Fluid in the Pouch of Douglas During Hysteroscopy and Tubal Patency
The appearance of fluid in the pouch of Douglas (POD) during or after hysteroscopy suggests, but does not definitively confirm, bilateral tubal patency. This finding has moderate diagnostic value but should not be relied upon as the sole method for confirming tubal patency in clinical practice.
Diagnostic Performance
The presence of fluid in the POD after hysteroscopy has the following characteristics:
Sensitivity and specificity are moderate: When transvaginal ultrasound is performed immediately after diagnostic hysteroscopy to detect fluid in the POD, the method demonstrates 73% sensitivity and 70% specificity for tubal patency, with a positive predictive value of 83% and negative predictive value of only 56% 1.
The ACR acknowledges this finding: The American College of Radiology states that "the presence of increased fluid in the posterior cul-de-sac following sonohysterography may indicate tubal patency," but notably does not recommend isolated sonohysterography for assessing tubal occlusion 2.
High accuracy when fluid is present: In one study of 56 infertile patients, when fluid was observed in the POD after hysteroscopy, 36 of 37 cases (97%) had confirmed unilateral or bilateral tubal patency by laparoscopic chromopertubation 1.
Critical Limitations
The absence of fluid does NOT confirm bilateral tubal occlusion, which is a crucial clinical pitfall:
When no fluid was seen in the POD, only 17 of 19 cases (89%) actually had bilateral tubal occlusion confirmed by laparoscopy, meaning 2 cases had patent tubes despite no visible fluid 1.
The "bubble sign" (visible air bubbles at the tubal ostia during hysteroscopy) is even less reliable, with only 73% sensitivity and 70% specificity for predicting actual tubal patency 3.
Recommended Approach for Confirming Tubal Patency
For definitive assessment of tubal patency, the following methods should be used instead:
First-Line Testing
Hysterosalpingography (HSG) remains the standard first-line test with 65% sensitivity and 85% specificity compared to laparoscopy, and has the added benefit of potentially improving pregnancy rates (up to 38% vs 21% without HSG) 2, 4.
Hysterosalpingo-contrast sonography (HyCoSy) with echogenic contrast has similar accuracy to HSG and demonstrates 91% accuracy in diagnosing tubal patency in women with endometriosis 2, 4.
Gold Standard
- Laparoscopy with chromopertubation remains the gold standard for confirming tubal patency and should be used when definitive diagnosis is required 2, 1.
Clinical Context
When hysteroscopy is performed for other indications (such as evaluating the uterine cavity for polyps, fibroids, or adhesions), observing fluid in the POD can provide suggestive evidence of at least unilateral tubal patency, but this should not replace formal tubal patency testing 1, 5.
Transvaginal ultrasound alone (without contrast) is not effective for documenting tubal patency, though it can detect hydrosalpinx with 86% sensitivity 2, 6.