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Estimation of Prostatic Size by Suprapubic Ultrasonography
0022-534 7/79/1215-0615$02.00/0 Vol. 121, May
THE JOURNAL OF UROLOGY
Printed in U.S.A.
Copyright © 1979 by The Williams & Wilkins Co.
ESTIMATION OF PROSTATIC SIZE BY SUPRAPUBIC ULTRASONOGRAPHY MICHAEL HENNEBERRY, MICHAEL F. CARTER
AND
HARVEY L. NEIMAN
From the Departments of Urology and Radiology, Northwestern University Medical School, Chicago, Illinois
ABSTRACT
Previous ultrasonic scanning of the prostate primarily has involved the transrectal approach. In this study the suprapubic approach was chosen because it uses basic ultrasound equipment and is atraumatic. In 29 patients undergoing prostatectomy there was a highly significant correlation (r equals 0.95) between the prostatic weight determined by this method and the postoperative weight of the adenoma. Determination of prostatic size has long been important to urologic surgeons because it influences the operative approach for prostatectomy. Serial measurements of prostatic size also are important in following the response to non-operative therapy ofprostatic disease. In certain patients, such as those who have undergone abdominal-perineal resections, determination of prostatic size by manual palpation is impossible. These considerations have prompted us to investigate the use oftransabdominal ultrasound as a means to estimate prostatic volume.
45 to 65 gm. range the post-transurethral resection weight was usually <45 gm. There were 4 such patients in this category. However, this difference in weights was not so great that one would have expected an open prostatectomy to have been significantly more difficult had that approach been chosen. Of all the patients who underwent transurethral resections of the prostate only 1 had a postoperative weight (78 gm.) that was greater than the estimated weight (65 gm.). DISCUSSION
MATERIALS AND METHODS
A prospective study was conducted at our hospital from March to October 1977. As part of the pre-prostatectomy diagnostic study 29 patients were evaluated with the use of ultrasound during this period. Eleven patients subsequently underwent open prostatectomy and 18 had transurethral resections. The operative specimen was weighed postoperatively and this weight was presumed to equal the true weight of the adenoma. The technique of the examination itself is straightforward. Commercially available gray scale B-mode ultrasound equipment with a 2.25 or 3.5 MHz internally focused transducer was used in all cases. The patient was asked to arrive in the ultrasound laboratory with a full bladder. The transducer was placed on the abdomen in the suprapubic position and angled in a caudal direction into the pelvis. With the full bladder as a window the technician obtained an image of the prostate from single pass sector scans. Transverse and longitudinal sections were obtained. The cross-sectional image approximated a circle and the diameter of the prostate was measured easily. If the anteroposterior and transverse diameters differed the average of the 2 was computed. In most instances, the surgical capsule was identified and served as the limit of the measurement (fig. 1). The volume of the gland (computed from the formula for the volume of a sphere, 4/31rr3 ) was equivalent to the estimated weight, since the specific gravity of the prostate was 1.05 gm./cc. 1
Prostatic ultrasound studies have lagged behind ultrasonic investigation of other organs, primarily because of the gland's well concealed anatomic position within the bony pelvis. Previous investigators have obtained ultrasonic images of the prostate via the transrectaP-3 and transurethral 4 avenues. Both of these approaches are cumbersome and require expensive additions to basic ultrasound equipment. A newer diag-
•
'
RESULTS
The estimated weight was plotted against the postoperative weight (fig. 2). The correlation coefficient (r) was 0.95, which proved significant at the 0.0005 level. The most accurate estimations were seen at the upper end of the scale in patients who had undergone open prostatectomies, presumably because a more complete removal of the hyperplastic tissue resulted in a postoperative weight that truly represented the weight of the adenoma. This was further substantiated by the fact that_when the estimated weight by ultrasound was in the Accepted for publication July 14, 1978.
FIG. 1. Transverse scan of patient with benign prostatic hyperplasia. B, bladder. A, adenoma. SC, surgical capsule.
