Nephroptosis

Nephroptosis, also known as floating or wandering kidney and ren mobilis, refers to the descent of the kidney more than 5cm or two vertebral bodies when the patient moves from a supine to upright position during IVU ^1-2.

Displacement can also occur medially across the midline, so-called medial nephroptosis ^8,9. A recent case report even demonstrated anterior displacement ¹⁰.

Clinical presentation

It may be present in up to 20% of young, slim females and is mostly asymptomatic ². It is more often seen on the right side, in up to 20%, is bilateral.

Symptoms may include flank pain on standing that is relieved on lying down, with the hypothesis being that movement of the kidney causes intermittent renal tract obstruction ¹. Rarely it can cause intermittent nausea, vomiting, hypotension, oliguria and proteinuria, a syndrome known as Dietl's crisis ⁵. It may occur in childhood as well ^11,12.

Radiographic features

Intravenous urography, renal scintigraphy with various tracers, CT and ultrasound may all allow for the diagnosis (performed supine and upright, lateral decubitus in medial ptosis) ^3,4,8,9.

Colour Doppler ultrasound (CDI) with estimation of renal resistance index (RI) has been shown to be sensitive in detecting renal blood flow impairment and may thus aid in decision for laparoscopic nephropexy ³.

Treatment and prognosis

Laparoscopic nephropexy, usually reserved for cases with vascular and/or obstructive renal impairment, has been shown to be successful in relieving symptoms caused by renal compromise ^3,6,7,12.

Differential diagnosis

After dynamic imaging depicting kidney descent with renal compromise, there is virtually no differential diagnosis. The entity may well be under recognised clinically ^3,4,8.