Family History Of Renal Stones Research Articles

The Prevalence of Nephrolithiasis and Associated Risk Factors Among the Population of the Riyadh Province, Saudi Arabia.

Background and objective Kidney stones, also referred to as nephrolithiasis or renal calculi, is a condition where crystal depositions are formed within the kidney and ideally excreted from the body via the urethra with no pain; however, larger calculi may cause significant pain and require further medical assistance. The vast majority of patients who develop renal calculi form calcium stones, which are either a composition of calcium oxalate or calcium phosphate. Other types include uric acid, struvite, and cysteine. While kidney stones are one of the most significant diseases among the Saudi population, which require an acute emergency intervention to prevent serious long-term complications,there are limited studies published regarding this condition inSaudi communities. In light of this, we performed this study to assess the prevalence, incidence, and risk factors of kidney stones among the population of Riyadh, Saudi Arabia. Methods This was a cross-sectional studyconducted in Riyadh, Saudi Arabia between Augustand October 2023, aiming to estimate the prevalence and risk factors of nephrolithiasis among residents of the Riyadh province. Data were collected through an electronic questionnairein both Arabic and Englishand distributed via social media in addition to barcode handouts in various selected venues in Riyadh. The questionnaire involved 12 questions categorized into three sections. The first section obtained demographical information while the second sectioncollected data about the past medical history of the participants. Lastly, the third section aimedto assess the prevalence of nephrolithiasis among participants or any history of the condition among their families. Results Atotal of 1,043 participants were surveyed, of whom 533 were males (51.1%). The prevalence of kidney stones was reported in 98 individuals (9.4%) overall. Individuals in the age groups of 36-50, 51-60, and >60 years showed significantly more renal stone prevalence than those in younger age groups (p<0.001). The prevalencewas found to be higher in participants who were smokers, diabetic, hypertensive, and those who suffered from inflammatory bowel disease (IBD), gout, chronic kidney disease (CKD), hyperthyroidism, and hyperparathyroidism. Participants who took calcium supplements or had a positive family history of renal stones were found to have a higher prevalence of renal stones as well. However, only hypertension, gout, and family history showed any statistical significance (p<0.05). Conclusions A direct correlation was observed between hypertension, gout, positive family history, and aging and an increased prevalence of kidney stones among theinhabitants of the Riyadh province. Therefore, we encourage the local authorities to raise awareness of kidney stones and their related risk factors among the general public. Moreover, further local studies need to be conducted to gain deeper insights into kidney stone prevalence, especially pertaining to associated comorbiditiesand the pattern of the disease itself.

Prevalence and Risk Factors of Renal Stones Among the Bisha Population, Saudi Arabia.

In urolithiasis, urinary calculi are formed in the urinary system. Stone development does not initially result in any symptoms, but later renal colic, flank pain, hematuria, obstruction of urine flow, and/or hydronephrosis may indicate renal stone disease. In addition to age, gender, ethnicity, and local climate, urolithiasis can be caused by several other factors. The prevalence and recurrence rate of kidney stone disease is rising globally, while few effective treatment options currently exist. Between June and October 2022, a cross-sectional study was conducted. An electronic questionnaire subdivided into three categories was used to determine the prevalence and identify the factors that increase the likelihood of developing urolithiasis among the population in Bisha. The collected data werereviewed and analyzed via IBM Corp. Released 2012. IBM SPSS Statistics for Windows, Version 21.0. Armonk, NY: IBM Corp. A total of 1,002 participants filledoutthequestionnaire. The age of the participants ranged from 18 to over 60 years, with an average age of 26.1 ± 13.9 years. There were 451 female participants(45%), and 927 (92.5%) were Saudis. According to the participants' body mass index, 98 (9.8%) were underweight, 388 (38.7%) were normal weight, 300 (29.9%) were overweight, and 216 (21.6%) were obese. The total number of participants with urolithiasis was161(16.1%),and 420 (41.9%) had a family history of renal stones. Urolithiasis was found to be significantly associated with family history, smoking, diabetes, hypertension, hyperthyroidism, gout, and chronic kidney disease. Older age and female gender were also associated with the risk of having urolithiasis. This study found urolithiasis to be highly prevalent among the Bisha population. In terms of risk factors, body mass index, smoking, and diabetes were the most significant. Based on the findings of this study, the authors recommend more public education regarding urolithiasis and its risk factors, emphasizing the importance ofpreventingthe disease and the ways of treating urolithiasis through medical campaigns and social media.

