The evaluation of the intracavitary effusions by a bedside ultrasound examination

Abstract

OBJECTIVE:

This study aims to evaluate the bedside use of the pocket-sized ultrasound (US) device for the detection of the intracavitary effusions.

METHODS:

We randomly enrolled 40 patients admitted to S. Andrea Hospital of Rome. Every patient received a clinical and biochemical evaluation and a bedside US examination to detect and estimate the intracavitary (pleural, pericardial and intra-abdominal) effusions; the US measurements have been compared to the computed tomography (CT) scans (as gold standard).

RESULTS:

The patients presented a high prevalence of effusions: right pleural 16/40 = 40% (esteemed volume 236.3±500.7 ml, mean±standard deviation m±SD), left pleural 8/40 = 20% (127.0±377.4 ml), pericardial 12/40 = 30% (47.5±72.8 ml) and intra-abdominal effusions 5/40 = 12.5% of cases (110.9±600.6 ml). Linear regression analysis showed a significant correlation between US and CT measurements: pleural r = 0.973 p < 1×10^–38, pericardial r = 0.927 p < 1×10^–39, intra-abdominal space r = 0.921 p < 1×10^–59. The accuracy of the bedside US at the pleural, pericardial and abdominal level was respectively 98%, 93% and 96% (Cohen’s kappa coefficient 0.966, 0.841 and 0.833).

CONCLUSIONS:

The present study showed a high prevalence of the intracavitary effusions and a high accuracy of the bedside US. The bedside US by a pocket-sized device is promising tool for its advantages of reproducibility and non-invasiveness of the device.

Keywords

Bedside ultrasound intracavitary effusions comorbidity computed tomography

1 Introduction

The availability of pocket-size ultrasound (US) devices recently increased, allowing physicians to evaluate their patients at a beside point-of-care ultrasound (POCUS), as an extension of the traditional physical examination, improving prompt medical decision making in the acute settings [1, 2].

Moreover, the complexity of the patients admitted to an Internal Medicine ward is characterized by a significant comorbidity (two or more coexisting diseases) and polypharmacy (five or more drugs), respectively with a mean of 7 diseases and 8 drugs [3, 4].

As described in different studies, ultrasonography has high levels of sensitivity and specificity with respect to CT (computed tomography) for the detection of pleural (range 92–100% and 93–100%), pericardial (range 87–94% and 92–96%) and intra-abdominal (range 73–76% and 97–98%) effusions [5, 6]. Color-coded duplex sonography is accurate in diagnosing location, wall thickness, and inflammatory findings of the examined structures [7, 8]. The lung US examination supports the clinicians in the evaluation of the pulmonary inflammatory changes (thickening of the pleural line and/or the presence of A/B lines in the subpleural regions), especially in patients with COVID-19 infection, as recently described [9].

The aim of this study is to evaluate the presence of the intracavitary effusions at the bedside of the inpatients of the Emergency Medicine Unit and Internal Medicine Unit of S.Andrea Hospital, by the means of a pocket-sized US device, in comparison with the standard radiological (X-ray and CT scan) imaging.

2 Materials and methods

We randomly enrolled n = 40 patients of the Emergency Medicine Unit and Internal Medicine Unit of S. Andrea Hospital of Rome (n.34 males and n.6 females, mean age±standard deviation = 80.0±10.2 years).

Each patient received an evaluation of: (1) the clinical history with the measurements of anthropometric (body weight, height, body mass index or BMI) and hemodynamic parameters (systolic and diastolic blood pressure, SBP and DBP, and heart rate, HR); (2) the cardiometabolic and inflammatory panel, including the measurement of blood glucose (mg/dl), total cholesterol (mg/dl), high-density lipoprotein (HDL) (mg/dl), triglycerides (TG) (mg/dl), creatinine (mg/dl) (with the esteemed glomerular filtration rate, GFR, ml/min, by the CDK-EPI equation), albumin (%), C-reactive protein (CRP) (mg/dl), procalcitonin (PCT) (ng/ml), brain natriuretic peptide (BNP) (pg/ml); (3) the intracavitary effusions, through a bedside US examination by a VSCAN Extend™ (a pocket dual probe with 1.7–3.8 MHz phased array and 3.3–8.0 MHz linear array transducer, respectively for deep and superficial scanning; a color imaging option to add color coded qualitative information concerning the relative velocity and direction of fluid motion within the black and white image; an optional connection to PACS/DICOM server for patient and image archiving/retrieval) (Esaote MyLabOmega was available); (4) a standard radiological examination by thoracic X-ray, that was followed by a thoracic and abdominal CT scan (with 3D multiplanar transverse-coronal-sagittal reconstructions, MPR, by Digital Imaging and COmmunications in Medicine, DICOM, standard) on the basis of their clinical features (with imaging obtained at the end of inspiration).

