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Saudi Journal of Kidney Diseases and Transplantation
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Year : 2021  |  Volume : 32  |  Issue : 6  |  Page : 1809-1812
Medullary Sponge Kidney-Associated Distal Renal Tubular Acidosis Diagnosed in Two Sisters with Variable Degree of Presentation

Department of Renal medicine, Kasr Alainy University Hospitals, Cairo, Egypt

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Date of Web Publication27-Jul-2022

How to cite this article:
Abdelaziz TS. Medullary Sponge Kidney-Associated Distal Renal Tubular Acidosis Diagnosed in Two Sisters with Variable Degree of Presentation. Saudi J Kidney Dis Transpl 2021;32:1809-12

How to cite this URL:
Abdelaziz TS. Medullary Sponge Kidney-Associated Distal Renal Tubular Acidosis Diagnosed in Two Sisters with Variable Degree of Presentation. Saudi J Kidney Dis Transpl [serial online] 2021 [cited 2022 Sep 25];32:1809-12. Available from: https://www.sjkdt.org/text.asp?2021/32/6/1809/352446

   Introduction Top

Medullary sponge kidney (MSK) is a rare congenital abnormality of kidney morphogenesis with an incidence of 1/5000.[1] Most cases are sporadic; however, some familial cases have been reported as well.[2] The pathogenesis is complex and involves both precalyceal duct dilatation and distal nephron defect. Multiple associations have been described including Beckwith-Wiedemann syndrome and congenital hemihypertrophy and horseshoe kidneys.[3],[4]

   Case Reports Top

Case 1

A 16-year-old girl presented with perioral parathesia and tetany. Total and ionized calcium were profoundly reduced and serum magnesium. Blood gases analysis revealed compensated metabolic acidosis. The 24 h urinary calcium was slightly increased. Fasting urinary pH was 5.7 inspite of metabolic acidosis [Table 1]. The patient was admitted to the intensive care unit (ICU) and was given intravenous calcium gluconate and magnesium with improvement of symptoms. Electrocardiography revealed prolonged QT interval. Abdominal ultrasound revealed calcified renal pyramids and was characteristic of MSK as reported by two different ultrasonographers. Since infancy, while she was in Saudi Arabia, she had failure to thrive. She had recurrent renal stones. No other systemic association was noted. She had left ureteric stone for which she had undergone cystoscopy and JJ stent insertion.
Table 1. Biochemical profile during last admission (Case 1).

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During her ICU symptoms markedly improved with the correction of electrolytes. She was then discharged home with the following medications: potassium citrate, sodium bicarbonate oral magnesium citrate and a thiazide diuretic.

Case 2

A 19-year-old girl has been recently admitted with left loin pain and vomiting. She had suffered recurrent renal stones in the past requiring hospitalization. Her biochemical workup showed impaired kidney functions, metabolic acidosis, anemia, hypokalemia, hypocalcemia, and hypomagnesemia, as shown in [Table 2]. Renal ultrasound showed bilateral nephrocalcinosis with the difference in size between both kidneys. The left kidney was small in size (7.2 cm in longest diameter) whereas the left kidney was average in size (longest diameter 9.1 cm) [Figure 1]. Intravenous urography (IVU) was not attempted due to fear of contrast-induced nephropathy.
Table 2. Biochemical profile during last admission (Case 2).

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Figure 1. Ultrasound shows differential sizes between both kidneys (Case 2).

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This case reports the occurrence of MSK in two sisters. Diagnosis was made based on characteristic findings on IVU [Figure 2] in case 1 and characteristic ultrasonographic findings in Case 2. The clinical phenotype is slightly different between both cases. Although both present with nephrocalcinosis, one of the important differences between the two cases was the degree of distal renal tubular acidosis (dRTA). While case 1 had incomplete dRTA, case 2 had overt RTA. It has been previously reported that the incidence of association between overt dRTA and MSKs is 2.9%. In case 2 there was small-sized left kidney which is a reported.
Figure 2. Intravenous urography showing typical features of medullary sponge kidneys.

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The author obtained all appropriate consent forms from the patients and their parents/guardians for the publication of this case report.

   Discussion Top

The presentation in Case 1 started very early in life as the first presentation was failure to thrive. The first renal stone was diagnosed at the age of three years. In spite of earlier presentation, kidney function at the age of 16 was somewhat preserved (serum creatinine = 1.47 mg/dL).

MSK is a disorder of kidney morphogenesis where there is ectasia of the collecting ducts. The pathogenesis is complex and not fully elucidated. Recent insights into the pathogenesis have unveiled a genetic contribution to this abnormality. It has been suggested that MSK is a ciliopathy and there was reported association with polycystic kidney disease. Other associations were congenital hepatic fibrosis. Since hypercalcuria and stone formation are the hallmark features of the disease, the main purpose of the treatment is to decrease stone formation through providing alkali citrate to prevent further stone formation. This case report is interesting in some aspects. First, this article reports MSKs in two sisters, most cases of reported MSK are sporadic. Second, there are variable degrees of presentation; in Case 1: the presentation is with profound hypocalcemia requiring ICU admission while kidney functions are somewhat preserved. In Case 2, the presentation is with more aggressive stone formation and kidney functions are more impaired. Third, in case number 2, the association of MSK with unilateral small-sized kidney is interesting.

   References Top

Fabris A, Anglani F, Lupo A, Gambaro G. Medullary sponge kidney: State of the art. Nephrol Dial Transplant 2013;28:1111-9.  Back to cited text no. 1
Kuiper JJ. Medullary sponge kidney in three generations. N Y State J Med 1971; 71:2665-9.  Back to cited text no. 2
Lambrianides AL, John DR. Medullary sponge disease in horseshoe kidney. Urology 1987; 29:426-7.  Back to cited text no. 3
Gambaro G, Fabris A, Citron L, et al. An unusual association of contralateral congenital small kidney, reduced renal function and hyperparathyroidism in sponge kidney patients: On the track of the molecular basis. Nephrol Dial Transplant 2005;20:1042-7.  Back to cited text no. 4

Correspondence Address:
Tarek Samy Abdelaziz
Department of Renal Medicine, Kasr Alainy University Hospitals, Cairo, Egypt.
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/1319-2442.352446

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  [Figure 1], [Figure 2]

  [Table 1], [Table 2]


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