Elevated Renal Pelvic Pressure Research Articles

Sympathoexcitatory responses to renal chemosensitive stimuli are exaggerated at nighttime in rats.

The circadian cycle impacts sympathetic nerve activity (SNA), cardiovascular hemodynamics, and renal function. Activation of renal sensory nerves by chemosensory and mechanosensory stimuli reflexively changes efferent SNA and arterial blood pressure (ABP) to maintain homeostasis. However, it is unclear to what extent circadian cycle influences reflex SNA and ABP responses to renal sensory stimuli. Renal, splanchnic, and lumbar SNA and ABP responses to intrarenal arterial infusion of bradykinin or capsaicin and elevated renal pelvic pressure were measured in male and female Sprague-Dawley rats during nighttime (wakeful/active phase) and daytime (inactive phase). Intrarenal arterial bradykinin infusion significantly increased efferent renal SNA, splanchnic SNA, and ABP but not lumbar SNA. Responses were greater during nighttime versus daytime. Similarly, intrarenal arterial capsaicin infusion significantly increased renal SNA and splanchnic SNA, and responses were again greater during nighttime. Elevated renal pelvic pressure increased renal SNA and splanchnic SNA; however, responses did not differ between daytime and nighttime. Finally, afferent renal nerve activity responses to bradykinin were not different between daytime and nighttime. Thus, renal chemokines elicit greater sympathoexcitatory responses at nighttime that cannot be attributed to differences in afferent renal nerve activity. Collectively, these data suggest that the circadian cycle alters the excitability of central autonomic networks to alter baseline SNA and ABP as well as the magnitude of visceral reflexes.NEW & NOTEWORTHY The current study discovers that the circadian cycle influences sympathetic and hemodynamic responses to activation of renal chemosensitive sensory fibers. Sympathetic responses to intrarenal bradykinin or capsaicin infusion were exaggerated during nighttime (active period), but mechanosensitive responses to elevated renal pelvic pressure were not. Importantly, renal afferent nerve responses were not different between nighttime and daytime. These data suggest that the circadian cycle modulates sympathetic responses to visceral afferent activation.

Renal chemosensitive and mechanosensitive afferent responses are preserved in TRPV1 knockout rats

The transient receptor potential vanilloid type‐1 (TRPV1) channel is expressed in renal sensory nerves, and intrarenal administration of the TRPV1 agonist capsaicin increases renal afferent nerve activity (ARNA). Nonselective denervation of renal sensory nerves using high concentration capsaicin reduces arterial blood pressure (ABP) in experimental models of hypertension. Pharmacological blockade of TRPV1 using renal pelvic infusion of capsazepine attenuates ARNA responses to capsaicin, CGRP, and elevated pelvic pressure. Thus, TRPV1 channels mediate activation of renal sensory nerves.To test this hypothesis, we generated a novel TRPV1 knockout rat (TRPV1‐/‐) using CRISPR/Cas9 to produce a 26bp deletion in exon 3. Multifiber ARNA responses to chemical (bradykinin and capsaicin) and mechanical (elevated renal pelvic pressure) stimuli were compared in Inactin‐anesthetized male and female wild‐type and TRPV1‐/‐ littermates (250‐400g). There were no significant differences in baseline mean ABP between wild‐type and TRPV1‐/‐ rats (122±2 mmHg vs 122±3 mmHg, respectively; p=0.48, n=8‐10), or baseline ARNA between wild‐type and TRPV1‐/‐ rats (14±3 Hz vs 18±5 Hz, respectively; p=0.24, n=8‐10).Intrarenal artery infusion of capsaicin (0.1–10μM, 50μL per 15s) significantly increased ipsilateral ARNA in wild‐type but not TRPV1‐/‐ rats (Δ discharge 65±14 Hz vs 9±3 Hz at 10μM, respectively; p<0.05, n=7). As a second chemosensitive stimulus, intrarenal artery infusion of bradykinin (0.1–10μM, 50μL per 15s) produced significant increases in ARNA in ­both wild‐type and TRPV1‐/‐ rats that were not significantly different between groups (Δ discharge of 10μM: 52±11 Hz vs 76±21 Hz, respectively; p=0.33, n=7). Elevated renal pelvic pressure (0–20mmHg; 30s) significantly increased ARNA in both wild‐type and TRPV1‐/‐ rats; however, ARNA responses were significantly smaller in wild‐type versus TRPV1‐/‐ rats (Δ discharge with 20mmHg: 17±3 Hz versus 29±6 Hz, respectively; p=0.03, n=8‐9).The preservation of ARNA responses in TRPV1‐/‐ rats contradicts prior studies using pharmacological TRPV1 antagonists. A final set of experiments tested whether intrapelvic capsazepine infusion (200μM, 200μl per 3 min) attenuates ARNA responses to elevated pelvic pressure (20mmHg) in both wild‐type and Trpv1‐/‐ rats. Interestingly, pelvic administration of capsazepine attenuated mechanosensitive ARNA responses in both wildtype (saline: 31±3 Hz vs capsazepine: 8±1 Hz; n=3) and TRPV1‐/‐ (saline: 20±7 Hz vs capsazepine: 6±1 Hz; n=3) rats thereby suggesting a TRPV1‐independent action of capsazepine.In conclusion, TRPV1 channels are dispensable for the activation of chemo‐ and mechanosensitive renal sensory nerves.

