ORIGINAL ARTICLE Regional changes in renal cortical glucose, lactate and urea during acute unilateral ureteral obstruction A microdialysis study PETER-MARTIN KRARUP 1,2 , LARS B. STOLLE 1,5 YAZAN F. RAWASHDEH 1,3 , OLE SKOTT 4 , JENS CHRISTIAN DJURHUUS 1 & JORGEN FROEKIAER 1,2 1 Institute of Clinical Medicine and 2 The Water and Salt Research Centre, University of Aarhus, Aarhus, Denmark, 3 Department of Urology, Aarhus University Hospital, Skejby, Denmark, 4 Physiology and Pharmacology, University of Southern Denmark, Odense, Denmark, and 5 Department of Plastic Surgery, Aarhus Hospital, Aarhus, Denmark Abstract Objective . Acute unilateral ureteral obstruction (UUO) leads to changes in kidney function and metabolism. Microdialysis offers the possibility of topical analysis of changes in kidney metabolism. We applied microdialysis to the porcine kidney and evaluated its impact on gross kidney function. Furthermore, we investigated regional variations in renal interstitial fluid (RIF) glucose, lactate and urea during acute UUO. Material and methods . Eight anesthetized pigs were used. Microdialysis probes were inserted in the upper, middle and lower thirds of the left renal cortex and perfused with Ringer’s chloride at a rate of 0.3 ml/min. Dialysates were fractionated for 30-min periods. Bilateral intrapelvic pressure, urinary output, urinary osmolality, the excretion fractions of sodium and potassium, renal blood flow and the glomerular filtration rate were measured. Subsequently, left-sided graded ureteral obstruction was initiated, using the kidney’s own urine production as a counter-pressure. Results . The application of three microdialysis probes did not have any impact on kidney function. Ureteral obstruction decreased RIF glucose in the upper and lower thirds of the kidney, but not in the middle third. RIF lactate did not change. Interstitial urea increased in all regions of the kidney, but most markedly in the upper and lower poles. Conclusions . Microdialysis is of potential value for assessing the renal interstitial milieu under different pathophy- siological conditions. Ureteral obstruction resulted in regional differences in cortical metabolites, predominantly affecting the upper and lower poles. Key Words: Microdialysis, obstruction, ureteral, metabolism, pig Introduction Ureteral obstruction leads to changes in glomerular filtration rate (GFR), renal hemodynamics [1] and intrarenal metabolism [2], including decreased glu- cose oxidation [3] and renal gluconeogenesis [3,4], together with an increase in anaerobic glycolysis [5]. In polypapillary kidneys, such as those of humans, there is evidence of inherent structural and func- tional heterogeneity. In terms of morphology the renal papillae are heterogeneously distributed, with compound papillae dominating the kidney poles and simple papillae the middle zone [6]. During steady- state conditions, polar cortical blood flow is lower than that in the middle zone [7]. These intrarenal differences may give rise to a heterogeneous pattern in certain renal diseases such as intrarenal reflux [6] and acute unilateral ureteral obstruction (UUO) [8]. In UUO a marked polar vascular underfilling has been reported [8]. New investigative tools are necessary in order to better understand the patho- genesis of UUO. It has not previously been investi- gated whether changes in renal metabolism subsequent to acute UUO are regionally distributed within the polypapillary kidney. Microdialysis is a method that enables regional in vivo analysis of the renal interstitial fluid (RIF) [9]. Briefly, the microdialysis probe mimics the capillary Correspondence: Peter-Martin Krarup, MD, Clinic of Urology, Esbjerg Hospital, Finsensgade 35, DK-6700 Esbjerg, Denmark. E-mail: krarup@ki.au.dk Scandinavian Journal of Urology and Nephrology, 2007; 41: 47  53 (Received 18 January 2006; accepted 28 April 2006) ISSN 0036-5599 print/ISSN 1651-2065 online # 2007 Taylor & Francis DOI: 10.1080/00365590600795305 Downloaded By: [University of Copenhagen North] At: 11:04 8 February 2010