Kidney Stone#440

Kidney Stone is an unlockable passive item added in The Binding of Isaac: Afterbirth.

• "Matt" refers to Matt Kap, a pixel artist for The Binding of Isaac: Rebirth, who has once been afflicted with a kidney stone.
• A kidney stone is a hard deposit made of minerals and salts that form inside kidneys. It will usually pass through the urethra, which is often a very painful process.
• When Isaac enters a room with half a heart and holding this item, he will leave a small puddle of blood rather than pee.

Bug! If Kidney Stone activates while a charged tear effect such as Tech X or Chocolate Milk is currently charging, the charge will get stuck, unable to fire for a somewhat-short period of time, before eventually having the Kidney stone be released as normal. Tears will then occasionally charge, even if a fire button isn't held down anymore. Bug! With Monstro's Lung and Technology, the stone can be launched but the barrage will not charge Monstro's Lung enough to fire, preventing Isaac from firing at all during the barrage. Bug! If Kidney Stone is fired by picking up trinket, the item description for the trinket will display the tears up from Kidney Stone as one of the trinkets effects. The Binding of Isaac: Rebirth

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