The phrase “living without” an organ refers to survival being possible after its necessary surgical removal or failure. This does not imply the organ was useless, but rather that its function can be compensated for by other parts of the body, medical intervention, or significant lifestyle adjustments. The human body possesses remarkable redundancy and adaptive capacity, allowing it to continue functioning even after the removal of structures that perform important, but not immediately life-sustaining, roles.
Paired Organs Where Redundancy Allows Survival
The body has several paired organs where the loss of one unit permits the remaining counterpart to assume the entire functional workload. The kidneys are the most commonly cited example, as they filter waste products and excess fluid from the blood to maintain chemical balance. When one kidney is removed, the remaining one enlarges and increases its filtration capacity.
This adaptation allows the single kidney to perform the work normally shared by two. While this can lead to a slightly increased long-term risk of conditions like high blood pressure, most people with one healthy kidney live normal, active lives. The lungs also demonstrate this redundancy, as the complete removal of one lung (pneumonectomy) or the removal of a single lobe (lobectomy) is survivable. The remaining lung tissue expands and the chest cavity shifts to fill the space, which helps maintain adequate gas exchange.
Accessory Organs and Storage Units
Certain single organs perform specialized functions, such as storage or filtering, that can be entirely taken over by other systems upon removal. The spleen, located in the upper left abdomen, filters blood, removes old red blood cells, and plays a role in the immune system. After its removal (splenectomy), the liver and bone marrow compensate for the blood-filtering duties.
Other lymphoid tissues take over the spleen’s immune functions, though patients are often vaccinated against certain bacterial infections. The gallbladder is another storage unit that can be easily removed, most often due to painful gallstones. Its function is to store and concentrate bile, which is continuously produced by the liver to aid in fat digestion. Without the gallbladder, bile flows directly from the liver into the small intestine, and most people report little difference in their ability to digest food.
The urinary bladder is a muscular sac that stores urine produced by the kidneys before excretion. Following a complete removal (cystectomy), the urinary system must be rerouted. One common alternative is the ileal conduit, which uses a segment of the small intestine to create a channel exiting through a stoma on the abdomen, requiring an external collection bag. Another option is a neobladder, an internal pouch constructed from the intestine and connected to the urethra, allowing for voluntary control.
Functionally Non-Essential Structures
Some structures are classified as non-essential because their removal does not require significant compensation or cause noticeable long-term functional change. The appendix, a small pouch attached to the large intestine, may function as a reservoir for beneficial gut bacteria. Despite this minor role, its removal (appendectomy) is one of the most common abdominal surgeries and results in no change in overall health or digestive function.
Similarly, the tonsils and adenoids, rings of lymphoid tissue in the throat, serve a role in the immune system by trapping pathogens. When chronically infected, they are often removed in a tonsillectomy or adenoidectomy. The body’s vast network of other lymph nodes and immune tissues readily compensates, meaning their absence is harmless to the immune system’s overall function.
Major Gastrointestinal and System Removals
The removal of large, single organs or major sections of the digestive system is survivable but necessitates lifelong management and adaptation. The stomach, which begins digestion by mixing food with acid and enzymes, can be partially or completely removed (gastrectomy). Surgeons connect the esophagus directly to the small intestine, bypassing the stomach’s functions.
Patients must adopt a feeding pattern of small, frequent meals to avoid dumping syndrome, a rapid rush of food into the small intestine. The loss of the stomach also eliminates a substance needed for Vitamin B12 absorption, requiring patients to receive lifelong B12 injections or supplements to prevent nerve damage and anemia.
The removal of the entire large intestine and rectum (proctocolectomy) is often performed for conditions like ulcerative colitis or colon cancer. This eliminates the colon’s primary function of absorbing water and electrolytes, significantly affecting bowel function.
Two main surgical outcomes exist: a permanent ileostomy, where the small intestine (ileum) drains into an external bag via a stoma, or an internal J-pouch. The J-pouch is created from the small intestine and connected to the anal canal, avoiding an external bag. While these surgeries permit survival, the loss of the large intestine means the stool output is looser, requiring careful attention to hydration and diet.
Reproductive organs like the uterus, ovaries, and testes are not directly necessary for continued biological survival, though they are fundamental to reproduction and hormone regulation. Their removal requires careful management of hormone replacement therapy to mitigate long-term side effects such as bone density loss.