An evaluation of the use of 99Tcm-dimercaptosuccinic acid (DMSA) as a static renal imaging agent

Combination of DMSA-Scintigraphy and Hippuran Renography in Unilateral Obstructive Nephropathy

The renal handling of dimercaptosuccinic acid and hippuran differs. This might be used in unilateral obstructive nephropathy in order to predict potential functional recovery following intervention. The theory was evaluated on a retrospective basis in 17 patients, who primarily had a nephrostomy. If the DMSA-uptake rate in the diseased kidney was more than 10 per cent higher than that of hippuran, the uptake rate of hippuran increased following relief of obstruction. Use of the two radiopharmaceuticals, thus, may have great impact on the clinical decision, since in case of a difference some function may be saved by immediate intervention.

Plain Radiography, Renography, and 99mTc-DMSA Renal Scintigraphy before and after Extracorporeal Shock Wave Lithotripsy for Urolithiasis

Eighteen patients were evaluated before and 5 weeks after the first treatment with extracorporeal shock wave lithotripsy (ESWL) using abdominal plain radiography, 131I-hippuran probe renography, and 99mTc-dimercaptosuccinic acid scintigraphy. In 6 patients no urolithiasis was present on the post ESWL plain radiograph, in 7 the size had decreased, and in 5 the stone mass was unchanged. The renograms were within normal range in the 6 patients who were cured by ESWL, whereas this was the case for only 4 of the 12 who still had renal calculi. In 2 patients pelvic stones had descended into the ureter after ESWL, and the renograms indicated obstruction. Another 3 patients had ureteral stones, whereas in the remaining 7 patients only pelvic stones were found on the plain radiographs. In no patient did the scintigrams reveal scars. It is concluded that abdominal plain radiography of the urinary tract and probe renography are complementary and sufficient in the monitoring of patients with urolithiasis post ESWL.

Single-photon emission CT using (99m)Tc-dimercaptosuccinic acid (DMSA) for characterization of suspected renal masses

OBJECTIVE

A retrospective analysis of the clinical utility of (99m)Tc-dimercaptosuccinic acid (DMSA) single photon emission CT (SPECT) for characterization of suspected renal masses.

METHODS

15 patients who had undergone (99m)Tc-DMSA SPECT were identified, and 13 patients also had SPECT/CT. (99m)Tc-DMSA uptake in the renal lesion was characterized semiquantitatively. Other imaging tests, histology and clinical data were available for correlation.

RESULTS

(99m)Tc-DMSA was not taken up in all five renal masses with histological confirmation of malignancy (uptake 7-19% of normal renal tissue); in two further masses, which were clinically likely to be malignant; and in one indeterminate mass (lack of sufficiently long follow-up). No renal malignancy was identified in any of the seven patients whose renal masses had normal (99m)Tc-DMSA uptake (41-130%).

CONCLUSION

Although caution with regard to applying those results in clinical practice must be advised, owing to the retrospective nature of this report and the small number of patients included, it seems that (99m)Tc-DMSA SPECT shows a clinically useful diagnostic accuracy for distinguishing true renal masses (which in many cases require surgery) from pseudomasses.

ADVANCES IN KNOWLEDGE

(99m)Tc-DMSA SPECT is a clinically useful adjunct test for characterization of suspected renal masses.

Decreased concentrating capacity in children with febrile urinary tract infection and normal 99mTc-dimercaptosuccinic acid scan: does medullonephritis exist?

BACKGROUND

Although 99mTc-dimercaptosuccinic acid (DMSA) scan is considered the gold standard for the diagnosis of acute pyelonephritis (AP), sometimes it produces false results in children with clinical features of AP. There are no studies on the comparison of the sensitivity of DMSA and concentrating capacity test.

METHODS

Eighty-five infants with AP of less than one year old were studied to evaluate whether they had real AP or not. Data were compared between infants with an abnormal (group A, n=64) and those with a normal DMSA scan (group B, n=21) respectively. A DDAVP test was performed for each infant.

RESULTS

All the infants in both groups presented a high level of C-reactive protein and fever (≥38°C). There were no differences in clinical and analytical variables except C-reactive protein level in the two groups. Both groups exhibited a low urinary osmolality (87.5% in the group A vs. 85.7% in the group B). The patients with normal DMSA and decreased concentrating capacity have some renal parenchymal damage and not only a lower urinary infection. Of the infants with an abnormal DMSA scan, 33.9% showed renal scars after 6-12 months. No infant with a normal DMSA scan showed scars. The biochemical variables in both groups of infants were not related to vesicoureteral refl ux.

CONCLUSION

Infants with AP, normal DMSA scan and low concentrating capacity may be characterized by a localized infection in the medulla (medullonephritis) or by a false negative DMSA scan.

