Renal cortical scintigraphy in the diagnosis of acute pyelonephritis

A case of ureteral reflux identified by ultrasound

Reflux nephropathy is known to be a major cause of renal failure in children. Vesico-ureteral reflux is usually diagnosed by voiding cysto-urethrography (VCG). However, it has been observed that conventional VCG is not always reliable for the diagnosis of ureteral reflux. In the case of a 5 year old girl with recurrent febrile urinary tract infection, VCG showed no ureteral reflux. Urodynamic study revealed a large bladder capacity and significant residual urine. Renal scintigram delineated a right renal scar. Simple ultrasound examination with videotape recording during voiding definitely demonstrated the presence of significant ureteral reflux when she voided, that is, there was marked dilatation of the right distal ureter and ballooning of the right renal pelvis on voiding, and quick refilling of the bladder concomitantly with the disappearance of the pelvic ballooning. Therefore, an ultrasound during voiding may be useful for diagnosing ureteral reflux in patients where a VCG does not reveal reflux.

Febrile urinary tract infection in children: Role of 99MTc-dimercaptosuccinic acid (DMSA) scan and other imaging techniques

Fifty children (37 females and 13 males) with first febrile urinary tract infections were studied to assess the value of 99MTc-dimercaptosuccinic acid (DMSA) scan in detecting inflammatory changes of acute pyelonephritis (APN). These findings were compared with renal ultrasonography (US). We also evaluated the reliability of clinical and laboratory observations in diagnosing acute pyelonephritis (APN). All children had micturating cystourethrography (MCUG). DMSA-documented acute pyelonephritis was present in 29 (58%) patients. Only four children (8%) demonstrated changes suggestive of APN on renal ultrasonography. Vesicoureteric reflux (VUR) was documented in 17 (47%) of the total group and in 13 (45%) of those with abnormal DMSA scan. Follow-up DMSA scan in 15 children with initial abnormal findings showed complete recovery in seven (47%). Our data have shown that DMSA renal scan is the most useful investigational procedure in children with febrile UTI. The diagnosis of APN, depending on clinical and laboratory data, is unreliable. Renal US alone can miss serious renal defects. MCUG remains the most sensitive procedure to detect VUR and it should be performed in all children with UTI and abbormal DMSA scan. Early detection of acute pyelonephritis allows the prompt introduction of antimicrobial agents in those children and can prevent or decrease renal damage and its complications.

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.

Where are we with nuclear medicine in pediatrics?

The practice of nuclear medicine in children is different from that in adults. Technical considerations including immobilization, dosing of radiopharmaceuticals, and instrumentation are of major importance. Image magnification and the capability to perform single-photon emission tomography are essential to performing state of the art pediatric nuclear medicine. New advances in instrumentation with multiple detector imaging, the possibility of clinical positron emission tomography imaging in children, and new radiopharmaceuticals will further enhance pediatric scintigraphic imaging. This review highlights advances in pediatric nuclear medicine and discusses selected clinical problems.

Contradictory supranormal nuclear renographic differential renal function: fact or artifact?

We previously reported contradictory supranormal nuclear renographic differential renal function in cases of unilateral hydroureteronephrosis, in which the kidneys with hydroureteronephrosis paradoxically had a greater differential function than the contralateral normal mate, based on diethylenetriaminepentaacetic acid (DTPA) nuclear renography. To evaluate whether DTPA supranormal differential function represented true hyperfunction, patients with DTPA supranormal differential function were evaluated with dimercaptosuccinic acid (DMSA) nuclear renography and the results were compared. A total of 16 patients with unilateral hydronephrosis was identified to have DTPA differential function of 53% or more. They were younger than age 1 year and had never undergone any urological surgery. In all 16 patients the DMSA differential function (mean 51.1%, range 42 to 57%) was lower than their own corresponding DTPA differential function (mean 58.3%, range 53 to 66%, p < 0.0001). In addition, the DMSA differential function was not significantly different from the intuitively anticipated mean of 50% (p = 0.48). The DTPA supranormal differential function identified in our patients was not corroborated by the DMSA differential function. With recent evidence that DMSA differential function may be a better predictor of outcome following relief of unilateral ureteral obstruction consideration should be given to using DMSA as a potentially more relevant method for differential function measurement in the setting of unilateral hydronephrosis. Conversely, until the potential deficiencies of DTPA are fully understood caution should be exercised in the interpretation of DTPA differential function in the setting of hydronephrosis.

