MRI assessment of the influence of body position on the shape and position of the urinary bladder

OBJECTIVE

Continuous surveillance of patients' bladder volume may be of benefit during the treatment of various urologic disorders. In order to design optimal bladder volume monitoring equipment, information about the shape and position of the bladder, not at least in relation to posture, is crucial. The purpose of this study was consequently to evaluate the influence of body position on the change in shape and position of the bladder.

MATERIAL AND METHODS

MRI was performed in three young volunteers during posture changes. MRI scans in the transverse, frontal and sagittal planes were recorded in bladders of various sizes. The position of the bladder midpoint in the three planes was determined. Moreover, to account for its shape, the compactness of the cross-section of the bladder was calculated on the basis of its perimeter and area.

RESULTS

For the medial-lateral and cranial-caudal positions, the maximal displacements were 4 and 5 mm, respectively. In the ventral-dorsal direction the displacement varied, but was <18 mm. The compactness changed maximally by 11%, indicating a minimal change in shape.

CONCLUSION

In young subjects, the position and shape of the bladder only change modestly for different body positions, thus eliminating the need for special correction measures when designing bladder volume monitoring equipment.

Male fetal pig lower urinary tract function. Part II: free voiding pattern close to term and in the newborn

PURPOSE

We assessed the development of natural voiding function late in gestation and in the immediate postnatal period in a porcine model.

MATERIALS AND METHODS

The study comprised 7 male fetal minipigs (median age 94 days, 0.88 gestation) and 7 male newborn pigs. In all pigs an ultrasonic probe was placed around the subcutaneous urethra and pressure catheters were placed in the bladder and rectum and in the amnionic cavity in the fetal pigs. The catheters were connected to pressure transducers as the flow probe was connected to a flow meter, and the recordings were sampled at a rate of 10 Hz on a personal computer.

RESULTS

The newborns had a median voiding frequency of 3.3 times per hour while the fetuses voided a median of 5.9 times per hour (p = 0.16). Both groups voided with a staccato flow at a frequency of 1 to 2 Hz, indicating voiding dyscoordination between the detrusor and urethra. Maximum flow rate increased from median 4.4 ml per minute (range 2.0 to 8.8) in the fetal group to median 10.9 (5.4 to 18.3) in the newborns (p = 0.07). While the minimum opening pressure remained unchanged (median 7.0 cm H2O, range 5.7 to 13.0) vs median 7.6, (range 7.7 to 14.0, p = 0.57) the detrusor pressure at maximum flow decreased from median 22.4 cm H2O (range 16.6 to 39.0) in the fetal pigs to 12.1 cm H2O (8.3 to 22.3) in the newborns.

CONCLUSIONS

Fetal and newborn pigs have dyscordinated voiding with a staccato flow. While the urethral opening pressure appears to be unchanged, the detrusor pressure at maximum flow decreases during the last period of gestation, indicating decreased urethral resistance. These findings are in accordance with observations made in human infants.

Neonatal ureteral obstruction alters expression of renal sodium transporters and aquaporin water channels

BACKGROUND

Congenital urinary tract obstruction is a common cause of renal insufficiency in the neonate and during infancy. Recently, we demonstrated that ureteral obstruction in adult rats is associated with reduction in the abundance of renal aquaporins (AQPs) and renal sodium transporters, which paralleled an impaired urinary concentrating capacity.

METHODS

In the present study, renal handling of sodium and water, together with the expression of renal aquaporins and major renal sodium transporters, was examined in rats with neonatally induced partial unilateral ureteral obstruction (PUUO) within the first 48 hours of life to clarify the molecular mechanisms involved in the tubular functional defects in response to congenital obstruction. Rats were then followed for 12 or 24 weeks.

RESULTS

Neonatal PUUO caused a progressive reduction in single kidney glomerular filtration rate (SKGFR) on the obstructed side to 43% of controls at 12 weeks (115 +/- 28 vs. 267 +/- 36 microL/min/100g bw, P < 0.05), and 31% of controls at 24 weeks (106 +/- 24 vs. 343 +/- 41 microL/min/100g bw, P < 0.05). Na-K-ATPase abundance was decreased in the obstructed kidney compared with the nonobstructed kidney at 24 weeks (79 +/- 6%, P < 0.05), and the abundance of bumetanide-sensitive Na-K-2Cl cotransporter (BSC-1) located to the medullary thick ascending limb (mTAL) of the obstructed kidney was significantly reduced both at 12 weeks (42 +/- 10%, P < 0.05) and 24 weeks (50 +/- 10%, P < 0.05). Immunohistochemistry confirmed down-regulation of BSC-1 both at 12 and 24 weeks after onset of obstruction. Consistent with this, sodium excretion from the obstructed kidney was increased at 12 weeks (0.13 +/- 0.03 vs. 0.04 +/- 0.01 micromol/min/100g bw, P < 0.05), and persisted 24 weeks after onset of PUUO (0.15 +/- 0.02 vs. 0.06 +/- 0.01 micromol/min/100g bw, P < 0.05). AQP2 abundance in the collecting duct was also reduced both at 12 weeks (68 +/- 5%, P < 0.05) and at 24 weeks (69 +/- 13%, P < 0.05). Consistent with this, solute-free water reabsorption was decreased in the obstructed kidney at 12 weeks (0.61 +/- 0.42 vs. 1.97 +/- 0.63 microL/min/100g bw, P < 0.05) and remained decreased after 24 weeks of PUUO (0.42 +/- 0.04 vs. 1.56 +/- 0.39 microL/min/100g bw, P < 0.05).

