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Clinical assessment of pelvic and ureteral function
CLINICAL ASSESSMENT
OF PELVIC
AND URETERAL FUNCTION ROBERT
H. WHITAKER,
From the Department Cambridge, England
hl.&IR.,
of Urology,
The purpose of this article is to help the clinician to decide whether or not a11 abnormally wide upper urinary tract requires surgery. In the majority of patients this decision is not difficult since the standard methods of evaluation available to the urologist are both sophisticated and accurate. However, in any busy urologic service there are perhaps 20 or 30 cases each year in which the decision cannot be made by these standard methods alone. In pediatric urology these difficult cases are more plentiful. The Problem The most common problem is the patient who is found by radiolom to have a wide ureter or large renal pelvis. Micturating cystography excludes ureterovesical reflux, and it is assumed that an obstruction is present. A reimplantation or pyeloplasty is performed, but repeat radiographic studies postoperatively are clisappointing at best or tragic at worst. If the operation is not perfect, the previously wide and nonobstructed system may be converted into an obstructed or refluxing one. The implications of performing such an unnecessary or even harmful operation are obvious. This mistake is made because of the long-standing and misguided belief that all nonrefluxing, wide systems are obstructed. Of course, many may well have been obstructed previously and, undoubtedly, the postobstructive dilatation after relief of obstruction is among the most difficult In this category are the situations to assess. patients with grossly dilated ureters or renal pelves after reimplantation or pyeloplasty, particularly in the presence of a poorly excreting kidney. Also, and perhaps the most difficult a 11d contro\,ersial of all, are boys who have dilated ureters after destruction of posteriol urethral valves.
F.R.C.S. Addenbrooke’s
Hospital,
Dynamic and pathophysiologic studies of the ripper tract are of great research interest, but from a clinical point of view there are only two decisions to be made. First, is there an obstruction which if relieved would lead to better drainage and less pressure on the nephrons? Second, if it is not obstructed, is there anything that can be done to stop recurrent or persistent infection by reducing the volume of the upper tract? This is with the understanding that in the absence of intrinsic renal disease there are only two f:,lctors, infection and obstruction, which can harm the kidney. Obstruction must be diagnosed as early as possible to allow the kidneys to function can be optimally. Stasis, without obstruction, improved surgically by reductive or reconstructive procedures such as extensive tapering, but equally the infection caused by stasis alone can often be treated readily with antibiotics; this should be tried before offering the patient an operation since ureteric surgery can be fraught with complications. hlethods
of Assessing
Obstruction
The shortcomings of commonl~~ llsed methods of assessing obstruction ha\re been discussed in other publications. ‘,* Suffice it to say that urography, ureterography, renography, or even operative exploration, either singly or in combination, can fail to give a definite answer in a relatively small group of patients with equivocal obstruction. The patient’s symptwns, although usually an important factor in the clecision, can also lx misleading. A patient with backache, fol instance, may be found to have an enlarged renal pelvis, and the symptoms may be too easil? and perhaps wrongly attributed to this finding. If obstruction is correctly defined in dynamic terms as a situation in which there is a
FIGURE 1. (‘4 1 Intraoenous urogram of forty-jiue-yearold mun with slight. proteinuria on one o( casion. wide spindle in lower right ureter with loss of calycecd cupping. (B) X-ray film during perfusion ut 10 mi. per minute and relatizre prc.ssure of only 4 cm. water; despite radiographic nppearunces this is unobstructed .qstem. higher than normal renal pelvic prc’ssure togcthvrIvith a normal or reduced urine flo~v rate, it is obvious why radiographic studies will never provide an entirely objective assessment. It is essential to know the flow and pressure, and that is why dynamic assessment is needed. The two methods to be discussed here are radiographic and urodynamic, but this is not to ha). that other methods are unworthy of conyideration.
