Nephrolithiasis Associated with Nephrocalcinosis Is Primarily Composed of Carbonate Apatite.

INTRODUCTION: This study was designed to determine the mineral composition of calculi in nephrocalcinosis with nephrolithiasis, diagnose the underlying disease, and monitor the course of renal function in patients with nephrocalcinosis-nephrolithiasis. METHODS: Renal calculi extruded in a series of 8 patients with nephrocalcinosis were analysed using Fourier transmission infrared spectrometry. In 4 patients, next-generation sequencing using a nephrocalcinosis-nephrolithiasis panel was performed to determine the nature of the underlying disease. In addition, longitudinal analysis of renal function was performed in all patients. RESULTS: Seven patients revealed carbonate apatite as the sole constituent of renal calculi. One patient showed a mixed composition of dicalcium phosphate dihydrate/carbonate apatite at first analysis yet in subsequent episodes also had calculi composed of pure carbonate apatite. Further molecular analysis displayed distal renal tubular acidosis in 2 of 4 patients who consented to sequencing. No known genetic defect could be found in the other two cases. In line with prior reports, decline of renal function was dependent on underlying disease. Distal renal tubular acidosis revealed a progressive course of renal failure, whereas other causes showed stable renal function in long term analysis. CONCLUSION: Nephrocalcinosis with nephrolithiasis is a rare condition with heterogeneous aetiology. Yet mineral composition of renal calculi predominantly consisted of pure carbonate apatite. This uniform finding is similar to subcutaneous calcifications of various origins and might propose a general principle of tissue calcification. Progressive decline of renal function was found in distal renal tubular acidosis, whereas other conditions remained stable over time.

Ultrasound Markers in Fetal Hydronephrosis to Predict Postnatal Surgery.

PURPOSE: Parents confronted with the finding of antenatal hydronephrosis (ANH) are particularly interested in whether their baby will need postnatal surgery. The objective of this study was to predict ANH requiring surgery on the basis of the fetal anteroposterior renal pelvic diameter (APRPD) and the Society for Fetal Urology (SFU) grading system. MATERIALS AND METHODS: The medical records of 179 patients with the finding of ANH were reviewed retrospectively. ANH was graded according to the SFU grading system. Prenatal ultrasound examinations were correlated to postnatal outcome, which was divided into three groups: prenatal resolution, conservative management and surgical treatment. RESULTS: 58 (32.4 %) cases were classified as prenatal resolution, 89 (49.7 %) babies were assigned to the conservative outcome group and 32 (17.9 %) patients needed surgical repair. Postnatal surgery was best predicted in the second trimester (area under the receiver operating characteristics curve: 0.839) by an APRPD cut-off of 8.3 mm (sensitivity: 77.8 %; specificity: 85.7 %; PPV of 53.9 %, NPV of 94.7 %). The combination of the parameters "progression of SFU grade" and SFU grade 3 or 4 achieved a sensitivity of 84.4 % and a specificity of 80.3 % for the prediction of surgery. CONCLUSION: Second-trimester APRPD is a useful parameter for predicting the risk for postnatal surgery. The SFU grade should be assessed in every prenatal ultrasound examination as some further risk estimates can be made based on its dynamics over time.