Usefulness of parametric renal clearance images in the assessment of basic risk factors for renalnal clearance images in the assessment of basic risk factors for renal scarring in children with recurrent urinary tract infections.

BACKGROUND: Clinically confirmed incidents of acute pyelonephritis (APN) following recurrent infections of urinary tract (UTI) form basic risk factors for renal scarring in children. Vesico-uretheral reflux (VUR) of higher grade is additional risk factor for this scarring. Opinions on diagnostic value of summed sequential images of renal uptake phase (SUM) of dynamic renal scintigraphy in detection of renal scars are diverse. However, several publications point to higher diagnostic efficacy of clearance parametric images (PAR) generated from this study. THE AIM OF THE STUDY: To establish a clinical value of parametric renal clearance images in detection of renal scarring. MATERIAL AND METHODS: A prospective study was performed in a group of 91 children at the age of 4 to 18 years with recurrent UTI. Clinically documented incidents of APN were noted in 32 children: in 8 cases - one and in the remaining 24 - 2 to 5 (mean 3) incidents. In the remaining 59 patients only infections of the lower part of urinary tract were diagnosed. Static renal 99mTc-DMSA SPECT study and after 2-4 days dynamic renal studies (99mTc-EC) were performed in every patient not earlier than 6 months after the last documented incident of UTI. PAR images generated from a dynamic study by in-house developed software and SUM images were compared with a gold standard SPECT study. RESULTS: Percentages of children with detected renal scar(s) with SPECT and PAR methods amounted to 55% and 54%, respectively and were statistically significantly higher (p < 0.0001) than with SUM method - 31%. Scars in children with history of APN detected with SPECT and PAR methods were significantly more frequent than with infections of only lower part of urinary tract (72% vs. 46%; p = 0.017 and 69% vs. 46%; p = 0.036, respectively). A SUM method did not reveal statistically significant differences between frequencies of detection of scars in groups specified above - 38% vs. 27% (p = 0.31). Both SPECT and PAR methods showed also that frequencies of occurrence of renal scars in children with higher grades of VUR were higher than without or with lower grades of VUR: 79% vs. 50% (p = 0.048) and 79% vs. 49% (p = 0.04). A SUM method did not reveal higher frequency of renal scars in children with high VUR grades: 36% vs. 30% (p = 0.44). CONCLUSION: Results obtained with PAR and SPECT methods were similar. An advantage of PAR over SUM images obtained from a dynamic renal scintigraphy in detection of renal scars in children with UTI was confirmed.

Assessment of clinical usefulness of parametric clearance images in diagnosis of kidney cicatrisation in children with chronic infections of the urinary tract.

BACKGROUND: Cicatrisation of the renal cortex is closely related to chronic infections of the urinary system. Static renal scintigraphy is used as the method enabling detection of local defects of radiopharmaceutical uptake, and is treated as the "gold standard" in the diagnosis of renal scars. The aim of the reported investigation was a comparison of the diagnostic efficacy of parametric clearance images and the conventional summation images - obtained from dynamic scintigraphy - in the detection of local defects of renal function. As the "gold standard" for the above comparison, the static scintigraphy of kidneys was accepted. MATERIAL AND METHODS: Forty-one patients (age 4-19 years), 28 girls and 13 boys, participated in the study. Altogether, 73 kidneys were analyzed (in 9 patients, only one kidney). In each patient dynamic renal scintigraphy was performed after IV administration of 99mTc EC (ethylenedicysteine) and static planar renal scintigraphy using 99mTc-DMSA (dimercaptosuccinic acid) as a reference method. From the dynamic study, summation and parametric clearance images were generated. Each kidney was divided into 3 segments (upper, middle, lower); altogether 219 segments were evaluated by modified Howard's scale. Planar and oblique projection images were compared with corresponding summation and parametric clearance images. RESULTS AND CONCLUSIONS: Parametric clearance imaging has a higher sensitivity and accuracy for detection of regional post-inflammatory changes in the kidneys than conventional summation images (p < 0.05) and shows parenchymal changes similarly to static scintigraphy (high Cohen's kappa index).