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Synonym: Cacchi-Ricci syndrome
Medullary sponge kidney (MSK) is a congenital disorder that can affect one or both kidneys, or only part of one kidney. There are ectatic and cystic changes of the medullary and papillary collecting ducts. The names tubular ectasia and cystic dilatation of the collecting ducts have been suggested as alternatives for this condition because the medulla does not actually appear like a sponge. It is bilateral in 70% of cases. Cysts can be 1-7 mm in diameter. Cyst formation is commonly associated with the development of small calculi within the cyst. The rest of the kidney is usually normal unless affected by complications such as pyelonephritis or obstruction secondary to renal calculi.
- Uncertain, though thought to be a developmental abnormality Theories include obstruction of a collecting duct by uric acid at the fetal stage or tubular obstruction secondary to calcium oxalate crystals formed during an episode of hypercalciuria in infancy.
- Most cases are sporadic.
- Familial forms with autosomal dominant inheritance exist but are rare. Online Mendelian Inheritance in Man (OMIM) lists two types of medullary cystic kidney disease with autosomal dominant inheritance - medullary cystic kidney disease 1 and 2. These conditions both have adult onset. There is also another form that has juvenile onset and autosomal recessive inheritance, known as familial juvenile nephronophthisis.
- Recent genetic research has identified a possible defect in the development of the proton pump mechanism in the kidney.
- Estimated prevalence is 5-50 per 100,000
- May be present in as many as 20% of people with renal calculi
- More common in women
- Affected women are also more likely than affected men to develop calculi
- Although it is a congenital disorder, diagnosis is often not made until the second or third decades.
- May be asymptomatic.
- Can be an incidental finding on radiological investigations performed for other reasons.
- Haematuria is common and usually microscopic. Macroscopic haematuria can occur with associated infection or calculi.
- Recurrent urinary tract infection (UTI) is a common presentation and affects more women than men. There may also be sterile pyuria.
- May present with renal calculi and their complications including renal colic, haematuria, infection and urinary obstruction. The stones are usually calcium oxalate and calcium phosphate.
Medullary sponge kidney (MSK) is associated with a number of other congenital disorders. Some of the more common associated conditions include:
- Congenital hemihypertrophy: this is the most frequent association. There is enlargement of a limb or one side of the body compared with the contralateral side beyond the limits of normal variation. 10% of people with congenital hemihypertrophy have MSK.
- Beckwith-Wiedemann syndrome: the association of macroglossia, macrosomia, omphalocele, visceromegaly, MSK, hemihypertrophy, mental retardation, adrenal cortex cysts.
- Congenital hepatic fibrosis.
- Congenital pyloric stenosis.
- Polycystic kidney disease.
- Horseshoe kidney.
- Distal renal tubular acidosis.
- Ehlers-Danlos syndrome.
- Marfan's syndrome.
- Caroli syndrome.
- Multivessel fibromuscular dysplasia (a nonatherosclerotic, noninflammatory vascular disease that commonly affects the renal arteries and other vessels.)
Except for the possible presence of other congenital abnormalities, including hemihypertrophy, there is usually no abnormality to be found on examination.
- Renal calculi: stones are usually small and can pass spontaneously.
- UTI and pyelonephritis.
- Renal failure: due to recurrent infection or obstruction due to calculi. Renal impairment can occur in 10% of patients. (Please refer to separate article Chronic Kidney Disease (Chronic Renal Failure)).
- Wilms' tumour: children with medullary sponge kidney (MSK) have a greater risk of developing Wilms' tumour. This is because of the association of Wilms' tumour with congenital hemihypertrophy and Beckwith-Wiedemann syndrome.
- Distal renal tubular acidosis.
Investigation may be initiated because of recurrent UTI or renal calculi.
- Plain abdominal X-ray: may reveal nephrocalcinosis.
- Ultrasound scan: calcification may be seen on ultrasound examination.
- Intravenous urography: the gold standard investigation. There are radial linear striations in the papillae ('brushlike' patterns). Contrast media collects in the ectatic collecting ducts and is seen as 'bunches of grapes' or 'bouquets of flowers'.
