Oligohydramnios and megacolon in a fetus with vesicorectal fistula and anal-urethral atresia: A case report Mordechai Hallak, MD: Alexander A. Reiter, MD," Leon G. Smith, Jr., MD," Gary A. Dildy III, MD: and Milton 1- Finegold, MD b Houston, T exas Severe oligohydramnios and extremely dilated bowel filled with hyperechogenic material floating in fluid were the ultrasonographic findings in a fetus at 27 weeks' gestation. Vesicorectal communication and urethral·anal atresia permitted urine to empty into the colon, causing megacolon, oligohydramnios, and markedly increased intraabdominal pressure resulting in pulmonary hypoplasia. (AM J OaSTET GVNECOl 1992;167:79·81.)
Key words: Oligohydramnios, fetal vesicorectal fistula, fetal megacolon, pulmonary hypoplasia
Malformations of the urogenital sinus are often associated with oligohydramnios and cystic dilatation of various segments of the urinary tract. We present the first case to our knowledge that describes the prenatal ultrasonographic findings of a fetus with anal-urethral obstruction and spontaneous decompression of the urinary tract into the colon through a vesicorectal fistula. Autopsy findings were helpful in making the clinical-pathophysiologic correlations. Case report A 21·year-old primigravid woman was referred to our prenatal diagnostic center at 27 weeks' gestation because of severe oligohydramnios. She was exposed to parvovirus B-19 during the first trimester of her pregnancy. No rash or fever was noted, yet laboratory tests showed elevated maternal serum parvovirus B-19 IgG antibodies and low levels of immunoglobulin M, consistent with recent exposure or infection. The ultrasonographic examination showed severe oligohydramnios, elevated diaphragms, compressed chest, and markedly distended abdomen and bowel. The abdominal cavity was completely occupied by a large cystic structure containing fluid and hyperechogenic substance (Fig. 1). Peristalsis-like waves were noted to be present within the mass . Kidneys and bladder appeared normal, and no other abnormalities were identified. The differential diagnosis included the conditions that are known to cause fetal intraabdominal From the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology,' and the Department of Pathology/ Baylor College of Medicine. Received for publication April 23 , 1991; ,·evised September 4, 1991 ; accepted October 8, 1991. Reprint ,·equests: Mordechai Hallak , MD, Division ofMaternal-Fetal Medicine, Department of Obstetrics and Gynecology, Wayne State UniveHity! Hutzel Hospital, 4707 SI. Antoine Boulevard, Detroit, MI 48201. 611 /34304
Fig. 1. Ultrasonography of fetal abdomen . Arrows show outline of distended bowel filled with floatin g hyperechogenic material.
calcifications. Meconium peritonitis was the leading consideration, although the floating nature of the hyperechogenic material was atypical. Other possibilities were tumors (hemangioma, hemangioendothelioma, hepatoblastoma, teratoma, and metastatic neuroblas-
79
80 Hallak et al.
July 1992 Am J Obstet Gynecol
Fig. 2. Autopsy findings of extremely distended colon in association with urethral obstruction and vesicorectal fistula.
toma) and congenital infection (toxoplasmosis, cytomegalovirus). In an attempt to establish the diagnosis the patient was offered amniocentesis and cordocentesis for karyotype determination, as well as culture and serologic testing for cytomegalovirus, toxoplasmosis, and parvovirus. It was also intended to evaluate intestinal isozymes of alkaline phosphatase in amniotic fluid, as well as to perform molecular genetics studies for diagnosis of cystic fibrosis. However, the patient declined any invasive diagnostic procedures. Serial ultrasonographic examinations continued to show the large echogenic abdominal mass and severe oligohydramnios. At 36 weeks' gestation she was admitted to the hospital in active labor. A 2650 gm male infant was delivered by emergency cesarean section for fetal distress. Apgar scores were 1 and 3 at 1 and 5 minutes, respectively. The infant was noted to have Potter's facies, lower-extremity deformation, markedly distended abdomen, imperforate anus, and ambiguous genitalia. Soon after delivery the infant was intubated and ventilated for respiratory insufficiency. Resuscitation was pursued after an episode of cardiac arrest, but the infant eventually died 4 hours after birth. The final pathologic diagnoses included pulmonary hypoplasia, most likely as a secondary effect of the extremely distended colon (Fig. 2) and oligohydramnios. The diaphragms were elevated to the level of the third rib bilaterally. The colon was filled with watery, flocculent, yellowish green material identified as a mixture
of meconium and urine. A fistula was identified between the distal bladder-proximal urethra to the rectum, and anal-urethral atresia was noted. Normal kidneys and ureters, normal penis, and undescended left testes were seen. Neonatal blood revealed a normal 46,XY karyotype. Comment
