Wm. Lane M. Robson, MD

A mother brought in her 3-week-old son on the day she discovered a reddish urine stain in the baby's diaper. There was no stool in the diaper. The boy had been circumcised on the second day of life, and the mother was concerned that her son might have experienced a complication of the procedure.

The infant was delivered vaginally at term after an uncomplicated pregnancy. His Apgar scores were 8 and 9. He weighed 7 lb 5 oz at birth and was 20 inches long. The baby was discharged along with his mother on the day he was circumcised. He was fed exclusively with breast milk and had been gaining weight satisfactorily.

Physicalexamination revealed a healthy- appearing infant in no distress with a well-healed circumcision. The urethral meatus looked elliptical and of normal caliber and was not inflamed. The kidneys and bladder were normal to palpation. The systolic blood pressure in the right upper arm while the baby was supine and quiet was 80 mm Hg. The peripheral perfusion was normal. There were no signs of dehydration. Results of the physical examination were otherwise normal.

 Prescribe an antibiotic for presumedurinary tract infection.

 Obtain a urine specimen for dipstick andmicroscopic urinalysis.

 Order ultrasonography of the kidneys andbladder.

The differential diagnosis of a reddish stain in the diaper includes hematuria, uric acid crystals, beeturia, some inborn errors of metabolism, ingestion of a food dye that is excreted in the urine, red diaper syndrome caused by 

 in the stool, and Munchausen syndrome by proxy.

We recommend obtaining a fresh urine specimen for dipstick and microscopic analysis.

We do not recommend treatment with an antibiotic unless a urinary tract infection has been confirmed. Nor do we recommend ultrasonography of the urinary tract or a voiding cystourethrogram unless hematuria is confirmed.

With specific questioning, the mother confirms that neither she nor her baby has ingested beets,berries, or any foods with known red food coloring. The mother has not observed any discomfort associated with wetting the diaper or colic. She has observed her son's urine stream on 2 occasions--one in the bath and the other during a routine diaper change. The urine emerged without straining or discomfort, and the stream was strong, straight, and continuous, with a good arc.

The urine dipstick revealed a pH of 6 and was negative for blood. Not enough urine was obtained to centrifuge or to perform a microscopic analysis.

 Ask the mother to bring in the diaper withthe reddish stain. If it has been discarded,ask her to bring in any future diaper with areddish stain.

 Ask the mother to bring in a first-morningurine specimen for dipstick and microscopicanalysis.

 Ask the mother to observe the baby forsigns of colic.

 Ask the mother to ask the grandparentswhether there is any family history of gout,kidney stones, or metabolic or neurologicproblems.

The mother returns the following day with the original diaper and a urine specimen obtained overnight. At about 4 am, the mother changed the baby's diaper, put on a urine bag, and then breast-fed the baby. The urine bag was full when the mother checked the diaper 3 hours later. The mother placed the urine specimen in a container in the refrigerator until she left for the clinic.

The reddish-stained diaper from the previous morning was still heavy with urine in the absorbent matrix. However, the inside surface of the diaper had dried to reveal a fine layer of a rust-colored powder.

The first-morning urine had a pH of 5 and a specific gravity of 1.02, and was negative by dipstick for blood. The centrifuged urine had pinkish orange sediment at the bottom of the tube. The microscopic urine specimen revealed numerous uric acid crystals but no blood.

The mother advised that the baby had not experienced any colicky discomfort and that there was no family history of gout, kidney stones, or metabolic or neurologic problems.

The reddish stain in the diaper is caused by uric acid crystals. The excretion of uric acid in urine is high at birth and falls during childhood until adolescence, when adult levels are observed. Uric acid excretion is especially high during early infancy. The solubility of uric acid is about 12 mmol/L at a urine pH of 8, but only 1 mmol/L at a pH of 5. As such, acid urine favors precipitation of uric acid crystals. The high protein content of breast milk favors acid urine.

Although uric acid crystals are commonly observed in the diapers of infants and are not usually a concern, some rare and more serious disorders of purine metabolism might also present in this fashion. A variety of inherited enzyme deficiencies and renal tubular problems can lead to hyperuricosuria. Deficiency of hypoxanthine- guanine phosphoribosyltransferase is the most commonly reported problemand can present along a clinical spectrum that includes Lesch-Nyhan syndrome at the severe end. Crystalluria with dysuria, stone formation with colicky pain, acute renal failure from urate nephropathy, and severe neurologic impairment are possible problems in children with Lesch-Nyhan syndrome.

Investigations are generally not required for otherwise well infants with uric acid crystals in the urine. However, blood tests for levels of serum uric acid, creatinine, and electrolytes, as well as an ultrasonogram of the kidneys and bladder, should be considered in those infants with uric acid crystals in the diaper who have a family history of gout, kidney stones, or metabolic problems during infancy; a history of colic or dysuria; or evidence of red blood cells in the urine in addition to uric acid crystals.

The problem is self-limited in otherwise well infants who have uric acid crystals in the urine--and no treatment is usually necessary. However, uric acid crystalluria can be associated with dysuria. Maintenance of good hydration will minimize this possibility.

 Cameron JS, Moro F, Simmonds HA. Gout, uric acid and purine metabolism in paediatric nephrology. 

 Grivna M, Prusa R, Janda J. Urinary uric acid excretion in healthy male infants. 

 Stapleton FB, Linshaw MA, Hassanein K, Gruskin AB. Uric acid excretion in normal children. 

