Hypokalemia Induced Partial Nephrogenic Diabetes Insipidus: A Case Report.

ABSTRACT: Diabetes insipidus is a condition characterised by a large volume of diluted urine production and increased thirst. In this case report, a 49-year-old gentleman presented with 3 months of polyuria and polydipsia. He had a repeated history of hypokalemia. On the evaluation of polyuria and polydipsia, he was diagnosed with partial nephrogenic diabetes insipidus based on his inability to concentrate urine after a water deprivation test and his less than 50% response to exogenous desmopressin. On the evaluation of recurrent hypokalemia, the investigation reports met biochemical criteria for the diagnosis of Gitelman syndrome. He was encouraged to increase his fluid intake as required, and potassium chloride supplementation relieved his symptoms. This case report demonstrates the reversibility of nephrogenic diabetes insipidus with a correction of hypokalemia.

Acute lymphoblastic leukemia with nephrogenic diabetes insipidus as the first symptom: a case report.

BACKGROUND: Acute lymphoblastic leukemia is the most common pediatric malignancy, characterized by fever, anemia, hemorrhage, and symptoms brought on by blasts infiltrating organs. CASE PRESENTATION: This is a case report of a 9-year-old Asian patient with acute lymphoblastic leukemia who presented with polyuria alone as a presenting feature without any other clinical manifestation; primary renal disease or inherited metabolic disease was highly suspected. However, the water deprivation test and water deprivation pressurization test suggested nephrogenic diabetes insipidus, and the renal biopsy displayed diffuse lymphocytic infiltration in the renal interstitium. Bone marrow aspiration was performed immediately, and a comprehensive diagnosis of B-lymphoblastic leukemia was finally made. CONCLUSIONS: Renal infiltration with leukemic blasts mostly remains asymptomatic, but our case suggests that it can present with nephrogenic diabetes insipidus. This case fully demonstrates that the presentation of extramedullary infiltration in acute lymphoblastic leukemia is varied. When the patient has renal diabetes insipidus as the first symptom, the possibility of hematological tumor infiltration should be considered when finding the cause, and timely bone marrow cytology should be performed.

PDE5 inhibitor potentially improves polyuria and bladder storage and voiding dysfunctions in type 2 diabetic rats.

PURPOSE: Bladder dysfunction associated with type 2 diabetes mellitus (T2DM) includes urine storage and voiding disorders. We examined pathological conditions of the bladder wall in a rat T2DM model and evaluated the effects of the phosphodiesterase-5 (PDE-5) inhibitor tadalafil. MATERIALS AND METHODS: Male Otsuka Long-Evans Tokushima Fatty (OLETF) rats and Long-Evans Tokushima Otsuka (LETO) rats were used as the T2DM and control groups, respectively. Tadalafil was orally administered for 12 weeks. Micturition behavior was monitored using metabolic cages, and bladder function was evaluated by cystometry. Bladder blood flow was evaluated by laser speckle imaging, and an organ bath bladder distention test was used to measure adenosine triphosphate (ATP) release from the bladder urothelium. The expression levels of vesicular nucleotide transporter (VNUT), hypoxia markers, pro-inflammatory cytokines and growth factors in the bladder wall were measured using real-time polymerase chain reaction and enzyme-linked immunosorbent assay. Bladder wall contractions in response to KCl and carbachol were monitored using bladder-strip tests. RESULTS: With aging, OLETF rats had higher micturition frequency and greater urine volume than LETO rats. Although bladder capacity was not significantly different, non-voiding bladder contraction occurred more frequently in OLETF rats than in LETO rats. Bladder blood flow was decreased and ATP release was increased with higher VNUT expression in OLETF rats than in LETO rats. These effects were suppressed by tadalafil administration, with accompanying decreased HIF-1α, 8-OHdG, IL-6, TNF-α, IGF-1, and bFGF expression. The impaired contractile responses of bladder strips to KCl and carbachol in OLETF rats with aging were restored by tadalafil administration. CONCLUSIONS: The T2DM rats had polyuria, increased ATP release induced by decreased bladder blood flow and impaired contractile function. PDE5 inhibition improved these changes and may prevent T2DM-associated urinary frequency and bladder storage and voiding dysfunctions.