Abstract MP48: Crispr/cas9 Trpv1 Deletion In Rats Does Not Impair Mechano- And Chemo-sensory Renal Afferent Nerve Responses

Elevated renal afferent nerve activity (ARNA) or dysfunctional renal reflexes contributes to hypertension and chronic kidney disease. The transient receptor potential vanilloid type-1 (TRPV1) channel is expressed in renal sensory nerves, and intrarenal administration of the TRPV1 agonist capsaicin increases ARNA. Nonselective denervation of renal sensory nerves using high-concentration capsaicin reduces arterial blood pressure (ABP) in experimental models of hypertension. However, the role of TRPV1 channels in ARNA responses to chemo- and mechano-sensitive stimuli has not been directly tested. To test this hypothesis, we generated a novel TRPV1 rat knockout model (TRPV1 -/- ) using CRISPR/CAS9 to delete exon 3 . ARNA multifiber recordings were performed in male and female TRPV1 -/- and wild-type littermates (250-400g) after decerebration or Inactin anesthesia (data combined). Wild-type and TRPV1 -/- rats had no significant differences in baseline mean ABP (126±4 mmHg vs 138±5 mmHg, respectively; n=8-10) or heart rate (451±25 bpm vs 432±24 bpm, respectively; n=8-10). Baseline ARNA was not different between wild-type and TRPV1 -/- rats (16±3 Hz vs 28±6 Hz, respectively; n=8-10). Intrarenal artery infusion of the TRPV1 agonist capsaicin (0.1-10μM, 50μL per 15s) significantly increased ipsilateral ARNA in wild-type but not TRPV1 -/- rats (Δ discharge with 10μM: 65±3 Hz vs 6±1 Hz, respectively; n=5-7). As a second chemosensitive stimulus, intrarenal artery infusion of bradykinin (0.1-10μM, 50μL per 15s) produced similar increases in ipsilateral ARNA between wild-type and TRPV1 -/- rats (Δ discharge with 10μM: 52±6 Hz vs 73±18 Hz, respectively; n=5-6). Finally, elevated renal pelvic pressures (0-20mmHg; 30s) significantly increased ipsilateral ARNA in both wild-type and TRPV1 -/- rats; however, the ARNA response was significantly greater in TRPV1 -/- versus wild-type rats (Δ discharge with 20mmHg: 47±14 Hz versus 18±6 Hz, respectively; n=5-8). In conclusion, mechanosensitive and chemosensitive ARNA responses remain intact in TRPV1 -/- rats. The mechanisms responsible for renal sensory nerve activation remain unidentified and the impact of TRPV1 deletion in rat models of hypertension and kidney disease remains to be tested.

The Whitaker Test in the Follow-up of Complex Upper Urinary Tract Reconstruction: Is It Clinical Useful or Not.

