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Saudi Journal of Kidney Diseases and Transplantation
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ORIGINAL ARTICLE Table of Contents   
Year : 2009  |  Volume : 20  |  Issue : 5  |  Page : 816-821
Renal duplex doppler ultrasonography in patients with recurrent urinary tract infection

1 Department of Pediatrics, Center of Pediatric Nephrology and Transplantation, Cairo University, Egypt
2 Department of Internal Medicine and Endocrinology, Cairo University, Egypt
3 Vascular Laboratory, Cairo University, Egypt
4 Department of Nuclear Medicine, Cairo University, Egypt

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Date of Web Publication2-Sep-2009


Renal hemodynamics were studied using duplex Doppler ultrasonography in forty (33 females and 7 males; mean age: 12.1 ± 5.3 years) normotensive patients with recurrent urinary tract infection and with no evidence of obstructive uropathy and age matched control group of 24 healthy children and adolescents. Resistivity index (RI) and pulsatility index (PI) in both arcuate (AA) and interlobar (IA) arteries were significantly higher in patients as compared to controls (P= 0.001, 0.01 respectively). Diastolic/systolic ratio (D/S) at the same levels of renal vasculature (AA and IA) was significantly lower in study patients as compared to their controls (P= 0.01, 0.001 respectively). Moreover, scarred renal units had higher RI and PI values as well as lower D/S ratio as compared to non scarred units (p= 0.01, 0.001, 0.001 respectively).). In conclusion, intra renal vascular resistivity is significantly increased in recurrent UTI patients particularly in those sus­taining renal scarring. Further follow up studies are recommended to determine if duplex assess­ment of intrarenal vasculature could be useful as an ancillary diagnostic and/or prognostic technique in the evaluation and follow up of recurrent UTI.

How to cite this article:
Soliman NA, Saif A, Hamid AA, Moustafa H. Renal duplex doppler ultrasonography in patients with recurrent urinary tract infection. Saudi J Kidney Dis Transpl 2009;20:816-21

How to cite this URL:
Soliman NA, Saif A, Hamid AA, Moustafa H. Renal duplex doppler ultrasonography in patients with recurrent urinary tract infection. Saudi J Kidney Dis Transpl [serial online] 2009 [cited 2021 Jun 24];20:816-21. Available from: https://www.sjkdt.org/text.asp?2009/20/5/816/55368

   Introduction Top

Urinary tract infections (UTIs) in children and adolescents can be classified based on the na­tural history and subsequent evaluation and ma­nagement as first infection or recurrent infec­tion. Recurrent infections can be subcategorized as unresolved bacteriuria, bacterial persistence, and reinfection. [1] Clinical classification of UTI, such as complicated versus uncomplicated, upper versus lower, or cystitis versus pyelonephritis, imply severity of infection when, in fact, this cannot be documented clinically nor may "lesser" infections require less rigorous evaluation. [2]

Duplex ultrasonography is a non-invasive tool that has been increasingly used in clinical neph­rology. Intrarenal blood flow can be observed by color-coded duplex and flow velocity can be mea­sured by real time pulsed Doppler ultrasound. [3]

This prospective study was carried out to de­tect changes in renal blood flow velocity and vascular indices by duplex ultrasonography and to correlate these changes with clinical para­meters as well as with renal imaging results in children and adolescents with recurrent UTI.

   Methodology Top

This study was approved by the Institutional Review Board at Cairo University Children's Hospital. Forty patients (33 females and 7 males; age range 5-18 years, with a mean of 12.1 ± 5.3 years) suffering from recurrent UTI as well as 24 age and sex matched healthy children and adolescents (18 females and 6 males, age range 4-17 years, with a mean of 11.7 ± 4.8 years) were examined by color-coded renal duplex ultrasound scan. Informed consent was obtained from the parents. Patients' case notes were re­viewed particularly for:

  1. the duration of ill-ness from the first do­cumented UTI,
  2. presence or absence of vesico-ureteric reflux (VUR) and
  3. the latest calculated glomerular filtration rate (c-GFR) as calculated by Schwartz formula. [4]

All patients were normotensive at the time of the study; none of them had persistent hyper­tension (HTN) or obstructive uropathy. They all had c-GFR > 80 mL/min/1.73 m² and had been infection free for at lest 6 months prior to the study.

