Effect of thromboxane and nitric oxide blockade on renal blood flow increase during volume expansion in hydronephrotic rats

Changes of arterial pressure following relief of obstruction in adults with hydronephrosis

BACKGROUND

As much as 20% of all cases of hypertension are associated with kidney malfunctions. We have previously demonstrated in animals and in pediatric patients that hydronephrosis causes hypertension, which was attenuated by surgical relief of the ureteropelvic junction (UPJ) obstruction. This retrospective cohort study aimed to investigate: (1) the proposed link between hydronephrosis, due to UPJ obstruction, and elevated arterial pressure in adults; and (2) if elevated blood pressure in patients with hydronephrosis might be another indication for surgery.

MATERIALS AND METHODS

Medical records of 212 patients undergoing surgical management of hydronephrosis, due to UPJ obstruction, between 2000 and 2016 were assessed. After excluding patients with confounding conditions and treatments, paired arterial pressures (i.e. before/after surgery) were compared in 49 patients (35 years old; 95% CI 29-39). Split renal function was evaluated by using mercaptoacetyltriglycine (MAG3) renography before surgical management of the hydronephrotic kidney.

RESULTS

Systolic (-11 mmHg; 95% CI 6-15 mmHg), diastolic (-8 mmHg; 95% CI 4-11 mmHg), and mean arterial (-9 mmHg; 95% CI 6-12) pressures were significantly reduced after relief of the obstruction (p < 0.001). Split renal function of the hydronephrotic kidney was 39% (95% CI 37-41). No correlations were found between MAG3 and blood pressure level before surgery or between MAG3 and the reduction of blood pressure after surgical management of the UPJ obstruction.

CONCLUSIONS

In adults with hydronephrosis, blood pressure was reduced following relief of the obstruction. Our findings suggest that elevated arterial pressure should be taken into account as an indication to surgically correct hydronephrosis.

Changes in arterial pressure and markers of nitric oxide homeostasis and oxidative stress following surgical correction of hydronephrosis in children

OBJECTIVE

Recent clinical studies have suggested an increased risk of elevated arterial pressure in patients with hydronephrosis. Animals with experimentally induced hydronephrosis develop hypertension, which is correlated to the degree of obstruction and increased oxidative stress. In this prospective study we investigated changes in arterial pressure, oxidative stress, and nitric oxide (NO) homeostasis following correction of hydronephrosis.

METHODS

Ambulatory arterial pressure (24 h) was monitored in pediatric patients with hydronephrosis (n = 15) before and after surgical correction, and the measurements were compared with arterial pressure measurements in two control groups, i.e. healthy controls (n = 8) and operated controls (n = 8). Markers of oxidative stress and NO homeostasis were analyzed in matched urine and plasma samples.

RESULTS

The preoperative mean arterial pressure was significantly higher in hydronephrotic patients [83 mmHg; 95% confidence interval (CI) 80-88 mmHg] than in healthy controls (74 mmHg; 95% CI 68-80 mmHg; p < 0.05), and surgical correction of ureteral obstruction reduced arterial pressure (76 mmHg; 95% CI 74-79 mmHg; p < 0.05). Markers of oxidative stress (i.e., 11-dehydroTXB₂, PGF_2α, 8-iso-PGF_2α, 8,12-iso-iPF_2α-VI) were significantly increased (p < 0.05) in patients with hydronephrosis compared with both control groups, and these were reduced following surgery (p < 0.05). Interestingly, there was a trend for increased NO synthase activity and signaling in hydronephrosis, which may indicate compensatory mechanism(s).

CONCLUSION

This study demonstrates increased arterial pressure and oxidative stress in children with hydronephrosis compared with healthy controls, which can be restored to normal levels by surgical correction of the obstruction. Once reference data on ambulatory blood pressure in this young age group become available, we hope cut-off values can be defined for deciding whether or not to correct hydronephrosis surgically.

Ureteropelvic junction obstruction causes histologic alterations in contralateral kidney

BACKGROUND/PURPOSE

Ureteropelvic junction (UPJ) obstruction causes histologic alterations both in ipsilateral and contralateral kidney. Because these alterations directly affect the fate of renal damage, definition of these alterations is of utmost importance from the clinical point of view. Thus, an experimental study is designed to determine the alterations of renal histology in response to partial and complete UPJ obstruction.

METHODS

Fifteen adult female New Zealand rabbits were assigned randomly into 3 groups (each containing 5 rabbits) according to the degree of unilateral UPJ obstruction as group I, sham operation was performed and served as the control group; group II, partial UPJ obstruction was made; group III, complete UPJ obstruction was made. The animals in group I and II were killed after 3 weeks, and animals in group III were killed after 2 weeks. Tissue samples were prepared and processed according to routine light microscopic tissue processing.

RESULTS

UPJ obstruction led to glomerulosclerosis, dilatation of proximal and distal tubules of loops of Henle, and dilatation of collecting tubes consistent with necrotic and apoptotic changes in ipsilateral kidneys. Severity of these degenerative changes depended on degree of obstruction. UPJ obstruction also led to histologic alterations on the contralateral kidneys such as glomerular edema, congested blood vessels, dilated tubuli, and necrotic and apoptotic changes in epithelia, which were more prominent in group III than group II.

CONCLUSIONS

It is well known that compensating changes including increased blood flow and parenchymal hypertrophy occurs in contralateral kidney as a response to unilateral UPJ obstruction. However histologic findings of this study confirmed progression of parenchymal damage and presence of apoptosis in contralateral kidney for the first time.