title: Surgical treatment reduces blood pressure in children with unilateral congenital hydronephrosis.
abstract: OBJECTIVE
  Renal disorders can cause hypertension, but less is known about the influence of hydronephrosis on blood pressure. Hydronephrosis due to pelvo-ureteric junction obstruction (PUJO) is a fairly common condition (incidence in newborns of 0.5-1%). Although hypertensive effects of hydronephrosis have been suggested, this has not been substantiated by prospective studies in humans [1-3]. Experimental studies with PUJO have shown that animals with induced hydronephrosis develop salt-sensitive hypertension, which strongly correlate to the degree of obstruction [4-7]. Moreover, relief of the obstruction normalized blood pressure [8]. In this first prospective study our aim was to study the blood pressure pattern in pediatric patients with hydronephrosis before and after surgical correction of the ureteral obstruction. Specifically, we investigated if preoperative blood pressure is reduced after surgery and if split renal function and renographic excretion curves provide any prognostic information.
  
  
  METHODS
  Twelve patients with unilateral congenital hydronephrosis were included in this prospective study. Ambulatory blood pressure (24 h) was measured preoperatively and six months after surgery. Preoperative evaluations of bilateral renal function by Tc99m-MAG3 scintigraphy, and renography curves, classified according to O'Reilly, were also performed.
  
  
  RESULTS
  As shown in the summary figure, postoperative systolic (103 ± 2 mmHg) and diastolic (62 ± 2 mmHg) blood pressure were significantly lower than those obtained preoperatively (110 ± 4 and 69 ± 2 mmHg, respectively), whereas no changes in circadian variation or pulse pressure were observed. Renal functional share of the hydronephrotic kidney ranged from 11 to 55%. There was no correlation between the degree of renal function impairment and the preoperative excretory pattern, or between the preoperative excretory pattern and the blood pressure reduction postoperatively. However, preoperative MAG3 function of the affected kidney correlated with the magnitude of blood pressure change after surgery.
  
  
  CONCLUSIONS
  Correction of the obstruction lowered blood pressure, and the reduction in blood pressure appeared to correlate with the degree of renal functional impairment, but not with the excretory pattern. Thus, in the setting of hypertension, it appears that the functional share of the hydronephrotic kidney should be considered an indicator of the need for surgery, whereas the renography curve is less reliable. The strength of the present study is the prospective nature and that ambulatory blood pressure monitoring was used. Future longitudinal prolonged follow-up studies are warranted to confirm the present findings, and to understand if a real nephrogenic hypertension with potential necessity of treatment will develop.
  
  
  CONCLUSIONS
  This novel prospective study in patients with congenital hydronephrosis demonstrates a reduction in blood pressure following relief of the obstruction. Based on the present results, we propose that the blood pressure level should also be taken into account when deciding whether to correct hydronephrosis surgically or not.
authors.affiliation: Pediatric Surgery Section, Department of Women's and Children's Health, Uppsala University, Uppsala, Sweden.
authors.forename: Ammar
authors.initials: A
authors.lastname: Al-Mashhadi
authors.affiliation: Pediatric Nephrology Unit, Department of Women's and Children's Health, Uppsala University, Uppsala, Sweden.
authors.forename: Tryggve
authors.initials: T
authors.lastname: Nevéus
authors.affiliation: Pediatric Surgery Section, Department of Women's and Children's Health, Uppsala University, Uppsala, Sweden.
authors.forename: Arne
authors.initials: A
authors.lastname: Stenberg
authors.affiliation: Pediatric Surgery Section, Department of Women's and Children's Health, Uppsala University, Uppsala, Sweden.
authors.forename: Birgitta
authors.initials: B
authors.lastname: Karanikas
authors.affiliation: Department Medical Cell Biology, Uppsala University, Uppsala, Sweden.
authors.forename: A Erik G
authors.initials: AE
authors.lastname: Persson
authors.affiliation: Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden. Electronic address: mattias.carlstrom@ki.se.
authors.forename: Mattias
authors.initials: M
authors.lastname: Carlström
authors.affiliation: Department of Pediatric Surgery, Astrid Lindgren Hospital, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Nils
authors.initials: N
authors.lastname: Wåhlin
mesh_terms: D000293:Adolescent; D018660:Blood Pressure Monitoring, Ambulatory / Q000379:methods; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006869:Hydronephrosis / Q000150:complications / Q000175:diagnosis / Q000601:surgery*; D006973:Hypertension / Q000175:diagnosis* / Q000209:etiology; D007223:Infant; D007682:Kidney Pelvis / Q000601:surgery*; D016014:Linear Models; D008297:Male; D011182:Postoperative Care / Q000379:methods; D011300:Preoperative Care / Q000379:methods; D011446:Prospective Studies; D018570:Risk Assessment; D018709:Statistics, Nonparametric; D016896:Treatment Outcome; D013520:Urologic Surgical Procedures / Q000379:methods*
keywords: Hydronephrosis; Hypertension; Pelvo-ureteric junction obstruction; Pyeloplasty; Renal function