Primary and minor indications to bedside renal ultrasonography

Abstract

We appreciated the letter ‘‘Bedside renal ultrasonography: other utilities than hydronephrosis’’ by Chia-Ter Chao [1]. The author described the ultrasonographic (US) findings of acute pyelonephritis (APN), analysed the diagnostic accuracy of various imaging modalities in this disease, and emphasized the role of bedside US in APN. On the basis of these considerations, Chao commented on the fact that in our paper titled ‘‘Clinical applications of bedside ultrasonography in Internal and Emergency Medicine’’ [2] we considered obstructive uropathy and acute urine retention as the primary indications for bedside US in urinary tract diseases and mention, as other indications, hematuria, acute renal failure, suspected abscesses of the kidneys, and gross prostate abnormalities without including APN. We comprehend the enthusiasm of Chao for the application of US in APN that confirms the knowledge and the experience of the author in this field but completely disagree with him when he attributes the same role and similar importance of bedside US to APN versus hydronephrosis, renal stone or other obstructive uropathy. We think that between APN and the latter pathologies, there are very important differences not only for the diagnostic accuracy and the role of US, especially if performed bedside, but also for the epidemiologic occurrence in both Internal Medicine and Emergency Departments. First of all, we have to keep in mind what bedside US is. This is a rapid and simple US method for the diagnostic evaluation of emergency medical conditions in the acutely ill, critically ill or injured patient, performed bedside with small portable instruments often capable of only fundamental imaging [3]. This technique can also be executed by clinicians with a limited experience in US, equipped with only a second level of experience, according to EFSUMB learning guidelines [1]. With respect to the sonographic findings of acute pyelonephritis mentioned by Chao, we have no comment because they are well known and reported in the literature, but they do not have a high specificity, since the disease produces hypoechoic as well as hyperechoic areas. Colour and power Doppler US produces a small increase in the sensitivity of US, but mainly in the case of abscesses. Similarly angiosonography (CEUS) can be usefully employed only in the presence of renal abscesses but not in APN without complications. In fact, EFSUMB guidelines report indications for CEUS only in case of focal renal tumours, trauma, or abscesses, and not in APN [4]. Finally we have to consider that Colour and Power Doppler US, and especially CEUS, are certainly not methods used as bedside US. Moreover, a recent review on the state of the art of imaging of renal infections confirms that US is especially effective in the diagnosis of hydronephrosis or pyonephrosis, is less sensitive than computed tomography (CT) in evaluating for complications, has major limits in operator dependency and in obese patients, and remains a main stay in differentiating cystic versus solid structures [5]. The same conclusions have been reported in another important review on radiologic and pathologic aspects of pyelonephritis: diagnosis is typically based on clinical features and laboratory tests; imaging is reserved for nonresponders or patients with a typical clinical presentation. Computed tomography, over conventional radiography and US, is the preferred method for evaluating APN and emphysematous pyelonephritis. US is useful but CT A. Vincenzo C. Valeria (&) Department of Internal Medicine, Maggiore Hospital, Largo B. Nigrisoli 2, 40133 Bologna, Italy e-mail: v.camaggi@ausl.bologna.it