Key words: Reflux nephropathy, renal scarring, vesico-ureteric reflux (VUR), urinary tact infection (UTI).
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Urinary tract infection (UTI) is a frequent problem in infants and children. In Jahra area, the overall incidence of UTI is 5.5% (1). Vesico-ureteral reflux (VUR) has been reported in 35-40% of children with UTI; and renal scarring may be seen in 9.5-38% of those with reflux (2). In children with a history of recurrent UTI, renal scarring is even more common; it may reach up to 25% (3, 4).

Renal reflux can result in renal scarring, renal insufficiency, rennin-mediated hypertension and end-stage renal disease (5). There is abundant clinical and experimental evidence that UTI and VUR is important in the pathogenesis of renal scarring (6, 7). Bacteria can reach the kidney from the bladder by the reflux, especially when bladder wall inflammation is co-existing, leading to formation of cortical micro abscesses and development of renal scars. However, it has been shown that antibacterial treatment can arrest or prevent the development of scarring (8).

As reflux nephropathy is irreversible, the objective of this study was to determine the frequency of renal scars and evaluate reflux in children with established UTI attending Pediatric Outpatient Department in Al-Jahra Hospital, Kuwait.

Sixty-nine children with proved UTI were included in this study. Sixty-seven were females and two were males. Their ages ranged from 1 year and 8 months to 8 years and 5 months. Details of presentation, treatment and patient's and family history were obtained. Further information was obtained from parent's interview when necessary. All underwent renal ultrasonography and micturation cystourethrography (MCUG) as a part of initial evaluation. Dimercapto Succinic Acid (DMSA) scans were obtained initially and 4-6 months after the last episode of pyelonephritis. Grading of VUR was based on the International Reflux Committee classification (9). Renal Scars grading was based on Goldarich and co-workers grading system (10).

All patients were treated with appropriate antibiotic therapy and remained on prophylaxis as indicated. They were followed up and urine routine, urine culture & sensitivity, renal function tests, blood pressure measurements and growth parameters were checked regularly.

Of the 69 patients who did DMSA scan (Table 2), 12 had scars on initial diagnosis and 3 developed them 4-6 months later (21.7%). Their ages ranged from one year and eight months to eight years and five months. One was male and 14 were females. The male patient was circumcised. Forty-five patients (65%) had history of recurrent UTI (Table 1). E.coli was the cause of infection in all patients, except one who had Klebsella. The scars were more common in the left kidney (60%). In 11 patients the scars were in the upper lobe of the kidney (73.3%) and 4 in the lower lobe (26.7%). Clinically they were normotensive and had normal growth and development.
Varying grades of vesico-ureteral reflux (VUR) was detected in 23 patients out of 53 (Table 3), who did MCUG (43.4%); 14 with grade I, 4 with grade II, 3 with grade III and 2 with grade IV reflux. Fourteen patients had bilateral reflux and 9 had unilateral reflux. Reflux grade 1, and scars stage I & III were the most prevalent sequelae following UTI. Of the fifteen children with renal scars 9 had VUR; 7 with grade I reflux and 2 with grade II. Ultra-sound of abdomen showed congenital anomalies in 3 (33.3%), one with congenital polycystic kidney, one with congenital multicystic kidney and the third with congenital left hydronephrosis (Table 3).

Reflux nephropathy is known to be a major cause of renal failure in children. Renal scintigraphy with dimercaptosuccinic acid (DMSA) is a valid diagnostic tool for confirming the presence of acute pyelonephritis as well as for documenting the presence of renal scarring. Its sensitivity and specifity are more than intravenous pyelography; IVP (11&12). Only 40% of our patients with proved renal scarring showed changes on IVP. However, the routine use of DMSA scan during the acute illness is not considered necessary (13). In our study, 15 out of 69 studied children with UTI had renal scarring (21.7%). Other authors showed different results. Szlyk et al (14) found that 38% of their patients had renal scars, while Polito et al (15) reported 37%. The low incidence of renal scarring in our cases may be due to early treatment of our patients as there is evidence that delay in diagnosis and treatment of UTI can contribute to the development of renal scarring (16 & 17).

Risks of hypertension and chronic renal failure are higher with diffuse scarring (18). Hadi et al (2) showed that hypertension occurred in 7.1% of their patients over a 6-year period. In our study, none of our patients suffered from hypertension. However, a long period of follow-up is necessary to verify the occurrence of this complication.

Vesico-ureteral reflux (VUR), has been identified as a risk factor for the development of UTI and renal scarring. Dick et al (2) showed that 62.5% of their patients with VUR had renal scarring. Lana et al (20) reported that 60% of girls and 44% of boys in the first year of life with VUR and UTI had renal scarring. Others showed similar results (21). In our study, only 9 patients out of 15 with renal scarring (60%) had VUR (Fig. 1). This proves that; although VUR is a risk factor for development of renal scarring, the lesion can still develop without VUR. This may be due to intra-renal reflux facilitated by the flat papillae in the kidney. Bacteria can also reach the kidney through transient reflux occurring with severe UTI and bladder wall inflammation, or by binding to epithelial cell surface in some children with specific blood groups.

Radiologists often report various degrees of dilatation of the collecting system of the kidney in patients with UTI on renal ultrasonography (22). However, in our study the ultrasound findings were not predictive of VUR and VCUG was necessary to rule out VUR, regardless of renal ultrasound findings. A similar conclusion was noted by S Mahant et al (22). Davey and colleagues (23), as well, found that the frequency of VUR in children with mild renal pelvic distension did not differ significantly from that in children without distension on renal ultrasound.

Our study suggests that incidence of renal scarring is high (21.7%) in children with UTI and that absence of VUR is not protective, as renal scarring can occur without VUR. We recommend early diagnosis and aggressive treatment of children with UTI. We also recommend performing DMSA scan for all children with UTI, especially in younger ages and in those with high grade VUR.

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