Implicit screening of abdominal aortic aneurysms among veterans using lumbar spine MRI

BACKGROUND

Early detection of abdominal aortic aneurysms (AAAs) is critical given the high morbidity and mortality of a ruptured aneurysm. Screening ultrasound is recommended for men 65 and 75 years of age with a smoking history. However, studies have shown that the rate of ultrasound screening is low and that implicit AAA screening by abdominal imaging studies that were not originally intended for AAA screening can play a major role in AAA detection.

OBJECTIVE

The main objective was to evaluate the role of lumbar spine MRIs as an implicit AAA screening study by assessing the detection rate of AAAs in a broader cohort of veterans that included screening and non-screening populations.

METHODS

4085 consecutive lumbar spine MRIs from our institution between 2/2020 and 9/2023 were retrospectively reviewed. Each study was labeled AAA present, AAA not present, or indeterminate by radiologists. The correlation between the presence of AAAs and cardiovascular risk factors was assessed using multinomial logistic regression.

RESULTS

AAAs were present in 89 studies (2.2 %) from 80 patients (mean age 75.8 (56-93), M:F 10:0) and absent in 3935 cases (96.3 %) from 3310 patients (mean age 61.7 (19-100), M:F 9:1). Indeterminate cases (n = 61, 1.5 %) were mainly due to incomplete visualization (70.5 %). Mean AAA size was 3.6 cm with most AAAs (n = 43) smaller than 3.5 cm. Sixteen AAAs were 3.5-3.9 cm, 16 between 4 and 4.9cm, and 6 between 5 and 5.9 cm. Artifact precluded measurements in 8 cases. Among the AAA-positive cases, 20 had no prior documentation of AAA. Twenty-one patients with AAAs would not have met the criteria for the routine AAA screening ultrasound. Higher rates of hypertension, hyperlipidemia, and smoking were observed for the AAA cohort at 78.8 % (OR 2.037, CI 1.160-3.576, P = .013), 82.5 % (2.808, 1.543-5.110, P < .001), and 75 % (3.340, 1.979-5.638, P < .001), respectively, compared to the matched no-AAA cohort (58.2 %, 57.6 %, and 50.8 %; n = 2055).

CONCLUSION

Lumbar spine MRI is a valid modality for implicit screening of AAAs.

CLINICAL IMPACT

Those interpreting lumbar spine MRIs should be vigilant about assessing for AAAs, especially in men with a history of hypertension, hyperlipidemia, or tobacco smoking.

Prevalence of Incidental Extraspinal Findings on MR Imaging of the Lumbar Spine in Adults: A Systematic Review and Meta-analysis

BACKGROUND

Low back pain is common worldwide. MR imaging may identify extraspinal findings that are not related to the proposed clinical question. The prevalence of extraspinal incidental findings and their clinical significance has not been well-established.

PURPOSE

This review aimed to evaluate the prevalence of extraspinal findings on MR imaging of the lumbar spine in adults and the prevalence of clinically significant incidental findings.

DATA SOURCES

A systematic search of MEDLINE and EMBASE was performed, including studies published before June 14, 2023.

STUDY SELECTION

Studies presenting a prevalence of extraspinal findings in patients 16 years of age or older were included.

DATA ANALYSIS

A random effects meta-analysis was used to generate composite prevalence measures of extraspinal findings, patients with extraspinal findings, and clinically significant findings.

DATA SYNTHESIS

Sixteen studies were included in this meta-analysis, with a total of 19,593 patients and 6,006 extraspinal incidental findings. The overall prevalence of extraspinal findings was 19.9% (95% CI, 11.1%-30.7%). Overall, 26.7% of patients had an extraspinal finding identified (95% CI, 14.8%-40.6%). The most common subgroup of extraspinal findings was genitourinary findings in males (27.1%; 95% CI, 25.6%-28.8%). Data from 8 studies demonstrated the prevalence of clinically significant findings at 5.4% (95% CI, 3.2%-8.1%).

