Abnormal Kidney Size

Abstract

Measurement of fetal kidney size can assist in the diagnosis when a renal abnormality is suspected. Fetal kidney size increases with gestational age. Nomograms are available for kidney length, anterior-posterior diameter, and transverse diameter. This chapter reviews the normal embryologic development of the fetal kidney and includes a systematic approach to the evaluation of a suspected enlarged or small fetal kidney.

Keywords

corticomedullary differentiation, compensatory hypertrophy

Introduction

The fetal kidneys are routinely imaged in the second and third trimester, but they are not usually measured unless an abnormality is suspected. Nomograms are available not only for kidney length ( Table 9.1 ) but also for anterior-posterior diameter ( Table 9.2 ) and transverse diameter ( Table 9.3 ). An abnormality of kidney size can occur as a normal variant, as a physiologic adaptation (i.e., compensatory hypertrophy), as a manifestation of a renal anomaly or tumor, or as a component of a genetic syndrome. If an abnormality of kidney size is suspected, further evaluation may reveal information about underlying pathology and assist with counseling about prognosis.

TABLE 9.1

NOMOGRAM FOR KIDNEY LENGTH IN MILLIMETERS ACCORDING TO GESTATIONAL AGE

Weeks’ Gestation	3rd	10th	50th	90th	97th
14	7.5	8.0	9.3	10.8	11.6
15	8.8	9.5	11.0	12.8	13.7
16	10.2	11.0	12.7	14.8	15.8
17	11.6	12.5	14.5	16.8	18.1
18	13.1	14.1	16.3	18.9	20.3
19	14.6	15.6	18.2	21.1	22.6
20	16.1	17.2	20.0	23.2	24.9
21	17.5	18.8	21.8	25.4	27.2
22	19.0	20.4	23.6	27.4	29.4
23	20.4	21.9	25.4	29.5	31.6
24	21.8	23.4	27.1	31.5	33.8
25	23.1	24.8	28.8	33.4	35.8
26	24.4	26.2	30.4	35.3	37.8
27	25.6	27.5	31.9	37.1	39.7
28	26.8	28.7	33.4	38.7	41.5
29	27.9	29.9	34.7	40.3	43.2
30	28.9	31.0	36.0	41.8	44.8
31	29.9	32.1	37.2	43.2	46.3
32	30.8	33.0	38.3	44.5	47.7
33	31.6	33.9	39.4	45.7	49.0
34	32.4	34.7	40.3	46.8	50.2
35	33.1	35.4	41.1	47.8	51.2
36	33.7	36.1	41.9	48.7	52.2
37	34.2	36.7	42.6	49.4	53.0
38	34.7	37.2	43.2	50.1	53.8
39	35.1	37.6	43.7	50.7	54.4
40	35.4	38.0	44.1	51.2	54.9
41	35.7	38.3	44.5	51.6	55.4
42	36.0	38.6	44.8	52.0	55.7

Data from Chitty LS, Altman DG: Charts of fetal size: kidney and renal pelvis measurements, Prenat Diagn 23:891–897, 2003.

TABLE 9.2

NOMOGRAM FOR KIDNEY ANTERIOR-POSTERIOR DIAMETER IN MILLIMETERS ACCORDING TO GESTATIONAL AGE

Weeks’ Gestation	3rd	10th	50th	90th	97th
14	4.6	5.2	6.5	8.3	9.2
15	5.4	6.0	7.6	9.6	10.7
16	6.2	6.9	8.6	10.9	12.1
17	7.0	7.8	9.7	12.2	13.6
18	7.8	8.7	10.8	13.6	15.1
19	8.6	9.5	11.9	14.9	16.6
20	9.4	10.4	13.0	16.3	18.0
21	10.2	11.3	14.1	17.5	19.4
22	11.0	12.2	15.1	18.8	20.8
23	11.8	13.0	16.1	20.0	22.1
24	12.5	13.8	17.1	21.1	23.3
25	13.2	14.6	18.0	22.2	24.5
26	13.9	15.4	18.9	23.2	25.6
27	14.6	16.1	19.7	24.2	26.6
28	15.2	16.7	20.5	25.1	27.6
29	15.8	17.4	21.2	25.9	28.4
30	16.4	18.0	21.9	26.7	29.2
31	16.9	18.5	22.5	27.3	29.9
32	17.4	19.0	23.1	27.9	30.6
33	17.8	19.5	23.6	28.5	31.2
34	18.2	19.9	24.0	29.0	31.6
35	18.6	20.3	24.4	29.4	32.1
36	18.9	20.6	24.8	29.7	32.4
37	19.2	20.9	25.1	30.0	32.7
38	19.5	21.2	25.3	30.3	32.9
39	19.7	21.4	25.5	30.5	33.1
40	19.9	21.6	25.7	30.6	33.2
41	20.1	21.8	25.8	30.7	33.2
42	20.2	21.9	25.9	30.7	33.2