There are several reasons for jaundice like hepatitis, blockage of the bile flow and excessive breakdown of red blood cells.
Jaundice in an adult patient can be caused by a wide variety of benign or life-threatening disorders. Organizing the differential diagnosis by prehepatic, intrahepatic, and posthepatic causes may help make the work-up more manageable.

Jaundice Diagnosis
Jaundice is mainly diagnosed by the appearance of patient’s complexion and eyes. In jaundice doctor usually examine the enlargement of spleen and liver. They check up for the abdominal pain. Fever and severity of abdominal pain aids the doctor to distinguish between hepatic and obstructive jaundice.

Any disorder in blood formation can be diagnosed by thorough examination of the blood or the bone marrow, where blood is made. Almost all the results will be revealed by blood test itself but if required then one can go for bone marrow and liver biopsy. The spleen can be assessed by an ultrasound examination or a nuclear scan if the physical examination has not yielded enough information.
Disease in the biliary system can be identified by imaging techniques, of which there are many. X rays are taken a day after swallowing a contrast agent that is secreted into the bile. This study gives sufficient data related to functional as well as anatomical information. The x ray dye can be injected through needle which is pushed straight into the liver or through a scope passed through the stomach that can inject dye into the Ampulla of Vater. CT and MRI scans are very useful for imaging certain conditions like cancers in and around the liver or gall stones in the common bile duct.

In Jaundice breastfeeding, if ever it needs to be discontinued even for a short time. Breast feeding should not be discontinued in order to make diagnosis. If baby is doing well on breast, there is no reason to stop breast feeding. So breastfeeding should be continued.