Nephrocalcinosis in radiographs, computed tomography, sonography and histology

[Nephrocalcinosis in children]

Nephrocalcinosis is defined by calcium phosphate or calcium oxalate deposits in the kidney parenchyma, particularly in tubular epithelial cells and interstitial tissue. It should be differentiated from urolithiasis where calcium salts deposits are located in the kidney and urinary tract. The epidemiology of nephrocalcinosis in children is unknown but the condition is not so rare, with an increased incidence in preterm infants. Often detected as an incidental finding, nephrocalcinosis may be classified according to the radiological type: medullary, cortical or diffuse. Nephrocalcinosis in children can be caused by a variety of etiology. The most common causes concern medullary nephrocalcinosis and include hereditary tubular disorders, in particular distal renal tubular acidosis and Dent disease, metabolic disorders such as idiopathic hypercalciuria and hyperoxaluria, and iatrogenic causes such as vitamin D intoxication. In the newborn, the main cause is hypercalciuria of the premature baby, whose multifactorial origin is largely iatrogenic. Primary hyperoxaluria which can lead to early onset nephrocalcinosis and usually to chronic kidney disease should always be considered and further investigated. In order to provide a specific diagnosis, it is essential to take into account the family history, the clinical context and complete laboratory data. Early initiation of an appropriate etiological treatment is recommended and may prevent or delay the progression to chronic kidney disease in some cases.

Nephrocalcinosis and Nephrolithiasis in X-Linked Hypophosphatemic Rickets: Diagnostic Imaging and Risk Factors

Context

Nephrocalcinosis (NC) and nephrolithiasis (NL) are described in hypophosphatemic rickets, but data regarding their prevalence rates and the presence of metabolic risk factors in X-linked hypophosphatemic rickets (XLH) are scarce.

Objective

To determine the prevalence rates of NC and NL and their risk factors in patients with XLH with confirmed PHEX mutations.

Methods

Renal ultrasonography (US) and CT were performed in 16 children and 23 adults. The images were evaluated by two blinded radiologists specializing in US and two specializing in CT. Confirmation of NC was determined with a positive result on both US and CT, whereas the diagnosis of NL was confirmed by CT alone. The presence of hypercalciuria, hypocitraturia, and hyperoxaluria was determined from 24-hour urinary samples from each patient. The glomerular filtration rate was estimated.

Results

NC was identified in 15 patients (38.4%), and stratification by age group showed a higher prevalence of NC in children than in adults (56.2% vs 26.1%). CT identified NL in four adults (10.2%). Patients in the pediatric group required intensive use of phosphate, started treatment earlier, and presented greater phosphaturia than those in the adult group (P < 0.01). In addition to hyperphosphaturia, which was present in all patients with XLH, hypocitraturia was the most common metabolic factor (28.2%), whereas hypercalciuria occurred in two patients (5.1%). None had hyperoxaluria. Most patients had normal renal function.

Conclusions

NC was more prevalent than NL. The main metabolic factor was hyperphosphaturia, and intensive phosphate treatment appears to be a worsening factor for kidney calcification.

Genetic, pathophysiological, and clinical aspects of nephrocalcinosis

Nephrocalcinosis describes the ectopic deposition of calcium salts in the kidney parenchyma. Nephrocalcinosis can result from a number of acquired causes but also an even greater number of genetic diseases, predominantly renal but also extrarenal. Here we provide a review of the genetic causes of nephrocalcinosis, along with putative mechanisms, illustrated by human and animal data.

Nephrocalcinosis in Calcium Stone Formers Who Do Not have Systemic Disease

PURPOSE

Nephrocalcinosis is commonly present in primary hyperparathyroidism, distal renal tubular acidosis and medullary sponge kidney disease. To our knowledge it has not been studied in patients with calcium phosphate stones who do not have systemic disease.

