Effect of renal decapsulation on renal function

Abstract

Marked increases in renal volume commonly occur in acute tubular necrosis and acute transplant rejection. Based on studies in the dog, we have previously suggested that the renal swelling observed in states of acute renal injury may be due principally to an increase in compliance of the kidney. The present study was undertaken in an effort to assess whether compliance-mediated increases in renal volume might affect renal function. In 15 dogs we compared the function of a decapsulated kidney (DK) to that of the contralateral intact kidney (IK); in 12 dogs we compared the function of a partially decapsulated kidney (PDK) to that of the contralateral IK. We compared the function of DK or PDK to IK, first under control conditions (ureteral pressure (UP) equals 0 mmHg), then at increased intrarenal pressure (UP equals 30 mmHg for both kidneys plus iv saline loading), and then during a recovery period (UP of both kidneys restored to 0 mmHg). The rationale is that probably DK is more compliant than IK; thus at increased intrarenal pressure DK volume should increase more than IK volume. Under control conditions DK and IK function were normal and equal; however, during increased intrarenal pressure, glomerular filtration rate (GFR) was about 20% less and Na and H20 excretion were about 30% less in DK than in IK. When intrarenal pressure was restored toward control by lowering UP to 0 mmHg, DK and IK function were once again equal. Similar but less marked changes occurred in the experiments comparing PDK and IK function. The impairment of renal function in DK vs. IK at increased intrarenal pressure was not explained by renal blood flow distribution, backdiffusion of glomerular filtrate, or by surface losses of fluid from DK. We suggest that impairment of renal function in DK vs. IK during increased intrarenal pressure is in some way related to the greater expansion of DK (21.0 +/- 0.02%) vs. IK (9.7 +/- 0.03%) at increased intrarenal pressure.

Electrical properties of the rabbit cortical collecting duct from obstructed kidneys after unilateral ureteral obstruction. Effects of renal decapsulation.

“…Therefore, we conclude that the increase in renal pressure might at least partly explain the defects in Na' and K+ transport in the CCD after ureteral obstruction. It is also possible that renal decapsulation is known to permit surface losses of renal interstitial fluid (37). Thus, we cannot rule out the possibility that surface losses could explain the present findings.…”

“…It should be noted that partial blocking of increased renal pressure with unilateral renal decapsulation had demonstrable protective effects on impaired Na' and K+ transports seen in the CCD after ureteral obstruction. In the 1970s it was also reported that transplant surgeons used partial renal decapsulation of the allograft (incision of the renal capsule) to prevent possible rupture of the allograft during episodes of acute rejection (37,38).…”

Effect of Ischemia on Renal Blood Flow in the Rat

“…Thus, 'no reflow', presumably the result of an increase in renal vascular resistance associated with cell swelling [1,2,10], exists to a modest extent in the rat following acute ischemic in jury and may contribute to the impaired renal function observed in this condition. Other mechanisms, however, have also been impli cated: (1) vasomotor nephropathy (increased preglomerular arteriolar constriction with or without postglomerular arteriolar dilatation [ 11]; (2) increased back-diffusion of glomerular filtrate because of increased tubular perme ability [7,12]; (3) tubular obstruction; (4) a decrease in total glomerular hydraulic con ductivity [13], and (5) renal swelling itself may also contribute to the impaired renal function, perhaps because of the mechanical adjust ments that the renal tubular and vascular net work must make as they participate in the overall expansion of parenchymal volume [14],…”

Effect of Expansion of Renal Parenchymal Volume on Renal Function

“…The left kidney only was weighed because with the present technique it is not possible to weigh the right and the left kidney simultaneously. Furthermore, we have shown previously the weighing technique does not affect renal function [11,12] and that the effect of expansion of renal volume on renal func tion is the same for the right and left kidney [II], During the experiment surface losses of interstitial fluid from CK were collected in an aluminium foil pan placed directly beneath the kidney.…”

“…Furthermore, from our study of the decapsulaled kidney [I I], it appears that the compliance of the renal parenchyma must also be greatly increased to account for the marked swelling of acute renal injury. This interpretation is based on the fact that total renal decapsulation of the normal kidney only modestly disrupts control of renal paren chymal volume, even under conditions which maximally increase intrarenal pressure [11]. Thus, the normal renal parenchyma possesses substantial tissue cohesive forces and, appar ently, these forces must be greatly diminished to account for the marked parenchymal swell ing seen in acute renal injury.…”