9.1 Congenital and Acquired Renal and GU Conditions

Congenital and Acquired Renal and GU Conditions

Quick Answer: Hypospadias is a ventral urethral meatus; do not circumcise, because the foreskin is used for later repair. Posterior urethral valves (PUV) are a male bladder-outlet obstruction that can destroy kidneys before birth and present with a palpable bladder, a poor stream, oligohydramnios physiology, and hydronephrosis. Hydronephrosis, autosomal recessive polycystic kidney disease (ARPKD), and bladder exstrophy need imaging, mucosa protection, and staged surgery—not a shrug when both kidneys or the airway are at risk. Ambiguous genitalia overlaps congenital adrenal hyperplasia (CAH) and is a diagnostic emergency for salt-wasting, not a naming contest at the warmer. Acute kidney injury (AKI) is a sudden creatinine rise or oliguria; chronic kidney disease (CKD) is lasting reduced function from dysplasia or obstruction. Urinary tract infection (UTI) in a neonate is treated as possible urosepsis. Peritoneal dialysis (PD) is the usual first dialysis mode in this age group.

Renal and genitourinary conditions sit with endocrine, hematology, gastrointestinal, and integumentary problems in the 20% Endocrine/Heme/GI/Renal/Integumentary Clinical Judgment cluster on the current Neonatal CCRN Test Plan (exams on or after November 12, 2025). Named leaves here are congenital and acquired renal-GU conditions, infections, and surgery. This OpenExamPrep section is independent teaching. It does not claim endorsement by AACN Certification Corporation. Full acid-base and electrolyte arithmetic is chapter 13 (acid-base-fluids); fluids appear here only as they change AKI, obstruction, and dialysis decisions. Mixed practice items are at /practice/ccrn-neonatal.

Neonatal kidney function you must use at the bedside

Nephrogenesis continues into the late second and early third trimester and is largely complete by about 34–36 weeks. A 24-week infant is born with an unfinished nephron census. Even a term kidney is not a small adult kidney: glomerular filtration rate (GFR) at term is often only about 15–30 mL/min/1.73 m² and rises over weeks. Concentrating and acidifying ability are limited. Creatinine on day 1 reflects maternal creatinine, not neonatal GFR. A falling creatinine over the first days is expected. A rising creatinine, or a level that fails to fall after the maternal contribution should have washed out, is AKI language until you prove otherwise.

Most infants void in the first 24 hours; many void in the first 12. After the transitional day, a working target is at least 1 mL/kg/hr of urine, commonly 1–3 mL/kg/hr when perfusion and fluids are adequate. Oliguria is often taught as less than 1 mL/kg/hr (some protocols use 0.5 mL/kg/hr). Anuria is no urine in a drained bladder. A dry diaper in an infant with a kinked catheter is not intrinsic renal failure.

Typical quiet heart rates still matter because renal perfusion follows cardiac output: term resting heart rate often 120–160 beats/min, preterm often 140–180. Mean blood pressure near the gestational age in weeks is a rough first-week floor many units still quote, but the kidney cares about perfusion, not a single MAP slogan. Hypotension, hypoxemia, and nephrotoxins are the everyday NICU AKI triad.

Hypospadias

Hypospadias is incomplete ventral urethral closure. The meatus may sit on the glans, shaft, scrotum, or perineum. Chordee (ventral curvature), a hooded foreskin, and cryptorchidism travel with more severe forms. Isolated distal hypospadias is common and is not an emergency airway problem. The nursing action that fails exams and families is circumcision before urology sees the infant: the prepuce is tissue for urethroplasty, usually performed later in infancy (often 6–18 months in a stable child, not at 12 hours of life).

Severe hypospadias plus bilateral nonpalpable gonads is a difference of sex development (DSD) workup, not a we-will-circ-on-Monday note. Overlap with CAH is real when the infant is a virilized 46,XX fetus. Do not guess sex from a single glance at the warmer.

Posterior urethral valves

PUV are congenital membranous folds in the male posterior urethra. In fetal life they obstruct bladder emptying. The bladder thickens, ureters dilate, and the renal parenchyma can become dysplastic. Severe obstruction plus oligohydramnios produces pulmonary hypoplasia (Potter sequence physiology): the delivery-room problem may be lungs, not the first creatinine.

