Calculi are frequently found in the kidney consisting usually of uric acid, sometimes of oxalates, more rarely of phosphates. Calculous disease of the bladder (q.v.) is generally the sequel to the formation of a stone in the kidney, which, passing down, becomes coated by the salts in the urine. Calculi are usually formed in the pelvis of the kidney, and their formation is dependent either on the excessive amounts of uric acid, oxalic acid, etc., in the blood, or on an alteration in the composition of the urine, such as increased acidity, leading to abnormal deposition. The formation of abnormal crystals is often due to the presence of some colloid, such as blood, mucus or albumen, in the secretion, modifying the crystalline form. Once a minute calculus has been formed, its subsequent growth by de position of further layers of the material is highly probable. Calculi formed in the pelvis of the kidney may be single and large, forming, indeed, an actual cast of the interior of the expand ed kidney. At other times they are multiple and of varying size. Serious complications may result from the presence of a stone in the kidney, such as hydronephrosis, from the urinary secretion being pent up behind the obstruction, or complete suppression, which is apparently produced reflexly through the nervous sys tem. In such cases the surgical removal of the stone is often followed by the restoration of the renal secretion. (See CALCULI.) The symptoms of renal calculus may be very slight, even entire ly absent if the stqne is moulding itself into the interior of the kidney; but if the stone is movable, heavy and rough it may cause great distress, especially during exercise. There will probably be blood in the urine ; and there will be pain in the loin and thigh and down into the testicle. The testicle also may be drawn up by its suspensory muscle, and there may be irritability of the bladder. With stone in one kidney the pains may be actually referred to the kidney of the other side. Generally, but not always, there is tenderness in the loin. If the stone is composed of lime it may throw a shadow on the Röntgen plate, but other stones may give no shadow.
Renal colic is the acute pain felt when a small stone is travel ling down the ureter to the bladder. The pain is at times so acute that fomentations, morphia and hot baths fail to ease it, and nothing short of chloroform gives relief. The treatment for renal calculus is surgical.
Inflammation of the pelvis of the kidney is generally produced by the extension of gonorrhoeal or other septic inflam mation upwards from the bladder and lower urinary tract, or by the presence of stone or of tubercle in the pelvis of the kidney. Pyonephrosis, or distension of the kidney with pus, may result as a sequel to pyelitis or as a complication of hydronephrosis ; in many cases the inflammation spreads to the capsule of the kidney and leads to the formation of an abscess outside the kidney—a perinephritic abscess. In some cases a perinephritic abscess re sults from a septic plug in a blood-vessel of the kidney, or it may occur as the result of an injury to the loose cellular tissue surrounding the kidney, without lesion of the kidney.
or distension of the kidney with pent-up urine, results from intermittent obstruction of the ureter. Obstruc tion of the ureter, causing hydronephrosis, is likely to be due to the impaction of a stone, or to pressure on the ureter from a tumour in the pelvis—as, for instance, a cancer of the uterus— or to some abnormality of the ureter. Sometimes a kink of the ureter of a movable kidney causes hydronephrosis. The hydrone
phrosis produced by obstruction of the ureter may be intermit tent; and when a certain degree of distension is produced, either as a result of the shifting of the calculus or of some other cause, the obstruction is temporarily relieved in a great outflow of urine, and the urinary discharge is re-established. When the hydronephrosis has long existed the kidney is converted into a sac, the remains of the renal tissues being spread out as a thin layer.
Diseases of the kidney produce altera tions in the composition of the urine ; either the proportion of the normal constituents being altered, or substances not normally present being excreted. There are two forms of suppression of the urine : obstructive, where the ureter is blocked by stone or other morbid process; non-obstructive, which is apt to occur in severe acute nephritis. In other cases complete suppression may occur as the result of shock or of injuries to distant parts of the body, as after severe surgical operations. In some diseases in which the quantity of urinary water excreted is normal, or even greater than normal, the efficiency of the renal activity is really diminished, inasmuch as the urine contains few solids. In estimat ing the efficiency of the kidneys it is necessary to take into con sideration the quantity of solid matter daily excreted, as shown by the specific gravity of the urine. The nitrogenous constituents —urea, uric acid, creatinin, etc.—vary greatly in amount in dif ferent diseases. In most renal diseases the quantities of these substances are diminished because of the physiological impair ment of the kidney. The chief abnormal constituents of the urine are serum-albumin, serum-globulin, albumoses (albumosuria), blood (haematuria), blood pigment (haemoglobinuria), pus (pyuria), chyle (chyluria), and pigments such as in melanuria and urobilinuria.
These may be persistent or intermittent or transitory. The most important persistent effects are, first, nutritional changes leading to general ill-health, wasting and cachexia; and, secondly, cardio-vascular phenomena, such as enlargement (hypertrophy) of the heart, and thickening of the inner, and degeneration of the middle, coat of the smaller arteries. Amongst the intermittent or transitory effects are dropsy, sec ondary inflammations of certain organs and serous cavities, and uraemia. Some of these effects are seen in every form of severe kidney disease, and uraemia may occur in any advanced kidney disease. Renal dropsy is chiefly seen in acute and chronic Bright's disease, and the cardiac and arterial changes are commonest in cases of granular kidney, but may be absent in other diseases which destroy the kidney tissue, such as hydronephrosis. Uraemia is a toxic condition, and three varieties are recognized—the acute, the chronic and the latent. In part it depends upon the action of poisons retained in the body owing to the deficient action of the kidneys. It is also probable that abnormal substances having a toxic action, e.g., carbamate of ammonia, are produced as a result of a perverted metabolism. The dropsy of renal disease, according to some authorities, is due to effects produced in the capillaries by the presence of abnormal substances in the blood, but the question is not beyond dispute. High arterial tension, cardiac hypertrophy, and arterial degeneration may also be of toxic origin, or they may be produced by an attempt of the body to maintain an active circulation through the greatly diminished amount of kidney tissue available.
See also UROLOGY.