Pediatr Nephrol (2013) 28:237–243 DOI 10.1007/s00467-012-2240-7
EDUCATIONAL REVIEW
Current management of antenatal hydronephrosis Kleiton G. R. Yamaçake & Hiep T. Nguyen
Received: 2 April 2012 / Revised: 31 May 2012 / Accepted: 31 May 2012 / Published online: 27 July 2012 # IPNA 2012
Abstract The strategy for the management of children with urinary tract anomalies has changed considerably as a result of the development of ultrasound equipment and techniques that allow for detailed fetal evaluation. Hydronephrosis is the most common urogenital anomaly detected, suggesting that an obstructive process may be potentially present. The goal of postnatal management is to identify and treat those patients whose renal function is at risk, while leaving alone the high percentage of patients who are at no risk of renal damage. This management involves a spectrum of radiological, medical, and surgical interventions for diagnosis, surveillance, and treatment. In this article, we review our current understanding of the natural history of antenatal hydronephrosis and its management. Keywords Hydronephrosis . Prenatal diagnosis . Fetal Intervention . Infants . Management . Prenatal ultrasonography
Introduction The use of prenatal ultrasound (US) has increased significantly over the past 20 years. In 1980, prenatal US was performed in 33 % of pregnancies, by 1987 in 78 %, and currently in over 90 %. The incidence of a significant structural abnormality detected by prenatal US is 1 % [1]. Congenital anomalies of the urinary system are the most common abnormalities detected during routine antenatal US (20–30 % of anomalies identified prenatally), representing a broad range of disorders, each with a myriad of prognoses K. G. R. Yamaçake : H. T. Nguyen (*) Department of Urology, Children’s Hospital Boston, Harvard Medical School, 300 Longwood Avenue, Hunnewell-353, Boston, MA 02115, USA e-mail:
[email protected]
and each requiring different therapies. The major challenges of postnatal management are: (1) to distinguish between patients who are at risk for renal damage and those who have anatomic variants without consequence to renal function; (2) to maximize the detection of significant abnormalities while minimizing the use of invasive and sometimes distressing testing for children who would have no benefits from such tests and which would cause unnecessary anxiety for parents. The etiology and the clinical outcome of hydronephrosis are varied [2], leading to much debate on the significance, work-up, and management of antenatal hydronephrosis (ANH) [3–5]. In this review, we evaluate our current understanding of prenatal detection and postnatal evaluation of ANH, as well as the wide spectrum of possible interventions.
Defining and grading ANH The parameters used to define ANH and determine what will be clinically significant are controversial. Despite efforts to develop a more objective method, the classification of hydronephrosis remains somewhat subjective. Currently, the system most widely used to grade hydronephrosis is a qualitative scale, in which the degree is characterized as being mild, moderate, or severe. Several systems have been proposed in attempts to standardize this grading system, and these are used in varying degrees. Several authors have assessed the threshold for diagnosing ANH associated with abnormalities of the urinary tract. One common method of diagnosing ANH is by measuring the anterior–posterior diameter (APD) of the renal pelvis using US. The currently accepted standard for APD considered to be of clinical significance is based on the original work by Corteville et al. [4] and reiterated by other studies [6–9]. In the Corteville series, an APD of >4 mm at 33 weeks gestational age (GA) or of >7 mm at 40 weeks GA
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demonstrated a sensitivity of 100 % for the identification of those patients with abnormal renal function or those who required subsequent intervention postnatally, suggesting an upper limit threshold of ANH that requires postnatal evaluation. A number of other studies noted persistent postnatal uropathies when the APD of the fetal renal pelvis measures >6 mm at 8 mm at 20–30 weeks, and >10 mm at >30 weeks gestation [10, 11]. In 1993, the Society for Fetal Urology (SFU) proposed a classification based not on the size of the renal pelvis (APD diameter), but on the appearance of the intrarenal collecting system [12]. This classification system incorporates collecting system dilation with renal parenchymal findings. The proposed SFU system is a spectrum, with grade 1 demonstrating normal parenchymal thickness and only renal pelvis splitting and grade 4 revealing distention of the renal pelvis and calyces in addition to parenchymal thinning (illustrated on the link http://www.uab.edu/images/peduro/ SFU/sfu_grading_on_web/sfu_grading_on_web.htm). It was intended that this more extensive classification of ANH might be helpful in predicting which children will require postnatal evaluation and management. It has been observed that the SFU grade of hydronephrosis correlates with the potential for postnatal resolution of the hydronephrosis. SFU grade 1 hydronephrosis resolves in approximately 50 % of patients, whereas grades 2, 3, and 4 hydronephrosis resolve in 36, 16, and 3 % of cases, respectively [13]. Unfortunately, the more quantitative grading systems, such as the SFU grading system, have failed to be adopted universally, and ANH is still a subjective determination by the interpreting physician. Because of this diversity of methods, it is important that when reporting the grading of ANH that the method used to diagnose and grade the finding is reported as well.
Etiology of ANH Various urological conditions may result in the finding of ANH. Some are associated with significant morbidity, while others have a fairly benign course. The differential diagnosis of ANH is listed in Table 1, with the incidence and prenatal US findings suggestive of the diagnosis. Hydronephrosis that is transient or mild in nature without any clinical sequelae is the most common, accounting for 50–70 % of the cases of ANH. Obstruction at the ureteropelvic junction (UPJ), either due to an adynamic segment, polyp, or crossing of lower pole vessels, accounts for another 10–30 % of cases of ANH [13]. Approximately 10–30 % of patients with ANH will have primary vesicoureteral reflux (VUR) [14]. Other causes of ANH, such as ureterovesical junction (UVJ) obstruction and posterior urethral valves (PUV) are much less common [15–17].
Pediatr Nephrol (2013) 28:237–243 Table 1 Differential diagnosis of prenatal hydronephrosis Etiology
Incidence
Prenatal ultrasound findings
Transient/physiologic
50–70 %
Ureteropelvic junction (UJP) obstruction
10–30 %
Vesicoureteral reflux (VUR)
10–40 %
Ureterovesical junction (UVJ) obstruction Multicystic dysplastic kidney (MCDK)
5–15 %
Posterior urethral valves (PUV)
1–5 %
Ureterocele
1–3 %
Isolated hydronephrosis, most often mild Moderately (10–15 mm) or severely (>15 mm) dilated renal pelvis in the absence of any dilation of ureter or bladder Variation in the degree of ANH during the time of US evaluation (in general, there are no specific US findings that are pathonomic) Hydronephrosis and dilated ureter to level of the UVJ Varying sizes of randomly located renal cysts, a large noncommunicating central cyst, and nonrenoform shape A combination of the following: posterior urethral dilatation (key hole sign); a full bladder with thickened wall; oligo- or anhydramnios; unilateral or bilateral hydronephrosis; increased renal echogenicity A cystic mass in the bladder, and hydroureteronephrosis to the level of the obstructing ureterocele
Less common etiology: ectopic ureter, urethral atresia, prune-belly syndrome, polycystic kidney diseases, and renal cysts