LIMITATIONS

Retrospective populations with small numbers of participants in clinically relevant subgroups may result in heterogeneity and imprecision within composite outcome measures.

CONCLUSIONS

Extraspinal findings are common, detected in more than one-quarter of patients. Five percent of findings are clinically significant and may require further action.

Ultra-low-dose non-contrast CT and CT angiography can be used interchangeably for assessing maximal abdominal aortic diameter

Background

Routine CT scans may increasingly be used to document normal aortic size and to detect incidental abdominal aortic aneurysms.

Purpose

To determine whether ultra-low-dose non-contrast CT (ULDNC-CT) can be used instead of the gold standard CT angiography (CTA) for assessment of maximal abdominal aortic diameter.

Materials and Methods

This retrospective study included 50 patients who underwent CTA and a normal-dose non-contrast CT for suspected renal artery stenosis. ULDNC-CT datasets were generated from the normal-dose non-contrast CT datasets using a simulation technique. Using the centerline technique, radiology consultants (n = 4) and residents (n = 3) determined maximal abdominal aortic diameter. The limits of agreement with the mean (LOAM) was used to access observer agreement. LOAM represents how much a measurement by a single observer may plausibly deviate from the mean of all observers on the specific subject.

Results

Observers completed 1400 measurements encompassing repeated CTA and ULDNC-CT measurements. The mean diameter was 24.0 and 25.0 mm for CTA and ULDNC-CT, respectively, yielding a significant but minor mean difference of 1.0 mm. The 95% LOAM reproducibility was similar for CTA and ULDNC-CT (2.3 vs 2.3 mm). In addition, the 95% LOAM and mean diameters were similar for CTA and ULDNC-CT when observers were grouped as consultants and residents.

Conclusions

Ultra-low-dose non-contrast CT exhibited similar accuracy and reproducibility of measurements compared with CTA for assessing maximal abdominal aortic diameter supporting that ULDNC-CT can be used interchangeably with CTA in the lower range of aortic sizes.

Appropriateness of Abdominal Aortic Aneurysm Screening With Ultrasound: Potential Cost Savings With Guideline Adherence and Review of Prior Imaging

OBJECTIVE

To assess the appropriateness of abdominal aortic aneurysm (AAA) screening with ultrasound (US) and potential cost savings by adhering to guidelines and reviewing prior imaging.

METHODS

Screening aortic US performed in Nova Scotia from January 1 to April 30, 2019, were reviewed. Patient sex, age, risk factors, and study result (negative, <2.5 cm; ectatic, 2.5-2.9 cm; positive for AAA, ≥3 cm) were recorded. Previous imaging tests were reviewed for the presence/absence of aortic ectasia or aneurysm. Appropriateness was based on the Canadian Task Force on Preventive Health Care (CTFPHC) and the Canadian Society of Vascular Surgery (CSVS) guidelines. The number of potentially averted US, subsequent missed positive findings, and cost savings (over the 4-month period) were calculated according to: 1) each guideline; and 2) each guideline combined with review of imaging done 0 to 5 years and 0 to 10 years previously.

RESULTS

There were 17 (4.6%) of 369 ectatic aortas and 18 (4.9%) of 369 AAAs. The number of potentially averted examinations, missed ectatic aortas, missed AAAs, and cost savings were as follows, respectively: CTFPHC, 222 (60.2%) of 369, 8, 7, and CAD$20 501.70; CSVS, 117 (31.7%) of 369, 4, 2, and CAD$10 804.95. The model that would yield the greatest cost savings and fewest missed positive findings was the combination of CSVS guidelines with review of prior imaging within 5 years; this would avert 189 (51.2%) of 369 examinations, save CAD$17 454.15 over 4 months, and miss only 2 AAAs and 2 ectatic aortas.

CONCLUSION

Over half of aortic US screening tests can be safely averted by adhering to CSVS guidelines and reviewing imaging performed within 5 years.