There is little difficulty in interpreting the signs of an acute obstruction on x-ray film. A prolonged nephrogram with delayed emptying from a dilated pelvis or ureter leaves little cloubt, particularly if the patient’s symptoms match these signs. In the more chronic situation there ma). also be a negative pyelogram and ~al~~ct~al crcascc>nts in the earlv films. A more c&~f~ll anal! sis shows that, in iact, any of these occursin the absence of obstruction signs cm 5r1ch as the prolonged nephrogram of acute tubular necrosis or sudden hypotension, the delu~~~tl nreteric or pelvic emptying in massively dilated bllt nonobstructed systems with stasis, and tllca ncagative pyelogram and crescents which art’ oftran se*11 after relief of obstruction. in the majority of obstructions Ho\\.e\.cbr. III the difficult these signs (*an be relied upon. C’;W~Sof ecluivocal obstruction it is not the radiographic* studies themselves which are at fault but often our inability to draw the corrtact c*onclllsioils from them. -411 c~xampl~ of this is the phenomenon of rotrogrtldc ~)~v-i,st&s which is not infrequentl!, 4ccn irr ;i wide ureter, particularly in the segIncntal or lo\vrr spindle type of megauretel
(Fig. 1). It is not uncommon to find that a good occlusive wave propels a bolus in to this lower ureteric segment which is wider than normal. No further bolus is formed, bllt the wave passes down the walls of the segment until it reaches the ureteric orifice or the short length of normal caliber ureter just above it. The wave then reverses and passes back ~113 over the wide segment and for a short distance into the normal-sized ureter above. At some stage cluring this activity a small amount of fluid is expelled into the bladder probably not so much by the peristaltic action as by the general rise in the intraluminal pressure caused by the addition of the bolus to this wide segment. Although this phenomenon may occur in obstructed ureters, I have seen it frequently in rlnobstructed ones and am convincxed that it is not synonymous with obstruction. dilatution is a vexing and controCalyceal versial topic. Such conditions as megacalycosis. papillary necrosis, and postobstruc+ve atroph?, make it obvious that there can he considerable calyceal change in the absence of’ obstruction. It is perhaps more difficult tc.1 accept that a degree of obstruction can be prYsent with neal normal call-ces (Fig. 2). A radiologic sign much mentioned in equivocal pelviureteric obstruction is the ability 01 filling in urogram inability to show ureteric films. If the kidney continues to t;mction, the ureter, clearly. must fill from time to time and our ability to see this on single films must depend on the timing of the fihns The arglnnent ww-ks against us both ways hen:~. If the nrete1 fills well, it is tempting to say t.hat obstruction cannot be present. This is, of c(nuse, quite erroneous as illustrated in Figure 2 and in
urogram of ten-year-old girl with FIGURE 2. (A) Intravenous two attacks of urinary tract infection showing good calyces and ureteric filling. (B) Percutaneous pressure&low study sho wing relative pressure across pelviureteric junction of 27 cm. u9ater sy stem at 10 ml. per minute. This was deemed an obstructed despite normal calyces, and pyeloplasty was performed.
FIGURE 3. lntravenous urogram of fifty-four-year-old attack of right subcostal pain: (A) supine, (B) prone pressuredof only 2 cm. water at 10 ml. per minute:
woman position.
many other cases I have studied. The filling is at the expense of a higher than normal pelvic pressure. Conversely, there may be deceptively little ureteric filling on single films with the patient supine but a prone exposure may show good filling (Fig. 3). Thus the readiness of the ureter to be shown full and the morphology of the calyces must, like all other radiographic signs of obstruction, be interpreted carefully and in the light of the entire clinical situation.