Prevalence and Risk Factors of Urolithiasis Among the Population of Hail, Saudi Arabia.

BackgroundUrolithiasis is the formation of calculi in the urinary system. It is a public health concern worldwide that can lead to serious long-term consequences. Age, gender, dietary habits, and physical activity levels are all factors that increase the risk of urolithiasis formation. Furthermore, the presence of comorbid medical conditions such as diabetes and hypertension are other major risk factors. Among the most prominent determinants that raise the likelihood of acquiring urolithiasis is exposure to high temperatures, especially in middle-aged men. Consequently, Saudi residents are two and a half times more prone than the global average to develop urolithiasis, especially those in the Kingdom’s hottest regions.MethodologyThis cross-sectional study assessed the self-reported prevalence and non-nutritional risk factors of urolithiasis among the population of Hail, Saudi Arabia, through an electronic questionnaire. The questionnaire contained 16 questions divided into three categories. Participants’ permission was obtained before completing the questionnaire. The Statistical Package for Social Sciences (SPSS) version 22 (IBM Corp., Armonk, NY, USA) was used to analyze the data.ResultsOf the 1150 participants with a mean age of 26.3 ± 12.8 years old, nearly half were males (50.9%). Urolithiasis was detected among 158 (13.7%) participants. The following factors showed significant relation with having urolithiasis: increased age, male gender, a low level of education, diabetes, hypertension, and hyperthyroidism. A family history of renal stones was also associated with double the risk of having urolithiasis.ConclusionThe results showed a high prevalence of urolithiasis in the Hail region, with many risk factors associated with it. It is important to support and promote awareness campaigns that address the critical risk factors of urolithiasis. Further studies should be conducted to arrive at a better understanding of the association between non-nutritional risk factors and developing urolithiasis.

Risk Factors of Nephrolithiasis in a Tertiary Care Hospital in Rawalpindi: A Descriptive Cross-Sectional Study.

BackgroundNephrolithiasis (renal stones) is the most common urological disease. Its prevalence is high in every part of the world. Several factors lead to renal stone formation. In Pakistan, nephrolithiasis prevalence is also high as Pakistan is located in a region which is known as the salt belt. However, nephrolithiasis and its possible risk factors are under-researched in Pakistan.ObjectiveThis study aims to identify the risk factors for nephrolithiasis among admitted patients with renal stones. This may lead to a reduction in renal stone incidence and its allied complications by the prevention of risk factors that would have a major role in renal stone formation.Material and methodsThis descriptive cross-sectional study was performed among the 143 admitted patients with renal stones in the urology ward of Benazir Bhutto Hospital, Rawalpindi, for approximately six months from November 2021 to April 2022. Non-probability convenient sampling and developed inclusion and exclusion criteria were used for the recruitment of patients. After elaborating on the objectives, the study data were collected by interviewers through a self-structured questionnaire. Descriptive analysis was carried out using SPSS version 25.0 (IBM Corp., Armonk, NY).ResultsNephrolithiasis was more prevalent among patients who had an age group range of 15-30 years (47.55%), male gender (56.65%), illiterate educational status (53.14%), lower socioeconomic status (66.43%), inadequate intake of water (61.53%), used tap water (56.64%), a habit of daily vegetable intake (65.04%), sedentary lifestyle (51.74%), family history of renal stones (57.34%), no diabetes mellitus (62.94%), no hypertension (52.45%), and overweight (48.23%).ConclusionIn brief, the age group of 15-30 years, male gender, illiteracy, lower socioeconomic status, insufficient water intake, tap water, high vegetables, inactive lifestyle, family history of nephrolithiasis, and a high BMI all increase the risk of nephrolithiasis.

Effect of Implementing Evidence- Based Guidelines on Lifestyle Modification for Adult Patients with Renal Stone Undergoing ESWL Procedure

