• Cause: premature emergence from eggshell for yolk sac retention and exposure to bacteria and/or fungi, often from suboptimal conditions for infection to develop.
• Signs: exterior yolk sac observed. Homogenous in color and texture, and yellow if healthy neonate but prematurely emerged. If not homogenous and yellow this is an indication of infection. If there is a closed umbilicus but palpable firm swelling in the coelom, this is an indication of an infected yolk sac. Skin changes: discolored, roughened. Dehydration. General malaise, lethargy, anorexia.
• Diagnosis: based on observation and clinical signs. Visualization of yolk sac with a change in color and appearance if infected. Malodorous smell. Swabs for bacterial and fungal culture and sensitivity.
• Treatment: if healthy individual and normal appearance to yolk sac (bright yellow and homogenous), environmental management (place in dark container lined with damp paper towels). Surgical intervention in most cases if infected.
• Prognosis: good if premature and healthy individual. Favorable if omphalectomized with supportive care. Poor if coelomic swelling and closed umbilicus as many neonates are septic.

Presenting signs

• Observation of an exteriorized yolk sac:
  • Homogenous in color and texture, and yellow if healthy neonate but prematurely emerged.
  • If not homogenous and yellow this is an indication of infection.
• Palpable firm swelling in the coelom and a closed umbilicus. In a snake, coelomic mass palpable approximately 50-65% of its snout-vent length.
• Non-specific signs:
  • General malaise.
  • Lethargy.
  • Anorexia.
• Failure to complete the postnatal shed successfully (neonatal snake).
• Failure to eat within 30 days (neonatal snake).
• Behavior changes of the neonate, eg neonate seen within enclosure instead of hiding as a result of not being attended to by the parents; this can be seen in some viviparous lizards, such as prehensile-tailed skinks.

Acute presentation

• Exteriorized yolk sac.
• Moribund.

Age predisposition

• Neonatal, very recently emerged from egg (oviparous reptiles) or recently from birth (viviparous reptiles).

Gender predisposition

• No predilection.

Breed/Species predisposition

• No predilection.

Public health considerations

• Standard basic hygiene and PPE (gloves) when handling reptiles with exposed and infected yolk sacs.

Cost considerations

• Minimal costs if healthy individual with a normal appearance to yolk sac (bright yellow and homogenous), environmental management often successful.
• Substantial costs if infected; costs for stabilization, surgery, culture and sensitivity testing and post-operative management.

Special risks

• Anesthetic risks Anesthesia overview:
  • Neonate.
  • Often septic.
  • Other underlying factors, eg localized or systemic infection if neonate has swallowed or inhaled contaminated fluid when emerging from the egg.