Bedside clues: male infant, weak or dribbling stream, palpable bladder, urinary ascites, rising creatinine, bilateral hydronephrosis, respiratory failure out of proportion to ordinary RDS. Immediate care is free drainage of the bladder with a well-placed catheter (gentle technique; valves and a tight urethra make catheterization skill-sensitive), cardiorespiratory support, and renal-bladder ultrasound. Voiding cystourethrogram (VCUG) shows a dilated posterior urethra, trabeculated bladder, and often reflux. Surgery is endoscopic valve ablation; a vesicostomy is a temporizing diversion when ablation is not feasible. Lifelong risks include CKD, bladder dysfunction, hypertension, and recurrent UTI.

After obstruction is relieved, post-obstructive diuresis can dump water. Replace ongoing losses so the infant does not swing from overload to hypovolemia. That is fluid care tied to obstruction, not a full sodium lecture.

Hydronephrosis and related dilation

Antenatal hydronephrosis is one of the most common fetal ultrasound findings. Postnatal causes include ureteropelvic junction (UPJ) obstruction, vesicoureteral reflux (VUR), PUV, ureterovesical junction obstruction, and multicystic dysplastic kidney (MCDK). Society for Fetal Urology (SFU) grades describe pelvic dilation and parenchymal thinning. Bilateral hydronephrosis, a solitary functioning kidney, or an abnormal bladder is urgent. Unilateral mild dilation in a well infant is often timed follow-up, not midnight surgery.

Postnatal ultrasound is the first imaging test. Many units delay the first look until after day 2–3 in a well infant because a relatively dehydrated newborn can underestimate dilation—unless the antenatal picture was severe, the infant is oliguric, or infection is suspected, in which case you do not wait for cosmetic timing. VCUG looks for reflux and PUV. A MAG-3 diuretic renogram asks whether a dilated system is obstructed and what split function each kidney contributes. Prophylactic antibiotics after antenatal hydro remain unit- and urology-dependent; know that the question is infection prevention in reflux or obstruction, not a universal OpenExamPrep mandate.

Polycystic kidney disease

ARPKD (often PKHD1) presents with bilaterally enlarged, hyperechoic kidneys, poor corticomedullary distinction, oligohydramnios, pulmonary hypoplasia, and later hypertension and congenital hepatic fibrosis. These infants can need respiratory support and, when kidneys fail, dialysis. Autosomal dominant polycystic kidney disease (ADPKD) usually declares in later childhood or adulthood; a rare neonatal cystic presentation exists, but do not call every bright kidney ADPKD. MCDK is usually unilateral, nonfunctioning, and involutes; it is not ARPKD.

Nursing: blood pressure, respiratory mechanics, family genetics referral, infection, and nutrition. Do not tell families that cystic kidneys are one disease.

Bladder exstrophy

Classic bladder exstrophy is a bladder plate open on the lower abdominal wall, often with epispadias and pelvic diastasis. The mucosa desiccates and bleeds if you treat it like ordinary abdominal skin. Cover with a nonadherent moist dressing or a nonstick barrier per surgical protocol; prevent trauma from diapers and cord clamps; keep the infant warm. Staged reconstruction closes the bladder, repairs the epispadias, and addresses continence; pelvic osteotomy appears in some protocols. Cloacal exstrophy is a more complex OEIS-spectrum problem. Infection, thermoregulation, and honest preoperative teaching are the NICU work.

Ambiguous genitalia and CAH overlap

Do not assign a sex in the delivery room from a hurried look. Document phallic size, meatal position, whether gonads are palpable, pigmentation, and labioscrotal fusion. Palpable gonads usually mean testicular tissue and make virilized CAH (46,XX) less likely. 21-hydroxylase deficiency CAH virilizes 46,XX fetuses and can produce salt-wasting shock with hyponatremia and hyperkalemia in the first weeks—full adrenal teaching is chapter 6. Send 17-hydroxyprogesterone, electrolytes, and karyotype, and involve endocrinology, urology, and genetics. Protect the infant from shame and from irreversible surgery decided in a panic. That is advocacy as well as Clinical Judgment.

AKI versus CKD

AKI is an abrupt decline in function: oliguria, a rising creatinine, fluid overload, or reduced clearance after a hit. NICU hits include perinatal hypoxia, sepsis, nephrotoxins (aminoglycosides, indomethacin or ibuprofen for PDA, acyclovir), abdominal compartment physiology, renal vein thrombosis (hematuria, flank mass, thrombocytopenia in an infant with a catheter or polycythemia), and obstruction.

