That tube you referred to is called the ureter. That's a good dream you had and yes, you can do that. You can use citrine and you can also use bloodstone, which is a type of jasper, and clear quartz, and peridot. Another thing you can do is put the stones directly on her abdomen and then put your hands on top of the stones and visualize
yourself drawing healing energy from the earth and air around you into yourself and then channeling it out through your hand into the stone and then from the stone into her abdomen. Hold that position for about 10 minutes, and only do it once a day. If you don't want to try transferring energy you can just use the stones alone on her, set them on her abdomen while she's relaxing comfortably and leave the stones on her for 10 to 15 minutes, but no longer than that. You can do that once a day.
I emphasize only once a day because if you do these direct contact treatments more than once a day it would be too stressful for her little body to handle since young children are very sensitive to the energies of stones and too much direct contact would be like overdosing from getting too much of a prescribed medicine. However, something else you can do that is even easier, and will be easier on her, is put the stones under her bed or under her mattress
and just leave them there for her to sleep above every night. That is most highly recommended for young children as it is gentle yet continuous healing that won't overload her body with too much crystal energies.
Rinse the stones in cold running water for about 10 minutes once a week to recharge them.
You will find a lot more information about healing with crystals and laying on of hands or crystals here at this topic: viewtopic.php?f=4&t=20109