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POST-OP WEIGHT (GMS l
Fm. 2. Comparison of estimated and postoperative weights in 29 patients who underwent prostatectomy. X, open prostatectomy. e, transurethral resection.
nostic tool, computed body tomography, also is able to image the prostate gland but has shown no advantage over ultrasound in evaluating this gland. 5 Attempts to develop a radioisotope scan of the prostate have been unsuccessful thus far. There have been only 2 previous reports of ultrasonic estimation of prostatic volume by the suprapubic approach. 5' 6 It is our opinion that this technique should receive more attention because it offers several advantages over existing modes to study the prostate: 1) it is an accurate predictor of prostatic volume, 2) it requires no adjustments or additions to basic ultrasound equipment, 3) it requires no orifice (a definite advantage when first evaluating the post-abdominal-perinea} resection patient with voiding difficulties), 4) it is atraumatic and uniformly well tolerated by patients and 5) there is no radiation exposure as with computed body tomography. It should be emphasized that excellent imaging of the prostate by this approach is possible only when the bladder is distended adequately. The main disadvantage of this technique has been our inability to predict the presence of carcinoma in a gland, as others have done with the transrectal approach. 3 In a retrospective analysis of our patients with carcinoma and prostatitis we have been able to detect subtle changes in echogenicity when compared to patients with benign prostatic hypertrophy (fig. 3). Therefore, we are optimistic that with experience and the improved resolution obtained with newer equipment detection of prostatic carcinoma will be possible by this technique. At present, our level of confidence in this technique is such that a decision aS-to which approach to use for prostatectomy usually includes the results of the suprapubic ultrasound. As mentioned previously, the advantage of this approach in evaluating patients who have undergone abdominal-perinea} resection is readily apparent. Suprapubic ultrasound should prove valuable also in monitoring the response of patients with prostatic carcinoma who are undergoing non-operative
Fm. 3. Transverse scan of patient with bladder neck obstruction and diffuse adenocarcinoma of prostate. Arrow demonstrates increased echo pattern in periurethral prostatic tissue, consistent with pathological diagnosis of carcinoma. B, bladder.
therapy. Future applications include serial measurements of prostatic volume in patients receiving hormonal therapy for benign prostatic hyperplasia. Thus, it would seem that suprapubic ultrasonography is a diagnostic tool with which all urologists and ultrasonographers should become familiar. REFERENCES
1. Watanabe, H., Igari, D., Tanahashi, Y., Harada, K. and Saitoh,
M.: Transrectal ultrasonotomography of the prostate. J. Urol., 114: 734, 1975. 2. King, W.W., Wilkiemeyer, R. M., Boyce, W. H. and McKinney, W. M.: Current status ofprostatic echography. J.A.M.A., 226: 444, 1973.
3. Resnick, M. I., Willard, J. W. and Boyce, W. H.: Recent progress in ultrasonography of the bladder and prostate. J. Urol., 117: 444, 1977.
4. Hohn, H. H. and Northeved, A.: A transurethral ultrasonic scanner. J. Urol., 111: 238, 1974. 5. Sukov, R. J., Scardino, P. T., Sample, W. F., Winter, J. and Confer, D. J.: Computed tomography and transabdominal ultrasound in the evaluation of the prostate. J. Comp. Assist. Tomography, 1: 281, 1977. 6. Whittingham, T. A.: Ultrasonic estimation of the volume of the enlarged prostate. Brit. J. Rad., 46: 68, 1973. EDITORIAL COMMENT Most authors discussing the examination of the prostate by ultrasound have described the technique popularized in Japan using a rectal transducer (reference 5 in article). This approach is somewhat time-consuming, requires a specific expensive instrument and is uncomfortable. B-scan ultrasound using an abdominal approach can visualize most of the prostate and, as these investigators show, is fairly accurate for volume estimation. Prostatic neoplasms have been identified by the same approach with fair accuracy. R .C .S.
THE JOURNAL OF UROLOGY
Printed in U.S.A.