last ten years it is surprising that little attention has been paid to the clinical application of dynamics to the upper tract. Studies by Johnston3 and Backlund and Reuterskiold4 using perfusion and pressure measurement in the renal pelvis and ureter led the way to our present method of assessing obstruction by dynamic means. The principle upon which these studies is based is that an abnormally high pressure in the pyelocalyceal system impairs the function of the nephrons, and has been clearly demonstrated by Schweitzer.” However, what is not yet entirely clear is how raised the pressure must be before renal damage is inevitable. What is certain is that pressures will be maximal during a high fluid load; h ence the need to measure
With the amount of interest dynamics of the lower urinary
148
shown in the tract over the
UROLOGY
with historu of recurrent cystitis and one Later percutaneous study showed relative
i AUGUST1978
/ VOLUME
SII~NCMBERZ
the prt’sslire under a high diuretic stress or during a perfusion. Static pressures without the knowledge of the flow rate are useless and misleading. The interpretation of pressure levels remains speculative since it is not difficult to envisage a situation ilk which a kidney with reduced cortical thickness and dilated calvces is shown to have a slightI,. raised pressure, as defined helou, 11:~ this renal damage been cxused 11) these marginally raised pressures over a period of >‘ears. or are the pressures now lower than the), had been previously, perhaps because of
growth of the system with resulting increase in the diameter of the narrowest point? At the present time these questions remain 11nanswered
hut
fortunately
detract
only
a little
from the olnious clinical advantage of having an objective method of assessing obstruction. Technique The pressllreiflow study described in I973 has not been significantly modified and continues to 1~ used rolltinely as part of a busy clinical practice. ‘.’ Details of the test and the required equipment have been described.“,’ Although access to the renal pelvis is easil>obtained via a nephrostomy tulle or 1)~ direct puncture at operation, the most advantageous rollte is 1)~. percutaneous puncture so that a decision can 1~ made which will influence whether or not an operation is necessary. Under fluoroscopic control a needlen1ountc.d cannula (Longdwel size 4 or 6 inches. 18 gauge) is passed into the pyelocalyceal system. preferably \ia the renal substance so that a watertight seal is obtained. A transducer and recording apparatus is attached to the cannulu through which saline or contrast medium is infused at a fised kno\vn flow rate. The pressure reference point is the level of the kidney outside the l,ocl)-. It is important, also, to record the bladder pressure intermittentl>. or continuously during the
prowdure
so that
the
renal
pelvic
pressure
can 1~1 interpreted in terms of ureterovesical 01 1)ladder outflow obstruction. This will be discussed later. A small urethral catheter is passed I)efore tht, l)ercutaneolls procedure is Imdertaken. Princtilring a small renal pelvis or calj-x is not ahvays a simple matter, but most radiologists are no\\’ espert in this type of procedure and tlicir
cooptwtion
is essential.
Perfusion is continued lintil the prtJssiirf> becomes steady or rises so high that the systeln clearly \vill not tolerate a high flow. rattb. ‘l’hr procedure has lxcome take only
is then complete. \\‘l~m a routine established, the entire stud\ need thirty to forty-fit-t, Ininutes. AII
anesthetic is necessary 1,111).in some vourkg children. Other patients ma\~ need iIltra\ enous or oral sedation, brat it is essential to have the patient’s full cooperation since a (lazed or (*onfused state is Ilnsatisfactorv. Interpretation
of Results
The final eqllilibrated pres,surtb whic>h is recorded is a compound pressure produ<,ed 1,~. several factors: (1) pressure within the renal pelvis at the flow rate used; (2) l>res5iir(l produced 11~ perfusing the cannuLl; St excrt+ion pressure from the nephrons; and (4) prt’ssllrtl from the intra-abdominal contents I intestines, etc.). So that the results
from patient to patient call be compared, it is convenient to express the final pressures in two ways. Initially. the prtlssurt produced by perfusion of the cal~nula at the known flow rate is subtracted (this can be reproduced either hefore or after the qtlld\ away from the patient); this I term thy nbwlz& pressure. If the bladder pressure is also subtracted there are two further ad\,antages: First, with the patient lving down the rt,cting prt~ssure in the empty bladder approximatt.*s the intraabdominal pressure and if this is subtracted. its effects on the renal pelvis c.:m be ignored. Second, subtraction of the bladder presstire pwssuw. or a pressure drop gives a t-dative across the site of suspected 0lMri~ction which lies between the renal pelvis and the l,ladder. Further information is c.)l)taine(l if‘the bladder is allowed to fill via the perfimxl ureter. If the l~laclder pressure rises or shows olnious signs of uninhibited contractions, the efkt of this 011 the iippyr tract pressures can I)tb ol)served. However high the bladder pressure rises the difference hetwcen it a11d the I (*11al pelvic pressure still represents the rrvistarlc:ta of the rlrt~terovc5ic21 junction (or pel\~iiireteric ,jiinction in the case of a hydronephrosis). This rdatizrc prcssurc illay increase with l~laclder filling