- CT scan: this can show other associated renal abnormalities.
- Urinary calcium: there is hypercalciuria in 30 to 50%.
- Urinary pH: if distal renal tubular acidosis is present, there is inability to form an acid urine in the distal tubule. Urine pH is above 6 and there is associated hypokalaemia with a hyperchloraemic metabolic acidosis.
- The presence of medullary sponge kidney (MSK) does not exclude other pathology and it can coexist with other diseases such as polycystic kidney disease.
- Sterile pyuria can be due to inadequately treated UTI or tuberculosis of the kidney.
- Haematuria requires the exclusion of malignancy of the urinary tract, including clear cell carcinoma of kidney, bladder tumours or Wilms' tumour in children.
- Patient education about the usually benign nature of the condition. Fluid intake should be kept high (at least 2 litres a day) to reduce the risk of both stones and UTI. Avoidance of a high protein diet also reduces the risk of recurrent calculi.
- Complicating UTI and pyelonephritis should be treated with antibiotics.
- Complicating renal calculi should be managed appropriately. This may include extracorporeal shockwave therapy, percutaneous surgery or ureteroscopy. In severe cases of recurrent renal stone, partial nephrectomy may be required. Rarely, total nephrectomy may be necessary in cases of severe recurrent sepsis.
- Investigate for other coexisting pathology, including the exclusion of malignancy if there is haematuria.
- Regular urinalysis and plain abdominal X-ray can help to detect infection and renal tract calcification but there is no general agreement about optimum frequency. Renal function can be monitored using urea, electrolytes, creatinine and eGFR. Affected children should have surveillance for Wilms' and other abdominal tumours.
- A thiazide diuretic may be used to reduce hypercalciuria and stone formation.
- Normally a benign condition that does not affect life expectancy.
- Recurrent stones and pyelonephritis affect about 10%.
- Renal impairment can occur in 10% of patients.
Further reading & references
- Rommel D, Pirson Y; Medullary sponge kidney--part of a congenital syndrome. Nephrol Dial Transplant. 2001 Mar;16(3):634-6.
- Ghosh K, Ghosh AK; Medullary Sponge Kidney; eMedicine, Oct 2009.
- Forster JA, Taylor J, Browning AJ, et al; A review of the natural progression of medullary sponge kidney and a novel grading system based on intravenous urography findings. Urol Int. 2007;78(3):264-9.
- Medullary Cystic Kidney Disease 1; MCKD1, Online Mendelian Inheritance in Man (OMIM)
- Medullary Cystic Kidney Disease 2; MCKD2, Online Mendelian Inheritance in Man (OMIM)
- Nephronophthisis 1; NPHP1, Online Mendelian Inheritance in Man (OMIM)
- Carboni I, Andreucci E, Caruso MR, et al; Medullary sponge kidney associated with primary distal renal tubular acidosis and Nephrol Dial Transplant. 2009 Sep;24(9):2734-8. Epub 2009 Apr 13.
- Medullary sponge kidney. In: Edelmann CM Jr, ed. Pediatric Kidney Disease. Little, Brown, Boston, 1992; 1641-1645
- Mayall GF; The incidence of medullary sponge kidney. Clin Radiol. 1970 Apr;21(2):171-4.
- Bisceglia M, Galliani C; Medullary sponge kidney associated with multivessel fibromuscular dysplasia: Int J Surg Pathol. 2008 Jan;16(1):85-90.
- Beetz R, Schofer O, Riedmiller H, et al; Medullary sponge kidneys and unilateral Wilms tumour in a child with Beckwith-Wiedemann syndrome. Eur J Pediatr. 1991 May;150(7):489-92.
- Hennessy WT, Cromie WJ, Duckett JW; Congenital hemihypertrophy and associated abdominal lesions. Urology. 1981 Dec;18(6):576-9.
- Bueno I, Ventura P, Samper MP, et al; Congenital hemihypertrophy. Genet Couns. 1993;4(3):231-4.
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Dr Michelle Wright
Dr Laurence Knott