MATERIALS AND METHODS

We studied patients undergoing percutaneous nephrolithotomy who had calcium phosphate or calcium oxalate stones and did not have hyperparathyroidism, distal renal tubular acidosis or medullary sponge kidney disease. On postoperative day 1 all patients underwent noncontrast computerized tomography. If there were no residual calcifications, the patient was categorized as not having nephrocalcinosis. If there were residual calcifications, the patient underwent secondary percutaneous nephrolithotomy. If the calcifications were found to be stones, the patient was categorized as not having nephrocalcinosis. If the calcifications were not stones, the patient was categorized as having nephrocalcinosis. Patients were grouped based on the type of stones that formed, including hydroxyapatite, brushite and idiopathic calcium oxalate. The extent of nephrocalcinosis was quantified as 0--absent nephrocalcinosis to 3--extensive nephrocalcinosis. Patients with residual calcifications on postoperative day 1 noncontrast computerized tomography who did not undergo secondary percutaneous nephrolithotomy were excluded from analysis. The presence or absence of nephrocalcinosis was correlated with metabolic studies.

RESULTS

A total of 67 patients were studied, including 14 with hydroxyapatite, 19 with brushite and 34 with idiopathic calcium oxalate calculi. Nephrocalcinosis was present in 10 of 14 (71.4%), 11 of 19 (57.9%) and 6 of 34 patients (17.6%) in the hydroxyapatite, brushite and idiopathic calcium oxalate groups, respectively (chi-square p = 0.01). The mean extent of nephrocalcinosis per group was 1.98, 1.32 and 0.18 for hydroxyapatite, brushite and idiopathic calcium oxalate, respectively (p ≤0.001). The presence of nephrocalcinosis positively correlated with urine calcium excretion (mean ± SD 287.39 ± 112.49 vs 223.68 ± 100.67 mg per day, p = 0.03).

CONCLUSIONS

Patients without systemic disease who form hydroxyapatite and brushite stones commonly have coexistent nephrocalcinosis. Nephrocalcinosis can occur in calcium oxalate stone formers but the quantity and frequency of nephrocalcinosis in this group are dramatically less.

Ultrasound is superior to computed tomography for assessment of medullary nephrocalcinosis in hypoparathyroidism

CONTEXT

Nephrocalcinosis is a complication of hypoparathyroidism and other metabolic disorders. Imaging modalities include ultrasonography (US) and computed tomography (CT). Few studies have compared these modalities, and standard clinical practice is not defined.

OBJECTIVE

The objective of the study was to determine the preferred method for assessing nephrocalcinosis.

DESIGN

The design of the study was a retrospective, blinded analysis.

SETTING

The study was conducted at a clinical research center.

PATIENTS

Twenty-two hypoparathyroid subjects and 7 controls participated in the study.

INTERVENTIONS

Contemporaneous renal US and CT images were reviewed in triplicate by 4 blinded radiologists. Nephrocalcinosis was classified using a 0-3 scale with 0 meaning no nephrocalcinosis and 3 meaning severe nephrocalcinosis.

MAIN OUTCOME MEASURES

Intraobserver, interobserver, and interdevice agreements were measured.

RESULTS

Intraobserver agreement was high, with an overall weighted kappa of 0.83 for CT and 0.89 for US. Interobserver agreement was similar between modalities, with kappas of 0.74 for US and 0.70 for CT. Only moderate agreement was found between US and CT scores, with an intermodality kappa of 0.47 and 60% concordance. Of discordant pairs, 81% had higher US scores and only 19% had higher CT scores. Of nephrocalcinosis seen on US and not CT, 45%, 46%, and 9% were grades 1, 2, and 3, respectively. Overall, US scores were higher than CT with a cumulative odds ratio (95% confidence interval) of 5.97 (2.60, 13.75) (P < .01). In controls, 100% of US ratings were 0, and 95% of CT ratings were 0.

CONCLUSIONS

US is superior to CT for assessment of mild to moderate nephrocalcinosis in patients with hypoparathyroidism. This finding, in combination with its low cost, lack of radiation, and portability, defines US as the preferred modality for assessment of nephrocalcinosis.