To evaluate the feasibility and guiding significance in postoperative management of the Whitaker test after complex reconstruction of the upper urinary tract. Patients who underwent complex ureteral reconstruction and received the Whitaker test after surgery between December 2018 and December 2019 were included. We judged it abnormal that the renal pelvis pressure was higher than 22 cmH2O or the pressure difference was greater than 15 cmH2O. The results were used as a reference for removing the nephrostomy tube. Based on whether the renal pelvic pressure was higher than 22 cmH2O, the patients were divided into the elevated pelvis pressure group and the normal group. Follow ups at 1 month and every 3 months were collected. A total of 19 patients were included. Fifteen patients did not present obvious abnormalities. One patient suffered from contrast infiltrating into the renal parenchyma, and the pressure was higher than 15 cmH2O. Ureteral stent implantation was performed. The other 3 patients had either elevated pelvis pressure or insufficient image, 2 of which prolonged the duration of nephrostomy tubes. The median follow-up time was 12.6 months. CTU/MRU after removing nephrostomy tubes indicated improved/stable hydronephrosis in all patients. The creatinine in the elevated pelvis pressure group was higher than that in the normal group (91.4 ± 27.6 vs 86.7 ± 16.5 μmol/L, P = .782), and the eGFR was lower (76.0 ± 14.0 vs 81.8 ± 24.1 mL/min/1.73m2, P = .695), but without significant difference. The change in creatinine during follow-up in the elevated renal pelvic pressure group was significantly different from that in the normal group (-13.6 ± 1.0 vs -0.2 ± 10.6 umol/L, P = .047). Postoperative Whitaker test can help judge whether nephrostomy could be removed. Elevated pressure in upper urinary tract after reconstruction suggests the need to prolong the time of the nephrostomy tube or even re-intervene. Proper management for patients with elevated renal pelvis pressure can help restore the renal function.

A simple fluid dynamic model of renal pelvis pressures during ureteroscopic kidney stone treatment.

Ureteroscopy is an endoscopic kidney stone removal procedure which increases the internal pressure in the renal pelvis, the kidney’s urinary collecting system. Elevated renal pelvic pressure may result in systemic absorption of irrigation fluid and urine, which can increase the risk of postoperative fever and sepsis. Urologists have investigated the effects of various surgical parameters on the renal pelvic pressure. However, it still remains unknown which surgical parameter has the most dominant effect on the renal pelvic pressure over time. Here we develop a physical model that computes the renal pelvic pressure as a function of time based on parameters that can be varied during ureteroscopy. The model is developed by applying pipe network analysis to the regions of the urinary tract that are involved in a representative ureteroscopic procedure. Our model unifies the findings of the previously published studies on this topic; an ex-vivo porcine study and an in-vivo human study. Furthermore it allows simulation of surgical procedures based on various techniques. Our simulation demonstrates that the two strong regulators of renal pelvis pressure during ureteroscopy are the size of the gap between ureteroscope and ureteral access sheath and the frequency and duration of ureteroscope withdrawal.

Pay much attention to control and manage the high pressure of renal plevic and the backflow of irrigation during the operation of urolithiasis of upper tract urinary

Endoscopic surgery has become the most common urological procedure for calculus in upper urinary tract. However, the widespread usage of minimally invasive endoscopic techniques failed to end the occurrence of perioperative complications, especially some fatal complications. The most severe complication of urolithiasis related endoscopic procedure is urosepsis, which is closely related to the backflow of irrigation fluid induced by the high pressure of renal pelvic during the procedure. By controlling the perfusion and drainage during the operation, the liquid backflow can be reduced effectively, thus may reduce the spread of infectious toxins and pathogens, and incidence of infectious complications can be controlled accordingly. In this article, the pathophysiology of urinary obstruction, the backflow which caused by elevated renal pelvic pressure and its subsequent pathophysiological changes, the control of intra-renal gressure and the prevention of urosepsis will be reviewed. The important range of intra-renal pressure and the major steps for pressure control during the operation is emphasized.