Articles

Pediatric Urology Clinics: Reddish Urine Stain in the Diaper of a 3-Week-Old Boy

Dysuria refers to painful micturition. When a child presents with dysuria, it is important to clarify the location of the discomfort. Such discomfort is usually localized to the urethra, but suprapubic, groin, and flank pain might also be experienced with voiding--either as an isolated symptom or in conjunction with urethral dysuria. The differential diagnosis of dysuria varies according to the location of the pain. 

The differential diagnosis of urethral dysuria in a circumcised elementary school-aged boy includes:

•Crystalluria (most commonly, calcium crystals).

•Meatal stenosis and other causes of urethral obstruction.

In this boy, there is no historical or clinical evidence of inflammation of the glans or meatus to suggest a diagnosis of meatitis. The dipstick urine test did not reveal the presence of white blood cells (WBCs) or bacteria, which makes an infectious cystourethritis or urethritis less likely. There is no history of trauma to the urethra. Calcium crystalluria is a reported cause of urethral dysuria that can also manifest with RBCs in the urine; with calcium crystalluria, urinary frequency is also common and there might be a family history of kidney stones. The circular and relatively small appearance of the urethral meatus suggests--but does not confirm--the possibility of meatal stenosis. There is no history of a urinary stream abnormality to suggest urethral obstruction, but specific questions were not asked to clarify this possibility. 

We recommend observation while the boy voids and examination of the fresh urine specimen under a microscope. 

We do not recommend treatment with an antibiotic unless a UTI has been confirmed. Urethral obstruction and calcium lithiasis with calcium crystalluria might be revealed with ultrasonography and a voiding cystourethrogram, but the presentation is not specific enough for these diagnoses to justify an invasive diagnostic imaging study at this stage in the investigation. A random urine specimen for evaluation of calcium and creatinine levels might help determine whether hypercalciuria is present; this is not an invasive test, but we would not recommend it until UTI--which is the most common cause of urethral dysuria--has been ruled out.

With specific questioning, the boy relates that the discomfort with voiding is localized only to the tip of his penis. He denies any discomfort in the suprapubic, groin, or flank areas. Also, with specific questioning, the boy relates that the discomfort occurs only several times a week, and is usually limited to an isolated void. The discomfort is often noted with his first morning void, and he acknowledges that he does not always void before going to bed. The discomfort is also often noted when he voids with an exceptionally full bladder--such as after he has ingested a full can of soda. Specific questions about his urinary stream reveal that he does not need to wait or push to initiate voiding. He acknowledges that his urinary stream is deflected upward such that he needs to push his penis down to direct the urine into the toilet. He does not know whether his stream is thin or thick but is confident that the stream is strong and continuous to the end. 

The boy allowed observation of his urinary stream with voiding. He did not need to wait or push to initiate voiding. The boy pushed the head of his penis down such that the upwardly deflected stream was directed into the center of the toilet. The stream was strong and continuous but thinner than normal. 

The fresh urine was centrifuged and the spun specimen revealed 1 to 2 non-dysmorphic RBCs per high-power field. No WBCs, bacteria, or crystals were evident.

In this boy, discomfort with voiding is likely the result of the passage of a large volume of urine from a full or an overly distended bladder across the relative obstruction caused by mild to moderate meatal stenosis. 

Episodes of dysuria might be minimized by avoiding an overly distended bladder with the following measures:

•Voiding regularly during the day and not holding the urine until the last minute.

•Voiding just before bedtime (to avoid an overly distended bladder first thing in the morning).

The average bladder capacity of a 6-year-old is about 8 oz. The child should be instructed to void within an hour of ingesting a full glass or can of soda or any other beverage. When the child voids, he should take his time--and not rush or push. His pants or zipper should be pulled down such that the penis is not bent during voiding. 

Definitive treatment requires a meatotomy, which can be performed by a pediatric urologist in the office in an awake child after application of a topical anesthetic. Meatal stenosis, which develops almost exclusively in circumcised boys, is presumed to result from recurrent episodes of meatitis. The meatus of the circumcised penis is subject to recurrent traumatic inflammation as the unprotected glans is compressed against synthetic or cloth diaper material and is subject to chemical inflammation from ammonia and other substances in the urine. Meatal stenosis might also occur subsequent to hypospadias repair or prolonged urethral catheterization, or after other causes of trauma to the urethral meatus. 

Classically, meatal stenosis presents with a small circular meatal opening rather than the normal elliptic shape. A web often develops over the dorsal aspect of the meatus and results in a relative obstruction to flow and a urinary stream that is deflected upward. The stream is often narrow and of high velocity. With more severe degrees of obstruction, the child might need to push to begin voiding. Occasionally, the forceful micturition causes the web to tear, with a resultant drop of blood after micturition. Meatal stenosis can be prevented by regular application of a petroleum ointment to the meatus for several weeks after circumcision.	*

m Persad R, Sharma S, McTavish J, et al. Clinical presentation and pathophysiology of meatal stenosis following circumcision. 

 1995;75:91-93. m Upadhyay V, Hammodat HM, Pease PW. Post circumcision meatal stenosis: 12 years' experience. 

Author | Wm. Lane M. Robson, MD

Articles

Pediatric Urology Clinics: Reddish Urine Stain in the Diaper of a 3-Week-Old Boy

Pediatric Urology Clinics: Dysuria in an Elementary School-Aged Boy