Retrograde intrarenal surgery for stones associated with renal anomalies: caliceal diverticulum, horseshoe kidney, medullary sponge kidney, megacalycosis, pelvic kidney, uretero-pelvic junction obstruction

PURPOSE OF REVIEW

Nowadays, due to the increase of imaging diagnosis, we identify easily renal anomalies, and we can choose between a wide range of armamentarium to treat symptomatic stones in those challenging cases. However, there is a lack of evidence and consensus on its use. The aim of this narrative review is to collect all the available data about safety and efficacity of retrograde intrarenal surgery (RIRS) in the treatment of kidney stones associated to a renal anomaly.

RECENT FINDINGS

Renal anomalies are uncommon findings and even more if it has to be associated with renal stones. After a literature review of the past 2 years, there are a small number of studies that compare the outcomes in patients who have been treated with minimally invasive modalities and they are mainly focus on RIRS.

SUMMARY

It is of extreme importance to know the advances on the stone treatment in anomalous kidneys. With the development of new laser technologies, RIRS is becoming a more interesting technique with high success rate and safety. Further studies are needed to make an accurate statement about the adequate surgical technique for each renal anomaly and also, clinical trials using new laser technologies.

CT urography for the diagnosis of medullary sponge kidney

BACKGROUND

Medullary sponge kidney (MSK) is characterized by malformation of the terminal collecting ducts and is associated with an increased risk of nephrolithiasis, nephrocalcinosis, urinary tract infections, renal acidification defects, and reduced bone density. It has been historically diagnosed with intravenous pyelography (IVP), which is falling out of favor as an imaging modality. CT urography (CTU) performed with multidetector CT (MDCT) has been shown to create images of the renal collecting system with similar detail as IVP; however, its utility in diagnosing MSK has not been defined.

CASE REPORT

We present the first 15 patients with recurrent symptomatic nephrolithiasis who were evaluated in our renal stone clinic with CTU. Four patients were diagnosed with MSK after visualization of the characteristic radiologic findings.

DISCUSSION

CTU effectively demonstrates the characteristic radiologic findings of MSK including collecting tubule dilatation, medullary nephrocalcinosis, nephrolithiasis, and medullary cysts. Dose reduction protocols can reduce radiation exposure below that associated with conventional IVP. We propose CTU be considered for the diagnosis of MSK.

Nephrolithiasis in medullary sponge kidney: evaluation of clinical and metabolic features

OBJECTIVE

Medullary sponge kidney (MSK) is a disorder characterized by tubular dilation of renal collecting ducts and cystic dilation of medullary pyramids that has been associated with stone disease. The significance of nephrolithiasis and the mechanisms by which it occurs are incompletely understood. We describe clinical and metabolic features of nephrolithiasis in a cohort of patients with MSK.

METHODS

Records were reviewed of 56 patients, all with radiographic diagnosis of medullary sponge kidney and data collected pertaining to presentation, stone events and recurrences, stone composition, and metabolic profile to perform a descriptive study with median 3.7 years follow-up.

RESULTS

Nephrolithiasis was confirmed radiographically in 39/56 patients (69.6%). No patient without evidence of nephrolithiasis developed a stone event, whereas 13/39 (33%) of those with nephrolithiasis developed a recurrent stone event. Stones were composed of calcium oxalate monohydrate, calcium oxalate dihydrate, calcium phosphate apatite, and uric acid. Metabolic profile was obtained for 26 of 39 (67%) stone-forming patients demonstrating abnormalities in 22/26 (84.6%). These included hypercalciuria, 58% (15/26); low urine volume, 35% (9/26); hyperuricosuria, 27% (7/26); hypocitraturia, 19% (5/26); elevated urine sodium, 15% (4/26); and hyperoxaluria, 12% (3/26).

CONCLUSION

Many patients with MSK have no evidence of nephrolithiasis. Among those who do, recurrence is common, and metabolic profile and composition are varied as in the general stone-forming population.

