Ultrasonography in the detection of residual urine

Eleven patients with distended urinary bladders (10 diabetics with autonomic neuropathy and one patient with prostatic hypertrophy) were examined by ultrasonography in an attempt to define the volumes detectable by this technique. Incremental volumes of saline were instilled through indwelling Foley catheters with ultrasonographic examination at each volume. The ultrasonograms obtained were presented to two radiologists trained in ultrasonography, who were asked to identify the presence of residual urine. There was 97% certainty of recognizing the presence of 100-cc residual volumes and 100% certainty of recognizing 150-cc residual volumes. It is concluded that residual urine volumes greater than 100 cc are clinically detectable by ultrasonography, a noninvasive alternative for diagnosing this common diabetic condition.