{"id":22941,"date":"2021-02-15T20:06:55","date_gmt":"2021-02-15T20:06:55","guid":{"rendered":"https:\/\/todaysveterinarypractice.com\/?p=22941"},"modified":"2022-03-30T20:52:31","modified_gmt":"2022-03-30T20:52:31","slug":"managing-urolithiasis-in-dogs","status":"publish","type":"post","link":"https:\/\/navc.sitepreview.app\/todaysveterinarypractice.com\/urology-renal-medicine\/managing-urolithiasis-in-dogs\/","title":{"rendered":"Managing Urolithiasis in Dogs"},"content":{"rendered":"

Urolithiasis<\/i> is a general term referring to the presence of a stone anywhere in the urinary tract. It can be modified to indicate the location of the stone: nephrolith <\/i>= kidney stone, ureterolith <\/i>= stone within ureter, cystolith<\/i> or cystic calculus <\/i>= bladder stone, urethrolith <\/i>= stone within urethra. Urolithiasis is a syndrome with multiple underlying etiologies.\u00a0<\/span><\/span><\/p>\n

Pathogenesis of Stone Formation<\/h2>\n

The initial step in stone formation is the precipitation of microcrystals in urine, which contains various salts, minerals, and other solutes. Normally, inhibitory mechanisms help prevent crystals, including undersaturation of solutes, inhibitory substances within urine, and lack of scaffolding matrix for precipitation.<\/span><\/p>\n

Once microcrystals form, they can link together and increase in size to form macrocrystals and, eventually, a stone.1<\/sup> Foreign material can serve as an excellent scaffold for crystal precipitation and subsequent stone formation. Absorbable suture (typically placed in the bladder wall following cystotomy) has been documented to play a causative role in the pathogenesis of some cystic calculi.2<\/sup> Similarly, once a stone is formed it can become a scaffold for deposition of a different type of crystal. This typically results in a compound stone, in which the shell is made of a different substance than the nidus (<\/span>FIGURE 1<\/span><\/strong>).<\/span><\/p>\n

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Figure 1. An example of a compound urolith. The calcium oxalate (CaOx) nidus serves as a scaffold for a bacterial urinary tract infection, leading to the deposition of struvite. The shell is also made of CaOx.<\/p><\/div>\n

History and Clinical Signs of Urolithiasis<\/h2>\n

Clinical signs of cystic calculi may include hematuria, pollakiuria, stranguria, and dysuria, but these signs are also common with other diseases of the lower urinary tract. Small uroliths can cause partial or complete urinary obstruction of the urethra, leading to bladder distention, abdominal pain, paradoxical incontinence, stranguria, and signs of postrenal azotemia. Rarely, the bladder ruptures, resulting in uroabdomen.<\/span><\/p>\n

Clinical signs of upper urolithiasis are different; they may be intermittent, or the patient may be asymptomatic. Microscopic or macroscopic hematuria may be present. Signs associated with ureteral calculi are usually caused by renal dysfunction from concurrent pyelonephritis or obstructive uropathy (postrenal azotemia). Abdominal pain may be present but does not seem to be common.3<\/sup><\/span><\/p>\n

Cystic calculi may be palpated during physical examination in some small patients. Rectal examination may allow for identification of uroliths within the bladder or pelvic urethra. Renomegaly or renal pain may be present with ureteral obstruction.<\/span><\/p>\n

Diagnostic Tests<\/h2>\n

The minimum database for patients presenting with lower urinary tract signs includes a complete blood count, serum biochemistry panel, urinalysis with culture, and diagnostic imaging. The major differentials for a dog with stranguria and pollakiuria are bacterial cystitis, urolithiasis, and neoplasia.\u00a0<\/span><\/span><\/p>\n

Urinalysis may allow for identification of crystals and infection as well as documentation of the pH and urine specific gravity (USG). Urine should be analyzed within 1 hour of collection to minimize temperature- and time-dependent changes in sediment. Refrigeration and prolonged storage time both may cause crystal precipitation that would not be observed in fresh, room-temperature urine.4<\/sup> However, even in fresh urine, crystalluria is clinically insignificant (<\/span>BOX 1<\/span><\/strong>).\u00a0<\/span><\/span><\/p>\n

BOX 1 Crystalluria Is Not a Disease<\/div>
Crystalluria is not a disease and does not necessarily indicate the animal is at risk for urolithiasis. Treatment is not required unless a urolith or urethral plug is present or has previously formed. Some crystal types, such as cystine, xanthine, and urate, may suggest metabolic abnormalities and warrant further investigation even in the absence of uroliths. Struvite crystals may suggest the presence of urinary tract infection if bacteriuria and pyuria are concurrently observed.<\/p>\n

Key Points<\/strong> <\/span><\/span><\/p>\n