Diagnosis of Medullary Sponge Kidney by Computed Tomographic Urography

The diagnosis of medullary sponge kidney traditionally was established by means of intravenous pyelography. Beginning in the mid-1990s, intravenous pyelography rapidly was supplanted by computed axial tomography as the preferred imaging study for evaluating patients with renal stone disease. Conventional computed tomographic imaging has not been satisfactory for diagnosing medullary sponge kidney. The introduction of multidetector-row computed tomography in 1999 allowed radiologists to acquire images composed of elements allowing the creation of high-resolution 3-dimensional displays. Computed tomographic urography is an imaging technique that provides both cross-sectional displays and images of the contrast-filled renal collecting systems, ureters, and urinary bladder that are the equivalent of intravenous pyelography. We report a case of medullary sponge kidney diagnosed by means of 3-dimensional multidetector-row computed tomographic urography.

Medullary sponge kidney associated with distal renal tubular acidosis in a 5-year-old girl

INTRODUCTION

Medullary sponge kidney (MSK) is characterized by cystic dilatation of the inner medullary collecting ducts, which causes the kidneys to resemble a sponge.

CASE REPORT

Although distal renal tubular acidosis (dRTA) is commonly observed in patients with MSK, we report a 5-year-old girl with MSK who had features of both dRTA (nephrocalcinosis, hypercalciuria, hypocitraturia) and proximal tubular dysfunction (hyperuricosuria, impaired tubular phosphate reabsorption and proteinuria).

DISCUSSION

Metabolic acidosis, hypercalciuria, hypocitraturia, tubular phosphate reabsorption and growth retardation in the patient improved with alkali therapy.

[Kidney sponge--treatment--case report]

Medullary sponge kidney (MSK) is a benign asymptomatic developmental anomaly of the kidney mostly seen in adult females. Typical for this morphological abnormality is dilation of the collecting ducts. Intravenosus pyelogram shows accumulation of contrast in dilated ducts giving to the papillae the appearance of a bouquet flowers, characteristic for MSK. Urinary tract infections, nephrolithiasis, hematuria and hyperkalciuria are the common complications of the kidney sponge. We present a case of a 29-year-old female who suffers from recurrent urinary tract infection, nephrolithiasis and distal tubular acidosis. This kind of tubular acidosis is specific for kidney sponge clinical picture.

[Cacchi and Ricci's disease. Radiology, epidemiology and biology]

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.

[Prevalence of medullary sponge kidney in patients with and without nephrolithiasis]

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.

[Medullary sponge kidney with severe renal function impairment: a case report]

The term medullary sponge kidney refers as a renal parenchymal malformation characterized by cystic dilatation of the collecting ducts. Although medullary sponge kidney is a congenital disease, it is rarely identified in childhood and is usually discovered in adulthood. We report a child with bilateral medullary sponge kidney who, in addition to typical urographic findings, presented an unfavorable evolution that ended in renal chronic insufficiency. This outlook is uncommon and is described in only 10% of affected subjects.

Papillary necrosis and medullary sponge kidney in a patient with hemoglobin SC

A 22-year-old woman with hemoglobin SC who was hematologically asymptomatic, developed gross hematuria associated with urinary tract infection, without any urological antecedents. Investigations revealed a unilateral hematuria due to papillary necrosis on the left kidney. Medullary sponge kidney was also discovered by radiologic investigations. Papillary cysts could play a role in the occurrence of papillary necrosis.

The use of extracorporeal shock wave lithotripsy for medullary sponge kidneys

A number of patients with medullary sponge kidney recurrently form and pass stones with the risk of developing an obstructive nephropathy. These patients may benefit from extracorporeal shock wave lithotripsy to the medullary collections, as this appears to reduce the frequency of symptomatic stone passage.

