Disorders of the outflow tract of the urinary system from the renal pelves to the external portion of the urethra. Disorders of the kidney itself are considered in a separate article. See also Kidney disorders.
Renal pelves
The renal pelves, the sacs that carry urine from the kidney to the ureter, are subject to a number of disorders.
Anomalies of the renal pelves are common. The pelvis may be subdivided into two or more sacs which may end in a single or separate ureters. By itself such an anomaly is harmless, but if there is associated obstruction there may be symptoms of pain and also destruction of the renal tissue.
Calculi may arise in the renal pelvis, usually below the epithelial layer. The cause of calculi is usually some metabolic defect with excessive excretion of a waste material such as oxalates, urates, cystine, or calcium salts.
Fibrous bands and aberrant vessels to the kidneys are usually blamed for obstruction when no other intrinsic cause can be found for uretero-pelvic obstruction.
Acute infection of the pelvis is usually associated with infection of the kidney (pyelonephritis). Most commonly occurring in young girls, it produces fever, back pain, and dysuria.
Tumors of the pelvis are rare; when they do occur they are usually transitional-cell carcinomas of varying degrees of malignancy. They cause obstruction and blood in the urine (hematuria).
Ureters
These long thin tubes carry the urine from the renal pelvis to the bladder; they are subject to the same diseases as are the renal pelves.
Reduplication of the ureters at any point, from a double beginning and later fusion, to complete separation and separate implantation into the bladder, may be found. This anomaly is generally harmless unless obstruction is produced.
One of the commonest causes of excruciating abdominal and flank pain, often radiating to the groin or testicle, is the passage of small calculi or even showers of crystals through the ureter.
Occasionally the ureter is obstructed by external pressure from retroperitoneal fibrosis, tumor, or aortic aneurysm.
If the normal valvelike mechanism that prevents bladder urine from going back into the ureter is defective, vesico-ureteral reflux results. When the individual, usually a young girl, voids, some of the urine goes back into the ureter so the bladder is not completely emptied. This residual urine is subject to bacterial infection.
Tumors are usually transitional-cell carcinomas and do not differ appreciably from those seen in the pelvis and bladder.
Bladder
The urinary bladder is subject to anomalies, obstructions, inflammations, calculi, fistulae, and tumors.
A fairly common, distressing anomaly is exstrophy of the bladder, which is a failure of both the lower abdominal wall and anterior bladder wall to close. The urine appears directly through the abdominal wall defect.
Interference with normal complete emptying of the bladder may be the result of various factors. In one form, an elevation of the internal urethral opening above its normal dependent position creates an unemptied pool of residual urine in the bottom of the bladder. This elevation is usually caused in the male by prostatic enlargement and in the female by cystocele, a bulging of the lower bladder wall into the vagina. Another form of obstruction is blockage of the bladder neck or urethra by such diverse lesions as anomalous congenital valves, prostatic enlargement, calculi, tumors, or postgonorrheal urethral strictures. A third major cause of inadequate emptying is neurogenic, usually following spinal cord injury or disease.
Cystitis or inflammation of the urinary bladder is an extremely common affliction, annoying because of the accompanying painful, frequent micturition. Bladder calculi usually develop as a result of infection and obstruction. They often reach a considerable size, up to several inches in diameter. They are usually composed of multiple urinary constituents, particularly phosphates and urates.
Abnormal openings between the bladder or female urethra and the vagina are not unusual. Such fistulae most often follow injury during childbirth. The chief effects are infection and the constant leakage of urine through the vagina.
The bladder is frequently the site of tumors which are almost always of transitional-cell epithelial origin. Malignant change into transitional-cell carcinoma is common.
Female urethra
This structure is not often diseased. In older women a painful raspberrylike swelling composed of inflammatory tissue may appear at the external urethral opening and is known as a caruncle.
Male urethra
The prostate gland may develop cancer. However, options are available to treat this disease if detected at an early stage.
The urethra is prone to obstruction. The most common cause is a noncancerous growth of the prostate called benign prostatic hyperplasia. This growth is a natural process associated with aging and can occlude the prostatic urethra, causing progressive difficulty in starting the urinary stream and completely emptying the bladder. See also Reproductive system disorders.
