Hello! Your symptoms are characteristic for partial renal or ureter obstruction (described as hydronephrosis). This state may be caused by kidney stones (what is quite often), kidney/ ureter tumor, ureter narrowing, ureter compressions from outside (something inside abdomen cavity). Your ultrasound shows a lobulated complex what should not be neglected (hypoecholic SOL - space occupied lesion is just a cyst, what is very often and not significant in that case). FNAC means fine-needle aspiration cytology. It is a very good idea to rule a cancer out. This procedure looks like a regular injection where a sample of cells is being aspirated and can be exterminated under a microscope. It is very important for you to find what is wrong with your kidney, as hydronephrosis is a pathological process which destroys your kidney. Hope this will help