Diagnosis of intraperitoneal extravasation of urine by peritoneal lavage

The diagnosis of intraperitoneal extravasation of urine in the multiple trauma patient is often delayed, resulting in increased morbidity and mortality. To determine if intraperitoneal extravasation of urine can be detected by peritoneal lavage, an animal study was designed to investigate whethe urea nitrogen and creatinine levels in the urine, serum, and lavage fluid would be predictive of urinary extravasation. Seventeen adult mongrel dogs, weighing 21 to 30 kg, were divided into two groups. The six dogs in Group 1 were utilized as controls, and had peritoneal lavage (15 mL normal saline/kg) performed using the open technique (direct visualization of the peritoneum). Blood, urine and lavage area nitrogen and cretinine and lavage red cell count were measured. Group 2 (11 dogs) had varying amounts of urine (5 mL to 330 mL) instilled into the peritoneal cavity. Diagnostic peritoneal lavage was performed 30 to 45 minutes after the instillation of urine in all Group 2 animals. Group 2A (nine dogs) had urine instilled under direct visualization through a peritoneal lavage catheter. As bladder dome rupture is the most common cause of intraperitoneal urine extravasation, Group 2B (two dogs) had bladder dome ruptures performed by cystoscopic approach using the resectoscope. Cystograms were obtained in the bladder-ruptured dogs after completion of the peritoneal lavage to confirm intraperitoneal extravasation of bladder contents. In these animals, urine was instilled back into the bladder followng bladder rupture. Results demonstrate that urea nitrogen and creatinine can be measured in peritoneal lavage fluid when extravasation of urine is in amounts of 15 mL or greater, and not measureable in amounts of 5 mL or less. Four of the Group 2 dogs had hemoperitoneum (red cell count greater than 80,000). Measurements of lavage urea nitrogen and creatinine were not affected by the presence of blood in the peritoneum. Detection of peritoneal lavage creatinine and urea nitrogen was significantly different (P < .01 and P < .05, respectively) between the Group 1 and Group 2 animals by analysis of variance. When lavage urea nitrogen and creatinine exceed serum levels, with or without hemoperitoneum, intraperitoneal extravasation of urine should be suspected. Routine measurement of serum and of lavage urea nitrogen and creatinine is useful in the early diagnosis of intraperitoneal extravasation of urine in trauma patients.