Ectopic location of kidney—normal variant

The incidence of pelvic kidney is reported as being between 1 in 2200 and 1 in 3000. The normal human kidney migrates to the renal fossa from a pelvic location early in embryonic development, typically before the 10th week of gestation. The congenital failure of this migration results in a pelvic kidney. Although a pelvic kidney is defined as a normal variant, it is associated with Müllerian duct anomalies such as uterine malformation (see Müllerian Duct Anomalies). Pelvic kidney is the most common type of renal ectopia and is typically clinically asymptomatic. However, ectopically located kidneys are at increased risk of urinary tract infection, stone formation, and trauma.

Pelvic kidneys that have a normal reniform appearance can easily be recognized as an ectopic kidney. It is important to check the corresponding renal fossa to confirm the absence of the kidney in its normal location before diagnosing a pelvic kidney. If there are cysts or fluid collections associated with the pelvic kidney, the correct diagnosis may be more challenging, and it is crucial to consider the diagnosis of ectopic kidney with hydronephrosis and hydroureter. The patient may also have an associated uterine anomaly, so a transvaginal gynecologic ultrasound should be included as part of the evaluation.