Primary Polydipsia in a Toddler: A Rare Case.

Primary polydipsia (PP) is a rare but significant clinical entity in pediatric patients. Here, we present the case of a 16-month-old female referred to our center due to recurrent episodes of electrolyte imbalances. Initially admitted for management of a viral illness, she experienced unexplained electrolyte disturbances, prompting subsequent admissions marked by similar disruptions. Despite stabilization and discharge, her condition persisted. Pre-referral laboratory findings revealed significant electrolyte abnormalities alongside polyuria symptoms. Investigations unveiled a history of frequent heavy wet diapers and increased thirst. Further tests including a water deprivation test excluded diabetes insipidus. Following the restriction of water intake and careful monitoring, her condition markedly improved. This case emphasizes the importance of thorough evaluation in persistent electrolyte imbalances in toddlers, highlighting the role of polyuria as a contributing factor and the efficacy of targeted interventions in managing such cases.

Salt-losing nephropathy associated with supraventricular arrhythmia.

We present a case of a young man with a new-onset supraventricular arrhythmia accompanied by polyuria and natriuresis with subsequent renal salt-wasting causing hypovolemic hyponatremia. Resolution of the electrolyte imbalance occurred only after successful atrial flutter ablation.

Establishment and validation of a predictive nomogram for polyuria during general anesthesia in thoracic surgery.

BACKGROUND: To develop and evaluate a predictive nomogram for polyuria during general anesthesia in thoracic surgery. METHODS: A retrospective study was designed and performed. The whole dataset was used to develop the predictive nomogram and used a stepwise algorithm to screen variables. The stepwise algorithm was based on Akaike's information criterion (AIC). Multivariable logistic regression analysis was used to develop the nomogram. The receiver operating characteristic (ROC) curve was used to evaluate the model's discrimination ability. The Hosmer-Lemeshow (HL) test was performed to check if the model was well calibrated. Decision curve analysis (DCA) was performed to measure the nomogram's clinical usefulness and net benefits. P < 0.05 was considered to indicate statistical significance. RESULTS: The sample included 529 subjects who had undergone thoracic surgery. Fentanyl use, gender, the difference between mean arterial pressure at admission and before the operation, operation type, total amount of fluids and blood products transfused, blood loss, vasopressor, and cisatracurium use were identified as predictors and incorporated into the nomogram. The nomogram showed good discrimination ability on the receiver operating characteristic curve (0.6937) and is well calibrated using the Hosmer-Lemeshow test. Decision curve analysis demonstrated that the nomogram was clinically useful. CONCLUSIONS: Individualized and precise prediction of intraoperative polyuria allows for better anesthesia management and early prevention optimization.

Not all ketosis is type 1 - remember Flatbush.

A 35-year-old otherwise healthy gentleman from Togo, was referred as a 'walk-in' to our clinic with polyuria and polydipsia, and a glycated haemoglobin (Hba1c) of 119 mmol/mol (13.1%). The patient also noted 5kg weight loss over a short span of time. He had a significant family history of Type 2 Diabetes Mellitus (T2DM). Initial blood tests revealed a blood glucose of 22.84 mmol/L, with positive ketones (1.2 mmol/L). Urinalysis showed glycosuria (1000 mg/dL) but was negative for nitrites and white cells. Renal, liver and thyroid function tests were all within normal limits. He had mild metabolic acidosis.

An adolescent male with persistent urinary symptoms.

