Uroperitoneum in Foals: Signs of a Ruptured Urinary Tract

Uroperitoneum means urine is leaking into the abdominal cavity instead of staying inside the urinary tract. In foals, this most often happens when the bladder tears around birth or when the urachus, the fetal tube that connects the bladder to the umbilicus before birth, ruptures or fails after infection. Male foals appear to be affected more often than females.

A foal with uroperitoneum may seem normal right after delivery. Over the next 1-2 days, urine builds up in the abdomen and the foal gradually becomes dull, weak, and less interested in nursing. As the abdomen fills, breathing can become harder and the foal may strain to urinate but pass very little.

This condition is dangerous because the problem is not only the leak itself. Urine sitting in the abdomen allows electrolytes and waste products to move back into the bloodstream. That can lead to low sodium and chloride, azotemia, and especially high potassium, which can interfere with normal heart function. Early recognition and rapid veterinary care make a major difference.

The most common cause is rupture of the urinary bladder, often thought to be related to pressure or trauma around foaling. A full fetal bladder may be compressed during passage through the birth canal, and the dorsal bladder wall is a common site of tearing. Male foals are reported more often, possibly because of differences in urinary outflow anatomy.

Another cause is rupture or disease of the urachus. The urachus should close after birth. If it stays open, becomes infected, or weakens, urine may leak from the umbilical region or into the abdomen. Less commonly, defects involving the ureters or congenital urinary tract abnormalities can lead to urine leakage.

Not every foal shows the same pattern. Some have a dramatic swollen abdomen, while others mainly show weakness, poor nursing, and repeated straining. Sepsis, prematurity, and concurrent illness can complicate the picture and may make diagnosis less straightforward.

Your vet will start with a physical exam and a careful history, including when the foal last nursed, whether urination has been seen, and how quickly the abdomen enlarged. Bloodwork is important because many foals develop metabolic changes such as hyponatremia, hypochloremia, azotemia, and hyperkalemia. Those changes help guide stabilization and anesthesia planning.

Abdominal ultrasound is commonly used to confirm free fluid in the abdomen and may help identify a bladder or urachal lesion. Your vet may also collect abdominal fluid with abdominocentesis. Comparing abdominal fluid creatinine to blood creatinine is a practical and widely used way to confirm that the fluid is urine.

Additional tests may include urinary catheterization, contrast imaging, or umbilical ultrasound when a urachal problem is suspected. Because uroperitoneum can resemble sepsis, meconium impaction, colic, or neurologic disease, diagnosis often depends on putting the exam, imaging, and lab results together rather than relying on one finding alone.

Not every case can be prevented, because some bladder tears happen around the time of birth despite good management. Still, close observation during the first 24-48 hours after foaling helps catch problems early. Make sure the foal is nursing, passing urine normally, and not developing a steadily enlarging abdomen.

Good foaling supervision matters. Difficult deliveries should be handled promptly and carefully with your vet's guidance, because excessive traction and birth trauma may increase the risk of urinary tract injury. Umbilical care is also important, since urachal infection can contribute to leakage problems.

Call your vet early if you notice urine dripping from the umbilicus, repeated straining, poor nursing, weakness, or a pot-bellied appearance. Early evaluation does not always prevent the condition, but it can prevent dangerous delays in treatment and improve the foal's chances of recovery.