3-Dimensional Demonstration of Fetal Anal Canal and Sphincter

Abstract

Purpose: To identify the fetal anal canal and sphincter using 3-dimensional (3 D) ultrasound.

Materials and Methods: 3 D volumes of the fetal pelvis were acquired prospectively in 52 fetuses between 10 and 39 gestational weeks. A standard method for evaluating the fetal anal canal and sphincter was developed. Measurements of mucosal and muscular circumferences and the length of the anal canal were taken.

Results: The anal canal was demonstrated in 46 out of 50 patients (92 %). The sonographic characteristics of the anal canal in the axial plane appear like a “target sign” with an echogenic mucosa in the center, the hypoechoic internal sphincter muscle surrounding it and an outer echogenic circle reflecting the external sphincter. Measurements of mucosal and internal sphincter circumferences and the length of the anal canal demonstrated linear growth during pregnancy (p < 0.01). One case of anal atresia was demonstrated.

Conclusion: The fetal anal canal can be visualized when a systematic analysis is performed using a 3 D volume dataset.

Zusammenfassung

Ziel: Der Nachweis des fetalen Analkanals und des Schließmuskels mittels dreidimensionaler (3-D-) Sonografie.

Material und Methoden: 3-D Volumina des fetalen Beckens wurden prospektiv bei 52 Feten zwischen 10 und 39 Schwangerschaftswochen aufgenommen. Eine Standardmethode für die Beurteilung des fetalen Analkanals und Schließmuskels wurde entwickelt. Die Umfänge von Mukosa und Muskeln wurden bestimmt und die Länge des Analkanals vermessen.

Ergebnisse: Der Analkanal konnte bei 46 von 50 Patienten dargestellt werden (92 %). Das sonografische Charakteristikum des Analkanals erscheint in der axialen Ebene als Zielscheiben-Zeichen mit der echoreichen Mukosa im Zentrum, dem umgebenden echoarmen M. sphincter ani internus und einem äußeren Ring, der dem M.sphinter ani externus entspricht. Messungen der Umfänge von Mukosa und M. sphincter ani internus sowie der Länge des Analkanals zeigten ein lineares Wachstum im Schwangerschaftsverlauf (p < 0,01). Ein Fall einer Analatresie wurde nachgewiesen.

Schlussfolgerung: Der fetale Analkanal kann mittels systematischer Analyse eines 3-D-Volumen-Datensatzes dargestellt werden.

Key words

3 D ultrasound - anus - obstetrics

^* Both authors equally correspondet to the manuscript.

