Faculty Bibliography

BACKGROUND: Primary hyperoxaluria (PH) is a family of rare genetic disorders affecting 1-3 per 1 million persons globally. PH causes hepatic oxalate overproduction leading to increased urinary oxalate excretion, that can result in frequent kidney stone events, progression to end-stage kidney disease (ESKD) and then other systemic morbidities.
OBJECTIVE(S): To assess the burden of PH among patients and caregivers with respect to healthcare resource utilization (HRU), quality of life (QoL) and work productivity.
METHOD(S): An IRB-approved web survey was conducted among adults (>= 18 years) with PH, and caregivers of children (< 17 years) with PH in the US. Participants were asked about their or their child's medical care, HRU and QoL. The Kidney Disease Quality of Life (KDQOL-36TM: range 0-100, higher score = better QOL) and Work Productivity and Activity Impairment (WPAI: range 0-100%, higher score = more impairment) questionnaires were administered. Descriptive statistics summarized the responses.
RESULT(S): Patient sample (n = 21) comprised 7 adults (median age 42 years) and 14 children (median age 8 years). Patients' HRU consisted of visits to nephrologists (81%), urologists (67%) and ophthalmologists (10%). 33% visited the emergency room and 29% were hospitalized. Patients on dialysis (n = 5) spent a median of 24 hours per week receiving dialysis. PH complications included kidney stone events (95%), pain (71%, nearly all moderate-severe) and nephrocalcinosis (48%). 48% of all patients experienced PH-related anxiety. Adult patients' mean KDQOL-36TM domain scores (burden, symptoms/problems and effects of kidney disease) were 38 (SD = 23), 77 (SD = 23) and 65 (SD = 26), respectively. Employed adult patients (n = 4) reported 25% presenteeism (reduced productivity at work) on average based on the WPAI. Children missed a median of 15 hours/month of school due to their PH. Caregivers (n = 13) experienced moderate-severe anxiety about the possibility of future PH-related outcomes (i.e., kidney stones [54%], kidney disease progression [62%] and ESKD [62%]) for their child. Employed caregivers (n = 9) reported 28% presenteeism on average based on the WPAI.
CONCLUSION(S): This research quantifies the burden of PH in terms of HRU, QoL and productivity for patients and caregivers. Patients experienced considerable clinical sequalae associated with PH, such as kidney stones and pain, which appear to negatively affect these outcomes. Numerous clinician visits indicated an intensive level of care. Further, PH burden goes beyond the patient, as evidenced by caregiver burden, including anxiety and impact on work productivity

PURPOSE OF REVIEW:Respiratory acidosis is commonly present in patients with respiratory failure. The usual treatment of hypercapnia is to increase ventilation. During the recent surge of COVID-19, respiratory acidosis unresponsive to increased mechanical ventilatory support was common. Increasing mechanical ventilation comes at the expense of barotrauma and hemodynamic compromise from increasing positive end-expiratory pressures or minute ventilation. Treating acute respiratory acidemia with sodium bicarbonate remains controversial. RECENT FINDINGS:There are no randomized controlled trials of administration of sodium bicarbonate for respiratory acidemia. A recent review concluded that alkali therapy for mixed respiratory and metabolic acidosis might be useful but was based on the conflicting and not conclusive literature regarding metabolic acidosis. This strategy should not be extrapolated to treatment of respiratory acidemia. Low tidal volume ventilation in acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) has beneficial effects associated with permissive hypercapnia. Whether the putative benefits will be negated by administration of alkali is not known. Hypercapnic acidosis is well tolerated, with few adverse effects as long as tissue perfusion and oxygenation are maintained. SUMMARY:There is a lack of clinical evidence that administration of sodium bicarbonate for respiratory acidosis has a net benefit; in fact, there are potential risks associated with it.

OBJECTIVE:To assess the effectiveness of an empiric approach to metabolic stone prevention. METHODS:Using medical claims from a cohort of working age adults with kidney stone diagnoses (2008-2017), we identified the subset who were prescribed thiazides, alkali therapy, or allopurinol-collectively known as preventive pharmacologic therapy (PPT). We distinguished between those who had 24-hour urine testing prior to initiating PPT (selective therapy) from those without it (empiric therapy). We conducted a survival analysis for time to first recurrence for stone-related events, including ED visits, hospitalizations, and surgery, up to 2 years after initiating PPT. RESULTS:Of 10,125 patients identified, 2744 (27%) and 7381 (73%) received selective and empiric therapy, respectively. The overall frequency of any stone-related event was 11%, and this did not differ between the 2 groups on bivariate analysis (P = .29). After adjusting for sociodemographic factors, comorbidities, medication class, and adherence, there was no difference in the hazard of a stone-related event between the selective and empiric therapy groups (hazard ratio, 0.97; 95% confidence interval, 0.84-1.12). When considered individually, the frequency of ED visits, hospitalizations, and surgeries did not differ between groups. Greater adherence to PPT and older age were associated with a lower hazard of a stone-related event (both P < .05). CONCLUSION/CONCLUSIONS:Compared to empiric therapy, PPT guided by 24-hour urine testing, on average, is not associated with a lower hazard of a stone-related event. These results suggest a need to identify kidney stone patients who benefit from 24-hour urine testing.