Introduction: Renal stone disease is one of the major health problems among urological patients, mainly the third most common urological disorder. Lifestyle modification and Extracorporeal Shock-Wave Lithotripsy (ESWL) is the first line of intervention for of upper urinary tract stones smaller than 2cm and ureter stones from 1 to 1.5 cm diameter. Aim: The aim of this study was to examine the effect of implementing evidence- based guidelines on lifestyle modification for adult patients with renal stone undergoing ESWL procedure. Methods: Random sample of Seventy patients in the age group ranging from 21-60 years old, recruited from the Urology department at the Alexandria main University Hospital, and Elnokba center for Urology in Damanhur City. Tools used for all patients underwent full history and physical examination including age, gender, family history of renal stones, past history of recurrent stone and any current medical diseases. In addition to assessing patients' knowledge regarding renal stone disease and ESWL procedure and lifestyle pattern regarding renal stones and prevention of its recurrence. Pre -Post test for patients' knowledge conducted before and after ESWL procedure with follow up for lifestyle modification within 1- and 3-months following implementation of lifestyle modifications guidelines sessions. Results: Results showed that both groups had poor knowledge level and lifestyle pattern, while after implementation all studied patients had fair knowledge and lifestyle pattern level. Results showed highly positive correlation between knowledge, and lifestyle pattern among the study group with P 0.001. Evidence based lifestyle guidelines enhance renal stone patient’s knowledge, lifestyle pattern of study group. The nurses should be trained to conduct evidence based educational lifestyle guidelines. Conclusion: Renal stone patients attending the lifestyle modification guidelines sessions demonstrated a positive significant improvement in their knowledge, as well as modifications in their lifestyle practices, all dimensions of health behaviors than those patients not attending the sessions. Therefore, a lifestyle modification guideline is considered as an effective nonpharmacological intervention in renal stone treatment and recurrence prevention. So, this study may provide a practice framework for the future development of other nursing evidence-based practice.

Renal Stones and Risk Factors in Jeddah and Riyadh.

Saudi Arabia has extremely hot climate for most of the year; this is associated with the risk of developing nephrolithiasis. This retrospective research aimed to investigate the current prevalence, manifestation, mode of treatment, and risk factors of renal stones in Jeddah and Riyadh, Saudi Arabia. A cross-sectional study was conducted from November 2018 to June 2019 at King Abdulaziz University Hospital, Jeddah, Saudi Arabia. This study included 1031 participants aged ≥18 years from Jeddah (n=652, 63.3%) and Riyadh (n=379, 36.8%). Data were expressed as mean ± standard deviation (minimum-maximum) or number (%). Comparisons between patients with and without renal stones were made using the Chi-square test and unpaired Student's t-test as appropriate. The odds ratio (OR) with a 95% confidence interval (95% CI) was determined for the risk factors of renal stones. The prevalence of renal stones was 16.9% among the participants. A significantly high risk for renal stones was associated with male sex (2.96; 95% CI: 2.08-4.20, P = 0.0001) and age group of 34-40 years (OR: 1.44; 95% CI: 1.005-2.103, P = 0.047). Hypertension was more common in patients with renal stones than those without renal stones (9.5% vs.4.6%, P = 0.013). The percentage of patients who took diuretics was significantly higher among those with renal stones than among those without renal stones (11.2% vs. 3.5%, P = 0.001). Of the 169 patients with renal stones, 58.0% had a positive family history of renal stones, and 23.7% had a history of urinary tract infections (UTIs). The symptoms of renal stones were pain (86.4%), hematuria (11.2%), fever (2.4%), and others (0.6%). Of all the patients, 43.8% took medication. For most patients, the stones passed spontaneously (67.5%), while 23.7% underwent lithotripsy, and 1.5% received stents. In this study, we found a higher prevalence of renal stones two major cities in Saudi Arabia in Jeddah and Riyadh, at 16.4%. Risk factors included male sex and age group of 34-40 years. A significant number of patients with renal stones have a family history of renal stones and a history of UTI. Loin pain and hematuria were the two major clinical presenting symptoms for renal stones. In the majority of patients, the renal stones passed spontaneously without the need for lithotripsy or surgery.

Infra-vesical Obstructive Uropathy Secondary to Benign Prostatic Enlargement

Background: Urinary tract obstruction is a common clinical problem. The obstruction of the urinary flow may be acute or chronic, partial or complete, unilateral or bilateral, and may occur at any site of the urinary tract. Aim: Imaging of complication of obstructive uropathy below the level of urinary bladder in adult male patient with enlarged prostate. We put urethral catheter to relief symptoms. Serum creatinine, PSA & urine analysis were within normal & the general condition was stabilized. Methods: Bedside ultrasound is used to scan the upper & lower urinary tract. We report a case of a male patient aged 50 y old, diabetic & hypertensive & complained of sudden onset of bilateral flank pain & urine retention. It is preceded by LUTS including: frequency, nocturia, dysuria & incomplete evacuation of bladder since 1 month. No previous surgical operation. No family history of renal stones. Results: Ultrasound is a valuable diagnostic tool in obstructive uropathy. Conclusion: Scan of pre-voiding & post-voiding renal tract is very important to realize the etiology & the level of urinary tract obstruction.

