Pyonephrosis in childhood--is ultrasound sufficient for diagnosis?

The validity of ultrasound in the diagnosis of pyonephrosis in infants and children was retrospectively investigated in 14 patients. The disease was unilateral in 13 patients and bilateral in one. The diagnosis was proven by percutaneous nephrostomy in 7 and by operation in 7 patients. Ultrasound was true positive in 9 patients (10 kidneys) and false negative in 5. Large staghorn calculi were present in 2 of the 5 false negative cases. A group of 20 patients with simple hydronephrosis, investigated by percutaneous punctures, served as a control group. There were two false positive cases in this group. The sensitivity of sonography for the diagnosis of pyonephrosis was only 66.7%, which is considerably lower than in previous reports. We therefore recommend early sonographically guided percutaneous puncture of the renal pelvis whenever pyonephrosis is suspected.