Applications of Bladder Ultrasonography. I. Bladder Content and Residue

0022-5347 /81/1252-0174$02.00/0 Vol. 125, February Printed in U.S.A.

THE JOURNAL OF UROLOGY

Copyright© 1981 by The Williams & Wilkins Co.

APPLICATIONS OF BLADDER ULTRASONOGRAPHY. I. BLADDER CONTENT AND RESIDUE RICARDO ESPUELA ORGAZ, * ARMANDO ZULUAGA GOMEZ, CARLOS TORRES RAMIREZ JOSE LUIS MARTINEZ TORRES

AND

From the Hospital Clinico "San Cecilio," Universidad de Granada, Granada, Spain

ABSTRACT

In reviewing our experience in the field of bladder ultrasonography, we conclude that this method is seldom used because its value has not been disseminated widely. Such a method is especially valuable in the investigation of infiltrative bladder tumors and the calculation of bladder volume. We herein report the results obtained in 100 patients whose bladder content has been calculated with the formula 12.56 times radius times height. We also outline the advantages of ultrasound over catheterization. Although ultrasound techniques were used earlier in urology than in other branches of medicine, 1• 2 its subsequent rate of development decreased until the 1960s when countless articles on renal ultrasonography appeared describing the ultrasonic features of practically all diseases of the kidney. Given that the bladder is an organ ideally suited for ultrasonic exploration it seems paradoxical that this method was not used until 1960, 3

and that, consequently, little is known of the uses and the value of bladder ultrasonography. Our experience in this field has enabled us to define clearly the precise uses of ultrasound in bladder diseases. We believe that it is most suited to the investigation of infiltrative bladder tumors, and the calculation or diagnosis of bladder content and/ or residue. Prostatic ultrasonography through the bladder

Fm. 1. A, longitudinal scan. Diameter of bladder length between 2 farthest points is measured. B, transverse scan. Anteroposterior diameter is used for measurement. When difference between anteroposterior and transverse diameters is great we used average between them but results were worse.

especially when one considers that by this date several articles had been published on prostatic ultrasonography. Because of its location the prostate is a difficult organ to explore via ultrasound. It is even more surprising that the bladder still is one of the least known areas from an ultrasonic point of view4

deserves to be considered separately, and we limit ourselves to commenting that ultrasound studies of the prostate should be transrectal, 5• 6 since studies effected through the abdomen yielded only 25 per cent positive results in 100 patients. MATERIALS AND METHODS

Accepted for publication May 2, 1980. * Current address: Servicio de Urologia, Residencia Sanitaria de la Seg. Social, Paseo de Sta. Barbara s/n, Soria, Spain.

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We used a cross-sectional image apparatus (Kretzh Technik Gesellschaft, model 4100 MB), a real-time ultrasound scanner (Searle, model Pho/sonic 2000) and a Vidoson (Siemens).

APPLICATIONS OF BLADDER ULTRASONOGRAPHY

In the investigation of bladder content the patient presents with a reasonable desire to urinate and is placed in the supine position. A primary midline longitudinal scan is done to assess the fullness of the bladder so that the required technical adjustments can be made. The patient is asked to urinate normally and, immediately afterwards, a midline longitudinal scan and a transverse scan are done, the latter 2 or 3 cm. from the pubis or at the point of greatest distance between the bladder walls. We generally use a probe of 2 mHz. frequency. These 2 scans provide us with sufficient data to measure the diameters required to make a sufficiently reliable calculation of bladder volume. For the longitudinal scan we measure the maximum distance between the lower edge and the bladder neck, and for the transverse section we usually measure the anteroposterior diameter (fig. 1). We sought a formula that would provide us with a rapid and efficient method of calculating bladder volume. We considered all existing geometrical formulas but obtained poor results with them. This was expected, since the shape of the bladder is variable and, naturally, cannot be expressed by any geometric figure. "Yve selected 100 patients who had been scanned by the method outlined previously and on whom we had performed catheterization or suprapubic puncture immediately after exploration for therapeutic reasons. Thus, we had ultrasonographic evidence of the exact volume of the bladder. A totally empirical selection was made of variants from those geometrical formulas that had yielded the least error. The best results were TABLE

I. Percentage error in the estimated volume

Real Volume (cc)

No. Cases

0-199 200-399 400-599 600-799 800-999 1,000-1,199 1,200-1,399 1,400-1,599 1,600-1,799 Totals

5 23 31 18 5 6

8 1 3 100

Max. Error

Min. Error

Mean Error

(%)

(%)

(%)

12 34 34 31.8 18.6 9 34

5 0 1 3.7 1.12 0.5 7.3

6.04 12.12 13.40 15.21 7.97 5.52 21.03

18.36 34

11.34 0

14.06 12.9

10

TABLE

2. Representation of the estimated mean volume ± standard

deviation in each group Real Volume (cc) 0-199 200-399 400-599 600-799 800-999 1,000-1,199 1,200-1,399 1,400-1,599 1,600-1, 799

No. Cases 5

23 31 18 5

6 8

1 3

Estimated Mean Volume (cc ± standard deviation) 156.1 ± 298.1 ± 501.0 ± 725.2 ± 908.5 ± 1,013.6 ± 1,004.75 ± 1,350 1,537 ±

