Ultrasound estimated bladder weight in the detection and post-operative follow-up of bladder outflow obstruction

This study was performed to standardize the ultrasound estimated bladder weight as an additional non-invasive test for the measurement of the bladder outflow obstruction and to measure the therapeutic effects of bladder outflow obstruction in the follow-up after surgical correction of obstruction. This study was conducted from December 2012 to May 2014 where the sample size was 55 and sampling technique was purposive. In bladder outflow obstruction patient, transabdominal sonography was performed using a 7.5 MHz. probe. The anterior bladder wall thickness was measured in three points in the midline 1 cm apart and the average value was recorded. After that bladder volume was measured by ultrasonogram. In pre- and post-operative groups ultrasound estimated bladder weight was measured from bladder wall thickness and bladder volume. In this study, the mean ± SD of age was 48.8 ± 15.0 years. In bladder outflow obstruction patient, the pre-operative ultrasound estimated bladder weight was 117 ± 45.1 g which was reduced to 53.9 ± 10.8 g three months after surgical correction of obstruction. The ultrasound estimated bladder weight is a non-invasive, cheap and easily available additional diagnostic tool for detecting bladder outflow obstruction as well as it can measure the therapeutic effects in post-operative period.


Introduction
Compensatory hypertrophy following infravesical obstruction leads to increase in blood perfusion to the urinary bladder wall muscles.[4] The urinary bladder which is formed by three layers shows different echogenicity on the ultrasound imaging.The detrusor muscle layer shows by a hypoechogenic layer between two hyperechogenic layers the serosa and mucosa respectively. 5, 6The measurement of different layers of urinary bladder varies investigator to investigator.Some measured the whole thickness of three layers together but others use the measurement of middle detrusor muscle only. 7,8 The way of measurement of the wall also varies.Most of the investigator prefer to measure anterior bladder wall but the study by measurement of posterior bladder wall through either by transrectal or by transvaginal ultrasound also there. 9There are no significant difference in the thickness of the different parts of urinary bladder wall measurement shown by different studies. 10,11  present study was done with the aim to standardize ultrasound estimated bladder weight as an additional routine test to assess the bladder outflow obstruction and to observe the post-surgical effect.

Materials and Methods
This study done was done on 55 patients with bladder outflow obstruction from December 2012 to May 2014.Patients with benign enlargement of prostate, stricture urethra and bladder neck hypertrophy were included.But the pediatric patient, the patient with neurogenic bladder and cystitis were excluded.Uroflowmetry, anterior bladder wall thickness

Copyright:
The opy ight of this a ti le is etai ed y the autho s [At i utio CC-By .] A aila le at: .a glajol.Transabdominal sonography was performed with the patient in supine position.By ultrasonic image, a vertical section of the bladder was obtained in the midline of the lower abdomen above the pubic symphysis using a 7.5 MHz.probe.The anterior bladder wall thickness was measured in the midline at 3 points approximately 1 cm.apart and the average value was recorded.Following that, the intravesical volume was measured by ultrasound and the bladder weight was calculated from the bladder wall thickness and intravesical volume, assuming that the bladder is a sphere (Figure 1).

Ultrasound estimated bladder weight was calculated by formula mentioned below
The urinary bladder resembles a sphere, and the internal diameter of the bladder was calculated from the volume of saline in the bladder (intravesical volume) from an outer diameter.The total bladder volume was calculated by subtracting the intravesical volume from the total vesical volume.Then, the spheric ultrasound estimated bladder weight was calculated by multiplying the volume of the bladder wall by the specific gravity. 9
The mean maximum urinary flow rate (Qmax) in pre-operative patients was 8.7 ± 3.6 mL/sec which was increased to 23.5 ± 6.5 mL/sec post-operatively.The lowest flow rate of urine was observed in case of stricture urethra pre-operatively which was increased after operation (Table I).Qmax was increased in all the cases after the operation.
The mean post-void residue in overall, benign enlargement of prostate and stricture urethra was ranged from 104-122 mL.Bladder neck hypertrophy showed higher amount post-void  residue 151 mL.Post-operative findings show a significant reduction in all the cases (Table I).
There was no change in the urinary bladder anterior wall thickness in all the cases.However, there was a significant decrease in the size after the operation.
The mean overall ultrasound estimated bladder weight in pre-and post-operative groups were 117.8 ± 45.1 and 53.9 ± 10.8 g respectively.The mean ultrasound estimated bladder weight of benign enlargement of the prostate for pre-and post-operative groups were 120.8 ± 46.8 and 54 ± 11 g respectively.In case of urethral stricture, it was 113 ± 43 and 58 ± 9 g for pre-and postoperative groups respectively (Table I).

Discussion
The present study shows that bladder outlet obstruction due to benign enlargement of prostate, stricture urethra, bladder neck hypertrophy or any other cause that decrease Qmax but increase the post-void residue.But after the relief of obstruction, this scenario reverses.The changes in Qmax and post-void residue that occur after intervention are statistically significant in the present study and the studies done by others.Ultrasound estimated bladder weight increases in bladder outlet obstruction due to compensatory hypertrophy, increase in blood perfusion and fibrosis. 1When outflow resistance decreases by treatment bladder wall thickness decreases with time.[12][13] Parameters such as Qmax and post-void residue were used for the detection and follow-up of this group of patients.But for the Qmax study, a machine is required.The result depends on the patients' level of understanding and the amount of pre-void volume of urine.So, the result does not represent the real scenario.The post-void residue varies if a slight delay occurs in the examination or the patient forces the intake of a lot of water within a short period of time to see the maximum bladder capacity which is significant for interpreting the post-void residue.
The Ultrasound estimated bladder weight does not depend on the patient factor.It is also non-invasive, and easily available.So, this can be taken as a good parameter for detection and follow-up of patients with bladder outlet obstruction.

Conclusion
Ultrasound i fo Ultrasound estimated bladder weight in the detection and post-operative follow-up of bladder outflow obstruction Mohammad Shafiqur Rahman, Mohammad Khairuzzaman, Md.Saiful Islam, Muhammad Humayun Kabir and Faika Farah Ahmed physical examination and relevant investigations were done.Urinalysis and culture were done to exclude urinary tract infection; ultrasonography was done to see the maximum bladder capacity, post-void residual urine and bladder wall thickness and intravesical volume.Uroflowmetry was done to see the flow rate curve that gives differentiation between the static or dynamic obstruction.

Figure 1 :Figure 2 :
Figure 1: Ultrasonogram of the anterior wall of urinary bladder.Hyperechogenic adventitia, hypoechogenic detrusor and hyperechogenic mucosa with submucosa comprise bladder wall and it was measured as 0.31 cm in the photograph

Cite this arti le: Rah
a MS, Khai uzza a M, Isla MS, Ka i MH, Ah ed FF.Ult asou d esti ated ladde eight i the detetio a d post-ope ati e follo -up of ladde outflo o st u tio .Ba gaa dhu Sheikh Muji Med U i J.; :

1, 3, 4
estimated bladder weight is promising as an auxiliary technique for the diagnosis, prediction, monitoring and follow-up in therapeutic effects of bladder outflow obstruction.Watanabe H. Ultrasonic estimation of bladder weight as a measure of bladder hypertrophy in men with infravesical obstruction: A preliminary report.Urology 1996; 47: 942-47.13.Kuzmic AC, Brkljacic B, Ivankovic D. Sonographic measurement of detrusor muscle thickness in healthy children.Pediatr Nephrol.2001; 16: 1122-25.