HYDRONEPHROSIS
Overview
Hydronephrosis is one of the most common fetal anomalies, detected in 1% of pregnancies. A sign rather than a diagnosis, hydronephrosis references significant dilation of the upper urinary tract. Common causes of hydronephrosis include physiologic hydronephrosis, ureteropelvic or ureterovesical junction (UVJ) obstruction, posterior urethral valves (PUVs), Eagle–Barrett (prune belly) syndrome, and vesicoureteral reflux (VUR; Martin, Fanaroff, & Walsh, 2011).
Prenatal diagnosis is highly correlated with postnatal findings (Policiano et al., 2015). The goal of prenatal ultrasound is reduction in the incidence of postnatal urinary tract infection (UTI) and prevention of acquired renal damage in asymptomatic patients. Early identification of the finding affords the opportunity for prenatal consultation with nephrology or urology specialists, facilitating postnatal care coordination. Prenatal interventions are limited in efficacy and associated with increased risk of preterm labor and chorioramnionitis. Expectant prenatal management prevails, with fetal surgical intervention rarely indicated (Liu, Armstrong, & Maizels, 2014).
Background
Occurring unilaterally or bilaterally, hydronephrosis is characterized by enlargement of the renal collecting system, including renal calyces and pelvis. The etiology is varied although it may be obstructive in origin. Prenatal hydronephrosis may be transient or secondary to clinically significant abnormalities of the kidney and urinary tract. As much as 15% of prenatally detected hydronephrosis occurs because of delayed fetal ureter maturation independently of anatomic abnormalities of the upper urinary tract (physiologic hydronephrosis) and typically resolve spontaneously before birth or by 2 years of age. The incidence of significant urinary tract disease in identified cases of hydronephrosis has been estimated at 0.2% to 0.4% (Aslan, 2005).
Ultrasound-guided prenatal grading of unilateral or bilateral hydronephrosis informs prenatal and postnatal management. The grading system of the Society of Fetal Urology (grades I–V) describes the degree of calyceal dilatation and renal parenchymal thickness.
Grading may be used as a guideline to describe the degree of hydronephrosis. Measuring the greatest dimension of the renal pelvis has also gained favor for defining hydronephrosis. An unfavorable outcome, including need for postnatal surgery, has been associated with a renal anteriorposterior (AP) diameter of 7 mm or more in the third trimester and the presence of urinary tract anomalies (Plevani et al., 2014).
157Prenatal ultrasonography findings, including increased renal echogenicity, bilateral disease, and oligohydramnios may be associated with long-term renal dysfunction and deserve additional prenatal consultation with nephrology or urology specialists (Vogt & Dell, 2011). Despite improvements in technique, prenatal imaging may not detect all defects of the urinary tract.
Clinical Aspects
The majority of cases of hydronephrosis are unilateral and mild, necessitating postnatal follow-up with serial ultrasonography beginning at 7 to 10 days of age to resolution (or progression) of findings. Newborns with a normal ultrasound in the first week of life should undergo a repeated study at 4 to 6 weeks of age to eliminate an initial false-negative study owing to relative dehydration or low glomerular filtration rate (GFR). Two normal postnatal ultrasound examinations exclude the presence of significant renal disease.
Sencan et al. (2014) describe a low incidence of UTI and VUR in children with mild antenatal hydronephrosis (ANH) at 2 weeks through 3 months of age, suggesting that routine voiding cystourethrogram (VCUG) and long-term antibiotic prophylaxis should be initiated only in symptomatic children presenting with UTI. Moderate to severe unilateral hydronephrosis prompts postnatal study, including ultrasonography followed by a VCUG and a functional renal scan (diuretic renography) to identify etiology precisely.
Mild isolated bilateral hydronephrosis should similarly be followed with sequential ultrasound examination. Causes of bilateral hydronephrosis include UVJ obstruction, referring to a blockage in the region of the UVJ where the ureter meets the bladder. The obstruction impedes flow of urine down to the bladder, causing the urine to back up into and dilate the ureters and kidney, appreciated on ultrasound as megaureter (dilated ureter) and hydronephrosis. Moderate to severe bilateral hydronephrosis may indicate potential obstructive uropathy and requires prompt, detailed evaluation postnatally, particularly in male infants who have an increased risk of PUVs.
In cases of severe bilateral hydronephrosis (greater than 15-mm AP diameter in third trimester), postnatal ultrasonography should be completed in the first 48 hours of life and prophylactic antibiotic therapy initiated. A VCUG follows with the continuation of antibiotic therapy or additional renal scans to complete diagnostic evaluation and determine presence and location of obstruction.
ASSESSMENT
Trending the blood pressure is important to monitor for hypertension as well as temperature to monitor for sepsis. Strict intake and output (I&O) is crucial and need to be calculated every 4 hours. Infants may need intravenous (IV) fluids to maintain hydration and IV antibiotics to prevent infection in the bladder or kidneys. If the hydronephrosis is severe, the infant may need a Foley catheter to keep the kidneys drained. Proper nutrition for growth and development is 158important and mothers should be encouraged to provide breast milk although there is a special commercial formula available.
NURSING INTERVENTIONS, MANAGEMENT, AND IMPLICATIONS
Treatment of all infants with hydronephrosis has the same goal, which is to preserve renal function. Nurses must be able to assess infant renal function and inform the other members of the health care team of any acute or subtle changes they observe in the infant.
In addition, nurses must understand normal and abnormal laboratory values. Serial renal function panels are performed to determine kidney function. Waste products, urea/blood urea nitrogen (BUN), and creatinine (Cr) can accumulate in the blood causing serious damage to the kidneys.
Parent education is of primary importance even if the parents are aware of the diagnosis prenatally. The different tests their infant may undergo must be reinforced to them at a level they can understand. No matter what degree of hydronephrosis, it remains a frightening experience and parents need support. An important aspect is the need for follow-up with a pediatric nephrologist and continuation of antibiotics if required.
OUTCOMES
Spontaneous resolution of mild hydronephrosis is greater than moderate or severe hydronephrosis. Infants with moderate/severe hydronephrosis are at greater risk for a UTI (Conkar, Memmedov, & Mir, 2016), but still may be treated conservatively.
Summary
Neonatal hydronephrosis is often self-limiting, but may signal obstructive pathology of the lower or upper urinary tract. Prenatal diagnosis is important in guiding postnatal follow-up and management, with the goal of amelioration of acquired renal damage. Nursing care focuses on identification of prenatal diagnosis and implementation of postnatal follow-up. Preparation for procedures necessitates parental education and support.
Aslan, A. (2005). Neonatal hydronephrosiss (UPJ obstruction) and multicystic dysplastic kidneys. In L. S. Baskin (Ed.), Handbook of pediatric urology (pp. 123–130). Philadelphia, PA: Lippincott Williams & Wilkins.
Conkar, S., Memmedov, V., & Mir, S. (2016). Outcomes of antenatal hydronephrosis. Annals of Clinical and Laboratory Research, 4(1), 1–5. Retrieved from http://www.aclr.com.es/clinical-research/outcome-of-antenatal-hydronephrosis.pdf
Liu, D. B., Armstrong, W. R., & Maizels, M. (2014). Hydronephrosis: Prenatal and postnatal evaluation and management. Clinics in Perinatology, 41(3), 661–678. doi:10.1016/j.clp.2014.05.013
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