The implication of these methodologic problems is that the frequencies of reflux and scarring may be significantly higher than the 42.5% and 25.9% reported by the authors. Ben-Ami et al have stimulated interest that we hope will result in the formulation of an effective management protocol for dealing with a treatable problem that is more common than is generally recognized. References 1. Ben-Ami T, Sinai L, Hertz M, Boichis H. Vesicoureteral reflux in boys: review of 196 cases. Radiology 1989; 173:681-684. 2. Ogra PL, Faden HS. Urinary tract infection in childhood: an update. J Pediatr 1985; 106:1023-1029. 3. Hellerstein S. Recurrent urinary tract infection in children. Pediatr Infect Dis 1982; 1:271-281. 4. Stoller ML, Kogan BA. Sensitivity of 99mTc-dimercaptosuccinic acid for the diagnosis of chronic pyelonephritis: clinical and theoretical considerations. J Urol 1986; 135:977-980. 5. Verber IG, Strudley MR, Meller ST. 99mTc-dimercaptosuccinic acid scan as first investigation of urinary tract infection. Arch Dis Child 1988; 63:1320-1325.

Dr Ben-Ami responds: We are grateful to Dr Schoeneman and his colleagues for their interest in our article and for providing an opportunity to highlight our message. The essence of their letter is the apparent lack of diagnostic criteria for UT!, the poor sensitivity of intravenous urography in the diagnosis of renal infection and scars, and the value of nuclear medicine in their diagnosis. Our report on VUR in boys reflects our 9-year experience (1974-1983), during which many concepts and conventional wisdom changed considerably. Most of our data were collected in the 1970s, when voiding cystourethrography and intravenous urography were still considered to be the state of the art in the workup of children with UT!. Obviously, we no longer image the urinary tracts of such children in the same way. Sonography has replaced intravenous urography in young children with mild or no VUR. Radionuclide studies performed with the use of tubular agents (Tc-99m glucoheptonate and Tc-99m dimercaptosuccinic acid) are now widely utilized and are clearly superior to intravenous urography and sonography in the diagnosis of renal parenchymal infection (1). We did not intend to address the subject of UTI in boys; therefore, we did not elaborate on diagnostic criteria in our article. All the boys in our patient population had been circumcised. The diagnosis of UTI depended entirely on multiple samples obtained by clean catch, catheterization, or suprapubic aspiration with pure growth of 105 bacterial colonies per milliliter. However, the purpose of our report was not to discuss current concepts in imaging of children with UTI. These have been eloquently discussed by others (2), and we have addressed this issue elsewhere (3). Rather, we wished to discuss the frequency of VUR in boys in various settings, not only in boys with UTI, and to show that it is common. We also demonstrated the association of VUR in boys with upper urinary tract anomalies, UTI, and high-grade bladder output obstruction. Boys with VUR are a more varied group than girls with VUR, reflecting the wider range of pathologic findings at voiding cystourethrography in the male. Urethral stricture, meatal stenosis, hypospadias, posterior urethral valves, and anterior urethral diverticulum are some of the more common abnormalities. The relationship between urethral abnormalities in the male and reflux was the subject of previous contrasting reports. Some claim that low-grade obstruction is associated with increased risk for VUR (4), and others believe that even high-grade urethral obstruction, such as that due to posterior urethral valves, is not associated with increased risk for reflux, except when paraureteral diverticula are present (5). We thought that our group was large and varied enough to contribute to the understanding of these issues. We concluded that VUR is mostly a primary, genetically determined phenomenon, with clear associations with congenital anomalies of the upper urinary tracts. However, it is affected by and is associated with mechanical factors, such as high-grade blad-

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der outlet obstruction, but not with low-grade urethral obstruction. It also plays an important part in the multifactorial picture of UTI and renal scarring. We admit that the incidence of renal scarring in boys with UTI and VUR might have been underestimated in our report. Other points made in reference to renal parenchymal scarring are all valid but do not challenge the points we tried to address in our article. References 1. Verber IG, Strudley MR, Miller ST. 99mTc dimercaptosuccinic acid (DMSA) scan as first investigation of urinary tract infection. Arch Dis Child 1988; 63:1320-1325. 2. Lebowitz RL, Mandel J. Urinary tract infection in children: putting radiology in its place. Radiology 1987; 165:1-9. 3. Ben-Ami T, Rozin M, Hertz M. Imaging of children with urinary tract infection: a tailored approach. Clin Radiol 1989; 40:64-67. 4. Shafir R, Hertz M, Boichis H, Tsur H, Aladzen M, Jonas P. Vesicoureteral reflux in boys with hypospadias. Urology 1982; 20:2932. 5. Nancarrow PA, Lebowitz RL. Primary vesicoureteral reflux in blacks with posterior urethral valves: does it occur? Pediatr Radiol 1988; 19:31-35.

Tamar Ben-Ami, MD Department of Radiology, University of Chicago 5841 South Maryland Avenue, Box 429, Chicago, IL 60637

* US Guidance of Interventional Procedures From: Eugene Y. Yeung, MB, FRCP(C), Wendy Thurston, MD, FRCP(C), Mark J. Quigley, MD, FRCP(C), and Chia-Sing Ho, MB, FRCP(C) Department of Radiology, Toronto General Hospital 200 Elizabeth Street, Toronto, Ontario M5G 2C4, Canada Editor: We commend Drs Matalon and Silver on their excellent article on the use of real-time ultrasonography (US) in interventional procedures (1), which appeared in the January 1990 issue of Radiology. In our interventional service we employ US guidance in a significant proportion of our procedures for the initiation of drainages and biopsies. We wish to make several comments on techniques that have been advantageous in our hands and may be helpful to others: 1. We have found it much easier to place the needle in the target organ if the target is placed in the center of the US image. In other words, the vertical axis of the transducer should point directly to the target and thus serve as a guide for needle placement. While we agree that the needle shaft can be best seen when the incident beam is perpendicular to it, deviation of the needle in the path may be more difficult to detect, especially for deep structures. We prefer to scan as close to the needle entry point as possible. With use of this technique, small alterations in scanning angle are easily made both to study the needle path and to maximize needle visualization. In this way, the axes of the US transducer and the exposed needle shaft provide a strong visual aid for accurate needle placement. 2. Our technique requires that the transducer be sterile. This is easily achieved by placing a small amount of scanning gel on the sticky side of a 30 X 28-cm sheet of Opsite dressing (Smith and Nephew Medical, Hull, England), which is then wrapped around the transducer. A sterile towel is used to wrap the probe cable. This system is much less cumbersome to use than scanning through a sterile glove. Furthermore, the orientation and axis of the transducer are easily visualized through the dressing, an important point in the establishment of the needle-operator-machine feedback loop (dynamic interaction), which is so necessary for quick and accurate needle placement. 3. We have found US guidance especially useful in the relief of biliary and urinary tract obstructions. We routinely use this technique to perform nephrostomies in hydronephrotic kidneys. An appropriate posterior calyx is easily identified

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US guidance of interventional procedures.

The implication of these methodologic problems is that the frequencies of reflux and scarring may be significantly higher than the 42.5% and 25.9% rep...
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