Urinary aquaporin-2 excretion during early human development

Post-obstructive diuresis after posterior urethral valve treatment in neonates: a retrospective cohort study

BACKGROUND

The management of posterior urethral valve (PUV) in neonates requires close monitoring in the intensive care unit because of the risk of post-obstructive diuresis (POD). Our aim was to describe the incidence and factors associated with POD in newborns treated for PUV.

METHODS

Retrospective analysis of the medical records of all neonates who underwent surgical intervention for PUV in our neonatal intensive care unit between January 2014 and April 2021.

RESULTS

Of the 40 patients included, 15 (37.5%) had POD defined by urine output > 6 ml.kg-1.h-1 during the first 24 h following urinary tract obstruction relief. At prenatal ultrasound examinations, oligohydramnios was more common in the group with POD than in the group without (53.3% vs. 8%, p = 0.002). Preterm birth was more frequent in neonates with POD (66.7% vs. 8%; p < 0.001). Median serum creatinine (212 [137-246] vs. 95 [77-125] µmol.l-1; p < 0.001) and urea (8.5 [5.2-12.2] vs. 4.1 [3.5-4.7] mmol.l-1; p < 0.001) concentrations on the day of obstruction relief were significantly higher in the group with POD than in the group without. After adjustment for prematurity, logistic regression models confirmed correlation between the occurrence of POD and the severity of the consequences of urethral obstruction (i.e., oligohydramnios and serum creatinine levels; ß = 2.90 [0.88; 5.36], p = 0.013 and ß = 0.014 [0.003; 0.031], p = 0.034, respectively).

CONCLUSIONS

In neonates, POD is common after the relief of PUV-related obstruction. Our findings may help to identify patients at highest risk. A higher resolution version of the Graphical abstract is available as Supplementary information.

The value of urinary interleukin-18 in predicting acute kidney injury: a systematic review and meta-analysis

Aims

The aim of this study was to systematically review relevant studies to evaluate the value of urinary interleukin-18 (uIL-18) in predicting acute kidney injury (AKI).

Methods

A comprehensive search of PubMed, Medline, Embase, and Cochrane Library was conducted for literature published up to 1 August 2022. Quality Assessment Tool for Diagnostic Accuracy Studies-2 (QUADAS-2) was applied to assess the literature quality. Then, relevant data were extracted from each eligible study and a random-effects regression model was utilized to pool sensitivity, specificity, and construct summary receiver operating characteristic (SROC) and area under curve (AUC).

Results

Twenty-six studies with 7183 patients were enrolled and relevant information was extracted. The estimated sensitivity and specificity of uIL-18 in the diagnosis of AKI were 0.64 (95% confidence interval (CI): 0.54–0.73) and 0.77 (95%CI: 0.71–0.83), respectively. The pooled diagnostic odds ratio (DOR) was 6.08 (95%CI: 3.63–10.18), and the AUC of uIL-18 in predicting AKI was 0.78 (95%CI: 0.74–0.81). Subgroup analysis showed that uIL-18 in pediatric patients was more effective in predicting AKI than in adults (DOR: 7.33 versus 5.75; AUC: 0.81 versus 0.77).

Conclusions

Urinary IL-18 could be a relatively good biomarker with moderate predictive value for AKI, especially in pediatric patients. However, further research and clinical settings are still needed to validate our findings.

The effectiveness of urinary TIMP-2 and IGFBP-7 in predicting acute kidney injury in critically ill neonates

BACKGROUD

Urinary tissue inhibitor of metalloproteinase-2 (TIMP-2), insulin-like growth factor binding protein-7 (IGFBP-7) and the combination of TIMP-2 and IGFBP-7 ([TIMP-2]•[IGFBP7]) are proposed to be predictive biomarkers for acute kidney injury (AKI). The intention of our study was to determine whether there is any significant predictive value of these biomarkers for the occurrence of AKI and severe AKI in critically ill neonates.

METHODS

Urinary samples were serially collected in 237 neonates during neonatal intensive care unit (NICU) stay for measurements of TIMP-2 and IGFBP-7 in this prospective study. AKI diagnosis was based on KDIGO classification without urine output or serum creatinine >1.2 mg/dL.