Imaging modalities employed in this work in­cluded:

  1. Pre-study real time renal ultrasound scan to assess renal size, Patients with small kid­neys for age and those with structural uri­nary tract anomalies were excluded from the study.
  2. Static renal scintigraphy (DMSA) scan was performed for all patients for the detection of renal scarring. [5]
  3. Color coded duplex ultrasound scan using 3.5 or 5 MHz transducer (HP Sonos 1500 machine, Hewlett Packard, Santa Clara, CA, USA). Patients were scanned in the supine position. The transducer was placed in the midline with slight inclination to the left to get a coronal section of the aorta. Each re­nal artery was identified as lying between the superior mesentric artery and the cor­responding renal vein. Flow velocities were measured by real time pulsed Doppler ul­trasonography.

The ulltrasonographer was blinded to the re­sults of DMSA scan in the study patients. Re­cordings were obtained from the main renal ar­tery as well as its main intrarenal branches (segmental, interlobar, and arcuate). For each artery, the resistivity index (RI), the pulsatility index (PI), and distolic systolic ratio (D/S) were mea­sured according to the following formulae: [6]

Mean renal RIs, PIs, and D/S ratios were used for statistical analysis of differences between patients and controls using student t-test (P value); P< 0.05 was considered significant. The correlation between the duplex indices in pa­tients and the clinical or imaging parameters were studied using the Pearson's correlation co­efficient (r value); r > 0.38 was accepted as sta­tistically significant.

   Results Top

In the study patients, the recurrence rate of episodes of UTI varied from 3 to as much as 11 times during the entire period of illness which ranged from 2-5 years (Mean ± SD 3.3 ± 0.85 years).

Ultrasonographic evaluation of our patients re­vealed no evidence of underlying obstructive congenital anomalies, only mild dilatation of the renal pelvis and/or ureters in 10/40 patients. Pre­vious DTPA scanning of these patients showed no evidence of organic obstruction, moreover indirect radionuclide cystography VCUG con­firmed the diagnosis of VUR in 8/40 patients (20%) graded II-III. VUR was bilateral in 1/8 and unilateral in 7/8 of the refluxer patients. One patient 1/40 had an isolated pelvic renal stone which was infective in nature that was surgically removed.

DMSA scintigraphy of the study patients re­vealed that 10/40 (25%) patients had evidence of renal scarring which was bilateral in only 2. Among the children with reflux, only 3/8 (37.5%) patients had renal scarring, [Figure 1].

[Table 1] demonstrates that of all the vascular indices including RI, PI in both AA and IA ar­teries were significantly higher and D/S lower in patients as compared to controls. Furthermore, high recurrence rate of UTI showed significant positive correlation to RI, PI, and negative cor­relation to D/S at both AA and IA levels. Pa­tients with renal scarring had significantly higher RI and PI values as well as lower D/S ratios (at the AA and IA levels) as compared to patients with no evidence of scarring. Nevertheless, no significant correlation was observed between any of the vascular indices and duration of infection and vesicoureteric reflux (VUR) [Table 2].

   Discussion Top

Urinary tract infection (UTI) is common and results in significant morbidity in children and adolescents. In the past few decades, a better un­derstanding of the pathogenesis and the natural history of UTI in this age group has evolved. This, together with the identification of risk fac­tors that predispose to subsequent renal paren­chymal damage, have led to the prompt, appro­priate, and thorough evaluation to minimize the acute morbidity and the long term sequelae of UTIs, such as: renal scarring, hypertension, and renal failure. [7]

The natural history of recurrent UTIs has been well documented by Winberg et al, moreover they demonstrated that the relative risk for re­current infection depends on the number of prior infections. [8] For example, one prior infection increased the risk for recurrence by 25%; this figure increased proportionately with the num­ber of infections (50% and 75% with two and three infections, respectively).