An 11-year-old male child who presented with increased frequency of urination, thirst and feeling of incomplete void was initially diagnosed with diabetes mellitus (DM) based on elevated blood sugar. Polyuria and polydipsia were confirmed even after normalisation of blood sugar. A standardised water deprivation test showed presence of central diabetes insipidus (DI) and patient was started on desmopressin. Presence of DM and DI led to suspicion of DIDMOAD/Wolfram syndrome and ophthalmic examination confirmed bilateral optic atrophy. Despite treatment for DM and DI the urinary complaints persisted, and ultrasound showed persistent bilateral hydronephroureterosis. Bladder workup including voiding cystourethrography (VCUG) and urodynamic study reported thickened trabeculated bladder wall along with overactivity, poor compliance and high bladder pressure. Bladder dysfunction has been documented to be associated with Wolfram syndrome and often may lead to chronic kidney disease which can be prevented by early diagnosis and appropriate management. The case highlights the need for comprehensive evaluation of children with urinary symptoms.

How to improve ChatGPT performance for nephrologists: a technique guide.

BACKGROUND: The integration of ChatGPT into nephrology presents opportunities for enhanced decision-making and patient care. However, refining its performance to meet the specific needs of nephrologists remains a challenge. This guide offers a strategic roadmap for advancing ChatGPT's effectiveness in nephrological applications. METHODS: Utilizing the advanced capabilities of GPT-4, we customized user profiles to optimize the model's response quality for nephrological inquiries. We assessed the efficacy of chain-of-thought prompting versus standard prompting in delineating the diagnostic pathway for nephrogenic diabetes insipidus-associated hypernatremia and polyuria. Additionally, we explored the influence of integrating retrieval-augmented generation on the model's proficiency in detailing pharmacological interventions to decelerate the progression from chronic kidney disease (CKD) G3 to end-stage kidney disease (ESKD), comparing it to responses without retrieval-augmented generation. RESULTS: In contrast to the standard prompting, the chain-of-thought method offers a step-by-step diagnostic process that mirrors the intricate thought processes needed for diagnosing nephrogenic diabetes insipidus-related hypernatremia and polyuria. This begins with an initial assessment, notably including a water deprivation test. After evaluating the outcomes of this test, the approach continues by identifying potential causes. Furthermore, if a patient's history suggests lithium usage, the chain-of-thought model adjusts by proposing a more customized course of action. In response to "List medication treatment to help slow progression of CKD G3 to ESKD?", GPT-4 only provides a general summary of medication options. Nevertheless, a specialized GPT-4 model equipped with a retrieval-augmented generation system delivers more precise responses, including renin-angiotensin system inhibitors, sodium-glucose cotransporter-2 inhibitors, and mineralocorticoid receptor antagonists. This aligns well with the 2024 KDIGO guidelines. CONCLUSIONS: GPT-4, when integrated with chain-of-thought prompting and retrieval-augmented generation techniques, demonstrates enhanced performance in the nephrology domain. This guide underscores the transformative potential of chain-of-thought and retrieval-augmented generation techniques in optimizing ChatGPT for nephrology, and highlights the ongoing need for innovative, tailored AI solutions in specialized medical fields.

Arginine vasopressin deficiency: diagnosis, management and the relevance of oxytocin deficiency.

Polyuria-polydipsia syndrome can be caused by central diabetes insipidus, nephrogenic diabetes insipidus or primary polydipsia. To avoid confusion with diabetes mellitus, the name 'central diabetes insipidus' was changed in 2022 to arginine vasopressin (AVP) deficiency and 'nephrogenic diabetes insipidus' was renamed as AVP resistance. To differentiate the three entities, various osmotic and non-osmotic copeptin-based stimulation tests have been introduced in the past decade. The hypertonic saline test plus plasma copeptin measurement emerged as the test with highest diagnostic accuracy, replacing the water deprivation test as the gold standard in differential diagnosis of the polyuria-polydipsia syndrome. The mainstay of treatment for AVP deficiency is AVP replacement with desmopressin, a synthetic analogue of AVP specific for AVP receptor 2 (AVPR2), which usually leads to rapid improvements in polyuria and polydipsia. The main adverse effect of desmopressin is dilutional hyponatraemia, which can be reduced by regularly performing the so-called desmopressin escape method. Evidence from the past few years suggests an additional oxytocin deficiency in patients with AVP deficiency. This potential deficiency should be further evaluated in future studies, including feasible provocation tests for clinical practice and interventional trials with oxytocin substitution.

