A 2-day-old boy is being evaluated in the nursery. The patient was born at 39 weeks gestation via spontaneous vaginal delivery to a 17-year-old primigravida. The pregnancy was complicated by lack of prenatal care. The delivery was uncomplicated, and the patient had Apgar scores of 9 and 9 at 1 and 5 minutes, respectively. He is formula-feeding well and has stooled twice but has had only a single wet diaper in the first 48 hours. Weight is 2.89 kg (6 lb 6 oz), down 3% from birth weight. Physical examination is unremarkable. Which of the following is the best next step in the evaluation of this patient?

Question

A 2-day-old boy is being evaluated in the nursery.  The patient was born at 39 weeks gestation via spontaneous vaginal delivery to a 17-year-old primigravida.  The pregnancy was complicated by lack of prenatal care.  The delivery was uncomplicated, and the patient had Apgar scores of 9 and 9 at 1 and 5 minutes, respectively.  He is formula-feeding well and has stooled twice but has had only a single wet diaper in the first 48 hours.  Weight is 2.89 kg (6 lb 6 oz), down 3% from birth weight.  Physical examination is unremarkable.  Which of the following is the best next step in the evaluation of this patient?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d726_6ffd_bc81_a5aca14cc14c_MD0003_00 Normal urine output in a neonate is defined as ≥1 void per day of life; this infant has had only a single wet diaper in the first 48 hours of life and therefore has oliguria from neonatal acute kidney injury (AKI). All neonates with oliguria require further evaluation with the following (Choice C): History and physical examination to evaluate for possible risk factors (eg, nephrotoxins, family history, renal anomaly) and volume status (volume overload vs hypovolemia) Renal and bladder ultrasound (RBUS), which documents the number, shape, and size of the kidney(s) and detects vascular abnormalities or congenital anomalies, which are particularly concerning in this patient with no prenatal care An intravenous fluid bolus is often used when hypovolemia (eg, excessive weight loss, dry lips) from prerenal disease is the suspected cause of neonatal oliguria (Choice D). However, establishing normal renal anatomy is required first because in neonates with obstructive uropathy or renal dysplasia, a fluid bolus could lead to volume overload, since the kidneys are unable to remove the excess fluid. In addition, this patient has appropriate weight loss (<10% weight change at day 2) and is formula-feeding well, suggesting a normal volume status. (Choice A) An abdominal radiograph may reveal gross calcification or enlarged kidneys; however, ultrasound is the preferred imaging modality because it provides more detailed anatomy of the entire urinary tract and does not involve radiation. (Choice B) Bladder catheterization may be used to evaluate for and treat urinary retention. However, renal ultrasound should be performed before attempting catheterization, which may cause injury if anatomy is abnormal. (Choice F) A voiding cystourethrogram provides detailed imaging of the distal urinary tract and can elucidate the reasons for pathology seen on renal bladder ultrasound (eg, reflux leading to hydronephrosis). It is performed only if the ultrasound is abnormal because the procedure is invasive and involves radiation. Educational objective: Evaluation of neonatal acute kidney injury includes assessment of risk factors, volume status, and a renal and bladder ultrasound (RBUS). RBUS documents the number, shape, and size of the kidneys and detects vascular abnormalities or congenital anomalies. References: Prenatal diagnosis of congenital renal and urinary tract malformations. (http://www.ncbi.nlm.nih.gov/pubmed/24753862)

A 2-Day-Old Boy Is Being Evaluated in the Nursery