The Consensus Group deliberated on a number of questions concerning urine and stone analysis over a period of months, and then met to develop consensus. The Group concluded that analyses of urine and stones should be routine in the diagnosis and treatment of urinary stone diseases. At present, the 24-h urine is the most useful type of urine collection, and accepted methods for analysis are described. Patient education is also important for obtaining a proper urine sample. Graphical methods for reporting urine analysis results can be helpful both for the physician and for educating the patient as to proper dietary changes that could be beneficial. Proper analysis of stones is also essential for diagnosis and management of patients. The Consensus Group also agreed that research has shown that evaluation of urinary crystals could be very valuable, but the Group also recognizes that existing methods for assessment of crystalluria do not allow this to be part of stone treatment in many places.

We recently encountered concern about the safety of bariatric surgery for a patient with cystinuria. Bariatric surgery procedures include those that cause malabsorption, like the Roux-en-Y gastric bypass procedure, and restrictive operations, such as the sleeve gastrectomy. These procedures produce beneficial effects on health and life expectancy, though whether kidney stones are prevented, as well as promoted, is not established. Although the importance of body weight to metabolic stone activity in patients with cystinuria is not established, the patient's physicians were concerned about whether any bariatric surgery procedure would affect her ability to drink sufficient quantities of water in order to reduce stone activity. Here we report the experience of a genetically defined patient with cystinuria who underwent a gastric sleeve procedure. In the months after the procedure, she lost 45 kg, though with time she regained 23 kg of that loss. She was able to maintain a urine volume of 4.0 L per day and has had no stone recurrence.XXCopyright

Background: Hereditary Hypophosphatemic Rickets with Hypercalciuria (HHRH) is a rare monogenic disorder caused by SLC34A3 pathogenic variants, characterized by renal phosphate wasting, hypophosphatemia, hypercalciuria (HC), elevated 1,25-dihydroxyvitamin D, nephrocalcinosis (NC), and urinary stone disease (USD). Previously we reported a high prevalence of kidney cysts in CYP24A1 deficiency. Thus, in the current study, we characterized cyst presence in HHRH, another monogenic cause of HC, NC, and USD.
Method(s): Medical records from Mayo Clinic and Rare Kidney Stone Consortium research results were queried for all patients with genetically confirmed HHRH diagnosis. Clinical characteristics and imaging data are summarized in table 1.
Result(s): Among 12 patients with SLC34A3 pathogenic variants (7 monoallelic, 5 biallelic), 42% (5/12) were males. Median age at clinical presentation was 17 yrs (range 8-46) and at genetic confirmation 42 yrs (range 9-66). None had a family history of cystic kidney disease. Kidney cysts (Figure 1) were present in 75% (9/12), among whom median age at first kidney imaging and first cyst detection was 41 yrs (range 9-64). Median number of cysts per patient was 3 (range 1-23). The number of cysts >=5 mm in size was above the 97.5th percentile of an age-and sex-matched control population in 6/9 (67%). At least 2 cysts >=5 mm in size were found in 100% of children.
Conclusion(s): We found a strong association between HHRH and kidney cysts. Similarities in the biochemical profiles of HHRH and CYP24A1 deficiency suggest elevated active vitamin D, and/or HC may be potential factors in cyst formation. Further studies are needed to evaluate the role of the SLC34A3 gene in cyst formation. (Figure Presented)

Background: Potassium citrate is a mainstay of treatment to prevent recurrent calcium-containing kidney stones. However, it can increase urine pH and calcium phosphate (CaP) supersaturation (SS). HCA, extracted from Garcinia cambogia, is a potent inhibitor of calcium oxalate crystal growth in vitro and should not provide "potential base", as citrate does. Urine excretion of HCA has not been well-studied.
Method(s): We enrolled 2 groups: calcium stone formers (SF; n = 9) and non-stone forming (NSF, n = 9) controls (after excluding 2 SF and 2 NSF whose urine creatinine excretion on the 2 collections differed by more than 20%). Mean age 49.3 years. Thiazides and citrate were held for 2 weeks prior to study. Participants recorded a self-selected diet for 2 days and performed 24-hour urine collection on day 2. HCA was purchased online from Amazon.com (Super CitriMax Garcinia Cambogia); 2 caps = 900 mg of HCA. Participants took 900 mg 3 times daily orally for 7 days. Diet from days 1 and 2 was replicated on day 6 and 7 of the HCA arm of the study. 24-hour urine was collected on day 7. Urine was sent to Litholink, Inc. (Chicago, IL) for analysis. Urinary excretion of hydroxycitrate and citrate were measured using LC/MS.
Result(s): According to label, 6 pills would provide 2700 mg (13.2 mmol) of HCA per day; we measured content as 3198 mg (15.6 mmol). Citrate content is supposed to be 0, but we found 126 mg (0.66 mmol) per day. Both NSF and SF had appearance of HCA in the urine: 1.86 +/- 0.80 and 2.07 +/- 0.67 mmol/day (p = 0.56). Urine chemistry seen in Table 1. In NSF, pH and citrate did not change. In SF, pH increased, citrate did not. K went up in both groups.
Conclusion(s): Administration of HCA, a potential inhibitor of Ca stone formation, leads to significant urinary HCA excretion. Citrate excretion was not affected. Urine pH increased, suggesting some alkalinizing effect. The difference in NSF and SF may be due to the lower starting pH in SF. The effect of HCA on stone formation remains to be determined. (Figure Presented)