{"id":1060,"date":"2016-05-03T12:52:53","date_gmt":"2016-05-03T16:52:53","guid":{"rendered":"http:\/\/phosdev.com\/todaysveterinarynurse\/?post_type=articles&p=1060"},"modified":"2022-05-03T18:46:04","modified_gmt":"2022-05-03T18:46:04","slug":"urethral-obstruction-in-male-cats","status":"publish","type":"post","link":"https:\/\/navc.sitepreview.app\/todaysveterinarynurse.com\/urologyrenal-medicine\/urethral-obstruction-in-male-cats\/","title":{"rendered":"Urethral Obstruction in Male Cats"},"content":{"rendered":"

Urethral obstruction is a potentially life-threatening emergency. Male cats are more prone to obstruction than female cats.1<\/sup> When the urethra becomes partially or completely blocked, urine is unable to drain from the bladder, resulting in fluid, electrolyte, and acid\u2013base abnormalities.2<\/sup> Feline urethral obstruction is a relatively common condition, accounting for up to 10% of feline cases presented to small animal referral and emergency clinics.3,4<\/sup><\/p>\n

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Editor\u2019s Note:<\/strong> This article was originally published in May 2016. Please use this content for reference or educational purposes, but note that it is not being actively vetted after publication. For the most recent peer-reviewed content, see our issue archive<\/a><\/strong>.<\/p>\n

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Etiology<\/h2>\n

The urethra\u2014the tubular passage through which urine is discharged from the bladder to outside the body\u2014can become obstructed for several reasons. The urethra is longer and narrower in male cats than in female cats; therefore, male cats are more likely to develop an obstruction. The most common cause of obstruction is a urethral plug, which consists of mineral crystals (e.g., struvite, calcium oxalate), white blood cells, red blood cells, protein (mucus), and epithelial cells.5<\/sup> The underlying cause of urethral plugs is unknown; however, plugs have been linked to struvite crystalluria \u2014 suggesting that diet may play a role \u2014 and idiopathic cystitis.6<\/sup> Other causes of urethral obstruction include urethral edema and spasm associated with lower urinary tract inflammation and pain.7<\/sup> Uroliths, neoplasms, and urethral strictures can also lead to urethral obstruction; however, they are reported less frequently than other causes.5<\/sup><\/p>\n

History and Clinical Signs<\/h2>\n

Cats with a history of lower urinary tract disease\u2014particularly interstitial cystitis\u2014are at an increased risk for developing urethral obstruction.8<\/sup> Some patients may have a history of obstruction.9<\/sup> Clinical signs of urethral obstruction can vary depending on the severity and duration of the obstruction. Initially, the most common clinical sign is stranguria, which is sometimes mistaken by the owner as constipation.8<\/sup> Affected cats may urinate frequently, strain to urinate, urinate inappropriately, and pass small volumes of blood-stained urine (hematuria).10<\/sup> Lethargy, anorexia, vomiting, and other signs of systemic illness are also common.1<\/sup> Signs of discomfort or pain caused by an inflamed urethra and increased bladder size include vocalization, inappetence, and hiding. Affected cats can be observed frequently licking their genital region.10<\/sup> Vomiting and lethargy may also be noted.1<\/sup> In addition, the patient\u2019s mucous membranes will be pale, and capillary refill time is prolonged.4<\/sup><\/p>\n

On abdominal palpation, the urinary bladder is often large and firm and cannot be expressed easily. Caution should be used when attempting to express a possibly obstructed bladder. If too much pressure is applied to the distended bladder, it can rupture. If bladder rupture is suspected, the goal is to immediately stabilize the patient so that the clinician can perform emergency surgery. If the urethral obstruction goes untreated for more than 24 to 48 hours, the resulting uremia can lead to hypothermia, bradycardia, tachypnea, altered levels of consciousness (including coma), and death.4<\/sup><\/p>\n

Diagnosis<\/h2>\n

A common finding associated with urethral obstruction is a large, firm bladder on abdominal palpation. Urine should be collected for urinalysis, culture, and sensitivity testing.10<\/sup> Blood work (i.e., complete blood count and serum chemistry profile, including serum potassium levels) should also be obtained. Serum potassium levels can be used to assess cardiotoxicity associated with hyperkalemia.10<\/sup> An electrocardiogram (ECG) should be obtained to evaluate cardiac function and identify abnormalities consistent with hyperkalemia. Signs of hyperkalemia include diminished to absent P waves, widened QRS complexes, prolonged PR intervals, and tall, \u201ctented\u201d T waves.11<\/sup> These abnormalities, which most often appear on lead II tracings when serum potassium concentration is >7 mEq\/L, are the result of a raised (more positive) resting membrane potential that slows depolarization and exaggerates repolarization.12<\/sup><\/p>\n

Abdominal radiographs can help determine the presence of cystic or urethral calculi. Identification of calculi (stones) affects how an obstruction is treated. The presence of calculi can make it much more difficult to use a urinary catheter to remove the obstruction and can result in additional urethral trauma. If bladder stones are present, a cystotomy should be performed after the urethral obstruction has been removed and the patient is stable enough to undergo anesthesia. Voiding urohydropulsion is another method that can be used to remove bladder stones.13<\/sup><\/p>\n

Treatment<\/h2>\n

Address Metabolic Abnormalities<\/h3>\n

When treating a cat with a urethral obstruction, it is important to quickly stabilize the patient\u2019s vital signs and address metabolic abnormalities so that urethral catheterization can be performed to remove the obstruction. Administering IV fluids is the initial step in therapeutic management. Traditionally, 0.9% NaCl has been the fluid of choice because it does not contain potassium and has the greatest dilutional effect on hyperkalemia; however, a balanced electrolyte solution, such as Normosol-R, Plasmalyte 148, or lactated Ringer\u2019s solution, can be administered as an alternative. Although these solutions contain some potassium, the concentrations are 5 mEq\/L or less,14<\/sup> which may also make the solutions effective in treating concurrent metabolic acidosis. Fluid rate and quantity should be determined based on the patient\u2019s clinical signs and physical examination findings. Aggressive fluid therapy is indicated in patients that are markedly depressed or unresponsive. A shock dose of 60 mL\/kg should be administered to these patients and titrated to effect.15<\/sup> Hydration and cardiovascular status must be reevaluated after each bolus is administered. In patients with stable vital signs, the percentage of dehydration should be used to calculate the fluid rate and quantity required to correct hydration status (BOX 1)<\/strong>.<\/p>\n

BOX 1<\/strong> How to Calculate Replacement Fluids<\/div>
Dehydration + Maintenance + Ongoing losses = Amount of replacement fluids needed<\/strong><\/p>\n

Example: For a 5 kg cat that is 5% dehydrated:<\/p>\n