Renal Pelvic Pressure in Percutaneous Nephrolithotomy: The Effect of Multiple Tracts.

During percutaneous nephrolithotomy (PCNL), elevated renal pelvic pressures (RPPs) may spread infection through pyelovenous backflow whereas decreased pressures can hinder observation and increase bleeding. The purpose of this study was to evaluate the effects of multiple access tracts and different sized endoscopic equipment on RPP in a porcine model. RPP was measured in one- vs two-tract access, rigid vs flexible nephroscopy, and suction vs no suction. Twenty trials were performed for each condition. An independent samples Mann-Whitney U-test was used to compare parameters, with p < 0.05 considered significant. With one tract, rigid nephroscopy resulted in higher mean pressures (31.35 mm Hg) than flexible nephroscopy (11.1 mm Hg; p < 0.001). The RPP was higher with rigid nephroscopy in one tract (31.35 mm Hg) than when two tracts were present (9.35 mm Hg; p < 0.001). In contrast, there was no difference in pressure during the use of a flexible nephroscope in one (11.1 mm Hg) vs two tracts (10.7 mm Hg; p = 0.63). Use of suction with the rigid nephroscope resulted in significantly lower pressures with one (-1.3 mm Hg) than with two tracts (1.8 mm Hg; p = 0.004). In PCNL, RPP is significantly affected by an additional tract during rigid nephroscopy and suctioning but not when using a flexible nephroscope. Understanding the effects of multiple tracts and equipment type on RPP may improve the safety of PCNL.

Elevated Renal Pelvic Pressures during Percutaneous Nephrolithotomy Risk Higher Postoperative Pain and Longer Hospital Stay.

Renal pelvic pressure may vary during percutaneous nephrolithotomy. We sought to determine the relationship of postoperative pain to endoscope caliber, renal pelvic pressure and hospital stay. We reviewed the records of 20 percutaneous nephrolithotomies done under ureteroscopic guidance with renal pelvic pressure monitoring. The ureteroscope working channel was connected to a pressure transducer and used to determine renal pelvic pressure at baseline, when irrigating with a 26Fr rigid nephroscope and a 16Fr flexible nephroscope, and during suction. Patient demographics, operative characteristics, Likert pain scores and length of hospital stay were compared as stratified by average renal pelvic pressure. The Mann-Whitney U and Fisher exact tests were used with p<0.05 considered significant. A total of 220 measurements were recorded in 20 patients undergoing single access percutaneous nephrolithotomy. Mean patient age was 55.2 years (range 20 to 77) and mean body mass index was 32.4 kg/m2 (range 18 to 53.3). Rigid nephroscopy resulted in significantly higher average renal pelvic pressure than flexible nephroscopy (30.3 vs 12.9 mm Hg, p = 0.007). Average renal pelvicpressure was 30 mm Hg or greater in 7 patients (35%) undergoing rigid nephroscopy and in none (0%) undergoing flexible nephroscopy (p <0.01). Patients exposed to an average renal pelvic pressure of 30 mm Hg or greater during rigid nephroscopy had significantly higher average pain scores (p = 0.004) and longer hospital stays (p = 0.04) than patients with renal pelvic pressure less than 30 mm Hg. Average renal pelvic pressure 30 mm Hg or greater during rigid nephroscopy was also associated with a longer skin to calyx distance (105.5 vs 79.7 mm, p = 0.03). Knowledge of the factors that influence renal pelvic pressure and methods to control pressure extremes may improve patient outcomes during percutaneous nephrolithotomy.