Volume effusions were measured using the following methods (Fig. 1). For the pericardial effusions, the volume of a prolate ellipse of the pericardial sac and heart (π x 4/3 x L/2 x D1/2 x D2/2, where L is the major and D1/D2 the minor axes (L = maximal long axis dimension and D1 = maximal transverse dimension in the apical four chamber view, D2 = maximal anteroposterior dimension in the parasternal short axis view at the mitral leaflet level), in centimeters (cm) have been calculated, and the pericardial effusion volume (ml) = volume of the pericardial sac - volume the of heart [10]; in the US evaluation, the L and D1 axes were measured in the four chamber view and the D2 axis in the parasternal short view, and they were compared with corresponding axis in the transverse and sagittal CT sections. For the peritoneal effusions, the average thickness of ascites (cm) in five areas (the bilateral subphrenic space A and B, the bilateral paracolic space C and D and the pre-bladder space E) was multiplied by the area of standard abdominal cavity (assumed to be 1000 cm²), volume of ascites (ml) = (A + B + C + D + E)×200 [11]; in the US evaluation, the A, B, C and D spaces were obtained in the transverse plane and the E space in the sagittal plane, and they were compared with corresponding spaces in the transverse CT sections. For the pleural effusions by US, the maximum distance between diaphragm and visceral pleural layer at the end of expiration with the patients in sitting position (D), pleural effusion volume (ml) = 16×D (mm) [12]; in the US evaluation, the distances were obtained in the sagittal planes, and they were compared to the largest depths measured between the visceral and parietal pleura on the transverse and sagittal CT sections.

Fig. 1

Probe positions (A supine, B left lateral, C sitting patient) for effusion evaluation by bedside POCUS with VSCAN Extend. Examples of US scans: D right paracolic, E four chamber, F right pleural view.

A fluid volume above 50 ml was considered as pathological.

The study was approved by the local ethical committee (RIF. CE 6583_2021) and all the patients gave their informed consent.

Statistical analysis was performed by the means of the one-way analysis of variance (to evaluate the differences between the means), Pearson’s chi-square test (to evaluate the associations between two variables), the linear regression analysis (to evaluate the correlations between the parameters) and Cohen’s coefficient calculation (to evaluate the possibility of the agreement occurring by chance).

A p-value < 0.05 was considered as significant.

3 Results

The clinical features of the patients are described in the Table 1.

Table 1
The clinical features of the patients (mean±SD) (n = 40)

Age (years) 80.0±10.2

Females 15%

CIRS-SI 2.6±0.7

CIRS-CI 7.0±2.5

Number of drugs 8.0±2.7

BMI 25.1±3.9

SBP (mm Hg) 123.4±14.5

DBP (mm Hg) 72.0±9.3

HR (bpm) 72.1±10.7

QTc (msec) 454.1±45.1

GFR by CKD-EPI (ml/min) 73.9±23.7

Albumin (%) 49.0±7.4

Hb (g/dl) 11.6±2.0

Blood glucose (mg/dl) 106.7±38.4

Procalcitonin (ng/ml) 0.9±3.6

Brain Natriuretic Peptide (pg/ml) 286.2±719.9

C-Reactive Protein (mg/dl) 5.5±5.6

Age (years)	80.0±10.2
Females	15%
CIRS-SI	2.6±0.7
CIRS-CI	7.0±2.5
Number of drugs	8.0±2.7
BMI	25.1±3.9
SBP (mm Hg)	123.4±14.5
DBP (mm Hg)	72.0±9.3
HR (bpm)	72.1±10.7
QTc (msec)	454.1±45.1
GFR by CKD-EPI (ml/min)	73.9±23.7
Albumin (%)	49.0±7.4
Hb (g/dl)	11.6±2.0
Blood glucose (mg/dl)	106.7±38.4
Procalcitonin (ng/ml)	0.9±3.6
Brain Natriuretic Peptide (pg/ml)	286.2±719.9
C-Reactive Protein (mg/dl)	5.5±5.6

CIRS = Cumulative Illness Rating Scale, SI and CI = Severity Index and Comorbidity Index.

The POCUS examination by VSCAN Extend revealed sixteen right pleural effusions (16/40 = 40% of cases, with mean±standard deviation, m±SD, volume of 236.3±500.7 ml), eight left pleural effusions (8/40 = 20%, with volume of 127.0±377.4 ml), twelve pericardial effusions (12/40 = 30%, with volume of 47.5±72.8 ml) and five intra-abdominal effusions (5/40 = 12.5%, with volume of 110.9±600.6 ml).