CONCLUSION

Major sodium transporters and aquaporins in the obstructed kidney are down-regulated in response to neonatally induced PUUO, which indicates that these transporters may play a crucial role for the persistent reduction in renal handling of sodium and water in response to PUUO.

Pharmacokinetics and pharmacodynamics of desmopressin administered orally versus intravenously at daytime versus night-time in healthy men aged 55-70 years

OBJECTIVE

To investigate (1) the pharmacokinetic and pharmacodynamic profiles of desmopressin in men from an age group with a high incidence of nocturia; and (2) circadian variation in the pharmacokinetic parameters.

METHODS

The study had an open, randomised, four-way cross-over design. Desmopressin was administered orally (0.2 mg) and intravenously (2 microg), daytime and night-time, yielding four in-hospital sessions, separated by at least 2 days. Blood samples were taken before and at predetermined time points up to 12 h after dosing. Pharmacokinetic parameters were derived using a two-compartmental model except for AUC(0-->t), which was derived using non-compartmental analysis. Bioavailability was estimated using AUC(0-->t) for the oral and the intravenous periods. Urine, for measurements of volume and osmolality, was collected in predetermined intervals before and until 12 h after dosing.

RESULTS

Fifteen healthy men aged 55-70 years were included in the analysis. The concentration-time curve after 2 microg intravenous desmopressin was best described using a biexponential term. The mean (95% CI) AUC at night was 302 (272-335) pg x h/ml and in the day was 281 (253-312) pg x h/ml. No statistically significant differences were detected between night and day except for terminal half-life, which was 3.1 h at night and 2.8 h in the daytime (P=0.02). After oral desmopressin, concentrations above the limit of quantification (2.5 pg/ml) were only detected in 51% of the samples. Peak plasma concentration (Cmax) was 6.2 (5.1-7.5) pg/ml at night and 6.6 (5.5-7.9) pg/ml in the daytime. Median time to reach Cmax (tmax) was 1.5 (range 1.0-4.1) h at night and 1.5 (range 0.5-3.0) h in the day. The bioavailability was 0.08%. The pharmacodynamic effects of oral and intravenous desmopressin given in the daytime were similar during the first 6 h after dosing. The night-time dosing and daytime intravenous dose resulted in antidiuresis throughout the measuring period, while the effect of the daytime peroral dose receded after 6 h.

CONCLUSION

The pharmacokinetic profile of desmopressin is biexponential. Terminal half-life was longer at night than in the daytime, but the difference is considered too small to be of clinical importance. The plasma levels given by the intravenous dose resulted in a duration of action of 12 h or more. Despite low bioavailability, the pharmacodynamic effects of oral desmopressin were similar in magnitude to those after intravenous dose at night and during the first 6 h after daytime administration.

MONOSYMPTOMATIC NOCTURNAL ENURESIS IS ASSOCIATED WITH ABNORMAL NOCTURNAL BLADDER EMPTYING

PURPOSE

We investigate the nature of enuresis episodes in monosymptomatic nocturnal enuresis using a fluid provocation model.

MATERIALS AND METHODS

The study included 18 children 7 to 13 years old with monosymptomatic nocturnal enuresis. Based on basal home recordings patients were subgrouped into those with a normal nocturnal urine output and those with nocturnal polyuria (mean nocturnal urine production on wet nights exceeding 130% of functional bladder capacity, normal functional bladder capacity for age provided). Children were admitted to the hospital for 4 consecutive nights. After an adaptation night all children received orally 25 ml/kg water, 30 minutes before bedtime on the remaining 3 nights. A cordless alarm device enabled registration of enuretic episodes from another room and diapers allowed the measurement of enuresis volumes. Post-void residual volumes were measured by ultrasound. Pelvic floor electromyography was continuously recorded throughout the night, and its association to bladder emptying was investigated.

RESULTS

A total of 95 enuresis and 14 nocturia episodes were recorded. Significantly more enuresis episodes were registered on nights with oral fluid load, whereas no increase in number of nocturia episodes was seen. Of the enuresis episodes 46 were associated with incomplete bladder emptying (post-void residual volume greater than 10% of total bladder volume at time of enuresis). No difference between patient groups regarding post-void residual volume was seen. Abnormal bursts of electromyography activity were associated with incomplete micturitions.

CONCLUSIONS

Enuresis nocturna episodes in polyuric and nonpolyuric patients are frequently incomplete micturitions. The present findings question the definition of nocturnal enuresis episode as normal complete voiding.