Update on dimercaptosuccinic acid renal scanning in children with urinary tract infection

The dimercaptosuccinic acid (DMSA) renal scan is a method for assessing kidney function. Indications for DMSA scanning in children with urinary tract infection (UTI), as well as timing, have changed. Pitfalls in interpreting DMSA scans include: (1) acute pyelonephritis (APN), (2) tubular dysfunction, (3) hypertension, (4) use of captopril in patients with renovascular hypertension and (5) duplex kidneys. Interpretation of DMSA scans in children with UTI vary according to timing and clinical setting. During the course of a febrile UTI a DMSA scan may reveal a normal kidney, APN or a non-functioning, small and/or ectopic kidney. In the absence of UTI (up to 6 months) in children with vesicoureteric reflux a DMSA scan may indicate a normal kidney, renal scarring (reflux nephropathy), occult duplex kidney and allows the progression of scarring and hypertrophy of normal areas of the kidney to be followed anatomically. The DMSA renal scan in now the most reliable test for the diagnosis of APN. The transient abnormalities due to APN can occur in normal or scarred kidneys. Lesions due to reflux nephropathy (defined as a defect in the renal outline or contraction of the whole kidney) are permanent. Intravenous urography reveals renal abnormalities later than the DMSA scan. If abnormalities are seen on a DMSA scan performed during the course of APN it is impossible to predict the outcome: they can progress to permanent scarring or heal completely. An abnormal DMSA scan during a febrile UTI allows the identification of children at risk of developing renal scars. These children should be carefully investigated, maintained on long-term quimioprophylaxis and followed.

Tc-99m dimercaptosuccinic acid(DMSA) renal scintigraphy in patients with acute pyelonephritis

OBJECTIVES

Recently, several authors reported that Tc-99m DMSA renal scan frequently showed cortical defects of the involved kidneys even in the patients with acute pyelonephritis who did not show abnormal findings in the ultrasonography and intravenous pyelography (IVP).

METHODS

In order to evaluate the utilities of Tc-99m DMSA renal scan and the clinical meaning of cortical defects in the Tc-99m DMSA renal scan of the patients with acute pyelonephritis, ninety two patients with acute pyelonephritis, from March 1991 to February 1994 in Chungnam National University Hospital(CNUH), were included in this study. Patients were subdivided as Group A:Patients showing normal Tc-99m DMSA renal scan (n = 42) and Group B:Patients with definite cortical defects on the Tc-99m DMSA renal scan (n = 50). We compared clinical characteristics such as age and sex, recurrency, duration of fever, bacterial culture study, incidence of renal insufficiency and the results of renal ultrasonography and intravenous pyelography between the two groups.

RESULTS

Fifty four percents of 92 patients with acute pyelonephritis showed a significantly longer febrile period after admission, higher positive rates on the urine and blood culture studies and higher incidence of renal insufficiency than those of the Group A patients. Sixty nine percents of Group B patients showed normal results in ultrasonography or IVP study.

CONCLUSIONS

Tc-99m DMSA renal scan was a more sensitive imaging test than ultrasonography in kidneys and IVP to detect pyelonephritis lesions and may be useful to predict the patient group with a severe disease course. These patients may need more careful management and further studies to evaluate the possibility of complications.

Renal pathology and the 99mTc-DMSA image before and after treatment of the evolving pyelonephritic scar: an experimental study

This study reports the effects of 3-weeks' antimicrobial treatment on the pathology and appearance of the 99mTc-DMSA renal image in piglets with pyelonephritis induced by a combination of vesicoureteral reflux (VUR) and urinary infection. Before treatment, either photon-deficient (B1, B2) or photon-absent (C) scintigraphic abnormalities were present in the refluxing kidney in all 22 animals examined. All (100%) of the initially B1 and the majority (71%) of B2 photon deficient defects resolved with treatment, leaving only insignificant residual pathologic lesions. Conversely almost all (93%) of the C photon-absent scintigraphic abnormalities persisted after treatment and were always associated with significant scarred or cratered pathologic lesions in the refluxing kidney at sacrifice.

