EDITORIAL COMMITrEE

Tomas Berl, Editor William Henrich Mark Paller Fred Silva

Denver, CO Toledo, OH Minneapolis, MN Oklahoma City, OK

NEPHROLOGY TRAINING PROGRAM:DUKE UNIVERSITY MEDICAL CENTER

The nephrology training program at the Duke University School of Medicine provides comprehensive training inclinical nephrology. dialysis, renal transplantation, and hypertension. Fellowship options include a 3-year clinicalinvestigator pathway, a 3-year basic science investigator pathway, and a 2-year clinical training track.

Each fellow completes a clinical program that includes rotation on three services: the transplant service, the acutenephrology service, and the consult service at the Durham Veterans’ Affairs Medical Center. During the transplantrotation, the fellow is involved in the evaluation of donor and recipient candidates for kidney and simultaneouskidney-pancreas transplant. Post-transplant care is primarily the responsibility of the nephrology division. The acute

service provides interventional support to Duke University Medical Center’s intensive care units. an inpatient renal ward,and a general renal consultation service. Outpatient activities include the longitudinal management of fellows’ ownrenal transplant, dialysis, chronic renal failure, and nephrology referral patients.

Clinical facilities include the 1 100-bed Duke University Medical Center and the 450-bed Durham Veterans’ AffairsMedical Center. The division directs five outpatient dialysis facilities, providing care for over 375 dialysis patients. Activeperitoneal and home hemodialysis programs are included. The renal transplant program at Duke University Medical

Center averages 70 kidney and simultaneous kidney-pancreas transplants each year. The Duke Hypertension Centerprovides the opportunity for clinical experience in refractory hypertension. A National Institutes of Health (NIH)-

supported General Clinical Research Center is often used by the division.

The basic science investigator pathway includes 2 years of research under the direction of a faculty sponsor. Thedivision currently has a NIH-training grant as welt as a Transplantation Program Project Grant with three faculty membersinvolved. NIH-funded basic science investigation is also ongoing in areas including metabolic bone disease, geneticpredisposition for hypertension. signal transduction, and receptor regulation.

Advanced training in biostatistics. study design. and epidemiology (including the opportunity to pursue a Masters ofHealth Science degree) is available to fellows choosing the clinical investigator pathway. NIH- and industry-funded trialsin hemodialysis vascular access, cardiovascular disease in renal failure patients, adequacy of dialysis and dialysis

membranes, use of atrial natriuretic peptide in acute renal failure, and treatment of metabolic bone disease in

hemodialysis patients are ongoing.

The straight clinical pathway includes 18 months of intensive clinical training that encompasses all areas ofnephrotogy. including the management of outpatient hemodialysis and significant outpatient transplant and hyper-tension experience. with a brief exposure to clinical research. In addition, structured exposures to renal pathology andhistocompatibility are available.

Medullary Sponge Kidney Associated with CongenitalHem ihypertrophyOlafur Skuli Indridason, Laura Thomas, and Michael Berkoben2

L. Thomas, Department of Radiology, Duke University

O.S. Indridason, M. Berkoben, Division ofNephrology, Medical Center, Durham, NC

Duke University Medical Center, Durham, NC (J. Am. Soc. Nephrol. 1996; 7:1123-1130)

ABSTRACTMedullary sponge kidney is a developmental disor-

1 Received September 21. 1995. Accepted February 10. 1996. . . .

2 Correspondence to Dr. M. Berkoben, Box 3014, Duke University Medical Center, der characterized by ectatuc and cystic malformationDurham, NC 27710. of the collecting ducts and tubules. Clinical manifes-104&6673/0708-1 123$03.OOIO tations include urinary tract infections, renal stones,Journal of the American SocIety of Nephrology . .

Copyright © 1996 by the American Society of Nephrology and hematuria. It can be associated with other de-

Journal of the American Society of Nephrology 1123

Medullary Sponge Kidney and Congenital Hemihypertrophy

1124 Volume 7 . Number 8 . 1996

velopmental disorders. A case of medullary spongekidney associated with congenital hemihypertrophy,complicated by nephrocalcinosis and nephrolithia-sis, is reported here.