(99m)Tc-DMSA absolute and relative renal uptake in cats: procedure and normal values

In this study we investigated the influence of technical factors (positioning, background (BG) correction and attenuation correction) on qualitative and quantitative (absolute (AU) and relative (RU) uptake) assessment of feline kidneys with (99m)technetium labelled dimercaptosuccinic acid ((99m)Tc-DMSA). Eleven healthy adult cats were included. Influence of BG and depth correction on quantitative assessment was evaluated. Depth correction was based on the geometric mean method (using dorsal and ventral images) and the use of two standards placed over each individual kidney. Visual evaluation showed superiority of dorsal and ventral over lateral positioning due to increased separation of the kidneys permitting region of interest (ROI) placement without overlap. No apparent influence of BG correction was found for RU. However, AU was systematically overestimated without BG correction. Depth correction did not seem to affect RU in most cases, however, in some cats the differences were not negligible. The values for AU without depth correction were lower compared to depth corrected values.

Estimation of absolute renal uptake with technetium-99m dimercaptosuccinic acid: direct comparison with the radioactivity of nephrectomy specimens

CONTEXT AND OBJECTIVE

Studies using radionuclides are the most appropriate method for estimating renal function. Dimercaptosuccinic acid chelate labeled with technetium-99m (99mTc-DMSA) is the radiopharmaceutical of choice for high-resolution imaging of the renal cortex and estimation of the functional renal mass. The aim of this study was to evaluate a simplified method for determining the absolute renal uptake (ARU) of 99mTc-DMSA prior to nephrectomy, using the radioactivity counts of nephrectomy specimens as the gold standard.

DESIGN AND SETTING

Prospective study at the Division of Nuclear Medicine, Department of Radiology, Universidade Estadual de Campinas.

METHODS

Seventeen patients (12 females; range 22-82 years old; mean age 50.8 years old) underwent nephrectomy for various reasons. Renal scintigraphy was performed three to four hours after intravenous administration of a mean dose of 188.7 MBq (5.1 mCi) of 99mTc-DMSA, which was done six to 24 hours before surgery. The in vivo renal uptake of 99mTc-DMSA was determined using the radioactivity of the syringe before the injection (measured using a dose calibrator) and the images of the syringe and kidneys, obtained from a scintillation camera. After surgery, the reference value for renal uptake of 99mTc-DMSA was determined by measuring the radioactivity of the nephrectomy specimen using the same dose calibrator.

RESULTS

The ARU measurements were very similar to those obtained using the reference method, as determined by linear regression (r-squared = 0.96).

CONCLUSION

ARU estimation using the proposed method before nephrectomy seems to be accurate and feasible for routine use.

Renal damage in vesico-ureteric reflux

OBJECTIVE

To detect the different extent of renal parenchymal involvement in primary vesico-ureteric reflux (VUR), and to evaluate the relationship between VUR grade, patient age and different patterns of parenchymal damage.

PATIENTS AND METHODS

This blinded retrospective study included 197 consecutive children (mean age 4.26 years, range 1 month to 13 years) with primary VUR detected by voiding cysto-urethrography (VCUG), 99mTc-dimercaptosuccinic acid (DMSA; 120 MBq/1.73 m2) renal scintigraphy, with scanning for 3 h after intravenous injection. An abnormal DMSA scan was classified into three subtypes: cortical defects as a single scar (SS), multiple cortical scarring (MS) and diffuse reduced uptake with small renal size. Renal absolute uptake (AU), and split-kidney relative uptake were evaluated in refluxing and nonrefluxing renal units, and correlated with parenchymal damage and patient age. Student's t-test and the chi-square test were used for the statistical analysis.

RESULTS

In all, 282 refluxing and 112 nonrefluxing units were assessed. Renal damage was detected in 188 of 282 units with VUR (67%) and in 18 of 112 (16%) contralateral nonrefluxing kidneys. The mean AU was 18.7% in kidneys with VUR and 29% in nonrefluxing units (P < 0.001). The mean (SD) AU decreased from lower to higher grades of VUR, i.e. grade 0 VUR (group A), 28.97 (9.71); grade 1-3 (group B), 21.28 (8.33); grade 4-5 (group C), 14.78 (8.02). The differences were statistically significant (A vs B, B vs C, both P < 0.001). Renal damage was differently distributed in the three groups: 69 of 109 kidneys (63%) in group C (MS prevalent), 39 of 173 (22.5%) in group B (SS prevalent) and 17 of 112 (15.2%) in group A. There was no significant difference in the distribution of renal damage subtypes in patients aged < or > 2 years (SS 19.6% vs 17.9%, MS 29.6% vs 30.1%, small size 48.2% vs 46.3%). The VUR was severe (group C) in 65% of patients aged < 2 years and in 46% aged > 2 years (chi-square, P = 0.016).

CONCLUSIONS

VUR is commonly associated with renal damage. Age (< or > 2 years) did not significantly influence the kidney lesion subtype. Reduced parenchymal function (AU) progressively decreased with the severity of VUR. Focal MS, reduced size and relative uptake were significantly more common in severe VUR, leading to multifocal lesions and hypo-dysplasia. Renal scarring was present in up to 15% of contralateral nonrefluxing kidneys. Severe VUR behaved differently from lesser VUR in the renal scan parenchymal uptake.