THE EFFECT OF ALARM TREATMENT ON THE FUNCTIONAL BLADDER CAPACITY IN CHILDREN WITH MONOSYMPTOMATIC NOCTURNAL ENURESIS

PURPOSE

We studied the characteristics of a group of monosymptomatic nocturnal enuretics successfully treated with the alarm system, with special reference to changes in functional bladder capacity.

MATERIALS AND METHODS

The diaries of 7 girls and 19 boys 7 to 13 years old with severe nocturnal enuresis, small daytime bladder capacity (70% or less of expected capacity for age) and poor or absent response to desmopressin were analyzed. Patients were treated with an alarm until complete dryness was achieved for 21 consecutive nights before ending therapy. Immediately after the treatment they recorded a 1-week followup diary of voiding and fluid intake.

RESULTS

Mean duration of the alarm treatment was 82 days, and there was no change in nocturnal or 24-hour diuresis from baseline to followup. Nocturia developed during the alarm treatment in 48% of the children. The nocturnal diuresis on nocturia nights was significantly higher than on nights without nocturia. Daytime functional bladder capacity increased significantly in children with and without nocturia.

CONCLUSIONS

Treatment with an alarm system increases daytime functional bladder capacity significantly in children with and without nocturia. A higher nocturnal urine production on nocturia nights explains why some children have nocturia and others do not.

Effects of high frequency deep brain stimulation on urine storage and voiding function in conscious minipigs

AIMS

Suprapontine neural integration during the storage phase is decisive for the timing of voiding. Neurological disorders like Parkinson's disease are thus frequently complicated by bladder dysfunction. The aim of the present study was to investigate the effect of high frequency deep brain stimulation on the urine storage and voiding function in conscious Parkinsonian minipigs.

MATERIALS AND METHODS

Five Goettingen minipigs had a Parkinsonism-like state induced by intoxication with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). An electrode for chronic stimulation was placed unilaterally in the subthalamic nucleus. The effect of stimulation was determined by the outcome of transurethral cystometries performed with the stimulation in on- and off-mode.

RESULTS

Of 20 planned cystometry-sessions 18 were completed. Six incomplete voidings occurred in stimulation on-mode and five in off-mode. Interruption of the stimulation for 2 days was followed by a significant increase in pressure rise on filling to cystometric capacity, from 7 to 21 cmH(2)O (P = 0.005), and an insignificant reduction in cystometric capacity from 30 to 26 ml/kg bodywt. (P = 0.370), leading to a significant decrease in bladder compliance from 124 to 34 ml/cmH(2)O (P = 0.013).

CONCLUSIONS

Transurethral cystometry was a feasible examination technique in pigs. The findings demonstrate that high frequency deep brain stimulation changes the bladder characteristics in the storage phase. Since bladder pressure and capacity responded differently to interruption of stimulation distinct neural mechanisms must be involved in the modulation of sensory information on bladder tension and stretch.

Quantitation of differential renal blood flow and renal function using dynamic contrast-enhanced MRI in rats

A first-pass upslope approach was used to estimate differential renal blood flow (DRBF) and a Patlak-Rutland approach was used to estimate differential renal function (DRF) using Gd-DTPA-BMA-enhanced MRI. DRBF and DRF were estimated in rat kidneys under three different experimental conditions: 1) transient renal artery occlusion (TRAO); 2) partial unilateral ureteric obstruction (PUO); and 3) sham-operated control rats (SHAM). A bolus of Gd-DTPA-BMA was given intravenously during a dynamic single slice T1-weighted gradient echo sequence, which allowed calculation of concentration from signal intensity values. Calculations based on the raw signal intensity showed that DRBF was decreased in both PUO (44 +/- 1%; P < 0.05) and in TRAO (38 +/- 1%; P < 0.05) compared with SHAM (52 +/- 1%). Converting the signal intensity into a measure of Gd-DTPA-BMA concentration did not substantially alter these findings (PUO: 40 +/- 3%, P < 0.05; TRAO: 35 +/- 2%, P < 0.05; SHAM 49 +/- 1%). Likewise, DRF decreased in both PUO (43 +/- 4%; P < 0.05) and TRAO (39 +/- 3%; P < 0.05) compared with SHAM (48 +/- 2%). Converting the signal intensity into measurements of Gd-DTPA-BMA concentration revealed similar findings (PUO: 41 +/- 5%, P < 0.05; TRAO: 34 +/- 5%, P < 0.05; SHAM: 49 +/- 2%). Our results suggest that renal damage in rats may be demonstrated by an observed reduction of DRBF and DRF as estimated from single-slice Gd-DTPA-BMA enhanced signal intensity using time-activity curves with and without quantitation of Gd-concentration.

