Background: Dynamic renal scan has become one of the most effective techniques to investigate the kidney parenchymal function, also the urine collecting and drainage system, in both adults and children. Compared with adults, it is the most commonly used test in children and accounts for more than half of the indications for nuclear medicine unit. In City Children's Hospital, dynamic renal scan has been implemented since the beginning of 2018 and initially showed its clearly role in facilitating the decision on treatment and follow-up strategy of pediatric patients. Therefore, we carry out this study to evaluate the results of dynamic renal scan application of the unit.

Objective: To assess the results of application of dynamic renal scan with ^99mTc-DTPA on pediatric patients in City Children's Hospital.

Subject and method: We retrospectively examined data derived from 671 pediatric patients aged 01 month to 15 years in City Children’s Hospital who underwent at least 1 ^99Tc DTPA dynamic renal scan with diuretic challenge test from June 2018  to March 2022.

Results: There were a total of 740 performed scans, including 611 patients underwent once, 52 patients underwent twice, 7 patients underwent threetimes and 1 patient underwent fourtimes. Among them, there are 454 boys and 217 girls with a male/female ratio of 2/1. The age of the pediatric patients at the time of scanning varied, from 1 month to 15 years old. However, there is a clear dominant distribution for the group of patients under 5 years old, accounting for 516 cases (~69.7%%), which is more than 3 times the number for the group of patients aged 5 to 10 years and about 10 times for the group of patients over 10 years old, 175 cases (~23.7%) and 49 cases (~6.6%) respectively.

Many different geographical locations in the country, where the patients come from, were noted. However the majority of cases live in Ho Chi Minh City, the number is 218 cases, accounting for ~30% of the total, followed by the west provinces and provinces from central region, as well as the Highlands area.

These patients were all diagnosed, followed, and treated in 03 large pediatric hospitals of Ho Chi Minh City, includes Children's Hospital 1, Children's Hospital 2 and City Children's Hospital with respective distribution rate of 248 patients (36.9%), 313 patients (46.6%) and 111 patients (~16.5%). The diagnosis and follow-up by dynamic renal scan were totally perfrom at Nuclear Medicine Unit of the City Children's Hospital.

For pre-acquisition diagnosis, after reviewing the anatomical imaging results, there were 436 patients (~65.0%) had a condition of left hydronephrosis/hydroureteronephrosis. 154 patients (~ 23.0%) had a condition of right hydronephrosis/hydroureteronephrosis, 74 patients (~ 11.1%) had a condition of bilateral hydronephrosis/hydroureteronephrosis, and the remains, including 6 children (~0.9 %) had following medical conditions: 02 children with neurogenic bladder, 02 children with right kidney polycystic dysplasia, 01 child with left kidney tumor and 01 child has renal tubular disease.

For imaging interpretation, in the group of left hydronephrosis/hydroureteronephrosis (N = 436), there were 163 patients (~ 37.3%), who had impaired renal function (DRF < 40 %), 323 patients (~ 74.0%) had urinary tract obstruction (T half index prolongs more than 20 minutes, 99 patients (~ 22,7%) had urinary tract obstruction accompanied with impaired renal function, 37 patients (~ 8,4%) had severe impaired renal function inducing difficulty in urinary obstruction detection.

In the group of right hydronephrosis/hydroureteronephrosis (N = 154), 44 patients (~ 28.5%) had impaired renal function, 69 patients (~ 44.8%) had urinary tract obstruction, 24 patients (5,5~ 1%) had urinary tract obstruction accompanied with impaired renal function. 5 patients (~ 3,2%) had severe impaired renal function inducing difficulty in urinary obstruction detection.

Similarly, in the group of bilateral hydronephrosis/hydroureteronephrosis (N = 74), 31 patients (~ 41.8%) had impaired renal function in one or both kidneys, 45 patients ( ~ 60.0%) had urinary tract obstruction on one or both sides, 02 patients (~ 2,7%) had urinary tract obstruction accompanied impaired renal function, 6 patients (~ 8,1%) had severe impaired renal function inducing difficulty in urinary obstruction detection.

In addition, among pediatric patients who underwent at least 2 scans (N = 60), 18 patients (~ 30,0 %) progressed to impaired renal function (DRF decreases more than 5 %) and 08 patients (~ 13,3%) appeared increasing urinary obstruction (change to upsloped time-activity curve). The intervals between follow-up scans varied from 03 months to 24 months, however, most of these cases were detected within 12 months since the first scan.

As a result, we found that among 671 patients in the first scan, there were 125 cases (~ 18.6%) of urinary tract obstruction accompanied impaired renal function and among 60 patients with at least 2 scans, there were 18 cases (~ 30,0 %) found to have impaired renal function in the follow-up scans. This is the pediatric group at risk of progressing to loss of kidney function.

Conclusion: Dynamic renal scan with ^99mTc DTPA has been currently one of the important tools in the diagnosis and follow-up strategy of hydronephrosis/hydroureteronephrosis in pediatric patients, especially the role of early detection of kidney at risk of progression to loss of function, which helps determine timely intervention measures to preserve kidney function. The application of this technique in City Children's Hospital has initially shown the benefits as an effective imaging for treatment decision besides other imaging studies.