What is a floating kidney?
A floating kidney, medically known as nephroptosis, is a condition where the kidney moves from its normal position when a person lies flat or stands upright. This movement is abnormal. Although most organs in the abdomen may descend slightly when a person stands upright, the kidneys usually do not move much, almost not at all. Even when the kidneys do move with a change in body position, it rarely ever causes any symptoms and the movement is usually very slight.
A floating kidney is said to be rare but in reality may not be so. It is estimated that some 20% of women may have a floating kidney but only a minority of patients have symptoms. Although the condition is routinely detected during certain diagnostic investigation, it is not often a cause for concern if a person is asymptomatic. Floating kidney (nephroptosis) can occur in both males and females but is far common in women. It tends to affect the right kidney more often than the left.
Floating Kidney Other Names
Floating kidney may also be known as :
- Prolapsed kidney
- Renal ptosis
- Wandering kidney
Floating Kidney Meaning
The medical term for a floating kidney is nephroptosis. This more accurately describes what a floating kidney is because ptosis means drooping, while nephro means kidney. It is important to first understand the normal anatomical position of the kidneys. The location of the right and left kidney does vary slightly apart from just being on opposite sides of the body.
Kidney Normal Position
The right kidney sits slightly lower than the left kidney. Both kidneys are located at the back of the abdominal cavity and slightly to the outer side against the abdominal wall. In the way, the right kidney lies behind the liver while the left kidney sits behind the spleen. The kidneys are between 9 to 13 centimeters long and bean shaped. Somewhat in the middle of the inner border of kidney is the renal hilum where the blood vessels, nerves and the ureter come in and out of the kidney. This is located around the level of the L2 vertebra (right kidney). The left kidney is about 1 centimeter higher. There may be some variation in this position by a few centimeters from person to person.
Fixation of the Kidney
Both kidneyz are attached to the posterolateral (back and outer) abdominal wall by fat and connective tissue known as fascia. The kidney tissue is covered by a capsule. Around this capsule is the perirenal fat. This in turn is surrounded by the renal fascia with another layer of fat over it known as the pararenal fat. The abdominal lining, peritoneum, covers the front of the pararenal fat of the kidney and the transversalis fascia covers the back. In this way the kidney is fairly fixed in its position and well shielded by fat and partly by the last two ribs.
Movement of the Kidney
Although the kidney can move very slightly like when breathing in an out, there is a point where this movement is defined as excessive. In a floating kidney (nephroptosis), the kidney can move more than 5 centimeters (about 2 vertebral bodies) when changing position from lying flat to standing upright. This may not seen like a significant distance. However, it is important to remember that although the kidney may be able to move, the nerves and blood vessels supplying it, as well as the ureter emerging from it, may not be able to move accordingly. This can cause :
- Kinking of the ureter thereby hampering the outflow of urine from the kidney.
- Stretching and stimulation of the nerves supplying the kidney and surrounding tissue.
- Elongation and narrowing of the kidney blood vessels thereby partially restricting blood flow.
It is the occurrence of these events that give rise to the symptoms of a floating kidney. However, with minor disturbances there may not be enough of a disruption to cause any symptoms.
Floating Kidney Causes
Lack of body fat
The exact cause of a floating kidney is unknown and despite various investigations, no abnormality can be detected to explain why this condition occurs. It is more frequently seen in very thin females and is believed that the lack of body fat compromises the support for the kidney, allowing it to fall downwards. This is believed to be the single most important contributing factors for the development of a floating kidney. Excessive weight loss and sudden weight loss may increase the chances.
Stretched or elongated tissue
The tissue that holds the blood vessels as it attaches to the kidney hilum may also be longer than normal. This is believed to contribute to the kidney being able to move front or back, and up and down, to a greater extent than normal. However, most of the support that fixes the kidney in its position comes from the fat and fascia so this allowance is a minimal contributing factor.
There is no evidence to suggest that strenuous physical activity like jumping will cause translocation of the kidney. This is a myth. However, there will be greater movement of the kidney during jumping and other activities where a floating kidney already exists.
Floating Kidney Symptoms
It is estimated that a floating kidney is asymptomatic in about 80% of patients with the condition. This means that there are no symptoms in the majority of cases of a floating kidney. At one time a floating kidney was even reconsidered as to whether it should be categorized as a medical diagnosis because of the inconsistency of symptoms. In fact all too often, the symptoms of a floating kidney when present is temporarily diagnosed as other kidney disorders, gallbladder, bowel and ovarian diseases.
One of the major symptoms of a floating kidney is pain. It is usually described as flank pain or lower abdominal pain. Typically this pain starts or worsens when standing upright and eases or disappears completely when lying flat. Severe physical activity can also worsen the pain.
Changes in urine and urination patterns may also be seen with floating kidney symptoms. This includes :
- Low urine output but not entirely absent as the other kidney is still functioning.
- Hematuria – blood in the urine
- Proteinuria – protein in the urine
In severe cases, there may be stomach flu-like symptoms although a floating kidney is not an infection. These symptoms are largely due to the kidney function being compromised.
- Tachycardia – rapid heart rate
This is a severe manifestation of a floating kidney and along with kidney pain and urinary abnormalities, it is known as Dietl crisis. Medical attention is needed immediately.
Floating Kidney Diagnosis
The presence of the symptoms mentioned above, along with a moving mass which can be felt both by the patient and doctor may raise the suspicion of a floating kidney. A medical history of excessive weight loss or a very thin patient with these symptoms should also raise the question about a floating kidney.
Blood and urine tests may reveal the abnormality in kidney functioning. However, it does not clearly indicate the type of kidney abnormality. In most cases, a floating kidney is diagnosed routinely during imaging studies. When suspected, it can then be diagnosed with the following imaging studies :
- Intravenous urography where a radiocontrast dye is injected into a vein and then an X-ray taken. This is the most effective diagnostic method.
- Ultrasound while sitting upright and lying flat.
- CT (computed tomography) scan which is not very effective as in most cases the kidney will return to the normal position when lying flat.
Floating Kidney Treatment
While medication may provide temporary relief for the symptoms, a floating kidney needs to be treated surgically. However, surgery is only considered where a patient has all the symptoms described above and the diagnosis of a floating kidney is confirmed with intravenous urography. It is important to bear in mind that not every case of floating kidney would require surgery though.
This is one of the favored surgical procedures to affix a floating kidney. It has been done since 1881 but open nephropexy is no longer favored. Instead laparoscopic nephropexy offers fewer complications and a quicker recovery time. Four holes (ports), one of which is for the laparoscope, are made and the kidney is affixed with sutures. The patient is discharged within 2 to 3 days after the procedure provided that there are no post-operative complications.
Circle (U) Nephrostomy
In this procedure, a nephrostomy tube is passed over the 12th rib and inserted through the kidney. The tube basically forms a sling so that the affected kidney is suspended from the 12th ribs. Although it is not widely performed, the results of this procedure have proven to be very promising. It is easy to perform, a quick procedure and has very few complications. Most patients are discharged with 3 days after performing the procedure and almost 80% of patients find relief from pain with this procedure.
Floating Kidney Surgery Video
The video below is of a laparoscopic nephropexy. Sensitive viewers should be aware that the footage may be disturbing.
Article reviewed by Dr. Greg. Last updated on June 4, 2012