Key Words: Hypercalciuria. kidney calculi. renal tubular aci-

dosis, nephrocalcinosis

M edullary sponge kidney is characterized by ec-

tatic and cystic malformations of the collecting

ducts and tubules of one or more papillae of one or

both kidneys. The cysts measure 1 to 7.5 mm in

diameter, are most prominent in the Inner paplllae,

are lined with cuboidal or columnar epithellum, and

communicate with the dilated ducts and tubules (1-

3). In and of themselves, these anatomic abnormali-

ties produce no symptoms. The morbidity of this

disorder is the result of nephrobithiasis and urinary

tract infectIon, both of which are thought to be sec-

ondary to the anatomic abnormalities. Not surpris-

ingly, then, medullary sponge kidney is often diag-

nosed incidentally by intravenous urography In the

work-up of hematuria, kidney stones, or urinary tract

infections ( 1 ). Although usually diagnosed In adult

life, the disorder is thought to be congenital. It has

been described in association with other congenitaldisorders ( 1 ,4). We report a case of medullary sponge

kidney associated with congenital hemihypertrophy.

The case also demonstrates many of the salient dm1-

cab features of medublary sponge kidney.

CASE REPORT

The patient is a 35-yr-old man who experiencedacute renal colic from a kidney stone in October 1992.Initial evaluation was remarkable for hypercalciurla

(450 mg/24 h), borderline hyperuricosuria (789

mg/24 h), and a high urinary sodium excretion rate

(383 mmol/24 h). He had normal citrate excretion (2.6

mmol/24 h) but mildly elevated oxalate excretion

(44.0 mg/24 h) rates. His serum creatinine concentra-

tion was 1 . 1 mg/dL, BUN 24 mg/dL, sodium 143

mmol/L, potassium 4.2 mmol/L, chloride 103

mmol/L, and CO2 29 mmoh/L. His serum calcium

concentration was 10. 1 mg/dL, phosphorus 3.4 mgI

dL, uric acid 6.2 mg/dL, and albumin 4.6 g/dL. The

serum intact parathyroid hormone bevel was 38

pg/mL (normal range, 13 to 64 pg/mL), the serum

1 ,25-dlhydroxyvltammn D level was 29 pg/mL (normal

range, 15 to 50 pg/mL), and the serum 25-hydroxyvi-

tamin D level was 27 ng/mL (normal range, 15 to 80

ng/mL). The hemogram was normal. Urinalysis

showed pH 6.0, specific gravity 1.014, and 19 white

blood cells per high-powered field (hpf). An abdominal

radiograph demonstrated extensive bilateral nephro-

calcinosis (Figure 1 ). Computed tomography of theabdomen demonstrated extensive bilateral nephrocal-

cinosis and milk of calcium (chalky white liquid) in

ectatic renal tubules (Figure 2). A high fluid intake

and dietary sodium and oxalate restriction were pre-

scribed. In March 1993, a 24-h urine sample was

Figure 1. Abdominal radiograph done on initial presentationshowed extensive nephrocalcinosis.

Figure 2. Computed tomography scan of abdomen demon-strated ectatic tubules and extensive nephrocalcinosis.

taken, which contained 367 mg calcium and 205

rnmol sodium. In December 1993, a 24-h urine sam-

ple was taken, containing 323 rng calcium and 304

mmol sodium. Urinalysis was remarkable for hema-

tuna and pyuria, but a urine culture yielded no

growth. An abdominal radiograph demonstrated pro-

gression of nephrocalcinosis. The patient was referred

to us for further evaluation and management.

At the time ofhis first visIt to us in January 1994, he

was asymptomatic, was following the prescribed diet,

and was maintaining a urine volume greater than 2 L

per day. His past medical history was remarkable forsurgical repair of an umbilical hernia in 1 976 and

surgery for a discrepancy in leg length in the early

1970s. He had no history ofgout, inflammatory bowel

disease, chronic diarrhea, hyperparathyroidism, neckirradiation, or granubomatous disease. His only med-

ication was a multivitamin that included vitamins A

(10,000 IU), C (3000 mg), and D (100 IU). He was a

vegetarian. He did not drink milk or eat cheese. He

took no antacids, calcium supplements, or protein

supplements. The family history was significant in

that his mother passed a kidney stone shortly after

Indridason et al

Journal of the American Society of Nephrology 1125

giving birth to him. In addition, the patient reported

that one of his mother’s arms was much smaller than

the other. The physical examination was unremark-

able except that the right leg was larger than the left

(Figure 3). The circumference of the right thigh was

58.8 cm and that of the left 55.2 cm. The circumfer-

ence of the right calf was 40.8 cm and that of the left

36.0 cm. Pertinent laboratory data included a serum

potassium level of3.8 mEq/L, a serum CO2 bevel of 33mEq/L, and a serum creatinine concentration of 1.2

mg/dL. Urinalysis showed a specific gravity of 1 .0 10,

pH of5.0, 19 white blood cells per hpf, and 3 red blood

cells per hpf. A urine culture again yielded no growth.