5riggesting a change in the morph~~log~ of thte Ilretero\.esicA junction -- perhaps l)ecalLse of the distortion 1)~ the exI)anding, l~laclder wall. Sometimes this rchtice prcssuro irrc~rt~ase~t‘\.en though the hladder pressllre itstslf’ rt~nrains low
TABLE
Comment
I. One hundred seventy studies in 112 patients
Condition Wide ureters Primary Secondary After reimplantation Hydronephrosis New cases Previously operated Induced by reflux After stone removal Retroperitoneal fibrosis Hydrocalycosis Megacalycosis Ureterocolic anastomosis Refluxing ureters with obstruction Transureteroureterostomy Indefinite ureteric obstruction
Number 33 18 17 62 9 2 6 6 1 4 1
7 1
3
throughout. This indicates a change in the mechanical nature of the orifice without hypertonicity of the bladder. In the case of a wide ureter knowledge of the absolute and relative pressures is decisive in determining whether the obstruction is at the ureterovesical junction or at the bladder neck, or at both sites; thus the correct operative decision can be made. It avoids the possibility of reimplantation of the ureter when what is really needed is an attack on the bladder neck or other aspects of the outflow tract. These studies have allowed a much more logical approach to the management of megaureters of all types and to the large ureters which present a problem in boys who have had resection of posterior urethral valves. I have considered a relative pressure of up to I2 cm. water as normal at the high flow rate of 10 ml. per minute. This is on the basis of many studies in seemingly unobstructed systems. It is difficult to interpret the significance of a pressure of, say, 15 to 18 cm. water at this flow rate and to determine at what level an operation is necessary. However, in my opinion it appears probable that pressures over 20 cm. water warrant relief of obstruction. It is significant that after a pyeloplasty the pressures are usually less than 12 cm. water.’ A high flow is necessary to stress the system maximally; 10 ml. per minute is well within the physiologic range, but 5 or 2 ml. per minute can be substituted and the pressures then observed at these rates.
150
To summarize the results of the studies performed is difficult since each study has been a complete investigation in reference to each individual patient. The conditions studied are shown in Table I. Many results have influenced our clinical decisions in a direction different from that which would have been taken had no study been available. Mostly this has meant that unnecessary operations have been avoided; however in a few younger patients higher pressures have been found and operations have been performed where we might otherwise have been tempted to procrastinate and do repeat radiographic or serial studies of renal function. We have seen patients with gross calyceal clubbing and no obstruction and others with minimal changes but with higher than normal pressures. Because of these findings we are now more wary in our interpretation of the radiographic findings and are resorting to dynamic studies more and more. These studies call for a degree of organization within the department and take up a little time, but we believe it is time well spent; and if they save an unnecessary operation or prevent the time and expense of repeated radiographic studies then surely they are worthwhile. Morbidity is low. We have frequently encountered minimal hematuria, but this never has been of serious consequence. A careless puncture once caused peritonism which quickly resolved, but this should easily be avoided. We have only recorded 1 case oi urinary infection attributable to this procedure. This dynamic approach can be recommended for the difficult diagnostic problem when other methods of assessment have failed. Cambridge,
1. \Vhitaker RH: Diagnosis of obstruction Ann. R. Coil. Surg. Engl. 53:153(1973). 2. IDEM: Thr ureter in posterior urethral
England
in dilated uwters.
valvrs, Br. J. LTrol. 45: 395 (1973). 3. Johnston JH: The pathogenesis of hvdroneplrrosi, in children, ibid. 41: 724 (1969). 4. Backlund L, and Reuterskiold AG: Thv abnormal ureter in children. 1. Perfusion studies on the wide non-wfluxing Imeter, Stand. J. Ural. Nephrol. 3: 219 (1969). 5. Schweitzer FAW: Intrapc~lvic pr~ssuw and rwral frmrtion studies in experimmtal chronic partial ut’rteric ot,atruction. Br. J. Crol. 45: 2 (1973). 6. Whit&r RH: Methods of sssesing obstruction in dilntryl uretrrs. ihid. 45: 15 (1973). 7. IDEM: Equivocal pelviureteric olxtruction, i/kc/. 47: 771 (1976).
