Analysis of urine composition from split 24-h samples: use of 12-h overnight samples to evaluate risk factors for calcium stones in healthy and stone-forming children

Experimental Study on Solidification Characteristics of Sessile Urine Droplets on a Horizontal Cold Plate Surface under Natural Convection

As the human excreta, urine is often used as one of the test materials in medical research due to its composition and content directly reflecting the health status of the body. Considering that the substances in urine may show different effects on its freezing process, solidification characteristics of sessile urine droplets on a horizontal cold plate surface under natural convection were experimentally investigated by comparing with those of water droplets under same conditions. To make the conclusion analysis more reasonable, the urine of a human without any diseases, especially metabolic diseases, was treated and used. The characteristics include nucleation location, dynamic variation of droplet color, and temperatures at different heights inside the droplet, and so forth. It was found that, similar to that of a water droplet, the solidification process of a urine droplet also experiences the following four stages: supercooling, recalescence, freezing, and cooling, in chronological order. Differently, the urine droplet changes from transparent to blur white at the supercooling stage due to the precipitation of inorganic salts. For nucleation locations, 46.67% cases are at the bottom, while others are at the top and middle of urine droplets. For a 10 μL droplet on a surface of -30 °C, urine has a 0.95 s freezing duration shorter than water, and a 5.31 °C lower phase-transition temperature. Results of this study are expected to reflect the content of substances in urine and thus provide references for urinalysis of patients with metabolic diseases.

Evaluation of urinary acidification in children: Clinical utility

The kidney plays a fundamental role in acid-base homeostasis by reabsorbing the filtered bicarbonate and by generating new bicarbonate, to replace that consumed in the buffering of non-volatile acids, a process that leads to the acidification of urine and the excretion of ammonium (NH₄ ⁺). Therefore, urine pH (UpH) and urinary NH₄ ⁺ (UNH₄ ⁺) are valuable parameters to assess urinary acidification. The adaptation of automated plasma NH₄ ⁺ quantification methods to measure UNH₄ ⁺ has proven to be an accurate and feasible technique, with diverse potential indications in clinical practice. Recently, reference values for spot urine NH₄ ⁺/creatinine ratio in children have been published. UpH and UNH₄ ⁺, aside from their classical application in the study of metabolic acidosis, have shown to be useful in the identification of incomplete distal renal tubular acidosis (dRTA), an acidification disorder, without overt metabolic acidosis, extensively described in adults, and barely known in children, in whom it has been found to be associated to hypocitraturia, congenital kidney abnormalities and growth impairment. In addition, a low UNH₄ ⁺ in chronic kidney disease (CKD) is a risk factor for glomerular filtration decay and mortality in adults, even in the absence of overt metabolic acidosis. We here emphasize on the need of measuring UpH and UNH₄ ⁺ in pediatric population, establishing reference values, as well as exploring their application in metabolic acidosis, CKD and disorders associated with incomplete dRTA, including growth retardation of unknown cause.

Global metabolic profiling of hemorrhagic shock and resuscitation

Hemorrhagic shock (HS) is a medical emergency during trauma. Significant loss of tissue perfusion may result in cellular hypoxia, organ damage and death. The primary treatment of HS is control of the source of bleeding as soon as possible and fluid replacement (crystalloid solutions and blood transfusion). Metabolomics can identify novel biomarkers for various functional and organic diseases. Therefore, systematic exploration of the biological mechanisms of HS and blood transfusion enables the optimization of treatments for HS to reduce the occurrence of organ damage. In this study, a global metabolic profiling strategy is applied to evaluate metabolic changes in the HS rat model. A serum metabolic network with 58 significant metabolites was constructed for HS and resuscitation. Our investigation will offer insights into the pathogenesis.