The kidneys are two bean-shaped organs found on the left and right sides of the body. They filter the blood in order to make urine, to release and retain water, and to remove waste and nitrogen (the excretory system). Each kidney accounts for 50% of a person's blood filtration. It is possible to survive with only one. Carcinoma, one form of tumor cancer, weakens blood filtration.
While most animals have kidneys, the kidney item can only be acquired by harvesting them from human pawns through the surgery bill. This bill requires 1 of any type of medicine to perform. Success chance is dependent on a number of factors, including bed quality, room cleanliness, and doctor skill - specifically the doctor's Medical Surgery Success Chance.
Up to two kidneys can be taken from a healthy patient but any damage, infection, carcinoma or other issue affecting a kidney will prevent harvesting. If both kidneys are taken, the patient will die.
Removing a kidney from a guest or prisoner decreases faction goodwill by 20 points down to a max of -100, and creates a -5 mood to your pawns for 8 days due to "someone's organ harvested", stacking up to 5 times, with a 0.75x multipler. Surgery on your own people gives "colonist's organ harvested" which is statisically identical to the previous mood penalty, however both types of mood penalties stack. The original owner of the organ receives a -30 mood penalty for 8 days. Lastly if the pawn is killed by taking the organ, the members of the colony gets an additional a -6 for 5 days.
Pawns with the Bloodlust and Psychopath trait are not affected by the harvesting of other people.
While kidneys can be harvested from prisoners, guests and your own colonists, generally it is preferable to harvest from prisoners that you don't intend to recruit or sell into slavery. Their faction is generally already hostile, their mood is not as important as a colonists and the significant loss in Blood Filtration is less important. It is also recommended to pick either colonist harvesting or prisoner/guest harvesting as they two debuffs stack and only the like debuffs have the stack multiplier i.e. harvesting one colonist and one prisoner will have a larger net debuff than harvesting from two colonists or two prisoners.
There are two primary reasons to harvest an organ - trade and transplantation.
Kidneys can be damaged by disease, drugs, or combat. The damage to a single kidney reduces Blood Filtration by up to 50%. This has two primary effects - the first is a 5% reduction in Consciousness which in turn affects almost every task a pawn can perform - making them slightly worse in basically every way.
The second, perhaps more urgent, effect is a 25% reduction in Immunity Gain Speed. This significantly reduces the survivability of infections and common diseases such as the Flu. If a pawn has an immunity gain speed of 58% or lower, such as from two damaged kidneys, or a damaged kidney and Liver, then the flu will be invariably fatal.
Lastly, while unlikely, if the remaining kidney is destroyed the pawn will instantly die.
Thus, it is recommended to replace damaged, destroyed or missing kidneys on valuable colonists as soon as possible. For most pawns. the mood penalty is worth replacing the organ but this may not apply to more disposable pawns.
Each kidney is worth 250 silver, and only has a mass of 1. The abundant supply of raiders means that, if the mood penalty can be withstood, a significant amount of value can be extracted from them without having to keep prisoners and wait for a Slave Trader or Royal Tribute Collector .
- 1x Lung worth 400
- 1x Kidney worth 250
- 1x Heart worth 500
For a total of 1150.
If the Heart is damaged, the liver can also be supplemented for the same value. If that is also unavailable, the second lung and then the second kidney are the optimal options. Removing the heart, liver, second lung or second kidney are all fatal and prevent further harvesting.
If unwilling to organ murder the donor, the best option is harvesting the
- 1x Lung worth 400
- 1x Kidney worth 250
For a total of 650.