The Urachal Diverticulum As a cause of repeat bladder infections

The Urachal Diverticulum
As a cause of repeat bladder infections

By Dr. Ed Mapes
Stonebridge Animal Hospital

The urachus is tube-like structure that is only present in the fetus as it develops within the mother’s uterus. It is a tube that extends from the fetal urinary bladder and joins the umbilical cord, which attaches to the mother’s placenta. The fetal urine is excreted through the urachus, into the umbilicus, and is delivered into the mother’s blood stream from which it is subsequently eliminated. At the time of birth, the urachus should be closed and non-functional, leaving a smooth inner lining of the bladder.

Several outcomes are possible if the urachus fails to close off entirely. In rare cases, urine is found to leak from the newborn’s umbilicus, indicating the entire tube is still patent. More often, the urachal connection with the umbilicus is intrerrupted, but its opening into the bladder remains. This creates a blind sac, or diverticulum, within the bladder wall that can serve as a focal point for persistent bladder infections (cystitis).

Veterinarians keep this in mind when presented with a patient that fails to respond properly to treatment of cystitis, has repeated bouts of cystitis, or who is found to have bladder stones. Our last article discussed the fact that some types of such stones arise secondary to persistent bladder infection, so those patients are considered at risk of having a urachal diverticulum. Risks to the animal vary depending on the extent of abnormality, but all cases are potentially serious.

We confirm our suspicions of a diverticulum with X-rays of the bladder). In some cases, more advanced techniques such as the contrast or double contrast cystogram or intravenous pyelogram (IVP) are required to help make a diagnosis (Figures 1 and 2). Since abnormality within a bladder wall often fail to show up on plain radiographs, we introduce air (contrast cystogram) or air and a barium solution (double contrast cystogram) into the bladder that delineates the bladder wall and any abnormalities affecting it. These techniques are also utilized to diagnose some forms of bladder stones, wall masses, etc.

Figure 1: Plain radiograph

Figure 1: Plain radiograph

Figure 1 this plain radiograph of our patient ruled out the presence of most types of bladder stones, but did not explain the cat’s persistent bladder infections. We proceeded to the double contrast cystogram seem in Figure 2.

Figure 2: Double contrast cystogram

Figure 2: Double contrast cystogram

Figure 2 this double contrast cystogram was performed by inserting air and then a contrast dye into the bladder by way of a urinary catheter. The technique was used to identify an urachal diverticulum in the same patient as seen in Figure 1. Note how the bladder wall is outlined, and that the forward end of the bladder wall is thickened. We subsequently corrected the defect at surgery, and put an end this cat’s repeated bouts of painful cystitis.

The IVP is done by injecting a contrast agent into the blood stream. We than take x-rays as the solution enters the kidneys and rest of the urinary tract to outline anomalies.
Once the presence of urachal diverticulum is confirmed, we schedule surgery to resect the defect and eliminate the source of further infections. Sometimes we discover the diverticulum while performing surgery to remove bladder stones, and proceed to make the correction during the same procedure. During surgery, we often take a culture swab of the bladder lining, used to determine exactly what bacterial organisms are present and what antibiotics are most effective for treatment.

Any pet that fits the parameters, with stubborn bladder infections that repeatedly recur after treatment or have stones in the bladder, should be examined for this anomaly. Only surgical correction will bring about a resolution of the persistent problems.

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