Tubal dilatation can occur in different pathological situations e.g tubal endometriosis, pelvic adhesion, pyosalpinx, ectopic pregnancy, transient during menstruation in case of narrow cervical os, as obstructive sequelae of tubal or uterine cornual masses and in imperforate hymen and other causes of impaired menstrual drainage.

The nature of accumulated fluid will help to differentiate, it is fluidy in simple occlusion due to adhesion, pus in pyosalpinx and PID, blood in malignancy ectopic pregnancy, imperforate hymen, tubal torsion and endometriosis and finally caseous in TB.

The different fluid will give different signal in MRI help to differentiate them; so that MRI has the upper hand over CT in diagnosis of the fluid nature and better natural tissue contrast resolution.

It is a must to differentiate endometriosis from other causes to avoid many troubles in treatment.

HSG give characteristic appearance of the dilated tube.

US will help to retrieve the nature of aspirated fluid using oblique course of the needle to avoid spillage of the fluid in the peritoneal cavity , if you suspect endometriosis it is better to avoid aspiration.

You must scan the urological system as renal malformations or agenesis may indicate Mullerian duct anomalies.