UROLOGY
/
AUGUST
1978
i
VOLUME
XII. \JI-XIREH
2
OF PELVIC
AND URETERAL FUNCTION ROBERT
H. WHITAKER,
From the Department Cambridge, England
hl.&IR.,
of Urology,
The purpose of this article is to help the clinician to decide whether or not a11 abnormally wide upper urinary tract requires surgery. In the majority of patients this decision is not difficult since the standard methods of evaluation available to the urologist are both sophisticated and accurate. However, in any busy urologic service there are perhaps 20 or 30 cases each year in which the decision cannot be made by these standard methods alone. In pediatric urology these difficult cases are more plentiful. The Problem The most common problem is the patient who is found by radiolom to have a wide ureter or large renal pelvis. Micturating cystography excludes ureterovesical reflux, and it is assumed that an obstruction is present. A reimplantation or pyeloplasty is performed, but repeat radiographic studies postoperatively are clisappointing at best or tragic at worst. If the operation is not perfect, the previously wide and nonobstructed system may be converted into an obstructed or refluxing one. The implications of performing such an unnecessary or even harmful operation are obvious. This mistake is made because of the long-standing and misguided belief that all nonrefluxing, wide systems are obstructed. Of course, many may well have been obstructed previously and, undoubtedly, the postobstructive dilatation after relief of obstruction is among the most difficult In this category are the situations to assess. patients with grossly dilated ureters or renal pelves after reimplantation or pyeloplasty, particularly in the presence of a poorly excreting kidney. Also, and perhaps the most difficult a 11d contro\,ersial of all, are boys who have dilated ureters after destruction of posteriol urethral valves.
F.R.C.S. Addenbrooke’s
Hospital,
Dynamic and pathophysiologic studies of the ripper tract are of great research interest, but from a clinical point of view there are only two decisions to be made. First, is there an obstruction which if relieved would lead to better drainage and less pressure on the nephrons? Second, if it is not obstructed, is there anything that can be done to stop recurrent or persistent infection by reducing the volume of the upper tract? This is with the understanding that in the absence of intrinsic renal disease there are only two f:,lctors, infection and obstruction, which can harm the kidney. Obstruction must be diagnosed as early as possible to allow the kidneys to function can be optimally. Stasis, without obstruction, improved surgically by reductive or reconstructive procedures such as extensive tapering, but equally the infection caused by stasis alone can often be treated readily with antibiotics; this should be tried before offering the patient an operation since ureteric surgery can be fraught with complications. hlethods
of Assessing
Obstruction
The shortcomings of commonl~~ llsed methods of assessing obstruction ha\re been discussed in other publications. ‘,* Suffice it to say that urography, ureterography, renography, or even operative exploration, either singly or in combination, can fail to give a definite answer in a relatively small group of patients with equivocal obstruction. The patient’s symptwns, although usually an important factor in the clecision, can also lx misleading. A patient with backache, fol instance, may be found to have an enlarged renal pelvis, and the symptoms may be too easil? and perhaps wrongly attributed to this finding. If obstruction is correctly defined in dynamic terms as a situation in which there is a
FIGURE 1. (‘4 1 Intraoenous urogram of forty-jiue-yearold mun with slight. proteinuria on one o( casion. wide spindle in lower right ureter with loss of calycecd cupping. (B) X-ray film during perfusion ut 10 mi. per minute and relatizre prc.ssure of only 4 cm. water; despite radiographic nppearunces this is unobstructed .qstem. higher than normal renal pelvic prc’ssure togcthvrIvith a normal or reduced urine flo~v rate, it is obvious why radiographic studies will never provide an entirely objective assessment. It is essential to know the flow and pressure, and that is why dynamic assessment is needed. The two methods to be discussed here are radiographic and urodynamic, but this is not to ha). that other methods are unworthy of conyideration.
