3.Female gender, Lax musculature of abdomen and obesity are
risk factors for this to happen in a transplanted kidney 30%
4.Patients usually complain of significant nocturnia and not much urination during the day 46%
5.There was a HOUSE MD episode on this diagnosis 30%
Nephroptosis (floating kidney or renal ptosis) is an abnormal condition in which the kidney drops down into the pelvis when the patient stands up. It is more common in women than in men. It can be seen in transplanted kidney as well. Look below for some references. Female gender and lax musculature are risk factors. Given the posture related function of the kidney- patients sometimes only urinate when they are in the lying down position. Most common symptoms although are pain, acute colic episodes, hematuria and nausea and vomiting. And yes, there was a house MD episode of this diagnosis. So all answers are correct.
It is interesting to look at the history of this disorder. The incidence of this might be greater than we think as we often forget this diagnosis. In 19th century, Nephropexy was performed and one of the most common procedure done for nephroptosis and not its almost extinct. One of the articles listed below calls " nephropexy for nephroptosis .. is listed among other ineffective treatments of imaginary diseases". It is more common in females, with right side effecting more(70%) and 10% can be bilateral. The pathophysiology behind this might be: ptosis causing intermittent ureteric obstruction- hydronephrosis( positional), ischemia,traction and simulation of visceral nerves and leading to stones and infections.
When you have acute hydronephrosis associated with this- it is called Dietl's crisis. Transplant kidneys can get this form of obstruction as well. Look below for more details on this entity on references listed.