Use of low-osmolality contrast medium does not increase prevalence of medullary sponge kidney

To assess the prevalence of intrapapillary linear collections of contrast medium as well as of homogeneous papillary blush on excretory urograms obtained with a low-osmolality contrast medium, iohexol was used in 300 patients. Intrapapillary linear collections of contrast medium (ie, three or more linear collections of contrast material within a papilla) were found in 10 (9.5%) of the 105 patients with renal stone disease and two (1.0%) of the 195 patients without nephrolithiasis (P less than .001). These prevalences are similar to those found in a previous study with use of a high-osmolality contrast medium (sodium amidotrizoate). The difference in the prevalence of homogeneous papillary blush between stone formers and non-stone formers was nonsignificant. The authors conclude that intrapapillary linear collections of contrast medium on excretory urograms obtained with use of a low-osmolality contrast medium should be considered to have the same clinical significance as those on excretory urograms obtained with use of a high-osmolality contrast medium, that is, as indicating the presence of medullary sponge kidney.

Medullary sponge kidney on axial computed tomography: comparison with excretory urography

To evaluate features of medullary sponge kidney (MSK) on computed tomography (CT), 4-mm-thick axial slices without intravenous contrast material were first made in 13 patients through 24 kidneys which showed images of MSK on excretory urograms. On CT, papillary calcifications were found in eleven kidneys. In five of these kidneys, the calcifications were not detectable on plain films. Some hyperdense papillae (attenuation value 55-70 Hounsfield units) without calcification were found in four other kidneys. Nine kidneys appeared normal. Ten of these 24 kidneys were reexamined by a second series of 4-mm-thick axial slices, 5 min after intravenous injections of 50 ml of Urografin. Images suggesting possible ectasia of precaliceal tubules were found in only four kidneys. These images appear much less obvious and characteristic on CT than on excretory urogram and do nothing more than suggest the possibility of MSK. In conclusion, the sensitivity of CT in the detection of MSK is markedly lower than that of excretory urography. In the most florid cases of the disease, CT can only show images suggesting the possibility of MSK. On the other hand, CT appears much more sensitive than plain films and tomograms of excretory urography in the detection of papillary calcifications, the most frequent complication of MSK.

Polycystic disease of the kidney coexisting with medullary sponge kidney

A case of simultaneous adult polycystic kidney disease and medullary sponge kidney is reported. Such an occurrence is rare but suggests that these two conditions share a common pathogenesis.

[A case of medullary sponge disease associated with horseshoe kidney]

A 60-year-old man visited our hospital with complaints of micturition pain and interruption of urinary stream. X-ray examinations were performed, showing no bladder and urethral stone. However, KUB revealed bilateral multiple renal stones. Excretory urography showed a horseshoe kidney and a concentration of the contrast medium in the ectatic tubules at the pyramidal apices. Calculi were also located in these ectatic tubules. Thus, we considered that this was a very rare case of medullary sponge disease associated with horseshoe kidney. So far there has been no case report of medullary sponge disease with horseshoe kidney in our country.

Does medullary sponge kidney cause nephrolithiasis?

The prevalence of medullary sponge kidney in patients with nephrolithiasis and the issue of whether or not medullary sponge kidney has a role in the pathogenesis of renal stones are controversial. We studied the excretory urograms of 280 patients with nephrolithiasis and 280 patients without either nephrolithiasis or a history of renal stones to determine the frequencies of medullary sponge kidney in the two groups. The criterion for the diagnosis of medullary sponge kidney was the presence of a minimum of three linear or round collections of contrast material within one renal papilla. In the patients with nephrolithiasis, we also looked for biochemical evidence of metabolic causes of renal stones. The frequency of medullary sponge kidney was 12% in patients with nephrolithiasis compared with 1% in patients without nephrolithiasis. The statistical difference was highly significant (chi square = 27.1; p less than .001). Metabolic disorders accounting for the lithiasis were detected in 93% of the patients with stones without medullary sponge kidney. Such evidence was present in 60% of patients with stones and medullary sponge kidney. The statistical difference was significant (chi square = 25.8; p less than .001). Our results suggest that medullary sponge kidney is a cause of nephrolithiasis.

