Congenital diaphragmatic hernia with multiple malformations in a fetal pig

Technical Summary: Congenital Diaphragmatic Hernia with Multiple Malformations in a Fetal Pig

Problem Statement
Congenital diaphragmatic hernia (CDH) is a well-documented condition in humans, occurring in approximately 1 in 2,000 to 4,000 births, often leading to severe pulmonary hypoplasia and high mortality. While CDH is frequently reported in adult dogs and cats, detailed reports regarding CDH in fetal animals are scarce. Furthermore, the incidence of CDH in animals remains largely unquantified, and the specific presentation of CDH accompanied by a complex cluster of multiple organ malformations in fetal pigs has not been previously documented. This study addresses the gap in veterinary and comparative anatomical literature by reporting a rare case of a fetal pig exhibiting CDH with multiple associated anomalies.

Methodology
The study utilized a single fetal pig specimen obtained from a stock of 1,040 fetal pigs imported from the United States and used for anatomical training. The specimen was a male fetal pig with a crown-rump length of 35 cm. The methodology involved a comprehensive gross anatomical dissection, including thoracotomy and laparotomy, to visualize internal organ positioning and structural integrity. The researchers conducted a systematic examination of the diaphragm, thoracic cavity, abdominal cavity, and pelvic cavity, documenting organ displacement, size discrepancies, and structural defects. The findings were compared against established human and veterinary literature regarding diaphragmatic hernias and associated syndromes.

Key Results
The dissection revealed a complex constellation of malformations:

• Diaphragmatic Defect: A Bochdalek-type hernia was identified at the posterior border of the left posterolateral diaphragm. The defect measured 20 mm anteroposteriorly and 39 mm horizontally. The esophageal hiatus was absent.
• Visceral Displacement: The stomach, spleen, cecum, and the distal 3/5 of the small intestine (ileum) were displaced into the thoracic cavity, located posterior to the heart and esophagus.
• Pulmonary Hypoplasia: Both lungs were severely underdeveloped, measuring approximately one-tenth of their normal size. The bronchi were malformed, though the trachea appeared normal.
• Renal and Urinary Anomalies: A horseshoe kidney (60 mm in length) was present in the pelvis, oriented diagonally with a common renal pelvis and a single dilated ureter connecting to the left side of the bladder. The renal veins drained into the internal iliac veins.
• Vascular and Skeletal Variations: The thoracic aorta ran to the right of the thoracic vertebrae. The inferior vena cava was positioned further to the left of the abdominal aorta. The fetal pig exhibited left-sided scoliosis.
• Genital Anomalies: The right testis and spermatic cord were absent, while the left testis and vas deferens were present.
• Other Observations: The liver was enlarged, but the gallbladder was normal. The vagus and phrenic nerves followed their typical courses relative to the esophagus and pericardium, respectively.

Key Contributions
This paper presents the first documented case of congenital diaphragmatic hernia in a fetal pig. It provides a detailed anatomical description of a Bochdalek hernia in a non-human mammal, a condition that is the most common form of CDH in humans but rarely reported in veterinary literature for fetal stages. The study contributes to the understanding of the incidence of CDH in animals, noting that while the sample size was limited (one case out of 1,040), the finding suggests the condition may be rarer in pigs than in humans, or at least underreported. Furthermore, the paper highlights the specific combination of CDH with horseshoe kidney, renal anomalies, and testicular agenesis, offering a comparative model for human syndromic presentations.

Significance and Claims
The authors assert that this case is significant because it mirrors the clinical presentation of Fryns syndrome in humans, a genetic disorder characterized by diaphragmatic defects, pulmonary hypoplasia, and multiple congenital anomalies (including renal and genital malformations). The study claims that the simultaneous occurrence of these specific malformations in a fetal pig is a rare event that corresponds to the complex phenotype seen in human Fryns syndrome.

Regarding prognosis, the paper maintains a modest and clinical perspective: while surgical repair of the diaphragm and repositioning of the herniated organs are theoretically possible postnatally, the authors conclude that survival is extremely unlikely due to the severity of the bilateral pulmonary hypoplasia. The study does not propose new therapeutic interventions or future experimental applications but rather serves as a descriptive case report to expand the limited literature on fetal animal diaphragmatic hernias and their association with multi-system malformations.