A 24-h urine sample contained 208 mg calcium, 105

mmol sodium, 42 mg oxalate, and 4.4 mmol citrate. It

was recommended that the patient discontinue taking

the multivitamin. Because of persistent hypercalci-

uria, a thiazide diuretic was prescribed. He refused to

take it. In November 1994, his serum creatine level

was 1 .0 mg/dL and serum CO2 bevel was 29 mEq/L. A

24-h urine sample contained 384 mg calcium, 155

mmob sodium, and 838 mg uric acid. An abdominal

radiograph demonstrated no progression of nephro-

calcinosis. He has continued to pass minute kidney

stones on occasion, but has experienced no renal

colic, hematuria, or urinary tract infections.

ETIOLOGY

The association of medullary sponge kidney with

congenital abnormalities and the unchanging nature

of the cystic lesions over time suggest that it is a

developmental disorder ( 1 ,4). It Is usually sporadic

but has been reported in two or more successive

generations of several families (1).

PREVALENCE

In a geographical area of the United Kingdom with a

population of 254,000, Mayall found 1 2 cases of med-

ullary sponge kidney in 2600 intravenous urograms,

suggesting a prevalence of 5 per 100,000 in the gen-

eral population (5). This is likely to be an underesti-

matlon, as asymptomatic patients do not undergo

urography. Other studies have shown a prevalence of

0.5 to 1 % in unselected patients undergoing urogra-

phy ( 1 ,6). In patients with stones, the prevalence has

been reported to be 2.6 to 2 1 % ( 1 ,6-8). When corn-pared with men with calcium stones, women with

calcium stones are more likely to have medullary

sponge kidney ( 1 ,7). The prevalence of medullary

sponge kidney may be as high as 25% in women with

calcium stones (1).

PATHOPHYSIOLOGY

The cysts frequently contain calcific deposits. These

deposits are radio-opaque, frequently appear in clus-

ters on plain film of the abdomen, and are composed of

an admixture of calcium apatite and calcium oxalate

or of calcium apatite alone ( 1 ). Erosion of these con-

cretions through the papillary wall into the renal

pelvis may head to symptomatic stone disease.

Several factors contribute to the formation of intra-

papillary calcium concretlons (Table 1 ). First, urinary

stasis within the cysts likely plays a role ( 1 ). Second,

cellular debris and hyahine material In the cysts may

provide a matrix for stone formation ( 1 ). Third, Im-

paired urinary acidification may decrease the solubil-

ity of calcium apatite (9-12). Finally, any or all of the

risk factors for idiopathic calcium stone disease (hy-

percalciuria, hyperoxaburia, hyperuricosuria, hypoci-

Figure 3. Views showing enlarged right leg of patient.

Medullary Sponge Kidney and Congenital Hemihypertrophy

1 126 Volume 7 . Number 8 . 1996

TABLE 1 . Factors that may promote formation ofintrapapillary concretions

Urinary StasisInfectionIntraluminal DebrisImpaired Urinary AcidificationRisk Factors for Calcium Stone Disease (Hypercalciuria,

Hyperoxaiuria, Hypocitraturla, Hyperuricosuria)

traturia) may be present In patients with medulbary

sponge kidney ( 1 ,6,8). The impaired urinary acidifica-

tion and the hypercalciurla of medullary sponge kid-

ney merit further comment.

Impaired Urinary Acidification

The terminal collecting duct is a principal site of theanatomic lesions of medulbary sponge kidney (1,2).

The terminal collecting duct also plays a major role In

urinary acidification. Indeed, investigators have re-

ported impaired distal acidification in a substantialproportion of patients with medullary sponge kidney.