There is little difficulty in interpreting the signs of an acute obstruction on x-ray film. A prolonged nephrogram with delayed emptying from a dilated pelvis or ureter leaves little cloubt, particularly if the patient’s symptoms match these signs. In the more chronic situation there ma). also be a negative pyelogram and ~al~~ct~al crcascc>nts in the earlv films. A more c&~f~ll anal! sis shows that, in iact, any of these occursin the absence of obstruction signs cm 5r1ch as the prolonged nephrogram of acute tubular necrosis or sudden hypotension, the delu~~~tl nreteric or pelvic emptying in massively dilated bllt nonobstructed systems with stasis, and tllca ncagative pyelogram and crescents which art’ oftran se*11 after relief of obstruction. in the majority of obstructions Ho\\.e\.cbr. III the difficult these signs (*an be relied upon. C’;W~Sof ecluivocal obstruction it is not the radiographic* studies themselves which are at fault but often our inability to draw the corrtact c*onclllsioils from them. -411 c~xampl~ of this is the phenomenon of rotrogrtldc ~)~v-i,st&s which is not infrequentl!, 4ccn irr ;i wide ureter, particularly in the segIncntal or lo\vrr spindle type of megauretel
(Fig. 1). It is not uncommon to find that a good occlusive wave propels a bolus in to this lower ureteric segment which is wider than normal. No further bolus is formed, bllt the wave passes down the walls of the segment until it reaches the ureteric orifice or the short length of normal caliber ureter just above it. The wave then reverses and passes back ~113 over the wide segment and for a short distance into the normal-sized ureter above. At some stage cluring this activity a small amount of fluid is expelled into the bladder probably not so much by the peristaltic action as by the general rise in the intraluminal pressure caused by the addition of the bolus to this wide segment. Although this phenomenon may occur in obstructed ureters, I have seen it frequently in rlnobstructed ones and am convincxed that it is not synonymous with obstruction. dilatution is a vexing and controCalyceal versial topic. Such conditions as megacalycosis. papillary necrosis, and postobstruc+ve atroph?, make it obvious that there can he considerable calyceal change in the absence of’ obstruction. It is perhaps more difficult tc.1 accept that a degree of obstruction can be prYsent with neal normal call-ces (Fig. 2). A radiologic sign much mentioned in equivocal pelviureteric obstruction is the ability 01 filling in urogram inability to show ureteric films. If the kidney continues to t;mction, the ureter, clearly. must fill from time to time and our ability to see this on single films must depend on the timing of the fihns The arglnnent ww-ks against us both ways hen:~. If the nrete1 fills well, it is tempting to say t.hat obstruction cannot be present. This is, of c(nuse, quite erroneous as illustrated in Figure 2 and in
urogram of ten-year-old girl with FIGURE 2. (A) Intravenous two attacks of urinary tract infection showing good calyces and ureteric filling. (B) Percutaneous pressure&low study sho wing relative pressure across pelviureteric junction of 27 cm. u9ater sy stem at 10 ml. per minute. This was deemed an obstructed despite normal calyces, and pyeloplasty was performed.
FIGURE 3. lntravenous urogram of fifty-four-year-old attack of right subcostal pain: (A) supine, (B) prone pressuredof only 2 cm. water at 10 ml. per minute:
woman position.
many other cases I have studied. The filling is at the expense of a higher than normal pelvic pressure. Conversely, there may be deceptively little ureteric filling on single films with the patient supine but a prone exposure may show good filling (Fig. 3). Thus the readiness of the ureter to be shown full and the morphology of the calyces must, like all other radiographic signs of obstruction, be interpreted carefully and in the light of the entire clinical situation.
