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The lower urinary tract

"The lower urinary tract is formed by two anatomical structures: the bladder and the urethra. The urethra is a tube that connects the bladder to the urethral orifice. The urethral orifice is the external opening of the urethra from which urine exits the body during normal urination.

Common pathologies of the lower urinary tract include inflammations and occlusions.

Clinical Signs:

Clinical signs of patients affected by lower urinary tract inflammation or occlusions are:

- Pollakiuria: frequent urination; dripping of urine from the penis (‘overflow’).

- Hematuria: presence of blood within the urine.

- Dysuria: difficulty urinating.

Behavioral changes may also be noted: spending a long time in a squat position in the litter tray, urinating in unusual places, or overgrooming the genital area.

A strong odor of urine may also be present.

Common causes:

Common causes of lower urinary tract inflammation or occlusion include:

- Bacterial infections, which are more common in dogs than in cats.

- Urinary stones, crystals, or very small stones. These cause irritation/inflammation or, in some cases, blockage of the

urethra (‘blocked bladder’).

- Neoplasia: bladder tumors.

- Urethral strictures.

In the case of complete urethral occlusion, emergency treatment of the patient would be required to unblock the urethra and restore electrolyte balance."


Urethrostomy is the creation of a permanent opening into the urethra. The indications for urethrostomy are recurrent or persistent urethral obstruction, irreversible urethral trauma (stricture), or severe penile trauma.

In male dogs, urethrostomy is performed just behind the penis because of the relatively superficial position of the urethra. The surgery should be performed in a neutered patient and will not require penis amputation.

In cats, penis amputation would be required, and urethrostomy would be performed a few centimeter behind the anus.

Early postoperative complications include swelling and haemorrhage. Swelling resolves within a few days, while haemorrhage (especially associated with urination) resolves in 5-7 days; however, blood within the urine may be present for a few weeks.

Stricture secondary to scar tissue formation could occur; these will need a review surgery.

Long-term complications could include recurrent urinary tract infection due to migration of bacteria into the bladder because of a short urethra (in 30% of cases).

Overall, the outcome of the surgery is good, with owners reporting positive long-term results in the majority of cases (90%)."

These changes mainly involve adding punctuation where needed, ensuring consistency in terminology, and clarifying some expressions for smoother readability.

Subcutaneous Urethral Bypass System (SUB)

The ureters are two very fine tubes carrying the urine produced by the kidneys to the bladder.

Ureteral obstructions due to calculi (stones) are the most commonly diagnosed condition; however, obstructions secondary to neoplastic lesions, strictures, or blood clots are also possible.

Photos: the yellow circles mark both left and right kidney , red and purple circles are marking kidney, bladder and urethral stones.

About the SUB

A SUB is a device designed to bypass the obstruction, allowing the flow of urine from the kidney to the bladder through a tube system. The system consists of one or two pigtail catheters placed in the kidneys, one catheter placed in the bladder and secured with sutures, a subcutaneous port used to collect urine or flush the system, and a "y" or "X" connector junction linking all the catheters to the port.

SUB Kit, Surgical Benefits, and Postoperative X- ray

Ureterostomy and Ureterotomy were the surgical techniques used in the past; these involved surgical interventions straight on the ureter to remove the cause of obstruction. Traditional surgeries were associated with a high complication rate between 22% to 31% due to urine leakage and strictures of the ureters (scar formation), especially in cats where the ureters measure 1 mm in diameter.

The advantage of the SUB is to reduce post-operative complications, bringing the death rates around 5%, with a life expectancy between 2 and 5 years. A significant association between long survival time and the grade of kidney failure is reported in scientific studies. Cats affected by severe kidney failure (very high creatinine levels) have a shorter survival time in comparison with those with moderate kidney injury.

Surgical Risks

The most common complications are infections (14%) and blocked catheters due to blood clots or kinking (5%). Whereas infection is a major complication and could be difficult to control, blocked catheters may require a review surgery, replacing only one part of the SUB.

Catheter Maintenance

Flushing of the catheter through the subcutaneous port will be required a month after the surgery and every 3-6 months for life. The procedure is minimally invasive and well-tolerated by the patients; however, some patients may be sedated depending on their behaviour.

Clinical Case The SUB was placed to treat bilateral ureteral blockage in a cat. Intra-operative "X" connector and Subcutaneous Port Intra-operative placement of the catheter in the bladder Intra-operative placement of the catheter in the kidney Postoperative XR of the SUB

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