department. Axial images were reconstructed with 5-mm-thick sections at 5-mm intervals. The second data set was reformatted coronally, with 3-mm-thick sections at 3-mm intervals. Four independent, blinded readers with various level of training interpreted first the axial scans alone and then followed immediately by the coronal scans. Confidence in the visualization of anatomy and pathology was scored on a 5-point scale. The final diagnosis was determined by surgical and pathologic reports and by clinical follow-up in those who did not undergo surgery.

Results

Based upon the individual patient’s clinical history and other comorbid factors, 92 patients received intravenous contrast and 90 patients received oral contrast. In 45 patients, no CT abnormalities were detected for an explanation of the abdominal pain. Mean sensitivity and specificity of axial CT alone were 92.5% and 91%, respectively. No significant differences in sensitivity and specificity were observed for the use of combined axial and coronal images. For the most inexperienced reader, the coronal reformations were helpful in 95% of cases, while for the most experienced reader, the coronal reformations were helpful in 35% of the cases. The coronal images were deemed helpful in an average of 62.3% of the cases for the four readers. However, diagnosing subtle pathology in the abdominal wall was difficult on coronal reformations alone. Overall, coronal reformations improved diagnostic confidence and interobserver agreement over axial images alone for visualization of normal abdominal structures and in the diagnosis of abdominal pathology.

Conclusion

Axial and coronal reformations of 64-section multidetector row CT have equal sensitivity and specificity for the diagnosis of acute abdominal pathology. However, coronal reformations improved the diagnostic confidence for all readers but most significantly for the least experienced. Therefore, radiology departments with residents should consider routinely generating coronal images in patients with acute abdominal pain.

A wide variety of potential life-threatening medical and surgical diseases can cause acute abdominal pain; thus, the management of patients with acute abdominal syndrome requires an accurate and rapid diagnosis to reduce morbidity and mortality and to direct proper management.

Spiral computed tomography (CT) has become the investigation of choice in the imaging evaluation of patients with acute abdominal pain because it is rapid, cost-effective and provides a global perspective of abdominal structures. Numerous studies indicate that CT provides useful diagnostic information in the evaluation of patients with acute abdominal pain ( ). The increased availability of multidetector row CT (MDCT) in emergency departments results in near universal utilization.

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Patients and methods

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Imaging Technique

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Imaging Evaluation

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Statistical Analysis

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Results

Image Quality

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Table 1

Mean Confidence Score for the Detection of Different Organ Systems for Four Readers

Scan Liver Gallbladder Pancreas Adrenal Glands Kidney Spleen Small Intestines Colon Urinary Bladder Genital Organs Vessels Lymph Nodes Skeleton Transverse Alone 4.77 4.02 4.60 4.56 4.79 4.80 4.48 4.54 4.26 4.02 4.80 4.70 4.91 Transverse and coronal 4.78 4.02 4.52 4.62 4.76 4.80 4.50 4.61 4.28 4.03 4.79 4.72 4.88P value ⁎ .861 .910 <.01 <.05 .065 .561 .491 .01 .236 .451 .589 .617 .154

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Abnormalities Detected at CT

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Table 2

Principal Findings on CT Scans. (Number of Patients)

Normal findings 30 No acute pathology 15 Cholecystitis/cholelithiasis 4 Abscess 7 Pancreatic cancer 2 Gallbladder cancer 1 Acute/chronic pancreatitis 5 Hydronephrosis/calculi 4 Small bowel ileus/intussusception 2 Small bowel inflammation 3 Colonic inflammation 7 Diverticulosis 3 Appendicitis 3 Renal cancer 1 Drain malposition 2 Hydrosalpinx 1 Pneumonia 2 Lung metastasis of a carcinoma of unknown primary CUP 1 Ovarian vein thrombosis 1 Ascites/peritoneal dialysis fluid 2 Esophageal hernia 2 Lymphadenopathy 2 Vertebral body fractures 1

$Figure 2, Scan of a 44-year-old patient with abdominal pain. Axial and coronal images show fractures ( arrow ) of thoracic vertebra (T12) and lumbar spine (L3). Although the indication for the study was “abdominal pain,” the history of fall from height was excluded on the request. The fractures were missed by the inexperienced readers on the axial images but easily detected with the coronal images.$

Table 3

Sensitivity and Specificity Values for the Diagnosis of Pathologies

Transverse Scans Alone Combined Transverse and Coronal Scans Reader Sensitivity (%) Specificity(%) AUC Sensitivity (%) Specificity (%) AUC 1 (Radiologist) 94 91 0.947 94 90 0.916 2 (Senior medical student) 93 90 0.927 92 91 0.971 3 (Resident, second year) 91 91 0.964 91 91 0.985 4 (Resident, fourth year) 92 91 0.951 93 91 0.934

There were no significant differences in sensitivity and specificity between transverse scans alone and combined transverse and coronal scans for any reader.

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Reader Agreement

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Table 4

Reader Agreement for the Diagnosis of Abdominal Pathology

Reader Combinations Axial Scans Alone Combined Axial and Coronal Scans Readers 1 and 2 0.80 0.83 Readers 2 and 3 0.73 0.78 Readers 1 and 3 0.70 0.77 Readers 3 and 4 0.72 0.84 Readers 1 and 4 0.76 0.81 Readers 2 and 4 0.74 0.79

Numbers are the mean weighted κ statistics. The differences between image sets were statistically significant ( P = 0.023).

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Table 5

Mean Confidence Scores for the Detection of Abdominal Pathology

Confidence Score Transverse Scans Alone Transverse Plus Coronal Scans R1 R2 R3 R4 Mean R1 R2 R3 R4 Mean 1 0 0 0 0 0 0 1 0 0 0 2 1 1 2 2 2 1 0 4 3 2 3 3 6 12 10 8 3 2 13 10 7 4 29 41 34 56 40 15 33 32 53 33 5 67 52 48 29 49 81 64 48 31 56

Data are given as number of patients. The differences based on the mean of the four readers were significant ( P < 0.001). Post-hoc (Dunn’s) R1 is R3 and R4 ( P < 0.05).

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Added Value of Coronal Images

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Discussion

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Conclusion

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References

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Acute Abdomen

Rationale and Objectives

Materials and Methods

Results

Conclusion

Patients and methods

Imaging Technique

Imaging Evaluation

Statistical Analysis

Results

Image Quality

Abnormalities Detected at CT

Reader Agreement

Added Value of Coronal Images

Discussion

Conclusion

References

Further Reading

Abstracts of Funded National Institutes of Health Grants

Amaurosis Fugax Secondary to Imaging Methods of MRI Scan

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