Copyright © 1979 by The Williams & Wilkins Co.
ESTIMATION OF PROSTATIC SIZE BY SUPRAPUBIC ULTRASONOGRAPHY MICHAEL HENNEBERRY, MICHAEL F. CARTER
AND
HARVEY L. NEIMAN
From the Departments of Urology and Radiology, Northwestern University Medical School, Chicago, Illinois
ABSTRACT
Previous ultrasonic scanning of the prostate primarily has involved the transrectal approach. In this study the suprapubic approach was chosen because it uses basic ultrasound equipment and is atraumatic. In 29 patients undergoing prostatectomy there was a highly significant correlation (r equals 0.95) between the prostatic weight determined by this method and the postoperative weight of the adenoma. Determination of prostatic size has long been important to urologic surgeons because it influences the operative approach for prostatectomy. Serial measurements of prostatic size also are important in following the response to non-operative therapy ofprostatic disease. In certain patients, such as those who have undergone abdominal-perineal resections, determination of prostatic size by manual palpation is impossible. These considerations have prompted us to investigate the use oftransabdominal ultrasound as a means to estimate prostatic volume.
45 to 65 gm. range the post-transurethral resection weight was usually <45 gm. There were 4 such patients in this category. However, this difference in weights was not so great that one would have expected an open prostatectomy to have been significantly more difficult had that approach been chosen. Of all the patients who underwent transurethral resections of the prostate only 1 had a postoperative weight (78 gm.) that was greater than the estimated weight (65 gm.). DISCUSSION
MATERIALS AND METHODS
A prospective study was conducted at our hospital from March to October 1977. As part of the pre-prostatectomy diagnostic study 29 patients were evaluated with the use of ultrasound during this period. Eleven patients subsequently underwent open prostatectomy and 18 had transurethral resections. The operative specimen was weighed postoperatively and this weight was presumed to equal the true weight of the adenoma. The technique of the examination itself is straightforward. Commercially available gray scale B-mode ultrasound equipment with a 2.25 or 3.5 MHz internally focused transducer was used in all cases. The patient was asked to arrive in the ultrasound laboratory with a full bladder. The transducer was placed on the abdomen in the suprapubic position and angled in a caudal direction into the pelvis. With the full bladder as a window the technician obtained an image of the prostate from single pass sector scans. Transverse and longitudinal sections were obtained. The cross-sectional image approximated a circle and the diameter of the prostate was measured easily. If the anteroposterior and transverse diameters differed the average of the 2 was computed. In most instances, the surgical capsule was identified and served as the limit of the measurement (fig. 1). The volume of the gland (computed from the formula for the volume of a sphere, 4/31rr3 ) was equivalent to the estimated weight, since the specific gravity of the prostate was 1.05 gm./cc. 1
Prostatic ultrasound studies have lagged behind ultrasonic investigation of other organs, primarily because of the gland's well concealed anatomic position within the bony pelvis. Previous investigators have obtained ultrasonic images of the prostate via the transrectaP-3 and transurethral 4 avenues. Both of these approaches are cumbersome and require expensive additions to basic ultrasound equipment. A newer diag-
•
'
RESULTS
The estimated weight was plotted against the postoperative weight (fig. 2). The correlation coefficient (r) was 0.95, which proved significant at the 0.0005 level. The most accurate estimations were seen at the upper end of the scale in patients who had undergone open prostatectomies, presumably because a more complete removal of the hyperplastic tissue resulted in a postoperative weight that truly represented the weight of the adenoma. This was further substantiated by the fact that_when the estimated weight by ultrasound was in the Accepted for publication July 14, 1978.
FIG. 1. Transverse scan of patient with benign prostatic hyperplasia. B, bladder. A, adenoma. SC, surgical capsule.