Higashihara and coworkers (9) studied 1 1 stone form-

ers with medullary sponge kidney. Baseline arterialblood pH was normal in all, but the baseline plasma

bicarbonate concentration was low In seven patients.

The urine pH of four patients did not fall below 5.3after ammonium chloride loading and thus met the

criteria for partial distal renal tubular acidosis. All

four had low plasma bicarbonate concentrations. The

urine pH of another five patients did not fall below5. 10. When compared with healthy subjects and to

patients with bilateral stones, the 1 1 patients with

medullary sponge kidney had lower baseline plasma

bicarbonate concentrations (mean, 22. 1 mEq/L) and

had higher urine pH values in response to ammoniumchloride loading. Similarly, Osther and colleagues (10)

studied 13 stone formers with medublary sponge kid-

ney and found two with complete and six with partial

distal renal tubular acidosis. More recently, Osther et

at. ( 13) reported his findings In ten women with med-

ullary sponge kidney. Four had partial renal tubular

acidosis. When compared with the six women withnormal urinary acidification, the four with partial

renal tubular acidosis had lower fasting plasma bicar-

bonate concentrations (20.5 mEq/L versus 23.8

mEq/L) and lower 24-h urinary citrate excretion rates

(0.93 mmol versus 3.58 mmoh; normal, >1.8 mmol).Other investigators have found that the 24-h urInarycitrate excretion rate is bower in recurrent stone form-

ers with medullary sponge kidney than In idiopathicstone formers (11).

The results of studies of urinary acidification inmeduhlary sponge kidney are summarized In Table 2.

On the basis of these results, we believe that we canmake the following statements. First, a substantial

proportion (perhaps one half) of patients with medul-bary sponge kidney have partial or complete distal

renal tubular acidosis. Second, a low plasma bicar-

bonate concentration and hypocitraturia will identifysome, but not all, patients with renal tubular acidosis

(9, 12, 13). Third, when compared with healthy sub-

jects or to patients with bilateral stones, patients with

medullary sponge kidney have lower baseline plasma

bicarbonate concentrations and higher minimal urinepH values in response to ammonium chloride loading

TABLE 2. Investigations of urinary acidification in medullary sponge kidneya

Number MeanNumber with Baseline

.investigators(Reference Number)

of.

Patients(Male/

Female)

RenalTubularAcidosis(Partial/

Complete)

Plasma.

BicarbonateConcentrationin Patients with

PTA (mEq/L)

.

Citrate Excretion

Backman et al. (1 1) 14 (9/5) 3 (3/0) (Not reported) Mean 24-h urinary citrateexcretion rate lower inpatients with MSK thanin idiopathic stoneformers

Higashihara et al. (9) 11 (4/7) 4 (4/0) 21.8 Not reportedOsther et a!. (10) 13 (3/10) 8 (6/2) (Not reported) Not reported

Osther et a!. (1 3) 10 (0/ 10) 4 (4/0) 20.5 Mean 24-h urinary citrateexcretion rate 0.93mmol in patients withPTA and 3.58 mmol Inthose without PTA

Mayers et a!. (12) 24 (9/ 15) 12 (5/7) (Not reported) Hypocitraturia in seven of 12patients with PTA

a PTA, renal tubular acidosis; MSK medullary sponge kidney.

Indridason et al

Journal of the American Society of Nephrology 1127

(9). It seems likely, therefore, that many patients with

medublary sponge kidney have subclinical impairment

of urinary acidification. Proton secretion may be im-

paired in cystic terminal collecting ducts. If only a

fraction of the terminal collecting ducts are cystic, the

patient may still be able to maintain normal systemic

pH and excrete maximally acid urine (pH < 5.3) in

response to ammonium chloride loading. Increased

urine pH wIthin cystic ducts, however, may promote

intraductal precipitation of calcium apatite and bead

to clinical stone disease. Although impaired urinary

acidification may characterize many patients with

medulbary sponge kidney, it does not follow that alkali

therapy will be beneficial (see the Treatment section).

