Saudi Journal of Kidney Diseases and Transplantation

CASE REPORT
Year
: 2008  |  Volume : 19  |  Issue : 4  |  Page : 619--623

Hyperuricosuria, an Often Overlooked Cause of Recurrent Oliguria in Children


Kamal Akl 
 Department of Pediatrics, Jordan University Hospital, Amman, Jordan

Correspondence Address:
Kamal Akl
Department of Pediatrics, Jordan University Hospital, P.O. Box 831373, Amman 11183
Jordan

Abstract

The association of oliguria with hyperuricosuria is often overlooked. Herein, we report an infant who since the age of five months had recurrent oliguria secondary to hyperuricosuria documented several times in the hospital. The decreased urine output co­incided with the presence of increased excretion of uric acid, which fluctuated within 24 hours as well as every few weeks. The child responded to treatment with increase in the fluid fluid intake along with the xanthine oxidase inhibitor, allopurinol. Being alert for hyperuricosuria in cases of oliguria, especially if there is history of gout or stones, may avoid performing many unnecessary investigations



How to cite this article:
Akl K. Hyperuricosuria, an Often Overlooked Cause of Recurrent Oliguria in Children.Saudi J Kidney Dis Transpl 2008;19:619-623


How to cite this URL:
Akl K. Hyperuricosuria, an Often Overlooked Cause of Recurrent Oliguria in Children. Saudi J Kidney Dis Transpl [serial online] 2008 [cited 2020 Feb 19 ];19:619-623
Available from: http://www.sjkdt.org/text.asp?2008/19/4/619/41324


Full Text

 Introduction



The association of oliguria with hyperuri­cosuria is often overlooked. In 2006, seven patients with idiopathic hyperuricosuria and oliguria were seen in the pediatric nephrology service at the Jordan University Hospital. Herein, we report one child that had oligu­ria documented several times in the hospital.

 Case Report



The patient was born after a smooth full­term pregnancy and normal vaginal deli­very. Birth weight was 2,700 grams. Her parents were not consanguinous. At the age of four months, the patient presented to the Jordan University Hospital with a one­month history of decreased urine output des­pite adequate feedings. On physical exami­nation at five months, the head circum­ference was 41 cm (25 th percentile), length 56 cm (50 th percentile), and weight was 5,300 grams (25 th percentile).

Laboratory investigations showed the fol­lowing: serum creatinine, 8.84-27.4 µmol/L (normal is 17.68-35.36 µmol/L), uric acid 77.32-285.5 µmol/L (normal is 142.75­380.67 µmol/L), urine analysis was nega­tive for protein, red and white blood cells and the urine culture was negative. Several spot urine samples and 24-hour urine col­lections for uric acid were done. Spot urine uric acid concentration corrected for glome­rular filtration rate was 2.54 mg/dl (consi­dered abnormal if > 0.53 mg/dl). 24-hour urine uric acid excretion on two occasions was 15084.7 µmol/kg and 30169.4 µmol/kg. The normal value for age is [1] conditions that lead to hyperuricemia and concomitant hyperurico­suria include malignancies such as leuke­mia and lymphoma, where there is increased purine catabolism. Tumour lysis syndrome may occur before or after chemotherapy. Hereditary disorders of purine metabolism with complete deficiency of hypoxanthine phosphoribosyl transferase (HPRT) result in the Lesch Nyhan syndrome, which consists of hyperuricemia, mental retardation, cho­reoathetosis, and self mutilation. [2] The en­zyme deficiency may be partial, when it is not associated with neurologic manifesta­tions. [3] Other enzyme deficiencies include adenine phosphoribosyl transferase (APRT) and genetic overproduction of purine as seen in patients with phosphoribosyl pyro­phosphate synthetase overactivity. [4]

Cystic fibrosis, certain drugs such as cy­closporine and tacrolimus, sickle cell di­sease, congenital heart disease with poly­cythemia and neonates may have associa­ted hyperuricosuria.

During infancy and childhood, there is increased uric acid production. [5],[6] Fractio­nal excretion of uric acid in early child­hood is higher than that in adults. [7] Before puberty, hyperuricosuria rather than hyper­uricemia may be the only clue to purine overproduction due to the high uric acid clearance. [4] When hyperuricosuria is secon­dary to hyperuricemia, the renal manifesta­tions may include acute uric acid nephro­pathy, chronic uric acid nephropathy, and nephrolithiasis. [8] Our patient had hyperuri­cosuria without hyperuricemia. The main manifestation was recurrent episodes of oliguria, which resolved with hydration, and allopurinol. The latter is a xanthine oxidase inhibitor that results in decreased serum and urinary uric acid by blocking the con­version of hypoxanthine and xanthine to uric acid. In a large series of hyperuri­cosuria in children, La Manna and asso­ciates mentioned a spectrum of signs and symptoms in 102 children with idiopathic hyperuricosuria. These included abdominal or flank pain, dysuria, gross or microsco­pic hematuria, and passage of gravel. Normal urinalysis was found in 15 patients. How­ever, there was no mention of oliguria. [9] Acute uric acid nephropathy may occur in the newborn, especially in the first few days of life due to breakdown of hema­poietic cells, or secondary to HPRT enzyme deficiency. [10]

The entity of neonatal transient renal failure with renal medullary hyperechoge­nicity is believed to be secondary to over production of uric acid. [11],[12],[13],[14] Most of the reported neonatal cases had associated hy­peruricemia. [15] Complete or partial HPRT deficiency may cause acute renal failure in infancy. [1] Batch et al, described a three month old infant with acute renal failure secondary to over-production of urate. The infant was found to have excessive urinary excretion of uric acid and partial deficien­cy of HPRT and responded to allopurinol and the renal failure resolved. [17] Our patient responded to daily orange juice because of the presence of citrate, which provided an alkali load. Odvina found out that amongst the citrus fruits, only orange juice preven­ted crystallization of calcium oxalate and uric acid. [18] One interesting aspect of our patient was the diurnal variation in uric acid excretion which was observed in the hospital and reflected as recurrent oliguria within a period of 24-hours in addition to that observed every few days to weeks. It is known that uric acid excretion may be intermittent as demonstrated in humans, [19],[20] and in Cebus monkeys where the highest plasma uric acid was before bedtime at night, and the lowest, early in the morning. [21] The 24-hour urine excretion of uric acid in our patient was always highly elevated against the random spot specimens, which were sometimes normal. Because of the circadian rhythm, random urine uric acid testing may not be accurate. [22] Furthermore, in patients with normal enzyme activity, uric acid to creatinine ratios in random urine samples do not correlate with 24-hour urine collections. [23],[24] Spot samples correc­ted for creatinine clearance (mg/dL GFR) are more accurate than the uric acid to creatinine ratio. [25],[26]

The cause of hyperuricosuria in our pa­tient remains unknown. It unlikely that she has familial juvenile hyperuricemic nephro­pathy because the serum uric acid was normal. [27] HPRT deficiency is usually asso­ciated with an elevated serum uric acid. In adenine phosphoribosyltransferase deficien­cy, the serum and urine uric acid is not elevated, but patients may present with acute renal failure. [28] Our patient could have an isolated defect in postsecretory reabsorption of uric acid, or idiopathic hyperuricosuria. Unfortunately, enzyme assays were not avai­lable. La Manna and associates emphasize the importance of family history of gout or stones in cases of hyperuricosuria. [29]

 Conclusion



A child with recurrent oliguria secondary to hyperuricosuria is presented. One should be on the lookout for such cases especially if there is family history of gout or uric acid stones. This will avoid doing unnece­ssary investigations.[30]

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