The relation between autophagy modulation by intermittent fasting and aquaporin 2 expression in experimentally induced diabetic nephropathy in albino rat.

Polyuria is an early sign of diabetic nephropathy (DN) that produces dehydration in diabetic patients. This could be caused by alteration of renal aquaporin 2 (AQP2) expression. This study aimed to describe the relation between autophagy modulation via intermittent fasting (IF) and renal AQP2 expression and polyuria in case of DN. We divided the rats into control, DN and IF groups. After 2 and 4 weeks of diabetes induction, blood glucose (BG), serum creatinine (Scr), urine volume, and 24 hours urine protein (UP) were examined. Diabetic nephropathy histopathological index (DNHI) was calculated to evaluate histopathological changes. Immunohistochemistry and real-time PCR were performed to measure the levels of AQP2 and the autophagy marker; LC3 in kidney tissue. DNHI was correlated to the PCR and immunoexpression of AQP2 and LC3. Intermittent fasting significantly decreased the BG, Scr, urine volume, 24 hours UP, and DNHI as compared diabetes. Diabetes significantly elevated the immunoreactivity and mRNA expression levels of AQP2 and LC3 as compared to the control. However, the IF decreased AQP2 and stimulated autophagy in cyclic fashion. Our data revealed significant positive correlations between AQP2 and LC3 at the level of immunoexpression and mRNA at 2nd weeks. Taken together, these data showed that autophagy stimulation didn't regulate AQP2 expression in case of diabetic nephropathy, however IF decreased polyuria through improvement of glycemic state.

Electroencephalography-based investigation of the effects of oral desmopressin on improving slow-wave sleep time in nocturnal polyuria patients (the DISTINCT study): A single-arm, open-label, single-assignment trial.

AIMS: To investigate changes in subjective and objective sleep quality after desmopressin administration in patients with nocturia due to nocturnal polyuria (NP) using electroencephalography (EEG) and the Pittsburgh sleep quality index (PSQI). METHODS: Twenty male patients (≥65 years old) with NP participated in this study. The inclusion criteria were nocturnal frequency ≥ 2, NP index (NPi) ≥ 0.33, first uninterrupted sleep period (FUSP) ≤ 2.5 h, serum sodium concentration ≥ 135 mEq/L, and estimated glomerular filtration rate ≥ 50 mL/min/1.73 m2. Participants were given 50 µg of desmopressin to be taken orally once daily before bed. The primary endpoint was the change in the duration of slow-wave sleep (nonrapid eye movement sleep stages 3 and 4), as evaluated by EEG 28 days from the baseline. The visual analog scale (VAS) was used as an additional indicator of sleep quality. RESULTS: Analysis of data from 15 participants (median age: 74.0 [70.5, 76.0] years) revealed that from before to after desmopressin administration, significant decreases occurred in the median nocturnal frequency (3.0 [2.0, 4.0] to 1.5 [1.0, 2.0]) and NPi (0.445 [0.380, 0.475] to 0.360 [0.250, 0.430]). Furthermore, FUSP was significantly prolonged from 120.0 (94.0, 150.0) min to 210.0 (203.8, 311.3) min. Although the VAS scores improved, slow-wave sleep duration and the PSQI global score showed no significant differences (68.50 [47.50, 75.50] and 48.00 [38.00, 66.50]; 5.0 [5.0, 10.0] and 7.0 [5.0, 9.0] min, respectively). CONCLUSION: Oral administration of 50 µg desmopressin improved nocturnal frequency and FUSP in older individuals with NP but did not significantly enhance sleep quality. In older adults, decreased nighttime urinary frequency may enhance quality of life; however, its influence on objective sleep quality may be limited.