Hypercalciuria

In large series of cases of medullary sponge kidney,

the prevalence ofhypercalciuria Is approximately 40%

(7, 14). Parks and coworkers found that hypercalciuria

was no more prevalent in stone formers with medul-

lary sponge kidney than in stone formers without

medullary sponge kidney (7). In addition, the same

causes of hypercalciuria are present in patients with

medullary sponge kidney as in patients without the

disorder (6,8, 15, 16). Table 3 lists the possible causes

of hypercalciuria in patients with medullary sponge

kidney. Some investigators have reported a prepon-

derance of absorptive hypercalciuria (8), whereas oth-

ers have reported a preponderance of renal hypercal-

ciuria ( 1 7). Although physiologic regulation of calcium

excretion occurs primarily In the cortical distal

nephron under the influence of parathyroid hormone

and calcitriol, calcium reabsorption does occur along

the inner medullary collecting duct of the rat. Some

researchers have speculated that impaired calcium

reabsorption in the cystic ducts may cause the hyper-

calciuria of medulbary sponge kidney. In contrast,

Higashihara and coworkers ( 1 7) have reported that

metabolic acidosis causes renal hypercalciuria. These

Investigators studied 1 6 patients with medulbary

sponge kidney. Seven patients exhibited renal hyper-

calciuria. These patients had higher urine pH values

in response to acid loading and lower plasma bicar-

TABLE 3. Hypercalciuria of medullary sponge kidney

bonate concentrations (22.5 mEq/L) than healthy

control subjects. Six of the seven patients had low

plasma bicarbonate concentrations. Administration of

2 to 4 g of sodium bicarbonate daily reduced calcium

excretion from 5.05 to 2.91 mg/kg per day and re-duced the frequency of stone passage. Osther et at.(13) studied ten women with bilateral medullarysponge kidney. Four women had incomplete distal

renal tubular acidosis. When compared with the six

patients without renal tubular acidosis. and with ten

healthy women, these four patients had lower plasma

bicarbonate concentrations, increased urinary excre-

tion rates of calcium, and decreased urinary excretionrates of citrate. The practical implications of these

findings will be discussed in the Treatment section.

The robe of hyperparathyroidism in the hypercalci-uria of medulbary sponge kidney is debatable. Hyper-

parathyroidism has been demonstrated in a few pa-

tients ( 1 ,6). In large series, however, the prevalence of

hyperparathyroidism In patients with medullary

sponge kidney is not different from that of patients

with idiopathic calcium stone disease (6,7).

Other tubular abnormalities that have been de-scribed include a vasopressin-resistant concentratingdefect ( 1 ,9) and a decreased ability to excrete an acute

potassium load ( 1 8); neither defect has proved to be

clinically significant.

CLINICAL MANIFESTATIONS

Patients are asymptomatic until kidney stones, he-

maturia, or infections develop, typically in adult life.

Stones occur in 50 to 65% of these patients (19-2 1).

When compared with calcium stone formers withoutmedulbary sponge kidney, calcium stone formers with

the disorder have higher rates of stone formation (7).Although intrapapillary concretions are composed of

an admixture of calcium apatite and calcium oxalate

or of calcium apatite alone, pure apatite stones are

rarely passed. Stone analysis demonstrates either

pure calcium oxahate or an admixture of calcium

oxalate and calcium apatite ( 1 ). It thus seems likely

that calcium oxalate deposition occurs in the collect-

ing system before final stone passage. Microscopic or

Etiology(Reference Number)

Laboratory Findings Mechanism

Absorptive Hypercalciuria (8) Urinary calcium excretion less than 0.1 1mg/mg creatinine after fasting andgreater than 0.26 mg/mgcreatinine after calcium loading(15,16)

Supranormal intestinal absorptionof calcium

Penal Hypercalciuria (1 7) Urinary calcium excretion greater than0.1 1 mg/mg creatinine after fasting(15,16)

Impaired calcium reabsorption bycystic ducts and/or metabolicacidosis (17)

Hyperparathyroidism Hypercalcemia; elevated serumparathyroid hormone level

Hypercalcemia

Medullary Sponge Kidney and Congenital Hemihyperirophy

1 128 Volume 7 . Number 8 ‘ 1996

frank hematurla can occur in the presence or absence

of stones ( 1 ,22). Urinary tract infections occur more

frequently in calcium stone formers with medullary

sponge kidney than in calcium stone formers without

the disorder and occur more frequently in women

than in men (7). Perltubular Inflammation has been

demonstrated in the absence of infection and may

result in sterile pyuria (2,3,9). Nephrocalcmnosis Is also

a frequent manifestation of medulbary sponge kidney.