last ten years it is surprising that little attention has been paid to the clinical application of dynamics to the upper tract. Studies by Johnston3 and Backlund and Reuterskiold4 using perfusion and pressure measurement in the renal pelvis and ureter led the way to our present method of assessing obstruction by dynamic means. The principle upon which these studies is based is that an abnormally high pressure in the pyelocalyceal system impairs the function of the nephrons, and has been clearly demonstrated by Schweitzer.” However, what is not yet entirely clear is how raised the pressure must be before renal damage is inevitable. What is certain is that pressures will be maximal during a high fluid load; h ence the need to measure
With the amount of interest dynamics of the lower urinary
148
shown in the tract over the
UROLOGY
with historu of recurrent cystitis and one Later percutaneous study showed relative
i AUGUST1978
/ VOLUME
SII~NCMBERZ
the prt’sslire under a high diuretic stress or during a perfusion. Static pressures without the knowledge of the flow rate are useless and misleading. The interpretation of pressure levels remains speculative since it is not difficult to envisage a situation ilk which a kidney with reduced cortical thickness and dilated calvces is shown to have a slightI,. raised pressure, as defined helou, 11:~ this renal damage been cxused 11) these marginally raised pressures over a period of >‘ears. or are the pressures now lower than the), had been previously, perhaps because of
growth of the system with resulting increase in the diameter of the narrowest point? At the present time these questions remain 11nanswered
hut
fortunately
detract
only
a little
from the olnious clinical advantage of having an objective method of assessing obstruction. Technique The pressllreiflow study described in I973 has not been significantly modified and continues to 1~ used rolltinely as part of a busy clinical practice. ‘.’ Details of the test and the required equipment have been described.“,’ Although access to the renal pelvis is easil>obtained via a nephrostomy tulle or 1)~ direct puncture at operation, the most advantageous rollte is 1)~. percutaneous puncture so that a decision can 1~ made which will influence whether or not an operation is necessary. Under fluoroscopic control a needlen1ountc.d cannula (Longdwel size 4 or 6 inches. 18 gauge) is passed into the pyelocalyceal system. preferably \ia the renal substance so that a watertight seal is obtained. A transducer and recording apparatus is attached to the cannulu through which saline or contrast medium is infused at a fised kno\vn flow rate. The pressure reference point is the level of the kidney outside the l,ocl)-. It is important, also, to record the bladder pressure intermittentl>. or continuously during the
prowdure
so that
the
renal
pelvic
pressure
can 1~1 interpreted in terms of ureterovesical 01 1)ladder outflow obstruction. This will be discussed later. A small urethral catheter is passed I)efore tht, l)ercutaneolls procedure is Imdertaken. Princtilring a small renal pelvis or calj-x is not ahvays a simple matter, but most radiologists are no\\’ espert in this type of procedure and tlicir
cooptwtion
is essential.
Perfusion is continued lintil the prtJssiirf> becomes steady or rises so high that the systeln clearly \vill not tolerate a high flow. rattb. ‘l’hr procedure has lxcome take only
is then complete. \\‘l~m a routine established, the entire stud\ need thirty to forty-fit-t, Ininutes. AII
anesthetic is necessary 1,111).in some vourkg children. Other patients ma\~ need iIltra\ enous or oral sedation, brat it is essential to have the patient’s full cooperation since a (lazed or (*onfused state is Ilnsatisfactorv. Interpretation
of Results
The final eqllilibrated pres,surtb whic>h is recorded is a compound pressure produ<,ed 1,~. several factors: (1) pressure within the renal pelvis at the flow rate used; (2) l>res5iir(l produced 11~ perfusing the cannuLl; St excrt+ion pressure from the nephrons; and (4) prt’ssllrtl from the intra-abdominal contents I intestines, etc.). So that the results
from patient to patient call be compared, it is convenient to express the final pressures in two ways. Initially. the prtlssurt produced by perfusion of the cal~nula at the known flow rate is subtracted (this can be reproduced either hefore or after the qtlld\ away from the patient); this I term thy nbwlz& pressure. If the bladder pressure is also subtracted there are two further ad\,antages: First, with the patient lving down the rt,cting prt~ssure in the empty bladder approximatt.*s the intraabdominal pressure and if this is subtracted. its effects on the renal pelvis c.:m be ignored. Second, subtraction of the bladder presstire pwssuw. or a pressure drop gives a t-dative across the site of suspected 0lMri~ction which lies between the renal pelvis and the l,ladder. Further information is c.)l)taine(l if‘the bladder is allowed to fill via the perfimxl ureter. If the l~laclder pressure rises or shows olnious signs of uninhibited contractions, the efkt of this 011 the iippyr tract pressures can I)tb ol)served. However high the bladder pressure rises the difference hetwcen it a11d the I (*11al pelvic pressure still represents the rrvistarlc:ta of the rlrt~terovc5ic21 junction (or pel\~iiireteric ,jiinction in the case of a hydronephrosis). This rdatizrc prcssurc illay increase with l~laclder filling