Intrarenal blood flow can be observed by color-coded duplex and the flow velocity can be measured by real time pulsed Doppler ultrasound in patients with diabetes mellitus, renal artery stenosis, chronic kidney disease and renal trans­plant recipients with some limitations. [6],[9],[10],[11],[12]

Radionuclide renal imaging studies are widely used to detect renal scarring, rule out obstruc­tive uropathies, diagnosis and follow up of VUR as well as for the assessment of relative renal function. [13],[14] Nevertheless, these scans are costly, invasive, and incur a radiation load. A non- invasive test is therefore more desirable.

Of all the vascular indices studied in this work­up, RI and PI in both AA and IA arteries were significantly higher in patients as compared to controls (P= 0.001, 0.01 respectively). Moreover, D/S at the same levels of renal vasculature (AA and IA) were significantly lower in study pa­tients as compared to their controls (P= 0.01, 0.001 respectively). This demonstrates the higher focal intra-renal vascular resistivity in patients compared to controls. Nevertheless, RI and PI were higher and D/S ratio was lower in patients compared to controls at both the main renal and segmental arteries, yet the difference did not reach statistical significance.

Platt and his co-workers demonstrated that ac­tive renal disease within the tubulointerstitial compartment (acute tubular necrosis, interstitial nephritis) or vasculitis/vasculopathy generally resulted in an elevated RI, whereas disease li­mited to the glomeruli, no matter how severe, did not significantly elevate the RI. [15] Moreover, Izumi and his associates reported the diagnostic value of Doppler ultrasound in differentiating acute tubular necrosis from prerenal azotemia by comparing RI and PI results with the frac­tional excretion of sodium, renal failure index, and urinary/serum creatinine ratio. [6]

The correlation between the studied vascular indices and clinical parameters revealed that the high recurrence rate of UTI was significantly positively correlated to RI (P= 0.02) and PI (P= 0.01), and negatively to D/S ratio (P= 0.01) at both AA and IA levels. This was again shown in kidneys with scarring on radionuclide scans.

Riccabona and co-workers demonstrated that amplitude coded-color Doppler sonography ac­curately depicted altered renal perfusion, when compared to scintigraphy or CT scan, in pedia­tric renal diseases including renal scars, UTI, reflux nephropathy among other renal diseases. [16] In another study, RI values were increased sig­nificantly in children with febrile UTI when renal parenchymal involvement (assessed by DMSA scintigraphy) was present. Refluxing kidneys and scarred kidneys also had higher RI values. [17]

Many of the previous studies utilizing Doppler ultrasonography in the evaluation of UTI were mainly addressed to febrile UTI in an attempt to differentiate acute pyelonephritis from lower urinary tract infection. [17],[18],[19],[20] Only few workers, however, did study its potential use to depict al­tered renal perfusion in pediatric renal diseases other than acute UTI including reflux nephro­pathy and renal scarring. [16]

In conclusion, our study in patients without active UTI demonstrated significant intra-renal vascular changes that predicted the possibility of recurrence of UTI. Further studies are re­commended to evaluate the role of duplex Dop­pler ultrasound in detecting altered renal hemo­dynamics and whether it helps in identifying those at high risk of recurrence and therefore permanent renal damage.

   Acknowledgement Top

The authors thank the patients and their fa­milies for participating in this study.

