Uric acid crystalluria

Background

• Common cause of red, pink, or orange urine in neonates
  • Occurs mostly in the first week of life, but can occur anytime during infancy
• Parents often confuse this phenomenon with blood, leading to presentation to ED
• Often due to dehydration and relative immaturity of kidney's concentrating abilities
  • Breastfeeding may increase uric acid crystalluria due to its high protein content, which acidifies urine and promotes urate crystallization

Clinical Features

• Reddish, pink, or orange urine noted in diaper
• History of breast-feeding and/or dehydration
• Baby is otherwise well-appearing (suspect alternate diagnoses if has colicky symptoms or febrile)

Representative characteristic of the red/orange urine

Differential Diagnosis

• For female neonates, consider withdrawal bleeding due to lack of maternal hormones
• Consider other serious causes, including obstructive uropathies, porphyria, familial/genetic causes of hyperuricemia
• Consider foods or medications: beets, rifampin, multivitamins, pyridium, etc

Pediatric Hematuria

Macroscopic Hematuria	Transient Microhematuria	Persistent Microhematuria
Blunt abdominal trauma	Strenuous exercise	Benign familial hematuria
Urinary tract infection	Congenital anomalies	Idiopathic hypercalciuria
Nephrolithiasis	Trauma	Immunoglobulin A nephropathy
Infections	Menstruation
Poststreptococcal glomerulonephritis	Bladder catheterization	Alport syndrome
	High fever	Sickle cell trait or anemia
Immunoglobulin A nephropathy		Henoch-Schonlein purpura
Hypercalciuria		Drugs and toxins
Sickle cell disease		Lupus nephritis

Look-Alikes

• Foods or medications
  • For example beets, rifampin, multivitamins, pyridium
• Uric acid crystalluria
• Gastrointestinal bleeding (peds)
• Vaginal bleeding
  • Prepubertal vaginal bleeding
• Other causes of abnormally colored urine

Workup

• Clinical diagnosis
• No further workup indicated, unless alternate causes are suspected

Management

• Reassurance

Disposition

• Discharge

See Also

Additional pearls