It’s nearly foaling season on the farm where I work, and a groom was telling me about a foal last year that died of bladder rupture on this farm. Is this something that I can prevent? How do I recognize it?

Bladder rupture is a tear or leak in the urinary bladder that results in uroperitoneum. Uroperitoneum, the accumulation of urine in the peritoneal (abdominal) cavity, also can result from disruption of other parts of the urinary tract. It is difficult to predict when bladder ruptures might occur; thus, it is difficult to prevent. Although bladder ruptures can occur in adult horses, usually from urinary tract obstruction, the vast majority of bladder ruptures occurs in foals. The rupture in foals usually occurs in the bladder itself, but also can occur in the urachus. The urachus, a structure in the fetus which lies between the tip of the bladder and the umbilical cord, allows the excretion of urine. This structure normally is closed at birth, and over several weeks contracts to a thick band of tissue.

Most bladder ruptures in foals occur during parturition. It is thought that the increased abdominal pressure the foal experiences during birth can lead to rupture of a full bladder if urine cannot be easily voided. The anatomy of the male pelvis and the longer length of the male urethra tend to predispose the male foal to this problem more often than the female.

Clinical signs seen in foals with bladders that rupture during parturition appear within the first two or three days of birth. The foal might become dull and depressed. There can be abdominal distension. Sometimes the foal will be colicky. Even though most of the urine is entering the abdominal cavity rather than exiting through the urethra, the foal often will dribble urine because the urethra is patent (not closed). You don’t usually see a steady stream of urine from these foals.

Uroperitoneum can also develop in neonates with debilitating problems or systemic infection. Leaking of urine into the abdomen might occur through tears in the bladder or the urachus. These foals did not rupture the bladder at birth. Infection might not primarily involve the urachal area, but can adversely affect it. Consequently, the tissue in the area becomes swollen and inflamed, loses integrity, then starts separating and leaking. This probably accounts for about 30% to 40% of our uroperitoneum cases. The clinical signs seen in these foals are similar to those mentioned earlier, except these foals have some other disease process present. Most of these clinical signs will occur somewhere between four and 12 days of age.

The diagnosis of uroperitoneum, regardless of the cause, can be made on the basis of the physical examination and lab values. Analysis of serum electrolytes in these foals generally shows a lower sodium and chloride value than normal and a higher potassium value. We also usually find elevated serum creatinine levels. These abnormalities result from the concentration of these substances found in the urine of a foal, the amount of urine that accumulates in the abdomen, and the ability or inability of the abdomen to reabsorb these substances. If the ratio of the creatinine in the peritoneal fluid to the creatinine in the serum is 2:1 or higher, you can almost count on a tear’s being present. An ultrasound exam will show a significant amount of fluid in the abdomen, and occasionally the origin of the leak.

The vast majority of these cases will require surgery. We enter the abdomen, locate the tear, and suture it closed. If the tear is in the urachus, the urachus is removed. There have been a few reports of leaks in the urinary system where the foal survived without surgery. A catheter was passed into the bladder through the urethra, draining the urine and decompressing the bladder. The edges of the tissue that were torn re-apposed and healed themselves, since the bladder was no longer distended. However, the surest way to solve the problem is surgically.

We try to perform the surgery as quickly after diagnosis as we can, but we are careful about the electrolyte abnormalities. High levels of serum potassium can affect the heart adversely, especially under anesthesia. In fact, some foals die before surgery can be performed, probably from cardiac arrest partially due to elevated potassium levels. To alleviate that risk, we partially drain the abdomen and administer intravenous fluids that do not contain potassium.

In general, the prognosis is favorable; about 80-90% of primary bladder rupture patients survive. Foals which are sick for other reasons that develop uroperitoneum have a guarded to fair prognosis, i.e., about 50% survive. Some of those foals are in marginal condition, and they don’t make it because of the combination of events.

Post-operative treatment consists of antibiotics and anti-inflammatories for at least a few days, plus whatever is needed for the foals which have other problems going on.

Bladder rupture is not a common problem, occuring in much less than 1% of the foal population. For the neonates where uroperitoneum develops after birth, the incidence is probably higher than that, but not by much.

Contributed By: Rolf Embertson, DVM, Dipl. ACVS (AAEP)