In the dam’s womb the foal has a unique way to urinate. Urine from the fetal bladder flows through the urachus—a channel that forms part of the umbilicus—and fills the placenta’s allantoic cavity. This highly specialized system works well in utero but, once on the ground, the newborn foal is no longer dependent on the mare’s blood supply for waste product disposal and instead begins to urinate through the urethra. At this time the umbilical vein atrophies and becomes the foal’s falciform ligament. Both umbilical arteries undergo a similar transformation, turning into the round ligaments of the bladder. The urachus becomes a dried stump within 24 hours of birth and falls off completely by the second week of life when all goes according to plan. “With the umbilicus, since we’re dealing with internal structures that are being exposed to the outside world at parturition (birth), there’s the potential for infection,” said Laura Javsicas, VMD, Dipl. ACVIM, an internal medicine specialist at Rhinebeck Equine in Rhinebeck, New York , during Cavalcade Education’s 2022 reproduction symposium, in Hyde Park, New York. The common practice of dipping the neonate’s umbilicus in antiseptic solution such as dilute chlorhexidine (Javsicas’ first choice) or dilute betadine (her second choice) for the first few days of life helps combat this risk of infection and allows the umbilicus to dry up. “Aside from the physical exam, our best diagnostic tool for these cases is ultrasonography,” Javsicas said. She uses her ultrasound probe to examine the area surrounding the umbilical stump, measuring the remnants of the umbilical vein and arteries. She also notes the presence of hypo- or hyperechoic fluid or gas bubbles, the latter being suggestive of anaerobic infection. Enlarged umbilical remnants, speckly fluid, edema, cellulitis, and mucopurulent exudate are all signs of infection. The decision to treat an infected umbilicus medically versus surgically is at the practitioner’s discretion and varies by case. The medical approach involves administering broad-spectrum antibiotics, ideally guided by a culture. “Without a culture, I generally prescribe a course of EquisuIl (the FDA-approved liquid form of sulfadiazine and trimethoprim) combined with rifampin,” said Javsicas. “Another antibiotic option is chloramphenicol, which also has good penetration for the hard-to-reach umbilical structures.” As for surgical treatment, the appropriate procedure depends on the infected structures. The three main options include: Omphalectomy: excision (removal) of the umbilical stump. Umbilical remnant resection: removal of infected internal structures, as determined by ultrasound. Marsupialization of the umbilical vein: rerouting the base of the infected vein from the liver to the outside of the abdominal cavity to allow it to drain. The surgeon then removes the remainder of the umbilical vein. “We don’t tie off these vessels internally because that could lead to the development of an internal abscess in the liver, where the vein ends,” Javsicas said. ­­Aside from infections, foals can also suffer from a patent urachus. “If you notice urine coming out of your foal’s urethra and from their umbilicus, call your vet,” she said. “The urachus is still open when it shouldn’t be.” To cauterize the umbilicus, some caretakers use silver nitrate sticks. Javsicas advised against this practice because the chemical compound greatly irritates tissues, predisposing them to infection. Instead, she recommends continuing to dip the umbilicus in antiseptic solution and generally prescribes a course of the antibiotics procaine penicillin G (PPG) or ceftiofur (Excede).