Consensus on renal cortical scintigraphy in children with urinary tract infection. Scientific Committee of Radionuclides in Nephrourology

A questionnaire related to cortical scintigraphy in children with urinary tract infection was submitted to 30 experts. A wide consensus was reached on several issues related to planar images: 99mTc dimercapto succinic acid (DMSA) appears as the most appropriate tracer for renal imaging; dynamic tracers are considered to be inferior, in particular 99mTc diethylenetriaminepentaacetate, which is not recommended. The general opinion is that DMSA scintigraphy is not feasible with a minimal dose below 15 MBq, whereas the maximum dose should not be higher than 110 MBq. The dose schedule generally is based on body surface area, and sedation is only exceptionally given to children. Images are obtained 2 to 3 hours after injection, preferably with high resolution collimators; pinhole images are used by only half of the experts. Posterior and posterior oblique views are used by most of the experts, and the posterior view is acquired in supine positions. At least 200.000 kcounts or 5 minute acquisition is required for nonzoomed images. As a quality control, experts check the presence of blurred or double outlines on the DMSA images. Color images are not used and experts report on film or directly on the computer screen. As far as normal DMSA images are concerned, most experts agree on several normal variants. Hydronephrosis is not a contraindication for DMSA scintigraphy but constitutes a pitfall. Differential renal function generally is measured, but no consensus is reached whether or not background should be subtracted. Most of the experts consider 45% as the lowest normal value. A consensus is reached on some scintigraphic aspects that are likely to improve and on some others that probably represent persistent sequelae. There is a wide consensus for the systematic use of DMSA scintigraphy for detection of renal sequelae, whereas only 58% of the experts are systematically performing this examination during the acute phase of infection.

Tc-99m DTPA renal scintigraphy using deconvolution analysis with six functional images of the mean time to evaluate acute pyelonephritis

In 38 children with proved P-fimbriated Escherichia coli acute pyelonephritis, Tc-99m DTPA dynamic renal scintigraphy in the zoom mode using deconvolution analysis was performed, and the results were compared with those of Tc-99m DMSA scans. From the dynamic study, six functional images of the mean time were generated. Each functional image was analyzed separately to search for focal areas of increased mean time within the kidney contour, especially over the kidney parenchyma. Time-activity curves from these areas were generated and analyzed. Tc-99m DMSA scintigraphy showed generalized or focal decreased uptake in 32 (41.8%) kidneys, and deconvolution analysis of Tc-99m DTPA scintigraphy revealed pathologic renographic curves in 58 (77.6%) kidneys. Prolonged whole-kidney and normal renal parenchymal transit times (dilatation without obstruction) were found in 38 (50%) kidneys, whereas prolonged whole-kidney and renal parenchymal transit times (dilatation with obstruction) were observed in 20 (27.6%) kidneys. Separate analysis of each of the six functional images of the mean time showed focal areas of increased mean time in the kidney parenchyma of 11 kidneys. In five cases, time-activity curves from these areas showed a sharp increase of activity on the descending part of the curve, which might reflect the return of urine from the collecting system into kidney cortex (i.e., intrarenal reflux). These results showed that in a urinary tract with acute pyelonephritis, urodynamic changes may lead to obstructive nephropathy and intrarenal reflux. Tc-99m DTPA renal scintigraphy in the zoom mode using deconvolution analysis with six functional images of the mean time has proved to be a valuable method to evaluate acute pyelonephritis, thus allowing dynamic and morphologic analysis of the urinary tract at the same time.

Quantitative technetium-99M dimercaptosuccinic acid renal scanning in children

OBJECTIVES

To develop a method for assessing absolute renal function (as well as morphology) in children, using gamma camera imaging of intravenously injected technetium-99m (99mTc) dimercaptosuccinic acid (DMSA).

METHODS

Forty-five children (ages 1 week to 10 years; mean, 2.0 years) were imaged using a planar technique in which not only the appearance but the absolute amount of intravenously administered 99mTc DMSA taken up by the kidneys was calculated for each child and compared with contemporaneous determinations of creatinine clearance.

RESULTS

There was a close correlation between the absolute DMSA uptake and creatinine clearance (r = 0.752).

CONCLUSIONS

Renal function in children, expressed as creatinine clearance, can be accurately estimated by measuring absolute DMSA uptake with planar gamma camera imaging using 99mTc DMSA.

Renal function up to 16 years after conduit (refluxing or anti-reflux anastomosis) or continent urinary diversion. 2. Renal scarring and location of bacteriuria

OBJECTIVE

To evaluate the importance of refluxing versus anti-reflux ureteric implantation for the development of renal scarring in patients with a conduit or continent urinary diversion and for the incidence of bacteriuria in the upper urinary tract of patients with a conduit.