The Prevalence of a Clinically Silent Nephrolithiasis in Baghdad Population: An Initial Ultrasound Screening Study From Iraq

Abstract- Asymptomatic or clinically silent kidney stones are possibly serious because, in their expected passage, they may cause infection, obstruction and renal impairment. The purpose of this study was to determine the prevalence of silent kidney stones in a sample of Baghdad population and consider how this value could affect the justification for a screening system. To our best knowledge, this is the first study of its kind conducted in Iraq. We investigated 714 consecutive patients who sustained an abdominal ultrasound at our hospital with further kidney screening. All these patients did not have clinical signs and symptoms of nephrolithiasis. Age, sex, the indication for ultrasound, the size, side, and the number of the discovered stones were recorded. We observed silent kidney stones in 3.4% of patients. Males were stone carriers mostly. Stones were detected more in the left kidney than the right. Distinctly, multiple stones and stones of a large size were minimally seen. We conclude that the prevalence of clinically silent nephrolithiasis of 3.4% does not support a global screening. Yet, this screening may be justified in a limited pattern for those male subjects higher than 50 years, having a positive family history of renal stones, and their socioeconomic status is granted.

A case-control study on environmental and biological risk factors for renal calculi persisting in a coastal Union Territory, India.

Background and Objectives:Renal stone disease is a common disorder of the urinary tract and also a significant problem because of incidence, recurrence, and severe consequences. The complex pathogenetic mechanisms of renal stone formation involve both biologic and environmental risk factors. The present study was performed to identify the role of these parameters among renal stone patients and normal individuals from a coastal union territory region in South India.Methods:The authors conducted a case–control study of renal stone disease among outpatient department patients more than 30 years of age using systematic random sampling procedure with 100 study participants (50 subjects for each group). A questionnaire to explore some relevant history as well as to note general examination findings was used along with a house visit to collect a sample of water. Analysis was undertaken using appropriate statistical techniques.Results:The study showed statistically significant association for renal stones with female sex, illiteracy, body mass index (BMI) (>25 kg/m2), sodium (>50 mg/L), water consumption (<1.5 L/day), water source being borewell, consuming soft drink, sedentary work, and family history of renal stones. The adjusted odds ratios (ORs) were significantly higher for consuming soft drink (OR: 8.19; 95% confidence interval: 1.99–33.69), sedentary work (10.01; 1.27–78.91), and water consumption < 1.5 L/day (7.73; 2.24–26.69).Interpretation and Conclusions:We conclude that in this part of India, female gender, illiteracy, high BMI, high sodium in drinking water, inadequate water consumption, borewell drinking water, soft-drink consumption, sedentary work, and family history of renal stones can lead to a significant increase in the risk of renal stone disease.

Epidemiological characteristics of childhood urolithiasis in Morocco

ObjectivesDue to the increase observed in the incidence of pediatric urolithiasis in the world, and the scarcity of studies of this pathology in Morocco, we assessed whether epidemiological characteristics of pediatric urolithiasis have a similar profile like in developed countries further we tried to assess the prevalence of this pathology among children in Hassan II University-Hospital of Fez. Subjects and methodsBetween January 2003 to November 2013, 104 pediatric patients with urolithiasis were presented to Hassan II University-Hospital of Fez. Eighty one were boys and 23 girls. Patients were referred from different regions of Moroccan states. ResultsOut of 104 children diagnosed with urolithiasis, 5 patients with positive family history of renal stones, and 12 were recurrent (12%).Their age varied between 8 months and 15 years old, with a mean age of 7.86±4. The sex ratio was 3.5:1 boys to girls. Clinical presentations were dominated by micturition disorder (59%), abdominal or flank pain (28%), nephritic colic (22%), hematuria (22%) and urinary tract infection (13%). Stones were located in the upper urinary tract in 62.5% of cases.Stones were treated by surgery in 89 cases (89%), and with ESWL in only 2 cases (2%).Over these years of study, a prevalence of 0.83% of childhood urolithiasis was calculated. ConclusionsThis preliminary study represents only a region of the country, so more epidemiological analyses should be done.Stone analysis should be performed more frequently, and patients must be presented at earlier stages, before any development of renal failure.

