Table 2 Main differential diagnosis between medullary sponge kidney and other cystic kidney diseases
From: Ultrasound to address medullary sponge kidney: a retrospective study
Diseases | Bilateral/Unilateral | Kidney size | Ultrasound appearance of kidneys and cysts | Hereditary/acquired | Genetics | Clinical findings |
|---|---|---|---|---|---|---|
Autosomal dominant polycystic kidney disease (ADPKD) [15, 18, 24, 25] | Bilateral | Increased | Presence of multiple, variably sized, cortical and medullary cysts, that increase in number and size with time | Hereditary (autosomal dominant) | PKD1, PKD2, GANAB | Chronic kidney disease typically occurs in adulthood; cysts could be found in other organs (eg: liver, pancreas, seminal vesicles); possible presence of intracranial aneurysms |
Medullary cystic kidney disease (MCKD)/ Autosomal dominant tubulointerstitial kidney disease (ADTKD) [16, 18, 26] | Bilateral | Small to normal size kidneys | Multiple cysts in the medulla and at the cortico-medullary junction with cortical sparing | Herditary (autosomal dominant) | MCKD1 (now MUC1), MCKD2 | Chronic renal failure manifesting in adulthood; no associated syndrome |
Bilateral | Moderately enlarged (infantile NPH); small to normal size (juvenile and adolescent/adult NPH) | Small, hyperechoic kidneys with loss of cortico-medullary differentiation; progressive cystic disease with numerous small discrete cysts in the medulla and cortico-medullary junction | Hereditary (autosomal recessive) | More than ten mutations identified until now (eg; NPHP 1 e NPHP4) | Polyuria and polydipsia because of renal concentration defect; growth retardation; chronic anemia resistant to therapy; chronic renal failure with end-stage renal disease developing in infancy or at a median age of 13 years (juvenile NPH) or 19 (adolescent/adult NPH). Presence of associated syndromes | |
Unilateral | Small kidney that disappear in adulthood | Kidney replaced by noncommunicating cysts with a central region of soft tissue; absence or severe atrophy of ipsilateral ureter, renal collecting system and renal vasculature | Acquired | None | Often detected in utero or infancy; possible association with contralateral vescico-ureteral reflux (5–43% of cases) | |
Bilateral | Small | Atrophic hyperechoic kidneys with cysts (at least three in each kidney) varying in size and complexity | Acquired | None | Presence of end-stage renal disease, the incidence increases with the length of time on dialysis; cysts could be complicated (hemorrhage, nephrolithiasis); possible development of renal malignancy | |
Generally bilateral, mild cases can be diagnosed as unilateral by ultrasound | Normal (size is more linked to the presence or absence of chronic kidney disease) | Hypoechoic medullary areas with hyperechoic spots and microcystic dilatation of papillary zone; multiple calcifications (linear, small stones or calcified intracystic sediment) in each papilla. In some cases nephrocalcinosis could be described | Hereditary in a half of cases (autosomal dominant) | Mutations of GDNF (12% of cases). Genetics under investigation | Typically observed in renal stone formers; possible presentation as pielonephritis; michroematuria and episods of machroematuria associated with nephrolithiasis. Possible presence of hyperparatiroidism. Association with tubular defect (eg: distal renal tubular acidosis, hypocitraturia defective urinary concentration, an altered Tm (transport maximum) for glucose, phosphate and para-aminohippuric acid, low molecular weight proteinuria). |