CT evaluation of severe renal inflammatory disease in children

99mTc-dimercaptosuccinic acid scan versus MRI in pyelonephritis: a meta-analysis

PURPOSE

Tc-dimercaptosuccinic acid (DMSA) scan is the current gold standard in detecting parenchymal changes, particularly scarring, in pyelonephritis. Recently, magnetic resonance imaging (MRI) is gaining popularity in the diagnosis of pyelonephritis. The aim of this study is to perform a meta-analysis on studies directly comparing MRI to DMSA scan in patients with pyelonephritis.

MATERIALS

Systematic searches of PUBMED and EMBASE databases were performed to extract studies comparing MRI and DMSA scan in patients with pyelonephritis. The relevance of articles was assessed by two authors according to predefined inclusion and exclusion criteria. The pooled estimates of the sensitivities of MRI and DMSA scan were computed using random-effects meta-analysis model following DerSimonian and Laird's method. Subgroup analysis and publication bias were performed.

RESULTS

Seven studies were included (164 patients). Using random effect model, the pooled estimate of the sensitivities of MRI and DMSA scan were 0.62 (95%CI: 0.44 - 0.77) and 0.59 (95%CI: 0.48 - 0.70), respectively. The pooled estimates of sensitivities of MRI and DMSA scan for acute pyelonephritis were 0.73 (95%CI: 0.49- 0.89) and 0.66 (95%CI: 0.56 - 0.75), respectively, and for scar detection were 0.48 (95%CI: 0.31- 0.66), and 0.50 (95%CI: 0.30 - 0.71), respectively.

CONCLUSION

The overall sensitivities of MRI and DMSA scan were equivalent in detecting parenchymal changes in pyelonephritis. MRI and DMSA scan appeared to be equivalent to scar detection. In a small number of studies, MRI appeared to be better than the DMSA scan in acute pyelonephritis but this should be further studied in a larger number of patients.

[Initial imaging in pediatric urinary tract infection]

First step imaging investigations in urinary tract infections in children rely upon conventional sonography, and, when available. Power Doppler sonography. Enhanced computerised tomography (CT) and dimercaptosuccinic acid (DMSA) scintigraphy are complementary investigations in difficult cases. Contrast cystourethrogram has always to be performed. Intravenous pyelography is no longer used as a first step imaging technique.

The role of power Doppler ultrasonography in the diagnosis of acute pyelonephritis

OBJECTIVE

To assess the ability of power Doppler ultrasonography (PDU) to detect acute pyelonephritis and to compare the findings from PDU with those from enhanced computed tomography (CT).

PATIENTS AND METHODS

Eleven patients (mean age 18.5 years, range 5-37) admitted to hospital with a clinical diagnosis of pyelonephritis were assessed with PDU and enhanced CT. the latter providing the reference method.

RESULTS

The imaging studies showed normal findings in three patients; a single focus of pyelonephritis was detected by CT in six, whereas a matching defect was detected on PDU in five, with PDU failing to detect an infective focus in one. Multifocal diffuse pyelonephritis was diagnosed correctly by enhanced CT and PDU in two patients.

CONCLUSION

Power Doppler ultrasonography had an overall sensitivity of 88% and complete specificity in the evaluation of patients with acute pyelonephritis.

[Contribution of vascular ultrasonic studies for the study of kidney diseases in children. Société francophone de recherche en pédiatrie]

The proximity of child's kidneys from the cutaneous surface allows a particularly sensitive exploration by doppler sonography, which in addition has the major advantage of being a non-invasive, non-irradiating and painless technique. However there are two limitations to this technique: the lack of cooperation of some children and the still limited availability of high quality equipment in intensive care units. Indeed most of the applications described in this paper (i.e., pyelonephritis, renovascular hypertension, tumors, acute renal insufficiency and renal vein thrombosis) require, besides an experienced operator, expensive power doppler equipment including high frequency and high resolution probes.