New probe for the measurement of dynamic changes in the rectum

Conventional mano-volumetric techniques cannot measure changes in circumferential dimensions at several axial positions within a bowel segment. Our aims were to validate a new impedance planimetry probe for simultaneously measuring the cross-sectional area (CSA) at five axial positions in vitro and in vivo in 10 anesthetized pigs. The day-to-day coefficient of variation (CV) for CSA measured by the probe in cylindrical tubes of known diameter was 0.8-9.5%. The mean from actual diameter deviation ranged from 2.3 to 6.7%. In a conical tube the day-to-day CV was 2.3-8% and mean percentage deviation -2.8 to 1.0. Interposed narrowing sections caused a total CV of 7-13%. In vivo studies revealed variations in CSA, associated with expulsion of flatus. It is concluded that impedance planimetry allows simultaneous measurement of CSA at several levels within the rectum. In vitro validity was acceptable and alterations in lumen diameter were identified in vivo.

Early release of neonatal ureteral obstruction preserves renal function

The incidence of congenital hydronephrosis is approximately 1% and is often associated with renal insufficiency. It is unknown whether early release is essential to prevent deterioration of renal function. Rats were subjected to partial unilateral ureteral obstruction (PUUO) on postnatal day 2. The obstruction was left in place or released after 1 or 4 wk. Renal blood flow (RBF) and kidney size were measured sequentially over 24 wk using MRI. In rats in which the obstruction was left in place, RBF of the obstructed kidney was progressively reduced to 0.92 +/- 0.17 vs. 1.79 +/- 0.12 ml.min(-1).100 g body wt(-1) (P < 0.05) after 24 wk. Similarly, glomerular filtration rate of the obstructed kidney was severely reduced at 24 wk: 172 +/- 36 vs. 306 +/- 42 microl.min(-1).100 g body wt(-1) (P < 0.05). These changes were preceded by development of severe hydronephrosis and obstructive nephropathy with a reduction in total protein content: 45 +/- 3 vs. 58 +/- 4 mg/kidney. Moreover, nonreleased PUUO caused a marked natriuresis (0.32 +/- 0.07 vs. 0.11 +/- 0.02 micromol.min(-1).100 g body wt(-1), P < 0.05) and impaired solute free water reabsorption (0.47 +/- 0.16 vs. 2.71 +/- 0.67 microl.min(-1).100 g body wt(-1), P < 0.05), consistent with a significant downregulation of Na-K-ATPase to 62 +/- 7%, aquaporin-1 to 53 +/- 3%, and aquaporin-3 to 53 +/- 7% of sham levels. Release after 1 wk completely prevented development of hydronephrosis, reduction in RBF and glomerular filtration rate, and downregulation of renal transport proteins, whereas release after 4 wk had no effect. These results suggest that early release of neonatal obstruction provides dramatically better protection of renal function than release of obstruction after the maturation process is completed.

Renal function may not be restored when using decreasing differential function as the criterion for surgery in unilateral hydronephrosis

OBJECTIVE

To evaluate the use of decreasing differential function (DF) as an indication for surgery in children with congenital hydronephrosis followed according to a flow chart with repeated renography and ultrasonography.

PATIENTS AND METHODS

The hospital records of consecutive children (0-12 years old) who underwent an Anderson-Hynes pyeloplasty between 1993 and 2000 were reviewed. Follow-up was recommended according to a flow chart, with isotope renography and ultrasonography at 1, 3 and 6 months, and at 1 (2), 3 and 5 years of age. The diagnosis and follow-up were often at the referring hospital. The criteria for surgery included a decrease in renographic DF of > 10% of DF, and a DF of < 42%, breakthrough pyelonephritis despite antibiotic prophylaxis, pain or an anterior-posterior pelvic diameter of > 50 mm.

RESULTS

Fifty-two children with unilateral hydronephrosis were included; eight had surgery because of decreasing DF of the hydronephrotic kidney. Seven children had a prenatal diagnosis. Only one of these eight children was managed according to the recommended procedures for follow-up. In two and possibly three children there was significant irreversible kidney damage since the initial renography before surgery. In one child the initial renography was at 15 months and the DF was < 10%. There was a functional improvement after surgery in three children.

CONCLUSION

Few children undergo surgery for decreasing DF of the hydronephrotic kidney in this study. Failure to adhere to the follow-up schedule was common; this may jeopardize kidney function when using decreasing DF as a criterion for surgery. Therefore, not complying (by medical staff or the patient) with the follow-up should be considered when using expectant management for asymptomatic hydronephrosis. The serious consequences for renal function of not complying with follow-up can be avoided by surgery if the patient risks renal functional deterioration, by close cooperation with medical staff at referring hospitals, and by close follow-up at an early age with renography and ultrasonography.

Conditional stimulation of the dorsal penile/clitoral nerve may increase cystometric capacity in patients with spinal cord injury

AIMS

To investigate the feasibility of conditional short duration electrical stimulation of the penile/clitoral nerve as treatment for detrusor hyperreflexia, the present study was initiated.

METHODS

Ten patients with spinal cord injury, 4 women and 6 men, with lesions at different levels above the sacral micturition center had a standard cystometry performed. During a subsequent cystometry, conditional short duration electrical stimulation of the penile/clitoral nerve was performed as treatment for one or more detrusor hyperreflexic contractions.

