Fetal chylous ascites may redevelop only after birth

Introduction

Congenital chylous ascites is a condition that is rarely seen. It may appear benign, although serious morbidity or even mortality is possible. We report a case where, very unusually, the origin of the chylous ascites was only revealed when the child was 3 months old.

Presentation of the case

A 24-year-old pregnant woman was seen at 31 weeks’ gestation in an antenatal care center due to an incidental finding of fetal ascites on an antenatal ultrasound. Amniocentesis was performed at 17 weeks of gestation with normal karyotype, 46,XY. Biochemical screening from the mother’s serum showed increasing chorionic gonadotropin levels, which were 5.65 and 7.68 multiples of median, respectively.

By 36 weeks, all the abnormal ultrasound findings had resolved. At 39 weeks’ gestation, a cesarean section was performed due to mild macrosomia. The mother gave birth to a boy weighing 4460 g. No resuscitation of the baby was required. No investigations or treatment for the ascites was undertaken. At the age of 3 months, the baby underwent surgery for bilateral inguinal hernias and hydrocele. During the operation, milky fluid was drained from the hernia sac. Laparoscopy was performed via the inguinal canal, which revealed the presence of the same fluid in parts of the bowel. A total of 200 mL of the fluid was drained from the abdominal cavity. The baby was then transferred to the pediatric department for further investigations.

The ascitic fluid was found to be rich in triglycerides, with a concentration of 42.45 mmol/L, suggesting chyle. No fats were found in the baby’s stools. Syphilis, toxoplasmosis, parvovirus B19, rubella, herpes simplex virus and cytomegalovirus serology results were all negative. Cerebral ultrasound, fundoscopy and chest X-ray results were all normal. Echocardiography showed normal heart anatomy and function. It was decided to replace the baby’s formula feedings with a special infant formula with 50% of its fat content being provided by medium chain triglycerides (MCTs) rather than by natural milk fats. The baby was discharged home 10 days after admission, continuing on this special formula.

Close follow-up in the pediatric clinic was provided and the following investigations were carried out.

Magnetic resonance imaging of the abdomen and chest was performed, which ruled out an intra-abdominal tumor and did not support gut malrotation; no lymphangiectasia or mesenteric cysts were identified; there were no signs of pleural effusion. Lymphoscintigraphy was also performed and showed normal lymphatic system anatomy and drainage. There were no signs of congestion in the lower limbs and no signs of an intra-abdominal lymph leak.

At 6 months of age, the special formula was supplemented with fruit, vegetables and cereals and a mixed infant diet. At 9 months, the special formula was replaced with normal infant formula. Serial ultrasounds were performed on follow-up. At 6 months, with the baby still on the partial MCT diet, there was no longer any evidence of ascites. At the age of 12 months, when he was fed with a normal mixed diet, the follow-up abdominal ultrasound revealed some progression of the ascites. However, by 30 months of age, the free abdominal fluid had completely resolved. The child’s development had been normal, and he had been in good health according to check-ups carried out up to that age.

Discussion

Congenital chylous ascites is a rare condition. Lack of lacteal function (“leaky lymphatics”), a localized leaking lymphatic duct, obstruction of the cisterna chyli, gut malrotation and genetic syndromes have all been reported as possible causes [1] (see Table 1). The term “leaky lymphatics” refers to a functional defect of the lymphatic chain in a case where no structural abnormalities of the lymphatic system were found. Chylous ascites appears transient in many cases and resolves spontaneously within days, weeks or months of life, whereas in some patients the problem persists long beyond this time period. Ascites may be revealed on the antenatal ultrasound. The amount of fluid found varies and may be small in some fetuses. However, after birth, if feedings containing long chain fats are given to the infant, the ascites may quickly worsen. Presentation of ascites in an infant varies from incidental findings in an asymptomatic patient to cases with an extremely large amount of fluid in the peritoneal cavity with significant impact on the functioning of several organ systems including the gastrointestinal tract, lungs, heart and circulation, and urinary system. Multiple therapeutic approaches have been used, including limited treatment with a diet containing MCT and/or octreotide, and surgical treatment including drainage, insertion of peritoneal-caval shunts or repair of an identifiable leak in the lymphatic system. Patients with severe ascites may require intubation and intensive care including mechanical ventilation and oxygen therapy. In general, the prognosis is good in most babies with the ascites completely resolving, all major organs functioning well and normal development. Complications may arise from drainage or surgery. Persisting refractory ascites may require repeated treatments, procedures and hospital admissions, thus interfering with the child’s quality of life. Severe ascites may cause fetal, neonatal or post-neonatal infant death [2–4].

Table 1

Possible causes of congenital chylous ascites.

^aSupporting diagnostic tests: magnetic resonance imaging of the abdomen and evaluation of abdominal effusions.

^bTesting for toxoplasmosis, cytomegalovirus, herpes simplex virus, syphilis, tuberculosis, parvovirus B19 and rubella may be of value.

The case reported here typifies a leaky lymphatics condition. The fetal ascites was mild and appeared to resolve prior to birth. Without clinically evident ascites, follow-up was not considered necessary. However, once enteral feedings containing long chain fats commence, chyle production increases and the resulting increase in flow through the leaky lymphatics results in the intraperitoneal extravasation of chylous fluid. In this patient, closer postnatal follow-up might have enabled an earlier diagnosis. We conclude that congenital chylous ascites may be diagnosed prior to birth but may become more clinically significant only after birth. It is important to understand that the condition may fully develop and be diagnosed only after significant amounts of milk are consumed. Close post-natal follow-up is warranted, and decisions about treatment need to be made, with appropriate procedures ranging from a suitable diet through octreotide or possible surgery.