Scintigraphic evaluation of pediatric urinary tract infection

Scintigraphic evaluation of urinary tract infection, pyelonephritis, and renal scarring represents a significant portion of a clinical pediatric nuclear medicine practice. Renal scarring from recurring infection remains an important cause of end-stage renal disease and hypertension in the pediatric population. However, the clinical presentation in infants and young children is often elusive, and clinical diagnosis of upper tract involvement is frequently unreliable. As a result, diagnostic imaging has a critical role to play in the localization of infection to the lower or upper urinary tract. Radionuclide cystography and renal cortical imaging have become mainstays of this evaluation. Direct radionuclide cystography is the preferred cystographic screening technique, because it has lower radiation exposure and greater sensitivity for the detection of vesicoureteral reflux than either indirect radionuclide cystography or fluoroscopic contrast cystography. Renal cortical scintigraphy has become the standard for the detection of pyelonephritis and renal scarring. Correlation with histopathology has demonstrated a high degree of diagnostic accuracy. Acute pyelonephritis has been shown to be the necessary etiologic factor for the development of subsequent renal scarring, and the mechanism of renal injury in pyelonephritis has been extensively studied in experimental models. The ability of prompt and appropriate antibiotic therapy to dramatically reduce the incidence of subsequent scarring also has been conclusively demonstrated both clinically and in the experimental model. Vesicoureteral reflux was once thought to be a necessary prerequisite for the development of renal scarring. Although it is clear that the intrarenal reflux of infected urine will create pyelonephritis in the experimental model, the high incidence of pyelonephritis and subsequent scarring in the absence of demonstrable vesicoureteral reflux leaves the role of reflux in question. Although the role of vesicoureteral reflux is incompletely understood, its detection nevertheless remains a standard part of the patient's evaluation.

Rational use of CT in acute pyelonephritis: findings and relationships with reflux

Enhanced renal CT scanners were performed in 38 children (82% girls) to rule out acute pyelonephritis. Patients were divided in 2 groups on the basis of clinical presentation and bacteriology data. In patients of group A (n = 16, preliminary study), upper urinary tract infection (UTI) was certain. CT confirmed the diagnosis in all but 3 patients (a 2-year-old child and 2 patients with UTI developed on prior obstruction). In subsequently studied patients of group B (n = 22), clinical findings or bacteriology data were negative or questionable. CT made the diagnosis of acute pyelonephritis in 11 patients. As well as DMSA scintigraphy, CT scanner can help to diagnose or to rule out upper UTIs in difficult cases. In all boys of both groups, ipsilateral vesico-ureteric reflux (VUR) was found by subsequent voiding cystourethrography (VCUG) on the side of pyelonephritis. In girls, this correlation was shown in only 7 of the 25 kidneys with pyelonephritis. This result supports the hypothesis of a gender-dependent contamination. We believe that absence of radiologic reflux cannot exclude the possibility of bacterial crossings of ureteric meatus capable to lead to genuine upper UTIs.

Renal cortical scintigraphy in the diagnosis of acute pyelonephritis

Comparative clinical studies have shown renal cortical scintigraphy, using technetium-99m (99mTc)-labeled glucoheptonate or dimercaptosuccinic acid (DMSA), to be significantly more sensitive than either intravenous pyelography or renal sonography in the diagnosis of acute pyelonephritis. However, due to uncertainties about the diagnostic accuracy of the clinical and laboratory parameters used in these studies, true sensitivity of renal cortical scintigraphy was unknown. Therefore, we evaluated the accuracy of [99mTc]DMSA scintigraphy in the diagnosis of experimentally induced acute pyelonephritis in piglets using strict histopathologic criteria as the standard of reference. The sensitivity and specificity of the DMSA scan for the diagnosis of acute pyelonephritis were 91% and 99%, respectively, with an overall 97% agreement between the scintigraphic and histopathologic findings. Based on the results of this experimental study, we used the [99mTc]DMSA scan as the standard of reference for the diagnosis of acute pyelonephritis, and conducted a prospective clinical study of 94 children hospitalized with the diagnosis of acute febrile urinary tract infection (UTI). The aims of this study were (1) to determine the relationship among vesicoureteral reflux, P-fimbriated Escherichia coli, acute pyelonephritis, and renal scarring, and (2) to evaluate the diagnostic reliability of the clinical and laboratory parameters commonly used in the diagnosis of acute pyelonephritis. We documented acute pyelonephritis in 62 (66%) of 94 patients. Vesicoureteral reflux was demonstrated in 29 (31%) of the total group and in only 23 (37%) of 62 patients with acute pyelonephritis. The prevalence of P-fimbriae in the E coli isolates was 64% in the patients with acute pyelonephritis and 78% in those with a normal DMSA scan. Even in patients without reflux, P-fimbriae were found in 71% of isolates from the patients with acute pyelonephritis and in 75% of those with a normal renal scan. Follow-up DMSA scans were obtained in 33 patients with acute pyelonephritis in 38 kidneys. We found complete resolution of the acute inflammatory changes in 58% of the involved kidneys and renal scarring in the remaining 42%, including 40% of the kidneys associated with reflux and 43% of those without reflux.(ABSTRACT TRUNCATED AT 400 WORDS)