Hepatorenal findings in obligate heterozygotes for autosomal recessive polycystic kidney disease

Autosomal recessive polycystic kidney disease (ARPKD), characterized by progressive cystic degeneration of the kidneys and congenital hepatic fibrosis (CHF), is the most common childhood onset ciliopathy, with an estimated frequency of 1 in 20,000 births. It is caused by mutations in PKHD1. The carrier frequency for ARPKD in the general population is estimated at 1 in 70. Given the recessive inheritance pattern, individuals who are heterozygous for PKHD1 mutations are not expected to have clinical findings. We performed ultrasound (USG) evaluations on 110 parents from 64 independent ARPKD families and identified increased medullary echogenicity in 6 (5.5%) and multiple small liver cysts in 10 parents (9%). All ARPKD parents with these abnormal imaging findings were asymptomatic; kidney and liver function tests were unremarkable. Complete sequencing of PKHD1 in the 16 ARPKD parents with abnormal imaging confirmed the mutation transmitted to the proband, but did not reveal any other pathogenic variants. Our data suggest that carrier status for ARPKD is a predisposition to polycystic liver disease and renal involvement associated with increased medullary echogenicity on USG. Whether some of these individuals become symptomatic as they age remains to be determined.

Nephrocalcinosis: re-defined in the era of endourology

Nephrocalcinosis generally refers to the presence of calcium salts within renal tissue, but this term is also used radiologically in diagnostic imaging in disease states that also produce renal stones, so that it is not always clear whether it is tissue calcifications or urinary calculi that give rise to the characteristic appearance of the kidney on x-ray or computed tomography (CT). Recent advances in endoscopic imaging now allow the visual distinction between stones and papillary nephrocalcinosis, and intrarenal endoscopy can also verify the complete removal of urinary stones, so that subsequent radiographic appearance can be confidently attributed to nephrocalcinosis. This report shows exemplary cases of primary hyperparathyroidism, type I distal renal tubular acidosis, medullary sponge kidney, and common calcium oxalate stone formation. In the first three cases--all being conditions commonly associated with nephrocalcinosis--it is shown that the majority of calcifications seen by radiograph may actually be stones. In common calcium oxalate stones formers, it is shown that Randall's plaque can appear as a small calculus on CT scan, even when calyces are known to be completely clear of stones. In the current era with the use of non-contrast CT for the diagnosis of nephrolithiasis, the finding of calcifications in close association with the renal papillae is common. Distinguishing nephrolithiasis from nephrocalcinosis requires direct visual inspection of the papillae and so the diagnosis of nephrocalcinosis is essentially an endoscopic, not radiologic, diagnosis.

Etiology of nephrocalcinosis in northern Indian children

This retrospective survey examines the etiology of nephrocalcinosis (NC) in 40 patients (26 boys), over an 8-year period. The median age at onset of symptoms and presentation was 36 months and 72 months, respectively. Clinical features included marked failure to thrive (82.5%), polyuria (60%) and bony deformities (52.5%). The etiology of NC included distal renal tubular acidosis (RTA) in 50% patients and idiopathic hypercalciuria and hyperoxaluria in 7.5% each. Other causes were Bartter syndrome, primary hypomagnesemia with hypercalciuria, severe hypothyroidism and vitamin D excess. No cause for NC was found in 12.5% patients. Specific therapy, where possible, ameliorated the biochemical aberrations, although the extent of NC remained unchanged. At a median (range) follow up of 35 (14-240) months, glomerular filtration rate (GFR) had declined from 82.0 (42-114) ml/min per 1.73 m2 body surface area to 70.8 (21.3-126.5) ml/min per 1.73 m2 body surface area (P = 0.001). Our findings confirm that, even with limited diagnostic facilities, protocol-based evaluation permits determination of the etiology of NC in most patients.

A critical appraisal of the radiological evaluation of nephrocalcinosis

BACKGROUND/AIM

The level of agreement concerning the diagnosis of nephrocalcinosis (NC) based on ultrasonography (US), computed tomography (CT) or kidney/ureter/bladder (KUB) X-ray was assessed.

METHODS

Sequences of KUB+US+CT from 62 patients, 48 with at least one exam suggesting NC and 14 with pelvicalyceal calcifications (nephrolithiasis) were reviewed twice by 3 radiologists (firstly randomized and secondly presenting KUB+US+CT of each patient together).