Incidence of kidney stones with topiramate treatment in pediatric patients

We ran this study to assess the incidence of nephrolithiasis in a group of children on topiramate (TPM) therapy for at least 1 year. In this retrospective observational surveillance study, we reviewed the medical charts of children on TPM for at least 1 year seen at the pediatric neurology department during the period from 2005 to 2010 at King Fahad Medical City. Children with a normal baseline ultrasound report were included. Follow-up ultrasound reports after at least 1 year were collected. However, patients with any evidence of chronic illness or medications that may affect the kidney functions in addition to those who are not compliant with the prescribed dose were excluded. Family history of renal stones, symptoms suggestive of urologic disorders, and comorbidities were recorded. Medical charts of 96 children on TPM with a mean age of 6.9 (±3.8) years were reviewed; 52 (54.2%) of the children were male. The follow-up ultrasound showed that five children (5.2%) had developed kidney stones. The occurrence of kidney stones was found in four female patients (80%) versus one male (20%) (p > 0.05). Long-term use of TPM may result in increased incidence of asymptomatic kidney stones in the pediatric population. Hence, routine baseline and follow-up ultrasound of the urinary system should be recommended during the use of TPM in children.

Familial multiple endocrine neoplasia type I: the urologist is first on the scene

To study the urological manifestations of familial multiple endocrine neoplasia type 1 (MEN-1). The study included 26 adults (median age 38.5 years, range 18-80) from two unrelated MEN-1 pedigrees. In 15 of the patients the diagnosis was confirmed by genetic analysis, while in the rest the diagnosis was based on clinical criteria combined with genealogy data. Urolithiasis associated with primary hyperparathyroidism was present in 65% of MEN-1 patients and in 77% of those who were symptomatic. In 68% of patients complications of urolithiasis (renal/ureteric colic, urinary tract infection) were the presenting clinical manifestations of MEN-1, whereas in 50% they constituted the only clinical manifestation of the syndrome. The mean time from the onset of symptoms of urolithiasis to the diagnosis of the polyendocrinopathy was 17.2 years. Initial failure to recognize the presence of MEN-1 in patients with primary hyperparathyroidism led to conservative parathyroid surgery, with subsequent relapse of the hyperparathyroidism, requiring re-operation. Serious renal morbidity included one case of pyonephrosis necessitating nephrectomy. While urolithiasis was a cardinal clinical manifestation of MEN-1, there was otherwise considerable phenotypic polymorphism, even among patients bearing the same MEN1 gene mutation. In patients with familial MEN-1 the complications of urolithiasis are the commonest presenting clinical manifestations and the cause of significant morbidity. In the presence of a family history of renal stones, appropriate investigations may lead to the timely diagnosis of this important, albeit rare, disorder.

Pediatric urolithiasis in Kuwait.

In this retrospective study, 31 Kuwaiti children with renal stones were reviewed between January 1996 and September 2000. Male to Female ratio was 2.1:1 with a mean age at presentation of 38 months. Family history of renal stones was reported in 58%. Stones were localized to the kidneys in 74.1%, to ureters in 6% and to the bladder in 9.6%. Bilateral stones were found in 64.5%. Clinical manifestations included: hematuria in 70.9%, passage of stones in 64.5%, abdominal pain in 41.9%, urinary tract infections in 29%, sterile pyuria in 22.9% and urine retention in 16%. Causes of stone formation included hypercalciuria in 38.7%, hyperoxaluria in 19.3%, cystinuria in 12.9%, xanthinuria in 12.9%, urinary tract infection in 3.2%, obstruction in 9.6% and idiopathic in 3.2%. In conclusion, lithogenic metabolic causes were found to be the major predisposing factors to stone formation among Kuwaiti children whereas diet and environmental factors played a trivial role.

Familial Aggregation of Renal Calcium Stone Disease

The question of a familial predisposition towards stone formation in primary nephrolithiasis has not been explored completely. In a sample of 214 calcium stone patients, and 428 age and sex-matched controls we observed a higher frequency of stones among the first degree relatives of stone patients compared to the relatives of controls.A family history of renal stones was more common among the female (45 per cent) than among the male patients (31 per cent). There was no relationship between family history of renal stones, and abnormal calcium and oxalate excretion rates. A significant association between a family history and a higher urinary pH was observed among the female calcium stone patients. A genetic defect in urinary acidification with variable expressivity might be associated with a high frequency of stone formation. Moreover, uric acid excretion was higher in male stone patients with a family history of stones. Finally, the parents and siblings of the renal stone patients were affected more by calculi than were the corresponding relatives of their spouses.

Some features of paediatric urolithiasis in a group of Syrian children.

