Nephrolithiasis in medullary sponge kidney: evaluation of clinical and metabolic features.
OBJECTIVE
Medullary sponge kidney (MSK) is a disorder characterized by tubular dilation of renal collecting ducts and cystic dilation of medullary pyramids that has been associated with stone disease. The significance of nephrolithiasis and the mechanisms by which it occurs are incompletely understood. We describe clinical and metabolic features of nephrolithiasis in a cohort of patients with MSK.


METHODS
Records were reviewed of 56 patients, all with radiographic diagnosis of medullary sponge kidney and data collected pertaining to presentation, stone events and recurrences, stone composition, and metabolic profile to perform a descriptive study with median 3.7 years follow-up.


RESULTS
Nephrolithiasis was confirmed radiographically in 39/56 patients (69.6%). No patient without evidence of nephrolithiasis developed a stone event, whereas 13/39 (33%) of those with nephrolithiasis developed a recurrent stone event. Stones were composed of calcium oxalate monohydrate, calcium oxalate dihydrate, calcium phosphate apatite, and uric acid. Metabolic profile was obtained for 26 of 39 (67%) stone-forming patients demonstrating abnormalities in 22/26 (84.6%). These included hypercalciuria, 58% (15/26); low urine volume, 35% (9/26); hyperuricosuria, 27% (7/26); hypocitraturia, 19% (5/26); elevated urine sodium, 15% (4/26); and hyperoxaluria, 12% (3/26).


CONCLUSIONS
Many patients with MSK have no evidence of nephrolithiasis. Among those who do, recurrence is common, and metabolic profile and composition are varied as in the general stone-forming population.
Department of Urology, Mayo Clinic, Rochester, Minnesota 55905, USA.
E Fred
EF
McPhail
Matthew T
MT
Gettman
David E
DE
Patterson
Laureano J
LJ
Rangel
Amy E
AE
Krambeck
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019343:Citric Acid / Q000652:urine; D004231:Diuresis; D005260:Female; D006801:Humans; D053565:Hypercalciuria / Q000150:complications; D006959:Hyperoxaluria / Q000150:complications; D007669:Kidney Calculi / Q000737:chemistry; D008297:Male; D007691:Medullary Sponge Kidney / Q000150:complications* / Q000000981:diagnostic imaging / Q000378:metabolism; D008875:Middle Aged; D009318:Natriuresis; D053040:Nephrolithiasis / Q000097:blood / Q000000981:diagnostic imaging / Q000209:etiology*; D011859:Radiography; D012008:Recurrence; D012189:Retrospective Studies; D014527:Uric Acid / Q000652:urine; D055815:Young Adult
D014527:Uric Acid; D019343:Citric Acid