RESULTS

Twenty neonates developed AKI, including 11 with KDIGO stage 1, defined as mild AKI, and 9 with stages 2 and 3, defined as severe AKI. Urinary IGFBP-7 and [TIMP-2]•[IGFBP7] remained associated with AKI after adjustment for gestational age, gender and illness severity. Urinary [TIMP-2]•[IGFBP7] achieved an AUC of 0.71 (P = 0.034) and displayed a sensitivity of 88.9% and a specificity of 50.9% for discriminating severe AKI at the optimal cut-off value of 0.045.

CONCLUSION

The combination of TIMP-2 and IGFBP-7 had independent discriminative value for severe AKI in critically ill neonates.

Early urinary angiotensinogen excretion in critically ill neonates

INTRODUCTION

Urinary angiotensinogen is considered a reliable biomarker for intrarenal renin-angiotensin system activity. The aims of this study were to assess the urinary angiotensinogen level during the first day of life and to evaluate its correlation with renal function in critically ill neonates.

METHODS

Urinary angiotensinogen concentration during the first 24 hours of life was measured in 98 critically ill neonates. Neonatal renal function was assessed by urinary levels of cystatin-C, albumin and α1-microglobulin and urinary electrolyte excretion.

RESULTS

Urinary angiotensinogen level decreased with increasing gestational age and body weight in critically ill neonates (P<0.001). After adjustment for gestational age, urinary angiotensinogen level correlated with urinary fractional excretion of sodium and urinary levels of cystatin-C and α1-microglobulin. Multivariate linear regression identified a significant impact of urinary cystatin-C on urinary angiotensinogen level (P<0.001). Furthermore, urinary angiotensinogen was significantly increased in neonates with a urinary cystatin-C-to-creatinine ratio ⩾2500 ng/mg, which was the optimal cut-off value to predict acute kidney injury in our previous study.

CONCLUSIONS

The urinary angiotensinogen level correlates with the overall maturity of renal function during the early postnatal period in critically ill neonates and an increased urinary angiotensinogen level might reflect renal injury in immature neonates.

Urine interleukin-18 in prediction of acute kidney injury: a systemic review and meta-analysis

BACKGROUND

Interleukin-18 (IL-18) mediates ischemic acute tubular necrosis; it has been proved as a rapid, reliable, and affordable test marker for the early detection of acute kidney injury (AKI), but its predictive accuracy varies greatly.

METHODS

MEDLINE and EMBASE, Cochrane Library, Ovid, and Springerlink (from inception to November 15, 2013) were searched for relevant studies (in English) investigating diagnostic accuracy of urine IL-18 to predict AKI in various clinical settings. The text index was increasing or increased urine IL-18 level and the main outcome was the development of AKI, which was primarily based on serum creatinine level [using risk, injury, failure, loss and end-stage renal disease (RIFLE), acute kidney injury network, or modified pediatric RIFLE criteria in pediatric patients]. Pooled estimates of diagnostic odds ratio (OR), sensitivity and specificity were calculated. Summary receiver operating characteristic curves were used to calculate the measures of accuracy and Q point value (Q*). Remarkable heterogeneity was explored further by subgroup analysis based on the different clinical settings.

RESULTS

We analyzed data from 11 studies of 3 countries covering 2,796 patients. These studies were marked by limitations of threshold and non-threshold effect heterogeneity. Across all settings, the diagnostic OR for urine IL-18 level to predict AKI was 5.11 [95% confidence interval (CI) 3.22-8.12], with sensitivity and specificity respectively at 0.51 and 0.79. The area under the ROC curve of urine IL-18 level to predict AKI was 0.77 (95% CI 0.71-0.83). Subgroup analysis showed that urine IL-18 level in pediatric patients (<18 years) and early AKI predictive time (<12 h) were more effective in predicting AKI, with diagnostic ORs of 7.51 (2.99-18.88), 8.18 (2.19-30.51), respectively.

CONCLUSION

Urine IL-18 holds promise as a biomarker in the prediction of AKI but has only moderate diagnostic value.