PATIENTS AND METHODS

Renal scintigraphy using 99mTc-dimercaptosuccinic acid was performed on 32 of 37 evaluable patients from a prospective, randomized study at a mean of 150 months (range 102-198) after urinary diversion. In five patients with a conduit diversion and unilateral renal scarring, urine was samples for culture from the proximal end of the conduit and from both renal pelvices by direct percutaneous aspiration.

RESULTS

Of 35 renal units (18 patients), studied after conduit diversion, scarring was found in 11 (two grade I, six grade II and three grade III) of 17 with refluxing anastomosis and in six (one grade I, four grade II and one grade III) of 18 with anti-reflux anastomosis (P = 0.06). Of 25 renal units (14 patients) after continent diversion, 16 showed scarring (seven grade I and nine grade II). Bacteriuria was found in four of five upper urinary tracts with a refluxing anastomosis, but in only one of five with an anti-reflux anastomosis. In these five patients scarring was present in all kidneys with refluxing anastomosis.

CONCLUSION

Anti-reflux ureteric anastomosis seems to be important for preventing scarring and bacteriuria in the upper urinary tract of patients with a conduit urinary diversion. Despite the anti-reflux technique of ureteric implantation, most patients with a continent reservoir had renal scarring, though it was generally less severe than in patients with a conduit urinary diversion.

Comparison of DMSA scintigraphy with intravenous urography for the detection of renal scarring and its correlation with vesicoureteric reflux

A series of 208 patients was prospectively assessed for reflux nephropathy by intravenous urography (IVU) and 99mTc-dimercaptosuccinate (DMSA) scintigraphy. All patients were studied at least 3 months after their most recent urinary tract infection and micturating cystourethrography (MCU) was performed prior to the scintigraphic studies. DMSA scintigraphy detected significantly more cortical abnormalities than did IVU. There was also a correlation between cortical abnormalities in the DMSA studies and the degree of reflux on MCU. The validity of DMSA as a cortical imaging agent is evaluated and the histological evidence for its efficacy derived from the animal model is reviewed, lending weight to its establishment as the "gold standard" for renal cortical scarring.

Single photon emission computed tomography with Tc-99m-dimercaptosuccinic acid in patients with upper urinary tract infection and/or vesicoureteral reflux

By means of Tc-99m dimercaptosuccinic acid (DMSA) scintigraphy, an established method for assessing renal cortical damage, we evaluated the pick-up rate for renal defects (scars) by single photon computed tomography (SPECT) and planar images of 10 normal volunteers, and 58 patients (70 scintigrams) with upper urinary tract infections, most of whom had a history of vesicoureteral reflux (VUR). The positive study rate for renal defects depended on the severity of VUR. The overall positive rates for renal cortical defects obtained by DMSA SPECT imaging and DMSA planar imaging were 60% and 43%, respectively, and the difference between these was significant (p less than 0.005). The mean absolute individual renal uptake (/injected dose) at 2 hours post-injection was decreased in kidneys with defects detected by SPECT alone. The positive study rate for intravenous urography (IVU) depended on the grade of VUR and was 15% overall. DMSA SPECT imaging detects renal cortical defects at greater frequency than previously achieved.

The detection of reflux nephropathy in infants by 99mtechnetium dimercaptosuccinic acid studies

Dimercaptosuccinic acid (DMSA) studies were performed in 113 infants less than 1 year old at risk of renal scarring. Of these patients 86 presented with urinary tract infection and 27 were asymptomatic. A voiding cystourethrogram was performed in all cases and excretory urography (IVP) was done in 99. More abnormalities were detected by DMSA study when compared to scars on IVP. When both studies were abnormal there was an excellent correlation on a site by site basis. Fever or systemic disorder was not a reliable sign to determine whether there was upper tract involvement with infection. The incidence of DMSA abnormalities in infants increased with high grade vesicoureteral reflux and decreased with low grade reflux. There was no significant difference in the incidence of abnormal kidneys between the infected and noninfected groups, suggesting that renal scarring may occur with sterile reflux.

Comparison of 99Tcm dimercaptosuccinic acid scans and intravenous urography in children

A retrospective comparison of 99Tcm dimercaptosuccinic acid (DMSA) scans and intravenous urograms (IVUs) was performed on a large, unselected paediatric population to assess critically the relative merits of these two techniques. A total of 205 children were studied, providing 388 kidneys for comparison. The studies agreed in 81%, both being normal in 39%, and both abnormal in 42%. In 28 kidneys (7%), the IVU was abnormal when the 99Tcm DMSA was normal. There was a collecting system abnormality in 27 kidneys, but 10 kidneys also showed a parenchymal abnormality. In all these the parenchymal abnormality was global thinning on the IVU, and the contralateral kidney was small. In 40 kidneys (10%) the 99Tcm DMSA was abnormal when the IVU was normal: the abnormalities demonstrated were predominantly focal defects. After excluding IVUs of poor diagnostic quality, only 14 kidneys (3.6%) showed this disparity. The important clinical subgroups are infection, with or without reflux (27 kidneys), hypertension (4) and neonates with poor renal function (2). The one false positive 99Tcm DMSA was a result of an anatomical variant. Global thinning in a "normal" kidney on a 99Tcm DMSA scan may be overlooked when the contralateral kidney is poorly functioning and small.