RESULTS

The intraobserver concordance varied from 76 to 90% for KUB, 77 to 85% for US and 82 to 89% for CT. There was a significant change in diagnosis between the 1st and 2nd reviews for observer 1 in KUB and CT, for observer 2 in US, but not for observer 3. Evaluating patients' exams together did not provide a better agreement. The highest sensitivity and specificity (92 and 89%, respectively) were only attained when 2 exams suggested NC diagnosis, being CT one of them. These enabled us to suggest that 33 out of 48 (62.5%) patients had NC (evidenced in US+CT+KUB (81.8%), US+CT (12.1%) or KUB+CT (6.1%).

CONCLUSION

The low level of concordance renders the radiological diagnosis of NC difficult. Nephrocalcinosis should be confirmed by CT combined with either US or KUB.

Diabetic and endocrine emergencies

Endocrine emergencies constitute only a small percentage of the emergency workload of general doctors, comprising about 1.5% of all hospital admission in England in 2004-5. Most of these are diabetes related with the remaining conditions totalling a few hundred cases at most. Hence any individual doctor might not have sufficient exposure to be confident in their management. This review discusses the management of diabetic ketoacidosis, hyperosmolar hyperglycaemic state, hypoglycaemia, hypercalcaemia, thyroid storm, myxoedema coma, acute adrenal insufficiency, phaeochromocytoma hypertensive crisis and pituitary apoplexy in the adult population.

Renal cortical nephrocalcinosis following acute renal failure due to polytrauma

Renal cortical nephrocalcinosis is a rare condition in which there is calcification within the renal parenchyma. This article reports a 33-year-old patient who developed acute renal failure following multiple injuries leading to hemorrhagic shock. His renal failure improved gradually, though he required dialysis support for two months. Serial ultrasounds showed a progressive decrease in renal size, and a radiograph of the abdomen showed speckled calcification in both renal areas. A CT scan of abdomen showed diffuse cortical calcification involving the entire right kidney and upper half of the left kidney.

Causes of increased renal medullary echogenicity in Turkish children

The primary disorders of 50 children with increased renal medullary echogenicity on renal ultrasound were studied; 28 girls and 22 boys aged from 1 month to 16 years were classified into four groups based on underlying disease and ultrasound findings. Group 1 was composed of 17 patients with distal renal tubular acidosis (34%); intense echoes throughout the pyramid were predominant. Group 2 consisted of 14 patients with vitamin D toxicity (28%) and an intense echogenic rim around the pyramids. Group 3 included 10 patients with different types of tubulopathies. A slight hyperechogenic rim around the sides and tip of the medullary pyramids was detected. Group 4 was made up of 9 patients with rare underlying conditions. Abdominal X-rays detected medullary calcinosis in only 12 (24%) of the total 50 patients. Ultrasonography appears to be an important tool in the early diagnosis of increased renal medullary echogenicity and medullary nephrocalcinosis.

Nephrocalcinosis in a child with autosomal dominant polycystic kidney disease and a prolapsing ectopic ureterocele

Although autosomal dominant polycystic kidney disease commonly presents in adults, it can occur in children. Usually, renal calcification in patients with autosomal dominant polycystic kidney disease is manifested as calculi or as hemorrhage into a renal cyst. An ectopic ureterocele is a well-known finding in patients with renal duplication. To our knowledge, this is the first case report of a child who had combined findings of autosomal dominant polycystic kidney disease, nephrocalcinosis, and an obstructing ectopic ureterocele.

Bone disease of primary hyperoxaluria in infancy

A patient with primary hyperoxaluria type I in infancy is reported. He had renal insufficiency, but urolithiasis was absent. Demonstration of diffuse nephrocalcinosis by renal ultrasound contributed to early diagnosis. Prolonged survival leads to extensive extrarenal oxalate deposition. Repeated skeletal surveys showed the development and the progression of severe hyperoxaluria-related bone disease. Translucent metaphyseal bands with sclerotic margins, wide areas of rarefaction at the ends of the long bones, and translucent rims around the epiphyses and the tarsal bones were signs of disordered bone growth. Bone density generally increased with time indicating progressive sclerosis due to oxalate deposition in the previously normal bone structure.

