Faculty Bibliography

Kidney stones are listed among the complications of eating disorders; however, very few cases have been reported. We present an additional case of nephrolithiasis associated with laxative abuse, including detailed results of the patient's urine metabolic profiles, in a patient with idiopathic hypercalciuria. We review the literature and provide an explanation for the paucity of cases of nephrolithiasis associated with these disorders. Despite low urine volumes resulting from extracellular fluid volume depletion and hypocitraturia resulting from hypokalemia, both of which would tend to favor the formation of kidney stones, most patients with eating disorders are likely to be protected from stone formation by the hypocalciuric effect of extracellular fluid volume depletion and increased proximal tubular sodium reabsorption. However, patients with underlying idiopathic hypercalciuria who develop eating disorders may be at increased risk of stone formation in the setting of low urine volume and therefore high supersaturation of calcium oxalate and phosphate.

Kidney stones composed predominantly (50% or more) of calcium phosphate constitute up to 10% of all stones and 15%-20% of calcium stones, 80% of which are composed of calcium oxalate. Calcium phosphate is a minor component of up to 30% of calcium oxalate stones as well. The cause of calcium phosphate stones is often obscure but most often related to a high urine pH. Some patients with calcium phosphate stones may have incomplete renal tubular acidosis. Others have distal renal tubular acidosis characterized by hyperchloremic acidosis, hypocitraturia, and high urine pH. The use of carbonic anhydrase inhibitors such as acetazolamide, topiramate, and zonisamide leads to a similar picture. Treatment options to specifically prevent calcium phosphate stone recurrence have not been tested in clinical trials. Increases in urine volume and restriction of sodium intake to limit calcium excretion are important. Citrate supplementation is probably effective, although the concomitant increase in urine pH may increase calcium phosphate supersaturation and partially offset the inhibition of crystallization resulting from the increased urine citrate excretion and the alkali-associated reduction in urine calcium excretion. Thiazides lower urine calcium excretion and may help ensure the safety of citrate supplementation.

Tubulocystic renal cell carcinoma (TC-RCC) is a rare, typically unilateral renal tumor. We report the first case of bilateral multifocal TC-RCC associated with end-stage renal disease with cytogenetic, immunohistochemical, and ultrastructural studies. A 62-year-old man with type 2 diabetes, hypertension, and end-stage renal disease on hemodialysis had bilateral complex renal masses smaller than 3.0 cm in greatest dimension found incidentally. Follow-up imaging studies demonstrated slowly enlarging masses. The patient underwent bilateral laparoscopic radical nephrectomy. Grossly, both kidneys had multifocal, unencapsulated, sharply demarcated, gray, spongy cystic lesions (0.3-2.5 cm) in cortex and medulla. The lesions contained clear serous fluid. Microscopically, the background kidneys showed end-stage changes with glomerulosclerosis and atrophic tubules. The well-delineated cystic lesions are composed of tightly packed tubules and cysts, separated by bland fibrous stroma. The lining cells are single-layer, flattened, cuboidal to columnar, with abundant eosinophilic cytoplasm, large round to oval nuclei, and prominent nucleoli. Hobnail cells are common. No desmoplastic reaction or cellular ovarian-like stroma is present. No solid growth or papilla is seen in either kidney. Immunohistochemically, the tumor cells showed diffuse and strong positivity for AMACR, AE1/AE3, CK8/18, CD10, and PAX2; focally strong positivity for CK7, EMA, vimentin, and 34BE12; and negativity for p63 and CK20. TC-RCC was diagnosed. Fuhrman nuclear grade was 2 to 3. Pathologic stage was pT1 on both kidneys. Fluorescence in situ hybridization shows gain of chromosome 7 and chromosome 17. Transmission electronic microscopy showed 2 types of epithelial cells: type I cells reminiscent of proximal tubular cells and lining the tubules and type II cells reminiscent of distal tubular cells lining the cysts. The patient was disease-free 3 years after radiologic detection and 12 months after bilateral nephrectomy. Our studies suggest TC-RCC is closely related to papillary RCC. This tumor appears to be low-grade with no metastasis