RESULTS

In all patients, at least one contraction (mean, 7.8; range, 1-16 contractions) was inhibited by the stimulations. The mean cystometric capacity was increased significantly by conditional electrical stimulation, from 210 mL in the control cystometries to 349 mL in the stimulation cystometries (P=0.016). The maximal detrusor pressure during the first contraction in the control cystometries was mean 51 cm H(2)O, whereas the maximal pressure of the first contraction in the stimulation cystometries was reduced to mean 33 cm H(2)O (P=0.045).

CONCLUSIONS

The authors conclude that repeated conditional short duration electrical stimulation significantly increased cystometric capacity in patients with spinal cord injury. The increase was caused mainly by an inhibition of detrusor contractions. The need for a reliable technique for chronic bladder activity monitoring is emphasized, as it is a prerequisite for clinical application of this treatment modality.

Functional bladder capacity and urodynamics in males with nocturia

Previous studies in males with lower urinary tract symptoms (LUTS) have shown that nocturia in some patients is associated with nocturnal polyuria whereas other patients have preserved circadian urine output rhythm. This outpatient study based on 7-dayss frequency/volume (FV) charts showed that patients with nocturnal polyuria and age-matched controls without nocturia had a diurnal variation in functional bladder capacity (FBC) with higher night-time values. In contrast, patients without nocturnal polyuria no diurnal variation was observed in FBC with lower day and night-time values than both controls and nocturnal polyuric patients. Nocturia volumes correlated significantly to daytime FBC in both patient groups. Voided volumes obtained from daytime pressure/flow urodynamic investigations correlated significantly with night-time FBC obtained from the FV chart. In patients with LUTS nocturia was caused by nocturnal polyuria in 10 of 23 patients and by diminished night-time functional bladder capacity in the remaining 13 patients. In conclusion, nocturia in males with LUTS referred for BPH evaluation is caused by a mismatch between nocturnal urine production and night-time FBC analogous with the pathophysiology of nocturnal enuresis. The evaluation of circadian urine production and FBC seems mandatory in the assessment of patients with nocturia and LUTS.

Norepinephrine inhibits the pelvic pressure increase in response to flow perfusion

PURPOSE

We evaluated the effects of norepinephrine on transport pressures in the normal upper urinary tract of the pig during increasing perfusion rates.

MATERIALS AND METHODS

Anesthetized Danish landrace Yorkshire pigs weighing 38 to 40 kg were studied. Transparenchymally 2, 6Fr catheters were introduced into the left renal pelvis for pressure measurements and perfusion, respectively. An ultrasonic flow probe was inserted around the left renal artery to record blood flow. A 10Fr catheter was placed transurethrally for bladder drainage and the bladder was maintained empty during the entire study. In the 5 group 1 pigs the pelvic pressure increase was examined at increasing perfusion rates of the renal pelvis (2, 4, 6, 8, 10 and 15 ml per minute) in response to endoluminal administration of increasing concentrations of norepinephrine (0, 5, 50 and 100 microg/ml) in saline. In the 5 group 2 pigs the pressure flow study was also done 4 times per animal using isotonic saline.

RESULTS

Endoluminal norepinephrine had a dose dependent effect on the pressure flow relationship. Perfusion with 5 and 50 microg/ml norepinephrine caused a delayed increase and a decrease in pelvic pressure in response to increasing flow rates, whereas perfusion with 100 microg/ml norepinephrine significantly inhibited and almost eliminated the pressure increase at all perfusion rates compared with saline perfusion. Importantly there were no changes in blood pressure, the heart rate or renal arterial blood flow. In group 2 perfusion with isotonic saline resulted in the same pressure response to increasing flow rates each time.

CONCLUSIONS

Endoluminal administration of norepinephrine caused a dose dependent inhibition on the pressure phases of the pressure flow relationship of the upper urinary tract in pigs. No systemic changes were observed. These observations may provide a useful adjuvant treatment strategy for upper urinary tract stone treatment and endoscopy.

Quantitative assessment of Gd-DTPA contrast agent from signal enhancement: an in-vitro study

