Introduction: The biochemical consequence of acute obstructive uropathy can alter the hemodynamic profile. The objectives of this study were to determine the arterial blood pressure at presentation of male cats with acute urethral obstruction and to correlate these measurements with concurrent metabolic abnormalities.

Study Design: Prospective research study in a private small animal after-hours emergency clinic. The subjects were client owned male cats presented with acute urethral obstruction and no other known concurrent disease.

Measurements: Indirect oscillometric blood pressure measurements of urethral obstructed male cats were obtained at admission prior to blood sampling and treatment. Data recorded and studied: mean arterial blood pressure (MAP), physical examination parameters, serum blood urea nitrogen (BUN), creatinine, potassium, phosphorus, total calcium and magnesium concentration, venous pH, electrocardiogram lead II, and urine volume in bladder.

Results: Twenty-eight cats were included in the study. Using normal values for MAP in cats, the results fell into 2 groups: normotensive (MAP 90–140 mmHg) and hypertensive (MAP>140 mmHg). Seventy-one percent (20/28) were considered normotensive (mean 113±14.6 mmHg). Twenty-nine percent (8/28) were considered hypertensive (mean 154±9.8 mmHg). In the normotensive group, the mean body temperature was 37.6±1.5°C, the mean heart rate was 179±42.2/min, and 64% (9/20) had an abnormal cardiac rhythm. In the hypertensive group, the mean body temperature was 38.3±0.6°C, the mean heart rate was 219±18.0/min, and all had normal cardiac rhythm. In the normotensive group, the serum biochemical abnormalities were more severe. Sixty percent of the normotensive casts (12/20) were azotemic (BUN>34 mg/dl) with a mean of 114±95.2; 58% (11/19) were hypercreatinemic (>2.2 mg/dl) with a mean of 8.9±7.9, and 55% (11/20) were hyperkalemic (>4.2 mEq/L) (mean 6.2±7.9). Within the hypertensive cats group, 50% (4/8) were mildly azotemic (BUN – mean 49±24.4 mg/dl); 50% (4/8) were hypercreatinemic (mean 2.9±1.95 mg/dl), and only 1/8 was hyperkalemic (mean 3.9±0.6 mEq/L). The volume of urine in the bladder at the time of presentation did not seem to be significantly different between the 2 groups (94.7±57.1 ml in the normotensive group vs. 83.8±26.7 ml in the hypertensive group).

Conclusions: The results suggest that cats with acute urethral obstruction and a normal mean arterial pressure at presentation were more likely to have severe azotemia, hypercreatinemia and hyperkalemia.