Parks and colleagues (7) reported that nephrocalcino-

sis is present in 15% of calcium stone formers with

medullary sponge kidney and In 3% of calcium stone

formers without medullary sponge kidney.

Medullary sponge kidney is associated with several

developmental and hereditary disorders (Table 4).

Anomalies of the urinary tract, bile duct ectasia (Caro-

li’s disease), congenital pyboric stenosis, Beckwith-

Wiedemann syndrome, Ehbers-Danbos syndrome,

Marfan’s syndrome, polycystic kidney disease, and

congenital hemihypertrophy have been reported in

association with medubbary sponge kidney ( 1 ,4). An

association with primary hyperparathyroidism Is a

matter of debate.

Congenital hemlhypertrophy is characterized by

asymmetry of the body as a result of hypertrophy of all

somatic elements (muscles, bones, nerves, vessels) of

one or more body parts. Visceromegaly may be presentas well. Congenital hemihypertrophy can involve part

or all of one side of the body (complex ipsilateral

hemihypertrophy), body parts on both sides (complex

contrabaterab hemlhypertrophy), a single limb (simple

hemihypertrophy), or one side of the face (hemifaclal

hypertrophy) (23). CongenItal hemlhypertrophy has

been estimated to occur In 1 In 40,000 lIve births (24).It is frequently associated with other developmental

abnormalities such as congenital heart disease, poly-

and syndactyly. mental retardation, Proteus syn-

drome, Silver-Russell syndrome, and Beckwith-

Wiedemann syndrome. Congenital hemihypertrophy

is also associated with childhood tumors, particularly

adrenal adenomas and Wilms’ tumors (24). Nephro-

genic rests and other developmental abnormalities of

the kidney and urinary tract have been reported In

association with congenital hemihypertrophy (23,25).

Up to 10% of patients with congenital hemlhypertro-

phy have medullary sponge kidney (26,27), and up to

25% of patients with medulbary sponge kidney have

congenital hemihypertrophy (14).

TABLE 4. Developmental and inherited disordersassociated with medullary sponge kidney

Congenital HemihypertrophyBeckwith-Wiedemann SyndromeCongenital Pyloric StenosisCaroli’s DiseaseUrinary Tract MalformationsEhlers-Danlos SyndromeMarfan’s SyndromePolycystic Kidney Disease

DIAGNOSIS

Definitive diagnosis is made by intravenous urogra-

phy (IVU). (Although our patient did not undergo IVU,

It was thought that the constellation of clinical find-

ings strongly supported the diagnosis of medulbary

sponge kidney. It was not thought that IVU would

affect his management.) Renal concretions, often ar-

ranged in small clusters in the papillae. may be seenon the initial plain film. With administration of con-

trast medium, ectatic tubules are imaged as striations

radiating from the calyces (�brush”). Cysts are imaged

as round opacifications in the papillae (“bouquets of

flowers” or “bunches of grapes”). Brushes and bou-

quets appear before opacification of the calyces and

may persist after the contrast medium is cleared from

the renal pelves ( 1 ). Firm radiographic criteria for the

diagnosis of medullary sponge kidney have not been

established. In a recent study, a minimum of three

linear or round collections within one renal papilla

was required for the diagnosis of medullary sponge

kidney (6). In previous studies, more stringent criteria

(Involvement of three or more papllbae or of both

kidneys) were used ( 1 ,7,8). Another diagnostic diffi-

culty arises when only diffuse opacification of the

papillae (papillary blushing) is present. Papillary

blushing is detected by urography in 4% of stone

formers and in 3% of non-stone formers (6). Whether

this finding should be considered normal or indicative

of a mild form of medubbary sponge kidney is unclear.

A pathologic diagnosis of medublary sponge kidney

has been established in kidneys that demonstrated

only papillary blushing on urography ( 1 ). Papillary

blushing should be considered diagnostic of medul-

lary sponge kidney if it appears before opaclfication of

the calyces, persists after contrast medium has beencleared from the pelves, and is associated with papil-

lary concretions or nephrocalcmnosis.

Computed tomography (CT), ultrasonography, and

retrograde pyelography have little utility in the diag-

nosis of medullary sponge kidney. CT without injec-

tion of contrast medium appears to be more sensitive

than IVU for detecting papillary concretions (28).