A kinetic model for 99mTc-DMSA in the rat

A pharmacokinetic model was developed for the renal imaging agent 99mTc-DMSA in anesthetized rats, which incorporated data from serial measurements of blood and urine simultaneously with dynamic images obtained over an 8-h period. Animals which received a 10 mg/kg dose of unlabeled DMSA immediately before 99mTc-DMSA injection had a significantly reduced kidney accumulation and greater urinary elimination of 99mTc than animals which received the radiopharmaceutical alone. The kidney clearance was also significantly lower in rats receiving unlabeled DMSA, but no significant difference was determined between the urine clearance estimates of the two animal groups. Because the increase in the amount eliminated in the urine was not coupled with a significant change in urine clearance, it would appear that unlabeled DMSA saturated the kidney uptake mechanism(s) of 99mTc-DMSA without modifying the urinary clearance process. This interpretation is consistent with the hypothesis that renal handling of 99mTc-DMSA is governed by both glomerular filtration and peritubular capillary uptake. The simultaneous acquisition of blood, urine and non invasive image data allows for a comprehensive and informative model of the physiological disposition of 99mTc-DMSA.

Experimental obstructive hydronephrosis in newborn rats. XI. A one-year follow-up study of renal function and morphology

Partial obstruction of the left ureter was created in two-day-old rats and its effects on kidney function were studied with 99mTc-DMSA and 99mTc-DTPA after one, two, three and six weeks, and after one year. Kidneys from animals sacrificed at the age of six weeks or one year were also examined histologically. The obstructed renal pelvis was enlarged by about 35 times and there was a delayed excretion of 99mTc-DTPA during forced diuresis, indicating significant, chronic obstruction. The renal DMSA-uptake ratio (left kidney/(left and right kidney] was reduced to about 40% from the first week of obstruction. The parenchymal weight ratio (expressed as above) was reduced to about 45% after both six weeks and one year. The glomerular filtration rate, examined during forced diuresis and calculated on the basis of uptake capacity, was lowered to 42% after six weeks but was not significantly reduced after one year of obstruction. The incidence figures for medullary hemorrhage or accumulation of iron pigment, and chronic inflammatory changes in the cortex were somewhat higher after one year of obstruction than after 6 weeks, but the lesions were patchy in both groups. We conclude that partial unilateral ureteric obstruction, created in the neonatal period, leads to a slight but permanent functional disturbance and parenchymal weight reduction without prominent structural parenchymal damage.

Effect of unilateral vesicoureteric reflux on renal growth and the uptake of 99mTc DMSA by the kidney. An experimental study in the minipig

The influence of unilateral vesicoureteric reflux (VUR) on renal growth and the uptake of 99mTc DMSA by the kidney has been investigated in a 2-kidney model in the growing minipig over a period of approximately 5 months. Animals with reflux in association with low voiding pressures and normal bladder function (n = 5), as well as those with raised voiding pressures and abnormal bladder function (n = 7), were investigated with appropriate non-refluxing controls (n = 12). Urinary infection and renal scarring were avoided since these factors may affect kidney function and growth independently. Statistical tests of difference failed to demonstrate any effect of VUR on renal growth or renal uptake of 99mTc DMSA even in the presence of elevated voiding pressures and abnormal detrusor function.

Evaluation of 99mtechnetium-dimercapto-succinic acid renal scans in experimental acute pyelonephritis in piglets

We evaluated the sensitivity and specificity of 99mtechnetium-dimercapto-succinic acid renal scans in the detection and localization of experimental acute pyelonephritis in piglets. To create pyelonephritis vesicoureteral reflux of infected urine was surgically induced in 22 piglets. Nine animals were evaluated with a dimercapto-succinic acid renal scan at 1 week and 13 at 2 weeks. Autopsy and histopathological examination of the kidneys were performed subsequently. The location and extent of the inflammatory response found on histopathological examination were compared to dimercapto-succinic acid renal scan findings in a blinded fashion. Of the 22 kidneys subjected to vesicoureteral reflux 15 had positive histopathological findings of acute pyelonephritis, including 13 detected by the dimercapto-succinic acid renal scan findings. The 2 kidneys in which inflammation was not detected had only minimal grade I lesions and were grossly normal. There were no false positive scans in any of these kidneys. The sensitivity of the scan for detection of acute pyelonephritis in the kidneys subjected to reflux was 87 per cent and the specificity was 100 per cent. Furthermore, in these same kidneys the dimercapto-succinic acid renal scan findings correctly predicted the presence or absence of individual pyelonephritic lesions in 62 of 66 poles for an over-all agreement rate of 94 per cent. Thus, dimercapto-succinic acid renal cortical imaging is a highly sensitive and reliable imaging modality to detect and localize experimental acute pyelonephritis in piglets.