Quantitative determination of in-vivo gadolinium diethylenetriamine-pentaacid (Gd-DTPA) concentration is attractive in various studies involving perfusion, tracer kinetics and permeability constants. Using a 1.5 T clinical system and a 7 T small-bore system, we evaluated a method for absolute determination of Gd-DTPA concentrations in plasma solutions. Different solutions of Gd-DTPA and (99m)Tc-DTPA were mixed in human plasma and concentrations in the range of 0-5.0 mmol/l (1.5 T system) or 0-3.0 mmol/l (7 T system) of Gd-DTPA were divided into thirteen tubes. All MRI measurements were carried out using conventional sequences (SE, FLASH and GRASS). The MR measured intensity was converted to Gd-DTPA concentration by mathematical interpretation of the sequences. All MRI sequences showed, that the measured concentrations of Gd-DTPA revealed a slight non-linear difference compared with the calculated Gd-DTPA concentrations determined by the plasma (99m)Tc-DTPA using gamma counting. This non-linearity was most pronounced at high Gd-DTPA concentrations, suggesting that the discrepancy could be a result of an increased plasma relaxivity at higher concentrations. Adjustment of measured Gd-DTPA concentration was therefore performed using a selected power function, A[Gd-DTPA](a), which yielded the best linear relationship. Regression analysis showed that the scaling constant (A) varied from 0.11 to 97.45 and the power constant (a) varied from 0.83 to 1.6. Based on these constants, the MRI measured concentrations of Gd-DTPA did not differ from the calculated concentrations of Gd-DTPA obtained from reference measurements of (99m)Tc-DTPA. In the 1.5 T system, a linear relationship (r(2) > or = 0.95) was demonstrated in the range of 0-5.0 mmol/l Gd-DTPA, and in the 7 T system, a linear relationship (r(2) > or = 0.92) was demonstrated in the range of 0-3.0 mmol/l Gd-DTPA. Additionally, the effect of signal-to-noise on measured concentrations of Gd-DTPA was simulated using MR data of the mixed solutions of Gd-DTPA in plasma and the analytical expression of the pulse sequences. The simulations showed that the concentrations were most sensitive to noise in the GRASS sequence. In conclusion, this study demonstrates a novel approach to quantify accurately the Gd-DTPA concentration directly from MRI signal data using different routine sequences.

Bladder and urethral responses to pelvic nerve stimulation in the pig

OBJECTIVE

The aim of our study of the pig was to investigate the responses of smooth muscle of the bladder and the urethral sphincter to preganglionic parasympathetic stimulation, and to assess the effect on the lower urinary tract of IV administration of alpha,beta-methylene-ATP.

MATERIALS AND METHODS

In seven anaesthetised female pigs, the responses to repeated 20 s pelvic nerve stimulations before and after IV administration of 0.02 mg/kg alpha-beta-methylene-ATP, and the responses to the drug itself, were recorded in the bladder and the urethra separately.

RESULTS

In the urethral high-pressure zone, pre-stimulation pressure was a mean of 61+/-11 cmH2O. During pelvic nerve stimulation, urethral pressure declined by 48+/-9 cmH2O, while the bladder pressure increased to 30+/-18 cmH2O. The rate of pressure changes during the first 3 s of stimulation (initiation of voiding) was larger in the urethra than in the bladder (urethral pressure decrease: 13.0+/-3.1 cmH2O/s, bladder pressure increase: 3.2+/-2.5 cmH2O/s). Administration of alpha,beta-methylene-ATP was followed by a significant but temporary enlargement in the bladder response to pelvic nerve stimulation to 36+/-20 cmH2O, p = 0.028, n = 7, but no change in urethral response.

CONCLUSIONS

At least 80% of the urethral pre-stimulation pressure was exerted by the smooth muscle. The synergic activation of the detrusor and the urethral smooth muscle in response to preganglionic parasympathetic nerve stimulation was controlled by the peripheral nerves or by the neuromuscular transmission. Administration of alpha,beta-methylene-ATP increased the bladder response to pelvic nerve stimulation without changing the urethral response.

Contralateral response in renal pelvic pressure and diuresis during increasing ipsilateral pelvic pressure and flow: a study of the normal and denervated upper urinary tract in pigs

OBJECTIVE

To examine, in young pigs, changes in baseline pelvic pressure and diuresis in the contralateral kidney during conditions of increasing pelvic pressure and perfusion with isotonic saline in the ipsilateral renal pelvis; the role of a reno-renal nervous mechanism was examined by denervating the kidneys, and the effect of bladder filling on these variables assessed.

MATERIALS AND METHODS

Female pigs (37-40 kg) were assessed under general anaesthesia. Transparenchymally, one 6 F and two 6 F catheters were introduced into the right and left renal pelvis, respectively. Through a bladder incision an 8 F catheter was introduced 10 cm into the right ureter to collect urine and the orifice closed around the catheter. For bladder drainage and to measure bladder pressure a 10 F catheter was placed in the bladder and both the 8 F and 10 F catheters lead out through the urethra. In group A, five animals served as controls, with group B comprising eight with intact nerves and group C eight with denervated kidneys. In group B and C the left renal pelvis was perfused with isotonic saline at 2, 4, 6, 8, 10, 12 and 16 mL/min while the bilateral pelvic pressure and right renal diuresis were recorded; the bladder was kept empty and 0.5 h later the left pelvis was perfused with 10 mL/min while the bladder catheter was closed. Perfusion continued until micturition occurred. The bilateral pelvic pressure, bladder pressure and right renal diuresis were recorded. In group C the kidneys were surgically denervated, dividing all adhesions and all connective tissue around the pelvis and the vascular pedicle. The renal artery was freed to the aortic level.

