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Many injuries and abnormalities of the urinary tract are not readily apparent on initial triage and physical examination. Historical information from the pet owner regarding changes in water consumption, urine production, stranguria, pigmenturia, and recent trauma can raise suspicion for urinary tract dysfunction, however, some patients have vague and non‐specific historical signs. For example, many male cats with urethral obstruction present for lethargy and/or constipation, as many owners are unable to differentiate stranguria from tenesmus.

After respiratory, cardiovascular, and neurologic assessments have been performed and treatment of urgent abnormalities initiated, assessment of the urinary tract can be performed. Palpation for a urinary bladder should be performed in all patients to assess for urethral obstruction, which causes a large, firm, painful, bladder that is unable to be expressed. Palpation of a bladder in trauma patients does not rule out injury and leakage, as small tears may not completely decompress the bladder. Additionally, lack of a palpable bladder is not always synonymous with rupture, as the bladder may not be palpable due to small size from dehydration, recent expression, or anuric or oliguric renal failure. Ultrasound is a useful tool in the emergency room, especially for urinary tract assessment. A standardized technique for abdominal ultrasonographic assessment in veterinary trauma patients has been created and validated. In human medicine, a similar technique has largely replaced the need for diagnostic peritoneal lavage in blunt abdominal trauma patients. Focused assessment sonography for trauma (FAST) has been validated to determine whether free fluid is present in the abdominal cavity after trauma [83]. It is a more sensitive diagnostic for free fluid than the presence of a palpable fluid wave, which requires at least 40 ml/kg of fluid within the peritoneal cavity. Using ultrasound in transverse and longitudinal planes, and the patient in lateral recumbency, the abdomen is evaluated at the gravity dependent and independent flanks (in the region of the kidneys), over the bladder, and below the xiphoid. If needed, ultrasound guidance or blind abdominocentesis via a one‐ or four‐quadrant closed needle/syringe technique can be used to collect any free fluid. In many patients with significant dehydration, free fluid may not be present in the peritoneum initially, and serial monitoring as the patient is rehydrated should be performed. Once fluid is obtained, PCV/TS, glucose, lactate, creatinine, potassium, cytology, and culture can help determine the etiology of the effusion. In dogs, a fluid to blood creatinine ratio of greater than 2 : 1, and fluid to blood potassium ratio of greater than 1.4 : 1 is supportive of a diagnosis of uroabdomen [84]. In cats, a fluid to blood creatinine ratio of 2 : 1 and fluid to blood potassium ratio of 1.9 : 1 is supportive of a diagnosis of uroperitoneum [85, 86].

Initial bloodwork may reveal azotemia, which could be due to prerenal, renal, or post‐renal causes. Assessment of urine specific gravity in conjunction with azotemia and PCV/TS can help to determine the etiology, but it may not be feasible or safe to obtain a urine sample during triage and before initiation of fluid therapy. This is especially true of female dogs and cats, and male cats where sedation for catheter placement is often necessary. Cystocentesis may be contraindicated in patients where there is any concern for coagulopathy, thrombocytopenia, or thrombopathia. An assessment of prerenal azotemia is therefore often made on physical examination findings and evidence of hemoconcentation without concurrent urine specific gravity. In these cases, improvement or resolution of azotemia in response to fluid therapy and rehydration helps to support the diagnosis of prerenal azotemia. For stabilization of the uremic patient, please refer to Chapter 22.

Urine drainage techniques can be useful for exact urine production quantification and management of urine leakage. Urinary catheterization can be very helpful in patients with urinary trauma to document appropriate urine production, maintain bladder decompression in patients for whom concern over bladder or urethral trauma exists, and for patient comfort and ease of management in non‐ambulatory patients. However, this use is controversial owing to the risk of ascending urinary tract infections, particularly in a hospital setting. Urinary catheterization is easy to perform in most male dogs without sedation, but placement in female dogs and male and female cats requires heavy sedation and can be more technically challenging, especially in small female dogs (Figure 1.6). Urinary drainage with locking loop or “pigtail” catheters in the peritoneum can be helpful to facilitate urine drainage and permit patient stabilization in preparation for surgical intervention when a uroabdomen is present (Figure 1.7a,b). The same catheters can be used in the bladder for decompression when transurethral catheterization is not possible, and in the renal pelvis as a nephrostomy tube when there is a ureteral obstruction or ureteral injury [86, 87].

Figure 1.6 Cadaveric dissection of the urethral papilla in a female dog, which is the major landmark used when performing urinary catheterization.

Figure 1.7 Distal end of a locking loop, or pigtail, catheter. The catheter coil is straightened over a stylet and trocar for placement (a), and then locked into the loop configuration using the suture upon removal of the stylet and trocar (b).