This section is from the book "A Manual Of Pathology", by Guthrie McConnell. Also available from Amazon: A Manual Of Pathology.
Renal calculi are quite frequently found in the pelvis of the kidney and are composed of material precipitated from the urine. They may occur in the form of fine particles like sand or they may be so large as to be unable to pass out through the center. When small, the calculi can pass from the kidney without giving any pain. As they become larger they may pass out and give rise to severe renal colic; if quite large, the ureter may be completely blocked, and 30 dilatation and atrophy follow. The concretions may also vary in shape, some being round and smooth, while others may be very rough, and if large send prolongations into the calices. The commonest variety is composed of uric acid and oxalate of lime, but phosphatic stones are found occasionally. The color varies according to whether uric acid and urates or the phosphates predominate.
The presence of calculi may cause degeneration and atrophy as a result of pressure, and suppuration is quite common. Obstruction of the ureter gives rise to varying degrees of hydronephrosis.
The presence of calculi seems occasionally to antedate the formation of a carcinoma.