The layered pyelogram in hydronephrosis.

Fifty patients were studied with erect films at excretory urography. Twenty-eight had hydronephrosis, bilateral in two cases; a total of 30 hydronephrotic kidneys were therefore investigated. Thin layers of contrast medium were shown in the dilated calyces in 29 of the 30 kidneys. The layered pyelogram is a simple, sensitive urographic sign of hydronephrosis, which may be demonstrated in the absence of a discernible pyelogram in the routine film or tomograph. The basis of layering has been investigated by simple experiments. Since the layered pyelogram may be the only urographic evidence of a poorly excreting hydronephrotic kidney, erect films should be routinely used at excretory urography when this condition is to be diagnosed or excluded.