A small renal calculus, when formed, may be the beginning of several quite different sets of phenomena. Of these, the simplest and most favorable event is its descent through the ureter into the bladder, with its subsequent expulsion with the jet of urine from the urethra. If the calculus be small and smooth, the passage through the ureter may be attended with little or no uneasiness, but if it is large enough to fill or distend the tube, and especially if the stone be irregular and rough, its descent gives rise to excessively severe symptoms. These are pain in the back at the level of the kidney, in the side and groin corresponding to the ureter affected, sometimes shooting down the thigh; with retraction of the testicle; usually no fever, but much general depression; feeble pulse, coldness and paleness of the surface, fainting, and vomiting. The beginning of the attack is usually sudden, corresponding to the entrance of the calculus into the ureter, and the pain continues without intermission, though with some remissions, until its discharge into the bladder. The pain is usually of the severest, and is described as cutting or tearing in character. It is probable that an attack may sometimes end by the calculus, which has become engaged in the ureter, falling back into the pelvis instead of advancing through the ureter. In this case the pain ceases for the time, to be perhaps subsequently renewed, or, if the stone grow larger, so that it cannot re-enter the ureter, giving place to the symptoms due to irritation of the pelvis. The urine is usually diminished in amount until the arrival of the {44} calculus at the bladder, when the fluid that has been retained is suddenly discharged with the stone. Constant attempts to pass water during the passage downward of the calculus are the consequence of sympathetic irritation of the bladder, and not of accumulation of urine therein. The urine is likely to be bloody, but is not necessarily so. The smoothness or roughness of the surface of the stone is of much importance as determining the presence of this symptom. The DIAGNOSIS of renal colic is usually not difficult, but it may not always be readily distinguished from hepatic or intestinal colic. The suddenness of the attack and intensity of the pain, its location in the side and downward to the groin, will in most cases make the condition very characteristic. From hepatic colic or the passage of a gall-stone the situation of the pain, which is in the latter affection naturally somewhat farther forward, the tenderness on pressure in the same region, and often the whitish color of the stools or the presence of jaundice, as well as the history of former attacks, will usually make the distinction a matter of a high degree of probability.