Relationship between HbA1c and lipid oxidation parameters in type-2 diabetic patients

Radionuclide procedures are clinically used for assessing obstruction in dilated urinary tracts. The precise correlation of the isotope retention function with the level of the renal pelvic pressure is not known as yet. It was measured experimentally using 20 minipigs, By means of ureterostomies in situ reaching into the pyelon the 40 kidneys were subjected to varying pressures (seven to 62 cm. H20) while the renal processing of 123-I-orthoiodine-hippuric-acid was recorded. The correlation of five radionuclide parameters with the pelvic pressure was computed: the time to the peak value of the isotope nephrography (t-max) and renal transit time correlated very well with high grade pelvic pressure (>37 cm. H20): r = 0.91 and 0.86 respectively, but much less well with low grade pelvic pressure (<37 cm. H20): r = 0.73 and 0.62 respectively. The slope of the third phase of the isotope nephrography (tan-turn) and the time to the turning point of its tangent (t-turn) correlated only weakly with elevated renal pelvic pressure: r = 0.62 and 0.59 respectively. In conclusion, radionuclide procedures give excellent qualitative information on the level of pelvic pressure. They cannot, however, be used even as an indirect means for quantitatively assessing elevated renal pelvic pressure, which in urinary obstruction is thought to be one of the factors jeopardizing renal function.

Does a Smaller Tract in Percutaneous Nephrolithotomy Contribute to High Renal Pelvic Pressure and Postoperative Fever?

High renal pelvic pressure brings systemic absorption of irrigation fluid containing bacteria or endotoxins, which leads to postoperative fever. We inspected the renal pelvic pressure (RPP) in vivo during minimally invasive percutaneous nephrolithotomy (MPCNL) to investigate whether a 14- to 18-French percutaneous tract and perfusion would bring high RPP and postoperative fever. Between July 2005 and December 2007, 80 patients were selected for RPP measurement during MPCNL. The RPP was measured by a baroceptor connected to the open-ended ureteric catheter, which was indwelling retrogradely in the renal pelvic. A computer recorded the RPP each second, and all the data were evaluated statistically with SPSS 12.0 software. During MPCNL with 14-, 16-, 18-, and double-16-French percutaneous tracts, the mean RPP was 24.55, 16.49, 11.22, and 6.64 mm Hg, respectively. Logistical analysis suggested that postoperative fever did not correlate to gender (P = 0.195), age (P = 0.641), urinary tract infection (P = 0.663), white blood cell > or = 10 x 10(9)/L in routine postoperative blood examination (P = 0.751), or an occurrence of renal pelvic pressure > or = 30 mm Hg in the operation (P = 0.662), although infection calculi (P = 0.000), percutaneous tract (P = 0.029), mean RPP (P = 0.036), mean RPP > or = 20 mm Hg (P = 0.013), accumulated time of RPP > or = 30 mm Hg (P = 0.010), and RPP > or = 30 mm Hg longer than 50 s (P = 0.024) may contribute a postoperative fever. Renal pelvic pressure generally remains lower than the backflow level (30 mm Hg) during MPCNL via a 14- to 18-French percutaneous tract. Any factors that brought about poor drainage would result in temporarily elevated RPP greater than 30 mm Hg, and many such occurrences of high pressure would have an accumulating effect, which means enough backflow to cause bacteremia and postoperative fever.

The Influence of Minimally Invasive Percutaneous Nephrolithotomy on Renal Pelvic Pressure In Vivo

To inspect the renal pelvic pressure during minimally invasive percutaneous nephrolithotomy (MPCNL) and to investigate whether the use of the 14 to 18-Fr percutaneous tract, 8/9.8-Fr rigid ureteroscope, and a perfusion with high pressure furnished for MPCNL results in high renal pelvic pressure. Between July 2005 and February 2006, 76 patients were selected for renal pelvic pressure measurement during MPCNL. The renal pelvic pressure was measured by a baroceptor of the invasive blood pressure channel in a MAIDRAY PM9000 monitor, which was connected to the open-ended ureteric catheter indwelled in the renal pelvis retrogradely. The computer collected the renal pelvic pressure data each second and all the data were evaluated statistically with SPSS 12.0 software. During MPCNL within the 14, 16, 18, and double-16-Fr percutaneous tracts, the average renal pelvic pressures were 24.85, 16.23, 11.68, and 5.8 mm Hg, respectively. The average lasting times of renal pelvic pressure >/=30 mm Hg were 283, 96, 44, and 10 seconds, respectively. A postoperative fever >/=38 degrees C was recorded in 2 (2/12), 3 (3/30), 2 (2/21), and 1 case (1/13), respectively. Renal pelvic pressure generally remains lower than the level required for a backflow (30 mm Hg), during MPCNL via 14 to 18-Fr percutaneous tract. Any factor, which causes bad drainage, will result in a temporarily elevated renal pelvic pressure greater than 30 mm Hg; and multiple temporary high-pressure episodes can have a cumulative effect, which means that there will be enough backflow to cause a bacteremia.