The largest pleural effusion depths on the MPR CT sagittal planes were significantly related to the largest heights on the MPR CT transverse planes (r = 0.976 p < 1×10^–39) (data not shown).

The measurements by US showed a mean parietal to visceral distance of, respectively: A) for the pericardial axes, the differences (Δ) between the L, D1 and D2 measurements of pericardium and heart were 2.4±4.5, 1.4±2.6 and 2.4±4.1 mm (versus 1.8±3.2, 1.3±2.3 and 1.7±3.0 mm in the MPR CT sagittal and transverse planes); B) for the right and left subphrenic, right and left paracolic and the pre-bladder space, the measurements were 0.8±3.3, 0.6±2.1, 1.0±6.3, 1.5±9.5 and 1.9±9.5 mm (vs 0.8±4.1, 0.5±1.6, 1.7±9.1, 1.1±5.0 and 1.5±7.6 mm in the transverse CT scans); C) for right and left pleural space, the distances were 15.4±30.6 and 8.0±23.6 mm (vs 16.4±27.4 and 10.7±27.4 mm in the transverse CT scans) (not significant differences between US and CT measures) (Fig. 2).

Fig. 2

The measurements of the parietal to visceral distance for the pericardial axes (difference, Δ in cm, in the L, D1 and D2 axis), for the intra-abdominal cavity (right and left subphrenic, right and left paracolic and pre-bladder space, in cm) and for the pleural spaces (right and left pleural space, in mm) (mean±standard deviation, US with VSCAN Extend versus CT scan).

Despite the potential bias due to the methods (for example, the imaging was obtained in different moments of the respiration), linear regression analysis showed a significant correlation between US and CT effusion measurements, respectively: pleural r = 0.973 p < 1×10^–38, pericardial r = 0.927 p < 1×10^–39, intra-abdominal effusion r = 0.921 p < 1×10^–59 (Figs. 3 –5).

Fig. 3

The correlation between the US (VSCAN Extend) and CT pleural effusions (mm).

Fig. 4

The correlation between the US and CT pericardial effusions (Δ cm).

Fig. 5

The correlation between the US and CT intra-abdominal effusions (cm).

The endocavitary effusions were significantly related to the main biochemical parameters (GFR, CRP, PCT, BNP and albumin) (data not shown). The measurements of the inferior vena cava diameter by US and CT scans were significantly related (p < 1×10^–6) (data not shown).

4 Discussion and conclusions

The present study showed that the bedside POCUS by a pocket-sized device is a fast and accurate support in the diagnostic process, particularly in the acute setting, without the need to move the patient out of the ward. We found a high percentage of intracavitary effusions, with a mean of 30% (ranging from 12.5 to 40% of cases, depending on the sites of evaluation).

The sensitivity, specificity and accuracy of the bedside US (with a cut-off liquid amount of 50 ml) were respectively 96%, 100% and 98% at the pleural level (agreement 0.984, Cohen’s kappa coefficient 0.966), 89% 95% and 93% at the pericardial level (agreement 0.933, Cohen’s kappa coefficient 0.841), 100%, 95% and 96% at the intra-abdominal level (agreement 0.958, Cohen’s kappa coefficient 0.833), in line to what previously reported in the literature [5, 6]. By using a hand-carried ultrasound device, Schleder S et al. showed a sensitivity and specificity of 91% and 100% for pleural effusion in intensive care patients, a sensitivity and specificity of 75% and 100% for free intra-abdominal fluid in major trauma patients with organ lacerations [13, 14].

Regarding the detection of pleural effusions, the standard investigation (chest X-ray) showed a low sensitivity (35%) and specificity (90%). Since CT scans may be difficult to perform in short time, the bedside US is a promising tool for use on a daily basis, especially in the management of critically ill patients [15 –21].

Further studies are necessary for the interesting evaluation of the impact of the effusions on the microcirculation. The issue has been extensively studied in the lung where pleural and interstitial fluid volumes are strictly controlled [22]. in this case, the POCUS examination may be useful to detect the fluid accumulation, at the same time, at both the pleural cavity and the alveolar space.

In conclusion, the bedside US appears advantageous for its reproducibility and non-invasiveness, and it is a promising tool in order to improve the diagnosis, treatment and follow-up of the intracavitary effusions, that are frequently present in the Internal Medicine Departments.

Conflicts of interest

The authors have no potential conflicts of interest to report.

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