Introduction
This topic covers urinary stone disease (urolithiasis), mainly kidney stones, and hydronephrosis, the dilatation of the renal collecting system caused by obstruction. Both are common causes of acute flank pain. In the exam, link each imaging choice to the clinical question: is there a stone, where is it, and is the kidney obstructed?
Kidney stone disease: definition and composition
Nephrolithiasis is the formation of solid crystal concretions in the excretory system of the kidney (renal pelvis and calyces). Stones can reach a few cm in size and interfere with kidney function; a stone that passes causes a lot of pain. A stone that has moved into the ureter is called ureterolithiasis. Stones can be divided into X-ray positive and X-ray negative. Stones form when urine becomes supersaturated with crystal-forming salts, when inhibitors such as citrate are deficient, and when a nidus such as a Randall plaque or debris is present. Stone composition determines both radiological appearance and treatment.