Renal ultrasonography of<unk>  caused by a left ureteral stone.<unk>  due to a kidney stone at the ureteral vesicular junction seen on CT scan Prenatal diagnosis is possible, and in fact, most cases in pediatric patients are incidentally detected by routine screening ultrasounds obtained during pregnancy. However, approximately half of all prenatally identified<unk>  is transient, and resolves by the time the infant is born, and in another 15%, the<unk>  persists but is not associated with urinary tract obstruction (so-called non-refluxing, non-obstructive<unk> . For these children, regression of the<unk>  occurs spontaneously, usually by age 3. However, in the remaining 35% of cases of prenatal<unk> , a pathological condition can be identified postnatally. Diagnostic workup depends on the age of the patient, as well as whether the<unk>  was detected incidentally or prenatally or is associated with other symptoms. Blood tests (such measurement of creatinine) are typically indicated, though they must be interpreted cautiously. Even in cases of severe unilateral<unk> , the overall kidney function may remain normal since the unaffected kidney will compensate for the obstructed kidney. Urinalysis is usually performed to determine the presence of blood (which is typical for kidney stones) or signs of infection (such as a positive leukocyte esterase or nitrite). Impaired concentrating ability or elevated urine pH (distal renal tubular acidosis) are also commonly found due to tubular stress and injury. Imaging studies Imaging studies, such as an intravenous urogram (IVU), renal ultrasonography, CT, or MRI, are also important investigations in determining the presence and/ or cause of<unk> . Whilst ultrasound allows for visualisation of the ureters and kidneys (and determine the presence of<unk>  and / or hydroureter), an IVU is useful for assessing the anatomical location of the obstruction. Antegrade or retrograde pyelography will show similar findings to an IVU but offer a therapeutic option as well. Real-time ultrasounds and Doppler ultrasound tests in association with vascular resistance testing helps determine how a given obstruction is effecting urinary functionality in hydronephrotic patients. In determining the cause of<unk> , the location of obstruction can be determined with a Whittaker (or pressure perfusion) test, wherein the collecting system of the kidney is accessed percutaneously, and the liquid is introduced at high pressure and constant rate of 10ml/min while measuring the pressure within the renal pelvis. A rise in pressure above 22 cm H2O suggests that the urinary collection system is obstructed. When arriving at this pressure measurement, bladder pressure is subtracted from the initial reading of internal pressure. (The test was first described by Whittaker in 1973 to test the hypothesis that patients whose<unk>  persists after the posterior urethral valves have been ablated usually have ureters that are not obstructed, even though they may be dilated.) Kay recommends that a neonate born with untreated in utero<unk>  receive a renal ultrasound within two days of birth. A renal pelvis greater than 12mm in a neonate is considered abnormal and suggests significant dilation and possible abnormalities such as obstruction or morphological abnormalities in the urinary tract. The choice of imaging depends on the clinical presentation (history, symptoms and examination findings). In the case of renal colic (one sided loin pain usually accompanied by a trace of blood in the urine) the initial investigation is usually a spiral or helical CT scan. This has the advantage of showing whether there is any obstruction of flow of urine causing<unk>  as well as demonstrating the function of the other kidney. Many stones are not visible on plain X-ray or IVU but 99% of stones are visible on CT and therefore CT is becoming a common choice of initial investigation. CT is not used, however, when there is a reason to avoid radiation exposure, e.g. in pregnancy. For incidentally detected prenatal<unk> , the first study to obtain is a postnatal renal ultrasound, since as noted, many cases of prenatal<unk>  resolve spontaneously. This is generally done within the first few days after birth, although there is some risk that obtaining an imaging study this early may miss some cases of mild<unk>  due to the relative oliguria of a newborn. Thus, some experts recommend obtaining a follow-up ultrasound at 4–6 weeks to reduce the false-negative rate of the initial ultrasound. A voiding cystourethrogram (VCUG) is also typically obtained to exclude the possibility of vesicoureteral reflux or anatomical abnormalities such as posterior urethral valves. Finally, if<unk>  is significant and obstruction is suspected, such as a ureteropelvic junction (UPJ) or ureterovesical junction (UVJ) obstruction, a nuclear imaging study such as a MAG-3 scan is warranted. File:BilateralHydroMark.CT scan of bilateral<unk>  due to a bladder cancer File:Hydronephrosis.Massive<unk>  as marked by the arrow. File:UOTW 10 - Ultrasound of the Week 1.Renal ultrasonography of<unk>  File:UOTW 10 - Ultrasound of the Week 3.Stone causing<unk>  File:UOTW 10 - Ultrasound of the Week 2.Stone causing<unk>  File:UOTW 10 - Ultrasound of the Week 4.Urine jets File:CT of peripelvic cysts with non-contrast and urography.Peripelvic renal cysts may look like<unk>  on non-contrast CT (left image). However, CT urography (at right) reveals non-dilated calyces and pelvises. Grading right The Society of Fetal Ultrasound (SFU) has developed a grading system for<unk> , initially intended for use in neonatal and infant<unk> , but it is now used for grading<unk>  in adults as well: * Grade 0 – No renal pelvis dilation. This means an anteroposterior diameter of less than 4 mm in fetuses up to 32 weeks of gestational age and 7 mm afterwards. In adults, cutoff values for renal pelvic dilation have been defined differently by different sources, with anteroposterior diameters ranging between 10 and 20 mm. About 13% of normal healthy adults have a transverse pelvic diameter of over 10 mm. * Grade 1 (mild) – Mild renal pelvis dilation (anteroposterior diameter less than 10 mm in fetuses) without dilation of the calyces nor parenchymal atrophy * Grade 2 (mild) – Moderate renal pelvis dilation (between 10 and 15 mm in fetuses), including a few calyces * Grade 3 (moderate) – Renal pelvis dilation with all calyces uniformly dilated. Normal renal parenchyma * Grade 4 (severe) – As grade 3 but with thinning of the renal parenchyma
Hydronephrosis
Pyonephrosis
Glomerulonephrosis
Pyelonephritis
Ureteric stricture
Ureteral cancer
Salpingitis
Obstructive uropathy