32.8 61.9 56 58.9 44.2 50.83 640.32 207 .82

obtained with the formula 12.56 x r x h, where r is the radius of the bladder in the transverse scan and h is the maximum height of the bladder in a vertical cross section. The formula does not describe any known measurement or geometrical figure but appears highly suitable in the calculation of bladder volume. RESULTS

The percentage error in the estimated volume is shown in table 1. Although there are isolated cases of considerable error (34 per cent) the calculations generally follow a line slightly higher than that of the real measurements and the majority of cases show a percentage of error lower than or similar to the over-all average error of 12.9 per cent (fig. 2). A study of standard average and standard deviation in the 100 cases reveals a greater deviation in the cases included in the 1,200 to 1,399 real volume group (table 2). The greatest difficulty in making the calculations was in the decision as to which diameter should be measured in the longitudinal scan. The interference of the pubis sometimes prevented us from seeing the lower edge of the bladder and, at other times, bladder expansion affected the anteroposterior diameter. Occasionally, it was uncertain which of the possible diameters should be chosen (fig. 3). The transverse diameters presented fewer problems, almost always being limited to the existence of a considerable disparity between the horizontal and vertical diameters. In such cases the maximum percentage of error had been assured. DISCUSSION

CASES /

ERROR

29

10

15

20

Fm. 2. Percentage error

25

30

35

The first application of ultrasound in the evaluation of bladder diseases was to determine the volume of residual urine. However, the method did not become popular, undoubtedly because of the precision and widespread use of post-micturitional catheterization. Although bladder residual volumes have always been measured by catheterization or suprapubic aspiration these methods cause difficulties and create considerable risks. For this reason these procedures should be used only when strictly necessary, so that even large amounts of residual urine remain unexamined to avoid the risks and discomforts that catheterization can entail. Therefore, different methods have been sought to replace catheterization, for example bacteriological methods, 7 isotopic methods, radiological methods and so forth. Of these methods radiological procedures are used most often but there are disadvantages (the nature of x-ray photographs prevents their repeated use, the inaccuracy of results, contrast allergies and so forth). We do not believe that any existing method fulfills those requirements that make ultrasound the ideal method for the investigation of bladder residual urine. 8 It has no contraindications, it is free of risk for the patient, it is an almost comfortable exploration that can be repeated as often as required and it is not feared by children. When all of these features are considered in relation to bladder catheterization the advantages of ultrasound are evident. However, the method has the disadvantage of inaccuracy of calculation. Undoubtedly, catheterization is the most accurate method but routine practice rarely demands absolute accuracy. We are convinced that an

176

ESPUELA ORGAZ AND ASSOCIATES

. Fm. 3. A, in some cases lower limit of bladder is impossible to be determined, which was source of error in our calculations. In this patient catheter is reference point and shows interference of pubis. B, in some longitudinal scans there are various possible diameters. Although difference between them is small uncertainty as to which diameter to choose was another cause of error in our calculations.

error such as we have obtained is perfectly tolerable in any clinical situation and the consequences of a slightly imperfect calculation are to be preferred to the discomfort, the risk of infection and so forth inherent in catheterization.

volume of the enlarged prostate. Brit. J. Rad., 46: 68, 1973. 7. Hinman, F., Jr. and Cox, C.: Residual urine volume in normal male subjects. J. Urol., 97: 641, 1967. 8. Harrison, N. W., Parks, C. and Sherwood, T.: Ultrasound assessment of residual urine in children. Brit. J. Urol., 47: 805, 1976.

REFERENCES 1. Wild, J. J. and Reid, J.M.: Diagnostic use of ultrasound. Brit. J.

2. 3. 4. 5. 6.

Phys. Med., 19: 248, 1956. ' Holmes, J. H., Howry, D. H., Posakony, G. J. and Cushman, C.R.: The ultrasonic visualization of soft tissue structures in the human body. Trans. Amer. Clin. Climat. Ass., 66: 208, 1954. West, K. A.: Sonocystography. A method for measuring residual urine. Scand. J. Urol. Nephrol., 1: 68, 1967. Kristensen, J., Holm, H. H., Rasmussen, S. N. and Smith, E. D.: Ultrasonically guided percutaneous puncture of renal masses. Scand. J. Urol. Nephrol., suppl. 15, 6: 49, 1972. Watanabe, H., lgari, D., Tanahashi, Y., Harada, K. and Saitoh, M.: Transrectal ultrasonotomog-;aphy of the prostate. J. Urol., 114: 734, 1975. Whittingham, T. A. and Bishop, R.: Ultrasonic estimation of the

EDITORIAL COMMENT For the routine assessment of residual urine volumes in patients with symptoms of bladder outlet obstruction or neurogenic disorders, I prefer a post-voiding film in association with excretory urography. Although inaccuracies do exist complete emptying is evident. The pros and cons of catheterization are topics unto themself. Ultrasonography as described in this paper certainly would have application when catheterization is not desirable, such as in children or in patients undergoing 24-hour urine collections for measurement of renal function. Martin I. Resnick Department of Urology Bowman Gray School of Medicine Winston-Salem, North Carolina