Effect of urinary tract infection on ureteropelvic junction obstruction in a rat model

Objectives When a partially obstructed kidney becomes infected, more rapid and extreme renal parenchymal damage appears to occur than might result from either infection or obstruction alone. Previously, we showed that either bacteriuria or partial obstruction in congenital unilateral hydronephrosis causes elevated renal pelvic pressures in a rat model. In this same model, we examined the combined effects of partial upper tract obstruction and bacteriuria on renal pelvic and bladder pressures. Methods Female rats from an inbred colony in which more than one half are born with unilateral obstructive hydronephrosis were studied. Type 1 piliated Escherichia coli was instilled into the bladder. Two to 6 days later, the bladder and renal pelvic pressures were measured during varying urinary flows (less than 2 to more than 30 mL/kg/hr). All animals were killed and the kidneys and bladder grossly and histologically assessed. Hydronephrosis was determined at pathologic examination. Results Eight rats had congenital unilateral hydronephrosis; five were normal. Acute inflammation was found in all bladder and renal specimens. In hydronephrotic, infected kidneys, the renal pelvic pressures exceeded those in nonhydronephrotic, infected kidneys at all urinary flow rates. Bladder capacity and pressures did not differ between the two groups. Conclusions This model demonstrates that the combination of infection and obstructive hydronephrosis in this model causes renal pelvic pressure elevation that is higher than that associated with either infection or obstructive hydronephrosis alone. These data demonstrate the compound effect that infection and obstruction may have on the kidney and offers an explanation for why this clinical situation is more likely to be associated with greater renal parenchymal injury than either alone.

OXYBUTYNIN DECREASES RENAL PELVIC PRESSURES IN NORMAL AND INFECTED RAT URINARY TRACT

Since abnormally elevated renal pelvic pressures may contribute to renal damage, we examined whether an anticholinergic agent could decrease elevated renal pelvic pressures. We have previously demonstrated in a rat model that renal pelvic pressures rise physiologically during normal bladder filling and high urinary flows; these pressures rise to abnormal levels during acute urinary tract infection (UTI). In these studies we investigated the effects of oxybutynin on the in vivo rat urinary tract. Simultaneous bladder and renal pelvic pressures were measured with and without oxybutynin at low (<2 ml./kg./hr.), moderate (2-10), high (10-20), and very high (>20) urinary flows while the rat bladder filled and emptied spontaneously. Although minimal differences were found between bladder filling pressures with and without oxybutynin, at higher urinary flows the renal pelvic pressure in oxybutynin treated rats was significantly lower than in nontreated animals. Indeed, when rats with urinary tract infection were treated with oxybutynin, their renal pelvic pressures were lower than those in uninfected rats. We conclude that oxybutynin affects rat upper urinary collecting system pressures, and is capable of decreasing abnormally elevated renal pelvic pressures due to urinary tract infection to normal or subnormal levels.

Oxybutynin decreases renal pelvic pressures in normal and infected rat urinary tract.

Since abnormally elevated renal pelvic pressures may contribute to renal damage, we examined whether an anticholinergic agent could decrease elevated renal pelvic pressures. We have previously demonstrated in a rat model that renal pelvic pressures rise physiologically during normal bladder filling and high urinary flows; these pressures rise to abnormal levels during acute urinary tract infection (UTI). In these studies we investigated the effects of oxybutynin on the in vivo rat urinary tract. Simultaneous bladder and renal pelvic pressures were measured with and without oxybutynin at low (<2 ml./kg./hr.), moderate (2-10), high (10-20), and very high (>20) urinary flows while the rat bladder filled and emptied spontaneously. Although minimal differences were found between bladder filling pressures with and without oxybutynin, at higher urinary flows the renal pelvic pressure in oxybutynin treated rats was significantly lower than in nontreated animals. Indeed, when rats with urinary tract infection were treated with oxybutynin, their renal pelvic pressures were lower than those in uninfected rats. We conclude that oxybutynin affects rat upper urinary collecting system pressures, and is capable of decreasing abnormally elevated renal pelvic pressures due to urinary tract infection to normal or subnormal levels.

