The diagnosis of hydronephrosis requires a thorough history, physical examination, and often includes laboratory testing and imaging. Typically, an ultrasound can be used to determine the condition of the patient's urinary system, specifically the kidneys and bladder. In addition, computed tomography (
CT) scans and magnetic resonance imaging (
MRI) can provide clearer images of the urinary tract and any obstructions. Prenatal diagnosis is possible and occurs in 1-5% of pregnancies. Most cases of fetal hydronephrosis are incidentally detected by routine screening ultrasounds obtained during pregnancy. In cases of mild prenatal hydronephrosis, approximately half are temporary and spontaneously resolve by the time the infant is born. In some cases of prenatally identified hydronephrosis, the hydronephrosis persists but is not associated with urinary tract obstruction. This type of hydronephrosis is commonly referred to as non-refluxing, non-obstructive hydronephrosis. For these children, regression of the hydronephrosis typically occurs spontaneously by age 3. However, in cases of moderate to severe hydronephrosis, spontaneous resolution is less likely, and prenatal or postnatal surgical intervention may be required. Imaging studies are also a large component of hydronephrosis diagnosis. The types of imaging are selected based on the patient's presentation and medical history. An ultrasound is commonly used for quick diagnosis of hydronephrosis and are the preferred imaging test for pregnant patients. A CT scan, however, provides more detailed imaging and is most effective at identifying kidney stones, tumors, or other causes of obstruction. Although IVUs were once among the most popular imaging modalities for identifying issues within the urinary system, ultrasound, CT, and MRI imaging have become increasingly popular. Real-time ultrasounds and Doppler ultrasound tests, in conjunction with vascular resistance testing, help determine how a given obstruction affects urinary functionality in hydronephrotic patients. Another diagnostic tool for identifying the location of the obstruction is the Whitaker (or pressure perfusion) test. The Whitaker test is performed by percutaneously accessing the collecting system of the kidney and introducing liquid at high pressure and constant rate while simultaneously measuring the pressure within the renal pelvis. A rise in pressure above 22 cm H2O suggests that the urinary collection system is obstructed. The choice of imaging depends on the clinical presentation, history, symptoms, and physical examination findings. Typically, the initial investigation of suspected hydronephrosis involves a CT scan of the abdomen/pelvis or renal ultrasound. CT scans are highly sensitive; however, they expose individuals to ionizing radiation and can be costly. In cases where there is a reason to avoid radiation exposure (pregnancy, pediatrics), CT is not used. Ultrasound, however, is less sensitive but does not expose individuals to radiation, is less expensive, and faster. 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 typically also obtained to exclude the possibility of vesicoureteral reflux or anatomical abnormalities, such as posterior urethral valves. Finally, if hydronephrosis 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:CT of peripelvic cysts with non-contrast and urography.jpg|Peripelvic
renal cysts may look like hydronephrosis on non-contrast CT (left image). However,
CT urography (at right) reveals non-dilated
calyces and
pelvises.
Grading There are two widely used grading systems of hydronephrosis. The Society of Fetal Ultrasound (SFU) developed a grading system for hydronephrosis in 1993 that was initially intended for use in neonatal and infant hydronephrosis, but is now used for grading hydronephrosis in adults as well. Additionally, the Onen grading system was developed in 2007 for the grading of hydronephrosis. • Grade 0 (no hydronephrosis) – No renal pelvis dilation. Calyceal walls are opposed to each other • Grade 1 (mild hydronephrosis) – Mild dilatation of the renal pelvis without dilatation of the calyces. No parenchymal atrophy. • Grade 2 (mild hydronephrosis) – Mild dilatation of the renal pelvis and calyces. No parenchymal atrophy • Grade 3 (moderate hydronephrosis) – Moderate renal pelvis dilation and calyces. Blunting of fornices and flattening of papillae. Mild cortical thinning may be visualized. • Grade 4 (severe hydronephrosis) – Obvious dilatation of the renal pelvis and calyces. Renal atrophy is seen as cortical thinning.
Onen Grading System • Grade 0 – No hydronephrosis • Grade 1 – Dilatation of the renal pelvis alone • Grade 2 – Dilation of the renal pelvis and calyceal dilatation • Grade 3 – Pelvic and calyceal dilation with less than 50% renal parenchymal loss • Grade 4 – Pelvic and calyceal dilation with more than 50% parenchymal loss ==Treatment==