A group of 28 Syrian children (19 males and 9 females; age ranging from 2.5 to 12 years) were diagnosed clinically and radiologically to have upper urinary tract stones. The commonest presentations were renal colic, vomiting, haematuria, pyrexia and vague abdominal pain. Family history of renal stones was present in 21% of cases. Haematological picture and chemical analysis of blood were within the normal limits for their age and sex. Urine analysis, however, showed significantly marked increase in the 24-hour excretions of calcium and uric acid. Microscopic examination showed haematuria and pyuria in 72% of the children with urolithiasis. Chemical analysis of removed stones revealed that most of them were mixed stones of calcium oxalate and urate or/and phosphate. Pure stones of calcium oxalate or calcium phosphate were less common. Radiologically, about 95% of all stones were demonstrated by plain X-ray, while 5% only after IVP.

Family history of renal stones in recurrent stone patients.

A survey was carried out on the family history of renal stones among 380 patients in an out-patient stone clinic, most of whom had experienced frequent recurrences. In 55.4% of patients at least one first-degree relative had experienced renal stones. A positive family history was more common in females (64.7%) than in males (51.0%) and was particularly apparent in those who had multiple recurrences. It was also significantly more common in female patients with evidence of renal tubular defects (incomplete forms of renal tubular acidosis). Among the ordinary stone patients 18% of the fathers and 8% of the mothers had also formed renal stones. The corresponding figures for female stone patients with renal tubular defects were 40 and 33% respectively. These findings indicate that tubular dysfunction could be an inherited trait that predisposes to the formation of renal stones. Hypercalciuria or hyperuricosuria was not over-represented among stone formers with a positive family history.

Family History of Renal Stones in a Population Study of Stone-formers and Healthy Subjects

Information on the family history of renal stone disease was obtained from over 2500 middle-aged men in a general health survey. A family history of stones was significantly more common among the stone-formers than amoung the controls, largely due to an increased frequency of stones among the fathers and brothers of the propositi. This study thus supports previous suggestions that genetic factors play a part in the predisposition to stone formation. An increased tendency was also noted, however, among the wives of those whose relatives had stones, which suggests that environmental factors are involved. Subjects with a family history of renal stones did not exhibit any particular characteristics in their laboratory profiles, but they appeared to be more prone to develop early and frequent recurrences.

Evidence for a renal PO4 leak in patients with calcium nephrolithiasis.

Patients having recurrent calcium oxalate and/or apatite nephrolithiasis demonstrate hypophosphatemia but normal rates of glomerular filtration and urinary phosphate excretion in comparison to healthy adults without a personal or family history of renal stones. These observations suggest that stone formers have a defect in net renal tubular reabsorption of filtered PO4. We compared the responses of stone formers and of normal subjects to dietary PO4 deprivation in order to assess whether the lower serum PO4 levels in stone formers are the result of a renal PO4 leak or a resetting of the level at which the kidneys regulate serum PO4 levels. Nine male stone formers and 13 healthy male adults were studied while eating normal diets and then while eating a liquid diet providing only 2 mmol PO4/day for 3 days. (Females were not studied because serum PO4 falls in healthy women deprived of dietary PO4.) During control, serum PO4 averaged 1.30 ± 0.06 SE mmol/L in normals and 1.28 ± 0.06 mmol/L in stone formers, values that are not different for these small groups. Control UPO4V averaged 32.4 ± 1.8 mmol/day in normals and 27.9 ± 2.3 mmol/day in the stone formers. These means are also not significantly different. However, after 3 days of dietary phosphate deprivation, mean serum PO4 concentrations declined by −0.18 ± 0.04 mmol/L in stone formers (p < 0.01) but did not change from control in the normal men (+0.05 ± 0.05 mmol/L; NS). The mean change from control in serum PO4 concentrations in stone formers was also significantly different from the change in normals (p < 0.01). In addition, UPO4V on the 3rd day of dietary PO4 deprivation fell to only 4.5 ± 1.0 mmol/day in stone formers, a value significantly higher than that observed in the normal men of 1.8 ± 0.5 mmol/day (p < 0.02). The observations that stone formers fail to achieve normal maximum renal PO4 conservation and demonstrate a fall in serum PO4 concentration in response to dietary PO4 deprivation provides further support for the view that these patients have a renal PO4 leak. The mechanism of such a leak remains to be determined. The suppression of PTH secretion that accompanies dietary PO4 deprivation in normal subjects could be impaired or delayed among stone formers. Alternatively, stone formers may have a defect in a PTH-independent renal tubular PO4 transport process.