REVIE\N ARTICLE Standardised ultrasound technique for evaluation of urinary tract infection in South African children highlighting the capabi Iities and pitfalls of this modality Savvas Andronikou MB BCh, FCRad(D), FRCR (Land) Ebrahim Kader MBChB ject with divergent imaging protocols existing in the current literature. As ultrasound (US) is a cheap, non-inva- sive, non-ionizing procedure, it is almost universally accepted as the ini- tial investigation of choice in children with UTI. US reliably demonstrates many important features of the uri- nary system, including renal size, con- genital abnormalities, calculi and, in particular, obstruction to flow of urine (pelvicalyceal dilation). Due to the subjective, user-dependent nature of US, we suggest the adoption of a standardised scanning approach to improve diagnostic accuracy and reproducibility, thereby facilitating patient follow-up. We also hope that standardisation will limit the misin- Chris Weiman MBChB Department of Paediatric Radiology, University of Cape Town and Institute of Child Health, Red Cross War Memorial Children's Hospital, Cape Town Abstract Urinary tract infection (UTI) is one of the commonest bacterial infections in childhood and has potentially disas- trous consequences. The imaging of UTI in children is a controversial sub- 35 SA JOURNAL OF RADIOLOGY • October 2001 terpretation of US findings that are not evidence-based. This is a pictorial review of the standardised US tech- nique used in the investigation of UTI in children at the Red Cross War Memorial Children's Hospital. Introduction Urinary tract infection (UTI) is considered the most common inva- sive bacterial infection in childhood and may result in permanent renal damage, especially hypertension and chronic renal failure, prompting the routine investigation of these children in order to identify those at risk."?The investigation of UTI in childhood is a controversial topic in current litera- ture with little consensus as to the ideal investigation protocol." How- ever, the availability, low cost and absence of significant biological side- effects of ultrasound (US) have made it the most popular initial investiga- tion of UTI in childhood." US ele- gantly demonstrates many features of the urinary tract including renal size, congenital abnormalities, calculi and, in particular, obstruction to flow (pelvicalyceal dilation), a treatable though relatively rare cause of UTP4 As is well recognised, the diagnostic accuracy and reproducibility of US findings are user-dependent," Stand- ardisation of US technique not only improves its diagnostic power, but also facilitates easy and reliable patient follow-up. In addition, it highlights the limitations of US and discourages over-zealous comment on these parameters.' This pictorial summary of the standardised US teclmique at the Red Cross War Memorial Children's Hospital (RXH) also high- lights a few abnormalities demon- strated by this modality. REVIEW ARTICLE Fig. te. The bladder should always be studied first in order to image it when distended. The transverse view is important to assess for possible nyato- ureter. The bladder is demonstrated in the axial plane and its transverse diameter measured. Vesical wall thickness is measured on the lateral wall in this view. There is good through·transmis· sion and visualisation of structures posterior to the bladder. Fig. 1b. Abnormal, bilaterally dilated ureters. This appearance, especially if unilateral, may be mun- Icked by a transient ureteric peristaltic wave. Capabilities and limitations of US US is complementary to radionu- elide scanning and radiographic imaging in the investigation of UTI in children.' While it cheaply, effectively and safely provides information regarding many facets of the urinary tract, cognizance should be taken of its limitations.' The principal benefits of US lie in Fig. ze. The bladder is shown in the sagittal plane. Assess for sediment and calculi. Fig. 2b. ParasagIttal image of the patient shown in Fig. 1b (above) confirms the persistent ureteric dilatation. its ability to elucidate: (i) the presence of two kidneys in their correct posi- tion; (ii) renal sizes - small kidneys in chronic renal failure, large kidneys - e.g. duplex kidneys and multicystic dysplastic kidneys; (iii) congenital abnormalities - horseshoe or duplex kidneys; (iv) hydronephrosis and/or hydro-ureter - suggests obstruction; (v) calculi; and (vi) post-micturition vesical residual volume (Figs 1 - 9).2,4.6 US cannot provide reliable assess- ment of: (i) vesico-ureteric reflux; (il) renal scars; (iiI) current renal infec- tion; and (iv) renal function.':" Standardisation (Figs 1 - 9) While many operators are com- 36 SA JOURNAL OF RADIOLOGY • October 2001 Fig. 3a. Right parasagIttal plane - this image shows the kidney inferior to the liver and al/ows comparison of their