These concretlons, however, are not specific for med-

ullary sponge kidney. IVU remains far superior to CT

(even with injection of contrast medium) in the diag-nosis of medullary sponge kidney because of its far-

greater ability to image tubular ectasia ( 1 ,28). Plain

radiographs of the abdomen with or without tomogra-

phy can be obtained to assist in following the progres-

sion of nephrocabcinosls.

TREATMENT

There is no specific treatment for medullary sponge

kidney ( 1 ). Urinary tract infections are treated with

antibiotics. Patients who develop calcium stones may

have primary hyperparathyroidism or may have any

or all of the risk factors for idiopathic calcium stone

disease. Evaluation of patients with calcium stones,

then, should include measurements of the 24-h un-

Indridason et al

Journal of the American Society of Nephrology 1129

nary excretion rates of calcium, oxalate, uric acid, and

citrate. If the serum calcium level is elevated, then the

serum parathyroid hormone level should be mea-

sured. Therapy should be directed at the underlying

abnormality. Thiazide diuretics may be prescribed for

hypercalciunla and albopuninol for hyperunicosunia.

The use of alkali therapy in patients with calciumstone disease warrants further discussion.

Although many patients with medublary sponge kid-

ney have impaired urinary acidification, it does not

follow that alkali therapy will be beneficial. Alkali

therapy should certainly be prescribed for those with

systemic acidemia (complete renal tubular acidosis).

In those with partial renal tubular acidosis or more

subtle impairment of urinary acidification, however,

alkali therapy may raise urine pH and may promote

mntraductab precipitation of calcium apatite. On the

other hand, the study by Higashihara et at. demon-

strates that, in patients with renal hypercalciunia and

low plasma bicarbonate concentrations, alkali ther-

apy decreases urinary calcium excretion and may

decrease the frequency of stone passage ( 1 7). It is also

rational to prescribe alkali therapy for those with

hypocitratunia (12,14,17).

Stones within the collecting system may be treated

with extracorporeal shock-wave lithotnipsy (ESWL).

The role of ESWL in the treatment of parenchymal

stones needs to be elucidated. A study of eight pa-

tients failed to demonstrate fragmentation or evacua-

tion of parenchymal concretions after ESWL (20).

Another study did demonstrate a reduction in the

stone burden of the renal medulla in 1 7 of 22 kidneys

treated with ESWL (29). Seven patients in this study

reported a long-term decrease in frequency of stone

passage.

SUMMARY

Although our patient did not undergo intravenous

urography, we believe that the constellation of clinical

findings strongly supported the diagnosis of medul-

lary sponge kidney. There was no other explanation

for the nephrocalcinosis. He did not have renal tubu-

bar acidosis, hypervitaminosis D, hyperparathyroid-

ism, sarcoldosis, or hypercalcemia, and his history

did not suggest the milk-alkali syndrome. Our patient

demonstrates the association of medullany sponge

kidney and simple hemihypertrophy. in view of his

mother’s history, one or both may be hereditary.

Hypercalciunia and nephrocalcinosis are frequent

manifestations of medublary sponge kidney. A thiazide

diuretic was prescribed to decrease the urinary cab-

cium excretion rate and prevent progression of

nephrocalcinosis, but he has refused to take it. Be-

cause he does not have renal tubular acidosis or

hypocitraturia, alkali therapy is not indicated. A plain

radiograph of the abdomen will be obtained every 6

months to detect progression of nephrocalcmnosis.

REFERENCES

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2. Jaeger P, Portmann L, Ginabskl J, Campiche M, Burck-hardt P: Dietary factors and medullary sponge kidney ascauses of the so-called idiopathic renal leak of calcium.Am J Nephrol 1987:7:257-263.

3. Higashihara E, Nutahara K, Tago K, Ueno A, Niijima T:Unilateral and segmental medullary sponge kidney: Re-nab function and calcium excretion. J Urol 1984:132:743-745.

4. Fick GM, Gabow PA: Hereditary and acquired cysticdisease of the kidney. Kidney Int 1994:46:951-964.

5. Mayalb GF: The incidence of medullary sponge kidney.Radiology 1970:21:171-174.

6. Ginaiski J, Portmann L, Jaeger P: Does medullarysponge kidney cause nephrohithiasis? Am J Roentgenol1990:155:299-302.

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