The role of manometry in the investigation of pelvi-ureteral function

Pressure matters: intrarenal pressures during normal and pathological conditions, and impact of increased values to renal physiology

PURPOSE

To perform a review on the latest evidence related to normal and pathological intrarenal pressures (IRPs), complications of incremented values, and IRP ranges during endourology.

METHODS

A literature search was performed using PubMed, restricted to original English-written articles, including animal, artificial model, and human studies. Different keywords were: percutaneous nephrolithotomy, PCNL, ureteroscopy, URS, RIRS, irrigation flow, irrigation pressure, intrarenal pressure, intrapelvic pressure and renal pelvic pressure.

RESULTS

Normal IRPs range from zero to a few cm H₂O. Pyelovenous backflow may occur at pressure range of 13.6-27.2 cm H₂O. During upper tract endourology, complications such as pyelorenal backflow, sepsis, and renal damage are directly related to increased IRPs. Duration of increased IRPs and concomitant obstruction are independent predictors of complication development.

CONCLUSIONS

IRP increase remains a neglected predictor of upper tract endourology complications and its intraoperative monitoring should be taken into consideration. Further research is necessary, to quantify pressures generated during upper tract endourology, and introduce means of controlling them.

Hydronephrosis by an aberrant renal artery: a case report

Ureteropelvic junction obstruction is usually intrinsic and is most common in children. Aberrant renal arteries are present in about 30% of individuals. Aberrant renal arteries to the inferior pole cross anteriorly to the ureter and may cause hydronephrosis. To the best of our knowledge, although there are some papers about aberrant renal arteries producing ureteropelvic junction obstruction, there is no report of a case which is diagnosed by the new modalities, such as computed tomography angiogram (CTA) or magnetic resonance angiogram (MRA). We describe a 36-year-old woman with right hydronephrosis. Kidney ultrasonogram and excretory urogram revealed right hydronephrosis. CTA and MRA clearly displayed an aberrant renal artery and hydronephrosis. The patient underwent surgical exploration. For the evaluation of hydronephrosis by an aberrant renal artery, use of CTA and MRA is advocated.

Crossing vessels. Endourologic implications

The controversy regarding the functional significance of vessels crossing at the ureteropelvic junction is not a new one, though this debate has been resurrected in recent years because of application of endourologic techniques to manage ureteropelvic junction (UPJ) obstruction. The principle limitation of endoscopic treatment of UPJ obstruction is the inferior success rate compared to open dismembered pyeloplasty. The influence crossing vessels may have in affecting both the success rates and complications of endoscopic treatment of UPJ obstruction has yet to be resolved. Crossing vessels may be important for two reasons: (1) they are a potential source of hemorrhage following endoscopic incision, and (2) they may play an etiologic role in UPJ obstruction and therefore may be a reason for failure of endoscopic techniques. This article reviews some of the historical aspects of crossing vessels and explores recent studies that are starting to shed some light on this controversial topic.

Vessels around the ureteropelvic junction: significance and imaging by conventional radiology

We studied the influence of vessels crossing the ureteropelvic junction and of the grade of hydronephrosis in 86 patients who underwent endoureteropyelotomy. With a follow-up ranging from 1 to 12 years, the presence of crossing vessels had a significant negative influence on the outcome and recurrence rate of the procedure. The success rate was 82% when no vessels were present but only 33% when crossing vessels were documented. In 13 of 15 failures (87%), a crossing vessel was found at open pyeloplasty. The degree of hydronephrosis was a less potent detrimental factor, with an 81% success rate in low-grade and 54% in high-grade hydronephrosis. The best results (90% success) were obtained in patients with no crossing vessels and low-grade hydronephrosis and the worst (30% success) in those with high-grade hydronephrosis in the presence of crossing vessels. Selection of patients according to those prognostic factors is recommended. Conventional intravenous urographic imaging techniques proved insufficient, and only angiography provided diagnostic accuracy; less-invasive methods are desirable.

Crossing vessels at the ureteropelvic junction: do they influence endopyelotomy outcome?

The majority of crossing vessels probably are inconsequential. Bleeding should not be a concern if the incision is made laterally. The optimal way to improve endopyelotomy results is to determine which crossing vessels truly are significant, and the authors describe the clinical trial that might be carried out to answer the question.