Aquaporin 2: Identification and analysis of expression in calves’ urine during their first month of life

Michałek, K., Dratwa-Chałupnik, A., Ciechanowicz, A. K. and Malinowski, E. 2014. Aquaporin 2: Identification and analysis of expression in calves’ urine during their first month of life. Can. J. Anim. Sci. 94: 653–659. Aquaporin 2 (AQP2) is a vasopressin-regulated water channel of the renal collecting duct and is excreted into urine. Renal excretion of AQP2 has been studied in humans, dogs, rats and mice. The aim of this study was to identify and analyze expression of AQP2 in calves’ urine. Short and controlled diarrhea was induced in the calves in order to determine any change in renal excretion of AQP2 and to evaluate a possible role of this channel in water balance during the neonatal period. For this purpose, an additional portion of lactose was administered to the calves with a milk replacer. The present work shows that after transient diarrhea associated with excessive supply of lactose in the diet, a significant increase in renal AQP2 excretion was reported in the first 3 wk of the calves’ lives. Renal excretion of this protein in the urine increased significantly despite the absence of changes in the concentration of vasopressin or the osmotic pressure of the blood plasma. The increase observed in the expression of the protein might be associated with the reduction of the total Ca2+ concentration in the blood plasma of calves. The results clearly indicate a different mechanism regulating urinary excretion of AQP2 in newborn calves, hitherto unknown. Although elevated renal excretion of AQP2 was observed, there was no increase in the osmolality of the urine in the calves tested.

Impact of sepsis on the urinary level of interleukin-18 and cystatin C in critically ill neonates

BACKGROUND

Urinary interleukin-18 (uIL-18) and cystatin C (uCysC) are biomarkers of acute kidney injury (AKI). We hypothesized that in non-AKI neonates, the level of uIL-18 and uCysC would be higher in those with sepsis compared to those without sepsis. The aims of this study were to determine the association between urinary biomarkers and sepsis in non-AKI critically ill neonates, and to evaluate whether uIL-18 and uCysC could serve as predictors of sepsis in this population.

METHODS

The study included 111 non-AKI critically ill neonates with acute clinical deterioration suggestive of sepsis: 26 with infection, 57 without infection, and 28 were assigned to the unclassified group. Urinary samples were collected and a full sepsis screen was performed at the time of enrollment.

RESULTS

The level of uIL-18, but not uCysC, was significantly elevated in non-AKI septic neonates. Urinary IL-18 was an independent factor associated with sepsis assessed by multivariate analysis, had odds ratio of 1.73 (95 % CI 1.15 to 2.58, p = 0.008), and achieved the area under the receiver operating characteristic curve of 0.74 for predicting the presence of sepsis in non-AKI critically ill neonates.

CONCLUSIONS

Sepsis has an impact on the level of uIL-18, but not on the uCysC in non-AKI neonates, suggesting systemic infection might influence the diagnostic value of uIL-18 to detect AKI in the general population.

Urine interleukin-18 and cystatin-C as biomarkers of acute kidney injury in critically ill neonates

BACKGROUND

Urinary interleukin-18 and cystatin-C are suggested to be biomarkers for predicting acute kidney injury (AKI). The aims of this study are to examine whether the urinary concentrations of interleukin-18 and cystatin-C vary with gestational age and other factors in non-AKI control neonates, and to determine whether urinary interleukin-18 and cystatin-C can predict AKI development in non-septic critically ill neonates, independently of potential confounders.

METHODS

We enrolled 62 non-septic critically ill neonates. Urine was collected every 48-72 h during the first 10 days of life.

RESULTS

Urinary concentration of cystatin-C, but not interleukin-18, decreased with increasing gestational age and body weight, but not with increasing postnatal age in non-AKI control neonates. Both urinary interleukin-18 and cystatin-C were associated with AKI, even after controlling for gestational and postnatal age, birth weight, gender, Apgar score and the score for neonatal acute physiology in non-septic critically ill neonates. Urinary interleukin-18 and cystatin-C had odds ratios of 2.27 and 2.07, and achieved the area under-the-receiver-operating-characteristic curve of 0.72 and 0.92, respectively, for predicting AKI.

CONCLUSIONS

The urinary concentration of cystatin-C, but not interleukin-18, may decrease with increasing renal maturity. Both urinary interleukin-18 and cystatin-C are independently predictive of AKI in non-septic critically ill neonates.

