海綿腎是個腎臟構造異常和基因異常的疾病，發生率並不高，約千分之五到十，是因為腎臟在發育時後腎間葉組織的GDNF 和RET 之間交互作用出現缺失，導致泌尿系統異常。疾病本身可以合併腎臟腫瘤或腎臟以外，如先天性肝內膽管擴張和肝纖維化的表現。主要的臨床表現是反覆的泌尿系統結石、腎鈣質沉積症和腎盂腎炎，原因是高尿鈣、低檸檬酸尿症及高尿液酸鹼度，也可以伴隨著第一型腎小管酸中毒及腎小管功能損傷。疾病本身沒有有效的治療方式，主要的治療是針對泌尿道結石做預防及治療，一般建議可以使用檸檬酸鉀來增加尿中檸檬酸及降低尿中鈣濃度。儘管現今的影像醫學進步，但電腦斷層和核磁共振對海綿腎的診斷能力，比不上靜脈注射腎盂攝影。

Medullary sponge kidney (MSK) is a disorder of renal abnormality and genetic abnormality. Incidence of MSK is 0.5% to 1% worldwide. The pathophysiologic mechanism of MSK is the defect of interaction between glial cell line-derived neurotrophic factor (GDNF) and receptor tyrosine kinase (RET). Clinical manifestations of MSK are recurrent urolithiasis, nephrocalcinosis and pyelonephritis, and sometimes combination of type 1 renal tubular acidosis. The etiology of recurrent renal stone is due to hypercalcinuria, hypocitraturia and relative high urine pH. Treatment and prevention of renal stone formation by potassium citrate is recommended. Intravenous pyelography remains gold standard of diagnosis of MSK, despite of computer tomography and magnetic resonance imaging.