Kidney transplantation is the standard treatment for end-stage kidney disease, but patients are often surprised that the two native, non-functioning kidneys are usually not removed. The common assumption is that a failed organ must be taken out to make room for the new one, similar to a heart or liver transplant. However, in the majority of cases, surgeons intentionally leave the recipient’s original kidneys in place. This decision is based on surgical risk, anatomical location, and patient benefit.
Surgical and Anatomical Reasons for Retention
The primary reason for leaving the old kidneys in the body is to avoid unnecessary surgical complications. The native kidneys are located deep within the abdominal cavity, behind the peritoneum, in a space known as the retroperitoneum. Removing them requires a deep, extensive dissection to reach the organs and their major blood vessels, significantly increasing the complexity and duration of the operation. This deep surgical access carries a higher risk of injury to surrounding structures, such as the major abdominal blood vessels and the bowel.
The non-functioning kidneys are typically scarred and surrounded by dense, fibrous tissue, a result of the long-term disease process. Cutting through this scar tissue elevates the potential for uncontrolled bleeding or accidental damage to adjacent organs. Avoiding this major abdominal surgery shortens the overall operative time, reducing the patient’s exposure to anesthesia and lowering the risk of infection and post-operative complications. Since the native kidneys are no longer filtering, their continued presence does not interfere with the new kidney’s job. There is no functional benefit to justify the increased surgical trauma of removal.
Placement of the Transplanted Kidney
The surgical decision to retain the native organs is made possible by placing the new kidney in an entirely different location. Instead of the retroperitoneum, the transplanted kidney is positioned in the lower abdomen or pelvis, specifically in the iliac fossa. This location offers a more accessible and less invasive surgical field. The new organ is easily connected to major blood vessels in this area, namely the iliac artery and iliac vein.
The new kidney’s ureter is then connected directly to the recipient’s bladder, providing a shorter and simpler route for urine drainage. This placement means the new organ does not occupy the same space as the native kidneys, eliminating the need for removal due to spatial reasons. Placing the transplanted kidney superficially in the lower abdomen also makes it easier to monitor its function, including routine ultrasound scans or necessary biopsies.
When Native Kidneys Require Removal
While retention is the standard practice, specific medical conditions necessitate the removal of one or both native kidneys, often before the transplant surgery. One common reason is massive polycystic kidney disease (PKD), where the kidneys become grossly enlarged with cysts. These massive organs can cause chronic pain, recurrent cyst hemorrhage, or exert pressure that limits the space required for the new transplanted kidney. Another indication for removal is uncontrolled, persistent infection, such as chronic pyelonephritis or recurrent urinary tract infections that do not respond to antibiotics. A constantly infected organ is a source of sepsis risk, which is unacceptable in an immunosuppressed transplant recipient.
Severe, refractory hypertension is a third reason, particularly when the native kidneys are believed to be over-secreting renin, a hormone that increases blood pressure. Finally, a confirmed diagnosis of cancer or a high risk of malignancy, such as acquired cystic disease of the kidney, is a clear indication for pre-transplant removal.
The Long-Term Status of Native Kidneys
Once the transplanted kidney begins to function, it takes over the body’s filtration and regulatory duties. The native kidneys, which were already severely damaged, typically begin a process of atrophy, meaning they shrink in size over time. The underlying disease that caused their failure is not cured, and the organs remain dormant and non-functional in their original location.
In most cases, these atrophied native kidneys do not regain function or cause further medical issues for the patient. They are essentially inert tissue, and a patient may live for decades with three kidneys: two small, inactive native kidneys and one fully functional, transplanted organ. While the native kidneys are monitored periodically, they rarely require intervention once the transplant is successful and the patient has stabilized.