[Renal functional diagnostics using magnetic resonance imaging]

[Imaging in children and adolescents with urinary tract infections]

CLINICAL/METHODOLOGICAL PROBLEM

Urinary tract infections are among the most common infectious diseases in childhood. The task of imaging is to detect predisposing factors, such as urinary transport disorders, vesicoureteral reflux, as well as complications such as abscesses or pyonephrosis in addition to possible morphological changes of the kidneys and the draining urinary tract during an infection.

STANDARD RADIOLOGICAL PROCEDURES

The initial diagnostic imaging technique is generally sonography. For the diagnosis of vesicoureteral reflux, voiding urosonography or alternatively radiological voiding cystourethrography are used. Further diagnostic workup may include scintigraphy, magnetic resonance imaging (MRI) or, in exceptional cases, computed tomography (CT).

RECOMMENDATION FOR PRACTICE

In children and adolescents, it is of particular importance to avoid recurrent urinary tract infections and their sequelae. This requires precise imaging diagnostics, which must be performed with special consideration of radiation protection.

[Imaging after kidney transplantation in childhood and adolescence]

The ultrasound (US) examination is the most important imaging procedure in the clinical care of children with chronic kidney disease, the assessment before kidney transplantation and in the acute and chronic phase after successful kidney transplantation. In trained hands, particularly with experience in Doppler sonography, US ensures that vascular complications, such as occlusions, thrombosis, stenosis as well as non-vascular complications, e.g., urinary tract dilatation, abscesses, hematomas, urine leaks or lymphoceles, are cost-effectively and rapidly diagnosed at any time. For the diagnosis of acute rejection, the US signs in the intraindividual course are only suggestive, but not specific. The gold standard for the diagnosis of acute rejection is a kidney biopsy. In these cases, US serves to exclude other causes. The use of multimodal techniques, various Doppler techniques and microvascular procedures, such as superb microvascular imaging (SMI) or B‑flow and contrast-enhanced ultrasonography (CEUS), optimizes the imaging in the context of transplantations in children. Magnetic resonance imaging with diffusion-weighed imaging (DWI), magnetic resonance angiography (MRA) and magnetic resonance urography (MRU) as well as functional MRU (fMRU) performed with the administration of gadolinium-containing contrast agents, are part of the extended diagnostics and possibly necessary for surgical planning in the early phase after kidney transplantation and for long-term assessment after transplantation. Excretory urography is associated with ionizing radiation and intravenous administration of iodine-containing contrast medium and is obsolete in children. Computed tomography (CT) using age-adapted and weight-adapted dose protocols is an alternative in emergencies if MRI is not available.

Functional MR urography in children - update 2023

BACKGROUND

 Functional MR urography (fMRU) has developed into an innovative, radiation-free option for assessing parameters of kidney function in pediatric radiology. The importance of fMRU in comparison to the standardized established nuclear medicine procedure (99mTc-Mercapto-acetyltriglycerine, MAG3 scintigraphy) is shown using SWOT analysis.

METHODS

 To assess the current state of research, a selective literature search was carried out in PubMed. Taking into account the current scientific status, the examination technique, preparation, and evaluation of fMRU are presented.

RESULTS

 As a result of the comparison with MAG3, fMRU is suitable for certain indications and represents an optimal combination of morphological and functional representation of the kidneys and urinary tract, especially in the case of surgical consequences.

CONCLUSION

 fMRU has been successfully established as a diagnostic method for assessing the morphology and function of the kidneys in competition with MAG3 scintigraphy.

KEY POINTS

  · Functional MRU allows reliable statements on the morphology and function of the kidneys and urinary tract.. · The results of the functional assessment of fMRU are comparable to the results of MAG3 scintigraphy.. · The complex implementation and demanding evaluation limits the spread of fMRU as a complete alternative to MAG3 scintigraphy. fMRU is reserved for special indications.. · Functional MRU has prevailed over MAG3 scintigraphy for complex renal and urinary tract anomalies (CAKUT) that require surgical correction. An example is the clarification of dribbling in girls, which is usually based on an ectopic opening of a ureter in a double system..

CITATION FORMAT

· Kirsch H, Krüger P, John-Kroegel U et al. Functional MR urography in children - update 2023. Fortschr Röntgenstr 2023; 195: 1097 - 1105.

The diagnostic efficacy of diffusion tensor imaging generated by gadolinium-based magnetic resonance imaging for patients with chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) can lead to systemic inflammatory responses and other cardiovascular disease. Diffusion tensor imaging findings generated by gadolinium-based MRI (DTI-GBMRI) is regarded as a standard method for assessing the pathology of CKD. To evaluate the diagnostic value of DTI-GBMRI for renal histopathology and renal efficiency, renal fibrosis and damage, noninvasive quantification of renal blood flow (RBF) were investigated in patients with CKD.

METHODS

CKD patients (n = 186) were recruited and underwent diagnosis of renal diffusion tensor imaging findings generated by MRI (DTI-MRI) or DTI-GBMRI to identify the pathological characteristics and depict renal efficiency. The cortical RBFs and estimated glomerular filtration rate were compared in CKD patients undergone DTI-GBMRI (n = 92) or DTI-MRI (n = 94).

RESULTS

Gadolinium enhanced the diagnosis generated by DTI-MRI in renal fibrosis, renal damage, and estimated glomerular filtration rate. The superiority in sensitivity and accuracy of the DTI-GBMRI method in assessing renal function and evaluating renal impairment was observed in CKD patients compared with DTI-MRI. Outcomes demonstrated that DTI-GBMRI had higher accuracy, sensitivity, and specificity than DTI-MRI in diagnosing patients with CKD.

CONCLUSION

In conclusion, DTI-GBMRI is a potential noninvasive method for measuring renal function, which can provide valuable information for clinical CKD diagnosis.