OXYBUTYNIN LOWERS ELEVATED RENAL PELVIC PRESSURES IN A RAT CONGENITAL UNILATERAL HYDRONEPHROSIS

We investigated whether oxybutynin could lower elevated renal pelvic pressures measured in a rat with an inbred unilateral congenital hydronephrosis. Simultaneous renal pelvic and bladder pressures were measured in 8 hydronephrotic rats and compared to those of 10 hydronephrotic rats treated with intravenous injection of 1.6 mg./kg. oxybutynin. Pressures were recorded at different urinary flow rates and during bladder filling and emptying. Hydronephrotic rats not given oxybutynin showed significantly higher renal pelvic pressures (e.g. p-bladder at 50% capacity = 8.9 +/- 3.1 cm. H 2 O, corresponding p-pelvis = 20.8 +/- 2.1 at very high urinary flow rates) than rats treated with oxybutynin. The latter had renal pelvic pressures similar to rats with normal non-hydronephrotic kidneys (e.g. p-bladder at 50% capacity = 10.1 +/- 3.5 cm. H 2 O, corresponding p-pelvis = 6.3 +/- 1.1 at very high urinary flow rates). Renal pelvic pressures were, moreover, lower than corresponding bladder pressures in contrast to the untreated hydronephrotic pelvic pressure that exceeded bladder pressure. This effect of oxybutynin in lowering elevated renal pelvic pressures in the obstructed kidney has not been described before and suggests a possible role for oxybutynin in this condition.

Oxybutynin lowers elevated renal pelvic pressures in a rat congenital unilateral hydronephrosis.

We investigated whether oxybutynin could lower elevated renal pelvic pressures measured in a rat with an inbred unilateral congenital hydronephrosis. Simultaneous renal pelvic and bladder pressures were measured in 8 hydronephrotic rats and compared to those of 10 hydronephrotic rats treated with intravenous injection of 1.6 mg./kg. oxybutynin. Pressures were recorded at different urinary flow rates and during bladder filling and emptying. Hydronephrotic rats not given oxybutynin showed significantly higher renal pelvic pressures (e.g. p-bladder at 50% capacity = 8.9 +/- 3.1 cm. H2O, corresponding p-pelvis = 20.8 +/- 2.1 at very high urinary flow rates) than rats treated with oxybutynin. The latter had renal pelvic pressures similar to rats with normal non-hydronephrotic kidneys (e.g. p-bladder at 50% capacity = 10.1 +/- 3.5 cm. H2O, corresponding p-pelvis = 6.3 +/- 1.1 at very high urinary flow rates). Renal pelvic pressures were, moreover, lower than corresponding bladder pressures in contrast to the untreated hydronephrotic pelvic pressure that exceeded bladder pressure. This effect of oxybutynin in lowering elevated renal pelvic pressures in the obstructed kidney has not been described before and suggests a possible role for oxybutynin in this condition.

Pressure Decay Half-life: A Method for Characterizing Upper Urinary Tract Urine Transport

Purpose We examined the pressure dynamics of hydronephrotic kidneys after elevated renal pelvic pressure developed. Materials and Methods A total of 40 patients (44 renal units) 0.2 to 12 years old was evaluated. Transiently elevated renal pelvic pressure was induced with a percutaneous nephrostomy infusion. After renal pelvic pressure increased the infusion was stopped and the subsequent decrease in pressure with time was plotted as a pressure decay curve. The rapidity of the decrease in renal pelvic pressure was then quantitated as a half-life for each pressure decay curve. Pressure decay half-lives were compared to corresponding pressure flow study results and diuretic nuclear renography half-lives. Results Renal units without elevated renal pelvic pressure during infusion at a high physiological flow rate were associated with relatively rapid pressure decay, whereas those with elevated renal pelvic pressure during infusion were associated with much slower pressure decay (p less than 0.0001). Diuretic nuclear renography half-lives had no correlation with collecting system pressure dynamics. Conclusions Pressure decay half-life provides an objective quantitative measure of the relative tendency for elevated renal pelvic pressure to persist. When used in conjunction with other diagnostic modalities, it may be a useful parameter for a comprehensive assessment of the risk of pressure induced injury in hydronephrotic kidneys.