99mTc dimercaptosuccinic acid (DMSA) scan in patients with established radiological renal scarring

The findings on 99mTc dimercaptosuccinic acid (DMSA) scans were examined in 54 patients aged 3 to 33 years in whom renal scarring had been diagnosed radiologically in childhood after urinary tract infection. There was no recent history of infection. Vesicoureteric reflux had been present in 48 patients and had stopped in 23 at the time of the DMSA scan. In six of the 72 radiologically scarred kidneys, the DMSA scan appeared normal but scarring would have been overlooked in only two of the 54 patients. DMSA scan changes are non-specific and underestimated individual scars in 21 kidneys. The intravenous urogram and the DMSA scan showed good correlation but should be regarded as complementary investigations in these patients, giving morphological and functional information, respectively. On DMSA scans the timing of any preceding urinary tract infection must be considered in order to differentiate diffuse potentially reversible defects in isotope uptake after urinary tract infection from those due to permanent renal scarring.

Technetium-99m dimercaptosuccinic acid uptake in long-term catheterized kidney. Comparison with renal function

We studied 23 long-term catheterized kidneys in 14 patients. The uptake of 99mtechnetium dimercaptosuccinic acid (99mTc-DMSA) was measured at one- and two-hour intervals after injection, and the uptake was corrected for variations in renal depth. These values were compared with inulin, creatinine, and para-amino hippurate (PAH) clearances which were measured in each kidney by collecting urine through long-term catheterization. Correlation coefficient was obtained between PAH clearance corrected for the body surface area and the two-hour uptake of 99mTc-DMSA. The correlation coefficients between the two-hour uptake of 99mTc-DMSA and the clearance values are not significantly different from those between the one-hour uptake and the clearance values. Corrections of the uptake for variations in renal depth did not improve the correlation coefficients. The results show that 99mTc-DMSA is an excellent method to estimate the renal plasma flow and the one-hour uptake without correction for renal depth is clinically sufficient to evaluate the split renal function.

Unilateral kidney irradiation and late retreatment with cis-dichlorodiammineplatinum (II): functional measurements with 99mtechnetium-dimercaptosuccinic acid

A rat model was used to study renal function after unilateral kidney irradiations. The left kidney was irradiated with a single dose (6-14 Gy), 2 equal sized fractions (10-16 Gy total dose) or 4 equal sized fractions (12 to 21 Gy total dose). At regular time intervals after treatment, the left kidney function was assessed with the use of 99mTc-Dimercaptosuccinic acid for a period of about 1 year. It was found that renal function declined in a dose- and time-dependent manner. The threshold dose for detecting functional impairment was 8 Gy for 1 fraction, 12 Gy for 2 fraction and 15 Gy for 4 fraction irradiations, demonstrating the sensitivity of the isotope tracer test used in these experiments. Retreatment of the rats with a single i.p. dose of 5 mg/kg cis-Dichlorodiammineplatinum (II) (cis-DDP) given at about 1 year after X ray exposure revealed an important relative decrease in the function of the irradiated compared to the unirradiated kidney. Reductions in function of 11 to 70% (depending on radiation dose and schedule) compared with control values were observed at 11 weeks after drug injection. These results demonstrate that a previously irradiated kidney is more sensitive to a subsequent treatment with cis-DDP than the contralateral hypertrophied kidney in the same animal.

Renal scarring secondary to vesicoureteric reflux. Critical assessment and new grading

One hundred and fifty children with proven urinary tract infection who were assessed by renal ultrasound (U/S), intravenous urography (IVU) and dimercaptosuccinic acid (99mTc DMSA) scan, were studied to identify the sensitivity of each examination and the pick-up rate of renal scarring secondary to vesicoureteric reflux. Sixty-three of these children who had the examinations carried out within a 6-month period were assessed in detail. A DMSA scan is the most accurate method of detecting early renal scars in the young age group (0-2 and 2-5 years), followed by ultrasound. The examinations are equally sensitive over the age of 5. A new grading system of the severity of renal scarring is presented.

The importance of using anterior and posterior views in the calculation of differential renal function using 99Tcm-DMSA

Radionuclide techniques for determining relative renal function are well established. One simple method uses the count rate from static images obtained using 99Tcm-dimercaptosuccinic acid (DMSA). We have reviewed 277 DMSA scans and shown that it is important to obtain the geometric mean of counts from the anterior and posterior views in order to correct for the different amounts of attenuation for each kidney. If counts were obtained from the posterior view only, erroneous results would be obtained in 8% of children under 13 years, in 28% of patients aged between 13 and 20 years and in 32% of patients over 20 years of age.

Imaging the kidneys and urinary tract in the neonate with acute renal failure

Transitional nephrology seriously affects the manner in which radiological investigations and other forms of imaging are undertaken in the neonate. When this is complicated by acute renal failure then caution must be exerted in taking care of the neonate. The use of ultrasound and micturating cystourethrography are well described and form the baseline for all imaging of the renal tract. The physiological handling of TC99m DTPA and the contrasts used for IVU are described as well as the normal appearances of these techniques in the neonate. TC99m DMSA is also included, as are other modalities of imaging.