• References

• 1 Moon MH, Cho JY, Kim JH et al. In-Utero development of the fetal anal sphincter. Ultrasound Obstet Gynecol 2010; 35: 556-559
• 2 Cuschieri A , EUROCAT Working Group Anorectal anomalies associated with or as part of other anomalies. Am J Med Gen 2002; 110: 122-130
• 3 Quan L, Smith DW. The VATER association. Vertebral defects, Anal atresia, T-E fistula with esophageal atresia, Radial and Renal dysplasia: a spectrum of associated defects. J Pediatr 1973; 82: 104-107
• 4 Black CT, Sherman JO. The association of low imperforate anus and Down’s syndrome. J Pediatr Surg 1989; 24: 92-94
• 5 Torres R, Levitt MA, Tovilla JM et al. Anorectal malformations and Down’s syndrome. J Pediatr Surg 1998; 33: 194-197
• 6 Zlotogora J, Abu-Dalu K, Lernau O et al. Anorectal malformations and Down syndrome. Am J Med Genet 1989; 34: 330-331
• 7 Yuan P, Qiao L, Dai L et al. Spatial distribution of anorectal atresia/stenosis in China: use of two-dimensional graph-theoretical clustering. World J Gastroenterol 2009; 15: 2787-2793
• 8 Jones KL. Smith’s Recognizable patterns of human malformation. 5th ed. Philadelphia: Saunders; 1997: 664-665
• 9 Taipale P, Rovamo L, Hillesmaa L. First-trimester diagnosis of imperforate anus. Ultrasound Obstet Gynecol 2005; 25: 187-188
• 10 Brantberg A, Blaas HG, Haugen SE et al. Imperforate anus: A relatively common anomaly rarely diagnosed prenatally. Ultrasound Obstet Gynecol 2006; 28: 904-910
• 11 Bean WJ, Calonje MA, Aprill CN et al. Anal atresia: a prenatal ultrasound diagnosis. J Clin Ultrasound 1978; 6: 111-112
• 12 Guzman ER, Ranzini A, Day-Salvatore D et al. The prenatal ultrasonographic visualization of imperforate anus in monoamniotic twins. J Ultrasound Med 1995; 14: 547-551
• 13 Grant T, Newman M, Gould R et al. Intraluminal colonic calcifications associated with anorectal atresia. Prenatal sonographic detection. J Ultrasound Med 1990; 9: 411-413
• 14 Lam YH, Shek T, Tang MH. Sonographic features of anal atresia at 12 weeks. Ultrasound Obstet Gynecol 2002; 19: 523-524
• 15 Ramón y Cajal CL, Martínez RO. Defecation in utero: a physiologic fetal function. Am J Obstet Gynecol 2003; 188: 153-156
• 16 Ochoa JH, Chiesa M, Vildoza RP et al. Evaluation of the perianal muscular complex in the prenatal diagnosis of anorectal atresia in a high-risk population. Ultrasound Obstet Gynecol 2012; 39: 521-527
• 17 Khatib N, Belossesky R, Marwan O et al. Fetal bowel calcifications: a sign of anal atresia with rectourethral fistula. J Clin Ultrasound 2010; 38: 332-334
• 18 Chen M, Meagher S, Simpson I et al. Sonographic features of anorectal atresia at 12 weeks. J Matern Fetal Neonatal Med 2009; 22: 931-933
• 19 Hallak M, Reiter AA, Smith Jr LG et al. Oligohydramnios and megacolon in a fetus with vesicorectal fistula and anal-urethral atresia: a case report. Am J Obstet Gynecol 1992; 167: 79-81
• 20 Magriples U, Copel JA. Accurate detection of anomalies by routine ultrasonography in an indigent clinic population. Am J Obstet Gynecol 1998; 179: 978-981
• 21 Elchalal U, Yanai N, Valsky DV et al. Application of 3-dimensional ultrasonography to imaging the fetal anal canal. J Ultrasound Med 2010; 29: 1195-1201
• 22 Dietz HP. Pelvic floor ultrasound: a review. Am J Obstet Gynecol 2010; 202: 321-334
• 23 Lewicky-Gaupp C, Hamilton Q, Ashton-Miller J et al. Anal sphincter structure and function relationships in aging and fecal incontinence. Am J Obstet Gynecol 2009; 200: 559.e1-559.e5
• 24 Bradley CS, Richter HE, Gutman RE et al. Risk factors for sonographic internal anal sphincter gaps 6–12 months after delivery complicated by anal sphincter tear. Am J Obstet Gynecol 2007; 197: 310.e1-310.e5
• 25 Gregory WT, Boyles SH, Simmons K et al. External anal sphincter volume measurements using 3-dimensional endoanal ultrasound. Am J Obstet Gynecol 2006; 194: 1243-1248
• 26 Huisman TA, Kellenbereger CJ. MR imaging characteristics of the normal fetal gastrointestinal tract and abdomen. EJR 2008; 65: 170-181
• 27 Harris RD, Nyberg DA, Mack LA et al. Anorectal atresia: prenatal sonographic diagnosis. Am J Roentgenol 1987; 149: 395-400
• 28 Ben-Neriah Z, Withers S, Thomas M et al. OEIS complex: prenatal ultrasound and autopsy findings. Ultrasound Obstet Gynecol 2007; 29: 170-177
• 29 Bronshtein M, Zimmer EZ. Early sonographic detection of fetal intestinal obstruction and possible diagnostic pitfalls. Prenat Diagn 1996; 16: 203-206
• 30 Ramón y Cajal CL, Martínez RO. Prenatal observation of fetal defecation using four-dimensional ultrasonography. Ultrasound Obstet Gynecol 2005; 26: 794-795
• 31 Corteville JE, Gray DL, Langer JC. Bowel abnormalities in the fetus – correlation of prenatal ultrasonographic findings with outcome. Am J Obstet Gynecol 1996; 175: 724-729
• 32 Muller F, Dommergues M, Aubry MC et al. Hyperechogenic fetal bowel: an ultrasonographic marker for adverse fetal and neonatal outcome. Am J Obstet Gynecol 1995; 173: 508-513
• 33 Belin B, Corteville JE, Langer JC. How accurate is prenatal sonography for the diagnosis of imperforate anus and Hirschsprung’s disease?. Pediatr Surg Int 1995; 10: 30-32
• 34 Valsky DV, Messing B, Petkova R et al. Postpartum evaluation of the anal sphincter by transperineal three-dimensional ultrasound in primiparous women after vaginal delivery and following surgical repair of third-degree tears by the overlapping technique. Ultrasound Obstet Gynecol 2007; 29: 195-204
• 35 Gindes L, Pretorius DH, Romine LE et al. Three-dimensional ultrasonographic depiction of fetal abdominal blood vessels. J Ultrasound Med 2009; 28: 977-988
• 36 Vijayaraghavan SB, Prema AS, Suganyadevi P. Sonographic depiction of the fetal anus and its utility in the diagnosis of anorectal malformations. J Ultrasound Med 2011; 30: 37-45