Hydronephrosis: Abnormal enlargement or swelling of a KIDNEY due to dilation of the KIDNEY CALICES and the KIDNEY PELVIS. It is often associated with obstruction of the URETER or chronic kidney diseases that prevents normal drainage of urine into the URINARY BLADDER.Ureteral Obstruction: Blockage in any part of the URETER causing obstruction of urine flow from the kidney to the URINARY BLADDER. The obstruction may be congenital, acquired, unilateral, bilateral, complete, partial, acute, or chronic. Depending on the degree and duration of the obstruction, clinical features vary greatly such as HYDRONEPHROSIS and obstructive nephropathy.Kidney Pelvis: The flattened, funnel-shaped expansion connecting the URETER to the KIDNEY CALICES.Urethral Obstruction: Partial or complete blockage in any part of the URETHRA that can lead to difficulty or inability to empty the URINARY BLADDER. It is characterized by an enlarged, often damaged, bladder with frequent urges to void.Urography: Radiography of any part of the urinary tract.Ureteral Diseases: Pathological processes involving the URETERS.Ureter: One of a pair of thick-walled tubes that transports urine from the KIDNEY PELVIS to the URINARY BLADDER.Vesico-Ureteral Reflux: Retrograde flow of urine from the URINARY BLADDER into the URETER. This is often due to incompetence of the vesicoureteral valve leading to ascending bacterial infection into the KIDNEY.Radioisotope Renography: Graphic tracing over a time period of radioactivity measured externally over the kidneys following intravenous injection of a radionuclide which is taken up and excreted by the kidneys.Urinary Tract: The duct which coveys URINE from the pelvis of the KIDNEY through the URETERS, BLADDER, and URETHRA.Technetium Tc 99m Mertiatide: A technetium diagnostic aid used in renal function determination.Fetal Diseases: Pathophysiological conditions of the FETUS in the UTERUS. Some fetal diseases may be treated with FETAL THERAPIES.Flank Pain: Pain emanating from below the RIBS and above the ILIUM.Retroperitoneal Fibrosis: A slowly progressive condition of unknown etiology, characterized by deposition of fibrous tissue in the retroperitoneal space compressing the ureters, great vessels, bile duct, and other structures. When associated with abdominal aortic aneurysm, it may be called chronic periaortitis or inflammatory perianeurysmal fibrosis.Urolithiasis: Formation of stones in any part of the URINARY TRACT, usually in the KIDNEY; URINARY BLADDER; or the URETER.Kidney Calices: Recesses of the kidney pelvis which divides into two wide, cup-shaped major renal calices, with each major calix subdivided into 7 to 14 minor calices. Urine empties into a minor calix from collecting tubules, then passes through the major calix, renal pelvis, and ureter to enter the urinary bladder. (From Moore, Clinically Oriented Anatomy, 3d ed, p211)Ureteral Neoplasms: Cancer or tumors of the URETER which may cause obstruction leading to hydroureter, HYDRONEPHROSIS, and PYELONEPHRITIS. HEMATURIA is a common symptom.Urologic Surgical Procedures: Surgery performed on the urinary tract or its parts in the male or female. For surgery of the male genitalia, UROLOGIC SURGICAL PROCEDURES, MALE is available.Ureteral Calculi: Stones in the URETER that are formed in the KIDNEY. They are rarely more than 5 mm in diameter for larger renal stones cannot enter ureters. They are often lodged at the ureteral narrowing and can cause excruciating renal colic.Diagnostic Techniques, Urological: Methods and procedures for the diagnosis of diseases or dysfunction of the urinary tract or its organs or demonstration of its physiological processes.Ultrasonography, Prenatal: The visualization of tissues during pregnancy through recording of the echoes of ultrasonic waves directed into the body. The procedure may be applied with reference to the mother or the fetus and with reference to organs or the detection of maternal or fetal disease.Kidney: Body organ that filters blood for the secretion of URINE and that regulates ion concentrations.Urologic Diseases: Pathological processes of the URINARY TRACT in both males and females.Polyuria: Urination of a large volume of urine with an increase in urinary frequency, commonly seen in diabetes (DIABETES MELLITUS; DIABETES INSIPIDUS).Dilatation, Pathologic: The condition of an anatomical structure's being dilated beyond normal dimensions.Cystotomy: Surgical incision or puncture into a URINARY BLADDER. Cystotomy may be used to remove URINARY CALCULI, or to perform tissue repair and reconstruction.Pessaries: Devices worn in the vagina to provide support to displaced uterus or rectum. Pessaries are used in conditions such as UTERINE PROLAPSE; CYSTOCELE; or RECTOCELE.Meningism: A condition characterized by neck stiffness, headache, and other symptoms suggestive of meningeal irritation, but without actual inflammation of the meninges (MENINGITIS). Spinal fluid pressure may be elevated but spinal fluid is normal. (DeJong, The Neurologic Examination, 4th ed, p673)Urogenital Abnormalities: Congenital structural abnormalities of the UROGENITAL SYSTEM in either the male or the female.Dysuria: Painful URINATION. It is often associated with infections of the lower URINARY TRACT.