Lung ultrasonography in the diagnostic work up of pneumonia in stroke patients

Purpose: Pneumonia is a frequent complication in patients with stroke and its early diagnosis is commonly a challenge. Chest X-ray (CXR) has several limitations especially in bedridden patients. Lung ultrasonography (LUS) is a promising technique in the detection of peripheral pneumonic infiltrates and pleural effusions. We performed this study to assess the usefulness of bedside LUS in the diagnostic work up of pneumonia in stroke patients in comparison to CXR.

Patients and methods: We collected data on consecutive ischemic or hemorrhagic stroke patients admitted to Perugia’s Stroke Unit from April 2009 to May 2010, in whom pneumonia was suspected according to clinical and laboratory findings. LUS and CXR were performed within 24 hours from the onset of pulmonary symptoms and within 24 hours from each other. LUS operator and radiologist were blinded to respective results. According to a revised version of the research protocol, after October 2009 CT scan was foreseen in all CXR/LUS discordant cases. Statistical analysis was done to assess concordance (Pearson chi2 test) and symmetry (McNemar test) between LUS and CXR results

Results: Out of the 38 patients studied, 9 were CXR positive. In this group LUS was positive in 8 cases (7 homolateral and 1 contralateral to CXR finding) and negative in 1. In the 1 CXR positive and LUS negative patient, CT scan confirmed LUS result. There were 29 negative CXR patients. In this group LUS was positive in 16 cases, negative in 12 cases and non conclusive in 1 case. Among the 16 CXR negative and LUS positive cases, 6 patients underwent CT scan which confirmed pneumonia

Table 1: LUS/CXR concordance

LUS/CXR concordance	CXR +	CXR -	TOTAL
LUS +	8	16	23
LUS -	1	12	13
LUS non conclusive	0	1	2
TOTAL	9	29	38

Table 2: discordant cases underwent CT scan

Discordant cases	CT +	CT -	TOTAL
15 pts: CXR -/LUS +	6	0	6
1 pts: CXR +/LUS -	0	1	1
TOTAL	6	1	7

Conclusion: LUS has the potential role to detect pneumonic infiltrates and pleural effusion in severe stroke patients with negative CXR and clinical suspicion of pneumonia

In the analyses 1 patient with doubt LUS finding and 1 patient with controlateral LUS finding respect to CXR were excluded. In our study the percentage of CXR/LUS discordant cases is higher than previous finding reported in literature. LUS and CXR were concordant in 13 of 36 cases (36%, Pearson chi2 = 2.485, p = 0.115). Interestingly the number of cases with positive LUS and negative CXR was significantly higher than the number of cases with negative LUS and positive CXR (McNemar P < 0.001). Probably patients' critical conditions (severity of stroke, associated pathologies, poor compliance) that permit only the execution of one plane CXR pictures, reduce sensitivity and specificity of CXR while didn’t impair the performance of a complete bedside LUS. We investigate whether patients with discordant CXR/LUS findings had a more severe stroke (expressed by NIHSS score) by a logistic regression analyses. We found a positive association between CXR/LUS discordance and severity of stroke but without statistically significance perhaps because of the small sample size.The performance of CT scan in some discordant cases suggests that LUS in stroke patients is more sensitive than CXR in detection of peripheral consolidation, according to data collected in other clinical settings. Sensitivity and specificity of LUS could not be calculate because CT scan, the gold standard, was not performed in all cases

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lung ultrasonography - pneumonia - stroke