5riggesting a change in the morph~~log~ of thte Ilretero\.esicA junction -- perhaps l)ecalLse of the distortion 1)~ the exI)anding, l~laclder wall. Sometimes this rchtice prcssuro irrc~rt~ase~t‘\.en though the hladder pressllre itstslf’ rt~nrains low
TABLE
Comment
I. One hundred seventy studies in 112 patients
Condition Wide ureters Primary Secondary After reimplantation Hydronephrosis New cases Previously operated Induced by reflux After stone removal Retroperitoneal fibrosis Hydrocalycosis Megacalycosis Ureterocolic anastomosis Refluxing ureters with obstruction Transureteroureterostomy Indefinite ureteric obstruction
Number 33 18 17 62 9 2 6 6 1 4 1
7 1
3
throughout. This indicates a change in the mechanical nature of the orifice without hypertonicity of the bladder. In the case of a wide ureter knowledge of the absolute and relative pressures is decisive in determining whether the obstruction is at the ureterovesical junction or at the bladder neck, or at both sites; thus the correct operative decision can be made. It avoids the possibility of reimplantation of the ureter when what is really needed is an attack on the bladder neck or other aspects of the outflow tract. These studies have allowed a much more logical approach to the management of megaureters of all types and to the large ureters which present a problem in boys who have had resection of posterior urethral valves. I have considered a relative pressure of up to I2 cm. water as normal at the high flow rate of 10 ml. per minute. This is on the basis of many studies in seemingly unobstructed systems. It is difficult to interpret the significance of a pressure of, say, 15 to 18 cm. water at this flow rate and to determine at what level an operation is necessary. However, in my opinion it appears probable that pressures over 20 cm. water warrant relief of obstruction. It is significant that after a pyeloplasty the pressures are usually less than 12 cm. water.’ A high flow is necessary to stress the system maximally; 10 ml. per minute is well within the physiologic range, but 5 or 2 ml. per minute can be substituted and the pressures then observed at these rates.
150
To summarize the results of the studies performed is difficult since each study has been a complete investigation in reference to each individual patient. The conditions studied are shown in Table I. Many results have influenced our clinical decisions in a direction different from that which would have been taken had no study been available. Mostly this has meant that unnecessary operations have been avoided; however in a few younger patients higher pressures have been found and operations have been performed where we might otherwise have been tempted to procrastinate and do repeat radiographic or serial studies of renal function. We have seen patients with gross calyceal clubbing and no obstruction and others with minimal changes but with higher than normal pressures. Because of these findings we are now more wary in our interpretation of the radiographic findings and are resorting to dynamic studies more and more. These studies call for a degree of organization within the department and take up a little time, but we believe it is time well spent; and if they save an unnecessary operation or prevent the time and expense of repeated radiographic studies then surely they are worthwhile. Morbidity is low. We have frequently encountered minimal hematuria, but this never has been of serious consequence. A careless puncture once caused peritonism which quickly resolved, but this should easily be avoided. We have only recorded 1 case oi urinary infection attributable to this procedure. This dynamic approach can be recommended for the difficult diagnostic problem when other methods of assessment have failed. Cambridge,
1. \Vhitaker RH: Diagnosis of obstruction Ann. R. Coil. Surg. Engl. 53:153(1973). 2. IDEM: Thr ureter in posterior urethral
England
in dilated uwters.
valvrs, Br. J. LTrol. 45: 395 (1973). 3. Johnston JH: The pathogenesis of hvdroneplrrosi, in children, ibid. 41: 724 (1969). 4. Backlund L, and Reuterskiold AG: Thv abnormal ureter in children. 1. Perfusion studies on the wide non-wfluxing Imeter, Stand. J. Ural. Nephrol. 3: 219 (1969). 5. Schweitzer FAW: Intrapc~lvic pr~ssuw and rwral frmrtion studies in experimmtal chronic partial ut’rteric ot,atruction. Br. J. Crol. 45: 2 (1973). 6. Whit&r RH: Methods of sssesing obstruction in dilntryl uretrrs. ihid. 45: 15 (1973). 7. IDEM: Equivocal pelviureteric olxtruction, i/kc/. 47: 771 (1976).
UROLOGY
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AUGUST
1978
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XII. \JI-XIREH
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