• Prerenal AKI may improve when you restore circulating volume and perfusion.
• Intrinsic AKI (acute tubular injury, cortical necrosis) does not instantly fix with a bolus.
• Postrenal AKI is obstruction until the bladder and both ureters are known to be open.

Fluids in AKI, without stealing chapter 13: in oliguric AKI, unrestricted maintenance fluid produces pulmonary edema. Many teams limit intake to insensible losses plus measured urine (and other outputs) once volume is restored. In polyuric recovery or post-obstructive diuresis, failing to replace urine produces hypovolemia. Electrolyte recipes, bicarbonate, and detailed anion-gap work stay in the acid-base chapter.

CKD is lasting GFR reduction from dysplasia, PUV, ARPKD, posterior insults that scar, or reflux nephropathy. Growth failure, hypertension, anemia, and bone mineral disease accrue over months. A day-1 creatinine that matches the mother’s is not CKD.

UTI, surgery, imaging, biopsy, and PD intro

Neonatal UTI presents as fever, lethargy, jaundice, poor feeding, vomiting, or shock, not as a chatty dysuria history. Uncircumcised males have a higher early-infancy risk. Obtain urine by catheter or suprapubic aspirate for culture; a bag specimen is contaminated theater. Escherichia coli is the usual pathogen. Treat as possible urosepsis. After a febrile UTI, renal ultrasound looks for obstruction and dysplasia; VCUG is used when ultrasound is abnormal, infection is atypical, or infection recurs—practices vary, but the concept is to find the anatomic reason this neonate infected.

Surgery includes valve ablation, vesicostomy, pyeloplasty (often later), exstrophy closure, hernia repair, and later orchiopexy and hypospadias repair. Preoperative work is NPO, temperature, consent, blood availability, and a secure plan for urine drainage. Postoperative work is urine output, stent or catheter security, hematuria that is expected versus clot obstruction, pain, and wound or stoma integrity. Do not send a hypospadias infant to a circ tray.

Ultrasound is first-line (structure, Doppler for thrombosis). VCUG defines the urethra and reflux. Nuclear MAG-3 defines obstruction versus non-obstructed dilation and split function. Biopsy is uncommon in the NICU: unexplained glomerular disease after imaging, not the first test for hydronephrosis. Bleeding risk is the counseling point.

Peritoneal dialysis is the usual neonatal dialysis introduction: a Tenckhoff-style catheter, fill, dwell, drain. Indications you should recognize: refractory fluid overload, severe hyperkalemia unresponsive to medical steps, uremic complications, and selected inborn-error clearances. Cloudy effluent, fever, and abdominal redness suggest peritonitis. Fill volumes start modestly (often on the order of 10–20 mL/kg and titrate per nephrology—not a number you invent as a standing order). Hemodialysis access and CRRT details belong with chapter 16 advanced therapies. This section only asks you to know PD exists, why neonates often get it first, and what infection looks like.

Worked examples

Example A. A 2-day-old term male has not voided, a lower midline mass, and a weak stream. Ultrasound shows a thick bladder and bilateral hydroureteronephrosis. This is PUV until proven otherwise. Drain the bladder, support breathing, obtain VCUG, call urology. It is not wait-until-day-3 after a palpable bladder.

Example B. A 26-week infant receives indomethacin for a PDA. Urine output falls to 0.4 mL/kg/hr and creatinine rises from 0.6 to 1.1 mg/dL. This is AKI. Hold the nephrotoxin, restore perfusion, restrict fluids if the infant is already volume loaded, and look for obstruction or abdominal compartment issues. It is not preterm-creatinine-always-climbs.

Example C. A nurse opens a circumcision tray for an infant with a proximal hypospadias. Stop. The foreskin is reconstructive tissue. If gonads are not palpable, add a DSD/CAH pathway rather than a cosmetic circ.

Exam traps: treating day-1 maternal creatinine as CKD; bag urine cultures; circumcising hypospadias; delaying bladder drainage in a male with a palpable bladder; writing a full CRRT prescription in this chapter; dumping potassium and bicarbonate algorithms here instead of chapter 13; describing this OpenExamPrep section as official AACN procedure certification. Independent practice items: /practice/ccrn-neonatal. Pediatric renal pages at /study-guides/ccrn-pediatric address older children.