Abstract: Ultrasonic Validation of Residual Bladder Volume in Postvaginal Hysterectomy Patients

Ron Maymon, Shlomo Bilboa, Jacques S. Abramowicz, Adrian Shulman, Michael Toar, and Charles Bahary. "Ultrasonic Validation of Residual Bladder Volume in Postvaginal Hysterectomy Patients." Gynecologic and Obstetric Investigation 31 (1991): 226-30.

Objectives:
* To assess the sensitivity, specificity, and positive and negative predictive values of traditional, non-portable ultrasonography as a screening procedure to determine post-void residual bladder volume in women recovering from hysterectomy, and compare it with catheterization.

Methods:
* Eighty postvaginal hysterectomy patients were examined by ultrasound after voiding on the first or second day following their operation. A total of 100 examinations were performed, as some patients were examined more than once.
* Patients were scanned using a real-time sector scan Dynex (made in Elscint, Israel) with a built-in program for measuring the cross-sectional area. The transducer worked at a frequency of 3.5 mHz. Bladder volume was determined by finding the largest cross-sectional image of the bladder, and measuring its height and depth axes.
* Immediately after each ultrasound examination, the true volume of the bladder was measured by catheterization.

Results:
* The sensitivity was 23%, meaning that the Dynex ultrasound machine detected only 3 out of 13 patients who required catheterization.
* The specificity was 97.7%, which means that the ultrasound eliminated 85 out of 87 patients, who had less than 150 cm3 of residual urine and were thus not appropriate cases for catheterization.
* The negative predictive value is 89.5%, meaning that of the 95 patients diagnosed by ultrasound as having less than 150 cm3 of residual urine, 85 could be considered as inappropriate candidates for catheterization.

Conclusions:
* "The ultrasonographic screening method is a simple, noninvasive test which appears to be ideal for the bedside assessment of residual urine volume in postvaginal hysterectomy patients." Despite its lack of sensitivity, its negative predictive value makes non-portable ultrasound an effective means of determining which patients do not need catheterization.
* The lack of sensitivity is related to the fact that there is inconsistency in the application of various formulas among different ultrasound centers and studies who use traditional, non-portable ultrasound equipment, and the quality of the image produced by ultrasound varies among the companies who produce such equipment.
* "Based on our data, we would suggest that instead of routine catheterization for residual urine volume assessment, ultrasonographic measurements may safely be performed in postvaginal hysterectomy patients. It will avoid unnecessary catheterization in many patients, as well as the side effects normally associated [with catheterization]."

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