Computed tomography of renal abscesses complicating medullary sponge kidney

Although urinary tract infection occurs in approximately one-third of symptomatic patients with medullary sponge kidney (MSK), renal abscess is a rare complication of the disorder. We describe two patients with MSK complicated by renal abscesses that were diagnosed by CT. The diagnosis of renal abscess should be suspected in patients with MSK and acute pyelonephritis who do not respond to appropriate antibiotic therapy, and renal CT should be done. Computed tomography may show large abscesses that require percutaneous or open surgical drainage or small abscesses that require prolonged high dose antibiotic therapy.

CT visualization of medullary sponge kidney

Recognizing the changes of medullary sponge kidney (MSK) on computed tomographic (CT) scans may be of value in both diagnosis and in differentiating this from other disease states. The appearance on CT of MSK has not previously been well described. A case is reported that demonstrates ectatic renal collecting tubules visualized by CT, and techniques are suggested to optimize visualization of these changes.

More medullary sponge variants

Sponge kidney has characteristic plain film and urographic findings which are generally regarded as being limited to the medullary pyramids. We describe two groups of patients with renal changes of medullary sponge kidney who show additional renal abnormalities. In the first group there were multiple cortical cysts; in the second there were cavities deep in the medulla, many of which communicated with the calices. Neither of these findings has been described before and we suggest that the spectrum of changes associated with this condition is wider than has previously been appreciated.

Familial medullary sponge kidney in association with congenital absence of teeth (anodontia)

Medullary sponge kidney was found in association with congenital absence of teeth (anodontia) in 3 siblings of a single family. Anodontia occurs in the rare familial syndrome of ectodermal dysplasia, but its association with a renal (mesodermal) anomaly is not known. The present report lends further support to a possible hereditary etiology for medullary sponge kidney.

Medullary sponge disease in horseshoe kidney

We report on a patient with a combination of medullary sponge disease and horseshoe kidney. The coexistence of two uncommon conditions of the kidney in this case obscured the clinical picture, and the patient was perhaps subjected to unnecessary invasive tests to establish the diagnosis. Medullary sponge disease occasionally will present as hematuria, and the condition should be kept in mind as a differential diagnosis since it is almost always recognizable on intravenous urography.

Dietary factors and medullary sponge kidneys as causes of the so-called idiopathic renal leak of calcium

Out of 89 stone formers with idiopathic hypercalciuria, 51 remained hypercalciuric on a low calcium diet over 5 days: a renal leak of calcium could thus have been suspected in them. Dietary factors such as high sodium or high animal protein intake, and metabolic factors such as obesity with or without hyperinsulinemia, which all might account for the hypercalciuria of these patients, have been evaluated. This evaluation revealed conditions known to be associated with hypercalciuria in 37 of these 51 patients: 15 had hypercalciuria related to a high sodium intake, 7 had severe hyperuricosuria (greater than 1 g/24 h) reflecting a high animal protein intake, 20 were obese (greater than 120% of ideal weight) with (7 cases) or without (13 cases) concomitant high fasting plasma level of insulin (greater than 18 microU/ml). A careful retrospective analysis of the intravenous pyelograms disclosed medullary sponge kidneys in 8 cases which had remained undiagnosed so far. One of them was studied histologically. Only 14 out of 51 patients had an otherwise unexplained hypercalciuria on a low calcium diet. It is concluded that dietary causes appear to play a key role in 'idiopathic' hypercalciuria, that the incidence of a primary renal leak of calcium among idiopathic stone formers is much smaller than initially thought, and that this condition can hide unrecognized medullary sponge kidneys.

Medullary sponge kidney in childhood

Medullary sponge kidney is reported in six children aged 2-18 years. One child was asymptomatic; the others had hematuria or a urine-concentrating defect. Renal function and size were otherwise normal, as was liver function. The diagnosis was made at excretory urography according to criteria established in adults. Sonography revealed hyperechogenic pyramids, at first at the periphery, later generalized. Computed tomography proved this to be calcium. Medullary sponge kidney is rare but exists in children. Sonography is very sensitive to the pyramidal nephrocalcinosis that complicates this disease and explains the frequent presenting symptom of hematuria in these children.