615
616
HENNEBERRY, CARTER AND NEIMAN
210
180
I
~
150
!c
!2
w
~
C 120
w
•
XXX
!;. :Ii
i;;
w 90
60
30
... 30
60
90
120
150
180
210
POST-OP WEIGHT (GMS l
Fm. 2. Comparison of estimated and postoperative weights in 29 patients who underwent prostatectomy. X, open prostatectomy. e, transurethral resection.
nostic tool, computed body tomography, also is able to image the prostate gland but has shown no advantage over ultrasound in evaluating this gland. 5 Attempts to develop a radioisotope scan of the prostate have been unsuccessful thus far. There have been only 2 previous reports of ultrasonic estimation of prostatic volume by the suprapubic approach. 5' 6 It is our opinion that this technique should receive more attention because it offers several advantages over existing modes to study the prostate: 1) it is an accurate predictor of prostatic volume, 2) it requires no adjustments or additions to basic ultrasound equipment, 3) it requires no orifice (a definite advantage when first evaluating the post-abdominal-perinea} resection patient with voiding difficulties), 4) it is atraumatic and uniformly well tolerated by patients and 5) there is no radiation exposure as with computed body tomography. It should be emphasized that excellent imaging of the prostate by this approach is possible only when the bladder is distended adequately. The main disadvantage of this technique has been our inability to predict the presence of carcinoma in a gland, as others have done with the transrectal approach. 3 In a retrospective analysis of our patients with carcinoma and prostatitis we have been able to detect subtle changes in echogenicity when compared to patients with benign prostatic hypertrophy (fig. 3). Therefore, we are optimistic that with experience and the improved resolution obtained with newer equipment detection of prostatic carcinoma will be possible by this technique. At present, our level of confidence in this technique is such that a decision aS-to which approach to use for prostatectomy usually includes the results of the suprapubic ultrasound. As mentioned previously, the advantage of this approach in evaluating patients who have undergone abdominal-perinea} resection is readily apparent. Suprapubic ultrasound should prove valuable also in monitoring the response of patients with prostatic carcinoma who are undergoing non-operative
Fm. 3. Transverse scan of patient with bladder neck obstruction and diffuse adenocarcinoma of prostate. Arrow demonstrates increased echo pattern in periurethral prostatic tissue, consistent with pathological diagnosis of carcinoma. B, bladder.
therapy. Future applications include serial measurements of prostatic volume in patients receiving hormonal therapy for benign prostatic hyperplasia. Thus, it would seem that suprapubic ultrasonography is a diagnostic tool with which all urologists and ultrasonographers should become familiar. REFERENCES
1. Watanabe, H., Igari, D., Tanahashi, Y., Harada, K. and Saitoh,
M.: Transrectal ultrasonotomography of the prostate. J. Urol., 114: 734, 1975. 2. King, W.W., Wilkiemeyer, R. M., Boyce, W. H. and McKinney, W. M.: Current status ofprostatic echography. J.A.M.A., 226: 444, 1973.
3. Resnick, M. I., Willard, J. W. and Boyce, W. H.: Recent progress in ultrasonography of the bladder and prostate. J. Urol., 117: 444, 1977.
4. Hohn, H. H. and Northeved, A.: A transurethral ultrasonic scanner. J. Urol., 111: 238, 1974. 5. Sukov, R. J., Scardino, P. T., Sample, W. F., Winter, J. and Confer, D. J.: Computed tomography and transabdominal ultrasound in the evaluation of the prostate. J. Comp. Assist. Tomography, 1: 281, 1977. 6. Whittingham, T. A.: Ultrasonic estimation of the volume of the enlarged prostate. Brit. J. Rad., 46: 68, 1973. EDITORIAL COMMENT Most authors discussing the examination of the prostate by ultrasound have described the technique popularized in Japan using a rectal transducer (reference 5 in article). This approach is somewhat time-consuming, requires a specific expensive instrument and is uncomfortable. B-scan ultrasound using an abdominal approach can visualize most of the prostate and, as these investigators show, is fairly accurate for volume estimation. Prostatic neoplasms have been identified by the same approach with fair accuracy. R .C .S.