In medicine, agenesis refers to the failure of an organ to develop during embryonic growth and development due to the absence of primordial tissue. Many forms of agenesis are referred to by individual names, depending on the organ affected:

• Agenesis of the corpus callosum - failure of the Corpus callosum to develop
• Renal agenesis - failure of one or both of the kidneys to develop
• Amelia - failure of the arms or legs to develop
• Penile agenesis - failure of penis to develop
• Müllerian agenesis - failure of the uterus and part of the vagina to develop
• Agenesis of the gallbladder - failure of the Gallbladder to develop. A person may not realize they have this condition unless they undergo surgery or medical imaging, since the gallbladder is neither externally visible nor essential.