Elevated Blood Urea Nitrogen: An Aid to the Diagnosis of Intraperitoneal Rupture of the Bladder

Abstract

A retrospective analysis was done on 18 patients with bladder rupture. At the time of hospitalization 9 patients with extraperitoneal rupture had an average blood urea N of 14.2 .+-. 2.2 mg% which did not vary from the normal laboratory value of 14.5 .+-. 7.4 mg%; 9 patients with intraperitoneal rupture had an average blood urea N of 29.9 .+-. 7.6 mg% which was significantly different (P < 0.0001) from the discharge blood urea N (12.9 .+-. 2.2 mg%) and the normal laboratory value. The 2 groups of patients were comparable since no significant difference was found in age, sex, mode of injury, hematocrit value or associated injuries. To quantify the significance of this observation an experimental study was done on dogs with surgically created intraperitoneal bladder ruptures, i.p. injections of urine, i.p. injections of blood and a control group. A sequential increase in serum blood urea N was found in dogs with intraperitoneal bladder rupture 1 h after injury to an empty bladder. An i.p. injection of urine showed that a high blood urea N could be found as early as 1/2 h after the injection and that it would be cleared totally in 3-6 h. Serum creatinine levels were not good indicators of intraperitoneal urine, becoming significantly different from control values later than the blood urea N. All creatinine levels were within the normal human laboratory value suggesting a poor and sluggish index of this type of injury. Increased blood urea N is a presenting laboratory finding and a sensitive index in the detection of patients who have sustained intraperitoneal rupture of the bladder. Awareness of this finding may lead to an early diagnosis in otherwise clinically unsuspected cases. This test will not provide for a diagnosis of extraperitoneal bladder ruptures.