The magical “floating” kidney

I started writing this up as a “Lesson from History”, because floating kidney (or “nephroptosis”) was big in the late 19^th century, and I thought that the condition was no longer taken seriously. In researching this however, I found that surgery for this condition is having a resurgence thanks to laparoscopic (keyhole) surgery. To a man with a hammer, everything looks like a nail.

This review of floating kidney from 1997 tells us that this diagnosis was once very common, and that there have been nearly 200 different operations described since the late 1800s including removal of the kidney, but most of the operations are forms of nephropexy (tying down the kidney). At the end of the 19^th century, surgery for floating kidney was the most common procedure performed by urologists.

Symptoms

Floating kidney has been associated with multiple causes, and blamed for wide variety of symptoms (including symptoms from damage to surrounding organs, nervous weakness, urinary tract infections, depression and irritability), and the condition has been described as being present in up to 20% of people without symptoms.

This report from 2001 of a series of patients treated with nephropexy noted the following symptoms:

Are we expected to believe that this questionable condition is capable of causing all of these symptoms? Hypertension (high blood pressure)? I am surprised that only one patient had hypertension, given how common it is.

Diagnosing

Floating kidney was initially diagnosed by feeling the abdomen, but with more modern imaging, movement of the kidney has been detected by dye injections, CT scans, Doppler imaging and bone scans. The diagnostic criteria have been tightened (more than 5cm movement of the kidney between lying down and sitting) as have the classification of the condition and the indications for surgery. The diagnostic criteria have been set without any reference to how much a kidney normally moves, and without any correlation with symptoms.

Treatment

Surgery for floating kidney (nephropexy) has always been controversial, with one early critic commenting that the biggest complication of nephroptosis (floating kidney) is surgery. Even at its peak, there were skeptic urologists who denied the condition existed. Surgery was not the only treatment though, with good relief being demonstrated with the use of various corsets that push the kidney upwards.

Controversy (and the high complication rate from surgery) led to a decline in the diagnosis and treatment of this condition after the 1920s. Since the 1990s however, there have been many reports of nephropexy being done laparoscopically.

The evidence

This review from 2008, like the 1997 review, notes the reappearance of the diagnosis of nephroptosis, and suggests that better diagnostic criteria, along with minimally invasive techniques, allows surgical correction to be performed in selected patients. The authors note that despite any comparative studies and a lack of standardisation of the surgery, laparoscopic [keyhole] nephropexy “will remain the standard therapy”. The 2008 review (along with another review from 2004, and other recent reports, including one using robots) describe “clearly” favourable results from surgery. I don’t buy it, for two reasons.

1. The diagnosis

The diagnosis has never been established. I hear about movement, impaired kidney function, blocked flow, blood in the urine, and a myriad of “classical” symptoms, but nothing has been produced that reliably attributes any symptoms to a kidney that moves more than 5cm. We need to see a study showing that symptoms (whichever ones we choose) are more common in people whose kidneys move >5cm than those whose kidneys move <5cm.

2. The treatment

The treatment has never been validated. I’m not even talking about placebo RCTs; any comparative study would satisfy me for this particular topic. Compare it to psychological counselling or chiropractic for all I care, but compare it to something, otherwise we don’t know if the patients got better as a result of the surgery or not. And what about the abnormal kidney function? That made it sound serious, but they didn’t even test it post-operatively, so we don’t know if there was any improvement. Most of the time, we don’t even know if the kidney stopped ‘floating’. Doing a handful of cases and saying that most of the patients felt better afterwards just doesn’t cut it science-wise (although it is good enough for most surgeons).

Then how do I explain the (roughly) 90% favourable results? Firstly, I don’t even know how “favourable” is defined or what is being measured, but either way, the answer is the same: most people (particularly those with vague symptoms and no clear diagnosis) get better after any treatment, just ask the homeopaths.

Diagnosis of convenience?

It is quite possible that patients with non-specific low back pain and lumbar pain are being diagnosed with this condition by virtue of the fact that they are sitting in the urologist’s office at the time. The same patient in a spine surgeon’s office might have had been given a spinal diagnosis. If you don’t believe that doctors fit patients into their own paradigm (i.e. diagnose what they are familiar with) then read this blog post.

The bottom line

This is a great example of the how myths spread through a supposedly scientific community. Once a procedure has been done enough times and published, it is accepted as reasonable. Then all you need to do is keep changing (“tightening”) the criteria for diagnosis and treatment (to explain any bad results from "the old" technique), and keep reporting “favourable” results from patients in non-comparative studies. Easy.

PS: Before any urologists misinterpret this article and start commenting, please note that I am not criticising urologists or urology in general. This is an example of what happens in many fields of medicine. I expect that most urologists do not consider this a valid diagnosis or treatment, but there are clearly some who do.