Diagnosis of anemia on computed tomography scans of the thorax

Scans of 14 patients with hemoglobin levels of 7.6 to 10.2 grams/deciliter (gm/dL) were positive for the diagnosis of anemia. All demonstrated the interventricular septum and ascending and descending aortic walls. Scans of 23 patients with hemoglobin levels of 10.5 to 12.8 gm/dL were positive for the diagnosis of anemia in 11 and negative in 12. The ascending and descending aortic walls were seen 39% and 48% of the time, respectively. Scans of 13 patients with hemoglobin levels of 12.9 to 16.0 gm/dL were negative for the diagnosis of anemia.

Fanconi-Bickel syndrome

Clinical, biochemical, functional and morphological data are presented in nine infants, children and adults, with Fanconi-Bickel syndrome. Long-term follow-up studies show severe growth retardation, partly compensated for by late onset of puberty. Glomerular filtration rate is normal or slightly decreased. Renal tubular dysfunction is characterized by a specific pattern of impaired proximal tubular transport mechanisms, with marked impairment of glucose transport. The utilization of glucose and galactose is defective, whereas fructose metabolism seems to be normal. Glycogenosis of the liver may be an epiphenomenon. Glycogen accumulation in the kidney is limited to the proximal tubule, with maximal levels in the straight part. The Fanconi-Bickel syndrome is a defined clinical entity which is distinguished from other inherited metabolic diseases by complex defects of renal tubular transport and other forms of glycogenosis.

Renal ultrasound in metabolic bone disease

Fifty-one patients aged 1 year to 56 years with metabolic bone disease underwent renal ultrasound. Medullary nephrocalcinosis was found in nine of 24 patients with X-linked hypophosphatemic rickets and is considered to be iatrogenic, related to vitamin D therapy. Another three in this group of 24 with both medullary and cortical increased renal echogenicity had suffered from repeated episodes of vitamin D intoxication and had secondary hyperparathyroidism. Nephrocalcinosis was less frequent in patients with treated vitamin D-dependent rickets or hypophosphatemic bone disease where generally smaller doses of vitamin D are given. Patients with pseudohypoparathyroidism, on small doses of vitamin D, had a normal renal ultrasound. In cystinosis and Fanconi's syndrome, the kidneys are small, echodense (both the cortex and medulla) with a tendency to cyst formation.

Renal medullary "rings": possible CT manifestation of hypercalcemia

Bilateral dense rings in the renal medulla were found on noncontrasted computed tomography in a patient with marked hypercalcemia and suspected primary hyperparathyroidism. The rings were not present on plain radiographs and were obscured on contrasted scans, and may represent occult nephrocalcinosis. Associated findings--renal insufficiency induced by hypercalcemia and interstitial nephritis--may be reversible with early recognition of this CT finding.

A variant of Bartter's syndrome. Bartter's syndrome associated with hydramnios, prematurity, hypercalciuria and nephrocalcinosis

A case of early onset Bartter's syndrome associated with hydramnios, prematurity, hypercalciuria and nephrocalcinosis is reported. A literature review of Bartter's syndrome supports the hypothesis that the findings in this infant constitute a specific variant of Bartter's syndrome inherited in an autosomal recessive mode. Fetal polyuria in Bartter's syndrome leads to hydramnios, and the excess fluid causes premature birth. This variant of Bartter's syndrome should be included in the differential diagnosis of hydramnios, especially if the woman has had previous hydramnios resulting in a perinatal death. The disorder responds to treatment with indomethacin.

Nephrocalcinosis in Bartter's syndrome. Demonstration by ultrasonography

Nephrocalcinosis in Bartter's syndrome has been recognized since 1962, but has not previously been shown in an infant with the syndrome. Ultrasonography shows striking echogenicity of the renal pyramids which appears to be a specific finding in medullary nephrocalcinosis. We suspect nephrocalcinosis will be found in many infants with Bartter's syndrome if ultrasonography is used to examine their kidneys.

Nephrocalcinosis in children

Nephrocalcinosis is an uncommon condition is childhood. The commonest cause is renal tubular acidosis, although this may not manifest itself radiographically until adolescence. Recognizing the calcification as either cortical, medullary or mixed is not always possible, but may sometimes be an aid to differentiate metabolic from vascular causes.