**3.2. Pelvic kidney**

**3. Renal development variants**

274 Congenital Anomalies - From the Embryo to the Neonate

Definition: one kidney does not form resulting one present kidney and one renal artery.

Pathology: failure of development of only one ureteric bud with normal development on the

Ultrasound findings: we notice an empty renal fossa on axial view; this view should be completed with longitudinal and coronal views. The contralateral kidney is increased in size (>95 percentile)—compensatory hypertrophy. The use of color Doppler shows only one renal artery. Some structures may mimic the second kidney—one is the adrenal gland, and the

• Careful scanning of the fetal abdomen (do not confuse with renal ectopia/do not confuse

• Isolated unilateral kidney has good prognosis and associates rarely with chromosomal

Differential diagnosis: an empty renal fossa may be present in:

**3.1. Unilateral agenesis**

Incidence: 1:1000 [2].

other is the colon.

• Pelvic kidney.

Clinical facts:

• Unilateral renal agenesis.

• Horseshoe kidney (graph).

kidney with adrenal glands).

anomalies (**Figure 2**).

**Figure 2.** Unilateral renal agenesis.

• Crossed renal ectopia.

other side.

Definition: the presence of one kidney in the pelvis; the most common location for ectopic kidney.

Incidence: 1:700–1:1200 [2–4].

Pathology: the kidney forms normally but fails to ascend to the lumbar area. This normally happens between 6 and 10 weeks of gestational age.

Ultrasound findings: the first thing we notice is an empty renal fossa; careful scanning reveals the kidney adjacent to the bladder. The normally positioned kidney shows no compensatory hypertrophy. Amniotic fluid is within a normal range. The use of color Doppler can be helpful—sometimes, you can follow the renal artery to the ectopic kidney, but sometimes a pelvic kidney can have vascularization from the iliac arteries.

Differential diagnosis: empty renal fossa (see above).

Clinical facts:


**Figure 3.** Pelvic kidney.
