Rationale and Objectives
Liver lesions incidentally discovered on ultrasound (US) are often further evaluated with magnetic resonance imaging (MRI). The purpose of this study is to evaluate the added effectiveness of contrast-enhanced MRI, compared to noncontrast MRI, to correctly guide management of liver lesions incidentally identified on ultrasound in patients with low pretest probability of malignancy. We conducted the evaluation using a multireader study.
Materials and Methods
Liver MRI studies ordered to evaluate incidental liver US lesions were selected for analysis. Patients with no prior history of cancer or chronic liver disease who had 2 years of clinical follow-up (72 patients) were selected to ensure low pretest probability of malignancy and adequate follow-up to establish proof of diagnosis. Fifty of these studies were randomly selected and analyzed by two abdominal radiologists. In the initial interpretation session, only nonenhanced images were reviewed; after 6 weeks, the complete exam including the contrast enhanced images were viewed. Differences in interpretation between the noncontrast and contrast enhanced reading sessions were assessed.
Results
Sixty-nine patients (95.8%) had no abnormalities, benign masses, or hepatic steatosis accounting for the ultrasound findings. One patient was newly diagnosed with hereditary hemochromatosis, and 2 patients were newly diagnosed with metastatic disease. The most likely diagnosis changed for 15 of the lesions described by reader A, and 16 by reader B. The majority of these changes (26/31 lesions, 84%) were from one benign entity to another. Five of 31 (16%) of the changes involved that of a benign entity to a malignant one. Reader A recommended additional contrast enhanced imaging in 13/50 (26%) patients; reader B, 9/50 (18%) patients. After viewing the nonenhanced images, both readers recommended that all patients with eventual malignancies return for contrast administration and/or biopsy. After viewing the contrast-enhanced imaging, both readers accurately diagnosed all malignancies. Patient-based analysis receiver operating characteristic curves demonstrated no significant difference between the enhanced and noncontrast limbs of the study, and no significant difference between readers.
Conclusion
Most of the changes in lesion detection and characterization made after contrast administration were clinically insignificant. In the lesions in which clinically important differences were made, both radiologists recommended additional imaging or biopsy that would have eventually led to the correct diagnosis. None of the patients with malignancy was categorized as completely benign either on noncontrast or contrast-enhanced imaging. This supports the utility of initially performing a noncontrast examination in a population with a low pretest probability of malignancy, especially those in whom gadolinium administration is contraindicated.
Significant technologic strides made in the past few decades have led to the development of highly sensitive imaging modalities. This has led to improved noninvasive characterization of abnormalities, more accurate delineation of local and distant spread of tumor, and better preoperative planning. These advances have come at added health care and individual costs. Notably, radiologists are increasingly detecting abnormalities unrelated to the patient’s primary complaint that precipitated the initial imaging . In the literature, these findings are often labeled “incidentalomas” because they are discovered incidentally and are often of little to no clinical significance. Incidentalomas create a significant increase in downstream additional work-up, financial cost, medical provider time allocation, patient inconvenience, and create management dilemmas . They often prompt the use of more advanced imaging or invasive procedures.
Although liver masses can be evaluated with multiphase contrast-enhanced computed tomography (CT), gadolinium-enhanced magnetic resonance imaging (MRI) has become the gold standard of noninvasive diagnosis , particularly in the era of heightened concern for radiation. However, gadolinium administration has its own set of drawbacks including its cost, the time necessary to obtain intravenous access, patient discomfort, and adverse reactions to administration.
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Materials and methods
Subjects
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Procedure
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Case Selection
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Table 1
Original Magnetic Resonance Imaging Interpretation Results
Characterization of Abnormality Number of Patients or Lesions Benign/incidental 69/72 (95.8% of patients) Normal: no abnormalities 6 (8.3% of patients) Hepatic steatosis 12 (16.7% of patients) Benign masses 51 (70.8% of patients) Hepatic adenoma 1% of benign masses Adrenal cyst 1% of benign masses Hemangioma 64% of benign masses Hepatic cysts 23% of benign masses FNH 11% of benign masses Clinically significant 3/72 (4.2% of patients) Metastatic disease 2 (2.8% of patients) Severe iron deposition (hemochromatosis) 1 (1.4% of patients)
FNH, focal nodular hyperplasia.
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Reader Analysis
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Statistical Analysis
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Results
Patient Population
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Reader Study
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Table 2
Individual Reader Analysis of Lesions Detected from Review of 50 Selected Liver MRIs with and without Gadolinium Contrast
Reader A Reader B Without Contrast With Contrast Without Contrast With Contrast Normal: no abnormalities 5 6 5 6 No masses; hepatic steatosis 9 9 7 8 Metastatic disease 6 7 3 7 Iron deposition 1 0 1 1 Adrenal cyst 1 1 1 1 Hemangioma 26 33 41 43 Simple cyst 27 19 17 32 Complicated cyst 4 1 8 3 Focal nodular hyperplasia 0 1 3 2 AVM 1 0 0 0
AVM, arteriovenous malformation.
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Table 3
Individual Reader Patient Characterization of 50 Selected Liver MRIs with and without Gadolinium
Total Number of Patients with: Reader A Reader B Without Contrast With Contrast Without Contrast With Contrast Benign/incidental findings 34 48 39 47 Indeterminate findings 13 0 9 0 Clinically significant findings 3 2 2 3 Called back for contrast administration 13 n/a 9 n/a Biopsies recommended 4 2 1 2
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Table 4
Specific Individual Reader Changes Noncontrast MRI versus Contrast Enhanced
Reader A Reader B Findings described on noncontrast study but not on the contrast-enhanced study 1 AVM
5 simple cysts
2 hemangiomas None Findings described on the contrast-enhanced study but not on the noncontrast study 2 simple cysts
1 hemangioma
1 FNH 9 simple cysts
4 hemangiomas
2 FNH Change in most likely diagnosis from the noncontrast round to the enhanced round: Total number changed 15 (26.3%) lesions 16 (21.9%) lesions Simple cyst to hemangioma 9 2 Hemangioma to simple cyst 2 5 Hemangioma to metastasis 1 1 Complicated cyst to hemangioma 2 2 Complicated to simple cyst 1 3 FNH to metastasis 0 3
AVM, arteriovenous malformation; FNH, focal nodular hyperplasia.
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Discussion
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