The effect of urinary flow and bladder fullness on renal pelvic pressure in a rat model

We describe an in vivo animal model used to study the interactions of urinary flow, and bladder pressure and fullness on renal pelvic pressure. These parameters were examined in 17 nonrefluxing Sprague-Dawley rats. At urinary flow rates less than 14 cc/kg. per hour and bladders less than 60% full, renal pelvic pressures were below 9 cm. water but at urinary flow rates more than 30 cc/kg. per hour renal pelvic pressure increased above 10 cm. water when the bladder was only 20% full. At all urinary flow rates examined renal pelvic pressure increased to more than 20 cm. water as the bladder approached 100% fullness. To quantitate the combined effects of these changes in renal pelvic pressure and urinary flow on the renal pelvis a renal pelvic work index (renal pelvic pressure times urinary flow rate) was defined. Using this index the magnitude of the change between low urinary flows with an empty bladder and high urinary flows with a full bladder can be observed. The results of these studies in this model might be applicable to high urinary flow states or bladders that fail to empty completely.

The effect of acute obstruction on ureteral function

In an effort to understand the physiologic processes which contribute to, or hinder the transport of stones through the ureter, we examined the intraluminal ureteral pressures and peristaltic activity above and below the acutely obstructed site. Because of patient differences, variability in stone size, shape and composition, an in vivo animal model was developed to study acute ureteral obstruction. Five adult mongrel dogs were anesthetized. A midline celiotomy was made and an open-ended ureteral catheter was inserted through a distal ureterotomy and advanced up the ureter. An angiographic balloon catheter was inserted through a small nephrotomy and directed down the ureter. The experiment was divided into phases: control, ureteral obstruction (balloon inflation) and release of obstruction (balloon deflation). Compared to control values, peristaltic rate above the obstruction increased significantly (p less than 0.05), as well as baseline, peak, and delta (peak minus baseline) pressures. In contrast, the peristaltic rate below the obstructed site remained approximately the same as its control, despite the significant decreases in baseline, peak, and delta (p less than 0.05) pressures. Failure of transmission of effective peristalsis across the obstructed site may hinder stone passage; however, this remains to be proven. Moreover, the failure of transmission of the increased rate of peristalsis past the balloon and persistence of peristaltic activity below the site of obstruction despite absence of urine flow suggest segmental forces influence peristaltic activity.

An experimental technique for renal intrapelvic access

This study describes an experimental technique for insertion of an indwelling cannula into the canine renal pelvis, and demonstrates its use in the measurement of pelviureteric pressure and motility, creatinine clearance, Whitaker tests, nephrostograms and nephrostomy drainage. The system, which consists of cannula, Heplock and plastic fixation disc, has been inserted into 53 canine kidneys (48) dogs, and percutaneous needle passage into the subcutaneously placed Heplock was used to gain access to the renal pelvis. This technique was successful in virtually all cases (131 separate procedures), and there were few complications. The indwelling intrapelvic cannula is a simple, cheap and reliable method of gaining longterm renal intrapelvic access in the dog, and has many experimental applications.

Mechanism of upper tract dilatation in patients with thick walled bladders, chronic retention of urine and associated hydroureteronephrosis

The mechanism of upper tract dilatation in patients with obstructive uropathy associated with thick walled trabeculated bladders and painless retention of urine has been determined in 9 cases by simultaneous measurement of renal pelvic and bladder pressures under baseline conditions and after administration of different stresses to the urinary tract. Under basal conditions no pelvic pressure increase was observed during detrusor contraction or other alteration of lower urinary tract pressure. However, after the flow in the upper tract was increased by oral water load, intravenous furosemide or direct pelvic perfusion, pelvic pressures were markedly elevated and reflected accurately any change in intravesical pressure. Under such conditions, pelvic pressures frequently exceeded 40 cm. water. These observations provide an explanation for the increasing size of the upper tract and a clarification of the mechanism whereby renal function might gradually deteriorate in these patients.

Tolerance to bilateral subcutaneous access nephrostomy in dogs

Subcutaneous nephrostomy is a technique which allows access to the renal pelvis for physiological study in the experimental animal over a prolonged period of time without the complications attendant upon an externally draining appliance. One end of an 8 Fr. polyvinyl tube was placed in the renal pelvis at open surgery and the other end was capped and buried in the subcutaneous space for subsequent access by percutaneous needle puncture. This procedure is preferable to surgically created vesical exstrophy, exteriorization of the renal pelvis or conventional nephrostomy, techniques which have been proposed for such purposes. Tolerance to subcutaneous access nephrostomy was investigated in a group of 10 dogs followed for periods ranging from six months to two years. It was found that bilateral subcutaneous access nephrostomy did not alter kidney function but was associated with altered peristalsis. It was also associated frequently with bacteriuria, but not pyelonephritis. Neither calcific deposits nor calculi were seen as a consequence of the tube, and the procedure was well tolerated by the animal although, in some, progressive weight loss was observed. In general, this technique proved to be an excellent procedure for prolonged physiological studies of the urinary tract in dogs, and might similarly find some clinical application in humans.