echogenicities. Normal echogenicity of the liver is greater than that of the spleen and in turn, the spleen is more echogenic than the kidneys. The neonatal kidney is an excep- tion (see Fig. 6a below). Fig. 3b. This kidney is hyperechoic relative to the liver and is abnormal. fortable with a free-scanning US tech- nique, the standardisation of US tech- nique involves adherence to a definite sequence. The ultrasonographer/ ultrasonologist, in the course of the examination, aims to measure preset parameters in predetermined views or planes. This improves diagnostic accuracy, allows for reproducibility and encourages a comprehensive examination," The aim is to record data pertinent to the investigation of UTI objectively, while limiting com- ment on parameters that are inade- quately assessed on US. A pro forma data sheet for recording the scan results reinforces the standardised REVIEW ARTICLE Fig. 4a. Right coronal/sagittal plane - renal length is recorded as the greatest cephalo-caudal dimen- sion. Comparison is made with standardised centile charts of renal size versus age. Fig. Sa. Axial plane - the renal pelvis should be measured in the AP axis at the position indicated (x • x) This is the most reliable measurement In the assessment of hydronephrosis and the most repro- ducible Indicator of serial change especially in pelvi-ureteric junction (PW) obstruction follow-up. Fig. 6a. Left parasagittal plane - this image demonstrates the left kidney in relation to the spleen and permits comparison of their echogenicities. The kidney should be less echogenie than the spleen. The neonatal kidney may have a normally echogenie cortex. Note the prominence of the rela- tively hypo-echoic medullary pyramids; this appear- ance must not be misinterpreted as hydronephrosis. In hydronephrosis, connection can be demonstrated between the dilated calyces. Fig. 4b. A duplex kidney is usually larger than nor- mal and may show an obstructed upper pole with a shrunken lower pole. Fig. Sb. Increased AP renal pelvis measurement. A measurement of < 10 mm is normal and> 20 mm is abnormal. A value between 10 and 20 mm repre- sents an equivocal finding. Fig. 6b. Echogenie infantile polycystic kidney dis- ease. 37 SA JOURNAL OF RADIOLOGY • October 2001 Fig. 7a. Left coronal/sagittal plane - the length of the left kidney is measured on this image (compare with Fig. 4a above). Fig. 7b. Hydronephrotic left kidney. Fig. Ba. Axial plane - as on the right, the pelvis of the left kidney Is measured in the AP axis. Fig. Bb. An extrarenal pelvis is a normal variant and Is measured at the position Indicated (+ • f). REVIE\N ARTICLE Fig. Ba. The petlent is allowed to micturate and any post·micturltlon residual volume is measured. This is not a reliable assessment in neonates as they do not void completely. Fig. Bb. Enlarged, trabeculated bladder with a sig· nificant residual volume and visibly di/ated ureters posterior to it. Table I. An example of a standard data sheet that can be used to encourage unifor- mity of reporting of ultrasound studies between various operators and allow long- term follow-up Urinary tract ultrasound assessment pro forma data sheet Patient name . Folder number Age .. Renal size - 50th centile for age (from standardised charts) .. Right Kidney Left Kidney Length (mm) Echogenicity Pelvicalyceal system Normal Hydronephrosis (Mild/moderate/severe) AP pelvis measurement Ureter seen? Other (e.g. calculus, renal anomaly) Bladder: Wall thickness Post micturition measurement and volume Dilated ureters posterior to the bladder: Other: Comment: approach. An example of a standard- ised data sheet is shown in Table I. Conclusion A standardised examination is essential to detect relevant pathologi- cal states related to UTI consistently, and to enhance reproducibility for long-term patient follow-up. It pro- motes objective data recording on uri- nary parameters pertinent to the investigation of UTI, which are reli- ably demonstrated on US, and limits over-zealous comment on findings attributed to US that are not evidence- based. References 1. Larcombe J. Urinary tract infection in children. BMJI999;319: 1173·1175. 2. Craig J. Urinary tract infection in children: investigation and management. Modern Medicine of South Africa 1998;Nov: 14·25. 3. Sreenarasimhaiah V, Alon US. Uroradiologic evaluation of children with urinary tract infec- tion: are both ultrasonography and renal corti- cal scintigraphy necessary? J Pediatr 1995; 127: 373·377. 4. Smellie JM, Rigden SPA, Prescod NP. Urinary tract infection: a comparison of four methods of investigation. Arch Dis Child 1995; 72: 247· 250. 5. Fidler K, Hyer W. A Strategy for UTI in chilo dren. Practitioner 1998; 242: 538·541. 6. Smellie JM, Rigden SPA. Pitfalls in the investi- gation of children with urinary tract infection. Arch Dis Child 1995; 72: 251·258. 38 SAJOURNALOF RADIOLOGY. October 2001