Urinary aquaporin-2 excretion during ibuprofen or indomethacin treatment in preterm infants with patent ductus arteriosus

AIM

Water channel AQP2 is the target for vasopressin (AVP) and a major determinant of urinary concentrating capacity. In mature kidneys, prostaglandins counteract the effect of AVP on AQP2 expression at functional sites. We investigated whether disturbances in water homeostasis in infants with patent ductus arteriosus (PDA) treated with prostaglandin inhibitors can be attributed to activation of AQP2.

METHODS

In 53 infants with symptomatic PDA (gestational age 24-33 weeks), 30 receiving ibuprofen and 23 indomethacin starting at 2-15 days of life, clinical and biochemical data were collected before treatment and after each dose of the drugs. Urinary AQP2 was determined by dot immunoblotting.

RESULTS

Urinary AQP2 level and osmolality were decreased in both groups. Urinary osmolality was overall low and correlated inversely with fluid uptake. In ibuprofen group, there was no correlation of AQP2 level with urinary osmolality.

CONCLUSION

There was no AQP2 upregulation in the infants. The low urinary osmolality and dissociation between urinary osmolality and urinary AQP2 level indicate that the fluid retention sometimes observed in PDA infants treated with prostaglandin inhibitors is not caused by increased levels of functional AQP2. Thus, knowledge about the renal physiology of the adult cannot always be transferred to the infant kidney.

Aquaporin-2 urinary excretion in preterm infants: relationship to diuresis and vasopressin

AIMS

Few investigations have explored the urinary aquaporin-2 (u-AQP2) excretion pattern after birth in preterm infants with conflicting results regarding the correlation between u-AQP2, urinary osmolality and vasopressin. The aims of this study were to evaluate u-AQP2 excretion during the first week of life in preterm infants, to correlate u-AQP2 with other markers of renal function and to investigate the relationship between u-AQP2, urinary tonicity and arginine-vasopressin in the immature kidney.

METHODS

In infants born less than 33 weeks daily diuresis, u-AQP2, urinary arginine-vasopressin, urine and plasma tonicity, creatinine and electrolytes were measured through the first 7 days of life.

RESULTS

Fifty-five infants were evaluated. u-AQP2 excretion showed the following profile: the highest u-AQP2 levels were found on day 2 and values remained significantly higher until day 5 with respect to day 1. On day 6, u-AQP2 levels significantly decreased to values closer to those found on day 1. u-AQP2 excretion was not associated with arginine-vasopressin while significant, but weak association was found with urinary tonicity (r = -0.20; -0.32 < r < -0.11; P < 0.05). u-AQP2 excretion and creatinine clearance were significantly associated during the study period (r = 0.19; 0.08 < r < 0.29; P < 0.05). There was a strong association between totally u-AQP2 excretion and diuresis over the week (r = 0.72; 0.66 < r < 0.76; P < 0.0001).

CONCLUSION

Significant variations occur in AQP2 expression levels during the first week of life in preterm infants. AQP2 does not seem to contribute to the urinary concentration ability after birth. Further investigations are required to elucidate the mechanisms underlying the strong association between diuresis and u-AQP2 excretion in early postnatal life.

The renal adverse effects of ibuprofen are not mediated by AQP2 water channels

The aim of this study was to determine (1) whether ibuprofen treatment in very preterm infants causes an increase in the renal water channel aquaporin-2 (AQP2) activity in the collecting duct via prostaglandin synthesis inhibition and (2) whether AQP2 activity remains disturbed long after ibuprofen treatment has ended. This was a prospective study involving premature infants with a gestation age of 27-31 weeks who received treatment between December 2005 and August 2006 in a tertiary Neonatal Intensive Care Unit. Each ibuprofen-treated infant was matched to two controls. Renal glomerular and tubular function were evaluated weekly for 1 month, and urinary AQP2 was measured by immuno-dotting. In total, 166 longitudinal samples were analyzed in 36 infants. Median [interquartile range] gestational age and birthweight were 28 [27.0-29.5] weeks and 1160 [1041-1242] g, respectively. Perinatal factors were similar in both groups. Urine output was significantly decreased in the ibuprofen-treated infants during the treatment. The urinary AQP2 level decreased significantly from day 2 to day 7 in both groups and was similar thereafter for the first month of life in ibuprofen-treated and control groups. Based on our results, we conclude that ibuprofen-induced oligo-anuria is not associated with a change in AQP2 activity and that ibuprofen does not affect AQP2 activity during the first month of life in very preterm neonates.