Reference curves for the normal fetal small bowel and colon diameters; their usefulness in fetuses with suspected dilated bowel

Figures & data

Figure 1. Identification of the largest loop of the colon (coronal plane) at 35 weeks of gestation. Measurement of the short axis of the bowel lumen (inner to inner bowel wall).

Figure 2. Reference charts of small bowel diameter (A) and colon diameter (B) showing raw data (°) and fitted 50th percentile and 95% prediction ranges.

Table 1. Small bowel and colon diameters according to gestational age.

Weeks of gestation	Small bowel diameter (mm)		Colon diameter (mm)
	Mean	95% prediction interval	Mean	95% prediction interval
20	1.7	0.4–3.5	1.8	0.0–4.0
22	2.1	0.7–3.9	2.9	0.8–5.5
24	2.4	0.9–4.3	3.9	1.5–6.7
26	2.7	1.2–4.7	4.8	2.2–7.8
28	3.1	1.4–5.1	5.7	3.0–8.8
30	3.4	1.7–5.5	6.6	3.7–9.8
32	3.8	2.0–5.9	7.7	4.6–11.0
34	4.1	2.2–6.3	8.9	5.6–12.5
36	4.4	2.5–6.7	10.4	6.8–14.3
38	4.8	2.8–7.1	12.3	8.2–16.5
40	5.1	3.0–7.6	14.5	9.8–19.4

Figure 3. Fetal small bowel (A) and colon (B) inner diameter according to gestational age in fetuses with (box, n = 8) and without (circle, n = 20) bowel pathology. Z-scores were calculated relative to the study nomograms in each case. Upper and lower horizontal lines indicate z-scores of two and −2 respectively, that is, the range of ± two SDs from the mean values represented by a z-score of 0. Two cases (*) were antenatally suspected of colon dilatation and are presented in Figure 3(B) but turned out to have small bowel pathology after birth.

Table 2. Summary of cases with bowel pathology.

Case number	estational age at last ultrasound examination	Appearances	Postnatal diagnosis	Outcome
1	30w 6d	Dilated bowel (24 mm), polyhydramion	Intra uterine fetal death at 31 weeks’ gestation, autopsy showed a duodenal web, causing severe dilatation of the proximal duodenum
2	31w 6d	Dilated bowel loops (28 mm)	Meconium ileus, volvulus, small bowel necrosis	Ileal resection, cystic fibrosis
3	31w 0d	Dilated bowel (12 mm), meconium plug, echogenic bowel, polyhydramnion	Meconium ileus, meconiumperitonitis	Ileal resection, cystic fibrosis
4	33w 4d	Dilated bowel (21 mm)	Malrotation and jejunal atresia, biliary atresia	Jejunal resection, failed porto-enterostomy, died due to liver failure
5	34w 3d	Dilated bowel (24 mm), polyhydramnion	Ileal and jejunal atresia with volvulus	Jejunal and ileal resection, died 4 months of age
6	29w 4d	Dilated bowel (18 mm), polyhydramnion	Meconium peritonitis, small bowel necrosis	Jejunal and ileal resection, died 18 h after birth
7	31w 4d	Dilated bowel (20 mm), polyhydramnion	Ileal atresia, volvulus, meconium peritonitis	Ileal resection, now well
8	21w 0d	Echolucent abdominal structure (8.6 mm)	Colonic atresia	Ileocolic anastomosis, now well

w: weeks; d: days.