During embryogenesis the cloaca is normally divided by a sheet of mesenchyme, the urorectal septum, into the urogenital sinus anteriorly and the rectum and upper anal canal posteriorly.' This process is completed by 6 weeks' gestation. In some cases, like the one presented, incomplete separation of the cloaca by the urorectal septum occurs. This type of malformation consists of anorectal agenesis with a fistula to the proximal urethra in male fetuses or the vagina in female fetuses. The prevalence of congenital abnormalities of the anus and rectum in general is approximately 1 in 5000 newborns. However, the prevalence of anorectal agenesis is even less. The associated urethral atresia in this case is more unique. It caused a diversion of urine into the colon and led to lethal complications, such as oligohydramnios and hypoplastic lungs. This case presented a diagnostic dilemma to the perinatologist and the pediatric surgeon. This entity should be added to the differential diagnosis of fetal
Fetal vesicorectal fistula
Volume 167 Number I
abdominal mass as seen by ultrasonography. The ultrasonographic findings were hyperechogenic material floating in an abdominal mass and severe oligohydramnios in the presence of normal-appearing kidneys, ureters, and bladder. Persistent vesicorectal communication with anal and urethral atresia permitted urine to empty into and distend the entire colon. The mixture of meconium and urine produced the ultrasonographic picture of hyperechogenic material floating in fluid. The diversion of urine protected the kidneys and ureters from obstructive dysplasia and hydronephrosis-hydroureter. However, severe oligohydramnios, elevated diaphragms, and thoracic compression probably led to pulmonary hypoplasia and neonatal death. This malformation was considered a sporadic event not related to a genetic disorder, infectious etiology, or specific teratogens. There does not appear to be a tem-
81
poral relationship between the documented maternal parvovirus infection and the malformation that led to lethal secondary consequences. There have been no reports of such an association. 2 Prenatal recognition of this entity at an early stage might permit operative urinary diversion. In theory, urine diverted into the amniotic cavity could prevent oligohydramnios, bowel distention, or pulmonary hypoplasia. REFERENCES I. Moore KL. The digestive system. In: Moore KL, ed. The
developing human: clinically oriented embryology. Philadelphia: WB Saunders, 1982:248-52. 2. Anderson Lj, Hurwitz ES. Human parvovirus B19 and pregnancy. In: Freij Bj, Sever jL, eds. Clinics in perinatology: infectious complications of pregnancy. Philadelphia: WB Saunders, 1988;15:273-86.
Key words: Oligohydramnios, fetal vesicorectal fistula, fetal megacolon, pulmonary hypoplasia
Malformations of the urogenital sinus are often associated with oligohydramnios and cystic dilatation of various segments of the urinary tract. We present the first case to our knowledge that describes the prenatal ultrasonographic findings of a fetus with anal-urethral obstruction and spontaneous decompression of the urinary tract into the colon through a vesicorectal fistula. Autopsy findings were helpful in making the clinical-pathophysiologic correlations. Case report A 21·year-old primigravid woman was referred to our prenatal diagnostic center at 27 weeks' gestation because of severe oligohydramnios. She was exposed to parvovirus B-19 during the first trimester of her pregnancy. No rash or fever was noted, yet laboratory tests showed elevated maternal serum parvovirus B-19 IgG antibodies and low levels of immunoglobulin M, consistent with recent exposure or infection. The ultrasonographic examination showed severe oligohydramnios, elevated diaphragms, compressed chest, and markedly distended abdomen and bowel. The abdominal cavity was completely occupied by a large cystic structure containing fluid and hyperechogenic substance (Fig. 1). Peristalsis-like waves were noted to be present within the mass . Kidneys and bladder appeared normal, and no other abnormalities were identified. The differential diagnosis included the conditions that are known to cause fetal intraabdominal From the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology,' and the Department of Pathology/ Baylor College of Medicine. Received for publication April 23 , 1991; ,·evised September 4, 1991 ; accepted October 8, 1991. Reprint ,·equests: Mordechai Hallak , MD, Division ofMaternal-Fetal Medicine, Department of Obstetrics and Gynecology, Wayne State UniveHity! Hutzel Hospital, 4707 SI. Antoine Boulevard, Detroit, MI 48201. 611 /34304
Fig. 1. Ultrasonography of fetal abdomen . Arrows show outline of distended bowel filled with floatin g hyperechogenic material.