RESULTS

During the pressure-perfusion study the mean (sd) right pelvic pressure was 7.4 (0.2) mmHg in group B and 8.6 (0.2) mmHg in group C. The diuresis from the right kidney in both groups was similar and the same as that in group A. The perfusion rate and pressure on the left side had no influence on pelvic pressure and diuresis on the right side. During perfusion with a full bladder the right pelvic pressure was 8.6 mmHg in group B and 9.5 mmHg in group C. Diuresis in group B was approximately 0.6 mL/min and a little higher in group C, at approximately 1 mL/min, but identical to that in group A.

CONCLUSION

These results indicate that a reno-renal reflex mechanism has no apparent role in young pigs during pressure-perfusion measurements with an empty or full bladder.

Renal water and sodium handling during gradated unilateral ureter obstruction

OBJECTIVE

Unilateral complete obstruction of the ureter (UUO) is associated with characteristic changes in renal function. To improve the understanding of how urine concentration directly is affected by changes in pelvic pressure, changes in renal salt and water handling along the nephron and collecting duct were examined.

MATERIAL AND METHODS

Pelvic pressure was raised stepwise using an adjustable lever inserted in the right ureter. Urine samples were collected from the tip of the catheter by way of an overflow system. Water and sodium handling in the distal and proximal tubules were measured by the lithium clearance technique. Renal blood flow (RBF) was measured with implanted ultrasonic flow probes. Catheters were placed in both renal veins and glomerular filtration rate (GFR) and filtration fraction were calculated using renal extraction of (51)Cr-EDTA independent of urine sampling.

RESULTS

The sequence of changes for each parameter is provided. The parameters did not show a uniform pattern from which specific threshold values could be derived. However, the mean value of the following parameters were markedly changed at specific pressures: (1) at 10 cm H(2)O ipsilateral urine output decreased rapidly and distal absolute reabsorption of sodium (DAR(H2O)) decreased, (2) at 20 cm H(2)O GFR started to decline rapidly, (3) at 30 cm H(2)O urine output was impaired, and (4) at 40 cm H(2)O proximal absolute reabsorption of water (PAR(H2O)) showed a decreasing tendency in all pigs together with impairment in tubular sodium handling. Furthermore, free water clearance was slightly impaired (-0.26 +/- 0.15 at baseline and -0.15 +/- 0.08 ml/min at maximum pressure) and ipsilateral RBF decreased from 171.1 +/- 12.4 ml/min at baseline to 136.3 +/- 12.3 ml/min at ureteral pressure of 80 cm H(2)O (p < 0.05). Consistent with that, ipsilateral renal vascular resistance increased with increasing pressure in the renal pelvis.

CONCLUSION

Water reabsorption and sodium handling is progressively impaired with increasing pelvic pressure. GFR and RBF are reduced in parallel. The study shows that the kidney responds to ureteral obstruction is unique and individual.

Long-term effects of partial unilateral ureteral obstruction on renal hemodynamics and morphology in newborn rats: a magnetic resonance imaging study

We assessed the longitudinal changes in renal vein blood flow (RVBF) and kidney volume in response to neonatally induced partial unilateral ureteral obstruction (PUUO) in rats with a magnetic resonance imaging (MRI) technique. During anesthesia, either the upper third or two thirds of the left ureter was embedded into the psoas muscle in newborn rats, creating either a mild (n=20) or a severe (n=9) partial obstruction. Control groups consisted of sham-operated (n=12) and non-operated (n=15) rats. During the following 24 weeks, RVBF and kidney volume were measured sequentially every 2-6 weeks with MRI, beginning 9 days after the operation. Both mild and severe obstruction caused a time-dependent decrease in RVBF. At week 24, the mean RVBF had decreased to 79% of the controls in the mildly obstructed kidneys (mean+/-SE: 1.45+/-0.14 vs 1.84+/-0.08 ml/min/100 g body weight, P<0.05) and to 57% of controls in the severely obstructed kidneys (1.05+/-0.10 vs 1.84+/-0.08 ml/min/100 g body weight, P<0.05). The renal pelvis volume increased and the renal parenchymal volume decreased significantly in the severely obstructed kidneys compared to the mildly obstructed kidneys. A good correlation was found between kidney volume measured in vivo using MRI and that measured in vitro (r>0.8, P<0.05), and between RVBF and renal parenchymal volume (r=0.758, P<0.01). In conclusion, the degree of reduction in RVBF depends on the severity and the duration of the PUUO. MRI can safely and reliably be used to monitor the longitudinal changes in RVBF and kidney volume in rats from early life.

Determining the displacement of the pelvic floor and pelvic organs during voluntary contractions using magnetic resonance imaging in younger and older women

OBJECTIVES

To: (i) visualize the effect of sustained voluntary contractions on the anatomical configuration of the pelvic floor (PF) muscles using magnetic resonance imaging (MRI); (ii) examine the effect of ageing on the range of displacement of the PF contents secondary to contraction and simulating incontinence exercises; and (iii) introduce the concept of contractile change in volume (DeltaPF-V) using three-dimensional (3D) reconstruction from axial, sagittal and coronal MRI.

