Medical negligence

My daughter had admitted to one hospital for the ailment of stomach pain and later operated for stomach obstruction. During the treatment and before preliminary treatment all the test conducted on various illness including liver it was fine and no other complications were reported in the reports. But after the operation some complication is developed and her liver started deteriorating and later asked us to shift to liver specialty hospital in Mumbai from Baroda (Gujarat). But the condition was worst, we could not save her life. We suspect the negligence from the first hospital (Baroda) in the treatment as there was no sign of any illness previously or any symptom of liver related disease. This was confirmed at all the hospital where various tests for knowing the reason for liver failure is done and all the tests shows negative results. So please give your valuable advice how to proceed against the hospital for the negligence and hence lost our daughter - 20 year engineering final year, college topper - had no other illness or have any such medical history earlier.