Is a Full Bladder Still Necessary for Pelvic Sonography?

Abstract & Commentary

Synopsis: This study confirms that transvaginal sonography, with an empty bladder, is all that is required for most pelvic ultrasound examinations. Adjunctive transabdominal scans will occasionally be required when there is a pelvic mass, but even in these cases bladder distention should be avoided.

Source: Benacerraf BR, et al. Is a full bladder still necessary for pelvic sonography? J Ultrasound Med 2000;19:237-241.

During the past decade, transvaginal ultrasound has gradually become the preferred method for imaging female pelvic organs. To optimize this approach, the patient’s urinary bladder should be empty. If the study is technically unsatisfactory or incomplete, the patient is usually instructed to drink approximately one liter of fluid, wait until her bladder is distended, and undergo a repeat ultrasound examination using a transabdominal (transvesical) approach. To determine whether a distended bladder is an absolute necessity for the transabdominal portion of the examination, Benacerraf and associates did a one-month prospective study of 206 consecutive patients referred for a pelvic ultrasound examination.

The initial part of the study consisted of an experienced sonographer performing a transabdominal scan through a distended bladder. Immediately thereafter, the patient voided, and an experienced sonologist (who was blinded to the transabdominal findings) did a transvaginal pelvic ultrasound examination. Subsequently, the sonologist repeated the transabdominal scan, but the bladder remained empty. At the completion of these three examinations, the sonographer and sonologist conferred, and decided if all pertinent pelvic anatomy was visible: 1) by transvaginal imaging alone; 2) by transvaginal plus transabdominal scans (the latter done through an empty bladder); or 3) by transabdominal scans (through a full bladder).

The results of this study showed that transvaginal scans alone were satisfactory to image the uterus and both ovaries in 172 patients (83.5%), and that transabdominal scans were necessary for the remaining 34 patients (16.5%). Noteworthy, however, was that of the 34 patients who required additional transabdominal scans, satisfactory images were obtained with an empty urinary bladder in 31 of these cases, and that only three cases required a distended bladder. Further analysis revealed that 25% of women with an enlarged uterus (primarily due to fibroids) required transabdominal scans (with an empty bladder), while more than 95% of patients with a normal size uterus were satisfactorily studied using only the transvaginal route.

Comment by Faye C. Laing, MD

Because transvaginal scans are usually done with a 5-MHz transducer while transabdominal scans often require a 3.5-MHz transducer, it should not surprise us that several comparative ultrasound studies agree uniformly that transvaginal scans yield more diagnostic information than transabdominal scans.1-3 Consequently, many sonologists now routinely begin pelvic ultrasound examinations using a transvaginal approach and an empty urinary bladder. Subsequent transabdominal scans are reserved for a subset of women in whom transvaginal imaging either incompletely or inadequately visualized the pelvic organs. Not only does this approach save time, but it also minimizes patient discomfort, since most women will not be required to fill their bladder in preparation for the transabdominal examination.

The results of this study show convincingly that even in those women required to undergo a transabdominal study, more urine in the bladder does not equate with a better quality study. Indeed, of the 206 patients in this study, only three (1.5%) required a distended bladder for a complete examination. Furthermore, Benacerraf et al have shown that women who require transabdominal imaging will almost always have a large uterine or adnexal mass.

In my opinion, the most practical approach for gynecologic imaging is as follows. If a women has a known or suspected pelvic mass, an initial transabdominal scan should be done without bladder filling. For complete visualization of the pelvic organs, many, but certainly not all, of these women will require a subsequent transvaginal exam (with an empty bladder). Since most women do not have a large pelvic mass, and since their organs will be better visualized transvaginally, this approach alone will suffice for the great majority of women.

References

1. Leibman AJ, et al. Transvaginal sonography: Comparison with transabdominal sonography in the diagnosis of pelvic masses. AJR Am J Roentgenol 1988;151:89-92.

2. Mendelson EB, et al. Gynecologic imaging: Comparison of transabdominal and transvaginal sonography. Radiology 1988;166:321-324.

3. Tessler FN, et al. Transabdominal versus endovaginal pelvic sonography: Prospective study. Radiology 1989;170:553-556.