Effect of diuresis and glucagon on upper urinary tract dynamics in the dog

The effect of glucagon on upper urinary tract peristalsis during extreme diuresis was studied in an unsedated dog preparation. In all experiments glucagon inhibited the peristaltic contraction waves without affecting urine propulsion, suggesting that peristalsis, at least for short periods, is not necessary for effective urine transport during extreme diuresis.

Does perfusion equal diuresis in the upper urinary tract?

Pressures occurring in the upper urinary tract during perfusion and diuresis were compared in an unsedated dog preparation. Perfusion pressures were significantly higher, suggesting that a product of diuresis actively reduces upper tract tone.

Percutaneous upper urinary tract dynamics in equivocal obstruction

Percutaneous pressure flow studies in the upper urinary tract remain the definitive method of distinguishing stasis from obstruction. They are not technically difficult and the results of 2 large series show minimal, minor complication rates. The results in over 200 studies show that a clear-cut answer as to whether or not an obstruction is present is obtained in over 95% of patients, the remainder showing pressures in an equivocal range.

Pressure flow studies in hydronephrosis

44 patients with idiopathic hydronephrosis underwent intrapelvic pressure flow studies. An increased basal pressure and an increased pressure during flow loading were found compared with the findings in 10 control kidneys. The method is relatively easy to perform and has few complications. It may be of value in determining the degree of obstruction in equivocal cases of dilated pelvis.

Urodynamic investigation of the wide ureter

Pressure flow studies constitute a valuable advancement in the investigation of wide ureters without reflux. However, these studies do not in themselves allow the determination of the adequacy of urine transport into the bladder. Radiological examination during perfusion is necessary to assess peristalsis and antiperistalsis, to determine the outflow to the bladder and to judge the geometric changes. Case studies reveal that it is difficult to assess the outflow to the bladder from measurements of renal pelvic pressure and of inflow.

What is a urodynamics study of upper urinary tract?

The urodynamic study of the upper urinary tract is a urologic procedure whose objective is to complement the information obtained by excretion urography in selected cases of documented or suspected upper tract obstruction. The procedure has several steps, all of which can be done by antegrade transcutaneous puncture of the kidney. The first and most important step consists of the simultaneous analysis of resting pelvic pressure, solute concentration in aspirated urine from the renal pelvis, and antegrade pyelogram. This set of data makes up the basic urodynamic evaluation and will be sufficient in many cases for diagnostic and prognostic purposes. However, in selected circumstances of equivocal dilatation or severe kidney atrophy, more complementary information can be gained using antegrade flow studies or temporary diversion by needle nephrostomy, respectively. These conclusions have been based on more than 300 urodynamic evaluations done by the author.

Maximum urinary concentration ability in patients with idiopathic hydronephrosis

The maximum urinary concentration ability and renal parenchymal function of each kidney were investigated in 34 patients with unilateral hydronephrosis. The ability to concentrate urine was not reduced in 10 hydronephrotic and 24 contralateral kidneys. The concentration ability was moderately reduced in 14 hydronephrotic and 10 non-hydronephrotic kidneys and severely impaired in 10 hydronephrotic kidneys. A reduced concentration ability was found almost entirely in hydronephrosis complicated with upper urinary tract infection or renal calculi. Hydronephrotic kidneys without these complications showed a normal concentration ability in 10 of 11 cases. Parenchymal function was reduced in only 10 hydronephrotic kidneys, 7 of which had had upper urinary tract infections and 3 of which had renal stones. It is our opinion that uncomplicated cases of unilateral hydronephrosis should not be operated upon unless necessitated by signs and symptoms. Measurement of the maximum urinary concentration ability might be helpful in setting the correct indication for surgery in borderline cases.

The renal pelvis and ureteral peristalsis. I. Pelveometry

The renal pelvis is a visco-elastic organ and serves the double purpose of acting as a pump function and a reservoir. With a "pig-tail" catheter ("William Cook Europe" aps, Søborg, Denmark), placed transrenally in the canine pelvis and external blocking of the pelveoureteral junction, it is possible to change the volume of the canine renal pelvis and register the resulting pelvic pressure. This examination is called pelveometry. In 24 adult, female dogs pelveometry showed a linear relation within the range of 0-5.5 ml and 1-30 mmHg, respectively. The correlations between the measurements and the estimated lines were about or more than 90%. The registrations during increasing and the following decreasing volume change showed different values and another linearity of 50% of the assays. This observation demonstrated the occurrence of hysteresis (c: a viscoelastic reaction of the smooth muscle tissue) and is in accordance with findings in previous investigations of other smooth muscle organs. The linearity within physiological ranges of the two pelvic parameters indicates that the pelvic pressure and the frequency of ureteral peristalsis will be sufficient to describe the urodynamic patterns of the canine upper urinary tract.