The Effect of Bacteriuria on Bladder and Renal Pelvic Pressures in the Rat

We investigated the effect of urinary tract infection on bladder and renal pelvic urodynamics in a rat model to examine the role of pressure during infection. Either an antibiotic solution (control group) or Escherichia coli with type 1 pili (infected group) was instilled into the bladder. After 2 to 6 days simultaneous continuous bladder and renal pelvic pressures were measured during urinary flows from less than 2 to greater than 20ml./kg. per hour while the bladder filled and emptied. Bladder pressures from 50 to 100% of maximum capacity and maximum voiding pressures were significantly higher in the infected group than the control group (36.7 ± 6.79cm. water versus 25.5 ± 5.21cm. water, respectively, p <0.0001). Renal pelvic pressures were significantly higher in the infected group during bladder filling at all urinary flows examined and actually exceeded bladder pressure for the highest flows. We conclude that elevated renal pelvic pressures may contribute to renal changes observed during urinary tract infection.

Dynamics of the upper urinary tract: II. The effect of variations of peristaltic frequency and bladder pressure on pyeloureteral pressure/flow relations

For pt. I see ibid., vol.32, no.7, p.813-22 (1987). The dynamics of pyeloureteral flow is described when there is no peristalsis and for peristalsis of high and intermediate frequencies, on the assumption that the ureter is uniform except in the mid-ureter and at the outlet. The possibility of upstream transmission of bladder pressure variations to the renal pelvis is considered. The overall behaviour depends on three principal variables, the maximum tube pressure in the contraction waves, the intrinsic peristaltic carrying capacity and the peristaltic frequency f, expressed in the form fT where T is the time for a peristaltic contraction wave to sweep through the ureter. At intermediate peristaltic frequencies (fT less than but comparable with one) oscillatory flow patterns can occur, in which periods of peristaltically driven flow alternate with extraperistaltic periods of flow through the open ureter. The kidney is better isolated from bladder pressure variations when the peristaltic frequency is high, but high peristaltic frequency can by itself lead to elevated renal pelvic pressure if the flow rate is high. Experimental observations in pigs are presented to support these conclusions.

The Effects of Renal Pelvic Pressure Elevation on Isotope Nephrography and Renal Transit Time, an Experimental Study

Radionuclide procedures are clinically used for assessing obstruction in dilated urinary tracts. The precise correlation of the isotope retention function with the level of the renal pelvic pressure is not known as yet. It was measured experimentally using 20 minipigs, By means of ureterostomies in situ reaching into the pyelon the 40 kidneys were subjected to varying pressures (seven to 62cm. H20) while the renal processing of 123-I-orthoiodine-hippuric-acid was recorded. The correlation of five radionuclide parameters with the pelvic pressure was computed: the time to the peak value of the isotope nephrography (t-max) and renal transit time correlated very well with high grade pelvic pressure (>37cm. H20): r = 0.91 and 0.86 respectively, but much less well with low grade pelvic pressure (<37cm. H20): r = 0.73 and 0.62 respectively. The slope of the third phase of the isotope nephrography (tan-turn) and the time to the turning point of its tangent (t-turn) correlated only weakly with elevated renal pelvic pressure: r = 0.62 and 0.59 respectively. In conclusion, radionuclide procedures give excellent qualitative information on the level of pelvic pressure. They cannot, however, be used even as an indirect means for quantitatively assessing elevated renal pelvic pressure, which in urinary obstruction is thought to be one of the factors jeopardizing renal function.