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Urolithiasis In Pets

overview

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Urolithiasis refers to stones in the urinary tract. These are usually in the bladder and/or kidneys, but can become lodged in the ureters (the thin tubes connecting the kidneys and bladder) or the urethra (the tube between the bladder and the outside world). Many different factors contribute to the development of stones, and include genetic predisposition (often breed related), age, gender, diet, environment and acquired disease (such as urinary tract infection). Several different types of urinary stone exist, consisting of different mineral compounds.

symptoms

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What are the symptoms of Urolithiasis?

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Symptoms of urolithiasis are not specific. Bladder stones cause symptoms very similar to other causes of bladder inflammation (cystitis), such as straining to urinate, frequent urination, painful urination, and blood in the urine. Cystitis due to stones may improve with medication, but will rapidly recur when treatment stops. Stones in the kidneys can be painful, and may cause signs related to reduced kidney function, such as inappetance, lethargy, increased thirst and vomiting. Kidney stones can also occur without symptoms.

diagnosis

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Which tests are used to diagnosis Urolithiasis?

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Imaging must be performed to diagnose urolithiasis. Most stones are visible on ultrasound, however, it is very challenging to visualise the ureters and urethra. X-rays are very good for imaging the entire urinary tract, however not all types of stone show up on x-ray. Often, both ultrasound and x-ray are advised in combination.

It is not possible to know exactly what composition uroliths are without testing a stone directly. Several clues can help us narrow down the possibilities, including visibility on x-ray and the acidity of the urine. Due to the increased incidence of bladder stones with urinary tract infection, urine is often cultured for bacterial growth if uroliths are diagnosed.

treatment

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How is Urolithiasis treated?

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Treatment options vary depending on the type and location of stones. Broadly speaking, we can treat urolithiasis medically or surgically. Stones which are located in the ureter or urethra, causing an obstruction, are not suitable for medical management.

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Medical treatment

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Medical treatment aims to dissolve the urinary stones, achieved by feeding a prescription urinary diet. It typically takes 3-6 weeks for stones to dissolve, depending on their size and location. Imaging and urinalysis are usually repeated during the dissolution process to monitor progress. Some stone types do not dissolve; the type most commonly suited to medical dissolution are called struvite.

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Surgical treatment

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For stones that will not dissolve, or that are causing significant secondary problems such as cystitis or obstruction, surgical removal is necessary. Most commonly, this involves removing stones from the bladder, known as a cystotomy. Occasionally, surgery is performed to remove stones obstructing the ureters, or urethra, though this can be challenging and specialist referral may be required. Sometimes, surgical removal of stones is required to determine their composition and guide treatment. The stone type most commonly requiring surgical management are called calcium oxalate.

For both medically and surgically managed urolithiasis, long-term treatment is required to try and prevent recurrence. This most commonly consists of a prescription diet. Depending on the type of stone present and any predisposing factors, treatment may also include antibiotics, oral supplements to alter urine acidity and specific medication, if there is a genetic cause for the uroliths. Rarely, stones can form due to an underlying condition, so blood tests or other investigations may be recommended.

outlook

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What is the outlook for pets with Urolithiasis?

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The prognosis for dogs and cats with urolithiasis is generally very good, and the vast majority can be successfully managed. Patients presenting with ureteral or urethral obstruction can require significantly more intensive treatment, but carry a good prognosis if treatment is successful.

All animals who have had urolithiasis will require regular monitoring of their urine. Periodic imaging may be advised as patients are predisposed to recurrence of uroliths in future. Repeat episodes will need prompt treatment, however, previous urolithiasis does not alter the prognosis for recovery.