Studies have shown that certain beverages decrease urinary lithogenicity by increasing urine citrate excretion. Diet Sunkist Orange soda had the highest concentration of citrate and total alkali content among 12 diet sodas previously assayed. We studied the effect of Diet Sunkist Orange soda consumption on urinary chemistry. Nine healthy men and women ages 26-54 years completed the study. During the control period, subjects drank 36 oz of water for 3 days in addition to their own, self-selected diet and recorded a food diary. During the study period, the subjects drank three 12-oz cans of Diet Sunkist Orange soda a day instead of water, and replicated their diets from the control period. In each period, the subjects performed 24-h urine collections on days 2 and 3. Urine chemical analysis was performed, including urinary citrate levels and pH. Diet Sunkist Orange soda increased urinary citrate excretion by 60 mg/day, which was not statistically significant (95% CI -75 to 195, P value 0.34). There was no significant change in pH from the control period to the study period (pH: 6.29-6.21; 95% CI: -0.09 to 0.25, P = 0.30). Urine volumes and creatinine excretions were not significantly different between the control and study periods. Despite the relatively high citrate and total alkali content of Diet Sunkist Orange soda, the volume consumed in this study (36 oz per day) did not provide sufficient potential base to significantly alter urine composition in healthy subjects with normocitraturia. The effect of Diet Sunkist Orange soda on urinary chemistry in patients with hypocitraturia and nephrolithiasis is not likely to have a clinically significant effect to prevent calcium or uric acid stones.

Abstract Extracorporeal treatments (ECTRs), such as hemodialysis and hemoperfusion, are used in poisoning despite a lack of controlled human trials demonstrating efficacy. To provide uniform recommendations, the EXTRIP group was formed as an international collaboration among recognized experts from nephrology, clinical toxicology, critical care, or pharmacology and supported by over 30 professional societies. For every poison, the clinical benefit of ECTR is weighed against associated complications, alternative therapies, and costs. Rigorous methodology, using the AGREE instrument, was developed and ratified. Methods rely on evidence appraisal and, in the absence of robust studies, on a thorough and transparent process of consensus statements. Twenty-four poisons were chosen according to their frequency, available evidence, and relevance. A systematic literature search was performed in order to retrieve all original publications regardless of language. Data were extracted on a standardized instrument. Quality of the evidence was assessed by GRADE as: High = A, Moderate = B, Low = C, Very Low = D. For every poison, dialyzability was assessed and clinical effect of ECTR summarized. All pertinent documents were submitted to the workgroup with a list of statements for vote (general statement, indications, timing, ECTR choice). A modified Delphi method with two voting rounds was used, between which deliberation was required. Each statement was voted on a Likert scale (1-9) to establish the strength of recommendation. This approach will permit the production of the first important practice guidelines on this topic.

OBJECTIVE: Many older adults have decreased kidney function. Practitioners should be informed that no single clinical assessment method is validated in predicting their kidney function. DATA SOURCES: Primary literature identified through MEDLINE/PubMed (1950-2010) and EMBASE (1980-2010) databases. The search was limited to English language, human subjects, and individuals 65 years of age and older. STUDY SELECTION AND DATA EXTRACTION: Research, review articles, and additional publications related to geriatric, elderly, kidney function assessment, and cystatin C. DATA SYNTHESIS: Screening and diagnosing chronic kidney disease are a challenge in older adults partially because of muscle loss and frailty. The various tools used to estimate creatinine clearance (Clcr) are not validated and may lead to under- or overdiagnosis of kidney function. The clinician must be cautious when using and interpreting results from these values. RESULTS: Estimating the glomerular filtration rate (eGFR) with either the Modification of Diet in Renal Disease (MDRD) or Cockcroft-Gault (Clcr) formulae yielded better predictions of kidney function when compared with creatinine alone, or to measured Clcr. These estimation methods should be used in clinical practice to provide a better estimation of kidney function in older adults until a more valid assessment tool becomes available. CONCLUSIONS: There is no proven valid method for eGFR in older adults; however, the CG and MDRD equations are routinely applied in clinical practice. Kidney function assessment in older adults remains a challenge, and practitioners should know their limitations.