During the process of normal embryonic gut development, the fetal midgut undergoes a 270° counterclockwise rotation around the axis of the superior mesenteric artery between 4 and 8 weeks of gestation. Partial or complete failure of this rotation during embryogenesis leads to intestinal rotational abnormalities [9, 10]. Intestinal malrotation predisposes to midgut volvulus.
Fetal midgut volvulus is a rare entity diagnosed prenatally [3, 11]. It refers to the twisting of bowel loops around the mesenteric artery. This may lead to catastrophic complications, including intestinal obstruction, bowel ischemia, necrosis, perforation, and peritonitis [1].
Prompt diagnosis is vital to prevent undesirable maternal and fetal outcomes. Intrauterine diagnosis of fetal midgut volvulus is considered difficult and rare in literature [3, 9]. Ultrasound findings of fetal midgut volvulus include dilated intestinal loops and the classic “whirlpool sign” [12]. “Whirlpool sign” in midgut volvulus refers to the winding appearance of the mesentery and superior mesenteric vein wrapped around the superior mesenteric artery [12]. It has a high sensitivity, specificity, and accuracy for the detection of midgut volvulus [8]. Associated findings such as polyhydramnios, decreased fetal movements, and fetal ascites may be encountered [13, 14]. Fetal anemia may be seen in cases of intestinal volvulus. Increased peak systolic velocity (PSV) of the middle cerebral artery (MCA) on Doppler study can be indicative of fetal anemia, especially in the presence of fetal ascites, polyhydramnios, and dilated bowel loops [15]. Bartholmot et al. reported that decreased fetal movements in fetal volvulus was not an accidental finding. Moreover, the presence of a “fluid–fluid level” within the dilated bowel loops improves the diagnostic accuracy of findings on ultrasonography [16, 17]. The presence of a fluid–fluid level in dilated bowel loops indicates the absence of peristalsis and fetal intestinal distress [16].
“Coffee-bean sign” with or without whirlpool sign may be observed in fetuses with midgut volvulus [2, 16, 17]. It occurs in cases with closed-loop bowel obstruction and refers to the coffee-bean-like appearance of closely approximated dilated bowel loops [17, 18]
Detection of fetal midgut volvulus warrants an urgent neonatal surgical intervention. In the absence of associated anomalies, isolated midgut volvulus has a favorable prognosis postsurgery [14].