Does Internal Ultrasound Break Fast?
Question

I am 15 years old and during the last three months my menstrual cycle has not been regular. Now, two days before Ramadan, I have been menstruating continuously for nearly 6 weeks, and the bleeding has not stopped. 
I am certain that this blood is menstrual blood and not Istihadah, as the (female) doctor said. The reason for that is a problem with the female hormones. 
The doctor has made an appointment for me to have an ultrasound to examine and check the state of my ovaries. This date is in the middle of Ramadan, in the morning. 
The problem is that it requires me to break my fast on this day in order to drink water before the ultrasound.
My question is: is it permissible to keep this appointment and is it permissible for me to break my fast on this day, or should I delay the appointment until after Ramadan? Will I be sinning if I do not delay it? 
Please note that the appointments here are very difficult to get and I may wait another month to do this examination.
Praise be to Allah.Does internal ultrasound break the fast?
It is permissible for the sick person not to fast in Ramadan and to make up the days that he did not fast , because Allah says (interpretation of the meaning): “and whoever is ill or on a journey, the same number [of days which one did not observe Sawm (fasts) must be made up] from other days. Allah intends for you ease, and He does not want to make things difficult for you” [Al-Baqarah 2:185]
Istihadah (irregular vaginal bleeding) and ongoing bleeding is a kind of sickness that affects the mind and body, hence there is nothing wrong with carrying out an examination on which the treatment will be based, even if that means that you have to break the fast during the day in Ramadan, although it is better to delay it until night if that is possible. 
It should be noted that x-rays and ultrasounds do not break the fast in and of themselves, so long as the patient does not consume any drink or medicine through the mouth or nose. 
In the answer to question 2299 , we have explained in detail the things that do and do not break the fast of one who is fasting. Please refer to this question. 
If the examination requires drinking water or taking medicine, and it is possible to do that before Fajr, then do that. Otherwise it is permissible for you to break the fast. 
Maximum length of menses 
The maximum length of menses according to most of the scholars is 15 days , and it is not possible for it to be any longer than that. Based on that, what the doctor told you is correct, that the bleeding you are experiencing is Istihadah and not menstrual blood.
And Allah knows best.