Color Doppler sonography in pyelonephritis

Renal sonography detects abnormality in only 40% of pediatric pyelonephritis. In eight patients shown to have acute pyelonephritis by 99mTc DMSA renal cortical scintigraphy, five were found to have focal abnormalities of renal perfusion by color Doppler sonography in the same sites as the scintigraphic defects (sensitivity-63%). Two of the five patients had normal plain sonograms. False positive studies occurred in patients with documented chronic renal scarring. The specificity of vascular asymmetry was 70%. This preliminary report suggests that, particularly in the patient without pre-existing renal scarring, color Doppler evaluation of the renal vasculature may increase the sensitivity of sonography in the diagnosis of pyelonephritis in children.

Vesicoureteral reflux simulating renal function: CT appearance

Urine may enter the pelvicalyceal system of the kidney either through renal excretion or via the ureter by vesicoureteral reflux. Opacified cyalyces and pelvis after the administration of intravenous contrast material are therefore not necessarily proof that the kidney is functioning. This phenomenon, well known from intravenous urography, may be observed on computed tomography studies as well. We present a case in which a CT scan showed a normal left and a contracted pyelonephritic right kidney with contrast material in pelvis and calydes of both kidneys without parenchymal enhancement on the right side. Subsequently marked vescioureteral reflux to the right kidney was demonstrated on cystourethrography and the kidney was shown to have no function on a nuclear scan. Contrast material in the collecting system associated with a small non-enhancing kidney on CT scan should suggest vesicoureteral reflux.

Migratory lobar nephronia

Lobar nephronia or focal bacterial nephritis is a pre-abscess stage of localized cellulitis and has been shown to represent a focal imaging manifestation of what is frequently a diffuse renal process. To the best of our knowledge, although multi-focal bacterial nephritis has been described, a migratory pattern has not been observed. This report describes a previously healthy 32-year-old woman with pathologically proven lobar nephronia that exhibited a migratory pattern on serial computed tomography (CT) and a prolonged course on antibiotic therapy. Possible etiologies for this unusual course, along with the CT, sonographic and needle biopsy features of this disease are discussed.

The role of scintigraphy in urinary tract infection

There is controversy regarding the role of radiological imaging for urinary tract infection (UTI). The "gold standard" has been the intravenous pyelogram (IVP). Yet, the IVP has a very limited value with only about 25% of children with pyelonephritis demonstrating abnormalities. Ultrasound (US) has recently been advocated as a replacement for the poorly sensitive and poorly specific IVP. However, comparative studies between US and IVP indicate only an equivalent sensitivity and specificity. Cortical scintigraphy with Technetium-99m glucoheptonate (99mTc GH) or 99mTc dimercaptosuccinic acid (99mTc DMSA) has also been advocated as a means of differentiating parenchymal (pyelonephritis) from nonparenchymal (lower UTI) involvement in UTI. The clinical presentation may be misleading especially in the infant and child in whom an elevated temperature, flank pain, shaking chills, or an elevated sedimentation rate are often lacking. The clinician attempts to localize the site of infection for it has a direct bearing upon the therapy. A collecting system infection can often be eradicated with a single oral dose of an appropriate antibiotic, whereas renal parenchymal involvement requires IV therapy for an extended interval. Cortical scintigraphy can localize the site of infection with a high degree of accuracy. Recent studies report a sensitivity of 86% and specificity of 81% of pyelonephritis. This is in contrast to the IVP with a sensitivity of only 24% and US with a sensitivity of only 42%. The scintigraphic appearance of parenchymal infection of the kidney is a spectrum of minimal to gross defects reflecting the degree of histologic involvement that spans from a mild infection to frank abscess. Cortical scintigraphy can be used to monitor the evolution of scarring following infection. Cortical scintigraphy with 99mTc DMSA or 99mTc GH is the method of choice for the initial evaluation of UTI. Not only does it have a very high sensitivity and specificity for differentiating parenchymal from collecting system disease, but it also provides an accurate quantitative measurement of function and in combination with radioiodinated orthoiodohippurate renography and Lasix (furosemide; Abbott Laboratories, North Chicago) diuresis will also differentiate significant obstruction from stasis. The use of radionuclide techniques opens new vistas for the investigation of UTI. Cortical scintigraphy should become the gold standard by which other technologies, therapy, and theoretical considerations of pyelonephritis are measured.