The selective use of dimercaptosuccinic acid renal scans in children with vesicoureteral reflux

Dimercaptosuccinic acid (DMSA) renal scans were performed on 75 children (115 refluxing renal units) to determine the efficacy of routine scanning in patients with various grades of vesicoureteral reflux. Cystourethrography demonstrated grades I and II reflux in 75 renal units and grades III to V in 40. Of the patients 51 presented with febrile urinary tract infection and 24 were asymptomatic (patients presenting with nonfebrile urinary tract infections or those undergoing sibling screening). Renal ultrasounds were performed in 60 patients. All patients were initially managed with medical therapy and 19 (25%) ultimately underwent antireflux surgery. DMSA scans demonstrated scarring in 17 of 40 renal units (43%) of patients with high grade vesicoureteral reflux and 6 of 75 renal units (8%) of those with low grade reflux. Renal ultrasounds that were interpreted as normal always correlated to a normal DMSA scan in asymptomatic patients. In patients presenting with febrile urinary tract infections the correlation between ultrasound and DMSA scan was inconsistent. We advocate a tailored approach in the evaluation of patients with vesicoureteral reflux. Renal sonography may be sufficient in the assessment of renal scarring in asymptomatic patients with reflux and those with low grade reflux. Conversely, in patients with high grade vesicoureteral reflux, a history of febrile urinary tract infections and abnormal renal ultrasound DMSA renal scans appear to be most useful.

Correlative imaging of the kidney

The proliferation of imaging methods for the kidney and urinary tract, combined with advances in technology and the introduction of new techniques, has created uncertainty in selecting the most efficient method for evaluating many problems encountered in clinical medicine. The main advantage of nuclear medicine lies in demonstrating the pathophysiology involved. Recent developments in Doppler ultrasound and magnetic resonance imaging with different pulse sequences and paramagnetic contrast agents also have shown promise for imaging physiological processes. However, there is little literature to support their advantage over nuclear medicine procedures in many common clinical situations. The complementary nature of nuclear medicine studies in the imaging evaluation of hydronephrosis, renal artery stenosis, flank pain, renal mass, pyelonephritis, and the transplant kidney is reviewed.

The significance of vesicoureteric reflux on kidney development assessed by dimercaptosuccinate renal scintigraphy

OBJECTIVE

To study the influence of vesicoureteric reflux on kidney parenchyma and renal length, and identify typical distribution patterns by dimercaptosuccinate (DMSA) renal scintigraphy.

PATIENTS AND METHODS

DMSA renal scintigraphies in 101 children (152 renal units) with vesicoureteric reflux grade 1-5 were reviewed.

RESULTS

Three main types of pathological DMSA patterns were found: (i) dysplasia; (ii) medial defect; and (iii) pole defects. In children with no history of pyelonephritis a normal distribution pattern was found in 31%, dysplasia in 23%, medial defect in 25%, pole defects in 17% and no typical pattern in 4%. In those with a history of pyelonephritis a normal distribution pattern was found in 28%, dysplasia in 24%, medial defect in 21%, pole defects in 24% and no typical pattern in 3%. A normal pattern was significantly more frequent in kidneys with reflux grade 1-2. Dysplasia was significantly more frequent in kidneys with reflux grade 4-5. In children with no history of pyelonephritis 42% of the renal units had reduced length, 8% with no other sign of pathology. The frequency of reduced kidney length at reflux grade 1-2 did not differ significantly from that at higher grades of reflux. In children with a history of pyelonephritis 52% of the renal units had reduced length, 13% with no other sign of pathology. The frequency of reduced kidney length with a normal DMSA pattern did not differ significantly from that with a pathological pattern.

CONCLUSION

The pathological DMSA distribution with vesicoureteric reflux generally conforms to one of three main patterns. Reduced kidney length is frequent even at lower grades of vesicoureteric reflux even in patients with no history of pyelonephritis, and can be the only sign of pathology.