calcifications. Meconium peritonitis was the leading consideration, although the floating nature of the hyperechogenic material was atypical. Other possibilities were tumors (hemangioma, hemangioendothelioma, hepatoblastoma, teratoma, and metastatic neuroblas-
79
80 Hallak et al.
July 1992 Am J Obstet Gynecol
Fig. 2. Autopsy findings of extremely distended colon in association with urethral obstruction and vesicorectal fistula.
toma) and congenital infection (toxoplasmosis, cytomegalovirus). In an attempt to establish the diagnosis the patient was offered amniocentesis and cordocentesis for karyotype determination, as well as culture and serologic testing for cytomegalovirus, toxoplasmosis, and parvovirus. It was also intended to evaluate intestinal isozymes of alkaline phosphatase in amniotic fluid, as well as to perform molecular genetics studies for diagnosis of cystic fibrosis. However, the patient declined any invasive diagnostic procedures. Serial ultrasonographic examinations continued to show the large echogenic abdominal mass and severe oligohydramnios. At 36 weeks' gestation she was admitted to the hospital in active labor. A 2650 gm male infant was delivered by emergency cesarean section for fetal distress. Apgar scores were 1 and 3 at 1 and 5 minutes, respectively. The infant was noted to have Potter's facies, lower-extremity deformation, markedly distended abdomen, imperforate anus, and ambiguous genitalia. Soon after delivery the infant was intubated and ventilated for respiratory insufficiency. Resuscitation was pursued after an episode of cardiac arrest, but the infant eventually died 4 hours after birth. The final pathologic diagnoses included pulmonary hypoplasia, most likely as a secondary effect of the extremely distended colon (Fig. 2) and oligohydramnios. The diaphragms were elevated to the level of the third rib bilaterally. The colon was filled with watery, flocculent, yellowish green material identified as a mixture
of meconium and urine. A fistula was identified between the distal bladder-proximal urethra to the rectum, and anal-urethral atresia was noted. Normal kidneys and ureters, normal penis, and undescended left testes were seen. Neonatal blood revealed a normal 46,XY karyotype. Comment
During embryogenesis the cloaca is normally divided by a sheet of mesenchyme, the urorectal septum, into the urogenital sinus anteriorly and the rectum and upper anal canal posteriorly.' This process is completed by 6 weeks' gestation. In some cases, like the one presented, incomplete separation of the cloaca by the urorectal septum occurs. This type of malformation consists of anorectal agenesis with a fistula to the proximal urethra in male fetuses or the vagina in female fetuses. The prevalence of congenital abnormalities of the anus and rectum in general is approximately 1 in 5000 newborns. However, the prevalence of anorectal agenesis is even less. The associated urethral atresia in this case is more unique. It caused a diversion of urine into the colon and led to lethal complications, such as oligohydramnios and hypoplastic lungs. This case presented a diagnostic dilemma to the perinatologist and the pediatric surgeon. This entity should be added to the differential diagnosis of fetal
Fetal vesicorectal fistula
Volume 167 Number I
abdominal mass as seen by ultrasonography. The ultrasonographic findings were hyperechogenic material floating in an abdominal mass and severe oligohydramnios in the presence of normal-appearing kidneys, ureters, and bladder. Persistent vesicorectal communication with anal and urethral atresia permitted urine to empty into and distend the entire colon. The mixture of meconium and urine produced the ultrasonographic picture of hyperechogenic material floating in fluid. The diversion of urine protected the kidneys and ureters from obstructive dysplasia and hydronephrosis-hydroureter. However, severe oligohydramnios, elevated diaphragms, and thoracic compression probably led to pulmonary hypoplasia and neonatal death. This malformation was considered a sporadic event not related to a genetic disorder, infectious etiology, or specific teratogens. There does not appear to be a tem-
81
poral relationship between the documented maternal parvovirus infection and the malformation that led to lethal secondary consequences. There have been no reports of such an association. 2 Prenatal recognition of this entity at an early stage might permit operative urinary diversion. In theory, urine diverted into the amniotic cavity could prevent oligohydramnios, bowel distention, or pulmonary hypoplasia. REFERENCES I. Moore KL. The digestive system. In: Moore KL, ed. The
developing human: clinically oriented embryology. Philadelphia: WB Saunders, 1982:248-52. 2. Anderson Lj, Hurwitz ES. Human parvovirus B19 and pregnancy. In: Freij Bj, Sever jL, eds. Clinics in perinatology: infectious complications of pregnancy. Philadelphia: WB Saunders, 1988;15:273-86.
