Pediatric UTI, Hydronephrosis & Congenital GU Anomalies
From catheterized urine to orchiopexy: what to test, image, and fix in a child's urinary tract.
Febrile UTI in infants and young children
Why it matters. UTI is the most common serious bacterial infection in febrile infants, and before age 2 fever may be its only sign. Risk is higher in girls, uncircumcised male infants, and children with VUR, urinary anomalies, or bladder-bowel dysfunction (constipation, infrequent voiding).
Getting the specimen. In a child who is not toilet-trained, urine for culture must come from transurethral catheterization or suprapubic aspiration. Bag specimens are so often contaminated that a positive result proves nothing and must be confirmed on a catheterized sample; a negative bag urinalysis only helps rule UTI out. Toilet-trained children can give a clean-catch midstream sample.
Diagnosis. UTI requires an abnormal urinalysis (leukocyte esterase, nitrite, pyuria, or bacteriuria) plus ≥50,000 CFU/mL of a single uropathogen on a catheterized specimen. A negative nitrite does not exclude infection in infants, who void too often for bacteria to convert nitrate. E. coli causes about 80%; others are Klebsiella, Proteus (uncircumcised boys), Enterococcus, and Pseudomonas (anomalies, instrumentation).
Treatment. A well-appearing child who keeps fluids down gets an oral cephalosporin (cephalexin, cefdinir, cefixime) adjusted to sensitivities. Parenteral therapy is for ill appearance, vomiting, dehydration, or age <2 months; young infants also need ampicillin (for example, ampicillin plus gentamicin) because cephalosporins miss Enterococcus, and febrile neonates need a full sepsis evaluation. Total duration is 7–14 days; no improvement after 48 hours calls for an ultrasound to look for abscess or obstruction.
Nitrofurantoin reaches therapeutic levels only in bladder urine, not renal tissue or blood: never use it for febrile UTI or pyelonephritis.
Imaging and vesicoureteral reflux
Who gets imaged. Every child aged 2–24 months with a first febrile UTI gets a renal-bladder ultrasound. VCUG is reserved for an abnormal ultrasound or a recurrent febrile UTI; with a normal ultrasound, the plan is prompt urine testing during future fevers.
| Test | What it shows | When to order |
|---|---|---|
| Renal-bladder ultrasound | Hydronephrosis, duplication, bladder wall thickening, scarring, abscess | First febrile UTI at 2–24 months; follow-up of prenatal hydronephrosis |
| Voiding cystourethrogram | Reflux and its grade; posterior urethral valves | Abnormal ultrasound, recurrent febrile UTI, suspected valves |
| Diuretic renal scan (MAG3 + furosemide) | Drainage (obstruction) and split renal function | Suspected UPJ obstruction or obstructive megaureter |
| DMSA scan | Cortical defects: pyelonephritis, later scarring | Selected cases, months after infection |
Mechanism. The ureter normally tunnels obliquely through the bladder wall so that bladder filling compresses it like a flap-valve. In primary VUR the intravesical tunnel is too short; secondary VUR results from high bladder pressure (posterior urethral valves, neurogenic bladder). VCUG grades reflux I–V: I, into an undilated ureter; II, up to an undilated pelvis and calyces; III, mild–moderate dilation with mild calyceal blunting; IV, moderate dilation with loss of sharp calyceal angles; V, gross dilation and tortuosity with loss of papillary impressions. Grades I–II usually resolve as the tunnel lengthens with growth.
Management. The aim is to prevent pyelonephritic scarring (reflux nephropathy), which causes hypertension, proteinuria, and CKD. Options: surveillance with prompt treatment of every febrile UTI, continuous prophylaxis (TMP-SMX or nitrofurantoin; TMP-SMX is avoided before 2 months), and treatment of bladder-bowel dysfunction. In the RIVUR trial, prophylaxis halved recurrent UTIs but did not reduce scarring. Surgery (ureteral reimplantation or endoscopic subureteral injection) is for high-grade reflux with breakthrough febrile UTIs or new scarring.