Renal scarring after acute pyelonephritis

Seventy six children, 18 boys and 58 girls, aged 0-15.9 (median 1.0) years, with acute pyelonephritis were prospectively studied with a technetium-99m dimercaptosuccinic acid (DMSA) scan during infection and two months later. Fifty nine of these children were also studied two years after the infection. Seventeen children with a normal DMSA scan during infection or at two months after infection, or both, were not investigated by a DMSA scan at two years after acute pyelonephritis. A micturition cystourethrogram was performed in all the children after two months. Changes on the DMSA scan were found in 65 (86%) children during acute pyelonephritis, in 45 (59%) children at two months, and in 28 (37%) children at two years after infection. Vesicoureteric reflux (VUR) was found in 19 (25%) children at two months. Renal scarring was significantly correlated with the presence of gross VUR and recurrent pyelonephritis, but 62% of the scarred kidneys were drained by non-refluxing ureters. Children with scars were older at the time of acute pyelonephritis than those without scars but no difference was found between the groups with regard to duration of illness, levels of C reactive protein and maximum white cell count, glomerular filtration rate, nor renal concentration capacity at the time of infection. It is concluded that renal scarring after acute pyelonephritis in children is more common than has been previously thought. Although children with gross VUR and recurrent pyelonephritis are at the greatest risk, renal scarring is more often seen without these risk factors.

Cortical scintigraphy in the evaluation of renal parenchymal changes in children with pyelonephritis

We designed a prospective study to evaluate the ability of dimercaptosuccinic acid cortical scintigraphy and ultrasonography to detect renal parenchymal lesions in children with pyelonephritis. One hundred eleven patients 1 week to 16 years of age (median 5.5 months) with a urine culture positive for pathogens were included in the study; cortical scintigraphy and ultrasonography were repeated in 25 children after a mean follow-up of 10.5 months. Cortical scintigraphy showed renal changes in 74 children (67%), and ultrasonography showed renal changes in 39 (35%) (p < 0.001); results of the two examinations were discordant in 49 patients (kappa = 0.19). Children more than 1 year of age had a higher incidence of renal lesions than did younger children (85% vs 66%; p = 0.04). The presence of inflammatory signs (erythrocyte sedimentation rate or C-reactive protein) had an 89% sensitivity and a 25% specificity in identifying renal lesions. Among children with renal changes, vesicoureteric reflux was present in 39%. At follow-up examination, 16 children (64%) had scars. Thus we found a high incidence of renal involvement in children with pyelonephritis. We found that cortical scintigraphy is more sensitive than ultrasonography in detecting renal changes, and we believe that it should be added to the initial examination of children with suspected pyelonephritis.

Typical technetium dimercaptosuccinic acid distribution patterns in acute pyelonephritis

Technetium dimercaptosuccinic acid renal scintiscans in 37 children with clinical diagnosis of acute pyelonephritis were reviewed. In 18 children, follow-up scintigraphy was obtained after an interval ranging from 5 to 8 months. Uptake abnormalities were found in 89% of the children (74% of the kidneys). We were able to identify four typical pathological uptake patterns: (i) pole defect(s), usually wedge shaped (60%); (ii) lateral wedge shaped defect (4%); (ii) scattered multiple defects (21%); and (iv) swollen kidney without areas of diminished uptake (15%). Remaining pathology at follow-up was found in 52% of the kidneys. Vesicoureteric reflux was present in 33% of the children with scintigraphic signs of pyelonephritis. Frequencies of parenchymal changes in the acute phase and at follow-up were not significantly correlated to the presence of reflux.

Intra- and interobserver variability in interpretation of DMSA scans using a set of standardized criteria

A set of criteria was developed to standardize assessment of DMSA renal scintigraphy which were performed to evaluate children for acute pyelonephritis and renal scarring. This study was undertaken to assess intra- and interobserver variability in the interpretation of DMSA renal scintigraphy using these criteria. Renal contours and parenchyma were assessed in three zones. Contours were assessed as normal or abnormal and parenchymal defects were evaluated in terms of character, shape and degree in three regions (upper and lower pole and midzone). Two nuclear medicine physicians blindly reviewed 57 DMSA scintigraphy on two occasions each. Disagreement of each observer's evaluation of the same scintigraphy on two different occasions was described as intraobserver variability, and the comparison between readings by each of the two observers was described as interobserver variability. High levels of intra- (95.9% and 90.6% respectively, p < 0.05) and interobserver agreement (84.4%, p < 0.05) were demonstrated. There were minor differences in inconsistencies between the two kidneys or different kidney zones. We conclude that standardization of criteria resulted in higher intra- and interobserver consistency in interpretation of DMSA scintigraphy.