SUBJECTS AND METHODS

Two groups of continent women volunteers, familiar with correct PF contraction, were evaluated. The mean (sd) age in group I was 34 (6) years and that of group II 55 (9) years; the mean parities were 0.7 and 2.2, respectively. MRI was conducted with the women supine and data were obtained in the axial, sagittal and coronal planes. In each plane, images were obtained with the PF relaxed and subsequently with the PF contracted over 10-20 s. Image processing was used to enhance the anatomical boundaries of the pelvic organs and to measure the displacement produced by the contraction. Displacements, observed between each image pair, were colour-coded to highlight the geometric differences between a relaxed and contracted PF and to facilitate measuring displacement. Data measured from each group were pooled and the range of motion expressed as the mean (sd), compared using Student's t-test.

RESULTS

Digitally processed imaging allowed an accurate comparison between the relaxed and contracted PF, and highlighted the differences between them. From these views, the levator ani displaced the vagina asymmetrically in nine of the 11 older subjects, and in six of the 17 younger subjects. The values from the imaging in the sagittal and coronal plane for the two groups were: levator ani displacement, 7.4 (1.1) and 1.4 (0.2) cm (P < 0.002), superior bladder wall, 4.2 (0.5) and 1.0 (0.1) cm (P < 0.002). There were also significant differences in the range of displacement produced by voluntary PF contraction in the internal structures; external outlines did not reflect these changes. The maximum displacement of the gluteal surface in the coronal plane did not change significantly; in group I it was 3.9 (1.8) to 2.9 (0.7) cm. From the 3D re-construction, DeltaPF-V for the younger women was significantly larger, at 23.3 (3.9) mL (P < 0.01) than in the older women, at 9.1 (4.4) mL. CONCLUCION: The range of motion over which voluntary PF contractions displace the bladder and vagina is age-dependent, being higher in younger than in older subjects. It remains to be established whether range of movement is a limitation caused by neuronal factors, decrease in muscle strength/mass, or the substitution of spaces with fat (restricting free movement), or other factors.

The relationship between desmopressin treatment and voiding pattern in children

OBJECTIVE

To collect data on voiding patterns at baseline (no treatment) and during short-term desmopressin treatment, with special reference to the functional and the mean bladder capacity.

PATIENTS AND METHODS

The study included 120 children (aged 6-16 years) with monosymptomatic nocturnal enuresis. While at home they recorded their fluid intake and diuresis in two separate periods, i.e. 2 weeks as a baseline registration and another 2 weeks during desmopressin titration. On four study days the children recorded the time and volume of all voids and of fluid intake. From the diaries their functional and mean bladder capacities, 24-h diuresis and day/night ratio of diuresis were determined.

RESULTS

The mean 24-h diuresis was significantly lower during short-term desmopressin treatment. In most of the enuretics the mean day/night ratio increased on desmopressin treatment. The mean functional and mean bladder capacities were unaffected by desmopressin. Those not responding had bladder capacities of approximately 100 mL less than full responders. Regardless of response, practically all the enuretics in the study had a smaller functional bladder capacity than expected for their age. Among responders the morning void was significantly larger than the following voids during the day, and among non-responders the fourth void was significantly larger than the previous voids in the day. Desmopressin treatment did not influence these volumes significantly.

CONCLUSIONS

Short-term desmopressin treatment does not affect functional and mean bladder capacity; 24-h urine production was reduced significantly (P<0.01) during desmopressin treatment.

Severe partial ureteric obstruction in newborn rats can produce renal dysplasia

OBJECTIVE

To investigate whether partial unilateral ureteric obstruction (PUUO) produces renal dysplasia in newborn rats.

MATERIALS AND METHODS

Left mild (in 31) or severe (in 34) PUUO was induced in 2-day-old rats by embedding a quarter or two-thirds of the ureter into the psoas muscles, respectively. Sham-operated control rats (36) were assessed in parallel. Kidney morphology, renal parenchymal weight and histology were examined 24 weeks and 30 months afterward.

RESULTS

There was significant pelvic dilatation in all obstructed kidneys; four kidneys were dysplastic in those severely obstructed, with a significant decrease in renal volume. There were three dysplastic kidneys after 6 months and one at 30 months. The in vitro dysplastic kidney weight was 36% of the control kidneys. Microscopy showed primitive glomerular and tubular structures, with renal parenchymal developmental disorganization and marked fibrosis. The glomeruli, tubules and collecting ducts were deficient in number and had often undergone cystic changes. Columnar tubular epithelium and peritubular mesenchymal collars were present. There was no renal dysplasia in the mildly obstructed and sham-operated rats. The parenchymal weight of the kidneys contralateral to the dysplastic kidneys was significantly higher than in the controls (P < 0.001).

CONCLUSIONS

Severe PUUO can produce renal dysplasia in newborn rats. However, only 12% with severe obstruction had renal dysplasia, indicating that the cause of renal dysplasia might also be related to other factors.