   References Top

1.Smellie JM, Prescod NP, Shaw PJ, et al. Child­hood reflux and urinary infection: a follow up of 10-41 years in 226 adults. Pediatr Nephrol 1998;12(9):727-36.  Back to cited text no. 1    
2.Stamey TA. Pathogenesis and treatment of urinary tract infections. Ed Baltimore, Williams & Wilkins 1980 pp 934-45.  Back to cited text no. 2    
3.Scholbach I. Doppler studies in normal kidneys of healthy children. Pediatr Nephrol 1996;10(2): 156-9.  Back to cited text no. 3    
4.Schwartz GJ, Haycock GB, Edelmann CM, Spitzer A. A simple method estimate of glome­rular filtration rate in children derived from Body lengh and plasma creatinine. Pediatrics 1976;58: 259-63.  Back to cited text no. 4    
5.Taylor CM, Chapman S. Imaging: Nuclear medicine. In Handbook of Renal Investigations in Children. Wright, Kent 1989;pp148-149.  Back to cited text no. 5    
6.Izumi M, Sugiura T, Nakamura H, Nagatoya K, Imai E, Hori M. Differential diagnosis of pre­renal azotemia from acute tubular necrosis and prediction of recovery by Doppler ultrasound. Am J Kidney Dis 2000;35(4):713-9.  Back to cited text no. 6    
7.Chon CH. Pediatric urinary tract infections. Pediatr Clin Nephrol Am 2001;48(6):1441-59.  Back to cited text no. 7    
8.Winberg J, Andersen HJ, Bergstrom T, Jacobsson B, Larson H, Lincoln K. Epidemiology of symp­tomatic urinary tract infection in childhood. Acta Paediatr Scand 1974; 252 Suppl:1-20.  Back to cited text no. 8    
9.Perrella R, Duerinckx A, Tessler F, et al. Eva­luation of renal transplant dysfunction by duplex Doppler sonography: A prospective study and review of the literature. Am J Kidney Dis 1990; 15:544-50.  Back to cited text no. 9    
10.Distler A, Spies K. Diagnostic procedure in renovascular hypertension. Clin Nephrol 1991; 36:174-80.  Back to cited text no. 10    
11.Ishimura E, Nishizawa Y, Kawagishi T, et al. Intra-renal hemodynamic abnormalities in dia­betic nephropathy measured by duplex Doppler sonography. Kidney Int 1997;51:1920-7.  Back to cited text no. 11    
12.Mostbeck G, Kain R, Mallek R, et al. Duplex Doppler sonography in renal parenchymal disease. J Ultrasound Med 1991;10:189-94.  Back to cited text no. 12    
13.Gordon I. Imaging the kidneys and the urinary tract. In: Holliday MA; Barratt TM; Avner (Eds) Pediatric Nephrology, 4 th edn. Kogan BA, London, 2000.pp 421-37.  Back to cited text no. 13    
14.Heyman S. Radionuclide studies of the genito­urinary tract. In: Miller JH; Gelfand MJ (Eds). Pediatric Nuclear Imaging 1 st edn. Saunders, Philadelphia, London, 1994.pp 195-251.  Back to cited text no. 14    
15.Platt JF, Ellis JH, Rubin JM, DiPietro MA, Sedman AB. Intrarenal arterial doppler sono­graphy in patients with nonobstructive renal disease: Correlation of resistive index with biopsy findings. AJR Am J Roentgenol 1990; 154:1223-7.  Back to cited text no. 15    
16.Riccabona M, Ring E, Schwinger W, Aigner R. Amplitude coded color Doppler sonography in paediatric renal disease. Eur Radiol 2001;11(5): 861-6.  Back to cited text no. 16    
17.Ozcelik G, Polat TB, Aktas S, Cetinkaya F. Resistive index in febrile urinary tract infec­tions: predictive value of renal outcome. Pediatr Nephrol 2004;19(2):148-52.  Back to cited text no. 17    
18.Berro Y, Baratte B, Seryer D, et al. Comparison between scintigraphy, B mode, and power Doppler sonography in acute pyelonephritis in children. J Radiol 2000;81(5):523-7.  Back to cited text no. 18    
19.Akdilli A, Karaman CZ, Basak O, Aydogdu A. The diagnostic value of intrarenal colour duplex Doppler ultrasonography in children with lower urinary tract infection. Pediatr Radiol 1999;29 (12):897-900.  Back to cited text no. 19    
20.Basiratnia M, Noohi AH, Lotfi M, Alavi MS. Power Doppler sonographic evaluation of acute childhood pyelonephritis. Pediatr Nephrol 2006; 21(12):1854-7.  Back to cited text no. 20    

Correspondence Address:
Neveen A Soliman
Center of Pediatric Nephrology and Transplantation, Egyptian Group for Orphan Renal Diseases Cairo University, Cairo, 11451
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PMID: 19736480

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