Biological Variation Estimates for Plasma Copeptin and Clinical Implications.

BACKGROUND: Plasma copeptin measurement is useful for the differential diagnoses of polyuria-polydipsia syndrome. It has also been proposed as a prognostic marker for cardiovascular diseases. However, limited information is available about the within- (CVI) and between-subject (CVG) biological variation (BV). This study presents BV estimates for copeptin in healthy individuals. METHODS: Samples were collected weekly from 41 healthy subjects over 5 weeks and analyzed using the BRAHMS Copeptin proAVP KRYPTOR assay after at least 8 h of food and fluid abstinence. Outlier detection, variance homogeneity, and trend analysis were performed followed by CV-ANOVA for BV and analytical variation (CVA) estimation with 95% confidence intervals. Reference change values (RCVs), index of individuality (II), and analytical performance specification (APS) were also calculated. RESULTS: The analysis included 178 results from 20 males and 202 values from 21 females. Copeptin concentrations were significantly higher in males than in females (mean 8.5 vs 5.2 pmol/L, P < 0.0001). CVI estimates were 18.0% (95% CI, 15.4%-21.6%) and 19.0% (95% CI, 16.4%-22.6%), for males and females, respectively; RCVs were -35% (decreasing value) and 54% (increasing value). There was marked individuality for copeptin. No result exceeded the diagnostic threshold (>21.4 pmol/L) for arginine vasopressin resistance. CONCLUSIONS: The availability of BV data allows for refined APS and associated II, and RCVs applicable as aids in the serial monitoring of patients with specific diseases such as heart failure. The BV estimates are only applicable in subjects who abstained from oral intake due to the rapid and marked effects of fluids on copeptin physiology.

Successful Treatment of Lithium-Induced Nephrogenic Diabetes Insipidus with Celecoxib: A Promising Therapeutic Option.

BACKGROUND Nephrogenic diabetic insipidus (NDI) poses a challenge in clinical management, particularly when associated with lithium ingestion. Non-selective non-steroidal anti-inflammatory drugs (NSAIDs) have been widely used for the treatment of numerous diseases worldwide, including NDI. However, many studies have reported the diverse adverse effects of long-term use of non-selective NSAIDs. Celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, is a better drug to relieve pain and inflammation in terms of long-term safety and efficacy than non-selective NSAIDs. Nevertheless, there are few reports describing the effectiveness of celecoxib in treating NDI. CASE REPORT We report a case of a 46-year-old woman with schizophrenia who presented with severe hypernatremia and refractory polyuria due to lithium-induced NDI. Cessation of lithium ingestion and traditional treatments, including trichlormethiazide and desmopressin, yielded minimal improvement in her hypernatremia and polyuria. Her sodium level needed to be strictly controlled with the infusion of dextrose 5% in water. Given the safety of celecoxib, we decided to initiate celecoxib as the treatment of lithium-induced NDI instead of indomethacin. Notably, the introduction of celecoxib led to a substantial and sustained amelioration of polyuria and hypernatremia without any celecoxib-associated adverse effects. Even after transfer to another hospital, stability in serum sodium levels persisted with celecoxib. CONCLUSIONS We presented a case of lithium-induced NDI successfully treated with celecoxib, a selective COX-2 inhibitor. To the best of our knowledge, this is the first reported case of successful treatment of lithium-induced NDI with celecoxib, and suggests celecoxib is a viable therapeutic option warranting further exploration. Physicians should consider its use when faced with the challenging management of lithium-induced NDI.

Long-term safety of desmopressin orally disintegrating tablets in men with nocturia due to nocturnal polyuria: Interim results of a specified drug use-results survey in Japan.