[Medullary sponge kidney. Diagnosis and course in 12 cases]

12 adult patients with medullary sponge kidney (MSK), followed up for 1 to 14 years (mean 7 years) are presented. MSK was initially diagnosed in 4 cases. In 8 cases the initial diagnosis included pyelonephritis, nephrocalcinosis, and nephrolithiasis. Renal calculi (4 patients), urinary tract infection (8) and hematuria (5) were the most frequent symptoms. Renal tubular acidosis was documented in 2 patients and hypercalciuria without hyperparathyroidism in 2. Over the years renal calculi increased in size in 4 patients. Renal function was stable in 11. In one patient with associated, well controlled hypertension, serum creatinin rose from 141 to 298 mumol/l over 14 years.

Cystic dilatations of the upper urinary tract: a radiologist's developmental model

The ureteral bud in the embryonic kidney grows and branches dichotomously for 15 generations. This branching tree is modified by a series of narrowings and expansions and becomes the ureter, the renal pelvis, the calyces, and the collecting tubules. Simultaneously, the ureteral bud induces the formation of nephrons. If many of the renal cystic diseases and congenital dilatations of the renal pelvis and ureter are viewed as a series of growth disturbances along the branching ureteral bud, their morphology and pathophysiology become clarified even though their etiology is often not known.

Medullary sponge kidney presenting as polycystic renal disease

We observed a 30-year-old woman in whom a large mass in the right lower quadrant and bilaterally enlarged cystic kidneys with markedly distorted collecting systems by excretory urography suggested a diagnosis of polycystic renal disease (PRD); but the linear and cystic dilatation of collecting tubules, many of which contained numerous calculi, was typical of medullary sponge kidney (MSK). Arteriography and CT scanning clearly showed that both the calcifications and the cysts were confined to the medullary portions. The cortical layer was entirely free of cysts except where large medullary cysts protruded to the surface. In patients in whom MSK imitates PRD, these conditions can be distinguished by CT scanning and arteriography.

Differential diagnosis of medullary sponge kidney

The diagnosis of medullary sponge kidney ( MSK ) is usually made as an incidental finding on pyelogram. The essential abnormality of this condition is a " paintbrush " appearance of the calyces due to the presence of contrast within dilated collecting ducts. Since the radiologic features are similar to those of papillary necrosis, a history of analgesic abuse may make the differential diagnosis difficult. We describe a patient whose urogram strongly suggested MSK but who also had a history of analgesic abuse. Special studies demonstrating completely normal renal function and proven MSK in the patient's mother allowed the diagnosis of medullary sponge kidney. We reviewed the similarities and differences between MSK and papillary necrosis to identify features of diagnostic significance.

Medullary sponge kidney and urolithiasis

A review of the urographic findings in 200 patients with renal colic due to urolithiasis demonstrated radiological evidence of medullary sponge kidney in 34, an incidence of 17%. In the majority, the diagnosis was readily made and the changes were bilateral and extensive. This relatively high incidence suggests that medullary sponge kidney may be a contributing factor in a population already predisposed to calculus formation because of other factors such as diet and dehydration.

Simultaneous medullary sponge and adult polycystic kidney disease: the need for accurate diagnosis

Two cases of simultaneous medullary sponge and adult polycystic kidney disease developed in siblings. The diagnoses of polycystic kidneys were made by renal ultrasonography and medullary sponge kidney was diagnosed roentgenographically. The family history was markedly positive for "cystic" disease. Medullary sponge kidney might be a precursor of polycystic kidney disease in some instances, or, more likely, this represents two separate afflictions occurring in the same individuals. When large medullary sponge kidneys are encountered, the possibility of concomitant polycystic kidney disease should be entertained and investigated with a sonogram. While the prognosis of isolated sponge kidney is excellent, polycystic kidney disease eventually leads to hypertension and renal failure.