Prenatal hydronephrosis and obstructive anomalies
Approach. Most prenatally detected pelvic dilation is transient. Postnatal ultrasound is done after 48 hours of life, because early neonatal oliguria underestimates dilation, but at once for a boy with bilateral hydronephrosis or a distended bladder. Hydronephrosis and multicystic dysplastic kidney are the leading causes of an abdominal mass in the newborn.
| Cause | Key features | Management |
|---|---|---|
| UPJ obstruction | Most common obstructive cause; intrinsic narrowing or crossing vessel; later, flank pain and vomiting after heavy fluid intake | Diuretic renal scan; pyeloplasty for declining function or symptoms |
| Vesicoureteral reflux | Dilation may vary with voiding | VCUG; surveillance ± prophylaxis |
| Primary megaureter | Dilated ureter above an aperistaltic distal segment | Most resolve |
| Duplex system | Upper pole obstructs (ectopic ureter, ureterocele); lower pole refluxes | VCUG; endoscopic incision or reconstruction |
| Posterior urethral valves | Boy; bilateral hydronephrosis, thick bladder, oligohydramnios | Catheter, VCUG, valve ablation |
| Multicystic dysplastic kidney | Mimic: noncommunicating cysts, no function | Observe; usually involutes |
Duplex kidneys. By the Weigert-Meyer rule, the upper-pole ureter inserts lower and more medially and tends to obstruct, often ending in a ureterocele; the lower-pole ureter inserts laterally with a short tunnel and refluxes. A girl who voids normally but is constantly damp has an ectopic ureter draining into the vagina or distal urethra beyond the sphincter.
Posterior urethral valves. These membranes are the most common cause of bladder outlet obstruction in male newborns. Prenatally: bilateral hydroureteronephrosis, a thick-walled bladder with a dilated posterior urethra (keyhole sign), and oligohydramnios → Potter sequence (pulmonary hypoplasia, the main cause of neonatal death; flat facies; limb deformities). After birth: weak dribbling stream, palpable bladder, UTI, urinary ascites, failure to thrive.
- DecompressSmall urethral catheter at once; watch fluids and electrolytes as the obstruction is relieved.
- ConfirmVCUG: dilated, elongated posterior urethra, trabeculated bladder, often VUR.
- AblateEndoscopic valve ablation; vesicostomy if the urethra is too small.
- Follow for lifeMany progress to CKD despite relief.
Hypospadias and the foreskin
Hypospadias. The meatus opens on the ventral penis anywhere from glans to perineum, with a dorsal hooded foreskin and often ventral curvature (chordee). Circumcision is deferred because the foreskin is used for repair at 6–18 months. Isolated distal hypospadias needs no workup, but proximal hypospadias with an undescended testis warrants a disorder-of-sex-development evaluation (karyotype, electrolytes, 17-hydroxyprogesterone). Epispadias, a dorsal meatus, is associated with bladder exstrophy.
Foreskin and meatus. A nonretractile foreskin with preputial adhesions is physiologic through early childhood, often until about age 5 or later, and should never be forced back; scarred pathologic phimosis gets topical steroid or circumcision. Balanoposthitis (red, swollen glans and foreskin) is managed with hygiene and topical therapy. Meatal stenosis in circumcised boys gives a thin, upward-deflected stream and dysuria and is fixed by meatotomy.
Paraphimosis, a retracted foreskin trapped behind a swelling glans, is an emergency: compress the edema and reduce manually, with a dorsal slit if that fails.
Testes and groin: cryptorchidism, hydrocele, hernia
Cryptorchidism. About 3% of term and up to 30% of preterm boys have an undescended testis. Most that will descend do so by 6 months (corrected age); after that, refer for orchiopexy by 18 months to protect fertility, allow examination, and lower torsion risk. Testicular cancer risk (most often seminoma) falls but stays above baseline. Ultrasound is not needed and hormones are not recommended; a nonpalpable testis gets exam under anesthesia and diagnostic laparoscopy.
Bilateral nonpalpable testes in a phenotypic male newborn may mean a virilized 46,XX infant with 21-hydroxylase deficiency: obtain a karyotype and 17-hydroxyprogesterone with electrolytes urgently, before a salt-wasting crisis. Hypospadias with any nonpalpable testis triggers the same evaluation.
Retractile testis. A brisk cremasteric reflex pulls a normal testis upward. If it reaches the bottom of the scrotum and stays after release, no surgery is needed, but it is rechecked yearly because some ascend.
Hydrocele vs hernia. Both arise from a patent processus vaginalis. A hydrocele transilluminates and has a normal cord palpable above it; noncommunicating hydroceles usually resolve by 12 months, while a communicating hydrocele fluctuates (larger by evening) and is repaired if it persists beyond 12–18 months. An indirect inguinal hernia is a reducible bulge extending up the canal, most common in boys and preterm infants; it gets prompt elective repair because incarceration risk peaks in infancy. Incarceration (tender, irreducible, vomiting) needs urgent reduction and surgery.
An inguinal hernia in a phenotypic girl should prompt consideration of complete androgen insensitivity, with a testis in the sac.