Indeed. Medical ninjutsu is also deeply rooted in fuuinjutsu, as the knowledge of the human body that you gain from mastering it allows you to better do things such as placing seals on a living medium and even purging the body of yin and yang energies from foreign sources.
Moving on, we'll. begin with one of the basic abilities of medical ninjutsu that doesn't have a technique. This is known as Shindan or Diagnosis. Basically, this is just the ability to use outside knowledge in order to work out what injuries are present and how to heal them.
Long version:
A Medical Ninja needs to start somewhere and that somewhere is detecting the issue with your patient. Shindan or diagnosis is the first step in treatment; understanding the problem. With this skill, you use your hands to carefully probe a patient for problems that you might not be able to see. Contact with the patient will initially be needed but with time becomes optional. Despite this, you'll always need close proximity between your patient and your hands. This technique is performed by approaching the patient and slowly running both hands over his or her body, using your chakra to examine the body and looking for signs of injury that may not be visible to the naked eye. It can detect any physical alteration to the body (internal or external wounds, lesions, tumors, fractures, diseases, etc) as well as its composition (glucose levels, iron levels, antibodies, etc ) and vital signs (blood pressure, heart rate, temperature, pain levels, breathing, oxygen saturation, etc).
A student of Medical Jutsu will require several minutes to assess all the details but a medical ninja will be able to do so in mere moments. To help less experienced ninjas or to aid in complex cases, direct contact is often used as well as chakra transmitting mediums such as water, wood, etc.
Mental injuries such as psychosis, depression, bipolar disorder, etc can be determined as well. In this case, however, scanning the patient's head is necessary. By scanning the various hormones, chemicals as well electrical currents that make up the inner working of the brain, the medical ninja can detect any imbalance and to what it might be due. He cannot read minds but he can understand if there is a disease or a Genjutsu present.
Additionally, all medical ninjas can use this skill to sense the patient's chakra flow. It's by sensing the chakra flow that most of the time injuries and diseases are noticed and diagnosed. Ninjas have their physical being greatly intertwined with their chakra, making so that an injury in one will result in changes to the other.
Finally, after gaining mastery over medical jutsu, a medical ninja becomes even able to examine dead bodies, determining the cause and time of death.
Let me just explain how Shindan works a bit better, for everyone.
The idea behind it is that you will send your chakra through another body (your hands are the main focus here and its through its tenketsu that you'll release the chakra) and then will it to return to you with the information you need. That means that it doesn't matter whether you will touch the person or not or the location of your initial scan at all; the chakra will find the root of the problem and the manifestation of it. This is the information you require.
You can use chakra transmitting mediums, such as water, to improve your diagnosis and its effectiveness. The easier it is for your chakra to enter the body of the patient and return, the more information you'll be able to attain. Water has the innate ability to assist us in transmitting our chakra to better diagnose a patient. Some jutsu utilizes water to assist in healing, stemming from RL cultures where water is seen as a healing element.
Now, to achieve this you need advanced chakra control and practice. Too much chakra and you risk harming the patient. Too little and you might not get enough information out of it.
Skills, KGs, and abilities might help in this procedure
Any advanced sensory enhancement helps the ninja acquire information in a more detailed manner, faster and without needing so much time. The main examples are:
-Sharingan: The ability to see your chakra flow and its characteristics as well as the ability to gain advanced visual perception in general helps to better identify the issues with the patient.
-Byakugan: Perhaps the most useful of all the abilities that can help a medical ninja, the Byakugan allows you to see inside the body, piercing through the flesh and looking at the core issue in detail. Additionally, because you can see the chakra circulatory system completely and in detail, you can gauge the extent of the damage and if it somehow has anything to do with his chakra flow.
-Rinnegan: Seems to have the same/similar perception to the Byakugan and Sharingan in that it can see chakra and chakra flow, but it doesn't grant you the ability to see the chakra network and tenketsu to the same detail as the Byakugan.
-Chakra Sensing: As said above, most injuries and diseases affect the chakra flow. By being able to sense disturbances in the chakra flow of your patients you are able to better understand their nature and extents.
-Enhanced Hearing: This can help you better evaluate biological functions such as breathing, heart function, intestinal function, blood circulation, blood pressure, etc.
-Emotion Sensing: While we talk about injuries of the flesh, the medical ninja also needs to treat injuries of the mind, often associated with Genjutsu. To better do this, sensing the emotions of your targets might help greatly.