OBJECTIVES: This interim report presents the 12-week results of a post-marketing surveillance evaluating the safety of desmopressin orally disintegrating tablets 25 and 50 µg in Japanese men with nocturia due to nocturnal polyuria. METHODS: Of the planned study population of 1000 Japanese men receiving desmopressin for the first time for nocturia due to nocturnal polyuria, 971 cases were enrolled. In this interim analysis, 9 cases, including 6 registry violations and 3 cases of unconfirmed desmopressin dosing, were excluded from the 354 case report forms collected and fixed by the end of December 2021, and data up to 12 weeks after administration in 345 cases were defined as the safety analysis set. RESULTS: The mean age was 74.5 ± 9.9 years and 88.7% of the survey participants were aged ≥65 years. Desmopressin was started at a dose of 25 µg in 153 cases (44.3%). There were 102 adverse drug reactions (ADRs) reported in 71 cases, including 6 serious ADRs in 3 cases (0.9%). The most common ADR was hyponatremia occurring in 29 cases (8.4%). Eight of the hyponatremic cases were asymptomatic. Symptoms were resolved or slightly improved within 4 weeks of onset in 13 of 29 cases of hyponatremia. In addition, hyponatremia occurred in 11 of 217 cases (5.1%), with a serum sodium level before the administration of desmopressin of ≥140 mmol/L, and in 13 of 87 cases (14.9%), with a level of 135-139 mmol/L, and was not measured in 5 hyponatremia cases. Patient characteristics that showed significant differences in the occurrence of hyponatremia included body weight, body mass index, renal function, and pretreatment serum sodium level. Regular monitoring of serum sodium is necessary for early detection of hyponatremia. CONCLUSIONS: Hyponatremia was the most common ADR when desmopressin orally disintegrating tablets were used to treat nocturia due to nocturnal polyuria over a 12-week period.

Coexistence of type 2 diabetes mellitus, arginine vasopressin deficiency, and Marfan syndrome: A case report.

Diabetes mellitus (DM) and arginine vasopressin deficiency (AVP-D) are characterized by polyuria. Marfan syndrome is an autosomal dominant disorder caused by pathogenetic variants in FBN1. Here, we report a patient with type 2 diabetes mellitus, AVP-D, and Marfan syndrome. Although the coexistence of type 2 diabetes mellitus and AVP-D is rare, for those patients with type 2 diabetes mellitus, the existence of AVP-D should be considered when polyuria is not in accordance with the blood glucose levels, especially for those with a low urine specific gravity. Specific symptoms or signs help to identify Marfan syndrome early, and genetic testing of the FBN1 pathogenetic variant helps to make a definitive diagnosis.

Antidiuretic hormone deficiency secondary to inactive hydrocephalus: a case report.

BACKGROUND: Diabetes insipidus is a syndrome characterized by polyuria, which is almost always associated with polydipsia. The most frequent cause is central diabetes insipidus, which is the result of an inadequate secretion of the antidiuretic hormone, and diagnosis involves differentiating it from other causes of polyuria and polydipsia. CASE PRESENTATION: Here, we present a clinical case of a previously healthy 13-year-old Nepali boy, who, in December 2022, was found to have intense polydipsia accompanied by polyuria. He had bilateral lower limb weakness at the time of presentation. Biochemical evaluation demonstrated raised serum sodium (181 mEq/L), serum creatinine (78 µmol/L), and serum uric acid (560 µmol/L) with suppressed serum potassium (2.7 mEq/L), which was the major concern to the clinicians. Further laboratory workup revealed an increased serum osmolarity (393.6 mOsm/kg) with reduced urine osmolarity (222.7 mOsm/kg). On contrast magnetic resonance imaging of the brain, a thick-walled third ventricular cyst with bilateral foramen obstruction, thin membrane-like structure at top of aqueduct of Sylvius with gross obstructive hydrocephalus (inactive), and compressed and thinned pituitary gland with no bright spot was observed. The laboratory findings, radiological findings, and case presentation provided the provisional diagnosis of diabetes insipidus due to hydrocephalus and third ventricular cyst. CONCLUSIONS: Central diabetes insipidus due to hydrocephalus, though rare, can have serious complications including the predilection to develop a deficit of other pituitary hormones. Thus, even if hydrocephalus is dormant with normal intracranial pressure, it must be addressed during investigations of central diabetes insipidus.