Indications for 99mtechnetium dimercapto-succinic acid scan in children

The 99mtechnetium dimercapto-succinic acid scan provides an image of functional renal parenchyma. This static scan has specific indications and cannot be used simply in place of a 99mtechnetium diethylenetriaminepentaacetic acid scan. The major clinical indications for this investigation are the detection and/or evaluation of a renal scar, the small or absent kidney, an occult duplex system, certain renal masses, systemic hypertension or suspected vasculitis. The physiology of the 99mtechnetium dimercapto-succinic acid scan is reviewed briefly.

Evaluation of renal parenchyma in children by DMSA scintigraphy, X-ray computed tomography and intravenous urography

The demonstration of diminished or scarred renal parenchyma in children is often the decisive factor in determining the future management of children with urinary tract malformations. Renal scintigraphy using technetium 99m-labelled dimercaptosuccinic acid (DMSA), computed tomography (CT) and intravenous urography (IU) were used to evaluate the renal parenchyma prior to ureter re-implantation in a series of 13 children. Their ages ranged from 5 months to 3 years 8 months. The indication for operation was ureteric reflux in 8 children and distal ureteric stenosis in 5. CT was performed on a Toshiba TCT-80 scanner. Renal scintigraphy was performed 3 hours after intravenous injection of DMSA. Compared with IU, DMSA imaging gave more information about the renal parenchyma in 6 children, gave equal information in 6 and less in 1. Compared with CT, DMSA imaging gave more information in 2 children, was equally informative in 8 and less so in 3. Accordingly, DMSA imaging was judged to be more sensitive than IU and as sensitive as CT. DMSA imaging can be used both for the initial evaluation and for follow-up assessment of renal parenchymal damage.

Multiple-section radionuclide tomography of the kidney: a clinical evaluation

The clinical utility of radionuclide emission tomography of the kidney in comparison with conventional gamma-camera imaging has been assessed from scans of 60 patients suspected of having space-occupying lesions of the kidney. Nineteen patients had renal tumour, 17 had cysts and seven had renal pseudotumours; the remainder had no lesion. Objective trials using four observers showed only a slight, statistically insignificant advantage from the addition of tomographic sections to conventional images. However, in several individual cases tomography had aided diagnosis, particularly in obese patients, when an alternative non-invasive investigation (ultrasonography) was inconclusive. In seven patients a positive diagnosis of renal pseudotumour was made possible by tomography; definite identification of ectopic functioning cortical tissue at the location of a mass suspected after urography was considered to be a distinct diagnostic advantage gained from emission tomography of the kidney.

Combined [99mTc]DMSA kidney scintigraphy and [131I]hippuran renography in children with urinary tract infections

Combined [99mTc]DMSA kidney scintigraphy and [131I]hippuran renography were performed consecutively in 87 children with recurrent urinary tract infections in a retrospective study. This procedure allows a description of renal cortical morphology, split function determination and run-off evaluation. Signs of cortical scarring were found in 41 of 172 kidneys (24%) and were significantly associated with vesico-ureteral reflux (p less than 0.001) and with delayed urinary run-off (p less than 0.01). Split renal function was significantly reduced in kidneys with unilateral scarring (p less than 0.001). The radio-isotope investigations and intravenous urography were performed within 3 months of each other in 56 patients (110 kidneys). Good agreement between the findings was found except for 13 kidneys, where cortical activity defects were revealed by scintiscan despite normal urography. The extended scintigraphic procedure described is considered useful for urological screening of children with urinary tract infections and may thus replace urography as a first-line investigation. It should be followed by micturition cysto-urethrography when evaluation for vesico-ureteral reflux is indicated.

A clinical study of 99mTechnetium dimercaptosuccinic acid uptake in obstructed kidneys: comparison with the creatinine clearance

We studied 17 hydronephrotic kidneys owing to stenosis of the pyeloureteral junction. Preoperative uptake of 99mtechnetium dimercaptosuccinic acid was compared to early postoperative unilateral creatinine clearance, measured by urine collection from the nephrostomy tube. An excellent correlation was found. Therefore, uptake of 99mtechnetium dimercaptosuccinic acid represents a reliable parameter of renal function even in the presence of severe urinary tract obstruction. However, 99mtechnetium dimercaptosuccinic acid uptake should be measured more than 24 hours after injection of the tracer.

