Medullary sponge kidney.

PURPOSE OF REVIEW: After it was first described in 1939, medullary sponge kidney (MSK) received relatively little attention. This was because it was believed to have a low prevalence and because it was considered a benign condition. Studies in recent years have been changing these convictions however, hence the present review. RECENT FINDINGS: Insight has been obtained on the genetic basis of this disease, supporting the hypothesis that MSK is due to a disruption at the 'ureteric bud-metanephric mesenchyme' interface. This explains why so many tubular defects coexist in this disease, and particularly a distal tubular acidification defect of which the highly prevalent metabolic bone disease is one very important consequence. In addition to the typical clinical phenotype of recurrent stone disease, other clinical profiles have now been recognized, that is, an indolent, almost asymptomatic MSK, and a rare form characterized by intractable, excruciating pain. SUMMARY: Findings suggest the need for a more comprehensive clinical characterization of MSK patients. The genetic grounds for the condition warrant further investigation, and reliable methods are needed to diagnose MSK.

An unusual association of contralateral congenital small kidney, reduced renal function and hyperparathyroidism in sponge kidney patients: on the track of the molecular basis.

Of unknown pathogenesis, sponge kidney (SK) is variably associated with nephrocalcinosis, stones, nephronic tubule dysfunctions and precalyceal duct cysts. Amongst 72 unrelated renal SK patients with renal stone disease, we detected one with unilateral bifid renal pelvis and six with unilateral small kidneys (longitudinal diameter difference >15%). Secondary causes of small kidney were excluded. Of the seven cases, four had reduced renal function (67 vs 7% in the entire cohort), and three developed hyperparathyroidism during follow-up (43 vs 4%). The pathogenesis of SK ought to explain why anatomical structures of different embryological origin are involved (the precalyceal and collecting ducts and the nephron) and why there is frequent association with hyperparathyroidism. In embryogenesis, the metanephric blastema synthesizes the chemotactic glial-derived neurotrophic factor (GDNF) to prompt the ureteric bud to branch off from Wolff's mesonephric duct, and to approach and invade the blastema. The bud's tip expresses the GDNF receptor (RET). RET-GDNF binding is crucial not only for the correct formation of ureters and collecting ducts (both of Wolffian origin), but also for nephrogenesis. We advance the hypothesis that SK results from a disruption in the ureteric bud-metanephric blastema interface, possibly due to one or more mutations or polymorphisms of RET or GDNF genes. This would explain: the concurrent alterations in precalyceal ducts and the functional defects in the nephron, the occasional association with size and the functional asymmetry between the two kidneys, some degree of renal dysplasia causing the reduction in the glomerular filtration rate and (given the role of RET in parathyroid cell proliferation) the association with hyperparathyroidism.

[Cacchi and Ricci's disease. Radiology, epidemiology and biology]. / Maladie de Cacchi et Ricci. Remarques radiologiques, épidémiologiques et biologiques.

OBJECTIVES: Medullary sponge kidney corresponds to the precaliceal dilatation of renal tubules. The purpose of this article is to draw attention to some of the radiological, epidemiological and laboratory features of this disease. MATERIAL AND METHOD: 500 cases of radiopaque renal stones, corresponding to 310 men and 190 women, were reviewed. One or several urographies, early urographic films, and blood calcium phosphate and 24-hour urinary calcium phosphate and oxalate assessments were available for all subjects. We have added to this series an identical study on 100 cases of stones in North African subjects. RESULTS: From a radiographic point of view, this study shows the value of early urography films, performed between the 2nd and 4th minutes after intravenous injection of iodinated contrast agent, which visualize abnormal opacification of the renal pyramids, before or at the same time as that of the bases of the calices. A radiological sign, not reported in the medical literature, is a clear border between abnormal opacification of the papillae and that of the calices, observed in one or several papillocaliceal zones, which facilitates the diagnosis of medullary sponge kidney. In this series of 500 cases of renal stones, the radiological diagnosis of medullary sponge kidney was established in 103 cases: 20.6%. The distribution varies according to sex, 54 out of 310 (12.59%) in men, 53 out of 190 (27.89%) in women; difference p < 0.001. We found only 3 cases of medullary sponge kidney in the series of 100 cases of radiopaque stones in North African subjects. In terms of laboratory parameters, 24-hour urine tests showed hypercalciuria in 61 out of 103 cases (59.22%), or hyperoxaluria in 66 out of 103 cases (64.08%), while 41 out of 103 cases (39.81%) presented both disorders. Urinary calcium oxalate assessments were normal in 20 out of 103 cases (19.42%). Hyperparathyroidism was never detected in combination with medullary sponge kidney. CONCLUSION: This study shows the value of early urography films for the diagnosis of medullary sponge kidney and demonstrates a useful diagnostic radiological sign: a clear border between abnormal urographic opacification of the papillae and calices. It shows the much higher frequency of medullary sponge kidney in patients with radiopaque stones, with a higher rate in women than in men, and a low frequency in North African subjects, that needs to be confirmed. This study also emphasizes the frequency of hypercalciuria and especially hyperoxaluria, and even the combination of these two disorders in medullary sponge kidney.

Medullary sponge kidney associated with congenital hemihypertrophy.

Medullary sponge kidney is a developmental disorder characterized by ectatic and cystic malformation of the collecting ducts and tubules. Clinical manifestations include urinary tract infections, renal stones, and hematuria. It can be associated with other developmental disorders. A case of medullary sponge kidney associated with congenital hemihypertrophy, complicated by nephrocalcinosis and nephrolithiasis, is reported here.

[Prevalence of medullary sponge kidney in patients with and without nephrolithiasis]. / Prävalenz der Markschwammniere bei Patienten mit und ohne Nierensteinleiden.

Reports on the prevalence of medullary sponge kidneys have given conflicting results. The present work is aimed at defining the prevalence of this abnormality in renal stone formers compared with a non-stone-forming control population by strict radiological criteria. Three separate studies have been carried out: the retrospective analysis of 191 intravenous urographies, which had been performed in 1988; the respective prospective analysis of 104 consecutive intravenous urographies and of 149 consecutive urographies, which had been performed at the end of intravenous digitalized subtraction renal angiographies. The 444 patients were classified according to presence or absence of nephrolithiasis. After exclusion of 70 patients (16%) of which the X-ray didn't fulfill the quality criteria, urographies were classified as 'medullary sponge kidneys', 'papillary blush' or 'negative' according to the radiological aspect of the papillae. Diagnosis of medullary sponge kidneys was based on presence of at least three linear or round papillary opacities seen in at least on papilla even of one kidney on late films (at least ten minutes after injection of contrast medium), taken without ureteral obstruction or abdominal compression. Overall results reveal that prevalence of a medullary sponge kidney in renal stone formers (8.5%) is significantly (p < 0.01) higher than in the control population (1.5%) and higher than what has been generally reported. Results of the retrospective and of both prospective analysis did not significantly differ. The best diagnostic tool to unmask medullary sponge kidneys remains urography.