Hydronephrosis
Hydronephrosis, which is the dilatation of the renal pelvis, is the most common urological anomaly, and uretero-pyelic junction obstruction (UPJO) is the main cause of hydronephrosis leading to surgical correction. The vast majority of hydronephrosis is n
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Maria Felicia Villani, Milena Pizzoferro, Simona Nappo, and Maria Carmen Garganese
4.1
Introduction
Hydronephrosis, which is the dilatation of the renal pelvis, is the most common urological anomaly. In the vast majority of cases, hydronephrosis is nowadays detected prenatally and is therefore asymptomatic. A limited number of cases are still diagnosed during childhood or adolescence after symptoms (urinary tract infection, hematuria, and pain), and their management is straightforward surgical in order to relieve symptoms and obstruction. Congenital hydronephrosis is detected from 1 to 5 % of all pregnancies. These patients offer a unique dilemma, since over 50–75 % of them will undergo resolution either prenatally or postnatally. The goals of treatment are therefore the early identification of patients at risk of significant uropathy and prevention of renal damage, avoiding at the same time overmedicalization of children not at risk. How should patients with hydronephrosis be evaluated prenatally and postnatally and who should be candidate to surgery have been the objects of intense debate over the past 20 years.
4.1.1
Prenatal Diagnosis
Prenatal hydronephrosis is one of the most common findings on prenatal ultrasound, with an incidence of 1–5 % of pregnancies. The most common clinically significant etiology of
M.F. Villani • M. Pizzoferro Nuclear Medicine Unit, Imaging Department, “Bambino Gesù” Children Hospital, Rome, Italy S. Nappo (*) Unit of Urology, “Bambino Gesù” Children Hospital, Rome, Italy e-mail: [email protected] M.C. Garganese Department of Diagnostic Imaging-Nuclear Medicine, IRCCS Bambino Gesù Paediatric Hospital, Rome, Italy
hydronephrosis is ureteropelvic junction obstruction (UPJO), which has an incidence of 1/1000–1/1250. There is no clear consensus defining the entity of prenatal dilatation and which should be considered clinically significant, and therefore requires postnatal investigation. The first and most common system of classification of hydronephrosis is by measuring the anteroposterior diameter (APD) of the renal pelvis. In the original work by Corteville, an APD >4 mm at 33 weeks and >7 mm at 40 weeks of gestational age were considered threshold for postnatal evaluation. Other studies have proposed clinically significant hydronephrosis as being >10 mm in the second trimester and >15 mm in the third trimester: such cutoff values are associated with a >50 % likelihood of UPJO in the postnatal age. However, one should keep in mind that dilatation also depends on gestational age, bladder fullness, and maternal hydration status. A second classification system of hydronephrosis was proposed by the Society of Fetal Urology (SFU) in 1993, based not only on the pyelic diameter but also on the global appearance of the renal collecting system. The SFU system goes from grade 1, with normal parenchymal thickness and/ or renal pelvis splitting, to grade 4 hydronephrosis, in which distension of pelvis and calyces goes together with parenchymal thinning. The SFU grading correlate
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