The diagnostic performance of copeptin in clinical practice: A prospective study.

OBJECTIVE: Plasma copeptin is a relatively new biomarker for evaluation of arginine vasopressin (AVP) secretion. The aim of this study was to test the diagnostic performance of copeptin in patients with polyuria-polydipsia syndrome. DESIGN, PATIENTS AND MEASUREMENTS: This was a prospective study where 88 patients with polyuria-polydipsia syndrome were evaluated with a water deprivation test (WDT). Weight, urine osmolality, urine specific gravity, and plasma copeptin were collected at baseline, after 8 h, and at termination of the WDT when one of the following had been reached: (i) >3% weight reduction, (ii) urine specific gravity >1.017 or urine osmolality >600 mOsm/kg, or (iii) intolerable adverse symptoms. RESULTS: Of 88 patients (57 women), 21 (24%) were diagnosed with central diabetes insipidus (cDI), 5 (6%) with nephrogenic DI (nDI), and 62 (71%) with primary polydipsia (PP). Median (interquartile range) copeptin at baseline was 1.7 (1.4-2.5) pmol/L in cDI, 22 (18-65) pmol/L in nDI, and 2.7 (2-4) pmol/L in PP. After 8 h of WDT, the highest copeptin in patients with cDI was 4.0 pmol/L. In patients with PP: (i) 41 had urine osmolality <600 mOsm/kg, 7 (17%) of these had copeptin >4.0 pmol/L, (ii) 21 had urine osmolality ≥600 mOsm/kg, 14 (67%) of these had copeptin >4.0 pmol/L. CONCLUSIONS: Copeptin >4.0 pmol/L after an overnight WDT can be used to rule out cDI and copeptin ≥21 pmol/L at baseline to diagnose nDI. The diagnostic performance of copeptin in the context of the WDT is otherwise limited in the diagnostic work-up of patients with polyuria-polydipsia syndrome.

Urine concentration impairment in sickle cell anemia: genuine nephrogenic diabetes insipidus or osmotic diuresis?

The urine concentration impairment responsible for hyposthenuria in sickle cell nephropathy is currently thought to be a consequence of renal medulla lesions, which lead to nephrogenic diabetes insipidus. The objective of the present study was to investigate the mechanism of hyposthenuria in patients with sickle cell anemia. We performed an observational study of patients with homozygous SS sickle cell anemia and data available on the fasting plasma antidiuretic hormone (ADH) concentration. A total of 55 patients were analyzed. The fasting plasma ADH values ranged from 1.2 to 15.4 pg/mL, and 82% of the patients had elevated ADH values and low fasting urine osmolality (<505 mosmol/kgH2O). Plasma ADH was positively associated with plasma tonicity and natremia (P < 0.001). None of the patients experienced polyuria and fasting free water clearance was negative in all cases, thus, ruling out nephrogenic diabetes insipidus. The tertile groups did not differ with regard to fasting urine osmolality, plasma renin level, mGFR, or several hemolysis biomarkers. The negative fasting free water clearance in all cases and the strong association between 24-h osmolal clearance and 24-h diuresis favors the diagnosis of osmotic diuresis due to an impaired medullary gradient, rather than lesions to collecting tubule.NEW & NOTEWORTHY The urine concentration impairment in sickle cell anemia is an osmotic diuresis related to an impaired renal medullary gradient leading to an ADH plateau effect. The fasting plasma ADH was high in the context of a basic state of close-to-maximal urine concentration probably driven by short nephrons maintaining a cortex-outer medullary gradient (about 400 milliosmoles). The patients had a low daily osmoles intake without evidence of thirst dysregulation so no one experienced polyuria.