Renal radiopharmaceuticals--an update

Noninvasive radionuclide procedures in the evaluation of renal disease have been accepted increasingly as effective and valuable alternatives to older clinical methods. The development of suitable radiopharmaceuticals labeled with high photon intensity radionuclides and with 99mTc in particular has stimulated this modality during the last few years. Currently several nearly ideal agents are available for anatomical and functional studies of kidney imparting very low absorbed radiation doses. These include 99mTc-GHA and 99mTc-DMSA for renal morphology and differential function evaluation, 99mTc-DTPA for GFR and 123I orthoiodohippurate for ERPF measurements. A suitable agent as a replacement for the latter labeled with 99mTc is actively being sought. Computer-assisted processing of dynamic renal function studies enables the observer to obtain a wealth of information related to the renal extraction, uptake, parenchymal transit and pelvic transit parameters of the agent administered into the bloodstream. Each of these parameters either globally or differentially contributes to a detailed evaluation of renal disease states. Several of these procedures have been validated against classical techniques clinically but more detailed information is being sought with the recently introduced radiopharmaceuticals. With the detailed validation and increasing recognition of the clinical utility of several of the radionuclidic procedures at many centers, it is hoped that radionuclide assessment of renal disorders ultimately will be made available routinely at all medical facilities.

Quantitative measurement of activity in small sources containing medium energy radionuclide: comparison of the gamma camera and the rectilinear scanner

The response of a gamma camera and a rectilinear scanner to small sources containing 131I was assessed from the point of view of thier suitability for measuring the activity of a source, as opposed to their capacity to produce well-resolved images. The influence of the size of the area over which counts were integrated, and of the size and depth of hte source, were investigated for both instruments. The results indicate that both instruments are dependent on these variables, though with the particular instruments investigated the dependence of the gamma camera is much more complex and difficult to define. The conclusions indicate that with these systems quantitative activity measurements are more readily achievable with the scanner than with the camera.

Endarterial urokinase in childhood hemolytic uremic syndrome

Urokinase was given by unilateral infusion for 48-168 hours into the renal arteries of 8 children (0.2 to 13.0 years) with acute renal failure and impaired renal perfusion due to hemolytic uremic syndrome (HUS). Two children subsequently received a bilateral infusion. Immediate changes in renal perfusion were assessed by serial dynamic renal scanning in all patients and by repeat renal arteriography in 5. No improvement clearly attributable to urokinase was observed. In 4 surviving children assessment of divided renal function by static renal scanning 1 to 5 years after presentation showed no evidence of benefit from urokinase. Examination of the kidneys of 2 of the 3 children who died, and one who underwent bilateral nephrectomy prior to renal transplantation, showed no evidence of benefit from urokinase. Examination of the kidneys of 2 of the 3 children who died, and one who underwent bilateral nephrectomy prior to renal transplantation, showed no preservation of renal mass attributable to urokinase; in one of these children the infused kidney was considerably smaller than the untreated kidney. It is concluded that local infusion of urokinase had no beneficial effect on the course of HUS in these children.

Renal scintigraphy: quantitative assessment of upper urinary tract dilatation in children

A standard method of Tc-DTPA renal scintigraphy has been used to examine 426 dilated upper urinary tracts in children aged 2 days-16 yr. The method provides an accurate estimate of individual kidney function and defines the extent of dilatation. Renogram analysis and frusemide-induced diuresis have been applied in an attempt to distinguish between the obstructed upper tract and the dilated upper tract without obstruction. In 304 upper tracts, obstruction was predicted with an overall sensitivity of 0.87. The sensitivity for diagnosis of pelviureteric junction obstruction was 0.93. The value of scintigraphy in excluding significant obstruction and in follow-up studies is emphasized. This is a noninvasive, low-radiation investigation which plays an important role in the assessment of obstructive uropathy in childhood and represents a major advance in diagnostic facilities.

Ureteric ectopy in children

Twenty-eight cases of ectopic ureters are reviewed. Two groups consisting of single ectopic ureters and ectopia associated with duplex systems are considered. The former is associated with a high incidence of congenital anomalies. A dilated ectopic ureter remains completely extravesical but can produce features closely resembling those of an ectopic ureterocele. The use of 99mTc-DMSA renal scan has proved helpful in the diagnosis of the condition because it can demonstrate the existence of a poorly functioning kidney not evident on excretion urography.

Kidney scintigraphy with 99mTc-DMSA and 131I-hippurate

43 patients underwent an extended scintigraphic procedure with 99mTc-dimercaptosuccinylic acid in order to investigate its proper use for diagnosing morphological and functional kidney abnormalities. The group was comprised of patients without renal disease, and patients with diffuse parenchymal disease, obstructive uropathy, renal cysts and renal tumors. The study was followed by 131I-hippurate renography. We propose a simplified routine procedure with scintiphotos taken 10-15 min after injection for topographic information and 120 min after injection for renal morphology. This procedure allows excellent case finding of diffuse parenchymal disease of a special value in cases of radiological non-visualization. The technique is indicated, when iodine contrast media cannot be used for radiological examinations. DMSA studies, however, do not allow safe functional evaluation in all categories of patients. Neither can obstructive nephropathy be diagnosed unless the renal pelvis is dilated. Renal perfusion studies are contaminated by the perfusion of liver and spleen. Nevertheless, a tentative differentiation between cysts and tumours is possible, the former being hypoperfused the latter hyperperfused. When supplemented with gamma camera 131I-hippurate renography, the total scintigraphic procedure will also include split function determination and run-off evaluation.