International audienceWhile calcium oxalate monohydrate (whewellite: CaC2 O 4 H 2 O) kidney stones are related to hyperoxaluria, calcium oxalate dihydrate (weddellite: CaC 2 O 4(2 + x)H 2 O) ones are mainly associated with hypercalciuria. Crystalline conversion from weddellite to whe-wellite introduces a contradiction between Fourier transform infrared (FTIR) spectra which indicate the presence of whewellite and the fact that bipyramid crystallites, a morphology specific of weddellite, can be observed. It constitutes thus a major problem for clinicians as hyperoxaluria and hypercalciuria are associated with very different aetiologies and treatments. In this contribution, the complete set of data including neutron diffraction experiments, observations through a last generation field emission scanning electron microscope as well as 3D and 2D cross-section visualisations derived from the mComputed Tomography measurements seems to explain some particular features observed on FTIR spectra related to the crystalline conversion from weddellite to whewellite. The structural hypothesis which is proposed is related to the formation of amorphous whewellite, a new polymorph recently synthesised. Thus, in such cases, special attention should be paid to the stone morphology (and not FTIR spectrum), which is a major element for clinical diagnosis as already underlined for other types of urinary calculi
PSM subclassifications do not improve the biochemical recurrence prediction in organ-confined disease. In non-organ-confined disease, PSM length (≥3 mm), multifocality (≥3 sites), and apical location are significantly linked to poorer outcomes and could justify a more aggressive adjuvant treatment approach.
Clogging of endoscopic stents necessitates their replacement in many patients with malignant obstructive jaundice and limits their use in benign strictures. We studied the basic mechanism of clogging to find ways to prevent it. We did light and electron microscopy studies of blocked and functioning stents, which were prepared so that organic structures would be preserved. The material blocking the lumina was composed of a matrix of bacterial cells and their fibrillar anionic extracellular products. Crystals of calcium bilirubinate, calcium palmitate, and cholesterol were embedded within this matrix. Bacterial cells were attached to the stent surface by a fibrillar matrix, suggesting that the initial event in stent clogging is the development of an adherent bacterial biofilm. Bacterial enzyme activity (beta-glucuronidase and phospholipase) leads to the deposition of crystals. The use of antibacterial plastics in the manufacture of stents may reduce bacterial adhesion and stent clogging.
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